Charging control method and system applied to static synchronous phase modifier system

Abstract

The invention relates to a charging control method applied to a static synchronous phase modifier system. The charging control method comprises the following steps: controlling the direct current side voltage of the MMC converter to rise to a preset system starting voltage value according to a first preset mode so as to charge at least two super-capacitance modules in a first super-capacitance charging stage. In the first super-capacitance charging stage, detecting whether the voltage values of the at least two super-capacitance modules are higher than a preset voltage limit value or not; and under the condition that the voltage value of the super-capacitance module is higher than the preset voltage limit value, a bypass switch of the super-capacitance module of which the voltage value is higher than the preset voltage limit value is controlled to be closed, so that bypass processing is performed on the super-capacitance module of which the voltage value is higher than the preset voltage limit value. And under the condition that the first super-capacitance charging stage is finished, controlling the direct-current side voltage of the MMC converter to rise to a preset charging voltage value according to a second preset mode so as to charge the at least two super-capacitance modules in a second super-capacitance charging stage until it is detected that charging of the at least two super-capacitance modules is completed.

Description

Technical Field

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

[0002] The static synchronous condenser is a dynamic reactive power compensation device based on grid-type control technology, which is widely used in new power systems with renewable energy as the main body. The static synchronous condenser has the characteristics of a self-synchronous voltage source, which can provide inertia and voltage support to the system, thus solving problems such as transient low voltage and overvoltage, broadband oscillation, etc. in new power systems with renewable energy as the main body.

[0003] The static synchronous condenser is composed of a MMC (Modular Multilevel Converter Q, referred to as MMC converter for short) and a supercapacitor branch (referred to as supercapacitor branch for short).

[0004] The MMC converter can convert AC power into DC power, including a DC side and an AC side. The DC side of the MMC converter is connected to the super-capacity branch.

[0005] An MMC converter usually includes multiple bridge arms, each of which is provided with a bridge arm reactor and multiple commutation sub-modules (SMs). For example, a typical three-phase MMC converter consists of six bridge arms, each of which is provided with multiple sub-modules and a bridge arm inductor.

[0006] The supercapacitor branch usually includes multiple supercapacitor submodules and multiple supercapacitors. The supercapacitor submodule is a half-bridge submodule. A small capacitor is included in the half-bridge submodule. The supercapacitor is connected in parallel with the small capacitor through a maintenance switch.

[0007] Before the static synchronous condenser is operated, the MMC converter and the supercapacitor branch need to be charged, and the voltage of the converter module of the MMC converter and the voltage of the supercapacitor module and supercapacitor of the supercapacitor branch are charged to the corresponding rated voltage respectively, so that the static synchronous condenser can operate normally.

[0008] However, the inventors have discovered that when charging the supercapacitor branch using the prior art, if the maintenance switch between the supercapacitor and the supercapacitor submodule is disconnected due to improper manual operation or other reasons, then during the charging process of the supercapacitor branch, only the small capacitor of the supercapacitor submodule will be charged, causing the voltage value of the supercapacitor submodule to be much higher than the normal voltage value, thereby damaging the supercapacitor submodule. Summary of the invention

[0009] The present application aims to provide a charging control method and system for a static synchronous condenser system.

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

[0011] The charging control method includes: 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 at least two super-capacity modules in the 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 the preset voltage limit. In the case of a super-capacity module whose super-capacity module voltage value is higher than the preset voltage limit, controlling the bypass switch of the super-capacity module whose super-capacity module voltage value is higher than the preset voltage limit to close, so as to bypass the super-capacity module whose super-capacity module voltage value is higher than the preset voltage limit. When the first super-capacity charging stage ends, controlling the DC side voltage of the MMC converter to increase to a preset charging voltage value according to a second preset method, so as to charge at least two super-capacity modules in the second super-capacity charging stage, until it is detected that at least two super-capacity modules are fully charged.

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

[0013] According to another aspect of the present application, a charging control device for a static synchronous condenser system is proposed. The charging control device includes a first super-capacity charging stage control module, a first super-capacity charging stage detection module, and a second super-capacity charging stage control module. The first super-capacity charging stage control module is used to control 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 at least two super-capacity modules in the first super-capacity charging stage; the first super-capacity charging stage detection module is used to detect whether the super-capacity module voltage value of each of at least two super-capacity modules is higher than a preset detection value in the first super-capacity charging stage; and in the case of 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 according to a second preset method when the first super-capacity charging stage ends, so as to charge at least two super-capacity modules in the second super-capacity charging stage, until it is detected that each super-capacity module has been fully charged.

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

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

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

[0017] Beneficial Effects

[0018] The MMC converter is used to charge the supercapacity branch in the first supercapacity charging stage and the second supercapacity charging stage, and during the first supercapacity charging stage, the supercapacity module voltage value of each supercapacity module is continuously detected to see whether it reaches the preset voltage limit, so as to detect whether the maintenance switch of each supercapacity module is closed. And in the case of detecting that there is a supercapacity module with an unclosed maintenance switch, the bypass switch of the supercapacity module is closed for bypass processing. This is equivalent to short-circuiting the supercapacity module so that the supercapacity module no longer participates in charging, thereby reducing the probability of the supercapacity module with an unclosed maintenance switch being damaged due to excessive voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 This is a schematic diagram of the system structure of a static synchronous condenser system according to an embodiment of the present application;

[0021] Figure 2 Schematic diagram of the circuit structure of the super-capacitance branch of the embodiment of the present application;

[0022] Figure 3 This is a flowchart of the charging control method according to an embodiment of the present application;

[0023] Figure 4 This is a flow chart of step S310 of the embodiment of the present application;

[0024] Figure 5 This is a schematic diagram of the process of the second super-capacity charging stage of the embodiment of the present application;

[0025] Figure 6 This is a flow chart of step S326 of the embodiment of the present application;

[0026] Figure 7 A schematic diagram of a process of removing a faulty super-capacity module in the second super-capacity charging stage according to an embodiment of the present application;

[0027] Figure 8 This is a schematic diagram of the circuit structure of the full-bridge commutation submodule of the embodiment of the present application;

[0028] Fig. 9 This is a schematic diagram of the circuit structure of the half-bridge commutation submodule of the embodiment of the present application;

[0029] Fig.10 A schematic diagram of a process for charging an MMC converter according to an embodiment of the present application;

[0030] Fig.11 This is a flow chart of step S1070 of the embodiment of the present application;

[0031] Fig.12 This is a block diagram of a charging control device according to an embodiment of the present application;

[0032] Fig.13 A schematic diagram of an electronic device according to an embodiment of the present application.

[0033] Description of reference numerals:

[0034] 1. MMC converter; 11. converter module; 81. first full-bridge switch device; 82. second full-bridge switch device; 83. third full-bridge switch device; 84. fourth full-bridge switch device; 85. full-bridge capacitor; 91. first half-bridge switch device; 92. second half-bridge switch device; 93. half-bridge capacitor; 2. supercapacitor branch; 21. supercapacitor module; 211. supercapacitor; 212. supercapacitor module; 2121. first switch device; 2122. second half-bridge switch device; 93. second half-bridge capacitor; 2. supercapacitor branch; 21. supercapacitor module; 2122. supercapacitor module; 2121. first switch device; 2122. second half-bridge switch device; 94. second half-bridge capacitor; 95. first half-bridge capacitor; 96. first half-bridge capacitor; 97. first half-bridge capacitor; 98. first half-bridge capacitor; 99. first half-bridge capacitor; 100. first half-bridge capacitor; 111. first half-bridge capacitor; 112. first half-bridge capacitor; 113. first half-bridge capacitor; 114. first half-bridge capacitor; 115. first half-bridge capacitor; 116. first half-bridge capacitor; 117. first half-bridge capacitor; 118. first half-bridge capacitor; 119. first half-bridge capacitor; 120. first half-bridge capacitor; 121. first half-bridge capacitor; 122. first half-bridge capacitor; 123. first half-bridge capacitor; 124. first half-bridge capacitor; 125. first half-bridge capacitor; 126. first half-bridge capacitor; 127. first half-bridge capacitor; 128. first half-bridge capacitor; 129. first half-bridge capacitor; 130. first Two switching devices; 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 super-capacity charging stage control module; 1202, first super-capacity charging stage detection module; 1203, second super-capacity charging stage control module; 1301, processor; 1302, bus; 1303, memory; 1304, transceiver. DETAILED DESCRIPTION

[0035] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many 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 comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0036] The described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of these specific details, or other modes, components, materials, devices, etc. may be adopted. In these cases, known structures, methods, devices, implementations, materials or operations will not be shown or described in detail.

[0037] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. 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 may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

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

[0039] The following is a clear and complete description of the technical solution of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection 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 condenser system.

[0041] Figure 1 FIG. 1 shows a structural example of a static synchronous condenser system. Figure 1 The static synchronous phase condenser system includes at least one MMC converter 1 and at least one super-capacity branch 2. The DC side of each MMC converter 1 is connected to at least one super-capacity branch 2.

[0042] It is worth noting that, when the MMC converter 1 is connected to at least two overcapacity branches 2, the at least two overcapacity branches 2 are connected in parallel to the DC side of the MMC converter 1. For example, Figure 1 FIG. 4 shows a situation where an MMC converter 1 is connected to two over-capacity branches 2 .

[0043] Figure 2 FIG. 2 shows a circuit structure of an ultra-capacitor module 21 and a bypass switch 22. According to an exemplary embodiment, Figure 1 and Figure 2 As shown, each super-capacity branch 2 includes at least two super-capacity modules 21 and a bypass switch 22 corresponding to each super-capacity module 21. The at least two super-capacity modules 21 are cascaded, and the bypass switch 22 is connected in parallel with the super-capacity module 21, that is, the two ends of the bypass switch 22 are respectively connected to the two ends of the super-capacity module 21, and when the bypass switch 22 is closed, the super-capacity module 21 will be short-circuited.

[0044] Reference Figure 2 Each supercapacitor module 21 includes a supercapacitor 211, a supercapacitor submodule 212, and a maintenance switch 213. The supercapacitor submodule 212 is a half-bridge structure, specifically including a first switch device 2121, a second switch device 2122, and a parallel small capacitor 2123. The supercapacitor 211 is connected in parallel with the parallel small capacitor 2123 via the maintenance switch 213.

[0045] Figure 3 The flow chart of the charging control method of the embodiment of the present application is shown. The charging control method is executed by a charging control device. Figure 3 , the charging control method includes steps S310 to S340.

[0046] In step S310, the charging control device controls 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 perform charging in the first super-capacity charging stage.

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

[0048] According to an example embodiment, the first preset method may specifically be a method in which the charging control device controls the MMC converter to increase the DC side voltage by a preset value per unit time (i.e., at a fixed boost speed), first increasing the DC side voltage to a first preset voltage value, and then, after a preset duration, increasing the DC side voltage from the first preset voltage value to a preset system start-up voltage value at a fixed boost speed and maintaining the second preset duration unchanged.

[0049] The first preset method can also be that the charging control device controls the MMC converter to directly increase the DC side voltage continuously at a fixed boost speed to a preset starting voltage value, or it can be that the MMC converter is controlled to increase the DC side voltage in steps to a preset starting voltage value, which is not limited here.

[0050] According to an example embodiment, the preset system startup voltage value may be a voltage value required for normal operation of a central control board and a control system of the super-capacity module.

[0051] The central control board and control system of the super-capacity module can communicate and transmit data normally only when the voltage reaches 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 super-capacity charging stage, so that the voltage of the super-capacity module is charged to the central control board and the control system to operate normally and communicate.

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

[0054] In step S320, in the first super-capacity charging stage, the charging control device detects whether the super-capacity module voltage value of each of at least two super-capacity modules reaches a preset voltage limit.

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

[0056] In the case where the module voltage value of the non-overcapacity module is higher than or equal to the preset voltage limit, it indicates that there is no overcapacity module whose maintenance switch is not closed. The charging control device continues to monitor whether the module voltage value of the overcapacity module reaches the preset voltage limit until the first overcapacity charging stage ends or until it is detected that the module voltage value of the overcapacity module reaches the preset voltage limit.

[0057] When the module voltage value of an over-capacity module is higher than or equal to the preset voltage limit, it indicates that there is an over-capacity module whose maintenance switch is not closed.

[0058] In step S330, when there is an over-capacity module whose voltage value reaches the preset voltage limit, the charging control device controls the maintenance switch of the over-capacity module whose voltage value is higher than the preset voltage limit to be closed.

[0059] According to an example embodiment, in step S330, in the case where there is an over-capacity module whose voltage value reaches a preset voltage limit, that is, it indicates that the maintenance switch of the over-capacity module is not closed, so the charging control device can control the bypass switch of the over-capacity module whose maintenance switch is not closed to close, so as to bypass the over-capacity module whose maintenance switch is not closed, so that the over-capacity module whose maintenance switch is not closed no longer participates in subsequent charging, thereby reducing the probability of the over-capacity module being damaged due to continued charging of the over-capacity module that is not correctly connected to the maintenance switch.

[0060] And after the maintenance switch is controlled to be closed in the first super-capacity charging stage, the charging control device continues to detect whether the module voltage value of the super-capacity module reaches the preset voltage limit until the first super-capacity charging stage ends.

[0061] It is worth noting that the preset voltage limit is set by the user. The preset voltage limit may be a certain value, or may be determined according to the real-time voltage value of the DC side voltage.

[0062] Exemplarily, the preset voltage limit value may be a ratio of the DC link voltage to the number of super-capacity modules multiplied by k. In the case where the DC link voltage is higher, the preset voltage limit value is also higher.

[0063] In step S340, when the first super-capacity charging stage is completed, the charging control device controls 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 at least two super-capacity modules in the second super-capacity charging stage until it is detected that at least two super-capacity modules are fully charged.

[0064] According to the exemplary embodiment, after the first super-capacity charging stage is completed, each super-capacity module that is not normally connected to the maintenance switch has been bypassed, and the normal super-capacity modules can continue to be charged without damaging any super-capacity modules. Therefore, in step S340, the charging control device starts charging the super-capacity modules in the second super-capacity charging stage when the first super-capacity charging is completed.

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

[0066] According to an example embodiment, in step S340, in the second super-capacity charging stage, the charging control device increases the DC side voltage of the MMC converter from a preset system starting voltage value to a 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 super-capacity module is completed, thereby ending the second super-capacity charging stage.

[0067] According to an example embodiment, the second preset mode may specifically be to control the DC side voltage of the MMC converter to increase from a preset system starting voltage value to a preset charging voltage value at a fixed boost speed.

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

[0069] According to an example embodiment, the charging control device may detect whether the charging of the super-capacity module is completed by detecting whether the super-capacity module voltage value reaches the rated voltage (or 95% of the rated voltage). When the rated voltage is reached, it indicates that the charging of the super-capacity module is completed.

[0070] Through the above embodiment, the MMC converter is used to charge the super-capacity branch in the first super-capacity charging stage and the second super-capacity charging stage, and during the first super-capacity charging stage, the super-capacity module voltage value of each super-capacity module is continuously detected to see whether it reaches the preset voltage limit value, so as to detect whether the maintenance switch of each super-capacity module is closed. And in the case of detecting that there is a super-capacity module with an unclosed maintenance switch, the bypass switch corresponding to the super-capacity module is closed to bypass the super-capacity 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 the bypass module with the unclosed maintenance switch being damaged due to charging.

[0071] According to some embodiments, reference Figure 4In the above step S310, the charging control device controls the DC side voltage of the MMC converter to increase to a preset system starting voltage value in a first preset manner so as to charge at least two super-capacity modules in the first super-capacity 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 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.

[0073] According to an example embodiment, in step S311 , the charging control device controls the DC side voltage of the MMC converter to increase to a preset module starting 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 overcapacity module not connected to the maintenance switch, the overcapacity 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 overcapacity module can withstand.

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

[0076] Exemplarily, in step S311, the charging control device may control the switch device inside the MMC converter to be turned on or off to adjust the DC side voltage value of the MMC converter, so that the DC side voltage increases to a preset module starting voltage value at a first preset boost speed.

[0077] Exemplarily, in step S311, the DC side voltage is increased to the preset module starting voltage value according to the first preset boosting speed, which can be: the DC side voltage starts from 0, increases by 10V per second (the first preset boosting speed is 10V / s), and increases to 50V after 5 seconds.

[0078] In step S312, the charging control device starts to count a first duration, where the first duration is the duration during which the DC side voltage is maintained at a preset module starting voltage value.

[0079] In step S313, when detecting that the first duration reaches the first preset duration, the charging control device controls the DC side voltage of the MMC converter to increase to a preset system starting voltage value at a second preset boost speed.

[0080] In step S314, the charging control device starts counting the second duration, where the second duration is the duration during which the DC side voltage remains at the preset system starting voltage value;

[0081] In step S315 , the charging control device ends the charging in the first super-capacity charging stage when detecting that the second duration reaches the second preset duration.

[0082] According to an exemplary embodiment, in steps S311 to S315, the charging control device starts charging in the first super-capacity charging stage, raising the DC link voltage from 0V to a preset module starting voltage value, and then maintaining the DC link voltage at the preset module starting voltage value.

[0083] When the duration of maintaining the DC side voltage at the preset module starting voltage value reaches a first preset duration (that is, when the first continuous duration reaches the first preset duration), the charging control device controls the DC side voltage of the MMC converter to continue to increase on the basis of the preset module starting voltage value, and increases it to the preset system starting voltage value at a second preset boost speed.

[0084] Afterwards, the charging control device controls the DC side voltage to maintain the preset system starting voltage value unchanged until the time for maintaining the DC side voltage value at the preset system starting voltage value reaches a second preset time (that is, the second continuous time reaches the second preset time), so as to end the charging of the first super-capacity charging stage.

[0085] According to some embodiments, the preset system startup voltage value is determined according to a first startup voltage value of a central control board of the super-capacity module, a second startup voltage value of a management system of the super-capacity module, and a 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 be powered on and started. The second startup voltage value is the voltage value required for the management system to be powered on and started. The central control board can respond to the instructions of the management system to control the super-capacity module. The central control board and the management system need to meet certain voltage requirements when powered on and started. That is, the voltage value of the super-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 start and communicate normally.

[0087] The third starting voltage value is a voltage value required for the management system to realize the function of accurately identifying faults, and can be determined according to a starting setting value of fault judgment of the management system.

[0088] The management system can identify whether there is an abnormality in the super-capacity module, and if an abnormality is detected, the maintenance switch will be disconnected. However, if the voltage of the super-capacity module does not reach the third starting voltage value, the fault identification ability of the management system is poor, and the maintenance switch may be misclassified.

[0089] Therefore, in the first overcapacity charging stage, the charging control device first increases the DC side voltage to the preset system starting voltage value to ensure that the central control board and the overcapacity management system can be powered on and started, and the management system will not mistakenly classify the maintenance switch at this time.

[0090] It is worth noting that, during the charging process of the over-capacity branch, the charging control device needs to control the two turn-off switch devices (i.e., the first switch device and the second switch device) of each over-capacity module to be in the off state, so that each over-capacity module remains in a locked state.

[0091] According to some embodiments, Figure 5 The figure shows the steps of the charging control device controlling the MMC converter to perform the second super-capacity charging stage. Figure 5 In the above step S320, the charging control device controls 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 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. This can be specifically achieved through steps S321-S327.

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

[0093] In step S322, the charging control device controls the DC link voltage to maintain a preset charging voltage value.

[0094] In step S323, the charging control device detects the average voltage of the super-capacity module in the second super-capacity charging stage.

[0095] In step S324, the charging control device determines whether the average voltage of the super-capacity module reaches a preset voltage.

[0096] In step S325 , the charging control device determines whether the average voltage of the super-capacity module reaches a preset super-capacity rated charging voltage.

[0097] In step S326, when the average voltage of the super-capacity module reaches a preset voltage but does not reach the preset super-capacity rated charging voltage, the charging control device controls the super-capacity branch to remove a preset number of super-capacity modules in each super-capacity removal cycle based on the average voltage of the super-capacity module and the super-capacity module voltage values ​​of at least two super-capacity modules.

[0098] In step S327, when the average voltage of the super-capacity module reaches the preset super-capacity rated charging voltage, the charging control device completes the charging of the super-capacity module and ends the charging of the second super-capacity charging stage.

[0099] Exemplarily, after the charging control device increases the DC side voltage of the MMC converter to a preset system starting voltage value and maintains it for a second preset time, the first super-capacity charging stage ends and begins to enter the second super-capacity charging stage, that is, after the above-mentioned step S315, steps S321-S327 are executed.

[0100] During the entire second super-capacity charging stage from step S321 to step S327, the charging control device controls the DC side voltage of the MMC converter to increase from the preset system starting voltage value to the preset charging voltage value according to the third preset boosting speed, and after increasing to the preset charging voltage value, controls the DC side voltage of the MMC converter to maintain the preset charging voltage value unchanged.

[0101] The super-capacity branch receives the DC side voltage of the MMC converter and is continuously charged, so that the module voltage value of the super-capacity module is continuously increased, and then the average voltage of the super-capacity module of the super-capacity branch is continuously increased.

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

[0103] In the process of the charging control device controlling the DC side voltage output of the MMC converter, the charging control device also continuously detects the average value of the voltage of all the super-capacity modules of the super-capacity branch to detect the average voltage of the super-capacity modules.

[0104] In step S324 and step S325, the charging control device determines whether the average voltage of the super-capacity module reaches a preset voltage and whether it reaches a preset super-capacity 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 determined specifically according to the number of super-capacity modules before removal and the preset charging voltage value. For example, in a static synchronous condenser system, 40 super-capacity modules are provided, and the preset charging voltage value is 20KV. In the second super-capacity charging stage, each super-capacity module should be charged to at least 500V, 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 super-capacity modules before removal.

[0106] The preset super-capacity rated charging voltage is the rated charging voltage of the super-capacity module.

[0107] When the super-capacity module is continuously charged, so that the average voltage of the super-capacity module increases to the preset voltage, and does not reach the preset super-capacity rated charging voltage, the super-capacity module needs to continue to be charged. In this case, in step S326, the charging control device can control the super-capacity branch to remove the super-capacity modules of the preset super-capacity removal number in each super-capacity removal cycle according to the average voltage of the super-capacity module and the super-capacity module voltage value of each super-capacity module.

[0108] Exemplarily, in step S326, when the average voltage of the super-capacity module rises to the preset voltage, the charging control device begins to enter the first super-capacity removal cycle, and at the initial moment of the super-capacity removal cycle, removes a preset number of super-capacity removal modules in the super-capacity branch (for example, removes 1 super-capacity module from 5 super-capacity modules), and the removed super-capacity modules will not participate in charging in the current super-capacity removal cycle, and the MMC converter will charge the remaining super-capacity modules that have not been removed.

[0109] After the preset over-capacity removal cycle duration has passed, the first over-capacity removal cycle ends and enters the second over-capacity removal cycle. At the initial moment of the second over-capacity removal cycle, a preset number of over-capacity removal over-capacity modules are selected from each over-capacity module of the over-capacity branch for removal (for example, 1 over-capacity module is removed from 5 over-capacity modules). The over-capacity modules removed in the second over-capacity removal cycle and the first over-capacity removal cycle may be the same or different, and are not limited here. The over-capacity modules removed in the second over-capacity removal cycle will not participate in charging in the second over-capacity removal cycle, and the MMC converter will charge the over-capacity modules that have not been removed.

[0110] The above method is used in a similar manner until it is detected that the average voltage of the super-capacity module increases to the preset super-capacity rated charging voltage, that is, it is detected that the charging of the super-capacity module is completed.

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

[0112] It is worth noting that the order of the above-mentioned steps S324 and S325 can be step S324 first and step S325 later, or step S324 and step S325 can be executed simultaneously, or step S325 can be first and step S324 later, which is not limited here.

[0113] According to some embodiments, reference Figure 6 In the above step S326, the charging control device controls the super-capacity branch to remove a preset number of super-capacity removal modules in each super-capacity removal cycle according to the super-capacity module average voltage and the super-capacity module voltage values ​​of each super-capacity 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-capacity module is within a preset over-capacity charging voltage range in the current over-capacity removal period.

[0115] In step S3262, when the average voltage of the super-capacity module is lower than the lower limit of the preset super-capacity charging voltage range, the charging control device increases the first preset number based on the super-capacity removal number of the previous super-capacity removal cycle to determine the super-capacity removal number of the current super-capacity removal cycle.

[0116] In step S3263, when the average voltage of the super-capacity module is in the preset super-capacity charging voltage range, the charging control device determines the super-capacity removal number of the previous super-capacity removal cycle as the super-capacity removal number of the current super-capacity removal cycle.

[0117] In step S3264, the charging control device selects the target super-capacity module for the current super-capacity removal cycle from the at least two super-capacity modules according to their respective super-capacity module voltage values, and the number of the target super-capacity modules is the super-capacity removal number of the current super-capacity removal cycle.

[0118] In step S3265, the charging control device removes the target-removed super-capacity module from the super-capacity branch to charge the remaining super-capacity modules.

[0119] According to an exemplary embodiment, the upper limit of the preset over-capacity charging voltage interval may be the preset over-capacity rated charging voltage, and the lower limit of the preset over-capacity charging voltage interval may be 0.95 times the preset over-capacity rated charging voltage.

[0120] For example, assuming that the static synchronous condenser system has an overcapacity branch, which includes four overcapacity modules. When the charging control device detects that the average voltage of the overcapacity module rises to a preset voltage, it enters the first overcapacity removal cycle and determines whether the average voltage of the overcapacity module is within the preset overcapacity charging voltage interval.

[0121] At this time, the average voltage of the supercapacitor module is lower than the lower limit of the preset supercapacitor charging voltage range. Since this is the first supercapacitor removal cycle, the supercapacitor removal number of the first supercapacitor removal cycle is the preset supercapacitor removal number, for example, it can be 1 or 0. The following example is taken as an example of the supercapacitor removal number of the first supercapacitor removal cycle being 1.

[0122] The charging control device selects one super-capacity module with the highest super-capacity module voltage value from the four super-capacity modules according to the super-capacity module voltage values ​​of each super-capacity module as the target super-capacity module to be removed, such as super-capacity module a1. The charging control device removes the target super-capacity module from the super-capacity branch, and the remaining three super-capacity modules are charged in the first super-capacity removal cycle, and the target removed super-capacity module is not charged.

[0123] When the first over-capacity removal cycle ends, the second over-capacity removal cycle begins, and the charging control device determines that the average voltage of the over-capacity module is lower than the lower limit of the preset over-capacity charging voltage range. Therefore, the over-capacity removal number determined by the charging control device for the second over-capacity removal cycle is 2 (assuming the first preset number is 1). The charging control device selects two over-capacity modules from the four over-capacity modules in order from large to small according to the over-capacity module voltage values ​​of the four over-capacity modules as the target over-capacity modules for the second over-capacity removal cycle, such as over-capacity module a2 and over-capacity module a3, that is, the over-capacity module voltage values ​​of the two target over-capacity modules selected are not less than the over-capacity module voltage values ​​of other over-capacity modules.

[0124] When selecting the target to remove the overcapacity module, the charging control device can select the overcapacity modules in descending order of voltage value. That is, in the current overcapacity removal cycle, the charging control device first removes the overcapacity module with a large overcapacity module voltage value in the current state.

[0125] In the second over-capacity removal cycle, the charging control device removes the target over-capacity module of the second over-capacity removal cycle (for example, removes over-capacity module a2 and over-capacity module a3), and the remaining over-capacity modules (over-capacity module a1 and over-capacity module a4) are charged in the second over-capacity removal cycle.

[0126] It is worth noting that the target over-capacity removal modules in different over-capacity removal cycles may be different.

[0127] After the second overcapacity removal cycle, the third overcapacity removal cycle is entered. Assume that in the third overcapacity removal cycle, the charging control device determines that the average voltage of the overcapacity module is in the preset overcapacity charging voltage range. In this case, the charging control device determines that the overcapacity removal number of the third overcapacity removal cycle remains the same as the overcapacity removal number of the second overcapacity removal cycle, that is, 2.

[0128] The charging control device selects two super-capacity modules from the four super-capacity modules as target super-capacity modules to be removed in the third super-capacity removal cycle, for example, super-capacity modules a2 and super-capacity modules a4. The charging control device removes the target super-capacity modules from the super-capacity branch, and the remaining super-capacity modules participate in charging in the third super-capacity removal cycle. The above steps S3261 to S3265 are continuously executed in this way.

[0129] It is worth noting that after the third overcapacity removal cycle ends, the fourth overcapacity removal cycle begins. At this time, the average voltage of the overcapacity module is already in the preset overcapacity charging voltage range, and the number of overcapacity removals in subsequent overcapacity removal cycles remains at 2. Two overcapacity modules are removed in each overcapacity removal cycle, but the removed overcapacity modules are different. In this case, the average voltage of the overcapacity module can eventually stabilize at the preset rated overcapacity charging voltage, so that the overcapacity branch completes the charging process.

[0130] According to an example embodiment, referring to Figure 2 , the removal of the super-capacitor module 21 can be achieved by controlling the second switch device 2122 of the super-capacitor sub-module 212 to be turned on.

[0131] According to some embodiments, reference Figure 7 , the charging control method also includes steps S710 to S730.

[0132] In step S710, upon receiving a fault instruction transmitted by the management system of the over-capacity module, the charging control device determines the faulty over-capacity module according to the fault instruction.

[0133] According to an example embodiment, the fault disconnection instruction is an instruction generated by the management system when it is detected that an abnormality occurs in an over-capacity module.

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

[0135] In step S730 , the charging control device controls the maintenance switch of the faulty over-capacity module to be turned off to trip the faulty over-capacity module.

[0136] According to an example embodiment, the steps S710 to S730 are performed simultaneously with the above-mentioned steps S3261 to S3265.

[0137] After the first super-capacity charging stage, the management system and central control board of the super-capacity module can operate normally. During the second super-capacity charging stage, if the management system detects that the super-capacity module is faulty, it will generate a fault instruction to indicate to the charging control device that the super-capacity module is faulty, and the identification or identity information of the faulty super-capacity module will be carried in the fault instruction and transmitted to the charging control device to indicate to the charging control device that the super-capacity module is faulty.

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

[0139] According to some embodiments, reference Figure 1 The static synchronous phase condenser system also 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 over-capacity branch 2 and the DC side of the MMC converter 1 to control the on-off of the over-capacity 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 an AC circuit breaker 4 and a 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, each of which is cascaded with at least two converter submodules 11. Figure 1 In the example shown, the MMC converter 1 includes six bridge arms, and each bridge arm is provided with three cascade-connected converter submodules 11 .

[0143] Figure 8 FIG. 1 shows a structural example of the commutation submodule 11. Figure 8 The commutation submodule 11 may be a full-bridge submodule, which includes a first full-bridge switch device 81 , a second full-bridge switch device 82 , a third full-bridge switch device 83 , a fourth full-bridge switch device 84 and a full-bridge capacitor 85 .

[0144] Fig. 9 Another structural example of the commutation submodule 11 is shown. Fig. 9 The commutation submodule 11 may also be a half-bridge submodule. The half-bridge submodule includes a first half-bridge switch device 91 , a second half-bridge switch device 92 and a half-bridge capacitor 93 .

[0145] In the charging control method of the embodiment of the present application, before charging the over-capacity branch, the MMC converter can be charged by using the external power grid, and after the MMC converter is charged, the above step S310 is performed.

[0146] Fig.10 The steps of charging the MMC converter are shown. That is, before the above step S310, the charging control method may further include steps S1010 to S1080.

[0147] In step S1010, the charging control device controls the DC side switch to be turned off, so that the connection between the DC side of the MMC converter and the excess capacity branch is disconnected, so as to charge the MMC converter first.

[0148] In step S1020 , the charging control device controls the start switch to be turned off.

[0149] In step S1030, the charging control device controls each inverter submodule of the MMC inverter to be in a locked state.

[0150] According to an example embodiment, referring to Figure 8 and Fig. 9 When the commutation submodule 11 is a full-bridge submodule, 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 the off state, so that the full-bridge submodule is in a locked state.

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

[0152] It is worth noting that the execution order of step S1020 and step S1030 can be to execute step S1020 first and then execute step S1030, or to execute step S1030 first and then execute step S1020, or to execute step S1020 and step S1030 at the same time, which is not limited here.

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

[0154] In step S1010-step S1040, the charging control device disconnects the starting switch, disconnects the DC side switch, controls each converter module to be in a locked state, and closes the AC circuit breaker, so that the external power grid can start charging 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 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.

[0156] According to an exemplary embodiment, the preset module energy-taking voltage value is a voltage value required for the commutation submodule to have communication and identification capabilities. The preset module energy-taking voltage value may specifically be 0.95*U lmax / (2*N).U lmax is the peak value of the power frequency side line voltage, and N is the number of the commutation submodules of each bridge arm. The preset current limit value may specifically be 0.1 pu.

[0157] The total average voltage of the bridge arm is the average of all bridge arm voltages. For example, the MMC converter has 6 bridge arms, each bridge arm is composed of 3 converter modules, and the total average voltage of the bridge arm is the average voltage of 18 converter modules. The total average voltage of the bridge arm can be obtained by measuring the total voltage of each bridge arm and calculating its average.

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

[0159] In step S1060, the charging control device controls the start switch to close, so as to start charging the MMC converter in the second commutation charging stage.

[0160] When the first commutation charging stage ends, the MMC converter starts charging in the second commutation charging stage. In step S1060, when the first commutation charging stage ends, the charging control device controls the start switch to close and the start resistor to short-circuit, so that the charging current increases and the charging speed is accelerated, and the MMC converter starts charging in the second commutation stage until it is detected that the charging of each commutation submodule is completed and the second commutation charging stage ends.

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

[0162] In step S1080, when the total average voltage of the bridge arm reaches the preset commutation rated charging voltage, the charging control device completes the charging of each commutation sub-module of the MMC converter to end the charging of the second commutation charging stage.

[0163] According to an exemplary embodiment, in the second commutation charging stage, the charging control device detects whether the total average voltage of the bridge arm reaches a 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. In addition, during the charging process, the charging control device can also remove the commutation submodules of the MMC converter in each commutation removal cycle according to the total average voltage of the bridge arm and the commutation module voltage value of each commutation submodule, in accordance with the method of removing the commutation submodules of the preset commutation removal number of each bridge arm, so as to speed up the charging process of the MMC converter.

[0166] Exemplarily, when the MMC converter enters the second commutation charging stage, that is, enters the first commutation removal cycle, and at the initial moment of the commutation removal cycle, the charging control device removes a preset number of commutation removal sub-modules in each bridge arm of the MMC converter.

[0167] For example, the MMC converter has six bridge arms, and the preset removal quantity is 1, then one converter sub-module is removed from each bridge arm, and the MMC converter removes a total of six converter sub-modules.

[0168] The removed commutation sub-module will not participate in charging in the current commutation removal cycle, and the external power grid will only charge the remaining commutation sub-modules that have not been removed.

[0169] After the preset commutation removal period has passed, the first commutation removal period ends and the second commutation removal period begins. At the beginning of the second commutation removal period, the charging control module re-removes the preset commutation removal number of commutation sub-modules in each bridge arm.

[0170] The commutation sub-modules removed in the second commutation removal period and the first commutation removal period may be the same or different, which is not limited here.

[0171] In the above manner, in each commutation removal cycle, a preset number of commutation removal submodules are reselected from all commutation submodules of all bridge arms for removal. In this way, the commutation submodules that have not been removed can be charged during the commutation removal cycle, and the commutation submodules can be replaced for charging in the next commutation removal cycle. Compared with directly charging all commutation submodules at the same time, this batch charging method has a faster charging speed.

[0172] According to some embodiments, Fig.11 The step flow of removing the commutation submodule in step S1070 is shown. Fig.11 , the above-mentioned step S1070 may include steps S1071 to S1075.

[0173] In step S1071, the charging control device determines whether the total average voltage of the bridge arm is in 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 of the preset commutation charging voltage range, the charging control device increases the commutation removal number of the previous commutation removal cycle by a second preset number to determine the commutation removal number of the current commutation removal cycle.

[0175] In step S1073, when the total average voltage of the bridge arm is in the preset commutation charging voltage interval, the charging control device determines the commutation removal number of the previous commutation removal cycle as the commutation removal number of the current commutation removal cycle.

[0176] In step S1074, the charging control device selects the target cut-off commutation sub-modules of the current commutation cut-off period corresponding to each bridge arm from each bridge arm according to the commutation module voltage value of each commutation sub-module, and the number of target cut-off commutation sub-modules corresponding to each bridge arm is the commutation cut-off number of the current commutation cut-off period.

[0177] In step S1075 , the charging control device removes the target-removed commutation sub-module.

[0178] For example, an MMC converter has six bridge arms, and each bridge arm is provided with three commutation submodules. When the charging control device enters the second commutation charging stage, it enters the first commutation removal cycle.

[0179] At the beginning of the first commutation removal cycle, the charging control device executes step S1071 to determine whether the current total average voltage of the bridge arm is in the preset commutation charging voltage range. Since the current commutation cycle is the first commutation removal cycle, in the first commutation removal cycle, regardless of whether the current total average voltage of the bridge arm is lower than the preset commutation charging voltage range, the commutation removal number of the first commutation removal cycle is the preset removal number. The preset removal number can be 1 or 0, which is not limited here. The following example is taken as an example of the commutation removal number of 0 in the first commutation removal cycle.

[0180] In the first commutation removal cycle, each bridge arm does not remove the commutation submodule. After the preset commutation removal cycle duration, the second commutation removal cycle is entered, and the charging control device executes step S1071.

[0181] At the beginning of the second commutation removal cycle, the charging control device determines that the current total average voltage of the bridge arm is lower than the lower limit of the preset commutation charging voltage range, and executes step S1072, and the commutation removal number of the second commutation removal cycle determined by the charging control device is 1 (assuming that the second preset number is 1).

[0182] Then, step S1074 is executed, and the charging control device selects one commutation submodule from the first bridge arm, one commutation submodule from the second bridge arm, and one commutation submodule from the sixth bridge arm according to the commutation module voltage values ​​of the commutation submodules, so as to determine six target commutation submodules to be removed. Then, in step S1075, the charging control device removes the six target commutation submodules to be removed.

[0183] After the preset commutation removal cycle duration, the third commutation removal cycle is entered, and the charging control device executes step S1071-step S1075 in a loop. For example, if the total average voltage of the bridge arm at the beginning of the third commutation removal cycle is in the preset commutation charging voltage range, the commutation removal quantity of the third commutation removal cycle is also 1. The charging control device selects 1 commutation submodule from the 3 commutation submodules in the first bridge arm, selects 1 commutation submodule from the 3 commutation submodules in the second bridge arm... and selects 1 commutation submodule from the 3 commutation submodules in the sixth bridge arm for removal.

[0184] The same process is repeated until the total average voltage of the bridge arm reaches the preset commutation rated charging voltage, each commutation sub-module completes charging, and the second commutation charging stage ends.

[0185] According to an example embodiment, in the above step S1074, the charging control device selects the target removal commutation submodules of the current commutation removal period corresponding to each bridge arm from each bridge arm according to the commutation module voltage value of each commutation submodule, and selects them in order from large to small commutation module voltage values. That is, in the current commutation removal period, the charging control device preferentially removes the commutation submodules with larger current commutation module voltage values.

[0186] It is worth noting that the target commutation modules to be removed in different commutation removal cycles may be different.

[0187] According to an example embodiment, referring to Fig. 9 The charging control device may cut off the commutation submodule 11 by controlling the second half-bridge switch device 92 of the half-bridge submodule when the commutation submodule 11 is a half-bridge submodule.

[0188] Reference Figure 8In the case where the commutation submodule 11 is a full-bridge submodule, the charging control device can cut off the commutation submodule by controlling the second full-bridge switch device 82 and the fourth full-bridge switch device 84 to be turned on, or controlling the first full-bridge switch device 81 and the third full-bridge switch device 83 to be turned on.

[0189] Reference Figure 8 That is, the two switch devices directly connected to the negative electrode of the capacitor in the full-bridge submodule are turned on at the same time, and the other two switch devices remain locked, or the two switch devices directly connected to the positive electrode of the capacitor are turned on at the same time, and the other two switch devices remain locked. One switch device directly connected to the negative electrode of the capacitor in the half-bridge submodule is turned on, and the other switch device remains locked. In this way, the commutation submodule 11 can be removed.

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

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

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

[0193] like Fig.12 As shown, the charging control device may include: the charging control device includes a first super-capacity charging stage control module 1201, a first super-capacity charging stage detection module 1202, and a second super-capacity charging stage control module 1203.

[0194] The first supercapacity charging stage control module 1201 is used to control the DC side voltage of the MMC converter to increase to the preset system starting voltage value according to the first preset method, so as to charge at least two supercapacity modules in the first supercapacity charging stage. The first supercapacity charging stage detection module 1202 is used to detect whether the supercapacity module voltage value of each of at least two supercapacity modules is higher than the preset detection value in the first supercapacity charging stage; and in the case of a supercapacity module whose supercapacity module voltage value is higher than the preset voltage limit, control the bypass switch of the supercapacity module whose supercapacity module voltage value is higher than the preset voltage limit to close, so as to bypass the supercapacity module whose supercapacity module voltage value is higher than the preset voltage limit. The second supercapacity charging stage control module 1203 is used to control the DC side voltage of the MMC converter to increase to the preset charging voltage value according to the second preset method when the first supercapacity charging stage ends, so as to charge at least two supercapacity modules in the second supercapacity charging stage, until it is detected that each supercapacity module has been fully charged.

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

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

[0197] According to another aspect of the present application, the embodiment of the present application also introduces a charging control device from the perspective of a physical device. Fig.13 , Fig.13 The charging control device shown includes: a processor 1301 and a memory 1303. The processor 1301 and the memory 1303 are connected, such as through a bus 1302. Optionally, the charging control device may also include a transceiver 1304. It should be noted that in actual applications, the transceiver 1304 is not limited to one, and the structure of the charging control device does not constitute a limitation on the embodiments of the present application.

[0198] 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 may implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of this application. 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 to transmit information between the above components. The bus 1302 may be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus. The bus 1302 may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Fig.13 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0200] The memory 1303 can be a ROM (Read Only Memory) or other types of static storage devices that can store static information and instructions, a RAM (Random Access Memory) or other types of dynamic storage devices that can store information and instructions, or an EEPROM (Electrically Erasable Programmable Read Only Memory), a CD-ROM (Compact Disc Read Only Memory) or other optical disk storage, optical disk storage (including compressed optical disk, laser disk, optical disk, digital versatile disk, Blu-ray disk, etc.), a magnetic disk storage medium or other magnetic storage device, 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 to these.

[0201] The memory 1303 is used to store the application code for executing the solution of the present application, and the execution is controlled by the processor 1301. The processor 1301 is used to execute the application code stored in the memory 1303 to implement the contents shown in the above method embodiment.

[0202] According to another aspect of the present application, an embodiment of the present application provides a non-volatile computer-readable medium, on which a computer program is stored, and when the computer-readable medium is run on a computer, the computer can execute the corresponding content in the aforementioned method embodiment. The storage medium can be a read-only memory, a disk or an optical disk, etc.

[0203] According to another aspect of the present application, an embodiment of the present application provides a computer program product. The computer program product includes a computer program stored on a computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the corresponding content in the aforementioned method embodiment.

[0204] Finally, it should be noted that the above are only preferred embodiments of the present application and are not intended to limit the present application. Although the present application is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions of the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present 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 required for the management system 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 1-7.

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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