A charging control method and system applied to a static synchronous compensator system

Abstract

The present application relates to a charging control method applied to a static synchronous compensator system. The charging control method includes controlling the DC-side voltage of the MMC converter to rise to a preset system startup voltage value according to a first preset manner to charge at least two supercapacitor modules in a first supercapacitor charging stage. In the first supercapacitor charging stage, it is detected whether the supercapacitor module voltage values of at least two supercapacitor modules are higher than a preset voltage limit value. In the case that there is a supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit value, the bypass switch of the supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit value is controlled to close to bypass the supercapacitor module with a voltage higher than the preset voltage limit value. In the case that the first supercapacitor charging stage ends, the DC-side voltage of the MMC converter is controlled to rise to a preset charging voltage value according to a second preset manner to charge at least two supercapacitor modules in a second supercapacitor charging stage until it is detected that all at least two supercapacitor modules are charged.

Description

Technical Field

[0001] The present application relates to the field of static synchronous compensators, and in particular to a charging control method and system applied to a static synchronous compensator system. Background Art

[0002] A static synchronous compensator is a dynamic reactive power compensation device based on grid-forming control technology and is widely used in a new power system mainly based on new energy. The static synchronous compensator has the characteristics of a self-synchronous voltage source and can provide inertia and voltage support to the system, thereby solving problems such as transient low voltage, overvoltage, and broadband oscillation in a new power system mainly based on new energy.

[0003] A static synchronous compensator consists of an MMC (Modular Multilevel ConverterQ, modular multilevel converter, hereinafter referred to as an MMC converter) and a supercapacitor branch (hereinafter referred to as a supercap branch).

[0004] The MMC converter can perform the conversion between alternating current and direct current, including the DC side and the AC side. The DC side of the MMC converter is connected to the supercap branch.

[0005] The MMC converter usually includes a plurality of arms, and a arm reactor and a plurality of commutation sub-modules (Sub-module, hereinafter referred to as SM) are correspondingly arranged on each arm. For example, a typical three-phase MMC converter is composed of six arms, and a plurality of sub-modules and an arm inductor are arranged on each arm.

[0006] The supercap branch usually includes a plurality of supercap sub-modules and a plurality of supercapacitors. Among them, the supercap sub-module is a half-bridge sub-module. A small capacitor is included in the half-bridge sub-module. The supercapacitor is connected in parallel with the small capacitor through a maintenance switch.

[0007] Before the static synchronous compensator operates, it is necessary to charge the MMC converter and the supercap branch, and charge the voltages of the commutation sub-modules of the MMC converter and the supercap sub-modules and supercapacitors of the supercap branch to the corresponding rated voltages respectively, so that the static synchronous compensator can operate normally.

[0008] However, the inventors found that in the case of charging the supercap branch in the prior art, if the maintenance switch between the supercapacitor and the supercap sub-module is disconnected due to improper manual operation or other reasons, then during the charging process of the supercap branch, only the small capacitor will charge the supercap sub-module, resulting in the voltage value of the supercap sub-module being much higher than the normal voltage value, and further causing damage to the supercap sub-module. Summary of the Invention

[0009] This application aims to provide a charging control method and system for a static synchronous compensator system.

[0010] According to one aspect of the present application, a charging control method for a static synchronous compensator system is proposed. The static synchronous compensator system includes an MMC converter and a supercapacitor branch. The DC side of the MMC converter is connected to the supercapacitor branch. The supercapacitor branch includes at least two supercapacitor modules and a bypass switch corresponding to each supercapacitor module. The at least two supercapacitor modules are connected in series, and both ends of the bypass switch are respectively connected to both ends of the supercapacitor module. Each supercapacitor module includes a supercapacitor, a supercapacitor sub-module, and a maintenance switch.

[0011] The charging control method includes: controlling the DC side voltage of the MMC converter to rise to a preset system startup voltage value according to a first preset method to charge at least two supercapacitor modules in a first supercapacitor charging stage. In the first supercapacitor charging stage, detecting whether the supercapacitor module voltage values of at least two supercapacitor modules are higher than a preset voltage limit value. In the case where there is a supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit value, controlling the bypass switch of the supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit value to close to bypass the supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit value. At the end of the first supercapacitor charging stage, controlling the DC side voltage of the MMC converter to rise to a preset charging voltage value according to a second preset method to charge at least two supercapacitor modules in a second supercapacitor charging stage until it is detected that at least two supercapacitor modules are all charged.

[0012] According to another aspect of the present application, a static synchronous compensator system is proposed. The static synchronous compensator system includes: an MMC converter; a supercapacitor branch connected to the DC side of the MMC converter; the supercapacitor branch includes at least two supercapacitor modules and a bypass switch corresponding to each supercapacitor module. The at least two supercapacitor modules are connected in series, and both ends of the bypass switch are respectively connected to both ends of the supercapacitor module. Each supercapacitor module includes a supercapacitor, a supercapacitor sub-module, and a maintenance switch. A charging control device for executing the above charging control method.

[0013] According to another aspect of the present application, a charging control device applied to a static synchronous compensator system is proposed. The charging control device includes a first supercapacitor charging stage control module, a first supercapacitor charging stage detection module, and a second supercapacitor charging stage control module. The first supercapacitor charging stage control module is used to control the DC side voltage of the MMC converter to rise to a preset system startup voltage value in a first preset manner, so as to charge at least two supercapacitor modules in the first supercapacitor charging stage; the first supercapacitor charging stage detection module is used to detect whether the supercapacitor module voltage values of at least two supercapacitor modules are higher than a preset detection value during the first supercapacitor charging stage; and in the case that there is a supercapacitor module with a supercapacitor module voltage value higher than a preset voltage limit value, control the bypass switch of the supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit value to close, so as to bypass the supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit value; the second supercapacitor charging stage control module is used to control the DC side voltage of the MMC converter to rise to a preset charging voltage value in a second preset manner in the case that the first supercapacitor charging stage ends, so as to charge at least two supercapacitor modules in the second supercapacitor charging stage until it is detected that each supercapacitor module is fully charged.

[0014] According to another aspect of the present application, a charging control device is proposed. The charging control device includes: one or more processors; a storage device for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the method as described above.

[0015] According to another aspect of the present application, a non-volatile computer-readable medium is proposed, on which a computer program is stored, and when the program is executed by a processor, the method as described above is implemented.

[0016] According to another aspect of the present application, a computer program product is proposed. The computer program product includes a computer program stored on a computer-readable storage medium, and the computer program includes program instructions, and when the program instructions are executed by a computer, the method as described above is implemented.

[0017] Beneficial effects

[0018] The MMC converter is used to charge the supercapacitor branch in the first supercapacitor charging stage and the second supercapacitor charging stage, and during the first supercapacitor charging stage, continuously detect whether the supercapacitor module voltage values of each supercapacitor module reach the preset voltage limit value to detect whether the maintenance switch of each supercapacitor module is closed. And in the case that it is detected that there is a supercapacitor module with an unclosed maintenance switch, close the bypass switch of the supercapacitor module for bypass processing. This is equivalent to short-circuiting the supercapacitor module, so that the supercapacitor module no longer participates in charging, thereby reducing the probability that the supercapacitor module with an unclosed maintenance switch is damaged due to excessive voltage. Description of the drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0020] Figure 1 It is a schematic diagram of the system structure of the static synchronous compensator system in the embodiments of the present application;

[0021] Figure 2 It is a schematic diagram of the circuit structure of the super-capacitor branch in the embodiments of the present application;

[0022] Figure 3 It is a flowchart of the steps of the charging control method in the embodiments of the present application;

[0023] Figure 4 It is a schematic diagram of the process of step S310 in the embodiments of the present application;

[0024] Figure 5 It is a schematic diagram of the process of the second super-capacitor charging stage in the embodiments of the present application;

[0025] Figure 6 It is a schematic diagram of the process of step S326 in the embodiments of the present application;

[0026] Figure 7 It is a schematic diagram of the process of removing a faulty super-capacitor module in the second super-capacitor charging stage in the embodiments of the present application;

[0027] Figure 8 It is a schematic diagram of the circuit structure of the full-bridge commutation sub-module in the embodiments of the present application;

[0028] Figure 9 It is a schematic diagram of the circuit structure of the half-bridge commutation sub-module in the embodiments of the present application;

[0029] Figure 10 It is a schematic diagram of the process of charging the MMC converter in the embodiments of the present application;

[0030] Figure 11 It is a schematic diagram of the process of step S1070 in the embodiments of the present application;

[0031] Figure 12 It is a block diagram of the charging control device in the embodiments of the present application;

[0032] Figure 13 It is a schematic diagram of the electronic device in the embodiments of the present application.

[0033] Description of the reference numerals:

[0034] 1. MMC converter; 11. Converter sub-module; 81. First full-bridge switching device; 82. Second full-bridge switching device; 83. Third full-bridge switching device; 84. Fourth full-bridge switching device; 85. Full-bridge capacitor; 91. First half-bridge switching device; 92. Second half-bridge switching device; 93. Half-bridge capacitor; 2. Supercapacitor branch; 21. Supercapacitor module; 211. Supercapacitor; 212. Supercapacitor sub-module; 2121. First switching device; 2122. Second switching device; 2123. Parallel small capacitor; 213. Maintenance switch; 22. Bypass switch; 3. DC-side switch; 4. AC circuit breaker; 5. Starting circuit; 51. Starting resistor; 52. Starting switch; 1201. First supercapacitor charging stage control module; 1202. First supercapacitor charging stage detection module; 1203. Second supercapacitor charging stage control module; 1301. Processor; 1302. Bus; 1303. Memory; 1304. Transceiver. Detailed implementation manners

[0035] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar parts, and thus their repetitive description will be omitted.

[0036] The features, structures or characteristics described may be combined in one or more embodiments in any suitable manner. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present disclosure. However, those skilled in the art will realize that the technical solutions of the present disclosure can be practiced without one or more of these specific details, or can be implemented in other ways, components, materials, devices, etc. In these cases, well-known structures, methods, devices, implementations, materials or operations will not be shown or described in detail.

[0037] In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0038] The terms "first", "second", etc. in the description and claims of this application and the above drawings are used to distinguish different objects, rather than to describe a specific order.

[0039] The technical solutions of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0040] According to one aspect of the present application, an embodiment of the present application provides a charging control method applied to a static synchronous compensator system.

[0041] Figure 1 Fig. shows a structural example of a static synchronous compensator system. Referring to Figure 1 , the static synchronous compensator system includes at least one MMC converter 1 and at least one ultracapacitor branch 2. The DC side of each MMC converter 1 is connected to at least one ultracapacitor branch 2.

[0042] It should be noted that when the MMC converter 1 is connected to at least two ultracapacitor branches 2, the at least two ultracapacitor branches 2 are connected in parallel to the DC side of the MMC converter 1. Exemplarily, Figure 1 shows the case where one MMC converter 1 is connected to two ultracapacitor branches 2.

[0043] Figure 2 Fig. shows the circuit structure of the ultracapacitor module 21 and the bypass switch 22. According to the exemplary embodiment, as Figure 1 and Figure 2 shown, each ultracapacitor branch 2 includes at least two ultracapacitor modules 21 and a bypass switch 22 corresponding to each ultracapacitor module 21. The at least two ultracapacitor modules 21 are cascaded, and the bypass switch 22 is connected in parallel with the ultracapacitor module 21, that is, both ends of the bypass switch 22 are respectively connected to both ends of the ultracapacitor module 21. When the bypass switch 22 is closed, the ultracapacitor module 21 will be short-circuited.

[0044] Referring to Figure 2 , each ultracapacitor module 21 includes a supercapacitor 211, an ultracapacitor sub-module 212, and a maintenance switch 213. The ultracapacitor sub-module 212 is a half-bridge structure, specifically including a first switching device 2121, a second switching device 2122, and a parallel small capacitor 2123. The supercapacitor 211 is connected in parallel with the parallel small capacitor 2123 through the maintenance switch 213.

[0045] Figure 3 Fig. shows the flow of the charging control method in the embodiment of the present application. The charging control method is executed by a charging control device. Referring to Figure 3 , the charging control method includes step S310 - step S340.

[0046] In step S310, the charging control device controls the DC-side voltage of the MMC converter to rise to a preset system startup voltage value in a first preset manner to perform charging in the first over-capacity charging stage.

[0047] According to the exemplary embodiment, in step S310, the charging control device controls the DC-side output of the MMC converter to output a DC-side voltage to charge the over-capacity module and the supercapacitor in the first over-capacity charging stage.

[0048] According to the exemplary embodiment, the first preset manner may specifically be that the charging control device controls the MMC converter to increase the DC-side voltage to a first preset voltage value in a manner of increasing the preset value per unit time (i.e., at a fixed boosting speed), and then after a preset duration, further increase the DC-side voltage from the first preset voltage value to the preset system startup voltage value at a fixed boosting speed and maintain it unchanged for a second preset duration.

[0049] The first preset manner may also be that the charging control device directly controls the MMC converter to continuously increase the DC-side voltage to the preset startup voltage value at a fixed boosting speed, or controls the MMC converter to increase the DC-side voltage step by step to the preset startup voltage value, which is not limited herein.

[0050] According to the exemplary embodiment, the preset system startup voltage value may be the voltage value required for the central control board and the control system of the over-capacity module to operate normally.

[0051] The central control board and the control system of the over-capacity module need to communicate and transmit data normally when the voltage is at the preset system startup voltage value.

[0052] Therefore, in step S310 of the embodiment of the present application, the charging control device first controls the MMC converter to perform charging in the first over-capacity charging stage to first charge the voltage of the over-capacity module to a level where the central control board and the control system can operate and communicate normally.

[0053] It should be noted that the preset system voltage value is set by the user and can be adjusted adaptively according to the situation.

[0054] In step S320, in the first over-capacity charging stage, the charging control device detects whether the over-capacity module voltage values of at least two over-capacity modules reach the preset voltage limit.

[0055] According to the exemplary embodiment, in step S320, during the process of the charging control device controlling the MMC converter to charge the over-capacity module in the first over-capacity charging stage, it continuously detects whether the module voltage value of each over-capacity module reaches the preset voltage limit.

[0056] When the module voltage value of the module without a supercapacitor module is higher than or equal to the preset voltage limit value, it means that there is no supercapacitor module with an unclosed maintenance switch. The charging control device then continues to monitor whether the module voltage value of a supercapacitor module reaches the preset voltage limit value until the end of the first supercapacitor charging stage or until it is detected that the module voltage value of a supercapacitor module reaches the preset voltage limit value.

[0057] When the module voltage value of a supercapacitor module is higher than or equal to the preset voltage limit value, it means that there is a supercapacitor module with an unclosed maintenance switch.

[0058] In step S330, when there is a supercapacitor module whose module voltage value reaches the preset voltage limit value, the charging control device controls the maintenance switch of the supercapacitor module with a module voltage value higher than the preset voltage limit value to close.

[0059] According to the exemplary embodiment, in step S330, when there is a supercapacitor module whose module voltage value reaches the preset voltage limit value, it means that the maintenance switch of the supercapacitor module is not closed. Therefore, the charging control device can control the bypass switch of the supercapacitor module with the unclosed maintenance switch to close, so as to perform bypass processing on the supercapacitor module with the unclosed maintenance switch, so that the supercapacitor module with the unclosed maintenance switch no longer participates in subsequent charging, thereby reducing the probability of damage to the supercapacitor module caused by the continuous charging of the supercapacitor module with the maintenance switch not correctly connected.

[0060] And after controlling the maintenance switch to close in the first supercapacitor charging stage, the charging control device continues to detect whether the module voltage value of a supercapacitor module reaches the preset voltage limit value until the end of the first supercapacitor charging stage.

[0061] It should be noted that the preset voltage limit value is set by the user himself. The preset voltage limit value can be a certain value or can be determined according to the voltage value of the real-time DC side voltage.

[0062] Exemplarily, the preset voltage limit value can be the ratio of the DC side voltage to the number of supercapacitor modules multiplied by k. In the case of a higher DC side voltage, the preset voltage limit value is also higher.

[0063] In step S340, when the first supercapacitor charging stage ends, the charging control device controls the DC side voltage of the MMC converter to rise to the preset charging voltage value in a second preset manner to charge at least two supercapacitor modules in the second supercapacitor charging stage until it is detected that at least two supercapacitor modules are all charged.

[0064] According to the exemplary embodiment, after the end of the first ultra-capacitor charging stage, the ultra-capacitor modules that are not normally connected to the maintenance switch have been bypassed. At this time, charging can continue for the normal ultra-capacitor modules without damaging any ultra-capacitor modules. Therefore, in step S340, when the first ultra-capacitor charging is completed, the charging control device starts to charge the ultra-capacitor modules for the second ultra-capacitor charging stage.

[0065] In the second ultra-capacitor charging stage, the bypassed ultra-capacitor modules will no longer participate in the charging process, and only the connected ultra-capacitor modules will be charged. When it is detected that the charging of each connected ultra-capacitor module is completed, the second ultra-capacitor charging stage ends.

[0066] According to the exemplary embodiment, in step S340, in the second ultra-capacitor charging stage, the charging control device raises the DC side voltage of the MMC converter from the preset system startup voltage value to the preset charging voltage value, and keeps it unchanged after reaching the preset charging voltage value until it is detected that the charging of each connected ultra-capacitor module is completed, and the second ultra-capacitor charging stage ends.

[0067] According to the exemplary embodiment, the second preset method can specifically be to control the DC side voltage of the MMC converter to rise from the preset system startup voltage value to the preset charging voltage value at a fixed boosting speed.

[0068] According to the exemplary embodiment, the preset charging voltage value can specifically be set by the user according to the rated voltage value of the DC side voltage in the actual project. For example, when the rated voltage value is 30 kV, the preset charging voltage value can be set to 30 kV.

[0069] According to the exemplary embodiment, the way for the charging control device to detect whether the charging of the ultra-capacitor module is completed can be to detect whether the ultra-capacitor module voltage value of the ultra-capacitor module reaches the rated voltage (or 95% of the rated voltage). When the rated voltage is reached, it indicates that the charging of the ultra-capacitor module is completed.

[0070] Through the above embodiments, the MMC converter is used to charge the ultra-capacitor branch for the first ultra-capacitor charging stage and the second ultra-capacitor charging stage. And during the first ultra-capacitor charging stage, continuously detect whether the ultra-capacitor module voltage value of each ultra-capacitor module reaches the preset voltage limit value to detect whether the maintenance switch of each ultra-capacitor module is closed. And when it is detected that there is an ultra-capacitor module with an unclosed maintenance switch, close the bypass switch corresponding to the ultra-capacitor module to bypass the ultra-capacitor module with the unclosed maintenance switch, so that the bypass module with the unclosed maintenance switch no longer participates in the subsequent charging process, which can reduce the probability of damage to the bypass module with the unclosed maintenance switch due to charging.

[0071] According to some embodiments, referring to Figure 4, in the above step S310, the charging control device controls the DC-side voltage of the MMC converter to increase to the preset system startup voltage value according to the first preset method, so as to charge at least two ultracapacitor modules in the first ultracapacitor charging stage, which can be specifically implemented through steps S311 - S315.

[0072] In step S311, the charging control device controls the DC-side voltage of the MMC converter to increase to the preset module startup voltage value at the first preset voltage increase rate, so as to start the charging in the first ultracapacitor charging stage.

[0073] According to the exemplary embodiment, in step S311, the charging control device controls the DC-side voltage of the MMC converter to increase to the preset module startup voltage value.

[0074] The setting of the preset module startup voltage value needs to ensure that when the DC-side voltage reaches the preset module startup voltage value, if there is an ultracapacitor module not connected to the maintenance switch, this ultracapacitor module can start and establish communication with the charging control device. And the preset module startup voltage value should not be higher than the maximum voltage that a single ultracapacitor module can withstand.

[0075] In step S311, the charging control device first controls the DC-side voltage of the MMC converter to increase to the preset module startup voltage value, and then increases it to the preset system startup voltage value.

[0076] Exemplarily, in step S311, the charging control device can control the switching devices inside the MMC converter to turn on or off, so as to adjust the DC-side voltage value of the MMC converter, so that the DC-side voltage increases to the preset module startup voltage value at the first preset voltage increase rate.

[0077] Exemplarily, in step S311, the DC-side voltage increasing to the preset module startup voltage value at the first preset voltage increase rate can be: the DC-side voltage starts from 0 and increases to 50V after 5 seconds in the way of increasing 10V per second (the first preset voltage increase rate is 10V / s).

[0078] In step S312, the charging control device starts timing the first duration, and the first duration is the duration when the DC-side voltage remains at the preset module startup voltage value.

[0079] In step S313, when the charging control device detects that the first duration reaches the first preset duration, it controls the DC-side voltage of the MMC converter to increase to the preset system startup voltage value at the second preset voltage increase rate.

[0080] In step S314, the charging control device starts timing the second duration, and the second duration is the duration when the DC-side voltage remains at the preset system startup voltage value;

[0081] In step S315, when the charging control device detects that the second duration reaches the second preset duration, it ends the charging of the first over-capacity charging stage.

[0082] According to the exemplary embodiment, in steps S311 to S315, the charging control device starts to charge in the first over-capacity charging stage, raises the DC-side voltage from 0V to the preset module startup voltage value, and then maintains the DC-side voltage at the preset module startup voltage value.

[0083] When the duration for which the charging control device maintains the DC-side voltage at the preset module startup voltage value reaches the first preset duration (i.e., when the first duration reaches the first preset duration), it controls the DC-side voltage of the MMC converter to continue to rise on the basis of the preset module startup voltage value and rise to the preset system startup voltage value at the second preset boosting speed.

[0084] After that, the charging control device then controls the DC-side voltage to remain unchanged at the preset system startup voltage value until the duration for which the DC-side voltage value is maintained at the preset system startup voltage value reaches the second preset duration (i.e., when the second duration reaches the second preset duration), so as to end the charging of the first over-capacity charging stage.

[0085] According to some embodiments, the preset system startup voltage value is determined according to the first startup voltage value of the central control board of the over-capacity module, the second startup voltage value of the management system of the over-capacity module, and the third startup voltage value of the management system.

[0086] The first startup voltage value is the voltage value required for the central control board to power on and start. The second startup voltage value is the voltage value required for the management system to power on and start. The central control board can respond to the instructions of the management system to control the over-capacity module. And the central control board and the management system need to meet certain voltage requirements when powering on and starting. That is, the voltage value of the over-capacity module should reach the first startup voltage value and the second startup voltage value so that the management system and the central control board can be normally started and communicate.

[0087] The third startup voltage value is the voltage value required for the management system to implement the function of accurately identifying faults and can be determined according to the startup setting value for the management system to judge faults.

[0088] The management system can identify whether there is an abnormality in the over-capacity module. When it detects an abnormality, it will disconnect the maintenance switch. However, when the voltage of the over-capacity module does not reach the third startup voltage value, the fault identification ability of the management system is poor, and the situation of mis-tripping the maintenance switch may occur.

[0089] Therefore, in the first ultra-capacitor charging stage, the charging control device first raises the DC side voltage to the preset system startup voltage value to ensure that the central control board and the ultra-capacitor management system can be powered on and started, and at this time, the management system will not mis-trip the maintenance switch.

[0090] It should be noted that during the charging process of the ultra-capacitor branch, the charging control device needs to control both turn-off switch devices (i.e., the first switch device and the second switch device) of each ultra-capacitor module to be in the off state, so that each ultra-capacitor module remains in the locked state.

[0091] According to some embodiments, Figure 5 shows the step flow of the charging control device controlling the MMC converter to perform the second ultra-capacitor charging stage. Refer to Figure 5 , in the above step S320, the charging control device controls the DC side voltage of the MMC converter to rise to the preset charging voltage value according to the second preset method to charge at least two ultra-capacitor modules in the second ultra-capacitor charging stage until it is detected that each ultra-capacitor module has completed charging, which can be specifically achieved through steps S321 - S327.

[0092] In step S321, the charging control device controls the DC side voltage to rise to the preset charging voltage value at the third preset boosting speed to start the charging in the second ultra-capacitor charging stage.

[0093] In step S322, the charging control device controls the DC side voltage to remain unchanged at the preset charging voltage value.

[0094] In step S323, the charging control device detects the average voltage of the ultra-capacitor modules in the second ultra-capacitor charging stage.

[0095] In step S324, the charging control device determines whether the average voltage of the ultra-capacitor modules reaches the preset voltage.

[0096] In step S325, the charging control device determines whether the average voltage of the ultra-capacitor modules reaches the preset ultra-capacitor rated charging voltage.

[0097] In step S326, when the average voltage of the ultra-capacitor modules reaches the preset voltage and does not reach the preset ultra-capacitor rated charging voltage, the charging control device controls the ultra-capacitor branch to cut off the preset number of ultra-capacitor modules in each ultra-capacitor cut-off cycle according to the average voltage of the ultra-capacitor modules and the ultra-capacitor voltage values of at least two ultra-capacitor modules.

[0098] In step S327, when the average voltage of the ultra-capacitor modules reaches the preset ultra-capacitor rated charging voltage, the charging of the ultra-capacitor modules is completed, and the charging in the second ultra-capacitor charging stage ends.

[0099] Exemplarily, after the charging control device raises the DC-side voltage of the MMC converter to the preset system startup voltage value and maintains it for a second preset duration, the first supercapacitor charging stage ends, and the second supercapacitor charging stage begins. That is, after the above step S315, steps S321 - S327 are started to be executed.

[0100] During the entire second supercapacitor charging stage from step S321 to step S327, the charging control device controls the DC-side voltage of the MMC converter to rise from the preset system startup voltage value to the preset charging voltage value at a third preset boosting speed, and after rising to the preset charging voltage value, controls the DC-side voltage of the MMC converter to remain unchanged at this preset charging voltage value.

[0101] The supercapacitor branch receives the DC-side voltage of the MMC converter and continuously charges, thereby causing the module voltage value of the supercapacitor module to continuously rise, and further causing the average voltage of the supercapacitor modules in the supercapacitor branch to continuously rise.

[0102] The module voltage value is the module voltage value of the supercapacitor module, and the average supercapacitor module voltage is the average value of the module voltage values of all the supercapacitor modules in this supercapacitor branch. For example, the supercapacitor branch includes two supercapacitor modules, the voltage of one supercapacitor module is 10V (module voltage value is 10V), and the voltage of the other supercapacitor module is 20V (module voltage value is 20V), and the average supercapacitor module voltage is 15V.

[0103] During the process of the charging control device controlling the output of the DC-side voltage of the MMC converter, the charging control device also continuously detects the average value of the voltages of all the supercapacitor modules in the supercapacitor branch to detect the average supercapacitor module voltage.

[0104] In steps S324 and S325, the charging control device determines whether the average supercapacitor module voltage reaches the preset voltage and whether it reaches the preset supercapacitor rated charging voltage.

[0105] The value of the preset voltage can be set by the user according to the preset charging voltage value, and can be specifically determined according to the number of supercapacitor modules before disconnection and the preset charging voltage value. For example, in a static synchronous compensator system, there are 40 supercapacitor modules, the preset charging voltage value is 20KV, and each supercapacitor module should be charged to at least 500V during the second supercapacitor charging stage, and the value of the preset voltage can be set to 475V, that is, the value of the preset voltage can be 0.95 * preset charging voltage value / number of supercapacitor modules before disconnection.

[0106] The preset supercapacitor rated charging voltage is the rated charging voltage of the supercapacitor module.

[0107] When the supercapacitor module is continuously charged, causing the average voltage of the supercapacitor module to rise to the preset voltage and not reaching the preset rated charging voltage of the supercapacitor, the supercapacitor module needs to continue charging. In this case, in step S326, the charging control device can control the supercapacitor branch to cut off a preset number of supercapacitor modules in each supercapacitor cut-off period according to the average voltage of the supercapacitor module and the supercapacitor module voltage value of each supercapacitor module.

[0108] Exemplarily, in step S326, when the average voltage of the supercapacitor module rises to the preset voltage, the charging control device starts to enter the first supercapacitor cut-off period, and at the initial moment of the supercapacitor cut-off period, a preset number of supercapacitor modules are cut off in the supercapacitor branch (for example, 1 supercapacitor module is cut off from 5 supercapacitor modules). The cut-off supercapacitor modules will not participate in charging in the current supercapacitor cut-off period, and the MMC converter will charge the remaining uncut supercapacitor modules.

[0109] After the preset supercapacitor cut-off period duration, the first supercapacitor cut-off period ends, and the second supercapacitor cut-off period is entered. At the initial moment of the second supercapacitor cut-off period, a preset number of supercapacitor modules are selected again from the supercapacitor modules in the supercapacitor branch for cutting off (for example, 1 supercapacitor module is cut off from 5 supercapacitor modules). The supercapacitor modules cut off in the second supercapacitor cut-off period and the first supercapacitor cut-off period can be the same or different, which is not limited here. The cut-off supercapacitor modules in the second supercapacitor cut-off period will not participate in charging in the second supercapacitor cut-off period, and the MMC converter will charge the uncut supercapacitor modules.

[0110] By analogy in the above manner, until it is detected that the average voltage of the supercapacitor module rises to the preset rated charging voltage of the supercapacitor, that is, it is detected that the charging of the supercapacitor module is completed.

[0111] When the average voltage of the supercapacitor module rises to the preset rated charging voltage of the supercapacitor, the charging control device also ends the charging of the second supercapacitor charging stage.

[0112] It should be noted that the order of the above step S324 and step S325 can be that step S324 is prior and step S325 is subsequent, or step S324 and step S325 are executed simultaneously, or step S325 is prior and step S324 is subsequent, which is not limited here.

[0113] According to some embodiments, referring to Figure 6 , in the above step S326, the charging control device controls the supercapacitor branch to cut off a preset number of supercapacitor modules in each supercapacitor cut-off period according to the average voltage of the supercapacitor module and the supercapacitor module voltage value of each supercapacitor module, which can be specifically implemented through steps S3261 - S3265.

[0114] In step S3261, the charging control device determines whether the average voltage of the over-capacitance module is within a preset over-capacitance charging voltage range in the current over-capacitance cut-off cycle.

[0115] In step S3262, when the average voltage of the over-capacitance module is lower than the lower limit value of the preset over-capacitance charging voltage range, the charging control device increases the first preset number based on the over-capacitance cut-off number in the previous over-capacitance cut-off cycle to determine the over-capacitance cut-off number in the current over-capacitance cut-off cycle.

[0116] In step S3263, when the average voltage of the over-capacitance module is within the preset over-capacitance charging voltage range, the charging control device determines the over-capacitance cut-off number in the previous over-capacitance cut-off cycle as the over-capacitance cut-off number in the current over-capacitance cut-off cycle.

[0117] In step S3264, the charging control device screens out the target cut-off over-capacitance modules in the current over-capacitance cut-off cycle from at least two over-capacitance modules according to the over-capacitance module voltage values of the at least two over-capacitance modules, and the number of the target cut-off over-capacitance modules is the over-capacitance cut-off number in the current over-capacitance cut-off cycle.

[0118] In step S3265, the charging control device cuts off the target cut-off over-capacitance modules from the over-capacitance branch to charge the remaining over-capacitance modules.

[0119] According to the exemplary embodiment, the upper limit value of the preset over-capacitance charging voltage range may specifically be the preset over-capacitance rated charging voltage. The lower limit value of the preset over-capacitance charging voltage range may specifically be 0.95 times the preset over-capacitance rated charging voltage.

[0120] Exemplarily, assume that the static synchronous compensator system has an over-capacitance branch, and the over-capacitance branch includes 4 over-capacitance modules. When the charging control device detects that the average voltage of the over-capacitance modules rises to the preset voltage, it enters the first over-capacitance cut-off cycle and determines whether the average voltage of the over-capacitance modules is within the preset over-capacitance charging voltage range.

[0121] At this time, the average voltage of the over-capacitance modules is lower than the lower limit value of the preset over-capacitance charging voltage range. Since this is the first over-capacitance cut-off cycle, the over-capacitance cut-off number in the first over-capacitance cut-off cycle is the preset over-capacitance cut-off number, which can be 1 or 0 for example. Subsequently, an example with the over-capacitance cut-off number in the first over-capacitance cut-off cycle being 1 is given for illustration.

[0122] The charging control device selects one supercapacitor module with the highest supercapacitor module voltage value from 4 supercapacitor modules according to the respective supercapacitor module voltage values of each supercapacitor module as the target supercapacitor module to be removed, such as supercapacitor module a1. The charging control device removes the target supercapacitor module from the supercapacitor branch, and the remaining 3 supercapacitor modules are charged in the first supercapacitor removal cycle, and the target supercapacitor module to be removed does not charge.

[0123] When the first supercapacitor removal cycle ends, it enters the second supercapacitor removal cycle. The charging control device determines that the average voltage of the supercapacitor modules is lower than the lower limit value of the preset supercapacitor charging voltage range. Therefore, the number of supercapacitor modules to be removed in the second supercapacitor removal cycle determined by the charging control device is 2 (assuming the first preset number is 1). The charging control device re-screens 2 supercapacitor modules from 4 supercapacitor modules in descending order of the supercapacitor module voltage values of the 4 supercapacitor modules as the target supercapacitor modules to be removed in the second supercapacitor removal cycle, such as supercapacitor module a2 and supercapacitor module a3, that is, the supercapacitor module voltage values of the 2 selected target supercapacitor modules to be removed are not less than those of other supercapacitor modules.

[0124] When screening the target supercapacitor modules to be removed, the charging control device can select them in descending order of the supercapacitor module voltage values. That is, in the current supercapacitor removal cycle, the charging control device first removes the supercapacitor module with a larger supercapacitor module voltage value in the current state.

[0125] In the second supercapacitor removal cycle, the charging control device removes the target supercapacitor modules to be removed in the second supercapacitor removal cycle (for example, removes supercapacitor module a2 and supercapacitor module a3), and the remaining supercapacitor modules (supercapacitor module a1 and supercapacitor module a4) are charged in the second supercapacitor removal cycle.

[0126] It should be noted that the target supercapacitor modules to be removed in different supercapacitor removal cycles may be different.

[0127] After the second supercapacitor removal cycle, it enters the third supercapacitor removal cycle. Assume that in the third supercapacitor removal cycle, the charging control device determines that the average voltage of the supercapacitor modules is within the preset supercapacitor charging voltage range. In this case, the charging control device determines that the number of supercapacitor modules to be removed in the third supercapacitor removal cycle remains the same as that in the second supercapacitor removal cycle, which is 2.

[0128] The charging control device screens 2 supercapacitor modules from 4 supercapacitor modules as the target supercapacitor modules to be removed in the third supercapacitor removal cycle, such as supercapacitor module a2 and supercapacitor module a4. The charging control device removes the target supercapacitor modules to be removed from the supercapacitor branch, and the remaining supercapacitor modules participate in charging in the third supercapacitor removal cycle. And so on, continuously loop and execute the above steps S3261 - step S3265.

[0129] It should be noted that after the end of the third over-capacitance removal cycle, the fourth over-capacitance removal cycle is entered. At this time, the average voltage of the over-capacitance module has been within the preset over-capacitance charging voltage range. The number of over-capacitance modules removed in subsequent over-capacitance removal cycles remains 2, and 2 over-capacitance modules are removed in each over-capacitance removal cycle, but the removed over-capacitance modules are different. In this case, the average voltage of the over-capacitance module can finally stabilize at the preset rated over-capacitance charging voltage, so that the over-capacitance branch completes the charging process.

[0130] According to the exemplary embodiment, with reference to Figure 2 , the removal of the over-capacitance module 21 can be achieved by controlling the second switching device 2122 of the over-capacitance sub-module 212 to conduct.

[0131] According to some embodiments, with reference to Figure 7 , the charging control method further includes step S710-step S730.

[0132] In step S710, when the charging control device receives a fault instruction transmitted by the management system of the over-capacitance module, the faulty over-capacitance module is determined according to the fault instruction.

[0133] According to the exemplary embodiment, the fault disconnection instruction is an instruction generated by the management system when detecting that there is an abnormality in the over-capacitance module.

[0134] In step S720, the charging control device controls the bypass switch corresponding to the faulty over-capacitance module to close.

[0135] In step S730, the charging control device controls the maintenance switch of the faulty over-capacitance module to disconnect to trip the faulty over-capacitance module.

[0136] According to the exemplary embodiment, steps S710-step S730 are executed simultaneously with the above steps S3261-S3265.

[0137] After the end of the first over-capacitance charging stage, the management system of the over-capacitance module and the central control board can operate normally. During the second over-capacitance charging stage, when the management system detects a fault in the over-capacitance module, a fault instruction will be generated to indicate that there is a fault in the over-capacitance module in the charging control device, and the identifier or identity information of the faulty over-capacitance module will be carried in the fault instruction and sent to the charging control device together to indicate the faulty over-capacitance module to the charging control device.

[0138] In this case, it is not advisable to continue charging the fault over-capacity module. Therefore, when the charging control device receives a fault instruction, it executes steps S710 - S730 to determine the fault over-capacity module according to the fault instruction, controls the bypass switch of the fault over-capacity module to close, bypasses the fault over-capacity module, and disconnects the maintenance switch of the fault over-capacity module to trip the fault over-capacity module and stop charging it.

[0139] According to some embodiments, referring to Figure 1 , the static synchronous compensator system further includes a DC-side switch 3, an AC circuit breaker 4, and a starting circuit 5.

[0140] The DC-side switch 3 is connected in series between the super-capacitor branch 2 and the DC side of the MMC converter 1 to control the on-off of the super-capacitor branch 2 and the DC side of the MMC converter 1.

[0141] The AC side of the MMC converter 1 is connected to the external power grid through the AC circuit breaker 4 and the starting circuit 5. The starting circuit 5 includes a starting resistor and a starting switch connected in parallel.

[0142] The MMC converter 1 includes six bridge arms, and at least two converter sub-modules 11 are cascaded on each bridge arm. For example Figure 1 In the example shown, the MMC converter 1 includes six bridge arms, and three cascaded converter sub-modules 11 are provided on each bridge arm.

[0143] Figure 8 Shows a structural example of the converter sub-module 11. Referring to Figure 8 , the converter sub-module 11 can be a full-bridge sub-module. The full-bridge sub-module includes a first full-bridge switching device 81, a second full-bridge switching device 82, a third full-bridge switching device 83, a fourth full-bridge switching device 84, and a full-bridge capacitor 85.

[0144] Figure 9 Shows another structural example of the converter sub-module 11. Referring to Figure 9 , the converter sub-module 11 can also be a half-bridge sub-module. The half-bridge sub-module includes a first half-bridge switching device 91, a second half-bridge switching device 92, and a half-bridge capacitor 93.

[0145] In the charging control method of the embodiment of the present application, before charging the super-capacitor branch, the MMC converter can be charged by using the external power grid first. After the MMC converter is charged, the above step S310 is executed.

[0146] Figure 10 Shows the step flow of charging the MMC converter. That is, before the above step S310, the charging control method may further include steps S1010 - S1080.

[0147] In step S1010, the charging control device controls the DC side switch to open, so that the connection between the DC side of the MMC converter and the supercapacitor branch is disconnected, and the MMC converter is charged first.

[0148] In step S1020, the charging control device controls the starting switch to open.

[0149] In step S1030, the charging control device controls each commutation sub-module of the MMC converter to be in a locked state.

[0150] According to the exemplary embodiment, referring to Figure 8 and Figure 9 , when the commutation sub-module 11 is a full-bridge sub-module, the charging control device can control the first full-bridge switch device 81, the second full-bridge switch device 82, the third full-bridge switch device 83, and the fourth full-bridge switch device 84 to be in an off state, so that the full-bridge sub-module is in a locked state.

[0151] According to the exemplary embodiment, referring to Figure 8 and Figure 9 , when the commutation sub-module 11 is a half-bridge sub-module, the charging control device can control the first half-bridge switch device 91 and the second half-bridge switch device 92 to be in an off state, so that the half-bridge sub-module is in a locked state.

[0152] It should be noted that the execution order of step S1020 and step S1030 can be to execute step S1020 first and then step S1030, or to execute step S1030 first and then step S1020, or to execute step S1020 and step S1030 simultaneously, which is not limited herein.

[0153] In step S1040, the charging control device controls the AC circuit breaker to close, so that the external power grid starts to charge the MMC converter in the first commutation charging stage.

[0154] In steps S1010 - S1040, the charging control device disconnects the starting switch, disconnects the DC side switch, controls each commutation sub-module to be in a locked state, and closes the AC circuit breaker, and then the external power grid can start to charge the MMC converter through the starting resistor.

[0155] In step S1050, when the charging control device detects that the charging current of the MMC converter is less than the preset current limit value and the total average voltage of the bridge arm of the MMC converter reaches the preset module energy-taking voltage value, the first commutation charging stage ends.

[0156] According to the exemplary embodiment, the preset module obtains the enabling voltage value as the voltage value required for the commutation sub-module to have communication and identification capabilities. The enabling voltage value obtained by the preset module can specifically be 0.95*U lmax / (2*N). U lmax is the peak value of the line voltage on the power frequency side, and N is the number of commutation sub-modules in each arm. The preset current limit value can specifically be 0.1 pu.

[0157] The total average voltage of the arm is the average value of the voltages of all arms. For example, if the MMC converter has 6 arms and each arm consists of 3 commutation sub-modules, the total average voltage of the arm is the average voltage of 18 commutation sub-modules. The total average voltage of the arm can specifically be obtained by measuring the total voltage of each arm and finding its average value.

[0158] When the charging current is less than the preset current limit value and the total average voltage of the arm reaches the enabling voltage value of the preset module, it indicates that all commutation sub-modules have successfully obtained energy, and the first commutation charging stage ends.

[0159] In step S1060, the charging control device controls the closing of the starting switch to start charging the MMC converter for the second commutation charging stage.

[0160] When the first commutation charging stage ends, the MMC converter starts charging for the second commutation charging stage. In step S1060, when the first commutation charging stage ends, the charging control device controls the closing of the starting switch, short-circuits the starting resistor, increases the charging current, speeds up the charging speed, and the MMC converter starts charging for the second commutation stage until it is detected that each commutation sub-module has completed charging, and the second commutation charging stage ends.

[0161] In step S1070, when the total average voltage of the arm does not reach the preset commutation rated charging voltage, the charging control device controls each arm of the MMC converter to cut off a preset number of commutation sub-modules respectively according to the total average voltage of the arm and the commutation module voltage values of each commutation sub-module in each commutation cut-off period.

[0162] In step S1080, when the total average voltage of the arm reaches the preset commutation rated charging voltage, each commutation sub-module of the MMC converter has completed charging, and the charging for the second commutation charging stage ends.

[0163] According to the exemplary embodiment, in the second commutation charging stage, the charging control device detects whether the total average voltage of the arm reaches the preset commutation rated charging voltage.

[0164] In step S1080, when the total average voltage of the bridge arm reaches the preset commutation rated charging voltage, it indicates that the charging of the MMC converter is completed, and the charging control device can end the charging of the second commutation charging stage.

[0165] And in step S1070, when the total average voltage of the bridge arm does not reach the preset commutation rated charging voltage, the MMC converter still needs to continue charging, and the charging control device can continue to control the external power grid to continue charging the MMC converter. Moreover, during the charging process, the charging control device can also, according to the total average voltage of the bridge arm and the commutation module voltage values of each commutation sub-module, in each commutation cut-off period, cut off the commutation sub-modules of the MMC converter in the way of cutting off the preset commutation cut-off number of commutation sub-modules for each bridge arm, so as to accelerate the charging process of the MMC converter.

[0166] Exemplarily, when the charging control device enters the second commutation charging stage of the MMC converter, it enters the first commutation cut-off period, and at the initial moment of the commutation cut-off period, respectively cut off the preset commutation cut-off number of commutation sub-modules in each bridge arm of the MMC converter.

[0167] For example, if the MMC converter has six bridge arms and the preset cut-off number is 1, then one commutation sub-module is cut off for each bridge arm, and a total of six commutation sub-modules are cut off from the MMC converter.

[0168] The cut-off commutation sub-modules will not participate in charging during the current commutation cut-off period, and the external power grid will only charge the remaining uncut commutation sub-modules.

[0169] After the preset commutation cut-off period duration, the first commutation cut-off period ends and the second commutation cut-off period begins. At the initial moment of the second commutation cut-off period, the charging control module respectively cuts off the preset commutation cut-off number of commutation sub-modules in each bridge arm again.

[0170] Among them, the commutation sub-modules cut off in the second commutation cut-off period and the first commutation cut-off period can be the same or different, which is not limited here.

[0171] And so on in the above manner. In each commutation cut-off period, the preset commutation cut-off number of commutation sub-modules is re-selected from all the commutation sub-modules of all the bridge arms for cutting off. In this way, the uncut commutation sub-modules can be charged during the commutation cut-off period, and the commutation sub-modules are replaced for charging in the next commutation cut-off period. Compared with directly charging all the commutation sub-modules simultaneously, this way of charging in batches has a faster charging speed.

[0172] According to some embodiments, Figure 11 shows the step flow of cutting off the commutation sub-modules in the above step S1070. Refer toFigure 11 , step S1070 described above may include steps S1071 - S1075.

[0173] In step S1071, the charging control device determines whether the total average voltage of the bridge arm is within a preset commutation charging voltage range.

[0174] In step S1072, when the total average voltage of the bridge arm is lower than the lower limit value of the preset commutation charging voltage range, the charging control device increases the second preset number based on the commutation cut-off number in the previous commutation cut-off period to determine the commutation cut-off number in the current commutation cut-off period.

[0175] In step S1073, when the total average voltage of the bridge arm is within the preset commutation charging voltage range, the charging control device determines the commutation cut-off number in the previous commutation cut-off period as the commutation cut-off number in the current commutation cut-off period.

[0176] In step S1074, based on the commutation module voltage values of each commutation sub-module, the charging control device respectively screens out the target cut-off commutation sub-modules corresponding to each bridge arm in the current commutation cut-off period from each bridge arm. The number of target cut-off commutation sub-modules corresponding to each bridge arm is the commutation cut-off number in the current commutation cut-off period.

[0177] In step S1075, the charging control device cuts off the target cut-off commutation sub-modules.

[0178] Exemplarily, taking the MMC converter having six bridge arms with three commutation sub-modules provided in each bridge arm as an example for illustration. When the charging control device enters the second commutation charging stage, it enters the first commutation cut-off period.

[0179] At the beginning of the first commutation cut-off period, the charging control device executes step S1071 to determine whether the current total average voltage of the bridge arm is within the preset commutation charging voltage range. Since the current commutation period is the first commutation cut-off period, in this first commutation cut-off period, regardless of whether the current total average voltage of the bridge arm is lower than the preset commutation charging voltage range, the commutation cut-off number in this first commutation cut-off period is the preset cut-off number. The preset cut-off number can be 1 or 0, which is not limited here. Subsequently, an example is given with the commutation cut-off number in the first commutation cut-off period being 0.

[0180] In the first commutation cut-off period, no commutation sub-module is cut off from each bridge arm. After the preset commutation cut-off period duration, it enters the second commutation cut-off period, and the charging control device executes step S1071.

[0181] At the start of the second commutation cut-off period, the charging control device determines that the current total average voltage of the bridge arm is lower than the lower limit value of the preset commutation charging voltage range, and executes step S1072. And the number of commutation cut-offs determined by the charging control device for the second commutation cut-off period is 1 (assuming the second preset number is 1).

[0182] Subsequently, step S1074 is executed. The charging control device selects 1 commutation sub-module from the first bridge arm, 1 commutation sub-module from the second bridge arm... 1 commutation sub-module from the sixth bridge arm according to the commutation module voltage values of the respective commutation sub-modules, so as to determine six target cut-off commutation sub-modules. Then, in step S1075, the charging control device cuts off the six target cut-off commutation sub-modules.

[0183] After the preset commutation cut-off period duration, the third commutation cut-off period is entered, and the charging control device repeatedly executes steps S1071 - S1075. For example, if the total average voltage of the bridge arm at the start of the third commutation cut-off period is within the preset commutation charging voltage range, the number of commutation cut-offs for the third commutation cut-off period is also 1. The charging control device re-selects 1 commutation sub-module from the 3 commutation sub-modules in the first bridge arm, 1 commutation sub-module from the 3 commutation sub-modules in the second bridge arm... 1 commutation sub-module from the 3 commutation sub-modules in the sixth bridge arm for cutting off.

[0184] And so on, until the total average voltage of the bridge arm reaches the preset commutation rated charging voltage, and each commutation sub-module completes charging, ending the second commutation charging stage.

[0185] According to the exemplary embodiment, in the above step S1074, when the charging control device selects the target cut-off commutation sub-modules corresponding to each bridge arm in each bridge arm according to the commutation module voltage values of the respective commutation sub-modules, it can be selected in the order from the largest to the smallest commutation module voltage value. That is, in the current commutation cut-off period, the charging control device preferentially cuts off the commutation sub-modules with larger current commutation module voltage values.

[0186] It should be noted that the target cut-off commutation modules in different commutation cut-off periods may be different.

[0187] According to the exemplary embodiment, referring to Figure 9 , the specific manner for the charging control device to cut off the commutation sub-module 11 can be to control the second half-bridge switching device 92 of the half-bridge sub-module when the commutation sub-module 11 is a half-bridge sub-module.

[0188] Referring to Figure 8When the commutation sub-module 11 is a full-bridge sub-module, the charging control device can cut off the commutation sub-module by controlling the second full-bridge switching device 82 and the fourth full-bridge switching device 84 to conduct, or by controlling the first full-bridge switching device 81 and the third full-bridge switching device 83 to conduct.

[0189] Refer to Figure 8 That is, two switching devices directly connected to the negative electrode of the capacitor in the full-bridge sub-module are simultaneously conducted, and the other two switching devices remain blocked, or two switching devices directly connected to the positive electrode of the capacitor are simultaneously conducted, and the other two switching devices remain blocked. One switching device directly connected to the negative electrode of the capacitor in the half-bridge sub-module is conducted, and the other switching device remains blocked. In this way, the commutation sub-module 11 can be cut off.

[0190] It should be clearly understood that this application describes how to form and use specific examples, but this application is not limited to any details of these examples. On the contrary, based on the teachings of the content disclosed in this application, these principles can be applied to many other embodiments.

[0191] Those skilled in the art can understand that all or part of the steps for implementing the above embodiments are implemented as a computer program executed by a CPU. When this computer program is executed by the CPU, the above functions defined by the above method provided in this application are executed.

[0192] According to another aspect of this application, an embodiment of this application provides a charging control device applied to a static synchronous compensator system. The device embodiments of this application described below can be used to execute the method embodiments of this application. For details not disclosed in the device embodiments of this application, reference can be made to the method embodiments of this application.

[0193] As Figure 12 shown, the charging control device may include: the charging control device includes a first supercapacitor charging stage control module 1201, a first supercapacitor charging stage detection module 1202, and a second supercapacitor charging stage control module 1203.

[0194] The first supercapacitor charging stage control module 1201 is used to control the DC side voltage of the MMC converter to increase to a preset system startup voltage value in a first preset manner, so as to charge at least two supercapacitor modules in the first supercapacitor charging stage. The first supercapacitor charging stage detection module 1202 is used to detect whether the supercapacitor module voltage values of at least two supercapacitor modules are higher than a preset detection value during the first supercapacitor charging stage; and in the case where there is a supercapacitor module with a supercapacitor module voltage value higher than a preset voltage limit, control the bypass switch of the supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit to close, so as to bypass the supercapacitor module with a supercapacitor module voltage value higher than the preset voltage limit. The second supercapacitor charging stage control module 1203 is used to control the DC side voltage of the MMC converter to increase to a preset charging voltage value in a second preset manner after the first supercapacitor charging stage ends, so as to charge at least two supercapacitor modules in the second supercapacitor charging stage until it is detected that each supercapacitor module is fully charged.

[0195] The device performs functions similar to the method provided above. For other functions, refer to the previous description and will not be elaborated here.

[0196] According to another aspect of the present application, an embodiment of the present application provides a static synchronous compensator system. Refer to Figure 1 With Figure 2 , the static synchronous compensator system includes an MMC converter 1, a supercapacitor branch 2, and a charging control device. The supercapacitor branch 2 is connected to the DC side of the MMC converter 1; the supercapacitor branch 2 includes at least two supercapacitor modules 21 and a bypass switch 22 corresponding to each supercapacitor module 21. The at least two supercapacitor modules 21 are connected in series, and both ends of the bypass switch 22 are connected to both ends of the supercapacitor module 21, that is, the bypass switch 22 is connected in parallel with the supercapacitor module. When the bypass switch 22 is closed, the supercapacitor module will be short-circuited. The supercapacitor module 21 includes a supercapacitor 211, a supercapacitor sub-module 212, and a maintenance switch 213. The charging control device is used to execute the above charging control method.

[0197] According to another aspect of the present application, an embodiment of the present application also introduces a charging control device from the perspective of an entity device. Refer to Figure 13 , Figure 13 The charging control device shown in

[0198] The processor 1301 may be a CPU (Central Processing Unit), a general-purpose processor, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute various exemplary logical blocks, modules, and circuits described in connection with the disclosure of this application. The processor 1301 may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc.

[0199] The bus 1302 may include a path for transmitting information between the above components. The bus 1302 may be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. The bus 1302 may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 13 only a thick line is used to represent it in the figure, but it does not mean that there is only one bus or one type of bus.

[0200] The memory 1303 may be a ROM (Read Only Memory) or other type of static storage device that can store static information and instructions, a RAM (Random Access Memory) or other type of dynamic storage device that can store information and instructions, or it may also be an EEPROM (Electrically Erasable Programmable Read Only Memory), a CD-ROM (Compact Disc Read Only Memory), or other optical disc storage, optical disc storage (including compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), magnetic storage media, or other magnetic storage devices, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto.

[0201] The memory 1303 is used to store the application program code for executing the solution of this application, and is controlled by the processor 1301 for execution. The processor 1301 is used to execute the application program code stored in the memory 1303 to implement the content shown in the foregoing method embodiments.

[0202] According to another aspect of this application, embodiments of this application provide a non-volatile computer-readable medium, on which a computer program is stored. When the computer program runs on a computer, it enables the computer to execute the corresponding content in the foregoing method embodiments. The storage medium may be a read-only memory, a magnetic disk, an optical disc, or the like.

[0203] According to another aspect of this application, embodiments of this application provide a computer program product. The computer program product includes a computer program stored on a computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, it enables the computer to execute the corresponding content in the foregoing method embodiments.

[0204] Finally, it should be noted that the above are only the preferred embodiments of this application and are not used to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions of the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A charging control method for a static synchronous condenser system, characterized in that: The static synchronous condenser system comprises an MMC converter and an overcapacity branch, wherein the DC side of the MMC converter is connected to the overcapacity branch; The super-capacity branch includes at least two super-capacity modules and a bypass switch corresponding to each super-capacity module; The at least two super-capacitor modules are connected in series, and the two ends of the bypass switch are respectively connected to the two ends of the super-capacitor modules; each super-capacitor module includes a supercapacitor, a super-capacitor sub-module and a maintenance switch; The charging control method comprises: Controlling the DC side voltage of the MMC converter to increase to a preset system startup voltage value in a first preset manner, so as to charge the at least two super-capacity modules in a first super-capacity charging stage; In the first super-capacity charging stage, detecting whether the super-capacity module voltage value of each of the at least two super-capacity modules is higher than a preset voltage limit; In the case where there is an over-capacity module whose voltage value of the over-capacity module is higher than the preset voltage limit, controlling the bypass switch of the over-capacity module whose voltage value of the over-capacity module is higher than the preset voltage limit to be closed, so as to bypass the over-capacity module whose voltage value of the over-capacity module is higher than the preset voltage limit; When the first super-capacity charging stage is completed, the DC side voltage of the MMC converter is controlled to increase to a preset charging voltage value in a second preset manner, so as to charge the at least two super-capacity modules in the second super-capacity charging stage until it is detected that the at least two super-capacity modules are fully charged.

2. The charging control method according to claim 1, characterized in that: The controlling the DC side voltage of the MMC converter to increase to a preset system startup voltage value in a first preset manner so as to charge the at least two super-capacity modules in the first super-capacity charging stage comprises: Controlling the DC side voltage of the MMC converter to increase to a preset module starting voltage value according to a first preset boosting speed, so as to start charging in the first super-capacity charging stage; Start timing a first duration, where the first duration is the duration during which the DC side voltage remains at the preset module starting voltage value; When it is detected that the first duration reaches a first preset duration, controlling the DC side voltage of the MMC converter to increase to the preset system startup voltage value at a second preset boost speed; Start timing a second duration, where the second duration is the duration during which the DC side voltage remains at the preset system starting voltage value; When it is detected that the second duration reaches a second preset duration, ending the charging in the first super-capacity charging stage; Wherein, the preset system startup voltage value is determined according to the first startup voltage value of the central control board of the super-capacity module, the second startup voltage value of the management system of the super-capacity module, and the third startup voltage value of the management system; The first starting voltage value is the voltage value required for powering on the central control board; The second starting voltage value is a voltage value required for the management system to be powered on and started; The third starting voltage value is a voltage value that the management system needs to access to realize the function of accurately identifying faults.

3. The charging control method according to claim 1, characterized in that: The step of controlling the DC side voltage of the MMC converter to increase to a preset charging voltage value in a second preset manner so as to charge the at least two super-capacity modules in a second super-capacity charging stage until it is detected that all super-capacity modules have been fully charged includes: Controlling the DC side voltage to increase to the preset charging voltage value at a third preset boosting speed to start charging in the second super-capacity charging stage; Controlling the DC side voltage to keep the preset charging voltage value unchanged; In the second super-capacity charging stage, detecting the average voltage of the super-capacity module, wherein the average voltage of the super-capacity module is the average of the voltages of the at least two super-capacity modules; Determining whether the average voltage of the super-capacity module reaches a preset voltage; Determining whether the average voltage of the super-capacity module reaches a preset super-capacity rated charging voltage; When the average voltage of the super-capacity module reaches the preset voltage and does not reach the preset super-capacity rated charging voltage, according to the average voltage of the super-capacity module and the super-capacity module voltage values ​​of the at least two super-capacity modules, the super-capacity branch is controlled to remove a preset number of super-capacity removal super-capacity modules in each super-capacity removal period; When the average voltage of the super-capacity module reaches the preset super-capacity rated charging voltage, the charging of the super-capacity module is completed, and the charging of the second super-capacity charging stage ends.

4. The charging control method according to claim 3, characterized in that: The controlling the super-capacity branch to remove a preset number of super-capacity removal modules in each super-capacity removal period according to the super-capacity module average voltage and the super-capacity module voltage values ​​of each super-capacity module comprises: In the current over-capacity removal cycle, determining whether the average voltage of the over-capacity module is within a preset over-capacity charging voltage range; When the average voltage of the over-capacity module is lower than the lower limit of the preset over-capacity charging voltage range, a first preset number is added to the over-capacity removal number of the previous over-capacity removal cycle to determine the over-capacity removal number of the current over-capacity removal cycle; When the average voltage of the super-capacity module is within the preset super-capacity charging voltage range, the super-capacity removal quantity of the previous super-capacity removal cycle is determined as the super-capacity removal quantity of the current super-capacity removal cycle; According to the respective super-capacity module voltage values ​​of the at least two super-capacity modules, a target super-capacity module to be removed in the current super-capacity removal cycle is selected from the at least two super-capacity modules, wherein the number of the target super-capacity modules to be removed is the number of super-capacity removals in the current super-capacity removal cycle; The target over-capacity module is removed from the over-capacity branch to charge the remaining over-capacity modules.

5. The charging control method according to claim 3, characterized in that: The charging control method further includes: In the case of receiving a fault instruction transmitted by the management system of the super-capacity module, determining the faulty super-capacity module according to the fault instruction, wherein the fault instruction is an instruction generated when the management system detects that there is an abnormality in the super-capacity module; Controlling the bypass switch corresponding to the fault over-capacity module to close; The maintenance switch of the fault-exceeding-tolerance module is controlled to be disconnected to trip the fault-exceeding-tolerance module.

6. The charging control method according to claim 1, characterized in that: The static synchronous condenser system further includes a DC side switch, an AC circuit breaker and a starting circuit, wherein the DC side switch is connected in series between the super-capacity branch and the DC side of the MMC converter to control the on-off of the super-capacity branch and the DC side of the MMC converter; The AC side of the MMC converter is connected to the external power grid through an AC circuit breaker and a starting circuit, wherein the starting circuit includes a starting resistor and a starting switch connected in parallel; The MMC converter comprises six bridge arms, each of which is provided with at least two cascaded converter submodules; Before the DC side voltage of the MMC converter is controlled to increase to a preset system startup voltage value in a first preset manner, the method further includes: Controlling the DC side switch to be disconnected so as to disconnect the DC side of the MMC converter from the over-capacity branch; Controlling the start switch to be disconnected; Controlling each commutation submodule of the MMC converter to be in a locked state; Controlling the AC circuit breaker to close so that the external power grid starts charging the MMC converter in the first commutation charging stage; When it is detected that the charging current of the MMC converter is less than the preset current limit and the total average voltage of the bridge arm of the MMC converter reaches the preset module energy extraction voltage value, the first commutation charging stage ends; Controlling the start switch to close, so as to start charging the MMC converter in the second commutation charging stage; When the total average voltage of the bridge arm does not reach the preset commutation rated charging voltage, according to the total average voltage of the bridge arm and the commutation module voltage value of each commutation sub-module, each bridge arm of the MMC converter is controlled to remove a preset commutation removal number of commutation sub-modules in each commutation removal period; When the total average voltage of the bridge arm reaches the preset commutation rated charging voltage, the charging of each commutation submodule of the MMC converter is completed, so as to end the charging of the second commutation charging stage; Among them, the preset module energy-taking voltage value is the voltage value required for the commutation submodule to have communication and identification capabilities; the total average voltage of the bridge arm is the average value of all bridge arm voltages.

7. The charging control method according to claim 6, characterized in that: The method of controlling each bridge arm of the MMC converter to respectively cut off a preset number of commutation removal submodules in each commutation removal period according to the total average voltage of the bridge arm and the commutation module voltage value of each commutation submodule comprises: Determining whether the total average voltage of the bridge arm is within a preset commutation charging voltage range; When the total average voltage of the bridge arm is lower than the lower limit of the preset commutation charging voltage range, a second preset number is added to the commutation removal number of the previous commutation removal cycle to determine the commutation removal number of the current commutation removal cycle; When the total average voltage of the bridge arm is within the preset commutation charging voltage interval, the commutation removal quantity of the previous commutation removal cycle is determined as the commutation removal quantity of the current commutation removal cycle; According to the commutation module voltage values ​​of the respective commutation sub-modules, the target removal commutation sub-modules of the current commutation removal period corresponding to the respective bridge arms are screened out from the respective bridge arms, and the number of the target removal commutation sub-modules corresponding to each bridge arm is the commutation removal number of the current commutation removal period; The target cut-off commutation submodule is cut off.

8. A charging control device for a static synchronous condenser system, characterized in that: The static synchronous condenser system comprises an MMC converter and an overcapacity branch, wherein the DC side of the MMC converter is connected to the overcapacity branch; The super-capacity branch includes at least two super-capacity modules and a bypass switch corresponding to each super-capacity module; The at least two super-capacity modules are connected in series, and the two ends of the bypass switch are respectively connected to the two ends of the super-capacity modules; Each supercapacitor module includes a supercapacitor, a supercapacitor submodule and a maintenance switch; wherein the charging control device includes: A first super-capacity charging stage control module, used for controlling the DC side voltage of the MMC converter to increase to a preset system starting voltage value according to a first preset method, so as to charge the at least two super-capacity modules in the first super-capacity charging stage; a first super-capacity charging stage detection module, configured to detect, in the first super-capacity charging stage, whether the super-capacity module voltage value of each of the at least two super-capacity modules is higher than a preset detection value; and, in the case where there is a super-capacity module whose super-capacity module voltage value is higher than a preset voltage limit value, control the bypass switch of the super-capacity module whose super-capacity module voltage value is higher than the preset voltage limit value to close, so as to bypass the super-capacity module whose super-capacity module voltage value is higher than the preset voltage limit value; The second super-capacity charging stage control module is used to control the DC side voltage of the MMC converter to increase to a preset charging voltage value in a second preset manner when the first super-capacity charging stage is completed, so as to charge the at least two super-capacity modules in the second super-capacity charging stage until it is detected that all super-capacity modules are fully charged.

9. A static synchronous condenser system, characterized in that: The static synchronous condenser system comprises: MMC inverter; An overcapacity branch connected to the DC side of the MMC converter; The super-capacity branch includes at least two super-capacity modules and a bypass switch corresponding to each super-capacity module; The at least two super-capacity modules are connected in series, and the two ends of the bypass switch are respectively connected to the two ends of the super-capacity modules; Each supercapacitor module includes a supercapacitor, a supercapacitor submodule, and a maintenance switch; A charging control device, wherein the charging control device is used to execute the charging control method described in any one of claims 1 to 7.

10. A charging control device, characterized in that: The charging control device comprises: one or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the charging control method as described in any one of claims 1 to 7.

11. A non-volatile computer readable medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the charging control method according to any one of claims 1 to 7 is implemented.

12. A computer program product, characterized in that The invention comprises a computer program stored on a computer-readable storage medium, wherein the computer program comprises program instructions, and when the program instructions are executed by a computer, the computer is caused to execute the charging control method according to any one of claims 1 to 7.

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