MMC-type statcom system

Abstract

The present invention relates to an MMC-type STATCOM system. The MMC-type STATCOM system according to an embodiment of the present invention comprises: a plurality of sub-modules; a plurality of sub-module interfaces (SMIs) that respectively correspond to the plurality of sub-modules and receive status information from the corresponding sub-modules; and a VBE controller that receives the status information of the sub-modules from the plurality of SMIs and diagnoses the status of each submodule on the basis of the received status information, wherein the VBE controller determines the number of failed sub-modules from among the plurality of sub-modules on the basis of the received status information, and when the determined number of sub-modules is greater than a preset number, calculates an index for determining whether or not it is operable.

Description

MMC-type STATCOM system

[0001] The present invention relates to an MMC type STATCOM system, and relates to an MMC type STATCOM system capable of improving the operating rate when a sub-module fails.

[0002] STATCOM, a type of flexible AC transmission system (FACTS), is a representative reactive power compensation power device along with SVC (Static Var Compensator). This device is connected in parallel to the power system and compensates for reactive power, ultimately increasing voltage stability and transmission efficiency and resolving power generation or transmission constraints. Many devices are installed and operated domestically and internationally.

[0003] Advances in the power electronics field have enabled the use of power electronic components such as IGBTs and Thyristors in transmission-grade power equipment. Based on this power electronics technology and the advanced logic circuit technology such as FPGAs and DSPs, the 4th generation Modular Multilevel Converter (MMC) has been developed, leading to advancements in the performance, reliability, and efficiency of FACTS.

[0004] The MMC type STATCOM system (MMC STATCOM) covered by the present invention comprises a number of full bridge submodules (Full bridge SMs (SubModules)) connected in series. In addition to SMs #1 to #N used for rated output among the serially connected SMs, there are additionally connected spare SMs, which are installed to be immediately brought in when a failure occurs in a specific SM to maintain continuous operation of the power equipment.

[0005] In reality, continuous operation is possible under actual conditions even if the SM (Sub Module) fails more than the spare number, but there is a problem that the operating rate is lowered due to unnecessary equipment stoppage due to harsh design conditions.

[0006] The present invention aims to solve the above-mentioned problems and other problems.

[0007] One object of the present invention is to improve the operating rate in an optimized manner even when a failure occurs in a submodule.

[0008] Another object of the present invention is to improve the continuous operation rate by determining whether actual operation is possible even if the sub-modules of the MMC STATCOM are broken beyond the spare number.

[0009] According to one aspect of the present invention to achieve the above or other purposes, an MMC type STACOM system according to an embodiment of the present invention includes a plurality of sub-modules, a plurality of SMIs (Sub-Module Interfaces) corresponding to each of the plurality of sub-modules and receiving status information from the corresponding sub-modules, and a VBE controller receiving status information of the sub-modules from the plurality of SMIs and diagnosing the status of each sub-module based on the received status information, wherein the VBE controller determines the number of faulty sub-modules among the plurality of sub-modules based on the received status information, and when the number of determined sub-modules is greater than a preset number, calculates an index for determining whether or not operation is possible.

[0010] In an embodiment, the plurality of sub-modules include at least one spare sub-module, and the VBE controller is characterized in that it calculates an index for determining whether operation is possible when a number of sub-modules among the plurality of sub-modules is faulty, which is greater than the number of spare sub-modules.

[0011] In an embodiment, the VBE controller is characterized in that, when the number of sub-modules determined to be faulty is greater than a preset number, it calculates an index that can compare the operable area and the required operable area, and, using the calculated index, maintains continuous operation when the operable area is wider than the required operable area.

[0012] In an embodiment, the VBE controller is characterized in that it calculates an index for determining whether driving is possible in different ways when driving with an inductive output and when driving with a capacitive output.

[0013] In an embodiment, the VBE controller is characterized in that, when driving an inductive output, it calculates a first index (Index_L) for determining whether driving is possible through the following [Mathematical Formula 1].

[0014] [Mathematical Formula 1]

[0015]

[0016] Here, V_(PCC_MAX) is the maximum voltage of the MMC STATCOM connection point (PCC), V_(MMC_MAX) is the maximum output voltage of the MMC STATCOM, and Z_STATCOM is the impedance of the MMC STACOM.

[0017] In an embodiment, the VBE controller is characterized in that, when driving a capacitive output, it calculates a second index (Index_C) for determining whether driving is possible through the following [Mathematical Formula 2].

[0018] [Equation 2]

[0019]

[0020] Here, V_ref is the MMC STATCOM link point reference value, V_(MMC_MAX) is the MMC STATCOM maximum output voltage, and Z_STATCOM is the impedance of the MMC STACOM.

[0021] In an embodiment, the VBE controller is characterized in that it stops STATCOM operation when the value of the first index is greater than 1.

[0022] In an embodiment, the VBE controller is characterized in that it stops STATCOM operation when the value of the second index is greater than -1.

[0023] The effects of the mobile terminal and its control method according to the present invention are described as follows.

[0024] According to at least one of the embodiments of the present invention, when a sub-module (SM) of an MMC STATCOM fails beyond the reserve quantity, the present invention can improve the operating rate of the equipment by calculating an index that can compare the operable area and the required operating area and maintaining continuous operation using the index, instead of stopping the equipment as in the prior art.

[0025] FIG. 1 is a block diagram illustrating the configuration of a STATCOM of the MMC method according to an embodiment of the present disclosure.

[0026] Figure 2 is a block diagram illustrating the structure of SMI.

[0027] FIG. 3 and FIG. 4 are circuit diagrams for explaining the MMC STATCOM structure of the present invention.

[0028] Figure 5 is a flowchart for explaining a control method of MMC STATCOM in case of a conventional submodule failure.

[0029] Figure 6 is a flowchart for explaining a control method of MMC STATCOM when a sub-module of the present invention fails.

[0030] Figures 7, 8, and 9 are graphs for explaining the control method discussed in Figure 6.

[0031] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components will be given the same reference numbers and redundant descriptions thereof will be omitted. The suffixes "module" and "part" used for components in the following description are assigned or used interchangeably only for the convenience of writing the specification, and do not in themselves have distinct meanings or roles. In addition, when describing the embodiments disclosed in this specification, if it is determined that a specific description of a related known technology may obscure the gist of the embodiments disclosed in this specification, a detailed description thereof will be omitted. In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

[0032] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0033] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0034] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0035] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0036] FIG. 1 is a block diagram illustrating the configuration of a STATCOM of the MMC method according to an embodiment of the present disclosure.

[0037] An MMC-type STATCOM system (or MMC STATCOM) may be a reactive power compensation device that converts current using a modular multi-level converter (MMC). An MMC-type STATCOM consists of a large number (tens to hundreds) of submodules, and can collect status information from the submodules within a short control cycle (e.g., 100 to 200 microseconds) and determine which submodules should be turned on or off in the next control cycle.

[0038] As illustrated in Fig. 1, the MMC-type STATCOM includes an upper controller (1) and a modular multi-level converter, and the modular multi-level converter can be composed of a VBE (Valve Base Electronics) controller (2), a plurality of sub-modules (SM_1 to SM_n), and a plurality of SMI (Sub-Module Interfaces, SMI_1 to SMI_n).

[0039] The upper controller (1) can control the overall operation of the MMC-type STATCOM. According to one embodiment, the upper controller (1) can be a C&P (Control and Protection) system that performs operations for controlling and protecting the STATCOM. In addition, in the drawing, the VBE controller (2) and the upper controller (1) are depicted separately, but according to the embodiment, the upper controller (1) can be a VBE

[0040] It may be a concept including a controller (2).

[0041] The VBE controller (2) can control multiple submodules (SM_1 to SM_n).

[0042] The VBE controller (2) can receive status information of each sub-module in order to control a plurality of sub-modules (SM_1 to SM_n). That is, the VBE controller (2) can receive status information of the sub-module and diagnose the status of the sub-module based on the status information of the sub-module. Based on the diagnosis result, the VBE controller (2) can control the sub-module in which a failure has occurred from the target of the control algorithm.

[0043] It can be excluded. And, the VBE controller (2) can control the turn-on and turn-off timing of each sub-module so that the sub-modules in the normal state can switch.

[0044] The VBE controller (2) can transmit commands to control each submodule to the submodule or SMI.

[0045] Meanwhile, in the present specification including FIG. 1, a plurality of sub-modules (SM_1 to SM_n) and a plurality of SMIs (SMI_1 to SMI_n) are depicted as separate configurations, but this is merely a distinction made for convenience of explanation, and a plurality of SMIs (SMI_1 to SMI_n) may also be understood as a concept included in a plurality of sub-modules (SM_1 to SM_n).

[0046] A plurality of sub-modules (SM_1 to SM_n) may be connected in series. In this case, a plurality of sub-modules connected to any one phase of a three-phase system may form a cluster. The cluster may be referred to as a valve according to an embodiment, and in this case, the VBE controller (2) may be referred to as a valve controller.

[0047] According to one embodiment, the modular multilevel converter may be a three-phase MMC, which may be configured with three clusters. Specifically, it may be configured with an A-phase cluster (3), a B-phase cluster (4), and a C-phase cluster (5) for each of the three phases, i.e., phases A, B, and C. The clusters, which are configured with a plurality of sub-modules (SM_1 to SM_n), may be connected to the three phases of the power system, i.e., phases A, B, and C, respectively.

[0048] Each of the plurality of SMIs (SMI_1 to SMI_n) is connected to each of the plurality of sub-modules (SM_1 to SM_n) and receives status information of the sub-modules from each of the sub-modules. That is, each of the plurality of SMIs (SMI_1 to SMI_n) is connected to each of the plurality of sub-modules (SM_1 to SM_n) and can receive status information from the corresponding sub-module. Specifically, the first

[0049] The SMI (SMI_1) corresponds to the first sub-module (SM_1), the second SMI (SMI_2) corresponds to the second sub-module (SM_2), ... the n-th SMI (SMI_n) may correspond to the n-th sub-module (SM_n).

[0050] However, depending on the embodiment, one SMI may be correspondingly connected to two or more sub-modules and may receive status information from two or more sub-modules.

[0051] And, here, 'connected' can mean not only being directly connected by wire, but also being indirectly connected wirelessly so that information or commands can be transmitted and received.

[0052] The VBE controller (2) diagnoses the status of each sub-module through multiple SMIs (SMI_1 to SMI_n) and excludes a sub-module in which a failure has occurred from the control algorithm. The VBE controller (2) can directly diagnose a communication problem with the SMI (or sub-module) and a switching frequency problem of the sub-module and exclude them from the control algorithm. For example, the VBE controller (2)

[0053] Since signals are transmitted and received with the SMI at each control cycle, if a signal is not received within a certain period of time or a checksum error occurs, it is determined that a problem has occurred and an off signal is sent to the corresponding submodule, thereby excluding it from the control algorithm.

[0054] Meanwhile, for internal submodule failures, the SMI receives status information about the submodule and determines whether to exclude it from the control algorithm. If the SMI determines that a submodule is faulty, it can send an off signal to the submodule, simultaneously excluding it from the control algorithm.

[0055]

[0056] Figure 2 is a block diagram illustrating the structure of SMI.

[0057] As shown in Fig. 2, SMI (10) may include a processor (11), a submodule communication unit (12), and a VBE communication unit (13).

[0058] The processor (11) can control the operation of the SMI (10). The processor (11) can control the submodule communication unit (12) and the VBE communication unit (13).

[0059] The submodule communication unit (12) can receive status information from the submodule. In addition, the submodule communication unit (12) can transmit a control command received through the VBE communication unit (13) to the submodule.

[0060] The VBE communication unit (13) can transmit status information of the sub-module to the VBE controller (2) and receive control commands for the sub-module from the VBE controller (2).

[0061] Specifically, the submodule communication unit (12) can receive status information of the submodule. That is, the submodule communication unit (12) can receive status information of the submodule from the submodule corresponding to the corresponding SMI.

[0062] The processor (11) can determine whether a submodule is faulty based on the status information of the submodule. If the processor (11) determines that a fault has occurred in a submodule, the processor (11) can exclude the submodule from the control algorithm.

[0063] If the processor (11) determines that a sub-module has not failed, it can transmit status information of the sub-module to the VBE controller (2).

[0064] FIG. 3 and FIG. 4 are circuit diagrams for explaining the MMC STATCOM structure of the present invention.

[0065] Referring to FIG. 3, the MMC STATCOM covered in the present invention is a power device that is connected in parallel to a power system to supply or absorb reactive power and maintain power factor, voltage, etc., and is used for the purpose of maintaining stability of the power system.

[0066] MMC STATCOM is a 4th generation reactive power compensation device.

[0067] The MMC STATCOM has multiple full bridge submodules connected in series, as shown in Fig. 4. In addition to the multiple submodules (SM #1 to SM #N) used for rated output among the serially connected submodules, there are additionally connected spare submodules (spare SM #1 to spare SM #N), which are installed to immediately take over and maintain continuous operation of the power equipment in the event of a failure in a specific SM.

[0068] The MMC STATCOM of the present invention includes a plurality of sub-modules, a plurality of SMIs (Sub-Module Interfaces) corresponding to each of the plurality of sub-modules and receiving status information from the corresponding sub-modules, and a VBE controller receiving status information of the sub-modules from the plurality of SMIs and diagnosing the status of each sub-module based on the received status information.

[0069] Figure 5 is a flowchart for explaining a control method of MMC STATCOM in case of a conventional submodule failure.

[0070] Referring to Fig. 5, while the MMC STATCOM is running (S510), the VBE controller (2) can receive status information of a plurality of sub-modules and determine the number of faulty sub-modules (Qty_(SM_F)) among the plurality of sub-modules based on the received status information (S520).

[0071] As previously explained, multiple submodules may include spare submodules.

[0072] Conventionally, when the number of faulty submodules (Qty_(SM_F)) of MMC STATCOM becomes greater than the number of spare submodules (Qty_(SM_Red)) (S530), the operation of MMC STATCOM can be stopped (S540).

[0073] Meanwhile, according to the conventional control method, even if the sub-modules of the MMC STATCOM fail beyond the spare number, continuous operation is possible under actual conditions, but the problem of low operating rate occurs as the equipment is unnecessarily stopped due to harsh design conditions.

[0074] The present invention calculates an index that can compare an operable area and a required operating area without stopping the system as in the prior art when a sub-module of an MMC STATCOM fails beyond the reserve quantity, and uses the index to maintain continuous operation when the operable area is wider than the required operating area, thereby improving the operating rate of the equipment.

[0075] To this end, the VBE controller (2) of the MMC STATCOM of the present invention can determine the number of faulty sub-modules among the plurality of sub-modules based on the received status information, and, if the number of determined sub-modules is greater than a preset number, calculate an index for determining whether operation is possible.

[0076] The above plurality of sub-modules may include at least one spare sub-module.

[0077] The VBE controller (2) can calculate an index for determining whether operation is possible when a number of sub-modules greater than the number of spare sub-modules among multiple sub-modules fails.

[0078] Specifically, the VBE controller (2) calculates an index that can compare the operable area and the required operable area when the number of sub-modules judged to be faulty is greater than a preset number, and can maintain continuous operation when the operable area is wider than the required operable area using the calculated index.

[0079] Figure 6 is a flowchart for explaining a control method of MMC STATCOM when a sub-module of the present invention fails.

[0080] Referring to Fig. 6, while the MMC STATCOM is running (S610), the VBE controller (2) can receive status information of a plurality of sub-modules and determine the number of faulty sub-modules (Qty_(SM_F)) among the plurality of sub-modules based on the received status information (S620).

[0081] As previously explained, multiple submodules may include spare submodules.

[0082] The VBE controller (2) can calculate an index for determining whether operation is possible when the number of faulty sub-modules (Qty_(SM_F)) is greater than a preset number (e.g., the number of spare sub-modules) (Qty_(SM_Red)) (S630).

[0083] At this time, the VBE controller (2) can calculate an index for determining whether driving is possible in different ways when driving with inductive output and when driving with capacitive output.

[0084] For example, the VBE controller (2) can calculate a first index (Index_L) for determining whether driving is possible through the following [Mathematical Formula 1] when driving an inductive output (S640).

[0085] [Mathematical Formula 1]

[0086]

[0087] Here, V_(PCC_MAX) is the maximum voltage of the MMC STATCOM connection point (PCC), V_(MMC_MAX) is the maximum output voltage of the MMC STATCOM, and Z_STATCOM is the impedance value of the MMC STACOM.

[0088] As another example, the VBE controller (2) can calculate a second index (Index_C) for determining whether operation is possible through the following [Mathematical Formula 2] when driving a capacitive output (S660).

[0089] [Equation 2]

[0090]

[0091] Here, V_ref is the MMC STATCOM link point reference value, V_(MMC_MAX) is the MMC STATCOM maximum output voltage, and Z_STATCOM is the impedance of the MMC STACOM.

[0092] The VBE controller (2) can stop the MMC STATCOM operation (S680) when the value of the first index (Index_L) to be considered in the inductive output drive is greater than 1 (S650).

[0093] In addition, the VBE controller (2) can stop the MMC STATCOM operation when the value of the second index (Index_C) that must be considered when driving the capacitive output is greater than -1 (S670).

[0094] That is, the first index (Index_L) is an inductive drivability index, and refers to an index that compares the drivable area and the required drivability area in the inductive output. The VBE controller (2) can determine that drivability is impossible if the Index_L value is greater than 1.

[0095] In addition, the second index (Index_C) is a capacitive drivability index, and refers to an index that compares the drivable area and the required drivability area in the capacitive output. The VBE controller (2) can determine that operation is impossible if the Index_C value is greater than -1.

[0096] Figures 7, 8, and 9 are graphs for explaining the control method discussed in Figure 6.

[0097] Figure 7 shows a VI curve graph of STATCOM in normal state.

[0098] Based on the horizontal current axis, the minus area indicates the capacitive output area, and the plus area indicates the inductive output area.

[0099] Fig. 7 is a graph that can confirm the operable area and designed operation area of ​​the MMC STATCOM to which the present invention is applied. The vertical axis is the voltage of the power system to which the STATCOM is connected, and the horizontal axis is the current that the STATCOM can output, and the unit is expressed as [P.U], which is Per Unit. In the graph, the dotted line indicates the boundary of the designed operation area, and the red line (Available Area) indicates the boundary of the operable area.

[0100] In Fig. 7, it can be seen that the boundaries of the design operation area and the operable operation area are the same because it is assumed that there is no sub-module failure of the MMC STATCOM or the number of spare sub-modules is less than or equal to the number of spare sub-modules.

[0101] Figure 8 shows a STATCOM VI curve graph showing a situation in which operation is possible even if the number of spare sub-modules is greater than the number of failures.

[0102] Figure 8 illustrates the operating areas when the submodule failure of the MMC STATCOM exceeds the reserve quantity. Unlike Figure 7, it can be seen that the available area is located below the design area. In the prior art, the MMC STATCOM is stopped in this situation, but the present invention can maintain continuous operation without stopping by taking into account the actual required operating area.

[0103] The required operation area described in the present invention is indicated by a black solid line in Figure 5. This required operation area indicates the operating boundary or area required for the MMC STATCOM to operate based on the set command value, and operation will not occur in the upper area of ​​this boundary unless the command value setting is changed. This required operation area boundary line is a unique graph representing the TATCOM operation characteristics and is named VI Curve.

[0104] As illustrated in Fig. 8, even if more sub-modules than the number of spare sub-modules fail, the VBE controller (2) can maintain continuous operation without stopping operation based on the fact that the available area is wider than the required operation area.

[0105] The required driving area and the possible driving area can refer to the area below in the VI graph.

[0106] Meanwhile, as shown in Fig. 9, this is a graph showing the VI curve of STATCOM in a state where the number of sub-modules is greater than the number of spare sub-modules.

[0107] Figure 8 shows a case where the available area is narrower than the operation area, and the index Index_C becomes greater than -1. Accordingly, the STATCOM is stopped by the proposed algorithm.

[0108] In the case of Fig. 9, since the available area is narrower than the operation area, it is determined that operation is impossible and operation of the MMC STATCOM can be stopped.

[0109] The present invention proposes an drivability index to enable comparison of the driving conditions and the drivable state in the event that the SM, which is the basic module of the MMC STATCOM, is bypassed more than the reserve SM quantity due to an accident. This invented index is used as an index for determining the drivable state in the proposed flowchart of Figure 6, and ultimately, when the index standard is exceeded, the MMC STATCOM can be stopped.

[0110] Due to this, the present invention can achieve the effect of increasing the operating rate and reliability of the equipment compared to the conventional technology.

[0111] According to at least one of the embodiments of the present invention, when a sub-module (SM) of an MMC STATCOM fails beyond the reserve quantity, the present invention can improve the operating rate of the equipment by calculating an index that can compare the operable area and the required operating area and maintaining continuous operation using the index, instead of stopping the equipment as in the prior art.

[0112] The present invention described above can be implemented as computer-readable code on a medium having a program recorded thereon. Computer-readable media include all types of recording devices that store data that can be read by a computer system. Examples of computer-readable media include hard disk drives (HDDs), solid-state disks (SSDs), silicon disk drives (SDDs), ROMs, RAMs, CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, etc., and also include media implemented in the form of carrier waves (e.g., transmission via the Internet). In addition, the computer may include a control unit for a protection relay. Therefore, the above detailed description should not be construed as limiting in all respects, but should be considered as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are intended to be included in the scope of the present invention.

Claims

1. Multiple submodules; A plurality of SMI (Sub-Module Interfaces) corresponding to each of the plurality of sub-modules and receiving status information from the corresponding sub-modules; and Includes a VBE controller that receives status information of submodules from the plurality of SMIs and diagnoses the status of each submodule based on the received status information, The above VBE controller, Based on the received status information, the number of faulty sub-modules among the plurality of sub-modules is determined, An MMC-type STATCOM system characterized in that it calculates an index for determining whether operation is possible when the number of judged sub-modules is greater than a preset number.

2. In paragraph 1, The above plurality of sub-modules include at least one spare sub-module, The above VBE controller, A STATCOM system of MMC type, characterized in that when a number of sub-modules greater than the number of spare sub-modules among the above-mentioned plurality of sub-modules fail, an index for determining whether operation is possible is calculated.

3. In paragraph 1, The above VBE controller, A STATCOM system of MMC type characterized in that when the number of sub-modules judged to be faulty is greater than a preset number, an index for comparing the operable area and the required operable area is calculated, and when the operable area is wider than the required operable area using the calculated index, continuous operation is maintained.

4. In paragraph 1, The above VBE controller, A STATCOM system of the MMC type characterized by calculating an index for determining whether operation is possible in different ways when driving with inductive output and when driving with capacitive output.

5. In paragraph 4, The above VBE controller, An MMC type STATCOM system characterized in that, when driving an inductive output, a first index (Index_L) is calculated to determine whether driving is possible through the following [Mathematical Formula 1]. [Mathematical Formula 1] Here, V_(PCC_MAX) is the maximum voltage of the MMC STATCOM connection point (PCC), V_(MMC_MAX) is the maximum output voltage of the MMC STATCOM, and Z_STATCOM is the impedance of the MMC STACOM.

6. In paragraph 4, The above VBE controller, An MMC type STATCOM system characterized in that, when driving a capacitive output, a second index (Index_C) is calculated to determine whether driving is possible through the following [Mathematical Formula 2]. [Equation 2] Here, V_ref is the MMC STATCOM link point reference value, V_(MMC_MAX) is the MMC STATCOM maximum output voltage, and Z_STATCOM is the impedance of the MMC STACOM.

7. In paragraph 5, The above VBE controller, An MMC type STATCOM system characterized in that when the value of the first index is greater than 1, the MMC STATCOM operation is stopped.

8. In paragraph 6, The above VBE controller, An MMC type STATCOM system characterized in that when the value of the second index is greater than -1, the MMC STATCOM operation is stopped.

Images