Power balancing method, device, computer equipment and storage medium for power system

Abstract

The present application discloses a method, device, computer equipment and storage medium for power balancing of an electric power system. The electric power system includes a flexible direct current transmission electronic system and an MMC-BESS subsystem, and the method includes: determining the working mode of the electric power system, switching the electric power system to the corresponding working mode, and performing power balancing according to a preset power balancing strategy corresponding to the working mode. The above method realizes the flexible switching of multiple working modes of the electric power system, and performs power balancing according to the preset power balancing strategy corresponding to each working mode, thereby realizing power balancing under multiple working modes and improving the flexibility of power balancing regulation.

Description

Power balancing method, device, computer equipment and storage medium for power system Technical Field

[0001] The present application relates to the field of power system energy storage technology, and in particular to a power balancing method, apparatus, computer equipment, storage medium, and computer program product for a power system. Background Art

[0002] Building a new power system dominated by renewable energy is an important support for achieving the goals of carbon peak and carbon neutrality. Therefore, ensuring the safety, controllability, flexibility and efficiency of this new power system is becoming increasingly important.

[0003] At present, due to the strong randomness, volatility and intermittency inherent in renewable energy power generation, after large-scale distributed energy is connected to the power grid, the requirements of BMS (Battery Management System) for battery management control capabilities are gradually increasing. All of the above factors make the operation and regulation of the distribution network face the coupling influence of multiple uncertain factors. Therefore, due to the poor operation and regulation of the distribution network, the three-phase power of the power system is often unbalanced, and the power quality and power supply reliability of the power system cannot be effectively guaranteed.

[0004] Therefore, it is necessary to provide a solution that can solve the power imbalance of the power system and ensure the power quality and power supply reliability of the power system.

[0005] Summary of the Invention

[0006] In view of the above problems, the present application provides a power balancing method, device, computer equipment, computer-readable storage medium and computer program product for an electric power system, which can achieve power balancing of the electric power system, improve the flexibility of power balancing regulation, and ensure the power quality and power supply reliability of the electric power system.

[0007] In a first aspect, the present application provides a power balancing method for an electric power system, wherein the electric power system includes a flexible direct current transmission electronic system and an MMC-BESS (Modular Multilevel Converter based Battery Energy Storage System -MMC-BESS, a battery energy storage system based on a modular multilevel converter) subsystem;

[0008] Power balancing methods for power systems include:

[0009] Determine the operating mode of the power system;

[0010] Switch the power system to the corresponding working mode;

[0011] Power balancing is performed according to a preset power balancing strategy corresponding to the operating mode.

[0012] The technical solution of the embodiment of the present application provides a power balancing solution for a power system including a flexible direct current transmission subsystem and an MMC-BESS subsystem. Specifically, after determining the operating mode of the power system, the power system can be switched to the corresponding operating mode, thereby achieving flexible switching of multiple operating modes of the power system. In addition, power balancing is performed according to a preset power balancing strategy corresponding to each operating mode, thereby achieving power balancing of multiple operating modes such as a flexible direct current transmission mode or a flexible direct current transmission energy storage mode, thereby achieving power balancing for a power system that meets multiple operating scenarios. While achieving power balancing of the power system, the flexibility of power balancing regulation is also improved, thereby improving the power system's ability to absorb and regulate power, and ensuring the power quality and power supply reliability of the power system.

[0013] In some embodiments, determining the operating mode of the power system includes:

[0014] Obtain fault monitoring data of the flexible direct current transmission subsystem and the MMC-BESS subsystem;

[0015] Determine the operating mode of the power system based on fault monitoring data.

[0016] In the technical solution of the embodiment of the present application, by obtaining the fault monitoring data of the flexible direct current electronic system and the MMC-BESS subsystem and determining the working mode, abnormal situations can be discovered in time, power support can be avoided in the event of a fault, affecting the efficiency of power support, and ensuring the normal operation of the power system.

[0017] In some embodiments, the operating mode includes a flexible direct current transmission mode, a flexible direct current transmission and battery energy storage mode, or a cascaded H-bridge energy storage mode;

[0018] Based on fault monitoring data, the working mode of the power system is determined to include:

[0019] If the fault monitoring data indicates that the flexible direct current transmission electronic system has failed, the operating mode is determined to be the cascaded H-bridge energy storage mode;

[0020] If the MMC-BESS subsystem is determined to have a fault based on the fault monitoring data, the operating mode is determined to be the flexible direct current transmission mode;

[0021] If it is determined based on the fault monitoring data that neither the flexible direct current transmission subsystem nor the MMC-BESS subsystem has any faults, the operating mode is determined to be the flexible direct current transmission and battery energy storage power mode.

[0022] The technical solution of the embodiment of the present application provides multiple working modes. Fault monitoring data is used to determine whether the flexible direct current transmission electronic system and the MMC-BESS subsystem have faults. Then, according to the fault conditions of the above two subsystems, the corresponding working mode is selected in a targeted manner to ensure safe and accurate power balancing.

[0023] In some embodiments, the operating mode includes a flexible direct current transmission mode, a flexible direct current transmission and battery energy storage mode, or a cascaded H-bridge energy storage mode;

[0024] Switching the power system to the corresponding operating mode includes:

[0025] According to the preset mode switching strategy corresponding to the determined working mode, the battery module and flexible direct current transmission electronic system of the MMC-BESS subsystem are switched on and off to switch the power system to the corresponding working mode.

[0026] In the technical solution of the embodiment of the present application, the battery module and the flexible direct current transmission electronic system of the MMC-BESS subsystem are switched on and off according to the preset mode switching strategy corresponding to the working mode, thereby simply and efficiently realizing the switching of multiple working modes of the power system and improving the flexibility of mode switching.

[0027] In some embodiments, according to a preset mode switching strategy corresponding to the determined operating mode, switching control of the battery module of the MMC-BESS subsystem and the flexible direct current transmission subsystem to switch the power system to the corresponding operating mode includes:

[0028] If the working mode is flexible direct current transmission mode, the battery module of the MMC-BESS subsystem is turned off to switch the power system to flexible direct current transmission mode;

[0029] Alternatively, if the operating mode is flexible direct current transmission and battery energy storage mode, the battery status of the battery modules of the MMC-BESS subsystem is monitored, abnormal battery modules and normal battery modules are screened out, the abnormal battery modules are shut down, and the normal battery modules are powered on and off to switch the power system to flexible direct current transmission and battery energy storage mode;

[0030] Alternatively, if the operating mode is the cascade H-bridge energy storage mode, the loop of the flexible direct current electronic system is disconnected to switch the power system to the cascade H-bridge energy storage mode.

[0031] In the technical solution of the embodiment of the present application, the status of the battery modules is monitored to screen out abnormalities, and the battery module switches are controlled to shut down the battery modules with problems, thereby avoiding the adverse effects of abnormal battery modules on the power system and realizing multi-mode switching of the power system.

[0032] In some embodiments, if a battery module of the MMC-BESS subsystem fails, identifying the failure type of the failed battery module;

[0033] Based on the identified fault type, the corresponding BMS control strategy is called to perform fault analysis and processing.

[0034] In the technical solution of the embodiment of the present application, during the switching of the working mode, the fault type of the battery module is identified and the corresponding BMS control strategy is called to solve the fault of the battery module, which can comprehensively and efficiently solve the fault of the battery module and effectively avoid the safety problems caused by the failure of the battery module.

[0035] In some embodiments, performing power on and off operations on a normal battery module includes:

[0036] Monitor battery status parameters of normal battery modules;

[0037] sorting the normal battery modules according to their battery status parameters;

[0038] According to the preset control strategy, the normal battery modules after sorting are powered on and off in sequence.

[0039] In the technical solution of the embodiment of the present application, by monitoring the battery modules and sorting the normal battery modules according to their battery status parameters, the remaining power of each normal battery module can be clearly determined, and the battery modules can be powered on and off according to the remaining power. The power on and off operations of batteries with high remaining power can be completed first, and the battery charging and discharging can be completed first, thereby improving the efficiency of power support.

[0040] In some embodiments, according to a preset control strategy, sequentially powering on and off the sorted normal battery modules includes:

[0041] The first battery switch and the second battery switch of the normal battery module after sorting are closed in sequence, and then the first battery switch is opened. The first battery switch includes a battery switch with a resistor, and the second switch includes a battery switching switch.

[0042] In the technical solution of the embodiment of the present application, since the switch with resistance has the function of battery charging and discharging buffering, the power on and off operations are performed in the above manner, so that the battery module can smoothly transition charge and discharge, thereby protecting the battery.

[0043] In some embodiments, performing power balancing according to a preset power balancing strategy corresponding to the operating mode includes:

[0044] If the working mode is flexible direct current transmission mode, the external grid load data of the power system is obtained and power balancing is performed based on the external grid load data;

[0045] Alternatively, if the operating mode is flexible direct current transmission and battery energy storage mode, the external grid load data is monitored to obtain the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem. Power balancing is performed based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem.

[0046] Alternatively, if the working mode is the cascade H-bridge energy storage mode, the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module of the MMC-BESS subsystem are obtained, and power support is provided based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module.

[0047] In the technical solution of the embodiment of the present application, different power balancing strategies are adopted for power balancing in each working mode, thereby realizing power balancing of the power system in the flexible direct current transmission mode, power balancing in the mode combining battery energy storage and flexible direct current transmission, and power balancing in the cascaded H-bridge mode, thereby achieving the effect of power balancing of a power system that meets the power requirements of multiple working scenarios.

[0048] In some embodiments, performing power balancing based on load data of the flexible direct current transmission subsystem and AC side power surplus data of the MMC-BESS subsystem includes:

[0049] If, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission subsystem requires power support and the AC side surplus power of the MMC-BESS subsystem meets the support conditions, the AC side surplus power of the MMC-BESS subsystem will be transmitted to the flexible direct current transmission subsystem through flexible direct current transmission for power balancing;

[0050] If, based on the load data of the flexible direct current transmission system and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission system requires power support and the AC side surplus power of the MMC-BESS subsystem does not meet the support conditions, the AC side surplus power of the MMC-BESS subsystem will be transmitted to the flexible direct current transmission system, and the battery modules of the MMC-BESS subsystem will be controlled to discharge the flexible direct current transmission system to achieve power balancing;

[0051] If, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission subsystem requires power support and the MMC-BESS subsystem does not have a power surplus, the battery module is controlled to provide discharge support to the flexible direct current transmission subsystem and the MMC-BESS subsystem to achieve power balancing.

[0052] In the technical solution of the embodiment of the present application, by comparing the load data of the flexible direct current electronic system and the AC side power surplus data of the MMC-BESS subsystem, corresponding measures are taken in a targeted manner to provide power support, thereby achieving power balance under various conditions.

[0053] In some embodiments, providing power support based on AC side power surplus data of the MMC-BESS subsystem and battery module status data includes:

[0054] If, based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module, it is determined that the MMC-BESS subsystem has AC side power surplus and the battery module is chargeable, the battery module is charged and placed in a hot standby state;

[0055] If it is determined that the AC side of the MMC-BESS subsystem requires power support based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module, the battery module is controlled to discharge the AC side of the MMC-BESS subsystem to achieve power balancing.

[0056] In the technical solution of the embodiment of the present application, by monitoring the status of the battery modules, battery modules with abnormal status or unable to be charged and discharged can be screened out in time to ensure the normal operation of power balancing, and through the AC side power surplus data, the charging and discharging of the battery modules can be further controlled, so that power balancing can be completed quickly and reasonably.

[0057] In some embodiments, before charging the battery module, the method further includes:

[0058] Monitor battery status parameters of battery modules;

[0059] sorting the battery modules according to their battery status parameters;

[0060] The first battery switch and the second battery switch of the sequenced battery module are closed in sequence, and then the first battery switch is opened. The first battery switch includes a battery switch with a resistor, and the second switch includes a battery insertion and removal switch.

[0061] In the technical solution of the embodiment of the present application, since the switch with resistance has the function of battery charging and discharging buffering, before charging the battery module, the battery module is powered on and off in the above-mentioned manner, which can enable the battery module to undergo smooth transition charging and discharging, thereby protecting the battery.

[0062] In some embodiments, before controlling the battery module to provide discharge support to the AC side of the MMC-BESS subsystem, the method further includes:

[0063] Monitor battery status parameters of battery modules;

[0064] sorting the battery modules according to their battery status parameters;

[0065] The first battery switch and the second battery switch of the sequenced battery module are closed in sequence, and then the first battery switch is opened to provide power support to the AC side of the MMC-BESS subsystem. The first battery switch includes a battery switch with a resistor, and the second switch includes a battery switching switch.

[0066] In the technical solution of the embodiment of the present application, since the switch SW2 is a switch with resistance, it has the function of battery charging and discharging buffering. Therefore, before providing power support to the AC side power, the battery module is powered on and off in the above-mentioned manner, which can enable the battery module to smoothly transition between charging and discharging, protect the battery, and ensure the safety of power support.

[0067] In a second aspect, the present application provides a power balancing device for a power system, the device comprising: a controller, and a power system connected to the controller, the power system comprising a VSC flexible direct current electronic system and an MMC-BESS subsystem;

[0068] The controller is used to determine the operating mode of the power system, control the switching of the VSC flexible direct current electronic system and the MMC-BESS subsystem, switch the power system to the corresponding operating mode, and perform power balancing according to the preset power balancing strategy corresponding to the operating mode.

[0069] The power balancing device of the power system of the embodiment of the present application provides a power balancing solution for the power system including a flexible direct current transmission subsystem and an MMC-BESS subsystem. Specifically, after determining the working mode of the power system, the controller switches the power system to the corresponding working mode by switching the flexible direct current transmission subsystem and the MMC-BESS subsystem, thereby realizing flexible switching of multiple working modes of the power system. In addition, power balancing is performed according to the preset power balancing strategy corresponding to each working mode, realizing power balancing of multiple working modes such as flexible direct current transmission mode or flexible direct current transmission energy storage mode, thereby achieving power balancing of a power system that meets multiple working scenarios. While realizing power balancing of the power system, the flexibility of power balancing regulation is also improved, thereby improving the power absorption and regulation capability of the power system, and ensuring the power quality and power supply reliability of the power system.

[0070] In a third aspect, the present application provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the power balancing method for the power system described above when executing the computer program.

[0071] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the above-mentioned power balancing method for a power system.

[0072] In a fifth aspect, the present application further provides a computer program product, which includes a computer program that implements the steps in the power balancing method for a power system when executed by a processor.

[0073] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0075] FIG1 is a diagram illustrating an application environment of a power balancing method for an electric power system according to some embodiments of the present application;

[0076] FIG2 is a schematic flow chart of a power balancing method for a power system in some embodiments of the present application;

[0077] FIG3 is a topological diagram of an MMC-BESS subsystem in some embodiments of the present application;

[0078] FIG4 is a schematic structural diagram of a submodule of a bridge arm in an MMC-BESS subsystem in some embodiments of the present application;

[0079] FIG5 is a schematic diagram of a detailed flow chart of a power balancing method for a power system in some embodiments of the present application;

[0080] FIG6 is a schematic diagram of switching of working modes of a power system in some embodiments of the present application;

[0081] FIG7 is a schematic diagram of a detailed flow chart of a power balancing method for a power system in some embodiments of the present application;

[0082] FIG8 is a schematic diagram of the structure of a power balancing device for a power system in some embodiments of the present application;

[0083] FIG9 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0084] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0085] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0086] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0087] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0088] In recent years, building a new power system dominated by renewable energy has become a hot topic, aiming to improve the grid's ability to absorb and regulate high proportions of renewable energy. However, due to the inherent randomness, volatility, and intermittency of renewable energy generation, the integration of large-scale renewable energy into the grid will significantly increase the difficulty of maintaining a spatial and temporal balance of power in the power system. Therefore, some experts believe that enhancing the flexible regulation capabilities of the new power system is key to ensuring balanced power supply and demand over different timescales and high-level renewable energy consumption.

[0089] Due to its advantages in long-distance, high-capacity power transmission, DC transmission technology plays a vital role in optimizing the allocation of energy resources. Traditionally, common HVDC transmission architectures include the following: Line Commutated Converter Based High Voltage Direct Current (LCC-HVDC) systems and Modular Multilevel Converter Based High Voltage Direct Current (MMC-HVDC) systems. Early hybrid DC transmission systems, such as the LCC-MMC parallel hybrid DC transmission system, were typically single-transmitting and single-receiving systems, using different types of converters at each end.

[0090] The inventors note that the aforementioned DC transmission system only considers the conventional DC to flexible DC transmission mode, without considering bidirectional transmission and load mutual support, nor the switching from double-ended to single-ended. Therefore, the power system's regulation is clearly insufficiently flexible and cannot guarantee the power quality and reliability of the power system. Furthermore, conventional technologies also present the following problems: The independent investment costs of the PCS (Power Conversion System) and energy storage batteries in current energy storage systems are high; multiple PCSs connected in parallel are prone to oscillation; the power conversion efficiency of two-level / three-level PCSs is low; the large number of batteries connected in series and parallel requires a strong BMS with strong battery management capabilities; and the three-phase imbalance and line overload / underload problems of the 10kV distribution network are common and serious.

[0091] The inventors discovered that the MMC-BESS has two external ports, AC and DC, and simultaneously supports AC grid connection, DC grid connection, and energy storage. When used in a power grid, it can connect to both AC and DC grids separately or simultaneously. The MMC-BESS utilizes an integrated modular design, enabling flexible regulation of the energy storage system's output power and optimizing battery management capabilities. This eliminates grid-connected harmonics, reduces investment costs, lowers the DC voltage the battery must withstand, and reduces the BMS's requirements for battery management capabilities. This results in lower system losses, better economic benefits, and greater operational reliability. Therefore, research on load support methods for multi-scenario mode switching based on the MMC-BESS is considered to be of great research significance for new power systems dominated by renewable energy.

[0092] Based on the above considerations, in order to solve the problem that the output power regulation of the above-mentioned traditional transmission system is not flexible enough, power balancing cannot be achieved stably, and the power quality and power supply reliability of the power system are guaranteed, a power system including a flexible direct current transmission subsystem and an MMC-BESS subsystem is proposed. First, the working mode of the power system is determined. The working mode includes a flexible direct current transmission mode, a flexible direct current transmission and battery energy storage mode, or a cascaded H-bridge energy storage mode. The power system is switched to the corresponding working mode to achieve flexible switching of multiple working modes. In addition, power balancing is performed according to the preset power balancing strategy corresponding to each working mode, and power balancing in the flexible direct current transmission mode, power balancing in the combination of energy storage and flexible direct current transmission mode, and power balancing in the cascaded H-bridge mode are achieved, so that a power system can meet power balance in multiple working scenarios. While achieving power balance of the power system, the flexibility of power balancing regulation is also improved, thereby improving the power absorption and regulation capabilities of the power system and ensuring the power quality and power supply reliability of the power system.

[0093] The power balancing method of the power system provided in the embodiment of the present application can be applied to the application environment shown in Figure 1. In which, the terminal 102 communicates with the control terminal 104 of the power system through the network. The power system includes an interconnected flexible direct current transmission electronic system and an MMC-BESS subsystem. The data storage system can store data that the server 104 needs to process. The data storage system can be integrated on the control terminal 104, or it can be placed on the cloud or other network servers. Specifically, the power system personnel can send a control instruction to the control terminal 104 through the terminal 102. The control terminal 104 responds to the control instruction and determines the working mode of the power system. Then, the power system switches to the corresponding working mode, and then obtains a preset power balancing strategy corresponding to the working mode. Power balancing is performed according to the preset power balancing strategy corresponding to the working mode. The working mode includes a flexible direct current transmission mode, a flexible direct current transmission and battery energy storage mode, or a cascaded H-bridge energy storage mode. In which, the terminal 102 can be, but is not limited to, various personal computers, laptops, smart phones, tablets, Internet of Things devices and portable wearable devices. The Internet of Things devices can be smart speakers, smart TVs, smart air conditioners, smart car devices, etc. The portable wearable device may be a smart watch, a smart bracelet, a head-mounted device, etc. The control terminal 104 may be implemented as an independent server or a server cluster consisting of multiple servers.

[0094] In one embodiment, as shown in FIG2 , a power balancing method for a power system is provided. The method is described by taking the control terminal 104 of the power system in FIG1 as an example. The power system includes an interconnected flexible direct current transmission subsystem and an MMC-BESS subsystem. The method includes the following steps:

[0095] Step 100: Determine the operating mode of the power system, wherein the operating mode includes a flexible direct current transmission mode, a flexible direct current transmission and battery energy storage mode, or a cascaded H-bridge energy storage mode.

[0096] In this embodiment, the power system is a hybrid flexible direct current transmission system. The flexible direct current transmission subsystem can be a flexible high-voltage direct current transmission subsystem based on VSC (hereinafter referred to as the VSC end), and the MMC-BESS subsystem can be a new energy storage system integrating modular multilevel converters (Modular Multilevel Converter based Battery Energy Storage System, MMC-BESS). That is, the power system can be a VSC+MMC-BESS two-terminal or multi-terminal grid flexible direct current transmission system with battery energy storage (referred to as VSC+MMC-BESS flexible direct current transmission energy storage system), which is used for the engineering integration of AC / DC microgrid / distribution network technology and battery energy storage technology. In addition, the power system also includes a BMS system. In layman's terms, the flexible direct current transmission mode, namely the VSC+VSC dual-terminal grid flexible direct current transmission mode, can be understood as a mode in which only the flexible direct current transmission subsystem participates in power support. The flexible direct current transmission and battery energy storage mode, namely the VSC+MMC-BESS dual-terminal or multi-terminal grid flexible direct current transmission mode, can be understood as a mode in which both the flexible direct current transmission subsystem and the MMC-BESS subsystem participate in power support. The cascaded H-bridge energy storage mode, namely the MMC-BESS AC-end direct energy storage mode, can be understood as a mode in which only the AC side of the MMC-BESS subsystem participates in power support.

[0097] The topology of the MMC-BESS subsystem is shown in Figure 3. The MMC-BESS subsystem consists of three phase clusters, each of which is further divided into upper and lower bridge arms. Each bridge arm contains N sub-modules (SMs). A sub-module consists of a half-bridge circuit, a battery, and a filter capacitor, with the battery connected directly in parallel across the filter capacitor. Specifically, the sub-modules in each bridge arm are shown in Figure 4. These sub-modules include a half-bridge energy storage sub-module and a full-bridge energy storage sub-module. Both the half-bridge and full-bridge energy storage sub-modules include a power module and a battery module. As shown in Figure 4, the half-bridge circuit in the power module contains two IGBTs (Insulated Gate Bipolar Transistors), a capacitor, a resistor, and a bypass switch SW1. The IGBT switches are controlled to charge the capacitor, generating a DC voltage across the capacitor. The full-bridge circuit in the power module contains four IGBTs, a capacitor, a resistor, and a bypass switch SW1. The IGBT switches are controlled to charge the capacitor, generating a DC voltage across the capacitor. The battery module includes a switch SW2 with a resistor, a battery enable / disable switch SW3, and a battery cluster. The switch SW2 with a resistor acts as a battery charge / discharge buffer. Two fuses are located between the power module and the battery module for overcurrent protection.

[0098] In this embodiment, the operating mode can be determined by receiving a control instruction, responding to the control instruction, and determining the operating mode of the power system. Alternatively, the operating mode can be determined by monitoring the operating status of the power system, obtaining fault monitoring data, and then determining the operating mode based on the fault monitoring data. Specifically, the operating mode can be any one of a flexible direct current transmission power mode, a flexible direct current transmission and battery energy storage power mode, or a cascaded H-bridge energy storage power mode.

[0099] Step 200: Switch the power system to a corresponding operating mode.

[0100] After obtaining the operating mode, the power system can be directly switched to the corresponding operating mode according to the obtained operating mode. For example, if the operating mode is flexible direct current transmission mode, the power system is switched to flexible direct current transmission mode; if the operating mode is flexible direct current transmission and battery energy storage mode, the power system is switched to flexible direct current transmission and battery energy storage mode; if the operating mode is cascaded H-bridge energy storage mode, the power system is switched to cascaded H-bridge energy storage mode. In other words, the power system in this embodiment can be switched to multiple operating modes.

[0101] Step 300: Perform power balancing according to a preset power balancing strategy corresponding to the working mode.

[0102] Power balancing can also be called load support, power transmission or power support. The power balancing strategy refers to the strategy or rule used to maintain power balance in the power system. In this embodiment, a corresponding power balancing strategy is pre-set for each working mode. The working mode and the power balancing strategy are one-to-one corresponding. When the working mode is determined, the power balancing strategy is also determined. Specifically, the corresponding power balancing strategy can be obtained according to the working mode. In this embodiment, the power balancing strategy can correspond to a flexible direct current transmission power balancing strategy, a flexible direct current transmission and battery energy storage power balancing strategy, or a cascaded H-bridge energy storage power balancing strategy. After the power system is switched to any one of the working modes of flexible direct current transmission mode, flexible direct current transmission and battery energy storage mode, or cascaded H-bridge energy storage mode, the power balancing strategy corresponding to the working mode can be obtained, and then power balancing can be performed according to the power balancing strategy.

[0103] In another embodiment, active power and reactive power can be controlled through the secondary architecture system by setting the voltage and power of the load. The power system also has the ability to adjust the bus or feeder voltage and balance the bus or feeder load through four-quadrant control. Specifically, the secondary architecture system includes a field layer, a control layer, and an operator control layer. The field layer includes control and protection equipment that communicates with the MMC-BESS subsystem, including AC energy consumption devices, DC circuit breakers, safety devices, valve control, BMS devices, and also includes battery modules and power modules. The field layer is connected by optical fiber between the upper and lower levels, and exchanges data with the control layer. It completes the control of AC energy consumption devices such as preparation signals, and completes the control of DC circuit breakers such as tripping signals due to failure protection. It also controls the safety devices of DC emergency power control commands, converter lockout, and networking / islanding signals.

[0104] The BMS monitors and provides early warnings for the battery module's SOC, transmitting the status of problematic battery modules to the valve control system. The valve control system receives the modulated waveform sent by the control layer and, through bridge arm circulating current suppression, modulation, voltage balancing, and switching frequency optimization, controls the power and battery modules on and off, the bypass switch (SW1), the battery resistor switch (SW2), and the battery switching switch (SW3). This system can be controlled in flexible direct current (FDC) mode, flexible direct current (FDC) and battery energy storage mode, or cascaded H-bridge mode. The system also ensures DC system stability by enabling redundant modules and disabling faulty modules. The BMS also transmits battery status to the remote control layer in real time via the IEC61850 MMS for real-time monitoring.

[0105] The control layer is the core of the secondary system's control and protection. It receives the operation commands from the operating personnel and, at the same time, receives signals such as the line connection status, unlocking, islanding grid connection, voltage and current from other circulating current stations through the SDH optical fiber network at a rate of 2 M. Coordinated control is carried out by the converter station's control layer, which has functions such as voltage takeover, grid voltage range control, power flow optimization, and related sequence control and interlock functions sent to the pole control A / B. Pole control A / B receives information such as the NBGS (neutral bus grounding switch) switch status and the operating status of the opposite end of other converter stations through the 2 M rate optical fiber channel for inter-station communication. The bipolar control receives commands from the operating personnel's control layer, performs sequence control and interlock,全站双极有功、无功分配、附加控制、功率盈余控制、安稳及广域协调接口及控制,并将控制命令下发至极控。极控接收上层下发的命令,进行偏差斜率控制、分接头控制、功率控制、顺控联锁,并结合运行人员控制层下发的命令进行模式选择和控制指令生成,进行定直流电压控制、定有功功率控制、定无功功率控制、定交流电压控制、定频率控制、孤岛(VF(电压频率)控制,通过外环控制器将控制模式和控制指令下发到电流内环控制器,输出桥臂电压参考值,形成调制波,下发到阀控。

[0106] The remote personnel control layer mainly includes the monitoring background, with an engineer station, a Web interface station, a time synchronization server, a simulation server, a protection and fault recording information management station, an energy management system, etc., and at the same time receives management from the remote dispatching layer.

[0107] Specifically, the ability to pass through the four-quadrant balance bus or feeder load can be as follows: Let the AC side terminal voltage of the VSC be Uc, the bus or feeder voltage be Us, and the angle between Uc and Us be θ. Then, by controlling Uc*sinθ, the magnitude and direction of the active power can be controlled, and by controlling Us - Uc*cosθ, the magnitude and direction of the reactive power can be controlled, thus achieving four-quadrant control.

[0108] Specifically, when operating in the first quadrant, Uc*cosθ > Us and θ > 0, the MMC-BESS subsystem can output active power and generate reactive power externally, realizing the functions of power support and voltage support.

[0109] When operating in the second quadrant, Uc*cosθ > Us and θ < 0, the MMC-BESS subsystem can absorb the power surplus of the power grid system while generating reactive power to provide voltage support for the system.

[0110] When operating in the third quadrant, Uc*cosθ < Us and θ < 0, the MMC-BESS subsystem absorbs the power surplus of the power grid system while absorbing excessive reactive power of the power grid, solving the problem of overvoltage of the bus or feeder. <00002

[0111] When operating in the fourth quadrant, Uc*cosθ < Us and θ > 0. The MMC-BESS subsystem can absorb excess reactive power from the power grid while providing active power to the power grid.

[0112] In the technical solution of the embodiment of the present application, a power balance scheme applied to a power system including a flexible DC transmission subsystem and an MMC-BESS subsystem is provided. In the whole scheme, the working mode of the power system is determined, and the power system is switched to the corresponding working mode, realizing flexible switching of multiple working modes. Moreover, power balance is carried out according to the preset power balance strategies corresponding to each working mode, achieving power balance in multiple working modes such as the flexible DC transmission mode or the flexible DC transmission energy storage mode, achieving power balance of a power system under multiple scenarios. While realizing the power balance of the power system, the flexibility of power balance regulation is also improved, thereby improving the power consumption and regulation ability of the power system to power, and ensuring the power quality and power supply reliability of the power system.

[0113] In some embodiments, as shown in Figure 5, step 100 includes: step 120, obtaining the fault monitoring data of the flexible DC transmission subsystem and the MMC-BESS subsystem, and determining the working mode of the power system according to the fault monitoring data.

[0114] The fault monitoring data refers to the data that can characterize whether a fault occurs in the operation of the monitored power system. That is, the fault monitoring data can be the data characterizing the normal operation of the power system, or the data characterizing the occurrence of a fault in the operation of the power system. Specifically, it can be to monitor whether abnormal conditions such as short circuit, open circuit, battery overcharge, battery over-discharge, thermal management failure, insulation failure, wiring failure, etc. occur in the flexible DC transmission subsystem and the MMC-BESS subsystem. In this embodiment, the working mode can be determined according to whether a fault occurs in the flexible DC transmission subsystem and the MMC-BESS subsystem. Specifically, it can be to obtain the fault monitoring data of the flexible DC transmission subsystem and the MMC-BESS subsystem, and determine whether a fault occurs in the flexible DC transmission subsystem and the MMC-BESS subsystem according to the fault monitoring data, and then determine the working mode of the power system. In other embodiments, the determination of the working mode can also be: receiving a control instruction carrying the working mode, and parsing the working mode in the control instruction to determine the specific working mode. Specifically, it can be to receive the message data carrying the control instruction sent by the external dispatching end through a preset communication protocol. The control instruction carries a working mode field. Then, it is judged whether the message data is legal. When it is determined that the message data is legal, the instruction segment and data segment of the message header in the message data are identified, and the working mode field included in the data segment is parsed to determine the corresponding working mode.

[0115] In the technical solution of the embodiment of the present application, by obtaining the fault monitoring data of the flexible direct current electronic system and the MMC-BESS subsystem and determining the working mode, abnormal situations can be discovered in time, power support can be avoided in the event of a fault, affecting the efficiency of power support, and ensuring the normal operation of the power system.

[0116] In some embodiments, step 120 includes:

[0117] Step 122: If it is determined according to the fault monitoring data that the flexible direct current transmission electronic system has a fault, the operating mode is determined to be the cascaded H-bridge energy storage mode.

[0118] Step 124: If it is determined according to the fault monitoring data that the MMC-BESS subsystem has a fault, the operating mode is determined to be the flexible direct current transmission mode.

[0119] Step 126: If it is determined based on the fault monitoring data that neither the flexible direct current transmission subsystem nor the MMC-BESS subsystem has any fault, the operating mode is determined to be the flexible direct current transmission and battery energy storage mode.

[0120] Continuing with the above embodiment, the operating mode can be determined based on fault monitoring data: if the fault monitoring data indicates a fault in the flexible direct current transmission subsystem, this means that the flexible direct current transmission subsystem cannot normally participate in power support, i.e., the operating mode is determined to be the cascaded H-bridge energy storage mode; if the fault monitoring data indicates a fault in the MMC-BESS subsystem, this means that the MMC-BESS subsystem cannot normally participate in power support, i.e., the operating mode is determined to be the flexible direct current transmission mode; if the fault monitoring data indicates that neither the MMC-BESS subsystem nor the flexible direct current transmission subsystem has a fault, this indicates that the system is operating normally, in which case the operating mode is determined to be the flexible direct current transmission and battery energy storage mode, i.e., operating in the normal operating mode. Fault types include, but are not limited to, at least one of short circuit, open circuit, battery overcharge, battery overdischarge, thermal management failure, insulation failure, wiring fault, and other abnormal conditions.

[0121] In the technical solution of the embodiment of the present application, whether a fault occurs in the flexible direct current transmission electronic system and the MMC-BESS subsystem is determined by fault monitoring data, and then the corresponding working mode is selected in a targeted manner according to the fault conditions of the above two subsystems, which can ensure safe and accurate power balancing.

[0122] In some embodiments, step 200 includes: controlling the battery modules and the flexible direct current transmission electronic system of the MMC-BESS subsystem according to a preset mode switching strategy corresponding to the determined operating mode, and switching the power system to the corresponding operating mode.

[0123] In practical applications, a corresponding mode switching strategy is pre-set for each operating mode. This strategy can involve monitoring the SOC of battery modules in the power system through the BMS and providing early warnings. The status of problematic battery modules is then transmitted to the valve control system. The valve control system receives the modulation wave sent by the control layer and controls the power modules and battery modules of the MMC-BESS subsystem, as well as the flexible direct current transmission electronic system, by suppressing bridge arm circulating current, modulating, balancing voltage, and optimizing switching frequency. This switches the operating mode, controlling the bypass switch (SW1), the battery resistor switch (SW2), and the battery switching switch (SW3). Simultaneously, the DC system's stability is ensured by enabling redundant modules and disabling faulty modules.

[0124] In the technical solution of the embodiment of the present application, the battery module and the flexible direct current transmission electronic system of the MMC-BESS subsystem are switched on and off according to the preset mode switching strategy corresponding to the working mode, thereby simply and efficiently realizing the switching of multiple working modes of the power system and improving the flexibility of mode switching.

[0125] As shown in FIG5 , in some embodiments, step 200 includes:

[0126] Step 220: If the working mode is the flexible direct current transmission mode, the battery module of the MMC-BESS subsystem is turned off to switch the power system to the flexible direct current transmission mode.

[0127] Step 240, or, if the operating mode is the flexible direct current transmission and battery energy storage mode, monitor the battery status of the battery modules of the MMC-BESS subsystem, screen out abnormal battery modules and normal battery modules, shut down the abnormal battery modules, and power on and off the normal battery modules to switch the power system to the flexible direct current transmission and battery energy storage mode.

[0128] Step 260 , or, if the operating mode is the cascade H-bridge energy storage mode, disconnect the loop of the flexible direct current electronic system to switch the power system to the cascade H-bridge energy storage mode.

[0129] In specific implementation, as shown in FIG6 , the switching process of the working mode can be: for the flexible direct current transmission mode (using the double-terminal grid VSC+VSC as an example in FIG6 ), the switch SW2 and the switch SW3 in FIG4 are opened, that is, all the battery modules in the MCC-BESS subsystem are turned off, and the power system is switched to the flexible direct current transmission mode. For the flexible direct current transmission and battery energy storage mode (using the double-terminal grid VSC+MCC-BESSC as an example in FIG6 ), the status of the battery module is first monitored through the BMS system, for example, monitoring whether the battery module has abnormal conditions such as short circuit, open circuit, overcharge, over-discharge, overtemperature, and insulation failure, so as to screen out abnormal battery modules and normal battery modules. Then, the abnormal battery module is opened, that is, the switch SW2 and the switch SW3 are opened to turn off the abnormal battery module, and then the normal battery module is powered on and off to switch the power system to the flexible direct current transmission and battery energy storage mode. For the cascade H-bridge energy storage mode (using the double-end grid MMC-BESSC (cascade H-bridge) as an example in Figure 6), without considering the transmission support at both ends or multiple ends of the DC, by tripping the AC circuit breaker and DC circuit breaker of the VSC-based flexible direct current transmission subsystem (hereinafter referred to as the VSC end) and opening the corresponding knife switches, opening the DC conversion switch and the grounding switch, the switching of the single-end MMC-BESS, i.e., the cascade H-bridge energy storage mode, is achieved. It can be understood that if the power system is operating in the flexible direct current transmission and battery energy storage mode, if the flexible direct current energy storage subsystem or the MCC-BESS subsystem fails, the system will be switched from the flexible direct current transmission and battery energy storage mode to the flexible direct current transmission mode or the cascade H-bridge energy storage mode in the above manner. The above working modes can be switched according to actual conditions. For example, the working mode can be switched from flexible direct current transmission and battery energy storage mode to cascaded H-bridge energy storage mode or flexible direct current transmission mode, or from cascaded H-bridge energy storage mode or flexible direct current transmission mode to flexible direct current transmission and battery energy storage mode.

[0130] In some embodiments, if a battery module of the MMC-BESS subsystem fails, the fault type of the failed battery module is identified, and based on the identified fault type, a corresponding BMS control strategy is called to perform fault analysis and processing.

[0131] If a battery module in the MMC-BESS subsystem fails during the actual FDC mode transition, the fault type of the module can be identified. Based on the identified fault type, the corresponding BMS control strategy can be invoked for fault analysis and resolution. Specifically, if a battery module in the MMC-BESS subsystem fails to shut down properly, the bypass switch connected to that module can be closed, and a functioning battery module from the redundant submodule can be selected for operation. During the transition between FDC and BESS modes, abnormal battery modules can be identified. Depending on the type of abnormality, such as battery overcharge, battery short circuit, or thermal management failure, the BMS can be invoked to implement existing control strategies, such as exception handling strategies, to resolve the anomaly. This allows for strict control of charging and discharging to prevent abnormalities such as overcharging, overdischarging, and overheating. If a DC circuit breaker fails to close properly during the cascaded H-bridge energy storage mode transition, a backup protection strategy can be implemented, such as opening a backup switch connected to the DC circuit breaker to trip the DC circuit breaker. It is understandable that the above method is only for illustrative purposes. If an abnormal situation occurs during the working mode switching process, the abnormal situation can be resolved by combining the main control and the backup control.

[0132] In the technical solution of the embodiment of the present application, the status of the battery module is monitored by the BMS, and abnormalities are screened out. The battery modules with problems are screened out and shut down, thereby avoiding the adverse effects of abnormal battery modules on the power system. By controlling the battery resistor switch (SW2) of the battery module, the battery insertion and withdrawal switch (SW3), and the corresponding knife switches, multi-mode switching of the power system is achieved.

[0133] In some embodiments, performing power on and off operations on normal battery modules includes: monitoring battery status parameters of the normal battery modules, sorting the normal battery modules according to the battery status parameters of the normal battery modules, and performing power on and off operations on the sorted normal battery modules in sequence according to a preset control strategy.

[0134] Battery status parameters include battery status parameters such as SOC (State of Charge), SOS (State of Safe), SOH (State of Health) and / or SOF (State of Function). The battery SOC value refers to the state of charge, which is used to reflect the remaining capacity of the battery. Its numerical value is defined as the ratio of the remaining capacity to the battery capacity, and is usually expressed as a percentage. Continuing from the above embodiment, in this embodiment, the power on and off operations on the normal battery modules can be performed by monitoring the SOC values ​​of the normal battery modules through the BMS system, obtaining the SOC values ​​of each normal battery module, and then sorting the normal battery modules in descending order according to the SOC values. Then, according to the preset control strategy, starting from the normal battery module with the highest SOC value, the sorted normal battery modules are sequentially powered on and off. It can be understood that the sorting method can also be ascending sorting, which can be determined according to the actual situation.

[0135] In another embodiment, the normal battery modules can be sorted according to the battery status parameters of the normal battery modules, or the SOS value, SOH value or SOF value of each battery module can be obtained, and the normal battery modules can be sorted according to the SOS value, SOH value or SOF value. In another embodiment, the battery status parameters including the SOC value, SOS value, SOH value and SOF value can be normalized to obtain the normalized SOX, and the scores of the battery modules can be set accordingly based on the size of the SOX value, and the modules can be sorted according to the scores. In other embodiments, the normal battery modules can be sorted according to the combination of the SOC value, SOS value, SOH value and SOF value, which is not limited here, as long as the battery modules with good performance can be screened out. In other embodiments, the normal battery modules can be sorted according to the voltage or power of the battery modules, which is not limited here.

[0136] In the technical solution of the embodiment of the present application, the battery modules are monitored by the BMS system, and the normal battery modules are sorted according to their SOC values, so that the remaining power of each normal battery module can be clearly determined. Subsequently, the battery modules are powered on and off according to the remaining power, and the power on and off operations of the batteries with high remaining power can be completed first, so that the battery charging and discharging can be completed first, and the efficiency of power support can be improved subsequently.

[0137] In some embodiments, according to a preset control strategy, the power-on and power-off operations on the sorted normal battery modules are performed in sequence, including: closing the first battery switch and the second battery switch of the sorted normal battery modules in sequence, and then disconnecting the first battery switch, the first battery switch includes a battery switch with a resistor, and the second switch includes a battery insertion and withdrawal switch.

[0138] Following the above embodiment, during practice, the applicant discovered that when charging the battery, the battery on / off switch connected to the battery module, namely SW3 in this application, is generally closed directly to charge the battery module. However, this method is prone to battery overcharging, which can easily cause battery failure. To address this problem, a resistor switch is introduced. Before closing the battery on / off switch, the resistor switch is closed first, achieving a smooth power supply effect through resistance consumption. Specifically, after the normal battery modules are sorted, switches SW2 and SW3 of the normal battery modules are closed in sequence according to the sorted order, and then switch SW2 is opened to complete the power on and off operations in sequence.

[0139] In the technical solution of the embodiment of the present application, since the switch SW2 is a switch with resistance, it has the function of battery charge and discharge buffering. Therefore, performing power on and off operations in the above manner can enable the battery module to undergo smooth transition charge and discharge, thereby protecting the battery.

[0140] In another embodiment, according to a preset control strategy, the power-on and power-off operations of the sorted normal battery modules can be performed in sequence: the resistor switch in the above embodiment is replaced with an inductive switch such as SW4, and then the switches SW4 and SW3 of the normal battery module are closed in sequence, and then the switch SW2 is opened. In this way, the impedance of the inductive switch is used to achieve a smooth charging effect. In another embodiment, a capacitor can be connected in parallel at both ends of the battery module, and the capacitor is connected to a switch SW5 and a discharge circuit. The switches SW5 and SW3 are closed at the same time to charge the capacitor and the battery module at the same time, and a part of the power is consumed by the capacitor to achieve a smooth power transmission effect. When the SOC of the battery module reaches a preset threshold value such as 80%, the switch SW5 is opened, and then the automatic discharge circuit with the capacitor is closed to completely discharge the capacitor and wait for the next power-on and power-off operation. It can be understood that the discharge circuit of the capacitor can achieve complete discharge of the capacitor, and the specific circuit structure is not limited here.

[0141] In the solution of the embodiment of the present application, by introducing a capacitor or an inductive switch, the battery charging and discharging is buffered, thereby avoiding overcharging when charging the battery module and protecting the battery module.

[0142] As shown in FIG5 , in some embodiments, step 300 includes:

[0143] Step 320: If the working mode is the flexible direct current transmission mode, the external grid load data of the power system is obtained, and power balancing is performed according to the external grid load data.

[0144] Step 340: If the operating mode is the flexible direct current transmission and battery energy storage mode, monitor the external grid load data, obtain the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, and perform power balancing based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem.

[0145] Step 360: If the operating mode is the cascade H-bridge energy storage mode, obtain the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery modules of the MMC-BESS subsystem, and perform power support based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery modules.

[0146] The load data of the external power grid refers to the load data of the two-end power grid or multi-end power grid connected to the power system. In specific implementation, power balancing is performed according to the preset power balancing strategy corresponding to the working mode: if the working mode is the flexible direct current transmission mode (VSC+VSC two-end power grid flexible direct current transmission mode), the load data of the external power grid is obtained, and the target power grid that needs power support is determined based on the load data of the external power grid, and power support is provided to the target power grid through flexible direct current transmission to achieve power balancing. For example, if the load data of the VSC-end power grid A is 90% and the load data of the VSC-end power grid B is 30%, the power of the VSC-end power grid B is transmitted to the VSC-end power grid A through flexible direct current transmission, so that the load data of the VSC-end power grid A and the VSC-end power grid B are 60%.

[0147] If the operating mode is flexible direct current transmission and battery energy storage mode, the external grid load data is monitored to obtain the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem. Then, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, the end that needs power support is determined, and power balancing can be achieved through flexible direct current transmission. Specifically, in the flexible direct current transmission and battery energy storage mode, the MMC-BESS subsystem can have 12 power support modes, which can be:

[0148] 1. In the mode where the battery is neither charging nor discharging, the DC side transmits power to the AC side.

[0149] 2. In the mode where the battery is neither charging nor discharging, power is transmitted from the AC side to the DC side.

[0150] 3. In battery charging mode, the AC side and DC side charge the battery simultaneously.

[0151] 4. In battery charging mode, the DC side charges the battery and transmits power to the AC side at the same time.

[0152] 5. In battery charging mode, the AC side charges the battery and transmits power to the DC side at the same time.

[0153] 6. In battery charging mode, the DC side and the battery operate independently and the battery is charged.

[0154] 7. In battery charging mode, the AC side and the battery are charged independently.

[0155] 8. In battery discharge mode, the battery discharges to both the DC and AC sides simultaneously.

[0156] 9. In battery discharge mode, the battery and AC side simultaneously transmit power to the DC side.

[0157] 10. In battery discharge mode, the battery and DC side transmit power to the AC side at the same time.

[0158] 11. In battery discharge mode, the DC side and the battery operate independently and the battery discharges.

[0159] 12. In battery discharge mode, the AC side and the battery operate independently and the battery discharges.

[0160] If the operating mode is cascaded H-bridge energy storage mode, the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery modules of the MMC-BESS subsystem are obtained, and power support is provided based on the AC side power surplus data and battery module status data of the MMC-BESS subsystem. As described in the above embodiment, since the DC conversion switch and grounding switch on the VSC side are open, there is no need to consider power support for the DC two-terminal or multi-terminal grids at this time. Only the energy conversion of the AC port of the MMC-BESS subsystem needs to be considered. Therefore, the need for charging or discharging the AC side can be determined based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery modules. In the above content, the load data and work can be obtained by obtaining the power curve of the external grid and obtaining the load data based on the power curve. Alternatively, the voltage and current of each grid end are collected, and power data is obtained based on the voltage and current. Then, combined with the preset linear relationship between load and power (power is inversely proportional to load), the load data or power surplus data is determined. In another embodiment, the load data can also be obtained by scheduling by on-site operators based on actual load conditions.

[0161] In the technical solution of the embodiment of the present application, different power balancing strategies are adopted for power balancing in each working mode, thereby realizing power balancing of the power system in the flexible direct current transmission mode, power balancing in the mode combining battery energy storage and flexible direct current transmission, and power balancing in the cascaded H-bridge mode, thereby achieving the effect of power balancing of a power system that meets the power requirements of multiple working scenarios.

[0162] In some embodiments, performing power balancing based on load data of the flexible direct current transmission subsystem and AC side power surplus data of the MMC-BESS subsystem includes:

[0163] If, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission subsystem requires power support and the AC side surplus power of the MMC-BESS subsystem meets the support conditions, the AC side surplus power of the MMC-BESS subsystem will be transmitted to the flexible direct current transmission subsystem through flexible direct current transmission for power balancing.

[0164] If, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission subsystem requires power support and the AC side surplus power of the MMC-BESS subsystem does not meet the support conditions, the AC side surplus power of the MMC-BESS subsystem will be transmitted to the flexible direct current transmission subsystem, and the battery module of the MMC-BESS subsystem will be controlled to provide discharge support to the flexible direct current transmission subsystem to achieve power balancing.

[0165] If, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission subsystem requires power support and the MMC-BESS subsystem does not have a power surplus, the battery module is controlled to provide discharge support to the flexible direct current transmission subsystem and the MMC-BESS subsystem to achieve power balancing.

[0166] In specific implementations, power balancing in a VSC+MMC-BESS dual-terminal or multi-terminal grid flexible direct current transmission mode can be accomplished by monitoring the load at both ends of the line in real time and, based on the load data of the flexible direct current transmission subsystem and the AC-side power surplus data of the MMC-BESS subsystem, determining the end requiring power support or having a power surplus. If the other end (including the flexible direct current transmission subsystem, i.e., the VSC end) requires power support and the AC power of the MMC-BESS subsystem is sufficient to support the other end, all battery cells of the MMC-BESS subsystem are opened, i.e., all switches SW3 are disconnected, and active and reactive power are transmitted to the end requiring power support via flexible direct current transmission. If the AC power of the MMC-BESS is insufficient to support the other end, battery cells that are capable of normal discharge, as monitored by the BMS, are activated to transmit the AC-side surplus power of the MMC-BESS subsystem (hereinafter referred to as the MMC-BESS end) to the flexible direct current transmission subsystem via flexible direct current transmission, and the battery modules of the MMC-BESS subsystem are controlled to discharge the power to support the flexible direct current transmission subsystem. If the VSC requires power support but the MMC-BESS does not have surplus power, the battery modules on the MMC-BESS are controlled to provide discharge support, closing switch 3. Once the battery is fully discharged, switch SW3 is opened, and the battery waits for charging. Once charging is complete, the battery waits for another discharge. If the VSC does not require power support and the load is light, resulting in a power surplus, while the AC load on the MMC-BESS is heavy and requires power support, the VSC mode is used to provide power support to the MMC-BESS via flexible direct current transmission. If the VSC experiences insufficient power support, the BMS detects dischargeable batteries and the transmission line provides power support. If the MMC-BESS has a surplus load and the other grids do not require power support, the transmission support mode is disabled, and the battery cells are charged directly via the AC power on the MMC-BESS. Switch SW3 on the fully charged battery cells is disconnected, placing them in hot standby mode.

[0167] In the technical solution of the embodiment of the present application, by comparing the load data of the flexible direct current electronic system and the AC side power surplus data of the MMC-BESS subsystem, corresponding measures are taken in a targeted manner to provide power support, thereby achieving power balance under various conditions.

[0168] In some embodiments, providing power support based on AC side power surplus data of the MMC-BESS subsystem and battery module status data includes:

[0169] If, based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module, it is determined that the MMC-BESS subsystem has AC side power surplus and the battery module is chargeable, the battery module is charged and placed in a hot standby state.

[0170] If it is determined that the AC side of the MMC-BESS subsystem requires power support based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module, the battery module is controlled to discharge the AC side of the MMC-BESS subsystem to achieve power balancing.

[0171] In specific implementation, in cascaded H-bridge energy storage mode, only energy conversion between the MMC-BESS DC and AC ports is considered. The BMS monitors the battery module's normal status and ability to charge and discharge. If the battery module is abnormal or unable to charge or discharge, switch SW3 on the battery module is turned off. If the battery module is normal and can charge and discharge, further measures are taken based on the AC-side power surplus data to achieve power balancing. Specifically, when there is surplus power on the AC side, the battery module is charged and placed in hot standby mode. If power support is required on the AC side, the battery module is controlled to discharge support to the AC side of the MMC-BESS subsystem to achieve power balancing.

[0172] In the technical solution of the embodiment of the present application, by monitoring the status of the battery modules, battery modules with abnormal status or unable to be charged and discharged can be screened out in time to ensure the normal operation of power balancing, and through the AC side power surplus data, the charging and discharging of the battery modules can be further controlled, so that power balancing can be completed quickly and reasonably.

[0173] In some embodiments, before charging the battery module, the process also includes: monitoring the SOC value of the battery module, sorting the battery modules according to the SOC value of the battery module, closing the first battery switch and the second battery switch of the sorted battery module in sequence, and then disconnecting the first battery switch, wherein the first battery switch includes a battery switch with a resistor, and the second switch includes a battery insertion and withdrawal switch.

[0174] Continuing with the above embodiment, when the battery module is in normal condition and can be charged and discharged, and there is a surplus of power on the AC side, the SOC value of the battery module can be monitored by the BMS system to obtain the SOC value of each normal battery module, and then the normal battery modules are sorted in descending order according to the SOC value. In the sorted order, the switches SW2 and SW3 of the normal battery modules are closed in sequence, and then the switch SW2 is opened. In another embodiment, as described in the above embodiment, the battery modules can also be sorted according to the SOS value, SOH value or other battery status parameters of each battery module, and the battery modules can also be sorted according to other voltages and powers. The details will not be repeated here, as long as the battery modules with good performance can be screened out. In other embodiments, the normal battery modules can also be sorted in ascending order according to the SOC value, which is not limited here.

[0175] In the technical solution of the embodiment of the present application, since the switch SW2 is a switch with resistance, it has the function of battery charging and discharging buffering. Therefore, before charging the battery module, the battery module is powered on and off in the above-mentioned manner, which can enable the battery module to smoothly transition between charging and discharging, thereby protecting the battery.

[0176] In some embodiments, before controlling the battery module to provide discharge support to the AC side of the MMC-BESS subsystem, the control further includes: monitoring the SOC value of the battery module, sorting the battery modules according to the SOC value of the battery module, closing the first battery switch and the second battery switch of the sorted battery module in sequence, and then disconnecting the first battery switch to provide power support to the AC side of the MMC-BESS subsystem, wherein the first battery switch includes a battery switch with a resistor, and the second switch includes a battery insertion and withdrawal switch.

[0177] Similarly, if the battery module is in normal condition and can be charged and discharged, and the AC side power needs to be supported, the SOC of the battery module monitored by the BMS can be used to close SW2 and then SW3 in sequence, and then disconnect SW2 to provide power support to the AC side.

[0178] In the technical solution of the embodiment of the present application, since the switch SW2 is a switch with resistance, it has the function of battery charging and discharging buffering. Therefore, before providing power support to the AC side power, the battery module is powered on and off in the above-mentioned manner, which can enable the battery module to smoothly transition between charging and discharging, protect the battery, and ensure orderly power support.

[0179] To explain the technical solution of the power balancing method of the power system of the present application in detail, the following will describe the entire power balancing solution in detail with reference to FIG7 and a specific embodiment. In this embodiment, the power balancing method of the power system includes the following steps:

[0180] Step 1: Obtain fault monitoring data of the flexible direct current transmission subsystem and the MMC-BESS subsystem.

[0181] In step 1-2, if it is determined that the MMC-BESS subsystem has a fault according to the fault monitoring data, the working mode is determined to be the flexible direct current transmission mode, and then step 2-2 is entered.

[0182] In step 1-4, if it is determined based on the fault monitoring data that neither the flexible direct current transmission subsystem nor the MMC-BESS subsystem has any faults, the operating mode is determined to be the flexible direct current transmission and battery energy storage power mode, and then the process goes to step 2-4.

[0183] In step 1-6, if it is determined according to the fault monitoring data that the flexible direct current transmission electronic system has a fault, the operating mode is determined to be the cascaded H-bridge energy storage mode, and then the process goes to step 2-6.

[0184] In step 2-2, if the working mode is the flexible direct current transmission mode, the battery module of the MMC-BESS subsystem is turned off to switch the power system to the flexible direct current transmission mode, and then the process goes to step 3-2.

[0185] In step 2-4, if the operating mode is flexible direct current transmission and battery energy storage mode, the battery status of the battery modules of the MMC-BESS subsystem is monitored, abnormal battery modules and normal battery modules are screened out, the abnormal battery modules are shut down, the SOC values ​​of the normal battery modules are monitored, the normal battery modules are sorted according to their SOC values, and the switches SW2 and SW3 of the sorted normal battery modules are closed in sequence, and then the switch SW2 is opened to switch the power system to flexible direct current transmission and battery energy storage mode, and then enter step 3-4.

[0186] In step 2-6, if the working mode is the cascade H-bridge energy storage mode, the loop of the flexible direct current electronic system is disconnected to switch the power system to the cascade H-bridge energy storage mode, and then proceed to step 3-6.

[0187] Step 3-2: If the working mode is the flexible direct current transmission mode, the external grid load data of the power system is obtained, and power balancing is performed based on the external grid load data.

[0188] Step 3-4: If the operating mode is flexible direct current transmission and battery energy storage mode, monitor the external grid load data, obtain the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem;

[0189] In step 3-4-2, if it is determined based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem that the flexible direct current transmission subsystem requires power support and the AC side surplus power of the MMC-BESS subsystem meets the support conditions, the AC side surplus power of the MMC-BESS subsystem is transmitted to the flexible direct current transmission subsystem via flexible direct current transmission for power balancing.

[0190] In step 3-4-4, if it is determined based on the load data of the flexible direct current transmission system and the AC side power surplus data of the MMC-BESS subsystem that the flexible direct current transmission system requires power support and the AC side surplus power of the MMC-BESS subsystem does not meet the support conditions, the AC side surplus power of the MMC-BESS subsystem is transmitted to the flexible direct current transmission system, and the battery modules of the MMC-BESS subsystem are controlled to provide discharge support to the flexible direct current transmission system for power balancing.

[0191] In step 3-4-6, if it is determined based on the load data of the flexible direct current transmission system and the AC side power surplus data of the MMC-BESS subsystem that the flexible direct current transmission system requires power support and the MMC-BESS subsystem does not have a power surplus, the battery module is controlled to provide discharge support to the flexible direct current transmission system and the MMC-BESS subsystem to achieve power balancing.

[0192] Step 3-6: If the operating mode is the cascade H-bridge energy storage mode, obtain the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module of the MMC-BESS subsystem;

[0193] Step 3-6-2: If, based on the AC side power surplus data of the MMC-BESS subsystem and the battery module status data, it is determined that the MMC-BESS subsystem has an AC side power surplus and the battery module is chargeable, the SOC values ​​of the battery modules are monitored, the battery modules are sorted according to their SOC values, and switches SW2 and SW3 of the sorted battery modules are closed in sequence, and then switch SW is opened to charge the battery modules and place the battery modules in a hot standby state.

[0194] In step 3-6-4, if it is determined that the AC side of the MMC-BESS subsystem requires power support based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery modules, the battery modules are sorted according to their SOC values, and switches SW2 and SW3 of the sorted battery modules are closed in sequence, and then switch SW is opened to control the battery modules to provide discharge support to the AC side of the MMC-BESS subsystem for power balancing.

[0195] It should be understood that, although the steps in the flowcharts of the above embodiments are shown in sequence as indicated by the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be performed in other orders. Moreover, at least a portion of the steps in the flowcharts of the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily to be performed in sequence, but can be performed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0196] Based on the same inventive concept, embodiments of the present application also provide a power balancing device for a power system for implementing the power balancing method for a power system involved above. The implementation solution provided by this device is similar to the implementation solution described in the above method. Therefore, the specific limitations of one or more power system power balancing device embodiments provided below can be found in the above-mentioned limitations of the power balancing method for a power system, and will not be repeated here.

[0197] In one embodiment, as shown in FIG8 , a power balancing device for a power system is provided, including: a controller 810 , and a power system 820 connected to the controller 810 , wherein the power system includes a VSC flexible direct current electronic system 822 and an MMC-BESS subsystem 824 ;

[0198] The controller is used to determine the working mode of the power system, perform switching control on the VSC flexible direct current electronic system 822 and the MMC-BESS subsystem 824, switch the power system 820 to the corresponding working mode, and perform power balancing according to the preset power balancing strategy corresponding to the working mode.

[0199] The power balancing device of the above-mentioned power system provides a power balancing solution for the power system including the flexible direct current transmission subsystem and the MMC-BESS subsystem. In the entire solution, the controller determines the working mode of the power system and switches the power system to the corresponding working mode, thereby realizing flexible switching of multiple working modes. In addition, power balancing is performed according to the preset power balancing strategy corresponding to each working mode, thereby realizing power balancing in multiple working modes such as flexible direct current transmission mode or flexible direct current transmission energy storage mode, thereby achieving power balancing for a power system that meets power requirements in multiple scenarios. While realizing power balancing of the power system, the flexibility of power balancing regulation is also improved, thereby improving the power system's ability to absorb and regulate power, and ensuring the power quality and power supply reliability of the power system.

[0200] In some embodiments, the controller 810 is further configured to obtain fault monitoring data of the VSCVSC flexible direct current transmission electronic system 822822 and the MMC-BESS subsystem 824, and determine the operating mode of the power system based on the fault monitoring data.

[0201] In some embodiments, the controller 810 is also used to determine that the operating mode is the cascade H-bridge energy storage mode if it is determined according to the fault monitoring data that the VSC flexible direct current transmission subsystem 822 has a fault; if it is determined according to the fault monitoring data that the MMC-BESS subsystem 824 has a fault, then the operating mode is determined to be the flexible direct current transmission mode; if it is determined according to the fault monitoring data that neither the VSC flexible direct current transmission subsystem 822 nor the MMC-BESS subsystem 824 has a fault, then the operating mode is determined to be the flexible direct current transmission and battery energy storage power mode.

[0202] In some embodiments, the controller 810 is also used to control the switching of the battery module of the MMC-BESS subsystem 824 and the VSC flexible direct current electronic system 822 according to a preset mode switching strategy corresponding to the determined working mode, so as to switch the power system to the corresponding working mode.

[0203] In some embodiments, the controller 810 is also used to, if the operating mode is the flexible direct current transmission mode, shut down the battery module of the MMC-BESS subsystem 824 to switch the power system to the flexible direct current transmission mode; if the operating mode is the flexible direct current transmission and battery energy storage mode, monitor the battery status of the battery module of the MMC-BESS subsystem 824, screen out abnormal battery modules and normal battery modules, shut down the abnormal battery modules, and power on and off the normal battery modules to switch the power system to the flexible direct current transmission and battery energy storage mode; if the operating mode is the cascaded H-bridge energy storage mode, disconnect the loop of the VSC flexible direct current transmission subsystem 822 to switch the power system to the cascaded H-bridge energy storage mode.

[0204] In some embodiments, the controller 810 is also used to monitor the battery status parameters of normal battery modules, sort the normal battery modules according to the battery status parameters of the normal battery modules, and perform power on and off operations on the sorted normal battery modules in sequence according to a preset control strategy.

[0205] In some embodiments, the controller 810 is further configured to sequentially close the first battery switch and the second battery switch of the normal battery module after sorting, and then disconnect the first battery switch. The first battery switch includes a battery switch with a resistor, and the second switch includes a battery insertion / withdrawal switch.

[0206] In some embodiments, the controller 810 is also used to obtain the external grid load data of the power system if the working mode is the flexible direct current transmission mode, and perform power balancing based on the external grid load data; if the working mode is the flexible direct current transmission and battery energy storage mode, monitor the external grid load data, obtain the load data of the VSC flexible direct current transmission subsystem 822 and the AC side power surplus data of the MMC-BESS subsystem 824, and perform power balancing based on the load data of the VSC flexible direct current transmission subsystem 822 and the AC side power surplus data of the MMC-BESS subsystem 824; if the working mode is the cascaded H-bridge energy storage mode, obtain the AC side power surplus data of the MMC-BESS subsystem 824 and the status data of the battery module of the MMC-BESS subsystem 824, and perform power support based on the AC side power surplus data of the MMC-BESS subsystem 824 and the status data of the battery module.

[0207] In some embodiments, the controller 810 is further configured to, if it is determined based on the load data of the VSC flexible direct current transmission electronic system 822 and the AC side power surplus data of the MMC-BESS subsystem 824 that the VSC flexible direct current transmission electronic system 822 needs power support and the AC side surplus power of the MMC-BESS subsystem 824 meets the support conditions, transmit the AC side surplus power of the MMC-BESS subsystem 824 to the VSC flexible direct current transmission electronic system 822 through flexible direct current transmission for power balancing; if it is determined based on the load data of the VSC flexible direct current transmission electronic system 822 and the AC side power surplus data of the MMC-BESS subsystem 824 that the VSC flexible direct current transmission electronic system 822 needs power support and the MMC-BESS subsystem 824 meets the support conditions, transmit the AC side surplus power of the MMC-BESS subsystem 824 to the VSC flexible direct current transmission electronic system 822 through flexible direct current transmission for power balancing; 4 does not meet the support conditions, the AC side surplus power of the MMC-BESS subsystem 824 is transmitted to the VSC flexible direct current transmission electronic system 822, and the battery module of the MMC-BESS subsystem 824 is controlled to perform discharge support on the VSC flexible direct current transmission electronic system 822 to achieve power balancing; if it is determined that the VSC flexible direct current transmission electronic system 822 needs power support and the MMC-BESS subsystem 824 does not have a power surplus based on the load data of the VSC flexible direct current transmission electronic system 822 and the AC side power surplus data of the MMC-BESS subsystem 824, the battery module is controlled to perform discharge support on the VSC flexible direct current transmission electronic system 822 and the MMC-BESS subsystem 824 to achieve power balancing.

[0208] In some embodiments, the controller 810 is further configured to charge the battery module and place the battery module in a hot standby state if it is determined, based on the AC side power surplus data of the MMC-BESS subsystem 824 and the status data of the battery module, that the MMC-BESS subsystem 824 has an AC side power surplus and the battery module is rechargeable; and to control the battery module to provide discharge support to the AC side of the MMC-BESS subsystem 824 for power balancing if it is determined, based on the AC side power surplus data of the MMC-BESS subsystem 824 and the status data of the battery module, that the AC side of the MMC-BESS subsystem 824 requires power support.

[0209] Each module in the power balancing device for the power system described above may be implemented in whole or in part through software, hardware, or a combination thereof. Each module may be embedded in or independent of a processor in a computer device in hardware form, or may be stored in a memory in the computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0210] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as shown in FIG9 . The computer device includes a processor, a memory, and a network interface connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store data such as fault monitoring data, load data, and battery status monitoring data of the power system. The network interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, a power balancing method for a power system is implemented.

[0211] Those skilled in the art will understand that the structure shown in Figure 9 is merely a block diagram of a portion of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0212] In one embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the power balancing method of the power system when executing the computer program.

[0213] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the power balancing method of the power system are implemented.

[0214] In one embodiment, a computer program product is provided, comprising a computer program, which implements the steps in the above-mentioned power balancing method for a power system when executed by a processor.

[0215] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0216] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0217] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0218] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A power balancing method for an electric power system, characterized in that: The power system includes a flexible direct current transmission subsystem and an MMC-BESS subsystem; The power balancing method of the power system includes: determining an operating mode of the power system; Switching the power system to a corresponding operating mode; Power balancing is performed according to a preset power balancing strategy corresponding to the operating mode.

2. The method according to claim 1, characterized in that Determining the operating mode of the power system includes: Obtain fault monitoring data of the flexible direct current transmission subsystem and the MMC-BESS subsystem; An operating mode of the power system is determined according to the fault monitoring data.

3. The method according to claim 2, characterized in that Determining the operating mode of the power system according to the fault monitoring data includes: If it is determined according to the fault monitoring data that the flexible direct current transmission electronic system has a fault, then the operating mode is determined to be a cascaded H-bridge energy storage mode; Alternatively, if it is determined according to the fault monitoring data that the MMC-BESS subsystem has a fault, determining that the operating mode is a flexible direct current transmission mode; Alternatively, if it is determined according to the fault monitoring data that neither the flexible direct current transmission subsystem nor the MMC-BESS subsystem has any fault, the operating mode is determined to be the flexible direct current transmission and battery energy storage power mode.

4. The method according to claim 3, characterized in that Switching the power system to a corresponding operating mode includes: According to the preset mode switching strategy corresponding to the determined working mode, the battery module of the MMC-BESS subsystem and the flexible direct current transmission electronic system are switched on and off to switch the power system to the corresponding working mode.

5. The method according to claim 4, characterized in that The switching control of the battery module of the MMC-BESS subsystem and the flexible direct current transmission subsystem according to the preset mode switching strategy corresponding to the determined working mode to switch the power system to the corresponding working mode includes: If the operating mode is the flexible direct current transmission mode, shutting down the battery module of the MMC-BESS subsystem to switch the power system to the flexible direct current transmission mode; Alternatively, if the operating mode is the flexible direct current transmission and battery energy storage mode, the battery status of the battery modules of the MMC-BESS subsystem is monitored, abnormal battery modules and normal battery modules are screened out, the abnormal battery modules are shut down, and the normal battery modules are powered on and off to switch the power system to the flexible direct current transmission and battery energy storage mode; Alternatively, if the operating mode is the cascade H-bridge energy storage mode, the loop of the flexible direct current electronic system is disconnected to switch the power system to the cascade H-bridge energy storage mode.

6. The method according to claim 5, characterized in that The method further comprises: If a battery module of the MMC-BESS subsystem fails, identifying a fault type of the failed battery module; Based on the identified fault type, the corresponding BMS control strategy is called to perform fault analysis and processing.

7. The method according to claim 5, characterized in that The powering on and off operations on the normal battery module include: Monitoring the battery status parameters of the normal battery modules; sorting the normal battery modules according to the battery status parameters of the normal battery modules; According to the preset control strategy, the normal battery modules after sorting are powered on and off in sequence.

8. The method according to claim 7, characterized in that The step of sequentially powering on and off the sorted normal battery modules according to the preset control strategy includes: The first battery switch and the second battery switch of the normal battery module after sorting are closed in sequence, and then the first battery switch is opened. The first battery switch includes a battery switch with a resistor, and the second switch includes a battery switching switch.

9. The method according to any one of claims 3 to 7, characterized in that The performing power balancing according to the preset power balancing strategy corresponding to the working mode includes: If the working mode is the flexible direct current transmission mode, obtaining external power grid load data of the power system, and performing power balancing according to the external power grid load data; If the operating mode is the flexible direct current transmission and battery energy storage mode, monitoring the external power grid load data, obtaining the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, and performing power balancing according to the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem; If the working mode is the cascade H-bridge energy storage mode, the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module of the MMC-BESS subsystem are obtained, and power support is performed according to the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module.

10. The method according to claim 8, characterized in that The performing of power balancing according to the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem includes: If, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission subsystem requires power support and the AC side surplus power of the MMC-BESS subsystem meets the support conditions, the AC side surplus power of the MMC-BESS subsystem is transmitted to the flexible direct current transmission subsystem via flexible direct current transmission to perform power balancing; If, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission subsystem requires power support and the AC side surplus power of the MMC-BESS subsystem does not meet the support conditions, the AC side surplus power of the MMC-BESS subsystem is transmitted to the flexible direct current transmission subsystem, and the battery modules of the MMC-BESS subsystem are controlled to discharge the flexible direct current transmission subsystem to achieve power balancing; If, based on the load data of the flexible direct current transmission subsystem and the AC side power surplus data of the MMC-BESS subsystem, it is determined that the flexible direct current transmission subsystem requires power support and the MMC-BESS subsystem does not have a power surplus, the battery module is controlled to provide discharge support to the flexible direct current transmission subsystem and the MMC-BESS subsystem to achieve power balancing.

11. The method according to claim 9, characterized in that The performing of power support according to the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module includes: If it is determined, based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module, that the MMC-BESS subsystem has an AC side power surplus and the battery module is chargeable, charging the battery module and placing the battery module in a hot standby state; If it is determined that the AC side of the MMC-BESS subsystem needs power support based on the AC side power surplus data of the MMC-BESS subsystem and the status data of the battery module, the battery module is controlled to perform discharge support on the AC side of the MMC-BESS subsystem to achieve power balancing.

12. The method according to claim 11, characterized in that Before charging the battery module, the method further includes: monitoring battery status parameters of the battery module; sorting the battery modules according to the battery status parameters of the battery modules; The first battery switch and the second battery switch of the sequenced battery module are closed in sequence, and then the first battery switch is opened, wherein the first battery switch includes a battery switch with a resistor, and the second switch includes a battery insertion and removal switch.

13. The method according to claim 11, characterized in that Before controlling the battery module to provide discharge support to the AC side of the MMC-BESS subsystem, the method further includes: monitoring battery status parameters of the battery module; sorting the battery modules according to the battery status parameters of the battery modules; The first battery switch and the second battery switch of the sequenced battery module are closed in sequence, and the first battery switch is then opened to provide power support to the AC side of the MMC-BESS subsystem. The first battery switch includes a battery switch with a resistor, and the second switch includes a battery switching switch.

14. A power balancing device for an electric power system, characterized in that: The device includes: a controller, and a power system connected to the controller, wherein the power system includes a VSC flexible direct current transmission electronic system and an MMC-BESS subsystem; The controller is used to determine the operating mode of the power system, perform switching control on the VSC flexible direct current transmission electronic system and the MMC-BESS subsystem, switch the power system to the corresponding operating mode, and perform power balancing according to a preset power balancing strategy corresponding to the operating mode.

15. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 13 are implemented.

16. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 13 are implemented.

17. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 13 are implemented.

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