CN103618327A - Large power energy storage current transformer and main circuit thereof - Google Patents

Abstract

The invention relates to a large power energy storage current transformer and a main circuit thereof. A main circuit of the current transformer includes a bidirectional AC/DC current transforming module which is composed of two three-phase full-bridge IGBT power transforming units connected in parallel, the AC side of the bidirectional AC/DC current transforming module is used for connecting an electrical network, and the DC side is used for connecting an energy storage medium. Conventional two-stage transformation is substituted by one-stage transformation, problems of high manufacturing cost, complex control and low reliability of a present large power energy storage current transformer adopting two-stage transformation are solved.

Description

A high-power energy storage converter and its main circuit

technical field

The invention relates to a high-power energy storage converter and its main circuit.

Background technique

Changes in power supply structure and electricity consumption characteristics have increased the demand for energy storage technology in the power system. Distributed power generation technology for renewable energy power generation has become the focus of development in my country's energy field, but renewable energy power generation such as wind energy and solar energy has different characteristics. Stable and discontinuous, it is an unstable energy source, which is greatly affected by natural conditions and control systems, especially when there is a new energy electric field that may have a small output during peak load periods, but a new energy electric field that may output a large amount during non-peak load periods question. The power supply of the power system to the user must be in a balanced state at all times. The power plant and the grid must supply as much power as the user needs, neither more nor less. Once this balance is disrupted, the power quality will deteriorate, causing The frequency and voltage are unstable, and it will cause large-scale power outages.

In order to balance the deviation between power generation and power consumption, power needs to be balanced. The energy storage system can store energy during off-peak load periods and release energy during peak load periods to make the new energy electric field system run more efficiently and economically. Large-scale Distributed energy storage technology can well solve related problems caused by wind power and solar power fluctuations. As a load balancing device and backup power source, the energy storage system is also a key technology necessary for smart grids and distributed energy systems, and is used to solve problems such as high failure rate, small system capacity, and large load fluctuations. It can be said that energy storage technology is the core of the new energy industry revolution. Without the development of energy storage technology, there will be no large-scale application and development of renewable energy.

The high-power energy storage converter is an important part of the energy storage system. It is mainly composed of switchgear, three-phase high-frequency IGBT converter, and power frequency transformer (boosted by the transformer, and the DC side has a wider DC voltage range. It is beneficial to battery grouping, and can adapt to grid applications of various voltage levels by changing the transformation ratio of the transformer), control unit and other components. In the working state of energy storage, the energy storage converter receives station-level monitoring command control equipment to charge the energy storage medium; in the discharge working state, the energy storage converter receives station-level monitoring command control equipment to discharge to the grid through the energy storage medium , to realize the function of peak shaving and valley filling, and it can also be used as a backup emergency power supply for the local area network. When connected to the grid, the energy storage medium is charged and stored by the energy storage converter. After off-grid, the energy storage medium passes through the energy storage converter. Provide power support for local area network discharge.

High-power energy storage converters are mainly applied to energy storage systems of MW level and above. Energy storage systems of MW level and above usually adopt distributed grid-connected design schemes, with 1MW×nh as the basic unit, each unit The interior is composed of two sets of 500kW energy storage converters and connected energy storage media and their management systems. Each 500kW energy storage converter is connected to a 0.4kV or 10kV AC grid through an isolation transformer, and the DC side of the energy storage converter The connected energy storage medium is configured according to project needs, and can form 1WM×nh level energy storage systems with different capacities.

In the existing energy storage converter technology, most of them are reformed from photovoltaic inverters, and there are the following problems: 1) The photovoltaic inverter is a one-way energy conversion device, which can only realize the conversion from photovoltaic (DC source) to the power grid. 2) The control modes of the inverter and the converter are quite different; 3) When running the charging mode, due to the lack of a filter circuit on the DC side of the photovoltaic inverter, it may be caused by a large DC ripple. The service life of the energy storage medium is greatly reduced. There are also some designs that use a two-stage conversion main circuit topology. When two-stage conversion is used, if a single machine achieves high power or super high power, there will be a significant increase in manufacturing costs and more complex control and protection problems, resulting in low reliability.

Contents of the invention

The purpose of the present invention is to provide a high-power energy storage converter and its main circuit to solve the problems of high manufacturing cost, complex control and low reliability of the existing high-power energy storage converter using two-stage conversion.

In order to achieve the above object, the solution of the present invention is: a main circuit of a high-power energy storage converter, including a bidirectional AC/DC converter module, the bidirectional AC/DC converter module is composed of at least two three-phase full-bridge IGBT The power conversion units are connected in parallel, the AC side of the bidirectional AC/DC conversion module is used to connect to the grid, and the DC side is used to connect to the energy storage medium.

The AC side of each of the three-phase full-bridge IGBT power conversion units is connected with an LCL filter, and the paralleled DC output side is connected with a CL filter, and each of the LCL filters shares a set of inductors and capacitors.

The AC side of the bidirectional AC/DC converter module is also provided with an AC EMI filter, and the DC side is provided with a DC EMI filter.

The DC side of the three-phase full-bridge IGBT power conversion unit is also connected with a DC bus capacitor.

The present invention also provides a high-power energy storage converter, including the main circuit of the energy storage converter and an energy storage controller. The energy storage controller is provided with an optical fiber trigger and detection port for controlling the IGBT The communication port of the energy storage medium management system and the communication port used to connect to station-level monitoring, the main circuit of the energy storage converter includes a bidirectional AC/DC converter module, and the bidirectional AC/DC converter module consists of two three-way Phase full-bridge IGBT power conversion units are connected in parallel, the AC side of the bidirectional AC/DC converter module is used to connect to the power grid, and the DC side is used to connect to the energy storage medium, the light trigger and detection port is connected to the bidirectional AC/DC module connection.

The AC side of each of the three-phase full-bridge IGBT power conversion units is connected with an LCL filter, and the paralleled DC output side is connected with a CL filter, and each of the LCL filters shares a set of inductors and capacitors.

The AC side of the bidirectional AC/DC converter module is also provided with an AC EMI filter, and the DC side is provided with a DC EMI filter.

A DC bus capacitor is also connected to the DC side of the three-phase full-bridge IGBT power conversion unit.

The beneficial effects achieved by the present invention: the main circuit of the converter of the present invention includes a bidirectional AC/DC conversion module, which is composed of two three-phase full-bridge IGBT power conversion units connected in parallel, and realizes high-power energy conversion. At the same time, the present invention The use of one-stage conversion instead of two-stage conversion reduces the manufacturing cost, and only needs to control the IGBT of the AC/DC converter module to trigger conduction to realize the charging and discharging function. The control process is simpler and easier to implement in engineering.

The main circuit of the converter of the present invention is provided with an LCL filter on the AC side of the bidirectional AC/DC conversion module, and a CL filter on the DC side. The AC side LCL filter can greatly reduce the high-frequency harmonic current on the AC side, and at the same time It can reduce the influence of grid parameters on the device and improve the reliability of the device; the CL filter on the DC side can filter out the high-frequency components in the DC current, reduce the ripple of the output current and voltage, and improve the service life of the energy storage medium. Therefore, the comprehensive application of the LCL filter and the CL filter not only realizes the power quality index and power output of the AC side, but also achieves the low ripple performance index of the DC side.

The main circuit of the converter of the present invention is provided with EMI filters on the AC side and the DC side of the bidirectional AC/DC conversion module respectively. The AC side EMI filter can not only suppress the influence of high-frequency interference in the grid on the device, but also suppress The interference of the device to the power grid; the EMI filter on the DC side can reduce the common-mode interference on the DC side and improve the stability of the device.

Description of drawings

Fig. 1 is a topological structure diagram of the main circuit of the energy storage converter of the present invention;

Fig. 2 is a structural principle diagram of the energy storage system of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Embodiment of the main circuit of the converter:

The main circuit of the converter of the present invention includes a bidirectional AC/DC converter module, the bidirectional AC/DC converter module is composed of two three-phase full-bridge IGBT power conversion units connected in parallel, the bidirectional AC/DC converter module The AC side is used to connect to the grid, and the DC side is used to connect to the energy storage medium.

As shown in Figure 1, the main circuit of the energy storage converter of the present invention includes an AC-side LCL filter, two parallel-connected IGBT power conversion units, a DC-side CL filter, an AC EMI filter, and a DC EMI filter. The AC side of the converter is used to connect to the 0.4kV or 10kV AC grid through the isolation transformer, and the DC side of the energy storage converter is used to connect to the energy storage medium. When the energy storage medium is charged, the IGBT power conversion unit rectifies the AC power on the grid side into DC to charge the energy storage medium; when the energy storage medium is discharged, the IGBT power conversion unit inverts the DC power into AC and feeds it back to the grid. The conversion between can be realized within 200ms.

The middle points of the three half-bridge IGBT bridge arms are connected in series with reactors 1HLa, 1HLb, and 1HLc in sequence to form a three-phase full-bridge circuit, which is connected in parallel with another identical three-phase full-bridge circuit, on the DC side of each IGBT power unit Both are equipped with DC bus capacitors. In this embodiment, laminated plane bus bars are used to connect the IGBTs and DC bus capacitors. Each IGBT is installed on a radiator respectively. The IGBT driver board uses the Concept driver board 2SP0320x2Ax-FF1400R12IP4. Drive, isolation, and protection are integrated, and can be directly installed on the IGBT. The IGBT drive board communicates with the controller of the energy storage converter through an optical fiber. The PWM light trigger signal is directly sent to the IGBT drive board. Feedback directly to the corresponding controller to achieve fast locking; reactors 1HLa, 1HLb, 1HLc and 2HLa, 2HLb, 2HLc can effectively improve the current sharing effect and have dual functions of circulating current suppression and filtering. In operation, the reactor HLdc on the DC output side of the three-phase inverter bridge uses a 550A reactor, and the AC side reactors 1HLa, 1HLb, 1HLc and 2HLa, 2HLb, 2HLc use a 1100A three-phase reactor.

The LCL filter on the AC side can greatly reduce the high-frequency harmonic current on the AC side, and at the same time reduce the influence of grid parameters on the device and improve the reliability of the device; the EMI filter on the AC side can not only suppress the high-frequency interference in the grid to the device The impact of the device can also suppress the interference of the device to the power grid; the DC side CL filter can filter out the high frequency components in the DC current, reduce the ripple of the output current and voltage, and improve the service life of the energy storage medium; the DC side EMI filter The device can reduce the common mode interference on the DC side and improve the stability of the device.

The design basis of the LCL filter:

(1) To ensure the bypass effect of the filter capacitor on the high-frequency ripple current, the capacitive reactance XC must be less than 20% of the grid-side inductive reactance;

(2) The impedance voltage drop generated by the total inductance of the LCL filter is less than 10% of the grid voltage under normal rated operating conditions;

(3) In order not to make the resonance point of the LCL filter appear in the high frequency or low frequency band, the resonance frequency of the designed LCL filter should be greater than 10 times the grid frequency and less than 1/2 of the switching frequency.

DC side filter design basis:

其中，L_dc为直流电感值，C_dc为直流母线电容，由于C_dc已知，因此可以求解出直流电感值L_dc；(1) According to the charging and discharging conversion time: Since the dynamic characteristics of the AC side current loop are much larger than the CL filter time constant, the charging and discharging conversion time mainly depends on the CL filter time constant, according to the calculation formula of the CL filter time constant

Among them, L _dc is the DC inductance value, and C _dc is the DC bus capacitance. Since C _dc is known, the DC inductance value L _dc can be calculated;

其中，Δu_dc为直流母线电压值，Δi_bat为直流母线电流值，由此可以求出直流电感值。(2) According to the battery current ripple: the battery current ripple is generated due to the DC bus voltage fluctuation,

Among them, Δu _dc is the voltage value of the DC bus, and Δi _bat is the current value of the DC bus, from which the value of the DC inductance can be obtained.

Energy storage converter embodiment:

The energy storage converter of the present invention includes the main circuit of the energy storage converter and an energy storage controller, the energy storage controller is provided with an optical fiber trigger and detection port for controlling the IGBT valve, and a port for connecting the energy storage medium management system The communication port and the communication port used to connect to station-level monitoring, the main circuit of the energy storage converter includes a bidirectional AC/DC converter module, and the bidirectional AC/DC converter module is composed of two three-phase full-bridge IGBT power converters The units are connected in parallel, the AC side of the bidirectional AC/DC converter module is used to connect to the power grid, and the DC side is used to connect to the energy storage medium, and the light trigger and detection port is connected to the bidirectional AC/DC module.

As shown in Figure 2, the energy storage controller receives the background control command through the LAN communication interface, and controls the IGBT power conversion unit to charge or discharge the energy storage medium according to the sign and size of the power command, so as to realize the control of the active power and reactive power of the grid. Adjustment; the energy storage controller communicates with the energy storage medium management system through the CAN interface to obtain the status information of the energy storage medium, which can realize the protective charge and discharge of the energy storage medium and ensure the safe operation of the energy storage medium. The human-machine unit monitors and communicates with the energy storage medium on-site through Ethernet, and completes functions such as calibration and equalization of the energy storage medium. The energy storage converter can also collect grid information, participate in the voltage/reactive power control of the grid, and realize anti-islanding Protection, or as an emergency power supply and other functions.

The specific implementation process of the main circuit of the energy storage converter is the same as the above embodiment of the main circuit of the energy storage converter, and will not be repeated here.

Claims (8)

1. A main circuit of a high-power energy storage converter, characterized in that it comprises a bidirectional AC/DC converter module, and the bidirectional AC/DC converter module is composed of at least two three-phase full-bridge IGBT power conversion units connected in parallel , the AC side of the bidirectional AC/DC converter module is used to connect to the grid, and the DC side is used to connect to the energy storage medium. 2. The main circuit of the high-power energy storage converter according to claim 1, wherein the AC side of each of the three-phase full-bridge IGBT power conversion units is connected with an LCL filter, and the DC output side after parallel connection A CL filter is connected, and each LCL filter shares a set of inductors and a set of capacitors. 3. The main circuit of the high-power energy storage converter according to claim 1, characterized in that, the AC side of the bidirectional AC/DC converter module is also provided with an AC EMI filter, and the DC side is provided with a DC EMI filter device. 4. The main circuit of the high-power energy storage converter according to claim 1, characterized in that, the DC side of the three-phase full-bridge IGBT power conversion unit is also connected with a DC bus capacitor. 5. A high-power energy storage converter, including the main circuit of the energy storage converter and an energy storage controller, the energy storage controller is provided with an optical fiber trigger and detection port for controlling the IGBT valve, and is used to connect the energy storage The communication port of the media management system and the communication port used to connect to station-level monitoring are characterized in that the main circuit of the energy storage converter includes a bidirectional AC/DC converter module, and the bidirectional AC/DC converter module consists of two Three-phase full-bridge IGBT power conversion units connected in parallel, the AC side of the bidirectional AC/DC converter module is used to connect to the power grid, and the DC side is used to connect to the energy storage medium, the light trigger and detection port is connected to the bidirectional AC /DC module connection. 6. The high-power energy storage converter according to claim 5, wherein the AC side of each of the three-phase full-bridge IGBT power conversion units is connected with an LCL filter, and the paralleled DC output side is connected with a CL filter, each of the LCL filters shares a set of inductors and a set of capacitors. 7. The high-power energy storage converter according to claim 5, characterized in that, the AC side of the bidirectional AC/DC converter module is further provided with an AC EMI filter, and the DC side is provided with a DC EMI filter. 8 . The high-power energy storage converter according to claim 5 , wherein a DC bus capacitor is connected to the DC side of the three-phase full-bridge IGBT power conversion unit.

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