Distributed flexible direct current converter and energy storage converter universal controller and control method

Abstract

The utility model discloses a distributed flexible direct current converter and energy storage converter general controller and control method, including distributed flexible direct current converter and energy storage converter general controller, the distributed flexible direct current converter and energy storage converter general controller including common grid parameter conversion controller module, flexible direct current transmission controller module, the dynamic function controller module of energy storage system and flexible direct current storage selection controller module. Can realize the core algorithm control of two kinds of products of distributed flexible direct current converter and energy storage converter. And the control method for this, can realize the simultaneous application of distributed flexible direct current converter and energy storage converter, reduce the production and debugging cost, improve the stability of two series products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of converter controller, in particular to a universal controller and control method for distributed flexible DC converter and energy storage converter. BACKGROUND

[0002] Distributed power generation and energy storage technology can realize the intelligentization of power grid, and intelligent power grid is an inevitable choice for social and economic development. In order to realize the development, transmission and consumption of clean energy, the power grid must improve its flexibility and compatibility, continuously improve its security defense capability and self-healing capability, reduce operation cost, promote energy saving and emission reduction, and make the power grid operation more economic and efficient.

[0003] Through comparison between conventional DC power transmission and flexible DC power transmission, it is found that with the rapid development of DC power transmission technology and the requirements of energy saving and green energy, especially in the aspects of renewable energy power generation and island power supply, the future flexible DC power transmission represented by IGBT will become the mainstream of the market, and the flexible DC power transmission, especially the DC power transmission based on voltage source converter, will develop rapidly and coexist with or even exceed the conventional DC power transmission.

[0004] The communication between the converter stations of the conventional DC power transmission system must be carried out to transmit system parameters and carry out appropriate control.

[0005] The conventional DC power transmission needs to change the voltage polarity when changing the power direction, while the DC current polarity remains unchanged. When the power is reversed, the converter station needs to exit operation, change the control strategy, and needs to make real-time judgment on the switching of the filter and the reactive power compensation device.

[0006] The conventional DC power transmission requires that the receiving end AC system has sufficient short-circuit capacity, needs additional commutation capacity, and cannot send power to passive or weak networks.

[0007] The active and reactive power of the conventional DC power transmission cannot be independently controlled, the adjustment of reactive power needs special devices and additional costs, and the AC system or additional reactive power compensation devices need to provide the reactive power consumed by the converter station. SUMMARY

[0008] In order to solve the problems of the conventional DC power transmission compared with the flexible DC power transmission in some aspects, the present application provides a universal controller and control method for distributed flexible DC converter and energy storage converter.

[0009] The technical scheme of the present application is as follows:

[0010] The universal controller for distributed flexible DC converter and energy storage converter comprises:

[0011] The common grid parameter conversion controller module is used for abc / dq conversion of port three-phase voltage, three-phase current and voltage phase, and obtaining port voltage and current in dq coordinate system, and can also obtain reference voltage in static coordinate system through dq / abc inverse conversion of reference voltage in dq coordinate system;

[0012] The HVDC energy storage selection controller module is used for receiving total control information and current port signal, determining application environment during power-on initialization, and adopting corresponding algorithm logic according to the application environment to realize algorithm control on different application environments.

[0013] The HVDC transmission controller module is used for constituting a core algorithm controller of the distributed HVDC converter together with the common grid parameter conversion controller module and the HVDC energy storage selection controller module.

[0014] The dynamic function controller module of the energy storage system is used for constituting a core algorithm controller of the energy storage converter together with the common grid parameter conversion controller module and the HVDC energy storage selection controller module.

[0015] Further, the core algorithm controller of the distributed HVDC converter has a DC inner and outer loop control structure and a low voltage ride-through strategy, and can adjust active power flow while keeping voltage constant, and can adjust reactive power while keeping active power unchanged.

[0016] Further, the dynamic function controller module of the energy storage system can control dynamic change of the battery energy storage power station and diagnose and adjust charge and discharge control parameters of the battery energy storage system, that is, actively adjusts active and reactive output according to current grid conditions to stabilize the grid.

[0017] The control method of the common controller of the distributed HVDC converter and the energy storage converter includes the following steps:

[0018] Step S1, after the common grid parameter conversion controller module is powered on, first acquire the port state of the HVDC energy storage selection controller module, and receive EMS total control input information.

[0019] Step S2, real-time acquire preset parameters of the currently used grid and matching parameters of the application occasion.

[0020] Step S3, according to the port state, perform preset logic analysis, and detect whether the energy storage battery is connected in the system loop.

[0021] Step S4, when the application scenario preset parameter is a distributed flexible direct current converter without energy storage battery, the application scenario preset parameter is an energy storage converter with energy storage battery, and each preset parameter meets the power grid stability condition corresponding to the preset parameter, step S6 is executed; when the application scenario preset parameter is a distributed flexible direct current converter with energy storage battery, the application scenario preset parameter is an energy storage converter without energy storage battery, or when the preset parameter does not meet the power grid stability condition corresponding to the preset parameter, step S5 is executed;

[0022] Step S5, issuing a parameter error indication, executing step S2, and checking the preset parameter;

[0023] Step S6, using and combining the operation module and the port, when it is judged in step S4 that the application scenario is a distributed flexible direct current converter, the common power grid parameter conversion module is combined with the logic application of the flexible direct current transmission controller module, and the output control port is connected; at this time, the application scenario is a distributed flexible direct current converter; when it is judged in step S4 that the application scenario is an energy storage converter, the common power grid parameter conversion module is combined with the logic application of the dynamic function controller module of the energy storage system, and the output control port is connected; at this time, the application scenario is an energy storage converter; after the logic matching is completed, step S7 is executed;

[0024] Step S7, when the application scenario is a distributed flexible direct current converter, a flexible direct current transmission indication is loaded; when the application scenario is an energy storage converter, an energy storage system indication is loaded; after the loading is completed, step S8 is executed;

[0025] Step S8, after step S7 is executed, each preset parameter meets the application scenario, the power grid preset parameter is stable, the system initialization is completed, and the system is switched to a use state.

[0026] Further, in step S2, the d-axis reference current i'd and the q-axis reference current i'q are calculated according to the target active power Pref of the converter and the target reactive power Qref; the calculation formula is:

[0027]

[0028] Wherein, P and Q are the active power and the reactive power of the flexible direct current converter port respectively; GP(s) and GQ(s) are the transfer functions of the active power PI controller and the reactive power PI controller respectively.

[0029] As a preferred, in step S3, the detection of whether there is an energy storage battery is detected by a remote signaling instruction.

[0030] As a preferred, the preset parameter is set to one or more.

[0031] The application has the advantages that the application is a universal controller and control method for distributed flexible direct current converter and energy storage converter, can switch between the flexible direct current converter and the energy storage converter, and the switching process is different from the conventional mechanism, but is directly completed through the flexible energy storage selection controller module, can be automatically selected according to the actual situation, and therefore has the advantages of the two controllers.

[0032] The flexible direct current transmission has the following advantages:

[0033] When the power flow is reversed, the flexible direct current transmission system only needs to change the current direction, and does not need to rely on the ability of the alternating current system to maintain voltage and frequency stability;

[0034] No reactive power compensation is needed, and the converter itself can provide reactive power;

[0035] The active power and the reactive power of the flexible direct current transmission can be independently controlled;

[0036] The flexible direct current transmission itself can act as a static var generator to stabilize the alternating current bus voltage.

[0037] At the same time, the energy storage converter has fast response speed and high control accuracy, and its frequency modulation and peak regulation effect far exceeds all traditional rotating power generation equipment. BRIEF DESCRIPTION OF DRAWINGS

[0038] The scheme and advantages of the present application will become clear to those skilled in the art from the following detailed description of the preferred embodiments. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be limiting to the present application.

[0039] In the drawings:

[0040] Figure 1 It is a schematic diagram of the algorithm module combination of the present application;

[0041] Figure 2 It is an algorithm application diagram of the distributed flexible direct current converter of the present application;

[0042] Figure 3 It is an algorithm application diagram of the energy storage converter of the present application;

[0043] Figure 4 It is a schematic diagram of the application occasion determination process of the present application;

[0044] Figure 5 It is a schematic diagram of the energy network level distribution of the present application;

[0045] Figure 6 It is a schematic diagram of the flexible direct current converter control module structure of the present application;

[0046] The components represented by the respective reference numerals in the drawings are: DETAILED DESCRIPTION

[0047] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. It should be noted that these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. The present disclosure can be implemented in various forms and should not be limited by the embodiments described herein.

[0048] Example

[0049] like Figure 1 The general controller of the distributed flexible DC converter and energy storage converter shown includes:

[0050] The shared grid parameter conversion controller module is used to perform abc / dq transformation on the three-phase voltage, three-phase current and voltage phase of the port, and obtain the port voltage and current in the dq coordinate system. It can also perform a dq / abc inverse transformation on the reference voltage in the dq coordinate system to obtain the reference voltage in the stationary coordinate system;

[0051] The flexible DC energy storage selection controller module is used to receive master control information and current port signals, determine the application environment during power-on initialization, and adopt corresponding algorithm logic based on the application environment to achieve algorithm control for different application environments;

[0052] The flexible direct current transmission controller module is used to form the core algorithm controller of the distributed flexible direct current converter together with the common grid parameter conversion controller module and the flexible direct current energy storage selection controller module; Figure 2 shown.

[0053] The dynamic function controller module of the energy storage system is used to form the core algorithm controller of the energy storage converter together with the shared grid parameter conversion controller module and the flexible DC energy storage selection controller module, such as Figure 3 shown.

[0054] Further on the basis of the above structure, the core algorithm controller of the distributed flexible DC converter has a DC inner and outer loop control structure and a low voltage crossing strategy, which can adjust the active power flow while keeping the voltage constant; and adjust the reactive power while keeping the active power unchanged.

[0055] Furthermore, based on the above structure, the dynamic function controller module of the energy storage system can control the dynamic changes of the battery energy storage power station and diagnose and adjust the charge and discharge control parameters of the battery energy storage system, that is, actively adjust the active and reactive output according to the current grid conditions to stabilize the grid.

[0056] The conditions and principles for designing the common grid parameter conversion controller module are that: based on the analysis of the existing distributed flexible direct current converter and energy storage converter algorithm, the main application of the converter algorithm in the smart grid is the grid parameter operation, including grid control, PWM generation, three-two conversion, etc. The content of the chip's large algorithm is the same, accounting for about 80%. The same algorithm is set as common, and the algorithms of the distributed flexible direct current converter and the energy storage converter are combined together. The chip algorithm is also sufficient, and the general core algorithm controller can be realized.

[0057] The logical algorithm part of the distributed flexible direct current converter and the energy storage converter algorithm is separated out, which is the analysis of the grid parameters, the PWM operation of the grid connection main circuit IGBT, and the design of the common grid parameter conversion controller module for the same part of the distributed flexible direct current converter and the energy storage converter algorithm.

[0058] After the design of the common grid parameter conversion controller module, other modules need to be designed, and specifically:

[0059] The common grid parameter conversion controller module content in the algorithm of the distributed flexible direct current converter is removed, and the special algorithm applied to the flexible direct current converter is composed of a flexible direct current transmission controller module.

[0060] The common grid parameter conversion controller module content in the algorithm of the energy storage converter is removed, and the special algorithm applied to the energy storage converter is composed of a dynamic function controller module of the energy storage system.

[0061] The application of the distributed flexible direct current converter and the energy storage converter selects the design of the special logic algorithm, which is adapted to the application occasion and designed as a flexible energy storage selection controller module.

[0062] Finally, after completing the above structure design, the following effects can be obtained:

[0063] When it is determined to be a distributed flexible direct current converter application, the common grid parameter conversion controller and the flexible direct current transmission controller form a direct current inner and outer loop control structure and a low voltage ride through strategy function, realizing a kind of distributed flexible direct current converter.

[0064] When it is determined to be an energy storage converter application, the common grid parameter conversion controller and the dynamic function controller of the energy storage system form a dynamic change for the battery energy storage power station, diagnose and adjust the charge and discharge control parameters of the battery energy storage system, and realize the energy storage converter converter.

[0065] And in the above structure, the advantages of the distributed flexible direct current converter and the energy storage converter are as follows:

[0066] (1) Distributed flexible direct current converter:

[0067] It is not necessary to realize the communication between each converter station in the flexible HVDC system.

[0068] When the power flow is reversed, the flexible HVDC system only needs to change the current direction, while the DC voltage polarity remains unchanged, and the system does not shut down when the power is reversed, which makes the control strategy of the two-end converter stations unchanged when the flexible HVDC system changes the power direction, and there is no need to switch the AC filter or block the converter. However, when the power direction is changed in the conventional DC power transmission, the voltage polarity needs to be changed, while the DC current polarity remains unchanged, and when the power is reversed, the converter station needs to be taken out of operation, the control strategy needs to be changed, and the switching of the filter and the real-time judgment of the reactive power compensation device need to be made.

[0069] The flexible HVDC does not need to rely on the capacity of the AC system to maintain voltage and frequency stability, and does not need reactive power compensation, and the converter itself can provide reactive power. However, the conventional DC power transmission requires the receiving end AC system to have sufficient short-circuit capacity, and needs additional commutation capacity, and cannot send power to passive or weak networks.

[0070] The active and reactive power of the flexible HVDC can be independently controlled. The active and reactive power of the conventional DC power transmission cannot be independently controlled, and special devices and additional costs are needed to adjust the reactive power, and the AC system or additional reactive power compensation devices are needed to provide the reactive power consumed by the converter station.

[0071] The flexible HVDC itself can play the role of STATCOM to stabilize the AC bus voltage, while the conventional DC power transmission needs to rely on reactive power compensation devices to stabilize the AC bus voltage

[0072] (2) Energy storage converter

[0073] The battery energy storage power station can fully play the role of a power station, and due to its unparalleled response speed and control accuracy, its frequency regulation and peak shaving effect far exceeds all traditional rotating power generation equipment, and the modular design, flexible configuration, and distributed use of the battery energy storage power station make large-scale grid-connected application possible. At the same time, the battery energy storage power station can also be conveniently used as a controllable load.

[0074] From the above description of the device, it can be seen that the focus of the device is the switching of the distributed flexible DC converter and the energy storage converter, therefore, the control method of the present application is also disclosed, and the specific content is:

[0075] The control method of the distributed flexible DC converter and the energy storage converter universal controller includes the following steps:

[0076] Step S1, after the common grid parameter conversion controller module is powered on, first acquire the HVDC energy storage selection controller module port state, receive the EMS master control (main station platform or front end) input information, for example, HVDC controller, energy storage controller;

[0077] Step S2, real-time acquire one or more preset parameters (voltage, current, power, operation mode) of the currently used grid, the supporting parameters of the application occasion, the specific mode is:

[0078] According to the converter target active power Pref, target reactive power Qref, the d-axis reference current i'd and the q-axis reference current i'q are calculated, and the calculation formula is:

[0079]

[0080] Wherein, P, Q are the active power and the reactive power of the HVDC converter port respectively; GP(s), GQ(s) are the active power PI controller transfer function and the reactive power PI controller transfer function respectively;

[0081] Step S3, according to the port state, carry out preset logic analysis, detect whether the energy storage battery is connected in the system loop, judge whether the preset input information working state is met, if not, execute S5, and the above detection method whether there is energy storage battery is through the remote signaling instruction detection;

[0082] Step S4, when the application occasion preset parameter is distributed HVDC converter without energy storage battery, the application occasion preset parameter is energy storage converter with energy storage battery, and each preset parameter meets the grid stability condition corresponding to the preset parameter, execute step S6; when the application occasion preset parameter is distributed HVDC converter with energy storage battery, the application occasion preset parameter is energy storage converter without energy storage battery, or when the preset parameter does not meet the grid stability condition corresponding to the preset parameter, execute step S5;

[0083] Step S5, issue parameter error indication, execute step S2, and check the preset parameter;

[0084] Step S6, use combination of operation module and port, when step S4 judges that the application occasion is distributed HVDC converter, the common grid parameter conversion module and the HVDC transmission controller module are combined with the logic application, the output control port is connected, at this time, the application occasion is distributed HVDC converter; When step S4 judges that the application occasion is energy storage converter, the common grid parameter conversion module and the dynamic function controller module of the energy storage system are combined with the logic application, the output control port is connected, at this time, the application occasion is energy storage converter; When the logic matching is completed, execute step S7;

[0085] Step S7, when the application scenario is a distributed flexible direct current converter, load the flexible power transmission instruction; when the application scenario is an energy storage converter, load the energy storage system instruction; after loading is completed, execute step S8;

[0086] Step S8, after step S7 is executed, each preset parameter meets the application scenario, the grid preset parameter is stable, the system initialization is completed, and the system is switched to a use state.

[0087] As shown in Figure 5 , for example:

[0088] The common grid parameter conversion controller and the flexible power transmission controller form a direct current inner and outer ring control structure and a low voltage ride through strategy function, and realize the distributed flexible direct current converter of the flexible direct current unit.

[0089] The distributed flexible direct current converter can be distributed in the entire direct current energy grid, and its function depends on its position and level in the energy network.

[0090] The backbone network layer distributed flexible direct current converter is mainly distributed on the energy supply side and bears the function of integrating different characteristic energy flows;

[0091] The distribution network layer distributed flexible direct current converter mainly bears the energy interaction function between the distribution network and the backbone network.

[0092] The microgrid layer distributed flexible direct current converter is the power management center of the microgrid and realizes the access of various users and devices.

[0093] The pre-obtained three-phase voltage, three-phase current and voltage phase of the flexible direct current converter port are subjected to abc / dq conversion to obtain the port voltage and current in the dq coordinate system; the pre-obtained target active power and target reactive power of the flexible direct current converter port are calculated to obtain the reference current in the dq coordinate system; the port voltage and current in the dq coordinate system and the reference current in the dq axis are subjected to current inner loop calculation to obtain the reference voltage in the dq coordinate system; the reference voltage in the dq coordinate system is subjected to dq / abc inverse conversion to obtain the reference voltage in the stationary coordinate system; the three-phase reference voltage subjected to dq / abc conversion after the stationary coordinate system is converted into 6 groups of PWM control of the full-bridge IGBT loop according to the reference voltage, and the flexible direct current converter is controlled.

[0094] The converter control module includes a power outer loop, a current inner loop, and an abc / dq conversion link, and the specific control composition is shown in the figure. The input signals of the power outer loop controller PIP include the active power given value Pref, the reactive power given value Qref, the active power measurement value P, and the reactive power measurement value Q. The output of the power outer loop controller PIP is used as the input of the current inner loop controller PIc. The input of the current inner loop controller PIc also includes the current d-axis component measurement value Ird and the q-axis component measurement value Irq.

[0095] Furthermore, when the power flow is reversed, the flexible DC power transmission system only needs to change the current direction, while the DC voltage polarity remains unchanged, and the system does not stop operating when the power is reversed, which makes the control strategy of the two-end converter station unchanged when the power direction of the flexible DC power transmission system is changed, and there is no need to switch the AC filter or block the converter. It does not need to rely on the ability of the AC system to maintain voltage and frequency stability, and does not need reactive power compensation, and the converter itself can provide reactive power. The active and reactive power of the flexible DC power transmission can be independently controlled. The flexible DC power transmission itself can act as a static var generator to stabilize the AC bus voltage.

[0096] The common grid parameter conversion controller and the dynamic function controller of the energy storage system constitute a dynamic change for the battery energy storage power station, diagnose and adjust the charge and discharge control parameters of the battery energy storage system, and realize the energy storage converter.

[0097] The pre-obtained three-phase voltage, three-phase current and voltage phase of the energy storage converter port are subjected to abc / dq conversion to obtain the port voltage and current in the dq coordinate system; the pre-obtained target active power and target reactive power of the HVDC converter port are calculated to obtain the reference current in the dq coordinate system; the port voltage and current in the dq coordinate system and the reference current in the dq axis are subjected to current inner loop calculation to obtain the reference voltage in the dq coordinate system; the reference voltage in the dq coordinate system is subjected to dq / abc inverse conversion to obtain the reference voltage in the stationary coordinate system; the three-phase reference voltage subjected to dq / abc conversion is converted into 6 groups of PWM control of the full-bridge IGBT loop according to the reference voltage in the stationary coordinate system. The energy storage converter control is realized.

[0098] Each energy storage battery module is connected in cascade through a corresponding switch module, and each energy storage battery module is connected in this way to form a complete battery pack. Through voltage detection of each energy storage battery module and control strategies of each IGBT switch, dynamic current sharing control, i.e., balancing control, of the battery pack during charging and discharging is realized. During normal operation of the energy storage converter, voltage of each energy storage battery module needs to be detected by a corresponding voltage detection device and the average voltage is calculated before balancing control during charging or discharging. The overall implementation process of balancing control includes the following: when the voltage of a certain energy storage battery module is greater than the average voltage and the error between the voltage of the energy storage battery module and the average voltage is greater than a first set error value, it is determined whether the energy storage converter is working in a charging state, and if the energy storage converter is working in the charging state, charging balancing control strategies are performed. The battery energy storage power station can fully play the role of a power station; and due to its incomparable response speed and control accuracy, its frequency modulation and peak shaving effect far exceeds that of all traditional rotating power generation equipment; and the modular design, flexible configuration and distributed use of the battery energy storage power station make large-scale grid-connected application possible. At the same time, the battery energy storage power station can also be used as a controllable load, that is, the battery energy storage power station has both power supply and load characteristics, and can instantaneously switch roles as needed.

Claims

1. A control method for a universal controller of a distributed flexible DC converter and an energy storage converter, characterized in that: The following steps are involved: Step S1: After the common grid parameter conversion controller module is powered on, it first obtains the port status of the flexible DC energy storage selection controller module and receives the EMS master control input information; Step S2: The common grid parameter conversion controller module obtains the preset parameters of the currently used grid and the supporting parameters of the application in real time; Step S3: Perform preset logic analysis based on the port status to detect whether an energy storage battery is connected to the system loop; Step S4: Determine whether the preset parameter for the application scenario is a distributed flexible DC converter without an energy storage battery, or whether the preset parameter for the application scenario is an energy storage converter with an energy storage battery. If each preset parameter satisfies the grid stability condition corresponding to the preset parameter, then execute step S6. If the preset parameter for the application scenario is a distributed flexible DC converter with an energy storage battery, or whether the preset parameter for the application scenario is an energy storage converter without an energy storage battery, or if the preset parameter does not satisfy the grid stability condition corresponding to the preset parameter, then execute step S5. Step S5: Issue a parameter error indication, execute step S2, and check the preset parameters; Step S6: Combine the operation modules and ports. When step S4 determines that the application scenario is a distributed flexible DC converter, the shared grid parameter conversion module and the flexible DC transmission controller module are logically combined and applied to connect the output control port. In this case, the application scenario is a distributed flexible DC converter. When step S4 determines that the application scenario is an energy storage converter, the shared grid parameter conversion module and the dynamic function controller module of the energy storage system are logically combined and applied to connect the output control port. In this case, the application scenario is an energy storage converter. After the logic matching is completed, step S7 is executed. Step S7: When the application scenario is a distributed flexible DC converter, the flexible DC transmission instruction is loaded; when the application scenario is an energy storage converter, the energy storage system instruction is loaded; when the loading is completed, step S8 is executed; Step S8: After step S7 is executed, each preset parameter meets the application scenario, the preset parameters of the power grid are stable, the system initialization is completed, and it is turned into the use state.

2. The control method of the universal controller of the distributed flexible DC converter and energy storage converter according to claim 1, characterized in that: In step S2, the d-axis reference current i′d and the q-axis reference current i′q are calculated according to the target active power Pref and the target reactive power Qref of the converter; The calculation formula is: Among them, P and Q are the active power and reactive power at the flexible DC converter port, respectively; GP(s) and GQ(s) are the active power PI controller transfer function and the reactive power PI controller transfer function, respectively.

3. The control method of the universal controller of the distributed flexible DC converter and energy storage converter according to claim 1, characterized in that: In step S3, the method of detecting whether there is an energy storage battery is through remote signaling command detection.

4. The control method of the universal controller of the distributed flexible DC converter and energy storage converter according to claim 1, characterized in that: The preset parameter is set to one or more.

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