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WO2022227401A1 - 微电网群同期控制方法和系统 - Google Patents

微电网群同期控制方法和系统 Download PDF

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Publication number
WO2022227401A1
WO2022227401A1 PCT/CN2021/121412 CN2021121412W WO2022227401A1 WO 2022227401 A1 WO2022227401 A1 WO 2022227401A1 CN 2021121412 W CN2021121412 W CN 2021121412W WO 2022227401 A1 WO2022227401 A1 WO 2022227401A1
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WIPO (PCT)
Prior art keywords
voltage
microgrid
control
microgrids
value
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PCT/CN2021/121412
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English (en)
French (fr)
Inventor
张卫
郑德化
苟富豪
谢素娴
张军生
张迅
特沙格鲁•博图•格鲁姆
朱树众
陈永欢
Original Assignee
北京天诚同创电气有限公司
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Application filed by 北京天诚同创电气有限公司 filed Critical 北京天诚同创电气有限公司
Priority to AU2021443821A priority Critical patent/AU2021443821A1/en
Priority to US18/558,092 priority patent/US20240222973A1/en
Priority to EP21938864.2A priority patent/EP4329135A1/en
Publication of WO2022227401A1 publication Critical patent/WO2022227401A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • H02J3/44—Synchronising a generator for connection to a network or to another generator with means for ensuring correct phase sequence
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/08—Synchronising of networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • H02J3/42—Synchronising a generator for connection to a network or to another generator with automatic parallel connection when synchronisation is achieved
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
    • H02J13/00028—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment involving the use of Internet protocols
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
    • H02J2310/10—The network having a local or delimited stationary reach
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/70—Smart grids as climate change mitigation technology in the energy generation sector
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/12—Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation

Definitions

  • the present disclosure belongs to the field of microgrid group control, and in particular, relates to a microgrid group synchronization control method and system based on optimal state estimation and IEC 61850 communication mode.
  • microgrids With the development and maturity of larger-capacity microgrid systems, multiple microgrids have developed from a single grid connection point to multiple grid connection points. Multiple loads in the same industrial park need to build multiple microgrids.
  • the parallel operation of multiple microgrids can maximize energy utilization, improve system stability, and ensure power supply reliability.
  • the traditional grid-connected and closed synchronization technology is based on the parallel operation of multiple machines in the power system.
  • the quasi-synchronized parallel device installed at the synchronization point in the hub substation is mainly used to judge the voltage amplitude difference. , phase difference and frequency difference, and then calculate the advance time of parallel parallel to control the closing relay, so as to achieve the purpose of parallel operation.
  • the traditional synchronous closing control technology is mainly aimed at the large power grid system where the frequency of the power supply is basically not adjustable. It is not suitable for the microgrid with more flexible power supply and a large number of power electronic devices. There are also disadvantages such as time-consuming and complicated calculation.
  • the distributed power generation equipment is mainly connected through the synchronous generator form or the power electronic device (converter) interface.
  • the power supply of the synchronous generator type is similar to the traditional protection device with the function of checking the synchronization and reclosing.
  • the generator itself has the moment of inertia and damping, the voltage and frequency do not change abruptly during stable operation, so its grid connection can be realized by using the synchronization checking device, that is, the detection of the power supply When the amplitude, frequency and phase angle of the side voltage and the grid side voltage reach the allowable range of grid connection, it can be closed and connected to the grid; the distributed power supply and energy storage device with the power electronic device as the interface and the automatic quasi-synchronized parallel operation of the traditional power grid Similarly, the synchronous grid connection is mainly based on the phase-locking technology of the stable voltage source, and the voltage control method is used to realize the pre-synchronization control of the grid connection of the microgrid system. However, for the microgrid in the island state, the energy storage system, synchronous generator, a large number of power electronic devices and loads in the U/f control mode operate at the same time. It is more complex and requires higher timeliness.
  • the grid-connection technology adopted in the microgrid is mainly based on the improvement of the synchronous grid-connection operation of the traditional power system.
  • the “Mode Switching Method for Microgrid Switching from Island Mode to Grid-connected Mode” (Application No. 201110382606.2) was published, and the method adopted was to shut down all distributed power sources before the microgrid was connected to the grid to ensure that there would be no asynchronous grid connection. However, it will cause short-term power failure of the load and affect users; "A Method for Synchronous Grid Connection of Microgrid Based on Phase Approximation" (Application No.
  • 201610580848.5 is published, which is mainly based on the inverter controlled by the power electronic interface to control the grid-connected frequency, but the microgrid group it considers is not the same.
  • the grid only refers to the integration of large microgrids including multiple small microgrids into the power system, only one grid connection point is considered, and the situation of multiple microgrid groups connected to the grid is not studied.
  • the existing microgrid synchronous grid-connection technology research content mainly focuses on how to control and adjust the voltage amplitude, frequency and phase of the microgrid side stably and accurately, and update the synchronous closing judgment algorithm.
  • the premise of accurate calculation and control is to ensure the accuracy of the data used and the timeliness of system communication.
  • the method currently used is to improve the accuracy of the sensor or the quality of data transmission, and to improve the accuracy of the data through uninterrupted multiple acquisitions.
  • the simultaneous grid connection of multiple microgrid groups the existing technology only gradually connects the grids one by one in a predetermined order, which is low in efficiency and cannot guarantee system stability.
  • the present disclosure optimizes and innovates data processing algorithms and communication control for the simultaneous data collection of microgrid groups and the simultaneous grid connection of multiple microgrid groups (multiple grid connection points).
  • the voltage amplitude, frequency and phase angle of the upper and lower ports of the circuit breaker are used as the judgment basis, and according to the voltage estimation results at both ends of the synchronous control point, the distributed power supply (mainly the voltage and frequency support power supply) in the micro-grid adopts fast proportional integration to carry out Real-time power regulation. While shortening the synchronization time, the accurate judgment of the synchronization conditions is realized, so that the impact of closing on the microgrids at both ends is small, and the success rate of the synchronization is improved.
  • the voltage estimation of the present disclosure establishes a differential equation model and an optimal estimation model for synchronous control, and uses optimal state estimation to obtain the optimal value of the state quantity required for the same period, which greatly improves the accuracy of the synchronization, thereby reducing the synchronous contract.
  • the system impact of the brake is improved, and the transient and dynamic stability of the system at the same time is improved.
  • the present disclosure establishes a contemporaneous conditional boundary model for a single microgrid, and further establishes a contemporaneous conditional boundary model for multiple microgrid groups, which can accurately determine the sequence of the synchronization, stabilize the synchronization and improve the efficiency of the synchronization, and avoid the occurrence of concurrency in the microgrid group.
  • Distributed power generation cannot be regulated at the same time (insufficient reserve capacity) and destroy system stability.
  • a microgrid group synchronization control system may include a plurality of microgrids, the system includes a central controller, and the central controller is configured to: select from the plurality of microgrids The voltage measurement value of each receiving grid-connected point of a control instruction at the next moment; and sending a control instruction to at least one of the plurality of microgrids, so as to adjust the closing synchronization among the plurality of microgrids through phase-lock control.
  • the voltage measurement value may be transmitted in a time-driven manner per sampling period; and the transmission time interval of the control command may be increased from a minimum time interval to a heartbeat time interval.
  • the central controller may also be configured to: receive voltage measurements from each microgrid through the SV protocol in the IEC 61850 standard; send control instructions to the at least one microgrid through the GOOSE protocol in the IEC 61850 standard, and for Each frame of data transmitted through the SV/GOOSE protocol performs individual verification.
  • the central controller may also be configured to perform optimal state estimation on the voltage measurement values on both sides of the grid connection point, so that the error of the control command is minimized.
  • the central controller may also be configured to: cumulatively determine the measurement error obtained by cumulatively summing the differences to obey a Gaussian distribution.
  • the central controller may also be configured to perform real-time verification of each voltage measurement using the covariance of the voltage measurements of the previous voltage cycle.
  • the central controller may also be configured to: obtain discrete direct-axis components and quadrature-axis components of the voltage value by performing Park transformation on the voltage measurement value into a rotating rectangular coordinate system and performing orthogonal transformation, and use it as an input value for proportional-integral adjustment. .
  • the central controller may also be configured to: determine an adjustment sequence of the plurality of microgrids according to the capacity of each of the plurality of microgrids, and determine that adjustments need to be made based on a margin in a current operating voltage parameter state The contemporaneous regulation boundary of the microgrid.
  • the central controller may also be configured to select a smaller capacity microgrid as the target to be regulated prior to the synchronization, and to change the regulation target when the voltage regulation parameter exceeds the microgrid's synchronous regulation boundary.
  • the microgrid group may include a plurality of microgrids, the method comprising: receiving a voltage measurement of a grid connection point from each of the plurality of microgrids performing proportional integral adjustment on the voltage measurement value to obtain the difference between the voltage measurement value at the previous moment and the control value at the current moment, so as to be used to estimate the control command at the next moment; At least one microgrid in the power grid sends a control command to adjust the closing synchronization among the plurality of microgrids through phase lock control.
  • the voltage measurement value may be transmitted in a time-driven manner per sampling period; and the transmission time interval of the control command may be increased from a minimum time interval to a heartbeat time interval.
  • the method may further include: receiving the voltage measurement value from each microgrid through the SV protocol in the IEC 61850 standard, and sending control instructions to at least one microgrid through the GOOSE protocol in the IEC 61850 standard; Each frame of data transmitted by the protocol performs a separate check.
  • the method may further include: performing optimal state estimation on the voltage measurement values on both sides of the grid connection point, so that the error of the control command is minimized.
  • the method may further include: accumulatively determining that the measurement error obtained by accumulating and summing the difference conforms to a Gaussian distribution.
  • the method may further include performing a real-time check on each voltage measurement using the covariance of the voltage measurements of the previous voltage cycle.
  • the method may further include: obtaining discrete direct-axis components and quadrature-axis components of the voltage value by performing Park transformation on the voltage measurement value into a rotating rectangular coordinate system and performing orthogonal transformation, which are used as input values for proportional-integral adjustment.
  • the method may further include: selecting an adjustment sequence of the plurality of microgrids according to the capacity of each of the plurality of microgrids, and determining the adjustment sequence of the microgrids to be adjusted based on the margin in the current operating voltage parameter state. Concurrent adjustment boundaries.
  • the method may further include selecting a microgrid with a smaller capacity as the target to be regulated earlier in the same period, and changing the regulation target when the voltage regulation parameter exceeds the synchronous regulation boundary of the microgrid.
  • a computer-readable storage medium storing a computer program
  • the above-mentioned microgrid group synchronization control method is implemented.
  • a computer device includes: a processor; and a memory storing a computer program, when the computer program is executed by the processor, the above-mentioned microgrid group synchronization control method is implemented.
  • Fig. 1 is the single-phase voltage curve diagram of both ends of the circuit breaker without applying synchronous control
  • Fig. 2 is the single-phase voltage curve diagram of both ends of the synchronously controlled circuit breaker without voltage state estimation
  • Figure 3 is a topology diagram of two microgrids based on the synchronous control mode of on-site direct mining and direct control;
  • Figure 4 is a topology diagram of the synchronous control mode using the IEC 61850 protocol
  • Fig. 5 is the topology diagram of the synchronous control of multiple microgrids under the traditional mode
  • FIG. 6 is a topology diagram of a synchronous control system according to the present disclosure.
  • FIG. 7 is a block diagram of a synchronous control system according to the present disclosure.
  • FIG. 8 is a block diagram of the principle of a three-phase synchronous phase-locked loop according to the present disclosure.
  • V d voltage amplitude
  • FIG. 10 is a graph of angular frequency ( ⁇ ) output of a phase locked loop according to the present disclosure
  • FIG. 11 is a graph of a voltage phase angle ( ⁇ ) output by a phase locked loop according to the present disclosure
  • FIG. 12 is a block diagram of the principles of a PI regulator according to the present disclosure.
  • FIG. 13 is a block diagram of voltage amplitude control employing a PI regulator according to the present disclosure
  • phase angle control employing a PI regulator according to the present disclosure
  • FIG. 15 is a block diagram of angular frequency control employing a PI regulator according to the present disclosure
  • 16 is a graph of voltage dynamics for active power regulation in accordance with the present disclosure.
  • 17 is a graph of voltage as a function of active and reactive power in accordance with the present disclosure.
  • 19 is a graph of voltage as a function of active and reactive power in accordance with the present disclosure.
  • FIG. 20 is an architecture diagram of a synchronous control system according to the present disclosure using IEC 61850 communication;
  • FIG. 21 is a schematic diagram of a GOOSE message sending process according to the present disclosure.
  • FIG. 22 is a flowchart of a microgrid cluster synchronization control method according to the present disclosure.
  • Microgrid Multiple distributed energy sources and loads are interconnected with clear electrical boundaries, and are a single controllable system that can operate in either grid-connected or islanded mode (refer to IEC 60050-617:2017). Description "Group of interconnected loads and distributed energy resources with defined electrical boundaries forming a local electric power system at distribution voltage levels, that acts as a single controllable entity and is able to operate in either grid-connected or island mode").
  • Island A part of an electrical system that is disconnected from the rest of the system but still has electricity.
  • Transient disturbance Instantaneous severe voltage and current changes caused by switching on and off of power generation equipment, load start and stop, unplanned islanding or faults in the microgrid, characterized by large fluctuations and obvious phase changes, continuous The time is 0-50ms (refer to the description in IEC TS 62898-3-1:2020 “Sudden and severe voltage and current changes in a microgrid caused by switching of generation or load, unintentional islanding or faults, characterized by large magnitude and phase changes and continuing for a period of 0ms to 50ms”).
  • Dynamic disturbance a series of changes in microgrid voltage and current caused by high penetration ratio of renewable energy and intermittent, non-linear loads, planned islanding of microgrids, and renewable energy output power fluctuations and grid-side faults , the duration is 50ms ⁇ 2s (refer to the description in IEC TS 62898-3-1:2020 "Series of voltage and current changes in a microgrid caused by output of renewable energy sources reaching a sufficiently high proportion, non-linear loads, intentional islanding,intermittency and output power fluctuation of renewable energy resources and grid side faults, which continue for a period of 50ms to 2s”).
  • SV(Sampled Value) Sampled value, also known as SMV(Sampled Measured Value).
  • GOOSE Generic Object Oriented Substation Events.
  • Optimal state estimation Under the condition of a certain estimation criterion, according to a certain statistical significance, the estimated state is optimized.
  • Voltage amplitude The maximum absolute value of the instantaneous alternating current in one cycle, which is also half the distance from the peak to the trough in a voltage sine wave.
  • Frequency of voltage The number of times the voltage vector completes periodic changes per unit time.
  • Voltage phase angle also known as phase angle, refers to a value that determines the state of the voltage vector at any time (or position) when it changes sine or cosine with time (or spatial position).
  • the existing synchronization technology detects the voltage at both ends of the circuit breaker port that needs to be closed synchronously based on the measurement and control equipment set up on site, and judges the synchronization based on the voltage amplitude, frequency and phase angle, but the synchronization time is relatively long. In addition, it is difficult to strictly judge the synchronization conditions, which has a great impact on the power grid at both ends of the breaker, and in severe cases leads to failure of the synchronization.
  • Figure 1 is a graph of single-phase voltage across a circuit breaker without synchronisation control applied.
  • Figure 2 is a graph of single-phase voltage across a synchronously controlled circuit breaker without voltage state estimation.
  • ⁇ ref represents the maximum value of the phase angle difference between the voltages on both sides of the fracture allowed by the synchronization conditions.
  • the system does not actually meet the synchronization conditions. After the controller sends the closing command, there will be a large inrush current and voltage dynamic instability between the microgrids. In severe cases, the synchronization will fail and affect the safe and stable operation of the system. .
  • the existing grid-connected synchronization technology cannot meet the requirements of precise synchronization control of microgrids or microgrid groups.
  • the microgrid power generation unit and the energy storage system are generally connected through power electronic equipment, and the power supply has a weak shock resistance, and is overloaded with twice the rated current at most.
  • the traditional synchronization technology is easy to cause the system current to be too large and protect in advance;
  • most of the microgrid system has weak inertia, weak transient stability and dynamic stability, and the transient process and dynamic process of the system in the same period are likely to cause synchronization failure.
  • the capacity of the microgrid island operation system is small and the reserve capacity is insufficient, so that the small disturbance of the system will also cause the microgrid dynamic response time to be long and the voltage dynamic oscillation amplitude to be large.
  • the existing on-site synchronous controller usually receives the upper-level control instructions to perform synchronous closing, but the synchronous control for a microgrid group composed of multiple microgrids involves multiple synchronous control points, and the synchronous control points are the same as the synchronous control.
  • the distance of the device is relatively long, and the direct acquisition of voltage data and the direct control of switch opening and closing cannot meet not only the long-distance requirements, but also the time requirements.
  • the existing technology cannot realize automatic synchronization and automatically determine the optimal sequence of synchronization. Therefore, it is necessary to calculate the operating states of all systems in a synchronization control system to realize fast communication and solve the problem of long-distance information transmission.
  • the microgrid group involves multiple synchronization control points, and the synchronization control point is far away from the synchronization controller.
  • the method of directly collecting voltage data and directly controlling the switching of switches cannot meet the long-distance requirements.
  • the present disclosure adopts the SV and GOOSE communication methods of IEC 61850 to collect real-time values of switch states and voltages and perform real-time remote control of synchronous circuit breakers. This communication control method can solve the problems of long-distance communication and multiple synchronous control points.
  • the synchronous control system of the present disclosure collects the state information of the synchronous control point and the real-time data of the voltage on both sides of the breaker at the synchronous control point. Since the synchronization process requires strict synchronization, the B code of the time synchronization server is used for time synchronization. For the synchronization between multiple microgrids or the synchronization control point is far from the synchronization core equipment, optical fiber communication is used to ensure the real-time and undistorted sampling signal, and the IEC 61850 communication method is used for real-time transmission of voltage data and real-time switching signal. feedback and remote control.
  • FIG. 3 is a topology diagram of two microgrids based on the synchronous control mode of direct mining and direct control on site.
  • a typical microgrid 1 in an industrial park may include three distributed power sources DER1 , DER2 and DER3 and a load Load, but is not limited thereto.
  • the distributed power source DER1 operating in U/f mode is used as the main support power supply in the microgrid system and can ensure the stability of the island operation of the microgrid 1.
  • the microgrid 2 may include three distributed power sources DER1 , DER2 and DER3 that are the same as or similar to the microgrid 1 and a load Load.
  • the distributed power source DER1 operating in U/f mode is used as the main support power supply in the microgrid system and can ensure the stability of the island operation of the microgrid 1.
  • micro power source DER2 and distributed power source DER3 are used as PQ power sources in the microgrid system, which can be fluctuating and intermittent power generation sources, such as wind power generation and photovoltaic power generation; the load is another 10kV load in the industrial park.
  • the synchronous control point can be the circuit breaker between the two microgrids when parallel operation or decoupling operation is required.
  • microgrid 1 may encounter a situation where the power generation of the distributed power source exceeds the load power and needs to be limited, and the microgrid 2 may have a situation where the power generation of the distributed power source is insufficient to support the industrial load. happensing. Therefore, it is necessary to operate two microgrids in parallel to improve energy utilization and ensure load power consumption.
  • a line in microgrid 1 or microgrid 2 fails, it is necessary to delineate the synchronous control points between microgrids to maximize the reliability and redundancy of system power supply and minimize economic losses. .
  • the tie lines of multiple microgrids operating in parallel are generally resistive. Therefore, the synchronization between microgrid 1 and microgrid 2 is the synchronization between the bus voltages of the two microgrids. It is assumed that the three-phase voltage on the bus of the microgrid 1 is V abc , and the three-phase voltage on the bus of the microgrid 2 is V′ abc .
  • the phase-locking calculation of the two busbar voltages is performed through the phase-locked loop, and the voltage amplitude, voltage phase angle and frequency on the two busbars can be obtained.
  • the three elements of the bus voltage of the microgrid 1 are V m , ⁇ and ⁇ , where V m is the bus voltage amplitude of the micro grid 1, ⁇ is the bus voltage phase angle of the micro grid 1, and ⁇ is the bus voltage angular frequency of the micro grid 1.
  • the three elements of the bus voltage of the microgrid 2 are V′ m , ⁇ ′ and ⁇ ′, where V′ m is the bus voltage amplitude of the micro grid 2, ⁇ ′ is the phase angle of the bus voltage of the micro grid 2, and ⁇ ′ is the micro grid 2 bus voltage.
  • the angular frequency of the bus voltage meets the conditions for synchronous closing as follows:
  • V ref represents the maximum value of the voltage difference between the two buses allowed by the synchronous conditions
  • ⁇ ref represents the maximum value of the phase angle difference between the two buses allowed by the synchronous conditions
  • ⁇ ref represents the maximum value of the two buses allowed by the synchronous conditions.
  • the synchronous mode of direct acquisition and direct control of the acquisition equipment (which can be a voltage sensor such as a voltage transformer or a voltage divider) and the control equipment (eg, the controller) set up on site directly connects the two microgrids through the secondary electrical line.
  • the voltage parameters of the bus are collected, and the sampled values are directly sent to the synchronous controller.
  • the synchronous controller uses the secondary electric wire to control the relay on and off to realize the synchronous closing at the synchronous control point.
  • one synchronization device can only correspond to one synchronization control point, and when the two microgrids are far apart, the voltage acquisition data signal will weaken and the control signal will be distorted.
  • FIG. 4 is a topology diagram of the synchronous control method using the IEC 61850 protocol.
  • the voltage between the two microgrid buses is acquired by collecting equipment in real-time data, and the collected voltage measurement value is filtered and performed according to the IEC 61850 communication method. framing.
  • the synchronous controller receives the voltage measurement value of the grid connection point from the acquisition device of each microgrid through IEC 61850 communication (the voltage measurement value is sent in a time-driven manner of each sampling period); based on the voltage measurement value, it is estimated for each The control command at the next moment of the microgrid; and send the control command to the microgrid that needs to be adjusted through IEC 61850 communication (the sending time interval of the control command is increased from the minimum time interval to the heartbeat time interval), so as to adjust through phase-locked control The closing synchronization between the plurality of microgrids.
  • FIG. 5 is a topology diagram of synchronous control of multiple microgrids in conventional mode.
  • 6 is a topology diagram of a synchronous control system according to the present disclosure.
  • synchronization central controller in view of the synchronization problem in the case of islanded operation of multiple microgrids, according to the embodiment of the present disclosure, only one synchronization central controller is set in the synchronization control system of the microgrid group, which can improve the economical efficiency and can operate in an optimal manner.
  • the synchronous control system of multiple microgrids also adopts IEC 61850 communication and long-distance optical fiber transmission to ensure real-time communication and no signal distortion.
  • the real-time collection data of the voltage measurement value and the current measurement value are directly collected by the on-site data collection device, which ensures the real-time data.
  • the directly collected voltage and current analog data cannot be transmitted over long distances, so the local data acquisition equipment needs to be able to convert the analog to digital for IEC 61850 SV communication, and the digital is framed according to the IEC 61850 communication protocol.
  • the on-site acquisition device sends the collected information to the synchronous central controller through a communication network (eg, optical fiber or wireless communication) to ensure that the signals sent to the synchronous central controller are real-time and not distorted.
  • the local data acquisition equipment can collect the switching status of the synchronous circuit breaker and directly control the circuit breaker.
  • the circuit breaker status collection can be sent to the synchronous central controller through the communication network through the GOOSE communication method of IEC 61850.
  • the synchronous central controller sends the synchronous control signal to the local controller through the GOOSE communication method of IEC 61850 to directly control the circuit breaker.
  • FIG. 7 is a block diagram of a synchronous control system according to the present disclosure.
  • the central controller undertakes the decoding function of the input information and the subsequent IEC 61850 encoding function in the same period.
  • the central controller performs the optimal estimation of the sent status information, and obtains the optimal value of the actual operation to improve the controllability of the system. sex.
  • the optimal estimation obtains the voltage amplitude, phase and frequency of the measurement point; phase locking is performed according to the real-time voltage estimation value; the synchronization comparison algorithm is performed according to the voltage amplitude, phase and frequency obtained by calculation, and PI adjustment is used to adjust the voltage amplitude and phase respectively. and frequency for quick adjustment to achieve synchronous closing operation.
  • FIG. 8 is a block diagram of the principle of a three-phase synchronous phase-locked loop according to the present disclosure.
  • the power grid is in a three-phase balanced state during normal operation, and a three-phase genlock technology is adopted here.
  • Park transformation on the voltage measurement value into a rotating rectangular coordinate system and performing orthogonal transformation, the discrete direct-axis and quadrature-axis components of the voltage value are obtained, which are used as input values for proportional-integral adjustment.
  • the input of the phase-locked loop is the real-time sampling value of the three-phase voltage.
  • the discrete direct-axis and quadrature-axis components of the voltage value are obtained, which are used as the input of the proportional-integral adjustment. That is, the three-phase voltage vector of the measured value V abc is transformed from the natural coordinate system to the dq synchronous rotating coordinate system using Park transformation, wherein the d-axis component contains voltage amplitude information, and the q-axis component has voltage phase information and frequency information.
  • V d represents the voltage amplitude
  • the actual voltage q-axis component is taken as 0 as a reference and the deviation from the 0 value is input into the PI regulator module, and the adjustment result is superimposed with the original frequency ⁇ 0 of the power grid
  • the angular frequency ⁇ * is obtained, and the voltage phase angle is obtained by integrating ⁇ *.
  • the phase-locking method can achieve high-precision and fast phase-locking in the normal power grid environment.
  • V d voltage magnitude
  • ⁇ angular frequency
  • ⁇ voltage phase angle
  • the output V d , ⁇ * and ⁇ are the above three elements Vm, ⁇ and ⁇ in the same period.
  • the algorithm and model of the three-phase synchronous phase-locked loop are tested in a typical microgrid model, and the three-phase voltage of abc on the microgrid bus is sampled. required state.
  • the phase-locking results are shown in Figures 9 to 11, which can be gradually adjusted in a short time until each state is stable.
  • the response time and accuracy of the phase-locking are controlled by adjusting the parameters of the PI regulator.
  • the synchronous central controller performs the phase-locking process of the phase-locked loop and uses fast proportional-integral regulation (PI regulation) for the voltage amplitude, frequency and phase regulation processes of the distributed power supply.
  • the PI regulator is a linear controller, which obtains the control difference according to the given value and the actual output value, and uses the proportional integral of the difference to obtain the control amount through a linear combination to control the controlled object.
  • the proportional parameter K p controls the response speed of the deviation adjustment.
  • the response speed of the system will increase with the increase of the value, but when it increases to a certain extent, the system will become unstable.
  • the main function of integral adjustment is to eliminate the steady-state error of the system and improve the error-free degree.
  • the larger the value of integral parameter K i the weaker the integral effect, and vice versa.
  • the smaller the overshoot of the closed-loop system the slower the response of the system.
  • FIG. 12 is a block diagram of the principle of a PI regulator according to the present disclosure.
  • the data acquisition equipment for collecting the voltage and current of the synchronous control point and the real-time state of the switch collects the synchronous control point and the necessary state signals of the microgrid system, and the state can also be calculated according to the system model.
  • 13 is a block diagram of voltage amplitude control using a PI regulator in accordance with the present disclosure.
  • 14 is a block diagram of phase angle control employing a PI regulator in accordance with the present disclosure.
  • 15 is a block diagram of angular frequency control employing a PI regulator in accordance with the present disclosure.
  • the PI regulator in the controller performs proportional and integral adjustment on the voltage measurement value to obtain the difference between the voltage measurement value at the previous moment and the control value at the current moment, which is used to estimate the control command at the next moment.
  • the calculation mathematical model of the synchronous voltage amplitude is established as follows:
  • Vref -[(Vn -1- Vn ) ⁇ Kvp +(Vn -1- Vn ) ⁇ Kvi /s] Vn (5)
  • Vref can be considered as a constant value in linear system or local linear calculation.
  • K vp represents the proportional coefficient of the voltage amplitude control
  • K vi represents the integral coefficient of the voltage amplitude control
  • V n represents the output value calculated by the controller
  • V n-1 represents the voltage amplitude state value feedback.
  • the integral term actually represents the accumulation of errors in the calculation process.
  • the present disclosure approximately considers that the state quantity obeys the Gaussian distribution, and the error accumulation can also be considered to obey the Gaussian distribution, because the results of actual calculation and theoretical simulation can also show that the error is similar to Gaussian white noise. Therefore, the above control system model can be expressed as follows:
  • V n V(n)
  • V n-1 V(n-1)
  • V(n) A ⁇ V(n-1)+B ⁇ u(n)+ ⁇ (n) (10)
  • the present disclosure applies the optimal state estimation to the synchronous control between medium-voltage microgrid groups, performs optimal state estimation on the voltage measurements on both sides of the synchronous grid connection point, and obtains a relatively accurate voltage value for use in control instructions, so that the control The error of the instruction is minimal.
  • the voltage amplitude, phase and frequency required for the synchronization may not meet the synchronous closing conditions due to measurement errors, calculation errors or the influence of communication quality, resulting in a large generation of voltage on the synchronous closing contact bus.
  • the inrush current will lead to the failure of synchronous closing.
  • the present disclosure performs optimal state estimation on the voltage data at both ends of the synchronous control point according to the mathematical model of synchronous control, so as to ensure the minimum error of the obtained state information at the next moment. to represent the covariance. Since the input data required by the model is calculated by sampling points, the model is a discrete mathematical model.
  • the discrete mathematical model of the optimal state estimation is obtained by discretizing the mathematical model of the microgrid voltage as follows:
  • y(t) represents the state value at the current moment, which can represent the voltage amplitude, phase angle or frequency at the current moment.
  • y(t-1) represents the state value at the last moment, where it can represent the voltage amplitude, phase angle or frequency obtained at the last sampling moment.
  • u(t) represents the control action of the system, which can be used to characterize the control action of the same period.
  • w(t) represents the error in the calculation and other processes.
  • the error obeys the Gaussian distribution, the covariance of the error is ⁇ 0, and the mean value is ⁇ 0.
  • a and B represent the control system parameters, respectively. According to the present disclosure, each voltage measurement can also be checked in real time using the covariance of the voltage measurements of the previous voltage cycle.
  • the voltage-related data at both ends of the synchronous control point can also be measured by sensors.
  • the discrete measurement system can be expressed as follows:
  • x(t) represents the measured value of the voltage amplitude, phase angle or frequency at the current sampling time
  • v(t) represents the error of the measurement system. It can also be considered that the measurement error obeys the Gaussian distribution, and the covariance of the measurement error is is ⁇ 1, and the mean is ⁇ 1.
  • the next state of the system is predicted using a mathematical model of the calculation process. If the current time is t, the state of the current time can be predicted based on the state of the previous time.
  • the expression is as follows:
  • t-1> represents the result predicted according to the previous state
  • t-1> represents the optimal value at the previous moment
  • u ⁇ t> represents the control of the control system effect. Since y ⁇ t-1
  • t-1> represents the covariance of the estimated value y ⁇ t
  • t-1> represents the y ⁇ t-1 at the previous time
  • K G represents the gain coefficient, which reflects the reliability between the measured value and the calculated value.
  • the calculation of the gain coefficient is as follows:
  • E represents the identity matrix
  • Another aspect of the present disclosure also proposes to establish a contemporaneous conditional boundary model of a single microgrid, and establish contemporaneous conditional boundary models of multiple microgrids accordingly, so as to realize whether the synchronously regulated distributed power supply has a reserve capacity and It is judged whether the power flow distribution after the same period exceeds the limit.
  • the microgrid belongs to the low-voltage system, and its voltage value and frequency have a coupling relationship with the active and reactive components, so that the system cannot be completely decoupled.
  • voltage may be related to the active component and frequency to the reactive component.
  • the present disclosure establishes functional relationships between voltage value and frequency and active and reactive components, respectively:
  • the droop factor represents the gradient of the bus voltage value and frequency with power changes.
  • the relational function formula considering the sag coefficient is as follows:
  • the system capacity boundary conditions are as follows:
  • U 1 represents the bus voltage value of the microgrid 1
  • F1 represents the bus voltage frequency of the microgrid 1
  • P1 represents the voltage frequency of the microgrid 1
  • the supporting power supply can withstand the active power
  • Q1 represents the voltage frequency of the microgrid 1 .
  • the reactive power that the support power supply can withstand S 1 represents the apparent power of the voltage and frequency support power supply of the microgrid 1, and its maximum value cannot exceed the maximum capacity of the distributed power supply. It must be noted that the following formula does not hold:
  • FIG. 16 is a graph of voltage dynamics for active power regulation in accordance with the present disclosure.
  • the frequency and voltage characteristics of the microgrid operating in the islands on both sides of the control point at the same time are shown.
  • the voltage value in the low-voltage system and the microgrid system is linearly related to the active component, and the frequency and the reactive component are linearly related.
  • the curve 1 represents the relationship between the output power of the microgrid 1 and the voltage value
  • the curve 2 represents the relationship between the output power and the voltage value of the microgrid 2 .
  • the microgrid 1 operates at point C, and the corresponding system frequency is U1; the microgrid 2 operates at point A , and the corresponding system frequency is U2.
  • the capacity corresponding to microgrid 1 is relatively large.
  • the microgrid with smaller capacity can be used as the adjusted item of synchronous control, and the microgrid with larger capacity can be used as the reference item for synchronous control. Therefore, it is necessary to adjust the voltage value of the microgrid 2 to U 1 .
  • the operation curve of the microgrid 2 is transformed from the curve 2 to the curve 3 from the point A to the point B.
  • the power does not change at this time, the transient impulse power will appear when the two microgrid systems are connected in parallel, resulting in an instantaneous power increase.
  • the power of the microgrid 2 may exceed the maximum value at the moment of closing, resulting in failure of the same period. Therefore, there is a greater risk of failure to perform synchronous operation at this voltage point, and this point can be used as a critical point.
  • the present disclosure selects the synchronous reference value according to the capacity of each microgrid in the microgrid cluster system, obtains the adjustment margin of each microgrid under the current operating state according to the voltage value and the functional relationship between frequency and power, and determines the synchronous boundary conditions for determining Synchronous frequency point and voltage value point and phase point.
  • voltage is related to both active and reactive power
  • frequency is also related to active and reactive power. Based on experience, the following corrections can be made:
  • m 1 represents the droop coefficient of the voltage value relative to the active component
  • a 1 , a 2 , and a 3 represent the fitting relationship coefficient between the voltage value and the reactive component
  • n 1 represents the droop coefficient of the frequency relative to the reactive component
  • b 1 , b 2 , and b 3 represent the fitting relationship coefficient between the frequency and the active component.
  • 17 is a graph of voltage as a function of active and reactive power in accordance with the present disclosure.
  • 18 is a graph of voltage as a function of active and reactive power in accordance with the present disclosure.
  • 19 is a graph of voltage as a function of active and reactive power in accordance with the present disclosure.
  • the optimal synchronous power area for the synchronous control of the system is near the intersection area.
  • the small-capacity microgrid issues synchronous control commands to make it follow the larger-capacity microgrid.
  • the microgrid with large system capacity operates near the power limit (if the energy storage is used as the main support power source, there are two situations of absorbing and emitting the maximum power point), due to the instantaneous impact of the same period, the large-capacity microgrid may cause overcurrent. As a result, the synchronization fails, so it is impossible to directly control the way that the synchronization of the small-capacity microgrid follows the large-capacity microgrid.
  • the synchronous controller is required to reasonably adjust the distributed power supply or adjustable load of the large-capacity microgrid system.
  • the operating point of the large-capacity microgrid is adjusted back to the intersection area to ensure the capacity margin of the two systems at the instant of the same period to ensure the stability of the same period. Therefore, the adjustment sequence of the multiple microgrids can be selected according to the capacity of each of the multiple microgrids, and the synchronous adjustment boundary of the microgrid to be adjusted is determined based on the margin in the current operating voltage parameter state. For example, a microgrid with a smaller capacity may be selected as the target to be regulated earlier in the same period, and the regulation target may be changed when the voltage regulation parameter exceeds the microgrid's synchronous regulation boundary.
  • FIG. 20 is an architectural diagram of a synchronous control system according to the present disclosure using IEC 61850 communication.
  • FIG. 21 is a schematic diagram of a GOOSE message sending process according to the present disclosure.
  • the control display interface in the system can be provided by the SCADA system and communicate with the central controller.
  • SV Sampleled Value
  • GOOSE Generic Object Oriented Substation Events
  • the IEC 61850 communication method connects the central controller for the synchronization of the microgrid group with the measurement unit MU (local device) of each microgrid through the SV network and with the controller (local device) of each microgrid through the GOOSE network connect.
  • the present disclosure adopts the SV/GOOSE message format in the IEC 61850 communication mode for data interaction to form a ring network architecture for Ethernet control and communication of high-speed communication.
  • the use of a ring network instead of a point-to-point communication architecture between the control center and the microgrid equipment takes into account the complexity of system wiring and the real-time nature of data interaction between various microgrids.
  • the SV/GOOSE message under the IEC 61850 standard adopts a publisher/subscriber communication structure.
  • the SV/GOOSE message is a time-driven communication method, that is, the sampling value is sent every predetermined time.
  • the publisher the voltage and current sensors in the microgrid on-site device and the switching value, status information, etc.
  • the SV message is a time-driven communication method, and the sampling value can be sent at a predetermined time interval, and the predetermined time interval can be the same as the sampling time interval. For example, voltage measurements of the microgrid are sent in a time-driven manner per sampling period.
  • T0 is the heartbeat time
  • T1 can be set to 2ms
  • T2 can be set to 2 times T1
  • T3 can be set to 2 times T2.
  • FIG. 22 is a flowchart of a microgrid cluster synchronization control method according to the present disclosure.
  • the process receives a voltage measurement value of the grid connection point from each microgrid of the plurality of microgrids, wherein the voltage measurement value is transmitted by the time driving of each sampling period; at operation 222 , the process estimates a control command for the next moment in time for each microgrid based on the voltage measurements; and at operation 223, the process sends a control command to at least one microgrid of the plurality of microgrids for phase-locked control
  • the closing synchronization among the plurality of microgrids is adjusted, wherein the sending time interval of the control command is increased from a minimum time interval to a heartbeat time interval.
  • the present disclosure also provides a computer-readable storage medium storing a computer program.
  • the computer-readable storage medium stores a computer program that, when executed by the processor, causes the processor to execute the microgrid cluster synchronization control method according to the present disclosure.
  • the computer-readable recording medium is any data storage device that can store data read by a computer system. Examples of the computer-readable recording medium include read-only memory, random-access memory, optical disks, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet via wired or wireless transmission paths).
  • the present disclosure also provides a computer device.
  • the computer device includes a processor and memory. Memory is used to store computer programs.
  • the computer program is executed by the processor so that the processor executes the computer program of the microgrid cluster synchronization control method according to the present disclosure.
  • the SV and GOOSE communication methods of IEC 61850 are used to sample the voltage in real time and send control instructions, and a high-precision phase-locked loop is used to calculate the amplitude, frequency and phase of the voltage.
  • a microgrid group with multiple synchronous control points The accuracy and validity of the collected data and the effectiveness of the control can still be guaranteed.
  • the optimal estimation model is used to estimate the optimal value of the state quantity of the synchronous control, so as to ensure that the synchronous control command is closest to the actual operating state of the system, which greatly improves the synchronization of the microgrid group. Closing success rate.
  • the boundary models of the synchronous conditions of multiple microgrids are established to accurately determine the synchronous boundary conditions of each microgrid in the microgrid group, so as to achieve system stability and rapid synchronous closing, and improve synchronous efficiency.

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Abstract

本公开提供一种微电网群同期控制方法和系统，所述微电网群同期控制系统包括中央控制器，所述中央控制器被配置为：从多个微电网中的每个接收并网点的电压测量值；对所述电压测量值进行比例积分调节，并得到上一时刻的电压测量值与当前时刻的控制值之间的差分，以估计针对每个微电网的下一时刻的控制指令；以及向所述多个微电网中的至少一个微电网发送控制指令，以通过锁相控制调节所述多个微电网之间的合闸同期。能够保证所采集数据的准确性和实效性以及控制的有效性，极大限度提升了微电网群同期合闸成功率。

Description

微电网群同期控制方法和系统 技术领域
本公开属于微电网群控制领域，具体地讲，涉及一种基于最优状态估计和IEC 61850通信方式的微电网群同期控制方法和系统。
背景技术
随着更大容量的微电网系统的发展和成熟，多个微电网之间由单个并网点发展到多个并网点。同一工业园区内的多个负荷需要建设多个微电网，多个微电网之间的并联运行可最大化利用能源，提高系统稳定性，保证供电可靠性。传统的并网合闸同期技术是基于电力系统多机并联运行的技术，在解决合闸同期的问题时，主要利用处于枢纽变电站中安装在同期并列点的准同期并列装置来判断电压幅值差、相位差和频率差，再计算同期并列的越前时间来控制合闸继电器，从而达到并列操作的目的。但传统的同期合闸控制技术主要针对的是电源频率基本不可调的大电网系统，对于电源更加灵活且包含大量电力电子装置的微电网并不适用，并且在数据处理、信息通信、控制算法等方面还存在耗时长、计算复杂等缺点。
在交流微电网中，分布式发电设备主要通过同步发电机形式或电力电子装置(变流器)接口接入。同步发电机类型的电源与传统保护装置检同期重合闸功能类似，由于发电机自身具备转动惯量和阻尼使得稳定运行中电压频率不发生突变，因此其并网可利用检同期装置实现，即检测电源侧电压与电网侧电压的幅值、频率、相位角达到并网允许的范围则可合闸并网；以电力电子装置为接口的分布式电源和储能装置与传统电网的自动准同期并列操作类似，同期并网主要是基于稳定电压源的锁相技术，采用电压控制方式实现微电网系统并网的预同步控制。但对于孤岛状态下的微电网，U/f控制模式下的储能系统、同步发电机、大量电力电子装置以及负荷同时运行，同期并网的条件更难以满足，同时数据处理和信息传递也更为复杂，时效性要求更高。
目前，微电网中采用的并网技术主要是基于传统电力系统同期并网操作的改进。公开《用于微网的从孤岛模式切换到并网模式的模式切换方法》(申 请号201110382606.2)，采用的方法是在微电网并网前将所有分布式电源停机，确保不出现非同期并网，但会造成负荷短时断电影响用户；公开《一种基于相位逐步逼近的微电网同期并网方法》(申请号201510549244.X)，将微电网系统与电网系统间的相位差作为同期判别依据，并采用设定步长调节的方法对微电网侧的电压相位进行调节，但没有对电压幅值的同期调节进行考虑；公开《一种微电网平滑同期并网控制方法》(申请号201410057243.9)公开的微电网并网方法中，公开了一种单相/三相自适应的同期并网检测和调节方法，通过自动幅值补偿、自动相角补偿的方式进行同期调节，但此同期调节所需时间较长；公开《一种微电网群同期合闸并网的控制方法》(申请号201610580848.5)，主要基于电力电子接口控制的逆变器控制并网频率，但其考虑的微电网群并网仅指包含多个小微电网的大型微电网并入电力系统，仅考虑一个并网点，并未研究多个微电网群并网的情况。
大多数现有的微电网同期并网技术的研究内容主要集中在如何对微电网侧的电压幅值、频率和相位进行稳定精确的控制调节，以及对同期合闸判定算法的更新。但计算和控制精准的前提是保证所使用数据的准确性，同时保证系统通信的时效性。对此，目前使用的方式在于提高传感器精度或数据传输质量，通过不间断多次采集来提高数据准确性。而对于多个微电网群的同期并网，现有技术也仅按既定顺序逐个系统逐步并网，效率较低同时也不能够保证系统稳定性。本公开针对微电网群同期时的数据采集以及多个微电网群(多个并网点)同期并网问题，在数据处理算法和通信控制方面进行了优化和创新。
发明内容
提供本发明内容是为了以简化的形式介绍所选择的构思，并将在下面的具体实施方式中进一步描述这些构思。本发明内容无意确定所要求保护的主题的关键特征或必要特征，也无意用于帮助确定所要求保护的主题的范围。
本公开以断路器上下口电压幅值、频率和相角作为判断依据，根据同期控制点两端的电压估算结果，对微电网内的分布式电源(主要是电压频率支撑电源)采用快速比例积分进行实时功率调节。在缩短同期时间的同时实现同期条件的准确判断，使合闸对两端微电网的冲击较小，提高同期成功率。其中，本公开的电压估算建立同期控制的差分方程模型以及最优估计模型， 采用最优状态估计对同期需要的状态量进行最优值的获取，极大限度提升同期准确性，从而减少同期合闸的系统冲击，提升系统同期的暂态和动态稳定性。本公开建立了针对单个微电网的同期条件边界模型，进而建立多个微电网群的同期条件边界模型，能够准确判别同期顺序，做到稳定同期的同时提高同期效率，避免出现微电网群内的分布式电源同期不能被调节(备用容量不足)而破坏系统稳定性。
根据本公开的一方面，提供一种微电网群同期控制系统，微电网群可包括多个微电网，所述系统包括中央控制器，所述中央控制器被配置为：从多个微电网中的每个接收并网点的电压测量值；对所述电压测量值进行比例积分调节，并得到上一时刻的电压测量值与当前时刻的控制值之间的差分，以估计针对每个微电网的下一时刻的控制指令；以及向所述多个微电网中的至少一个微电网发送控制指令，以通过锁相控制调节所述多个微电网之间的合闸同期。
所述电压测量值可以以每个采样周期的时间驱动的方式被发送；并且所述控制指令的发送时间间隔可从最小时间间隔增大至心跳时间间隔。
所述中央控制器还可被配置为：通过IEC 61850标准中的SV协议从每个微电网接收电压测量值；通过IEC 61850标准中的GOOSE协议向所述至少一个微电网发送控制指令，并且针对通过SV/GOOSE协议传输的每一帧数据执行单独校验。
所述中央控制器还可被配置为：对所述并网点两侧的电压测量值进行最优状态估计，使得控制指令的误差最小。
所述中央控制器还可被配置为：将对所述差分进行累加求和得到的测量误差累计确定为服从高斯分布。
所述中央控制器还可被配置为：利用上一电压周期的电压测量值的协方差对每个电压测量值进行实时校验。
所述中央控制器还可被配置为：通过对电压测量值进行Park变换成为旋转直角坐标系并进行正交变换得到离散的电压值直轴分量和交轴分量，并作为比例积分调节的输入值。
所述中央控制器还可被配置为：根据所述多个微电网中的每个的容量确定所述多个微电网的调节顺序，并基于当前运行电压参数状态下的裕度确定需要被调节的微电网的同期调节边界。
所述中央控制器还可被配置为：将容量较小的微电网选择为同期先被调节的目标，并且当电压调节参数超过微电网的同期调节边界时改变调节目标。
根据本公开的另一方面，提供一种微电网群同期控制方法，微电网群可包括多个微电网，所述方法包括：从多个微电网中的每个微电网接收并网点的电压测量值；对所述电压测量值进行比例积分调节，得到上一时刻的电压测量值与当前时刻的控制值之间的差分，以用于估计下一时刻的控制指令；以及向所述多个微电网中的至少一个微电网发送控制指令，以通过锁相控制调节所述多个微电网之间的合闸同期。
所述电压测量值可以以每个采样周期的时间驱动的方式被发送；并且所述控制指令的发送时间间隔可从最小时间间隔增大至心跳时间间隔。
所述方法还可包括：过IEC 61850标准中的SV协议从每个微电网接收所述电压测量值，并且通过IEC 61850标准中的GOOSE协议向至少一个微电网发送控制指令；针对通过SV/GOOSE协议传输的每一帧数据执行单独校验。
所述方法还可包括：对所述并网点两侧的电压测量值进行最优状态估计，使得控制指令的误差最小。
所述方法还可包括：将对所述差分进行累加求和得到的测量误差累计确定为服从高斯分布。
所述方法还可包括：利用上一电压周期的电压测量值的协方差对每个电压测量值进行实时校验。
所述方法还可包括：通过对电压测量值进行Park变换成为旋转直角坐标系并进行正交变换得到离散的电压值直轴分量和交轴分量，并作为比例积分调节的输入值。
所述方法还可包括：根据所述多个微电网中的每个的容量选择所述多个微电网的调节顺序，并基于当前运行电压参数状态下的裕度确定需要被调节的微电网的同期调节边界。
所述方法还可包括：将容量较小的微电网选择为同期先被调节的目标，并且当电压调节参数超过微电网的同期调节边界时改变调节目标。
根据本公开的另一方面，提供一种存储有计算机程序的计算机可读存储介质，当所述计算机程序在被处理器执行时实现上述微电网群同期控制方法。
根据本公开的另一方面，提供一种计算机设备，所述计算机设备包括：处理器；存储器，存储有计算机程序，当所述计算机程序被处理器执行时， 实现上述微电网群同期控制方法。
附图说明
通过以下结合附图的详细描述，本公开的以上和其它方面、特征和优点将被更清楚地理解，在附图中：
图1是未施加同期控制的断路器两端的单相电压曲线图；
图2是无电压状态估计的同期控制的断路器两端的单相电压曲线图；
图3是基于就地直采直控的同期控制方式的两个微电网的拓扑图；
图4是采用IEC 61850协议的同期控制方式的拓扑图；
图5是传统模式下的多个微电网的同期控制的拓扑图；
图6是根据本公开的同期控制系统的拓扑图；
图7是根据本公开的同期控制系统的框图；
图8是根据本公开的三相同步锁相环原理的框图；
图9是根据本公开的锁相环输出的电压幅值(V d)曲线图；
图10是根据本公开的锁相环输出的角频率(ω)曲线图；
图11是根据本公开的锁相环输出的电压相角(θ)曲线图；
图12是根据本公开的PI调节器原理的框图；
图13是根据本公开的采用PI调节器进行电压幅值控制的框图；
图14是根据本公开的采用PI调节器进行相角控制的框图；
图15是根据本公开的采用PI调节器进行角频率控制的框图；
图16是根据本公开的有功功率调节的电压动态曲线图；
图17是根据本公开的电压随着有功功率和无功功率变化的函数图；
图18是根据本公开的电压随着有功功率和无功功率变化的函数图；
图19是根据本公开的电压随着有功功率和无功功率变化的函数图；
图20是根据本公开的同期控制系统采用IEC 61850通信的架构图；
图21是根据本公开的GOOSE报文发送过程的示意图；以及
图22是根据本公开的微电网群同期控制方法的流程图。
具体实施方式
提供以下具体实施方式以帮助读者获得对在此描述的方法、设备和/或系统的全面理解。然而，对于本领域普通技术人员在此描述的方法、设备和/或 系统的各种改变、变型和等同物将是显而易见的。例如，在此描述的操作的顺序仅仅是示例，并且不限于在此阐述的顺序，而是除了必须以特定顺序发生的操作之外，可做出对于本领域普通技术人员将显而易见的改变。此外，为了提高清楚性和简洁性，可省略对于本领域普通技术人员将公知的特征和结构的描述。在此描述的特征可以以不同的形式实施，并且将不被解释为局限于在此描述的示例。更确切地说，已经提供在此描述的示例使得本公开将是彻底的和完整的，并且将向本领域普通技术人员充分地传达本公开的范围。
下面是本公开中使用的一些技术术语的定义：
微电网(microgrid)：具有明确电气边界的多个分布式能源和负载互联，为单一可控的系统，既可以运行在并网模式也可以运行在孤岛模式(参照IEC 60050-617:2017中的描述“Group of interconnected loads and distributed energy resources with defined electrical boundaries forming a local electric power system at distribution voltage levels,that acts as a single controllable entity and is able to operate in either grid-connected or island mode”)。
同期(synchronization)：发电机和电网连接时，在同一时期内，要求发电机发出的电压、频率、相位和电网一致。
孤岛(island)：电力系统中与其余部分断开，但仍有电的部分。
暂态扰动(transient disturbance)：由微电网中发电设备投切、负荷启停、微电网非计划孤岛或故障引起的瞬间剧烈的电压和电流变化，其特征是波动幅度大且相位变化明显，持续时间为0-50ms(参照IEC TS 62898-3-1:2020中的描述“Sudden and severe voltage and current changes in a microgrid caused by switching of generation or load,unintentional islanding or faults,characterized by large magnitude and phase changes and continuing for a period of 0ms to 50ms”)。
动态扰动(dynamic disturbance)：由可再生能源的高渗透比和间歇性、非线性负荷、微电网计划性孤岛以及可再生能源输出功率波动和电网侧故障引起的微电网电压、电流的一系列变化，持续时间为50ms～2s(参照IEC TS 62898-3-1:2020中的描述“Series of voltage and current changes in a microgrid caused by output of renewable energy sources reaching a sufficiently high proportion,non-linear loads,intentional islanding,intermittency and output power fluctuation of renewable energy resources and grid side faults,which continue for a period of 50ms to 2s”)。
SV(Sampled Value)：采样值，也称SMV(Sampled Measured Value)。
GOOSE：通用面向对象变电站事件(Generic Object Oriented Substation Events)。
最优状态估计(optimal state estimation)：在某一确定的估计准则条件下，按照某种统计意义，使估计状态达到最优。
电压幅值(voltage amplitude)：在一个周期内，交流电瞬时出现的最大绝对值，也是一个电压正弦波中，波峰到波谷距离的一半。
电压频率(frequency of voltage)：电压矢量在单位时间内完成周期性变化的次数。
电压相角(phase angle of voltage)：又称相位角，指电压矢量随时间(或空间位置)作正弦或余弦变化时，决定其在任一时刻(或位置)状态的一个数值。
现有的同期技术基于就地设置的测量和控制设备对需要同期合闸的断路器端口两端进行电压检测，并基于电压幅值、频率和相角进行同期判断，但同期的时间较长，且难以严格判断同期条件，对断路器断口两端的电网冲击很大，严重情况下导致同期失败。
图1是未施加同期控制的断路器两端的单相电压曲线图。图2是无电压状态估计的同期控制的断路器两端的单相电压曲线图。参照图1，在未施加同期控制策略的情况下，断路器断口两端电压无法快速满足同期条件。即使在偶然条件下满足同期要求也只是暂时存在，无法作为同期合闸的必要条件。在此情况下，虽然系统中的控制器根据通信上传的数据计算得到的同期控制点两端电压符合同期合闸条件并对同期控制点发出了合闸指令，但由于电压数值采集或者通信传输过程中会出现偏差，因此各种误差叠加后经过锁相环(锁相环也会出现误差)计算出来的相角存在误差。参照图2，此时经过同期PI调节器调节的实际电压相角的误差值记为θ err和θ′ err。实际最大误差可能是θ err+θ′ err，此误差是断口两侧采集和计算误差的叠加，并且这个误差可能满足式1：
|θ err+θ′ err|＞θ ref     (1)
其中，θ ref表示同期条件允许的断口两侧电压的相角差的最大值。此时，系统实际上并未满足同期条件，控制器发出合闸指令后，微电网之间会出现较大的冲击电流以及电压动态不稳定，严重情况下会导致同期失败而影响系统安全稳定运行。
可见，现有的并网同期技术无法满足微电网或微电网群的精确同期控制的要求。首先，微电网发电单元和储能系统一般通过电力电子设备连接，电源抗冲击能力较弱，最多过载两倍的额定电流。传统的同期技术易造成系统电流过大而提前保护；其次，微电网系统大部分惯性较弱，暂态稳定能力及动态稳定能力较弱，系统同期的暂态过程和动态过程很可能导致同期失败；并且，微电网孤岛运行系统容量较小且备用容量不足，以至于系统微小的扰动也会引起微电网动态响应时间长，电压动态振荡幅度大。
当两个孤岛运行的微电网需要同期并联运行时，首先要考虑以哪个微电网作为参考，其次考虑满足同期的绝对条件等，现有的同期技术还不能够很好的解决这些问题。同时，现有的就地放置的同期控制器通常接收上级控制指示进行同期合闸，但是针对多个微电网构成的微电网群进行的同期控制涉及多个同期控制点并且同期控制点与同期控制器距离较远，直接采集电压数据和直接控制开关分合不仅无法满足远距离要求，也无法满足时间要求。此外，现有技术无法实现自动同期、自动判别同期最优顺序，因此需要在一个同期控制系统中对所有系统运行状态进行计算，以实现快速通信解决远距离信息传送的问题。
此外，微电网群涉及到多个同期控制点，同期控制点与同期控制器距离较远，直接采集电压数据和直接控制开关分合这种方式无法满足远距离要求。本公开采用IEC 61850的SV和GOOSE通信方式，对开关状态和电压实时值进行采集并对同期断路器进行实时遥控，这种通信控制方式可解决远程通信和多个同期控制点的问题。
本公开的同期控制系统采集同期控制点的状态信息和同期控制点处断路器断口两侧的电压实时数据。由于同期过程需要严格同步，因此采用对时服务器的B码对时。对于多个微电网之间的同期或者同期控制点离同期核心设备较远的情况，采用光纤通信保证采样信号的实时性和不失真，并采用IEC 61850通信方式进行电压数据实时发送以及开关信号实时反馈以及遥控。
图3是基于就地直采直控的同期控制方式的两个微电网的拓扑图。参照图3，工业园区内的典型微电网1可包括三个分布式电源DER1、DER2和DER3以及负荷Load，但不限于此。运行为U/f模式的分布式电源DER1作为微电网系统中的主支撑电源并且能够保证微电网1孤岛运行的稳定性，可以是储能系统、微型燃气轮机、柴油机等稳定微型电源；分布式电源DER2 和分布式电源DER3作为微电网系统中的PQ电源，可以是波动性、间歇性的发电电源，例如，风力发电和光伏发电；负荷Load可以是工业园区10kV用电负荷。微电网2可包括与微电网1相同或相似的三个分布式电源DER1、DER2和DER3以及负荷Load。运行为U/f模式的分布式电源DER1作为微电网系统中的主支撑电源并且能够保证微电网1孤岛运行的稳定性，可以是储能系统、微型燃气轮机、柴油机等稳定微型电源；分布式电源DER2和分布式电源DER3作为微电网系统中的PQ电源，可以是波动性、间歇性发电电源，例如，风力发电和光伏发电；负荷为工业园区内另一10kV负荷。
同期控制点可以是两个微电网之间需要并联运行或解列运行时的断路器。当微电网1与微电网2均独立运行时，微电网1可能出现分布式电源发电功率超过负荷功率而需要进行功率限制的情况，微电网2可能出现分布式电源发电功率不足以支撑工业负荷的情况。因此，有必要将两个微电网并联运行，以提高能源利用率并保障负荷用电。同时，当微电网1或微电网2中某一线路出现故障时，有必要将微电网之间的同期控制点解列，以最大限度保障系统供电可靠性和冗余性且最大限度降低经济损失。
并联运行的多个微电网的联络线一般为阻性。因此，微电网1和微电网2之间的同期在于两个微电网母线电压之间的同期。假设微电网1的母线上三相电压为V abc，微电网2的母线上三相电压为V′ abc。通过锁相环对两条母线电压进行锁相计算，可以得到两条母线上电压幅值、电压相角和频率。微电网1的母线电压三要素分别为V m、θ和ω，其中V m为微电网1母线电压幅值，θ为微电网1母线电压相角，ω为微电网1的母线电压角频率。微电网2的母线电压三要素分别为V′ m、θ′和ω′，其中V′ m为微电网2母线电压幅值，θ′为微电网2母线电压相角，ω′为微电网2母线电压角频率，满足同期合闸的条件如下：
|V m-V′ m|≤V ref     (2)
|θ-θ′|≤θ ref    (3)
|ω-ω′|≤ω ref     (4)
在上式2至式4中，V ref表示同期条件允许的两条母线电压差的最大值，θ ref表示同期条件允许的两条母线相角差的最大值，ω ref表示同期条件允许的两条母线角频率差的最大值。实际中，这些阈值可根据标准或微电网实际运行情况被预先设置。
就地设置的采集设备(可以是诸如电压互感器或分压器等的电压传感器)和控制设备(例如，控制器)的直采直控的同期方式通过二次电气线直接对两个微电网母线的电压参数进行采集，采样值直接发送到同期控制器，同期控制器采用二次电气线对继电器进行开入开出控制，实现同期控制点处的同期合闸。但这种方式中，一个同期装置只能对应一个同期控制点，而且两个微电网距离较远时会出现电压采集数据信号减弱、控制信号失真的现象。
本公开的优选实施例
图4是采用IEC 61850协议的同期控制方式的拓扑图。在此，将省略对附图中相同或相似部分的重复描述，并且将仅描述差异。参照图4，在根据本公开的微电网群同期控制系统中，两个微电网母线之间的电压通过采集设备进行实时数据获取，采集到的的电压测量值通过滤波并按照IEC 61850通信方式进行组帧。同期控制器通过IEC 61850通信方式从每个微电网的采集设备接收并网点的电压测量值(电压测量值以每个采样周期的时间驱动的方式被发送)；基于电压测量值来估计针对每个微电网的下一时刻的控制指令；并且通过IEC 61850通信方式向需要调节的微电网发送控制指令(控制指令的发送时间间隔从最小时间间隔增大至心跳时间间隔)，以通过锁相控制调节所述多个微电网之间的合闸同期。
图5是传统模式下的多个微电网的同期控制的拓扑图。图6是根据本公开的同期控制系统的拓扑图。
参照图5，传统模式当需要四个微电网之间并联运行时则需要三个同期控制装置联合工作，三个同期控制装置均采用直接采集直接控制的方式进行。这种同期的方法中必须提前约定好同期顺序，导致同期效率低下且同期过程无法保证并联同期以后系统的稳定性和经济性。例如，微电网1和微电网2之间的同期完成，系统会进入新的稳定区间，有可能在进入新的稳定区间之前发生暂态不稳定或者动态不稳定问题导致系统再次解列，同期合闸操作失败。
参照图6，针对多个微电网孤岛运行情况下的同期问题，根据本公开的实施例，微电网群的同期控制系统中仅设置一个同期中央控制器，可提高经济型并且可以以最优的时间和最小的冲击电流完成多个微电网之间的同步并机，确保微电网孤岛运行下经济性和稳定性。多个微电网的同期控制系统还采用IEC 61850通信以及远距离光纤传输方式确保通信实时性以及信号不失 真。
根据本公开的实施例，电压测量值和电流测量值的实时采集数据通过就地数据采集设备进行直接采集，保证了数据实时性。直接采集的电压和电流模拟量数据无法进行远距离传送，因此需要就地数据采集设备能够将模拟量转数字量来进行IEC 61850的SV通信，数字量按照IEC 61850的通信协议进行组帧。就地采集设备将采集到的信息通过通信网络(例如，光纤或无线通信)发送至同期中央控制器，保证上送至同期中央控制器的信号的实时性且信号不失真。此外，就地数据采集设备能够采集同期断路器的开关状态并且直接控制断路器，断路器状态采集可通过IEC 61850的GOOSE通信方式由通信网络上送至同期中央控制器。同期中央控制器将同期控制信号以IEC 61850的GOOSE通信方式通过光纤发送到就地控制器，以直接控制断路器。
图7是根据本公开的同期控制系统的框图。参照图7，同期中央控制器承担了输入信息的解码功能以及后续IEC 61850编码功能，同期中央控制器对上送的状态信息进行最优估计，得到实际运行的最优值以提升系统的能控性。最优估计获取测量点的电压幅值、相位和频率；根据实时电压估计值进行锁相；根据计算获取的电压幅值、相位以及频率进行同期比较算法并采用PI调节分别对电压幅值、相位和频率进行快速调节以实现同期合闸操作。
图8是根据本公开的三相同步锁相环原理的框图。参照图8，电网正常运行时为三相平衡状态，在此采用三相同步锁相技术。通过对电压测量值进行Park变换成为旋转直角坐标系并进行正交变换得到离散的电压值直轴分量和交轴分量，并作为比例积分调节的输入值。锁相环输入为三相电压实时采样值，通过对电压测量值进行Park变换成为旋转直角坐标系并进行正交变换得到离散的电压值直轴分量和交轴分量，并作为比例积分调节的输入值，即，利用Park变换将测量值V abc的三相电压矢量由自然坐标系变换至dq同步旋转坐标系，其中d轴分量含有电压幅值信息，q轴分量具有电压相位信息和频率信息。q轴分量为0时V d即表示电压幅值，故将实际电压q轴分量以0作为参考并将其与0值的偏差输入PI调节器模块，把调节结果与电网原有频率ω 0叠加得到角频率ω*，对ω*进行积分运算可获得电压相位角。该锁相方法在正常电网环境下可高精度快速锁相。
图9是根据本公开的锁相环输出的电压幅值(V d)曲线图。图10是根据本公开的锁相环输出的角频率(ω)曲线图。图11是根据本公开的锁相环输 出的电压相角(θ)曲线图。
锁相过程中，输出的V d、ω*和θ即为上述同期三要素Vm、θ和ω。根据上述原理将三相同步锁相环的算法和模型在典型的微电网模型中进行测试，对微电网母线上abc三相电压进行采样，经此三相同步锁相环可精确快速地得到所需状态量。锁相结果如图9至图11所示，可得到短时间内逐步调节至各状态量达到稳定的调节过程，其中锁相的响应时间及精确程度是通过调节PI调节器参数来控制的。
根据本公开的实施例，同期中央控制器执行锁相环的锁相过程以及对分布式电源电压幅值、频率和相位调节过程均使用快速比例积分调节(PI调节)。PI调节器是线性控制器，根据给定值与实际输出值得到控制差分，将差分的比例积分通过线性组合得到控制量对被控对象进行控制。其中，比例参数K p控制的是偏差调节的响应速度，通常随着值的加大系统响应的速度会加快，但是当增加到一定程度系统会变得不稳定。积分调节的主要作用是消除系统稳态误差、提高无误差度，积分参数K i值越大积分作用越弱，反之越强。闭环系统的超调量越小，系统的响应速度也会变慢。
图12是根据本公开的PI调节器原理的框图。参照图12，用于采集同期控制点的电压电流及开关实时状态的数据采集设备采集同期控制点以及微电网系统的必要状态信号，该状态还可根据系统模型计算得到。
图13是根据本公开的采用PI调节器进行电压幅值控制的框图。图14是根据本公开的采用PI调节器进行相角控制的框图。图15是根据本公开的采用PI调节器进行角频率控制的框图。
控制器中的PI调节器对所述电压测量值进行比例积分调节，得到上一时刻的电压测量值与当前时刻的控制值之间的差分，以用于估计下一时刻的控制指令。根据电压幅值控制框图建立同期电压幅值的计算数学模型如下：
V ref-[(V n-1-V n)·K vp+(V n-1-V n)·K vi/s]＝V n    (5)
上式5中，在线性系统或者局部线性计算可以认为V ref是定值。K vp表示电压幅值控制的比例系数，K vi表示电压幅值控制的积分系数，V n表示控制器计算后的输出值，V n-1表示电压幅值状态值反馈。对上式5进行重新变换，将积分项与其余项分开写出可得到如下：
(V n-V n-1)·K vi/s＝V n-V ref+(V n-1-V n)·K vp    (6)
将上式6变换成差分形式，如果用T sample表示实际系统采样周期，得到 离散化模型如下：
Figure PCTCN2021121412-appb-000001
通过差分方程可知积分项实际上表示计算过程中的误差累计。本公开近似认为状态量服从高斯分布，同样可认为误差累积服从高斯分布，因为实际计算和理论仿真的结果也可表明误差与高斯白噪声相似。因此上述控制系统模型可以表述如下：
Figure PCTCN2021121412-appb-000002
并且做如下整理和设定可得：
u(n)＝V ref
V n＝V(n)
V n-1＝V(n-1)
Figure PCTCN2021121412-appb-000003
A＝-K vp/(1-K vp)
B＝1/(1-K vp)
由于对差分进行累加求和得到的测量误差累计服从高斯分布，在此可通过累加消除误差。则电压幅值控制系统的模型重新表达如下：
V(n)＝A·V(n-1)+B·u(n)+ω(n)    (10)
本公开将最优状态估计运用到中压微电网群之间的同期控制中，对同期并网点两侧的电压测量进行最优状态估计，得到较为准确的电压值以用于控制指令，使得控制指令的误差最小。在没有较为准确的电压输入的情况下，同期需要的电压幅值、相位和频率可能因为测量误差、计算误差或通信质量的影响没有达到同期合闸条件，导致同期合闸联络母线上产生较大的冲击电流进而导致同期合闸失败。
本公开根据同期控制的数学模型对同期控制点两端电压数据进行最优状态估计，以确保获取的下一时刻的状态信息的误差最小，在此，误差的大小可通过采样周期内的测量值的协方差来表征。由于模型所需的输入数据通过采样点计算得到，因此模型是离散化的数学模型，将微电网电压的数学模型离散化得到最优状态估计的离散化数学模型如下：
y(t)＝A·y(t-1)+B·u(t)+ω(t)    (11)
在此模型中，y(t)表示当前时刻的状态值，在此可表征当前时刻的电压幅值、相角或频率。y(t-1)表示上一个时刻的状态值，在此可表征上一采样时刻得到的电压幅值、相角或频率。u(t)表示系统的控制作用，在此可表征同期的控制作用。w(t)表示计算等过程出现的误差，在此认为该误差服从高斯分布，误差的协方差为Σ0，均值为μ0。A和B分别表示控制系统参数。根据本公开，还可利用上一电压周期的电压测量值的协方差对每个电压测量值进行实时校验。
同期控制点两端的电压相关数据还可通过传感器测量，离散化的测量系统可以表述如下：
x(t)＝C·y(t)+v(t)    (12)
上式中，x(t)表示当前采样时刻的电压幅值、相角或频率的测量值，v(t)表示测量系统的误差，同样可认为测量误差服从高斯分布，并且测量误差的协方差为Σ1，均值为μ1。
为了得到系统的最优估计值，利用计算过程的数学模型预测系统的下一状态。如果当前时刻为t，则基于上一个时刻状态可预测得到当前时刻的状态，表达式如下：
y<t|t-1>＝A·y<t-1|t-1>+B·u<t>    (13)
上式中，y<t|t-1>表示根据上一状态预测得到的结果，y<t-1|t-1>表示上一时刻的最优值，u<t>表示控制系统的控制作用。由于y<t-1|t-1>表示上一状态的概率分布最优值(加权最优情况下的概率分布期望值)，因此基于上一时刻重现的当前时刻的估计值y<t|t-1>同样服从类似的概率分布，当前时刻的估计值y<t|t-1>的协方差计算如下(详细可参考随机过程)：
Σ<t|t-1>＝A·Σ<t-1|t-1>·A′+Σ 0    (14)
上式中，Σ<t|t-1>表示前时刻的估计值y<t|t-1>的协方差，Σ<t-1|t-1>表示上一时刻的y<t-1|t-1>的协方差。由此得到当前状态的估计值，并结合观测值可得到现阶段状态的最优估计值y<t|t>，表述如下：
y<t|t>＝y<t|t-1>+K G·(x<t>-C·y<t|t-1>)   (15)
最优估计值中K G表示增益系数，其反映测量值和计算值之间的可信度，增益系数的计算如下：
Figure PCTCN2021121412-appb-000004
综上，计算当前状态的协方差如下：
Σ<t|t>＝(E-K G·C)·Σ<t|t-1>    (17)
其中，E表示单位矩阵。
本公开的另一方面还提出建立单个微电网的同期条件边界模型，并据此建立多个微电网的同期条件边界模型，以实现在同期操作之前对同期调节的分布式电源是否具有备用容量和同期后的潮流分布是否超限进行判断。
不同于高压输电网，微电网属于低压系统，其电压值和频率与有功和无功分量都有耦合关系导致系统无法完全解耦。例如，在一些低压微电网系统中，电压可与有功分量相关，频率与无功分量相关。为了将三种情况都进行考虑，本公开建立电压值和频率分别与有功分量和无功分量之间的函数关系：
Figure PCTCN2021121412-appb-000005
传统电力系统中有针对发电机的单位功率调节的概念，因此在微电网中引入下垂系数的概念。下垂系数表示母线电压值和频率随着功率变化的梯度。考虑下垂系数的关系函数式如下：
Figure PCTCN2021121412-appb-000006
系统容量边界条件如下：
Figure PCTCN2021121412-appb-000007
上式中，U 1表示微电网1的母线电压值，F 1表示微电网1母线电压频率，P 1表示微电网1的电压频率支撑电源能够承受有功功率，Q 1表示微电网1的电压频率支撑电源能够承受的无功功率，S 1表示微电网1的电压频率支撑电源视在功率，其最大值不能超过该分布式电源的最大容量，必须注意到下式不成立：
Figure PCTCN2021121412-appb-000008
图16是根据本公开的有功功率调节的电压动态曲线图。参照图16，示出了同期控制点两侧孤岛运行的微电网的频率电压特性，在此考虑低压系统及微电网系统中的电压值和有功分量线性相关，频率和无功分量线性相关的情况。在图16中，曲线1表示微电网1的输出功率与电压值的关系，曲线2表示微电网2的输出功率与电压值的关系。微电网1运行在C点，对应的系 统频率为U 1；微电网2运行在A点，对应的系统频率为U 2。从两个微电网的运行特点来看，微电网1对应的容量较大。同期控制的可将容量较小的微电网作为同期控制的被调节项，而微电网容量较大的作为同期控制的参考项。因此需要将微电网2的电压值调节到U 1，从一次调频曲线变化可知，微电网2的运行曲线从点A到点B，从曲线2变换成曲线3。虽然此时功率没有发生变化，但两个微电网系统并联瞬间会出现暂态冲击功率，造成瞬间功率增加，可能在合闸的瞬间微电网2功率超过最大值导致同期失败。因此，在此电压点进行同期操作有较大的失败风险，可以以该点作为临界点。
本公开根据微电网群系统的各个微电网容量进行同期基准值的选择，根据电压值和频率与功率的函数关系得到当前运行状态下各个微电网的调节裕度并确定同期边界条件，用于确定同期频率点和电压值点以及相位点。此外，考虑低压系统中的传输线路阻抗和感抗，电压与有功功率和无功功率都相关，频率与有功功率和无功功率也相关。根据经验值可做如下修正：
Figure PCTCN2021121412-appb-000009
上式中，m 1表示电压值相对于有功分量下垂系数，a 1、a 2、a 3表示电压值与无功分量之间的拟合关系系数。n 1表示频率相对于无功分量的下垂系数，b 1、b 2、b 3表示频率与有功分量之间的拟合关系系数。这些系数可通过实际测量和计算得到。通过计算得到两个微电网的下垂系数对应曲线，在此仅分析电压值特性的分析方法，此方法还可用于频率特性的分析。
图17是根据本公开的电压随着有功功率和无功功率变化的函数图。图18是根据本公开的电压随着有功功率和无功功率变化的函数图。图19是根据本公开的电压随着有功功率和无功功率变化的函数图。
根据前述的二维函数曲线，参照图18，系统同期控制的最佳同期功率区域在交合区域附近，如果两个将同期合闸并网的微电网运行都运行在交合区域中，则可直接对容量小的微电网发出同期控制指令，使其跟随容量较大的微电网。参照图19，系统容量较大的微电网运行在功率极限附近(如果储能作为主支撑电源则存在吸收和发出最大功率点两种情况)，由于同期瞬间的冲击可能造成大容量微电网过流而导致同期失败，因此不能直接控制小容量微电网的同期跟随大容量微电网的方式。这种情况下需要同期控制器对大容量微电网系统的分布式电源或者可调节负荷进行合理调节。将大容量微电网的 运行点调节回到交合区域中，保证同期瞬间两个系统容量裕度以使得确保同期稳定。因此，可根据多个微电网中的每个的容量选择多个微电网的调节顺序，并基于当前运行电压参数状态下的裕度确定需要被调节的微电网的同期调节边界。例如，可将容量较小的微电网选择为同期先被调节的目标，并且当电压调节参数超过微电网的同期调节边界时改变调节目标。
图20是根据本公开的同期控制系统采用IEC 61850通信的架构图。图21是根据本公开的GOOSE报文发送过程的示意图。
系统中的控制显示界面可由SCADA系统提供，并与中央控制器通信。IEC 61850中的SV(Sampled Value)和GOOSE(面向通用对象的变电站事件，Generic Object Oriented Substation Events)是IEC 61850标准中实时性要求比较高的两种通信协议。IEC 61850通信方式将用于微电网群同期的中央控制器通过SV网络与每个微电网的测量单元MU(就地装置)连接并通过GOOSE网络与每个微电网的控制器(就地装置)连接。本公开采用IEC 61850通信方式中的SV/GOOSE报文格式进行数据交互，以形成高速通信的以太网控制和通信的环形网络架构。采用环形网络而不采用控制中心与微电网设备之间点对点的通信架构，是考虑到系统布线的复杂度和各个微电网间数据交互的实时性。IEC 61850标准下的SV/GOOSE报文采用发布者/订阅者的通信结构。
SV/GOOSE报文是时间驱动的通信方式，即每隔预定时间发送一次采样值。当网络原因导致报文传输丢失时，发布者(微电网就地装置中的电压和电流传感器以及开关量、状态信息等)并不受影响，会继续采集最新的电压和电流以及开关量状态信息等。SV报文是时间驱动的通信方式，可以以预定时间间隔发送采样值，并且预定时间间隔可与采样的时间间隔相同。例如，微电网的电压测量值以每个采样周期的时间驱动的方式被发送。GOOSE报文的发送过程参照图21，其中T0是心跳时间，每隔T0时间发送当前状态，故称为心跳报文。各个微电网就地装置的GOOSE数据中任一成员的数据值发生变化则发送所有数据，然后间隔T1时间发送第二帧及第三帧，间隔T2时间发送第四帧，间隔T3时间发送第五帧，后续报文的发送时间间隔逐渐增加，直到最后报文间隔恢复为心跳时间，即，控制指令的发送时间间隔从间隔T1增大至心跳时间间隔T0。T0可设置为5000ms，T1可设置为2ms，T2看设置为2倍的T1，T3设置为2倍的T2。
图22是根据本公开的微电网群同期控制方法的流程图。
参照图22，在操作221，处理从多个微电网中的每个微电网接收并网点的电压测量值，其中，所述电压测量值以每个采样周期的时间驱动来被发送；在操作222，处理基于所述电压测量值估计针对每个微电网的下一时刻的控制指令；以及在操作223，处理向所述多个微电网中的至少一个微电网发送控制指令，以通过锁相控制调节所述多个微电网之间的合闸同期，其中，所述控制指令的发送时间间隔从最小时间间隔增大至心跳时间间隔。
本公开还提供一种存储有计算机程序的计算机可读存储介质。该计算机可读存储介质存储有当被处理器执行时使得处理器执行根据本公开的微电网群同期控制方法的计算机程序。该计算机可读记录介质是可存储由计算机系统读出的数据的任意数据存储装置。计算机可读记录介质的示例包括：只读存储器、随机存取存储器、只读光盘、磁带、软盘、光数据存储装置和载波(诸如经有线或无线传输路径通过互联网的数据传输)。
本公开还提供一种计算机设备。该计算机设备包括处理器和存储器。存储器用于存储计算机程序。所述计算机程序被处理器执行使得处理器执行根据本公开的微电网群同期控制方法的计算机程序。
本公开中采用IEC 61850的SV和GOOSE通信方式对电压实时采样并发送控制指令，并应用高精度锁相环计算电压的幅值、频率和相位，在具有多个同期控制点的微电网群中仍能够保证所采集数据的准确性和实效性和控制的有效性。
在运行有大量电力电子设备的微电网群系统中利用了更加精准快速的比例积分调节，对微电网内部分布式电源进行功率调控，降低调节难度的同时也进一步保证了同期判别的准确性。
对于传感器测量或信号传输的误差、延迟等问题，采用最优估计模型对同期控制的状态量进行最优值估计，保证同期控制指令最接近系统实际运行情态，极大限度提升了微电网群同期合闸成功率。
对于多个微电网的同期控制，建立多个微电网的同期条件边界模型，准确判断微电网群中的各微电网的同期边界条件，实现系统稳定、快速同期合闸，提高同期效率。
虽然本公开包括具体示例，但是对于本领域普通技术人员将明显的是，在不脱离权利要求及它们的等同物的精神和范围的情况下，可在这些示例中 做出形式上和细节上的各种改变。在此描述的示例将仅被认为是描述性含义，而非出于限制的目的。在每个示例中的特征或方面的描述将被认为可适用于其他示例中的类似的特征或方面。如果按照不同的顺序执行描述的技术，和/或如果按照不同的方式组合描述的系统、架构、装置或者电路中的组件和/或通过其他组件或者它们的等同物替换或者补充描述的系统、架构、装置或者电路中的组件，则可获得适当的结果。因此，本公开的范围不由具体实施方式限定，而是由权利要求及它们的等同物限定，在权利要求及它们的等同物的范围内的所有变型将被解释为包含于本公开中。

Claims (20)

  1. 一种微电网群同期控制系统，所述微电网群包括多个微电网，其特征在于，所述系统包括中央控制器，所述中央控制器被配置为：
    从多个微电网中的每个接收并网点的电压测量值；
    对所述电压测量值进行比例积分调节，并得到上一时刻的电压测量值与当前时刻的控制值之间的差分，以估计针对每个微电网的下一时刻的控制指令；以及
    向所述多个微电网中的至少一个微电网发送控制指令，以通过锁相控制调节所述多个微电网之间的合闸同期。
  2. 根据权利要求1所述的系统，其中，所述电压测量值以每个采样周期的时间驱动的方式被发送；并且
    其中，所述控制指令的发送时间间隔从最小时间间隔增大至心跳时间间隔。
  3. 根据权利要求2所述的系统，其中，所述中央控制器还被配置为：通过IEC 61850标准中的SV协议从每个微电网接收电压测量值；通过IEC 61850标准中的GOOSE协议向所述至少一个微电网发送控制指令，并且针对通过SV/GOOSE协议传输的每一帧数据执行单独校验。
  4. 根据权利要求1所述的系统，其中，所述中央控制器还被配置为：对所述并网点两侧的电压测量值进行最优状态估计，使得控制指令的误差最小。
  5. 根据权利要求4所述的系统，其中，所述中央控制器还被配置为：将对所述差分进行累加求和得到的测量误差累计确定为服从高斯分布。
  6. 根据权利要求5所述的系统，其中，所述中央控制器还被配置为：利用上一电压周期的电压测量值的协方差对每个电压测量值进行实时校验。
  7. 根据权利要求1所述的系统，其中，所述中央控制器还被配置为：通过对电压测量值进行Park变换成为旋转直角坐标系并进行正交变换得到离散的电压值直轴分量和交轴分量，并作为比例积分调节的输入值。
  8. 根据权利要求1所述的系统，其中，所述中央控制器还被配置为：根据所述多个微电网中的每个的容量确定所述多个微电网的调节顺序，并基于当前运行电压参数状态下的裕度确定需要被调节的微电网的同期调节边界。
  9. 根据权利要求8所述的系统，其中，所述中央控制器还被配置为：将 容量较小的微电网选择为同期先被调节的目标，并且当电压调节参数超过微电网的同期调节边界时改变调节目标。
  10. 一种微电网群同期控制方法，所述微电网群包括多个微电网，其特征在于，所述方法包括：
    从多个微电网中的每个微电网接收并网点的电压测量值；
    对所述电压测量值进行比例积分调节，得到上一时刻的电压测量值与当前时刻的控制值之间的差分，以用于估计下一时刻的控制指令；以及
    向所述多个微电网中的至少一个微电网发送控制指令，以通过锁相控制调节所述多个微电网之间的合闸同期。
  11. 根据权利要求10所述的方法，其中，所述电压测量值以每个采样周期的时间驱动来被发送；并且
    其中，所述控制指令的发送时间间隔从最小时间间隔增大至心跳时间间隔。
  12. 根据权利要求11所述的方法，其中，所述方法还包括：过IEC 61850标准中的SV协议从每个微电网接收所述电压测量值，并且通过IEC 61850标准中的GOOSE协议向至少一个微电网发送控制指令；
    针对通过SV/GOOSE协议传输的每一帧数据执行单独校验。
  13. 根据权利要求10所述的方法，其中，所述方法还包括：对所述并网点两侧的电压测量值进行最优状态估计，使得所述控制指令的误差最小。
  14. 根据权利要求13所述的方法，其中，所述方法还包括：将对所述差分进行累加求和得到的测量误差累计确定为服从高斯分布。
  15. 根据权利要求14所述的方法，其中，所述方法还包括：利用上一电压周期的电压测量值的协方差对每个电压测量值进行实时校验。
  16. 根据权利要求10所述的方法，其中，所述方法还包括：通过对电压测量值进行Park变换成为旋转直角坐标系并进行正交变换得到离散的电压值直轴分量和交轴分量，并作为比例积分调节的输入值。
  17. 根据权利要求10所述的方法，其中，所述方法还包括：根据所述多个微电网中的每个的容量选择所述多个微电网的调节顺序，并基于当前运行电压参数状态下的裕度确定需要被调节的微电网的同期调节边界。
  18. 根据权利要求17所述的方法，其中，所述方法还包括：将容量较小的微电网选择为同期先被调节的目标，并且当电压调节参数超过微电网的同 期调节边界时改变调节目标。
  19. 一种存储有计算机程序的计算机可读存储介质，其特征在于，当所述计算机程序在被处理器执行时实现如权利要求10至18中任意一项所述的微电网群同期控制方法。
  20. 一种计算机设备，其特征在于，所述计算机设备包括：
    处理器；
    存储器，存储有计算机程序，当所述计算机程序被处理器执行时，实现如权利要求10至18中任意一项所述的微电网群同期控制方法。
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CN110768261A (zh) * 2019-12-02 2020-02-07 国网江苏省电力有限公司徐州供电分公司 一种基于状态空间预测的储能型dvr控制方法
CN113300408A (zh) * 2021-04-30 2021-08-24 北京天诚同创电气有限公司 微电网群同期控制方法和系统

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CN115542146A (zh) * 2022-11-30 2022-12-30 南方电网调峰调频发电有限公司 发电机组出口开关装置同期测试方法、装置、设备及介质
CN115542146B (zh) * 2022-11-30 2023-03-24 南方电网调峰调频发电有限公司 发电机组出口开关装置同期测试方法、装置、设备及介质
CN117810971A (zh) * 2023-12-14 2024-04-02 重庆新世杰电气股份有限公司 一种自适应同期检查方法
CN117728506A (zh) * 2024-02-08 2024-03-19 国网浙江省电力有限公司经济技术研究院 一种构网型储能自适应平滑并网方法、系统、设备及介质
CN117728506B (zh) * 2024-02-08 2024-05-24 国网浙江省电力有限公司经济技术研究院 一种构网型储能自适应平滑并网方法、系统、设备及介质

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