CN114498714B - New energy storage system with distributed access to flexible traction transformer and control method - Google Patents
New energy storage system with distributed access to flexible traction transformer and control method Download PDFInfo
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60M—POWER SUPPLY LINES, AND DEVICES ALONG RAILS, FOR ELECTRICALLY- PROPELLED VEHICLES
- B60M3/00—Feeding power to supply lines in contact with collector on vehicles; Arrangements for consuming regenerative power
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/102—Parallel operation of dc sources being switching converters
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/106—Parallel operation of dc sources for load balancing, symmetrisation, or sharing
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/14—Balancing the load in a network
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
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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
- 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
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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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
- 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
- H02J2300/28—The renewable source being wind energy
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- 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
- Y02E70/00—Other energy conversion or management systems reducing GHG emissions
- Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
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Abstract
The invention discloses a new energy storage system with a distributed access flexible traction transformer and a control method, which comprises the following steps of: the system comprises a flexible traction transformer, an isolated DC/DC converter, a direct current bus and a new energy storage device; the flexible traction transformer is connected with the isolated DC/DC converter; the isolated DC/DC converter is respectively connected with the flexible traction transformer and the direct current bus; the direct current bus is connected with the new energy storage device; the new energy storage device is used for transmitting power to the direct current link of the flexible traction transformer; according to the invention, the energy storage device is used for reducing wind and light abandonment, providing convenience for access and nearby consumption of various new energy sources, coordinating regenerative braking energy storage, realizing optimal utilization of the new energy sources and the regenerative braking energy, and promoting green and healthy railway traction power supply.
Description
Technical Field
The invention relates to the technical field of traction power supply of electrified railways, in particular to a new energy storage system with a flexible traction transformer connected in a scattered mode and a control method.
Background
In recent years, attention has been paid to power generation by renewable energy sources typified by photovoltaic power, wind power, and the like, and a new power system era mainly based on new energy has been started. The new energy is accessed to the electrified railway, so that the new energy can be consumed nearby, the basic national policy of energy conservation and emission reduction in China and the development requirement of green railways are met, and the method has high economic benefit.
At present, the research on new energy access to the electrified railway at home and abroad mainly focuses on low-voltage system power supply such as station power utilization, signal and communication, and the research on access to a traction power supply system is less. New energy power generation is connected into a traction power supply system, and a complex connection structure and a control method are involved. The prior art provides a grid-connected system for in-phase traction power supply and remote power generation, but does not consider the coexistence of multiple new energy sources, and does not relate to how to access the multiple new energy sources into the traction power supply system; in addition, a distributed power generation system connected into a traction substation and a control method are provided, the method is characterized in that a new energy convergence power cable is arranged in a corridor along a railway and then connected into a traction bus of the traction substation, but the method has the problems that the convergence cable is large in consumption, multiple access points cause complex tide distribution and the like, new energy fluctuation and intermittence directly influence the stability of a traction network through the traction bus, and the resonance of the traction network is aggravated.
The new energy is converted into 27.5kV single-phase alternating current to be directly connected into a traction network, the new energy utilization rate is high, but photovoltaic fluctuation can directly interfere with the traction network; or the new energy is inverted into three-phase alternating current to be accessed into a special three-phase power grid for the railway, the new energy utilization rate is low, and the technical difficulty and the construction cost for accessing the high-voltage side are high; or the new energy is inverted into three-phase alternating current and then is connected into the two power supply arms through a three-phase-two-phase (out-of-phase) transformer for the railway, and the new energy is also output to the two power supply arm network side transformers through a back-to-back converter.
How to efficiently access new energy into a traction power supply system, the requirement of near consumption of the new energy is met, the phenomena of 'wind and light abandonment' are reduced, the influence of photovoltaic fluctuation and intermittence on a traction network is effectively inhibited, and the improvement of the utilization rate and the stability of the new energy is a hotspot of the current research on the new energy access into the traction power supply system.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a new energy storage system and a control method for dispersedly accessing a flexible traction transformer, aiming at solving the problems of accessing various new energies with larger capacity, stably and efficiently accessing a traction power supply system, and improving the utilization rate of the new energies and regenerative braking energy by coordinating and controlling.
In order to achieve the purpose of the invention, the invention adopts the technical scheme that:
on the one hand, a new forms of energy storage system of flexible traction transformer is inserted in dispersion includes:
the system comprises a flexible traction transformer, an isolated DC/DC converter, a direct current bus and a new energy storage device;
the flexible traction transformer is connected with the isolated DC/DC converter and is used for receiving energy of the isolated DC/DC converter;
the isolated DC/DC converter is respectively connected with the flexible traction transformer and the direct current bus and is used for adjusting the direct current voltage of the flexible traction transformer and bidirectionally and controllably adjusting the transmitted energy;
the direct current bus is connected with the new energy storage device and used as an energy convergence bus for receiving the power transmitted by the new energy storage device and transmitting the power to the isolated DC/DC converter;
the new energy storage device is used for supplying power to the flexible traction transformer and the isolated DC/DC converter and storing regenerative braking energy.
Preferably, the flexible traction transformer comprises a traction transformer, a multi-winding step-down transformer, an ac-dc-ac converter;
the traction transformer is connected with the multi-winding step-down and used for receiving and transforming three-phase power grid voltage;
the multi-winding step-down transformer is connected with the AC-DC-AC converter and is used for receiving the transmission power of the traction transformer, reducing the transmission power, obtaining and transmitting the reduced power to the AC-DC-AC converter;
the alternating current-direct current-alternating current converter is connected with the isolation type DC/DC converter and used for changing three-phase alternating current into single-phase alternating current by electric energy, and energy in a new energy storage device with a direct current bus gathered is connected into a direct current link through the isolation type DC/DC converter and is supplied to a single-phase traction power supply network.
The preferred scheme has the following beneficial effects:
the power is connected into the traction network through the isolated DC/DC converter and the single-phase cascade inverter, so that the energy stability is greatly enhanced, and the power transmitted by the new energy storage system is connected into the traction network through the flexible traction transformer without involving the transformation of the traction network, thereby being easy to realize engineering.
Preferably, the ac-dc-ac converter comprises a three-phase rectifier, a single-phase cascade inverter;
the three-phase rectifier is respectively connected with the multi-winding step-down transformer, the single-phase inverter and the isolated DC/DC converter and is used for rectifying three-phase alternating current output by the multi-winding step-down transformer into direct current;
the single-phase inverter is connected with the isolation type DC/DC converter and is used for realizing the bidirectional flow of energy in the single-phase cascade inverter.
The preferable scheme has the following beneficial effects:
the independent control of the three-phase power grid side and the traction grid side is realized through three-phase rectification and single-phase inversion, so that the complete controllability of the electric energy quality is realized, and new energy and energy of an energy storage system are accessed in a direct current link.
Preferably, the single-phase-stage inverter includes a plurality of cascade modules, and bypass switches are provided outside each cascade module, and the number of cascade modules is the same as that of the isolated DC/DC converters.
The preferred scheme has the following beneficial effects:
the isolated DC/DC converter can realize fault operation of the AC-DC-AC converter when the cascade module in the single-phase cascade inverter has a fault.
Preferably, the cascade module comprises a plurality of normal operation modules and a plurality of redundant standby modules, wherein the maximum accessible new energy capacity calculation formula of the flexible traction transformer is represented as follows:
Pc1+Pc2+……+Pcm＝m*Pc
the method comprises the steps that Pcm is the capacity of cascade modules in the mth single-phase cascade inverter, m is the number of cascade modules in normal operation, pc is the capacity value of a single cascade module, and Pc1= Pc2= … … = Pcm = Pc.
The preferred scheme has the following beneficial effects:
the method has the advantages that the large access capacity is realized, the maximum capacity can reach the design capacity of the cascade inverter, and the method is suitable for a new energy system with large access capacity;
preferably, the new energy storage device adopts a direct current mode networking and comprises a new energy subsystem and an energy storage subsystem;
the new energy subsystem is connected with the direct current bus, comprises a new energy converter and a new energy power generation module which are connected, and is used for receiving power transmitted by the new energy power generation module through the new energy converter and transmitting the power to a direct current link of the flexible traction transformer through the isolated DC/DC converter.
The energy storage subsystem is connected with the direct current bus, comprises a bidirectional DC/DC energy storage converter and an energy storage module which are connected and is used for absorbing or storing the fluctuating power of the direct current bus through the bidirectional DC/DC energy storage converter and inhibiting the power fluctuation of the new energy subsystem.
The preferred scheme has the following beneficial effects:
the novel energy system has the advantages that multiple new energy sources such as photovoltaic energy, wind power and the like are gathered in a direct current bus converging mode, the flexible traction transformer is connected into the isolated DC/DC converter, and finally the flexible traction transformer is connected into the traction power supply system, so that the multiple new energy sources are connected into the traction power supply system, the energy storage subsystem is arranged on the direct current bus, energy fluctuation and intermittence of the energy of the new energy system are effectively inhibited, the energy is reasonably stored under the condition that the new energy system has energy surplus, and 'wind and light abandoning' is reduced.
On the other hand, the control method of the new energy storage system dispersedly connected to the flexible traction transformer is characterized by comprising the following steps:
s1, collecting voltage information of each port in a new energy storage system to calculate power of each port;
s2, judging whether the single-phase traction power supply network is in a load state at present according to the power of the traction network in the power of each port, if so, recording that the energy inflow of the single-phase traction power supply network is positive, and entering the step S3; otherwise, recording that the energy returned to the flexible traction transformer is negative, and entering the step S7;
s3, judging whether the power of the traction network is larger than the sum of the power of the new energy subsystem and the power of the energy storage subsystem, and if so, entering a step S4; otherwise, entering step S5;
s4, judging whether the charge state of the energy storage subsystem is larger than the minimum charge state of the energy storage subsystem, if so, enabling the new energy subsystem to be in a maximum power point tracking state, releasing energy by the energy storage subsystem, and complementing the difference power by a three-phase power grid, otherwise, enabling the new energy subsystem to be in the maximum power point tracking state, stopping the energy storage subsystem, and complementing the difference power by the three-phase power grid;
s5, judging whether the power of the new energy subsystem is larger than the power of a traction network, if so, entering a step S6, otherwise, keeping the new energy subsystem in a maximum power point tracking state, and complementing the difference power by the energy storage subsystem;
s6, judging whether the difference value between the power of the new energy subsystem and the power of the traction network is larger than the maximum charging power of the energy storage subsystem or not, if so, reducing the power of the new energy subsystem to generate power, and absorbing and storing energy by the energy storage subsystem; otherwise, the new energy subsystem is in a maximum power point tracking state, and the energy storage subsystem absorbs and stores energy;
s7, judging whether the charge state of the energy storage subsystem is smaller than the maximum value of the charge state of the energy storage subsystem, if so, entering a step S8, otherwise, stopping power generation of the new energy subsystem, stopping the work of the energy storage subsystem and consuming regenerative braking energy;
s8, judging whether the power of the traction network is smaller than the maximum charging power of the energy storage subsystem or not, if so, absorbing and storing surplus energy by the energy storage subsystem, and reducing power generation by the new energy subsystem; otherwise, the energy storage subsystem absorbs and stores surplus energy, the new energy subsystem stops generating electricity, and part of regenerative braking energy is consumed.
Preferably, step S1 is specifically:
and acquiring voltage information of each port in the new energy storage system to calculate traction network power, new energy subsystem power, energy storage subsystem charge state, isolated DC/DC converter power and three-phase power grid power, so as to obtain power of each port.
The preferred scheme has the following beneficial effects:
when the traction network is positively supplied with energy, the new energy storage subsystem and the three-phase power network are in a complementary relationship, the energy of the new energy storage subsystem is preferentially consumed, and the three-phase power network supplements the power difference; when the power of the new energy is larger than that of the traction network, the redundant energy can be stored through the energy storage subsystem; the high-capacity cascade inverter can be connected with a high capacity, the maximum capacity can reach the design capacity of the cascade inverter, and the high-capacity cascade inverter is suitable for a new energy system with high access capacity and realizes the storage and utilization of regenerative braking energy.
Preferably, when a cascade module in the single-phase inverter fails, the isolated DC/DC converter adopts an emergency redundancy strategy;
the emergency redundancy strategy specifically comprises the following steps:
the method comprises the steps that a bypass switch is arranged outside each cascade module in a single-phase inverter, when an enabling signal of each cascade module in the single-phase inverter is defined to be a low level, the single-phase inverter normally works, the enabling signal of each cascade module in the single-phase inverter is defined to be a high level, the single-phase inverter stops working, the enabling signal of each cascade module in the single-phase inverter is inverted to the signal state of an isolation type DC/DC converter, and when the cascade module breaks down, the enabling signal corresponding to the fault module is a high level, and the fault module stops working; meanwhile, in order to ensure the normal work of the single-phase inverter, required power is supplied to the direct current link corresponding to the fault module through the new energy subsystem and the energy storage subsystem, when the cascade module in the single-phase inverter stops working due to a fault, the isolation type DC/DC converter corresponding to the cascade module stops working, and the redundancy standby modules with corresponding quantity are started, wherein the power of the isolation type DC/DC converter corresponding to the redundancy standby modules is expressed as:
P_ISx＝Pt/m
p _ ISx is the power of the xth isolated DC/DC converter, pt is the power of a traction network, and m is the number of normally-operated isolated DC/DC converters.
The preferred scheme has the following beneficial effects:
through the cooperation cascade inverter redundancy control, after the module operation breaks down and puts into redundancy module, still effectively utilize the new forms of energy to through setting up redundant spare module, guarantee that single-phase cascade inverter when breaking down, the access of new forms of energy is not influenced, still can normally work under the trouble condition.
Preferably, the power control of each isolated DC/DC converter is independent, and the voltage of the direct current side of the corresponding cascade module in the single-phase inverter is adjusted to follow the voltage of the new energy storage system, so that the power balance of the cascade module is realized; and when the power of the traction network is larger than zero, each isolated DC/DC converter equally divides the power of the new energy subsystem and the power of the energy storage subsystem transmitted by the direct current bus.
The invention has the following beneficial effects:
the method comprises the following steps: the system comprises a flexible traction transformer, an isolated DC/DC, a direct current bus and an energy storage device; the flexible traction transformer is connected with the isolated DC/DC and used for receiving energy of the isolated DC/DC converter; the isolated DC/DC is respectively connected with the flexible traction transformer and the direct current bus, is used for adjusting the direct current voltage of the flexible traction transformer and bidirectionally and controllably adjusting the transmitted energy, and can realize the fault operation of the AC-DC-AC converter when the cascade module in the single-phase inverter has a fault; the direct current bus is connected with the new energy storage device, serves as an energy convergence bus, and is used for connecting the isolated DC/DC and the new energy storage device, various new energy such as photovoltaic energy, wind power energy and the like are converged through the direct current bus convergence mode, the isolated DC/DC converter is connected into a direct current link of the flexible traction transformer, and finally a single-phase traction power supply system is connected, so that various new energy is connected into the traction power supply system; the new energy storage device is used for transmitting power to a direct current link of the flexible traction transformer, meanwhile, the energy storage subsystem is arranged on a direct current bus to effectively inhibit energy fluctuation and intermittence of the new energy subsystem, and energy is reasonably stored through the energy storage subsystem under the condition that the new energy subsystem has energy surplus, so that 'wind and light abandonment' is reduced; the fluctuation energy of the new energy subsystem is stabilized through the energy storage subsystem, and then is connected into the traction network through the isolated DC/DC converter and the single-phase cascade inverter, so that the energy stability is greatly enhanced, and the new energy is connected into the traction network through the flexible traction transformer, which does not involve the transformation of the traction network and is easy for engineering realization; when the traction network generates regenerative braking energy, the regenerative braking energy can be stored and utilized by connecting the cascade rectifier (reverse of the cascade inverter) and the isolated DC/DC and energy storage converter into the energy storage subsystem.
Drawings
Fig. 1 is a new energy storage system dispersedly connected to a flexible traction transformer according to the present invention;
fig. 2 is a schematic circuit diagram of an isolated DC/DC converter based on a dual-level dual-active full bridge according to an embodiment of the present invention;
FIG. 3 is a flowchart illustrating steps of a method for controlling a new energy storage system discretely connected to a flexible traction transformer according to the present invention;
fig. 4 is a voltage and power control block diagram of an isolated DC/DC converter based on a two-level dual active full bridge according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.
The invention provides a new energy storage system with a distributed access flexible traction transformer and a control method;
as shown in fig. 1, in one aspect, a new energy storage system for decentralized access to a flexible traction transformer includes: the system comprises a flexible traction transformer, an isolated DC/DC converter, a direct current bus and a new energy storage device;
the flexible traction transformer is connected with the isolated DC/DC converter and is used for receiving energy of the isolated DC/DC converter;
preferably, the flexible traction transformer comprises a traction transformer, a multi-winding step-down transformer, an ac-dc-ac converter;
the traction transformer is connected with the multi-winding step-down transformer and used for receiving three-phase power grid voltage and carrying out energy-saving transformation;
the multi-winding step-down transformer is connected with the AC-DC-AC converter and used for receiving the transmission power of the traction transformer, reducing the transmission power, obtaining and transmitting the reduced power to the AC-DC-AC converter;
the alternating current-direct current-alternating current converter is connected with the isolation type DC/DC converter and is used for changing three-phase alternating current into single-phase alternating current by electric energy, and energy in the new energy storage device converged by the direct current bus is connected into a direct current link through the isolation type DC/DC converter and is supplied to a single-phase traction power supply network.
In practice, the input end of the flexible traction transformer is connected to the three-phase power grid, and the output end of the flexible traction transformer is connected to the single-phase traction power supply network system, and the single-phase traction power supply network system is used for receiving the output voltage of the flexible traction transformer and supplying power to the external load.
Preferably, the ac-dc-ac converter comprises a three-phase rectifier, a single-phase cascade inverter;
the three-phase rectifier is respectively connected with the multi-winding step-down transformer, the single-phase inverter and the isolated DC/DC converter and is used for rectifying three-phase alternating current output by the multi-winding step-down transformer into direct current;
the single-phase inverter is connected with the isolation type DC/DC converter and used for realizing the bidirectional flow of energy in the single-phase cascade inverter.
Optionally, the energy of the single-phase cascaded inverter can flow in two directions, works reversely as a cascaded rectifier, and inputs direct-current electric energy to the direct-current link.
Preferably, the single-phase-stage inverter comprises a plurality of cascade modules, each cascade module is externally provided with a bypass switch, and the number of the cascade modules is the same as that of the isolated DC/DC converters.
Optionally, in the emergency redundancy strategy of the single-phase cascade inverter, the cascade module is switched in or out by adding the bypass switches S1 and S2 … … Sn at the output end of the single cascade module, and when the bypass switch Sx is disconnected, the cascade module x is switched in operation; when the bypass switch Sx is closed, the cascade module x is bypassed and switched out of the single-phase cascade inversion system, and the bypass switch Sx defines two states: sx =1, closed; sx =0, open, wherein: x is more than or equal to 1 and less than or equal to n. When the single-phase cascade inverter normally operates, the m cascade modules are in a working state, the p cascade modules are in a standby state, and the single-phase inverter in the emergency redundancy strategy can realize the fault operation under the fault of the p cascade modules;
the redundant standby module is also connected to the direct-current bus through the isolated DC/DC converter, so that when some modules of the single-phase cascade inverter have faults (p module faults can be borne at most), after the standby module is put into use, the new energy access is not influenced, and the isolated DC/DC converter realizes the fault operation of the AC-DC-AC converter when the cascade modules in the single-phase cascade inverter have faults;
similarly, in order to realize emergency redundancy control by matching with a single-phase cascade inverter, n isolated DC/DC converter enable signals are defined as G1, G2 … … Gn, and Gx has two states: gx =1, the isolated DC/DC converter _ ISx operates; gx =0, the isolated DC/DC converter _ ISx stops working, and the state of the enabling signal Gx and the state of the bypass switch Sx are inverted
Therefore, when the cascade module x stops working due to failure or standby, the corresponding isolated DC/DC converter _ ISx also stops working correspondingly.
Preferably, the cascade module comprises a plurality of normal operation modules and a plurality of redundant standby modules, wherein the maximum accessible new energy capacity calculation formula of the flexible traction transformer is represented as:
Pc1+Pc2+……+Pcm＝m*Pc
pcm is the capacity of the cascade modules in the mth single-phase cascade inverter, m is the number of the cascade modules in normal operation, and Pc is the capacity value of a single cascade module and meets the requirements of Pc1= Pc2= … … = Pcm = Pc.
The isolated DC/DC converter is respectively connected with the flexible traction transformer and the direct current bus and is used for adjusting the direct current voltage of the flexible traction transformer and bidirectionally and controllably adjusting the transmitted energy;
optionally, the design capacity of the isolated DC/DC converter may also consider the capacities of the plurality of redundant standby modules, so the capacity of the isolated DC/DC converter may be expressed as: pc1+ Pc2+ … … + Pcn = n × Pc, where n is the total number of single-phase cascade inverter modules and satisfies m + p = n, where p is the number of redundant standby modules.
Optionally, the isolated DC/DC converters appear in pairs at access points of each cascade module between the three-phase rectifier and the single-phase cascade inverter, and are sequentially U1P, U1N, U P, U2N … UnP and UnN; unP and UnN are connected to the three phase rectifier Rn module output RnP and RnN of the nth single phase cascaded inverter and the input CnP and CnN of the single phase cascaded inverter Cn module, respectively.
Optionally, the positive output IS1+ of the isolated DC/DC converter IS connected to the middle connection point UnP between the three-phase rectifier Rn module and the single-phase cascade inverter Cn module, and the negative output IS 1-of the isolated DC/DC converter IS connected to the middle connection point UnN between the three-phase rectifier Rn module and the single-phase cascade inverter _ Cn module.
Optionally, the isolated DC/DC converter includes, but is not limited to, topologies such as a dual-active full bridge and a full bridge resonant converter, and may be a two-level structure or a multi-level structure, as shown in fig. 2, in the embodiment of the present invention, a two-level dual-active full bridge based isolated DC/DC structure is adopted.
In practice, the isolated DC/DC converter is controlled to make the output voltage follow the DC link voltage, thereby ensuring the DC link voltage to be stable; when the cascade module in the single-phase inverter fails, the AC-DC-AC converter can operate after the fault occurs;
one end of the isolated DC/DC converter is connected to a direct current link in an AC-DC-AC converter in the flexible traction transformer, namely between the three-phase rectifier and the single-phase cascade inverter, and the other end of the isolated DC/DC converter is connected with a direct current bus.
The direct current bus is connected with the new energy storage device and used as an energy convergence bus for receiving the power transmitted by the new energy storage device and transmitting the power to the isolated DC/DC converter; the energy storage device is used for supplying power to the flexible traction transformer and the isolated DC/DC converter;
and the new energy storage device is used for supplying power to the flexible traction transformer and the isolated DC/DC converter and storing regenerative braking energy.
Preferably, the new energy storage device adopts a direct current mode networking and comprises a new energy subsystem and an energy storage subsystem;
the new energy subsystem is connected with the direct current bus, comprises a new energy converter and a new energy power generation module which are connected, and is used for receiving power transmitted by the new energy power generation module through the new energy converter and transmitting the power to a direct current link of the flexible traction transformer through the isolated DC/DC converter.
Optionally, the new energy power generation subsystem comprises other various new energy sources such as wind energy, photovoltaic energy, hydrogen energy and the like; and networking is performed in a direct current mode, electric energy is gathered to a direct current bus by photovoltaic through DC/DC conversion, wind energy through AC/DC conversion and other new energy through corresponding electric energy form conversion, and the generated energy and the generated power of the new energy are adjustable.
The energy storage subsystem is connected with the direct current bus, comprises a bidirectional DC/DC energy storage converter and an energy storage module which are connected and is used for absorbing or storing the fluctuating power of the direct current bus through the bidirectional DC/DC energy storage converter and inhibiting the power fluctuation of the new energy subsystem.
Optionally, the energy storage subsystem includes a plurality of energy storage media such as a super capacitor and a storage battery, and is connected to the DC bus through the bidirectional DC/DC energy storage converter, so that energy absorption/release to the DC bus can be rapidly realized.
Optionally, the energy generation subsystem is connected with the energy storage subsystem through a direct current bus, the energy storage subsystem can effectively stabilize the intermittence and fluctuation of new energy generation, wind and light abandonment is reduced, meanwhile, new energy is connected into a traction network through the isolation type DC/DC converter and the single-phase cascade inverter, and the fluctuation of the new energy does not affect the traction network; the new energy is connected to the traction network through the flexible traction transformer, the transformation of the traction network is not involved, and the engineering realization is easy.
As shown in fig. 3, in another aspect, a method for controlling a new energy storage system dispersedly connected to a flexible traction transformer is characterized by comprising the following steps:
s1, collecting voltage information of each port in a new energy storage system to calculate power of each port;
optionally, after comprehensive judgment is performed by detecting the power Pt of each traction network, the new energy power Pne and the state of charge SoC of the energy storage subsystem, control signals of the isolated DC/DC converter, the bidirectional DC/DC energy storage converter and the new energy power generation subsystem are given.
Preferably, step S1 is specifically:
and acquiring voltage information of each port in the new energy storage system to calculate traction network power, new energy subsystem power, energy storage subsystem charge state, isolated DC/DC converter power and three-phase power grid power, so as to obtain power of each port.
Optionally, as shown in fig. 1, the traction grid power Pt is the power of the traction grid in the single-phase traction supply network.
Optionally, the voltage of each port and the power of the new energy subsystem are calculated by obtaining the voltage and current information of each port in the new energy storage system, wherein when the traction network is under the load of the locomotive, the energy flow direction to the traction network is recorded as positive, when the traction network is under the braking of the locomotive, the energy returned to the flexible traction network transformer is recorded as negative, and the energy injected into the traction network by the three-phase power network is recorded as Pr, which represents the power of the three-phase power network; the isolated DC/DC converter power Pdc takes the power transmitted to a direct-current link as positive and the power absorbed from the direct-current link as negative, and meets the following requirements: pdc = Pess + Pne, where Pess is the energy storage subsystem power; the new energy subsystem takes the energy injected into the direct current bus as positive, and records the power of the new energy subsystem as Pne, so that the following requirements are met: pne = Ppv + Pw + Poth, ppv is photovoltaic power, pw is wind power, and Poth is other new energy power; the power Pess of the energy storage subsystem takes the energy injected into the direct current bus as positive and the energy absorbed from the direct current bus as negative, wherein the maximum charging/discharging power is expressed as +/-Pess _ max; the maximum value and the minimum value of the state of charge (SoC) of the energy storage system are represented as SoCmax and SoCmin, and in order to prevent the energy storage system from being damaged by over-charging and over-discharging, the energy storage system stops working when the SoC of the energy storage system is more than or equal to SoCmax or less than or equal to SoCmin.
S3, judging whether the power of the traction network is larger than the sum of the power of the new energy subsystem and the power of the energy storage subsystem, and if so, entering a step S4; otherwise, entering step S5;
s4, judging whether the charge state of the energy storage subsystem is larger than the minimum charge state of the energy storage subsystem, if so, enabling the new energy subsystem to be in a maximum power point tracking state, releasing energy by the energy storage subsystem, and complementing the difference power by a three-phase power grid, otherwise, enabling the new energy subsystem to be in the maximum power point tracking state, stopping the energy storage subsystem, and complementing the difference power by the three-phase power grid;
s5, judging whether the power of the new energy subsystem is larger than the power of a traction network, if so, entering a step S6, otherwise, keeping the new energy subsystem in a maximum power point tracking state, and complementing the difference power by the energy storage subsystem;
s6, judging whether the difference value between the power of the new energy subsystem and the power of the traction network is larger than the maximum charging power of the energy storage subsystem or not, if so, reducing the power of the new energy subsystem to generate power, and absorbing and storing energy by the energy storage subsystem; otherwise, the new energy subsystem is in a maximum power point tracking state, and the energy storage subsystem absorbs and stores energy;
optionally, the power Pt of the traction network is positive, and when the power Pt of the traction network is greater than the sum of the power of the new energy subsystem and the power of the energy storage subsystem, that is, pt is greater than Pne + Pess, the power Pt of the traction network is provided by the power Pr of the three-phase power grid and the power Pdc of the isolated DC/DC converter, and Pt = Pr + Pdc is satisfied, and the new energy transmitted by the isolated DC/DC is preferentially consumed, the power difference is complemented by the power of the three-phase power grid, and at this time, the new energy subsystem is in a maximum power generation state; if the charge quantity of the energy storage subsystem is larger than the minimum charge state of the energy storage subsystem, namely SoC is larger than SoCmin, the energy storage subsystem injects energy into the direct current bus to meet Pdc = Pess + Pne, and the three-phase power grid supplements power to meet Pr = Pt-Pess-Pne; otherwise, if the charge quantity of the energy storage subsystem is smaller than or equal to the minimum charge state of the energy storage subsystem, namely the SoC is smaller than or equal to SoCmin, the energy storage system stops working Pess =0, the power of the isolated DC/DC converter is equal to the power of the new energy subsystem, namely Pdc = Pne, the supplementary power of a three-phase power grid is satisfied, and Pr = Pt-Pne is satisfied;
when the power of the traction network is less than or equal to the sum of the power of the new energy subsystem and the power of the energy storage subsystem, namely Pt is less than or equal to Pne + Pess, the power of the new energy subsystem and the power of the traction network are required to be further judged, if Pne is less than or equal to Pt, the new energy subsystem is in an MPPT working state, namely a maximum power point tracking state, the energy storage subsystem complements the difference power, and power is injected into a direct current bus, so that the following conditions are met: pess = Pt-Pne; otherwise, pne is larger than Pt, whether the charge state of the energy storage system is higher than the maximum charge state of the energy storage subsystem or not needs to be further judged, if the charge state of the energy storage subsystem is higher than the maximum charge state of the energy storage subsystem, namely SoC is larger than or equal to SoCmax, the energy storage subsystem stops working at the moment, the new energy subsystem is in power reduction power generation, and Pne = Pt is met; otherwise, namely the state of charge of the energy storage subsystem is lower than the maximum state of charge of the energy storage subsystem, namely SoC is less than SoCmax, the difference value between the power Pne of the new energy subsystem and the power Pt of the traction network, namely Pne-Pt, is judged again, whether the difference value is greater than the maximum charging power Pess _ max of the energy storage subsystem or not is judged, if the difference value is greater than the maximum charging power Pne-Pt of the energy storage subsystem, the energy storage subsystem stores energy with the maximum charging power, the new energy subsystem reduces power to generate electricity, the maximum power point tracking state is met, namely the MPPT state is achieved, namely the maximum power point tracking state is achieved, the energy storage system absorbs and stores energy, and the Pess = Pne-Pt is met.
S7, judging whether the charge state of the energy storage subsystem is smaller than the maximum value of the charge state of the energy storage subsystem, if so, entering a step S8, otherwise, stopping power generation of the new energy subsystem, stopping the work of the energy storage subsystem and consuming regenerative braking energy;
s8, judging whether the power of the traction network is smaller than the maximum charging power of the energy storage subsystem or not, if so, absorbing and storing surplus energy by the energy storage subsystem, and reducing power generation by the new energy subsystem; otherwise, the energy storage subsystem absorbs and stores the surplus energy, the new energy subsystem stops generating electricity, and part of regenerative braking energy is consumed.
Optionally, when the power Pt of the traction network is negative, the traction network is in a state that the locomotive brakes and returns energy to the flexible traction transformer, the power Pt of the traction network reversely works in a mode of a cascade rectifier through a single-phase cascade inverter and transmits the energy to a direct current link, and since an electric power department does not allow the energy to be returned to the power grid from the traction power supply system, at this time, pr =0. If the charge state of the energy storage subsystem is smaller than the maximum charge state of the energy storage subsystem, the method is as follows: and if the SoC is less than the SoCmax, further judging to regenerate the braking energy power, and meeting the relationship between the traction network power Pt and the maximum charging power Pess _ max of the energy storage subsystem at the moment: (1) when Pt is larger than Pess _ max, the energy storage subsystem can not completely store regenerative braking energy, and the energy storage subsystem stores power with the maximum charging power Pess _ max at the moment, consumes the power which can not be stored, and meets the following requirements: pt-Pess _ max, stopping power generation of the new energy subsystem; (2) when Pt is less than or equal to Pess _ max, the energy storage subsystem stores energy, and the new energy subsystem reduces power to generate electricity;
otherwise, namely when the state of charge of the energy storage subsystem is higher than the maximum state of charge of the energy storage subsystem, the SoC is more than or equal to the SoCmax, the energy storage subsystem stops working and cannot store regenerative braking energy, and the new energy subsystem stops generating electricity.
Preferably, when a cascade module in the single-phase inverter fails, the isolated DC/DC converter adopts an emergency redundancy strategy;
the emergency redundancy strategy specifically comprises the following steps:
the method comprises the steps that a bypass switch is arranged outside each cascade module in a single-phase inverter, when an enabling signal of each cascade module in the single-phase inverter is defined to be a low level, the single-phase inverter normally works, the enabling signal of each cascade module in the single-phase inverter is defined to be a high level, the single-phase inverter stops working, the enabling signal of each cascade module in the single-phase inverter is inverted to the signal state of an isolation type DC/DC converter, and when the cascade module breaks down, the enabling signal corresponding to the fault module is a high level, and the fault module stops working; meanwhile, in order to ensure the normal work of the single-phase inverter, required power is supplied to the direct current link corresponding to the fault module through the new energy subsystem and the energy storage subsystem, when the cascade module in the single-phase inverter stops working due to a fault, the isolation type DC/DC converter corresponding to the cascade module stops working, and the redundancy standby modules with corresponding quantity are started, wherein the power of the isolation type DC/DC converter corresponding to the redundancy standby modules is expressed as:
P_ISx＝Pt/m
p _ ISx is the power of the xth isolated DC/DC converter, pt is the power of a traction network, and m is the number of normally-operated isolated DC/DC converters.
Preferably, the power control of each isolated DC/DC converter is independent, and the voltage of the direct current side of the corresponding cascade module in the single-phase inverter is adjusted to follow the voltage of the new energy storage system, so that the power balance of the cascade module is realized; and when the power of the traction network is larger than zero, each isolated DC/DC converter equally divides the power of the new energy subsystem and the power of the energy storage subsystem transmitted by the direct current bus.
Optionally, the power control of the isolated DC/DC converter is independent, and has a function of adjusting the voltage of the direct-current link of the flexible traction transformer, so that the direct-current side voltages Upn1, upn2, … … Upnn of each cascade module all follow the preset reference value Upn _ ref of the system, thereby ensuring the power balance of each module of the cascade inverter; when the power Pt of the traction network IS larger than 0, the isolation type DC/DC converters divide new energy and stored energy power on the direct current bus equally, and the power transmitted to the direct current link IS P _ IS1= P _ IS2= … … = P _ ISn = Pdc/n = (Pne + Pess)/n respectively.
Optionally, energy of the new energy and energy storage subsystem is preferentially consumed, energy of the three-phase power grid is used as a relaxation port, power shortage is automatically supplemented, the new energy is preferentially supplied to the traction grid for consumption, and when the energy of the new energy system is greater than load power of the traction grid, surplus energy is stored by the energy storage subsystem.
Optionally, as shown in fig. 4, an isolated DC/DC converter with a two-level dual-active full bridge is used for voltage and power control, the control adopts single-phase-shift control, and the power expression under the single-phase-shift control is as follows:
wherein, P is power under single phase-shift control, D is primary-secondary side transformation ratio of the high-frequency transformer, udc is direct-current bus voltage, upn is intermediate direct-current link of the alternating-direct-current alternating-current converter, fs is high-frequency transformer frequency, L is double-active full-bridge inductor, and D is phase-shift ratio;
it can be seen that the estimated phase shift calculation at the reference voltage and power is expressed as:
wherein D is an estimated phase shift of a known parameter, and the difference Delta D between D and the actual phase shift is compensated by the PI controller;
the method has the advantages that the voltage of a direct current link is stabilized, meanwhile, power is transmitted according to needs, so that the prior consumption of new energy and the fault operation of an alternating current-direct current converter when a certain cascade module rectifier has a fault are realized, the control analysis of the isolated DC/DC converter with the two-level double-active full bridge under the single phase-shift control is performed, and the characteristics of voltage stabilization and power control are also met if isolated DC/DC converters or control methods with other structures are adopted.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The principle and the implementation mode of the invention are explained by applying specific embodiments in the invention, and the description of the embodiments is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (5)
1. The utility model provides a new forms of energy storage system of flexible traction transformer of distributed access which characterized in that includes: the system comprises a flexible traction transformer, an isolated DC/DC converter, a direct current bus and a new energy storage device;
the flexible traction transformer is connected with the isolated DC/DC converter and is used for receiving energy of the isolated DC/DC converter;
the isolated DC/DC converter is respectively connected with the flexible traction transformer and the direct current bus and is used for adjusting the direct current voltage of the flexible traction transformer and bidirectionally and controllably adjusting the transmitted energy;
the direct current bus is respectively connected with the isolated DC/DC converter and the new energy storage device, is used as an energy convergence bus and is used for connecting the isolated DC/DC converter and the new energy storage device;
the new energy storage device is used for supplying power to the flexible traction transformer and the isolated DC/DC converter and storing regenerative braking energy;
the flexible traction transformer comprises a traction transformer, a multi-winding step-down transformer and an AC-DC-AC converter;
the traction transformer is connected with the multi-winding step-down and used for receiving and transforming three-phase power grid voltage;
the multi-winding step-down transformer is connected with the AC-DC-AC converter and used for receiving the transmitted power of the traction transformer, reducing the transmitted power, obtaining and transmitting the reduced power to the AC-DC-AC converter;
the alternating current-direct current-alternating current converter is connected with the isolation type DC/DC converter and is used for changing three-phase alternating current into single-phase alternating current by electric energy, and energy in a new energy storage device converged by a direct current bus is connected into a direct current link through the isolation type DC/DC converter and is supplied to a single-phase traction power supply network;
the AC-DC-AC converter comprises a three-phase rectifier and a single-phase cascade inverter;
the three-phase rectifier is respectively connected with the multi-winding step-down transformer, the single-phase inverter and the isolated DC/DC converter and is used for rectifying three-phase alternating current output by the multi-winding step-down transformer into direct current;
the single-phase inverter is connected with the isolated DC/DC converter and is used for realizing the bidirectional flow of energy in the single-phase cascade inverter;
the new energy storage device adopts a direct current mode to form a network and comprises a new energy subsystem and an energy storage subsystem;
the new energy subsystem is connected with the direct current bus, comprises a new energy converter and a new energy power generation module which are connected, and is used for receiving the power transmitted by the new energy power generation module through the new energy converter and transmitting the power to a direct current link of the flexible traction transformer through the isolated DC/DC converter;
the energy storage subsystem is connected with the direct current bus, comprises a bidirectional DC/DC energy storage converter and an energy storage module which are connected and is used for absorbing or storing the fluctuating power of the direct current bus through the bidirectional DC/DC energy storage converter and inhibiting the power fluctuation of the new energy subsystem;
the single-phase inverter comprises a plurality of cascade modules, bypass switches are arranged outside the cascade modules, the number of the cascade modules is the same as that of the isolated DC/DC converters, power control of the isolated DC/DC converters is independent, and the single-phase inverter is used for adjusting the voltage of the direct current side of the corresponding cascade module in the single-phase inverter to follow the voltage of the new energy storage system.
2. The new energy storage system with decentralized access to flexible traction transformer according to claim 1, wherein said cascade module comprises a plurality of normal operation modules and a plurality of redundant standby modules, and wherein the calculation formula of the maximum accessible new energy capacity of the flexible traction transformer is:
Pc1+Pc2+……+Pcm=m*Pc
pcm is the capacity of the cascade modules in the mth single-phase cascade inverter, m is the number of the cascade modules in normal operation, and Pc is the capacity value of a single cascade module and meets the requirements of Pc1= Pc2= … … = Pcm = Pc.
3. The control method of the new energy storage system dispersedly connected to the flexible traction transformer according to claim 1 or 2, characterized by comprising the following sub-steps:
s1, collecting voltage information of each port in a new energy storage system to calculate power of each port;
s2, judging whether the single-phase traction power supply network is in a load state at present according to the power of the traction network in the power of each port, if so, recording that the energy inflow of the single-phase traction power supply network is positive, and entering the step S3; otherwise, recording that the energy returned to the flexible traction transformer is negative, and entering the step S7;
s3, judging whether the power of the traction network is larger than the sum of the power of the new energy subsystem and the power of the energy storage subsystem, and if so, entering a step S4; otherwise, entering step S5;
s4, judging whether the charge state of the energy storage subsystem is larger than the minimum charge state of the energy storage subsystem, if so, enabling the new energy subsystem to be in a maximum power point tracking state, releasing energy by the energy storage subsystem, and complementing the difference power by a three-phase power grid, otherwise, enabling the new energy subsystem to be in the maximum power point tracking state, stopping the energy storage subsystem, and complementing the difference power by the three-phase power grid;
s5, judging whether the power of the new energy subsystem is larger than the power of a traction network, if so, entering a step S6, otherwise, keeping the new energy subsystem in a maximum power point tracking state, and complementing the difference power by the energy storage subsystem;
s6, judging whether the difference value between the power of the new energy subsystem and the power of the traction network is larger than the maximum charging power of the energy storage subsystem or not, if so, reducing the power of the new energy subsystem to generate power, and absorbing and storing energy by the energy storage subsystem; otherwise, the new energy subsystem is in a maximum power point tracking state, and the energy storage subsystem absorbs and stores energy;
s7, judging whether the charge state of the energy storage subsystem is smaller than the maximum value of the charge state of the energy storage subsystem, if so, entering a step S8, otherwise, stopping power generation of the new energy subsystem, stopping the work of the energy storage subsystem and consuming regenerative braking energy;
s8, judging whether the power of the traction network is smaller than the maximum charging power of the energy storage subsystem or not, if so, absorbing and storing surplus energy by the energy storage subsystem, and reducing power generation by the new energy subsystem; otherwise, the energy storage subsystem absorbs and stores surplus energy, the new energy subsystem stops generating electricity, and part of regenerative braking energy is consumed;
when a cascade module in a single-phase inverter fails, an emergency redundancy strategy is adopted by the isolated DC/DC converter;
the emergency redundancy strategy specifically comprises the following steps:
the method comprises the steps that a bypass switch is arranged outside each cascade module in a single-phase inverter, when an enabling signal of each cascade module in the single-phase inverter is defined to be a low level, the single-phase inverter normally works, the enabling signal of each cascade module in the single-phase inverter is defined to be a high level, the single-phase inverter stops working, the enabling signal of each cascade module in the single-phase inverter is inverted to the signal state of an isolation type DC/DC converter, and when the cascade module breaks down, the enabling signal corresponding to the fault module is a high level, and the fault module stops working; meanwhile, in order to ensure the normal work of the single-phase inverter, required power is supplied to the direct current link corresponding to the fault module through the new energy subsystem and the energy storage subsystem, when the cascade module in the single-phase inverter stops working due to a fault, the isolation type DC/DC converter corresponding to the cascade module stops working, and the redundancy standby modules with corresponding quantity are started, wherein the power of the isolation type DC/DC converter corresponding to the redundancy standby modules is expressed as:
P_ISx=Pt/m
wherein,P_ISxis as followsxThe power of the isolated DC/DC converter,Ptin order to pull the power of the net,mthe number of isolated DC/DC converters that are operating normally.
4. The control method according to claim 3, wherein step S1 is specifically:
and acquiring voltage information of each port in the new energy storage system to calculate traction network power, new energy subsystem power, energy storage subsystem charge state, isolated DC/DC converter power and three-phase power grid power, so as to obtain power of each port.
5. The control method according to claim 3, wherein power control among the isolated DC/DC converters is independent, and the direct-current side voltage of the corresponding cascade module in the single-phase inverter is adjusted to follow the voltage of the new energy storage system, so that power balance of the cascade module is realized; and when the power of the traction network is larger than zero, each isolated DC/DC converter equally divides the power of the new energy subsystem and the power of the energy storage subsystem transmitted by the direct current bus.
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| CN102355154B (en) * | 2011-09-19 | 2015-04-29 | 中电普瑞科技有限公司 | Protection method of cascaded converter |
| CN103434421B (en) * | 2013-07-29 | 2015-10-21 | 华北电力大学（保定） | A kind of mixing inter-act DC traction power-supply system based on new forms of energy |
| CN104410095B (en) * | 2014-03-21 | 2015-11-18 | 南车株洲电力机车研究所有限公司 | The same electric power system that connects of ac electrified railway based on multi-terminal HVDC transmission |
| CN107104461A (en) * | 2017-05-17 | 2017-08-29 | 阳光电源股份有限公司 | A kind of photovoltaic generating system |
| CN108336727B (en) * | 2018-01-23 | 2023-11-24 | 西南交通大学 | New energy supply system for through traction power supply and control method |
| CN109572491B (en) * | 2019-01-23 | 2023-11-24 | 西南交通大学 | Electrified railway traction network power supply structure and control method thereof |
| CN110190628B (en) * | 2019-06-12 | 2022-04-15 | 西南交通大学 | Complex line full-parallel AT traction power supply system and method based on comprehensive energy |
| CN110341728B (en) * | 2019-08-19 | 2024-01-26 | 西南交通大学 | Electrified railway through-type traction power supply system |
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2021
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