A protection system and method for hybrid AC filter

Abstract

The present invention belongs to the technical field of power systems, and specifically relates to a protection system and method for a hybrid AC filter. The method detects the area where a hybrid AC filter fault occurs, and the hybrid AC filter is divided into a busbar area, a passive area, and an active area. When a fault occurs in an area, a corresponding protection action is performed based on the fault type of the fault area. If the corresponding fault still exists in the passive area of ​​the hybrid AC filter after the protection action, the busbar area of ​​the hybrid AC filter is cut off from the passive area. If the corresponding fault still exists in the active area of ​​the hybrid AC filter after the protection action, the passive area of ​​the hybrid AC filter is cut off from the active area. The method determines the corresponding protection action for each area and each fault based on the fault and protection requirements of each area. Then, when a fault occurs in the corresponding area, the corresponding area can perform the corresponding protection action, solving the problem that the prior art does not set corresponding protection measures for the hybrid AC filter.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, and in particular relates to a protection system and method for a hybrid AC filter. Background Art

[0002] As UHVDC projects continue to gain prominence in my country's power transmission system, the harmonic issues they bring are becoming increasingly prominent. Currently, serious harmonic exceeding standards has occurred around some DC project sites. Traditional UHV harmonic mitigation requires the installation of numerous passive filter banks. These filters occupy large footprints, have weak dynamic regulation capabilities, are prone to overvoltage during load shedding, and can resonate with the AC system, making them unsuitable for future power system operations.

[0003] Active filters have large capacity and high cost, and consume a lot of electricity during operation. It is difficult to manufacture high-power and fast-response active filters, which limits the promotion and use of active filters, especially in high-voltage and high-power situations such as substations or large industrial and mining enterprises. Therefore, further improving and enhancing the combination scheme and working performance of hybrid AC filters to meet various compensation requirements has gradually become a hot research topic in the field of harmonic suppression and is also the development direction of future filtering technology. The filtering effect of hybrid AC filter HAPF is as follows: Figure 1 shown.

[0004] Common faults of hybrid AC filters include short circuits, capacitor damage, equipment overload, filter detuning, valve block failure, and valve unit failure. A short circuit primarily refers to a ground short in the equipment or wiring. The three phases of the filter are separated by a considerable distance, making interphase short circuits extremely unlikely. Capacitor damage refers to a breakdown in the internal capacitor components. Equipment overload includes overload of high-end capacitors, reactors, and resistors. Filter detuning occurs when the actual tuned frequency of the filter deviates from the set value of the corresponding harmonic frequency. Valve block failure and valve unit failure refer to malfunctions within the valve itself. When a hybrid AC filter short-circuit occurs, the set filter channel is altered, and the hybrid AC filter cannot achieve the intended filtering effect. More seriously, a short circuit can cause overcurrent in individual components, resulting in damage. Therefore, the hybrid AC filter must be promptly disconnected based on the fault condition.

[0005] The invention patent application, publication number CN 108288857 A (A Dual-Resonance Three-Phase Active Power Filter, Control Method, and Device), proposes a dual-resonance three-phase active power filter topology, addressing the technical issue of active power filters being unsuitable for high-voltage systems. The patent does not mention filter-related protection solutions or systems.

[0006] The invention patent application, publication number CN 110601197 A (High-voltage Passive Filter Protection System and Method), proposes a high-voltage passive filter protection method and system. This method primarily detects harmonic current overcurrent and harmonic voltage overvoltage conditions in the traction network. When a harmonic current overcurrent or harmonic voltage overvoltage occurs, the high-voltage passive filter is switched off, reducing the risk of breakdown or overheating of certain components in the high-voltage passive filter. While the patent mentions filter-related protection schemes and systems, it primarily focuses on passive filters and does not address how to configure protection schemes and systems for hybrid AC filters.

[0007] The invention patent application, with publication number CN 114844011 A (Active filter protection method and system), proposes a high-voltage active filter protection method and system. This invention patent application primarily addresses the H-type connected capacitors of the active filter, proposing a novel differential protection scheme. This scheme compensates the capacitor current value by fixing it in the differential current. When a capacitor fault occurs, the capacitor parameters change, and differential protection generates a differential current. This differential protection can reflect capacitor faults. However, the invention patent application does not address how to configure the protection scheme and system for hybrid AC filters.

[0008] The invention patent application, publication number CN 114825276 A (Converter Protection System and Method for a Through-Phase Traction Power Supply System), proposes a converter protection system and method for a through-phase traction power supply system. Based on the specific structure and fault electrical characteristics of the converters in the through-phase power supply system, converter fault protection is divided into zones, and protection measures are determined based on the fault and protection requirements of each zone. The patent does not mention protection schemes and systems related to hybrid AC filters. Summary of the Invention

[0009] The object of the present invention is to provide a protection system and method for a hybrid AC filter, so as to solve the problem that there is no protection solution for the hybrid AC filter in the prior art.

[0010] To solve the above technical problems, the present invention provides a protection method for a hybrid AC filter, comprising the following steps:

[0011] 1) Detecting the area where the hybrid AC filter fault occurs; the hybrid AC filter is divided into a busbar area, a passive area, and an active area; the passive area is connected to the busbar area through the busbar of the busbar area, and the other end of the passive area is connected to the active area;

[0012] 2) When a busbar fault is detected, the busbar area of ​​the hybrid AC filter performs corresponding protection actions according to the type of busbar fault;

[0013] When a passive zone fault is detected, the passive zone of the hybrid AC filter performs corresponding protection actions according to the type of passive zone fault;

[0014] When an active zone fault is detected, the active zone of the hybrid AC filter performs corresponding protection actions according to the active zone fault type;

[0015] 3) When the passive area of ​​the hybrid AC filter still has the corresponding fault after the protection action, the busbar area of ​​the hybrid AC filter will cut off the passive area;

[0016] When the active area of ​​the hybrid AC filter still has a corresponding fault after the protection action, the active area of ​​the passive area of ​​the hybrid AC filter is cut off.

[0017] The beneficial effects are as follows: the hybrid AC filter is partitioned according to the specific structure and fault electrical characteristics of the hybrid AC filter, and after the partitioning, the corresponding protection actions of each area and each fault are determined according to the faults and protection requirements that may exist in each area, so that when a fault occurs in the corresponding area, the corresponding area can perform the corresponding protection action, which solves the problem that the prior art does not set corresponding protection measures for the hybrid AC filter, and based on the protection actions of the present invention based on the different areas and fault types, the protection actions of the hybrid AC filter are more refined. When the corresponding protection action fails to eliminate the fault in the passive area or the active area of ​​the hybrid AC filter, the fault is removed through the previous area (the previous area corresponding to the passive area of ​​the hybrid AC filter is the hybrid AC filter bus area, and the previous area corresponding to the active area of ​​the hybrid AC filter is the hybrid AC filter passive area), thereby increasing the protection redundancy of the hybrid AC filter.

[0018] Furthermore, in step 3), the method for removing the passive area from the busbar area of ​​the hybrid AC filter is: tripping all AC filter branch group circuit breakers, AC field series circuit breakers and hybrid AC passive area circuit breakers in the busbar area of ​​the hybrid AC filter; the method for removing the passive area from the passive area of ​​the hybrid AC filter is: tripping the hybrid AC active area circuit breaker.

[0019] The present invention achieves the process of blocking the fault by disconnecting the circuit breaker in the passive region (or active region) of the hybrid AC filter after the corresponding protection action in the passive region (or active region) of the hybrid AC filter fails to clear the fault. Furthermore, the present invention can completely clear the fault by directly disconnecting the corresponding circuit breaker, thereby ensuring the safety of the hybrid AC filter.

[0020] Furthermore, in step 2), when the busbar area fault type is a fault occurring inside the busbar area, the corresponding busbar area differential protection action is performed by the busbar area differential protection module; when the busbar area fault type is overvoltage, the corresponding busbar area overvoltage protection action is performed by the busbar area overvoltage protection module.

[0021] Furthermore, in step 2), when the passive zone fault type is a short circuit fault or a capacitor group unbalanced fault, the corresponding passive zone differential protection action or passive zone unbalanced protection action is performed through the passive zone main protection module; when the passive zone fault type is an overcurrent and overload fault, the corresponding passive zone overcurrent and overload protection action is performed through the passive zone backup protection module; when the passive zone fault type is a tuning point offset fault, the corresponding passive zone detuning alarm action is performed through the passive zone backup protection module.

[0022] Furthermore, in step 2), when the active area fault type is a short circuit fault, the corresponding active area differential protection action is performed by the active area main protection module; when the active area fault type is an overload fault, the corresponding active area overload protection action is performed by the active area backup protection module; when the active area fault type is a valve unit or valve group fault, the corresponding active area valve group protection action is performed by the active area valve group protection module.

[0023] By dividing the hybrid AC filter into zones for protection and setting a protection module corresponding to the fault in each zone, refined protection against faults is achieved and the protection reliability of the hybrid AC filter is improved.

[0024] To solve the above technical problems, the present invention further provides a protection system for a hybrid AC filter, comprising a controller, wherein the controller is configured to execute instructions to implement the following process:

[0025] 1) Detecting the area where the hybrid AC filter fault occurs; the hybrid AC filter is divided into a busbar area, a passive area, and an active area; the passive area is connected to the busbar area through the busbar of the busbar area, and the other end of the passive area is connected to the active area;

[0026] 2) When a busbar fault is detected, the busbar area of ​​the hybrid AC filter performs corresponding protection actions according to the type of busbar fault;

[0027] When a passive zone fault is detected, the passive zone of the hybrid AC filter performs corresponding protection actions according to the type of passive zone fault;

[0028] When an active zone fault is detected, the active zone of the hybrid AC filter performs corresponding protection actions according to the active zone fault type;

[0029] 3) When the passive area of ​​the hybrid AC filter still has the corresponding fault after the protection action, the busbar area of ​​the hybrid AC filter will cut off the passive area;

[0030] When the active area of ​​the hybrid AC filter still has a corresponding fault after the protection action, the active area of ​​the passive area of ​​the hybrid AC filter is cut off.

[0031] The beneficial effects are as follows: the hybrid AC filter is partitioned according to the specific structure and fault electrical characteristics of the hybrid AC filter, and after the partitioning, the corresponding protection actions of each area and each fault are determined according to the faults and protection requirements that may exist in each area, so that when a fault occurs in the corresponding area, the corresponding area can perform the corresponding protection action, which solves the problem that the prior art does not set corresponding protection measures for the hybrid AC filter, and based on the protection actions of the present invention based on the different areas and fault types, the protection actions of the hybrid AC filter are more refined. When the corresponding protection action fails to eliminate the fault in the passive area or the active area of ​​the hybrid AC filter, the fault is removed through the previous area (the previous area corresponding to the passive area of ​​the hybrid AC filter is the hybrid AC filter bus area, and the previous area corresponding to the active area of ​​the hybrid AC filter is the hybrid AC filter passive area), thereby increasing the protection redundancy of the hybrid AC filter.

[0032] Furthermore, in step 3), the method for removing the passive area from the busbar area of ​​the hybrid AC filter is: tripping all AC filter branch group circuit breakers, AC field series circuit breakers and hybrid AC passive area circuit breakers in the busbar area of ​​the hybrid AC filter; the method for removing the passive area from the passive area of ​​the hybrid AC filter is: tripping the hybrid AC active area circuit breaker.

[0033] The present invention achieves the process of blocking the fault by disconnecting the circuit breaker in the passive region (or active region) of the hybrid AC filter after the corresponding protection action in the passive region (or active region) of the hybrid AC filter fails to clear the fault. Furthermore, the present invention can completely clear the fault by directly disconnecting the corresponding circuit breaker, thereby ensuring the safety of the hybrid AC filter.

[0034] Furthermore, it also includes a bus area differential protection module and a bus area overvoltage protection module; the bus area differential protection module is used to perform corresponding bus area differential protection actions when the bus area fault type is a fault inside the bus area bus; the bus area overvoltage protection module is used to perform corresponding bus area overvoltage protection actions when the bus area fault type is overvoltage.

[0035] Furthermore, it also includes a passive zone main protection module and a passive zone backup protection module; the passive zone main protection module is used to perform corresponding passive zone differential protection action or passive zone unbalanced protection action when the passive zone fault type is a short circuit fault or a capacitor group unbalanced fault; the passive zone backup protection module is used to perform corresponding passive zone overcurrent and overload protection action when the passive zone fault type is an overcurrent and overload fault; the passive zone backup protection module is also used to perform corresponding passive zone detuning alarm action when the passive zone fault type is a tuning point offset fault.

[0036] Furthermore, it also includes an active area main protection module, an active area backup protection module and an active area valve group protection module; the active area main protection module is used to perform the corresponding active area differential protection action when the active area fault type is a short circuit fault; the active area backup protection module is used to perform the corresponding active area overload protection action when the active area fault type is an overload fault; the active area valve group protection module is used to perform the corresponding active area valve group protection action when the active area fault type is a valve unit or valve group fault.

[0037] By dividing the hybrid AC filter into zones for protection and setting a protection module corresponding to the fault in each zone, refined protection against faults is achieved and the protection reliability of the hybrid AC filter is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the filtering effect of the hybrid AC filter HAPF;

[0039] Figure 2 This is a schematic diagram of the protection area division of the hybrid AC filter of the present invention;

[0040] Figure 3 It is a schematic diagram of the hybrid AC filter protection system module of the present invention;

[0041] Figure 4 is a schematic diagram of a hybrid AC filter protection system of the present invention;

[0042] Figure 5 It is a flow chart of the hybrid AC filter protection method of the present invention. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail with reference to the accompanying drawings and embodiments.

[0044] Example of protection system for hybrid AC filter:

[0045] In this embodiment, the hybrid AC filter fault protection is divided into zones according to the specific structure and fault electrical characteristics of the hybrid AC filter, and the protection process of the hybrid AC filter is realized by respectively determining the protection measures according to the fault and protection requirements of each zone. Figure 2 The figure shows the protection area division of the hybrid AC filter used in this embodiment, that is, the hybrid AC filter is divided into three areas: the hybrid AC filter bus area (hereinafter referred to as the bus area), the hybrid AC filter passive area (hereinafter referred to as the passive area), and the hybrid AC filter active area (hereinafter referred to as the active area). That is, the passive area is connected to the bus area through the bus of the bus area, and the other end of the passive area is connected to the active area. In addition, for common fault types of the hybrid AC filter, a protection module corresponding to the fault type is set in each area, such as Figure 3 As shown, this embodiment includes a hybrid AC filter bus area differential protection module, a hybrid AC filter bus area overvoltage protection module, a hybrid AC filter bus area failure protection module, a hybrid AC filter passive area main protection module, a hybrid AC filter passive area backup protection module, a hybrid AC filter passive area failure protection module, a hybrid AC filter active area main protection module, a hybrid AC filter active area backup protection module, a valve group protection module, and a hybrid AC filter active area failure protection module.

[0046] The connection relationship of the protection modules of this embodiment is as follows: Figure 4 As shown, the hybrid AC filter bus area differential protection module, the hybrid AC filter bus area overvoltage protection module and the hybrid AC filter bus area failure protection module are respectively Figure 4 Differential protection, overvoltage protection and circuit breaker failure protection in the hybrid AC filter busbar area; the main protection module of the hybrid AC filter passive area includes Figure 4 Differential protection in the passive zone of hybrid AC filter, C1 capacitor unbalance protection; hybrid AC filter passive zone backup protection module includes Figure 4 Overcurrent and overload protection, zero-sequence overcurrent protection, L2 reactance overload protection, resistor overload protection, L1 reactance overload protection and detuning alarm in the passive zone of hybrid AC filter; the hybrid AC filter passive zone failure protection module includes Figure 4 Circuit breaker failure protection in the passive area of ​​the hybrid AC filter; the main protection module of the active area of ​​the hybrid AC filter, the backup protection module of the active area of ​​the hybrid AC filter, the valve group protection module and the failure protection module of the active area of ​​the hybrid AC filter are respectively Figure 4 Active filter differential protection, reactor overload protection, valve group protection and circuit breaker failure protection in the active area of ​​hybrid AC filter, and based on Figure 4 The link relationship can be realized when performing fault detection on the hybrid AC filter. Figure 5The protection method of the hybrid AC filter shown in the figure is as follows:

[0047] Busbar area fault types and corresponding protection actions:

[0048] The hybrid AC filter busbar differential protection module is used to protect the hybrid AC filter busbar (i.e., when a busbar fault occurs in the hybrid AC filter busbar area, the hybrid AC filter busbar differential protection is activated). This module includes conventional ratio differential protection and sudden change ratio differential protection. It can detect internal phase-to-phase short-circuit and ground short-circuit faults within the passive AC filter busbar, as well as subtle faults. The module also takes into account CT anomalies and inconsistent CT transient characteristics.

[0049] The hybrid AC filter busbar area overvoltage protection module is mainly used to avoid serious AC continuous overvoltage (that is, after detecting AC continuous overvoltage, the hybrid AC filter busbar area overvoltage protection will be activated). The hybrid AC filter busbar area overvoltage protection module is set according to phase and is sensitive to power frequency voltage and voltage below the eleventh harmonic. The hybrid AC filter busbar area overvoltage protection module will issue alarms in sequence after being activated according to the set values ​​from small to large and the different delays from large to small; it will trip the passive AC filter branch group circuit breaker and the hybrid AC filter passive area circuit breaker, and at the same time, it should also issue a locking instruction to the hybrid AC filter active area; it will trip all passive AC filter branch group circuit breakers, AC field series circuit breakers and hybrid AC filter passive area circuit breakers in the hybrid AC filter busbar area.

[0050] The hybrid AC filter busbar area failure protection module is started by the protection tripping contact of the hybrid AC filter passive area (that is, it is started when the protection tripping contact of the hybrid AC filter passive area is detected), and all the passive AC filter branch group circuit breakers, AC field series circuit breakers and hybrid AC filter passive area circuit breakers in the hybrid AC filter busbar area are tripped, and at the same time a blocking instruction is issued to the hybrid AC filter active area, such as Figure 4 When the hybrid filter busbar area is activated, Q1, Q2, Q3, Q4 and Q5 are tripped (that is, when the protection of the hybrid AC filter busbar area is activated, all passive AC filter branch group circuit breakers, AC field series circuit breakers and hybrid AC filter passive area circuit breakers in the hybrid AC filter busbar area are tripped), and a locking command is issued to the active area of ​​the hybrid AC filter.

[0051] Fault types in the passive zone and corresponding protection actions:

[0052] The hybrid AC filter passive zone main protection module is used to protect the hybrid AC filter's passive zone. It includes ratio differential protection and capacitor unbalance protection. Ratio differential protection and capacitor unbalance protection are two existing independent protection principles. Ratio differential protection can detect phase-to-phase short-circuit faults and ground short-circuit faults within the hybrid AC filter's passive zone. When a serious fault occurs within the filter in the hybrid AC filter's passive zone, it poses a serious threat to the stability of the power system. Differential current-rate trip protection is configured to quickly eliminate serious internal faults within the hybrid AC filter's passive zone (i.e., when a short-circuit fault occurs in the hybrid AC filter's passive zone, the hybrid AC filter's passive zone differential protection activates). The capacitor unbalance protection works by detecting the changing trend of the capacitor bank's unbalanced current to determine whether the capacitance on both sides of the bridge arm has changed, and thus whether a capacitor bank fault has occurred (i.e., when a capacitor bank imbalance occurs in the hybrid AC filter's passive zone, the hybrid AC filter's passive zone unbalance protection activates).

[0053] The hybrid AC filter's passive zone backup protection module is used to protect the hybrid AC filter's passive zone, with a slight delay. This module includes overcurrent protection, zero-sequence overcurrent protection, thermal overload protection, and detuning monitoring. Overcurrent protection primarily prevents overcurrent from damaging the filter in the hybrid AC filter's passive zone. The most important function of zero-sequence overcurrent protection is detecting ground faults on the ground side of the filter in the hybrid AC filter's passive zone. Because the fault current is small, differential protection may not detect it. Zero-sequence overcurrent protection also detects open-circuit faults on each phase (i.e., if an open-circuit fault occurs in a phase in the hybrid AC filter's passive zone, the zero-sequence overcurrent protection in the hybrid AC filter's passive zone activates). High-side capacitors carry the majority of the bus voltage and high harmonic voltages. Increased grid voltage or significant capacitor damage can lead to capacitor overload. Due to the nature of hybrid AC filters, the long-term flow of high harmonic currents through the hybrid AC filter can cause long-term heating and damage to reactors and resistors. In response to these situations, it is necessary to configure targeted protection, namely harmonic definite time thermal overload protection and harmonic inverse time thermal overload protection (that is, when the high-voltage capacitor, reactor or resistor in the passive area of ​​the hybrid AC filter is overloaded, the harmonic definite time thermal overload protection and harmonic inverse time thermal overload protection in the passive area of ​​the hybrid AC filter will be activated). In order to identify small changes in the filter in the passive area of ​​the hybrid AC filter, a detuning monitoring function is set to monitor the tuning point of the filter in the passive area of ​​the hybrid AC filter (that is, when the tuning point of the passive AC filter shifts in the passive area of ​​the hybrid AC filter, the passive area of ​​the hybrid AC filter will issue a detuning alarm).

[0054] Failure protection module of hybrid AC filter passive zone. When the main protection module or backup protection module of hybrid AC filter passive zone operates and issues a tripping command to cut off the circuit breaker of hybrid AC filter passive zone, if the current flowing through the circuit breaker of hybrid AC filter passive zone can still be detected after a certain delay, it is determined that the hybrid AC filter passive zone cannot clear the fault, and the protection tripping contact of hybrid AC filter passive zone is output and sent to the failure protection module of hybrid AC filter bus zone (that is, when the failure of circuit breaker of hybrid AC filter passive zone is detected, the protection tripping contact of hybrid AC filter passive zone is output and sent to the failure protection module of hybrid AC filter bus zone). Figure 4 The action of the passive zone of the hybrid filter is to trip Q3, Q4 or Q5, among which when Q5 is tripped, the active AC filter is locked (that is, when the protection of the passive zone of the hybrid AC filter is actuated, the circuit breaker of the passive zone of the hybrid AC filter is tripped, and a locking instruction is sent to the active zone of the hybrid AC filter at the same time).

[0055] Active zone fault types and corresponding protection actions:

[0056] The hybrid AC filter active zone main protection module is used to protect the active area of ​​the hybrid AC filter. This module is ratio differential protection. Ratio differential protection can detect internal phase-to-phase short-circuit and ground short-circuit faults within the hybrid AC filter's active zone. Ratio differential protection also considers CT anomalies and inconsistent CT transient characteristics (i.e., if a short-circuit fault occurs within the hybrid AC filter's active zone, the hybrid AC filter's active zone differential protection will activate).

[0057] The hybrid AC filter active zone backup protection module is used to protect the active area of ​​the hybrid AC filter with a slight delay. This module includes overcurrent protection, zero-sequence overcurrent protection, thermal overload protection, and detuning monitoring. Overcurrent protection primarily prevents overcurrent from damaging the filter in the active zone of the hybrid AC filter. The most important function of zero-sequence overcurrent protection is to detect ground faults on the ground side of the filter in the active zone of the hybrid AC filter. Because the fault current is small, differential protection may not detect it. Zero-sequence overcurrent protection also detects open-circuit faults on each phase (i.e., if an open-circuit fault occurs in a phase in the active zone of the hybrid AC filter, the zero-sequence overcurrent protection in the active zone of the hybrid AC filter activates). High-side capacitors carry the majority of the bus voltage and high harmonic voltages. Increased grid voltage or significant capacitor damage can lead to capacitor overload. Furthermore, due to the nature of hybrid AC filters, the long-term flow of high harmonic currents through the filter can cause long-term heating and damage to reactors and resistors. In response to these situations, it is necessary to configure targeted protection, namely harmonic time-limited thermal overload protection and harmonic inverse time-limited thermal overload protection (that is, when the high-voltage capacitor, reactor or resistor in the active area of ​​the hybrid AC filter is overloaded, the harmonic time-limited thermal overload protection and harmonic inverse time-limited thermal overload protection in the active area of ​​the hybrid AC filter will be activated). In order to identify small changes in the filter in the active area of ​​the hybrid AC filter, a detuning monitoring function is set to monitor the tuning point of the filter in the active area of ​​the hybrid AC filter (that is, when the tuning point of the passive AC filter in the active area of ​​the hybrid AC filter shifts, the active area of ​​the hybrid AC filter will issue a detuning alarm).

[0058] The valve manifold protection module protects the valve manifold and valve units. Upon detecting an overcurrent fault, overvoltage fault, or undervoltage fault in the active AC filter's valve unit, the module activates valve unit overcurrent protection, overvoltage protection, and undervoltage protection. Overcurrent protection is activated when a line fault is detected in the valve manifold; overvoltage protection is activated when an overvoltage condition is detected in the valve manifold due to an external fault; and redundancy protection is activated when the number of faulty valve units exceeds the permitted operating range. A ground fault in the valve manifold activates differential protection.

[0059] Failure protection module of the active area of ​​the hybrid AC filter. When the main protection module or backup protection module of the active area of ​​the hybrid AC filter is activated and a tripping command is issued to cut off the circuit breaker of the active area of ​​the hybrid AC filter, if the current flowing through the circuit breaker of the active area of ​​the hybrid AC filter can still be detected after a certain delay, it is determined that the circuit breaker of the active area of ​​the hybrid AC filter cannot clear the fault, and the protection tripping contact of the active area of ​​the hybrid AC filter is output and sent to the corresponding failure protection module of the passive area of ​​the hybrid AC filter (that is, when the failure of the circuit breaker of the active area of ​​the hybrid AC filter is detected, the protection tripping contact of the active area of ​​the hybrid AC filter is output and sent to the failure protection module of the passive area of ​​the hybrid AC filter, and the failure protection module of the passive area of ​​the hybrid AC filter trips the circuit breaker of the passive area of ​​the hybrid AC filter). Figure 4 As shown, the action of the active area of ​​the hybrid filter is to close Q7 and trip Q6 (that is, after the failure protection of the active area of ​​the hybrid AC filter is actuated, the circuit breaker of the corresponding passive area of ​​the hybrid AC filter should be tripped, and the fault of the active area of ​​the hybrid AC filter is handled by the protection action of the active area of ​​the hybrid AC filter. The filter in the active area of ​​the hybrid AC filter fails and exits, which should not affect the operation of the filter in the passive area of ​​the hybrid AC filter).

[0060] Based on the system of this embodiment, the hybrid AC filter can be partitioned according to the specific structure of the hybrid AC filter and the electrical characteristics of the fault. After the partitioning, the corresponding protection actions of each area and each fault are determined according to the faults and protection requirements that may exist in each area. Then, when a fault occurs in the corresponding area, the corresponding area can perform the corresponding protection action, which solves the problem that the prior art does not set corresponding protection measures for the hybrid AC filter. And based on the protection action of the present invention based on the region and fault type, the protection action of the hybrid AC filter is more refined. When the corresponding protection action fails to eliminate the fault in the passive area or the active area of ​​the hybrid AC filter, the fault is removed through the previous area (the previous area corresponding to the passive area of ​​the hybrid AC filter is the hybrid AC filter bus area, and the previous area corresponding to the active area of ​​the hybrid AC filter is the hybrid AC filter passive area), thereby increasing the protection redundancy of the hybrid AC filter.

[0061] Example of protection method for hybrid AC filter:

[0062] The protection method of the hybrid AC filter can be implemented by the protection system of the hybrid AC filter. The protection system of the hybrid AC filter and the process of the protection method of the hybrid AC filter have been introduced in detail in the embodiment of the protection system of the hybrid AC filter and will not be repeated here.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be based on the claims. Any equivalent structural changes made using the description and drawings of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A protection method for a hybrid AC filter, characterized in that: The steps include: 1) Detecting the area where the hybrid AC filter fault occurs; the hybrid AC filter is divided into a busbar area, a passive area, and an active area; the passive area is connected to the busbar area through the busbar of the busbar area, and the other end of the passive area is connected to the active area; 2) When a busbar area fault is detected and the fault is an overvoltage, the busbar area overvoltage protection module trips all passive AC filter branch group circuit breakers, AC field string circuit breakers and passive area circuit breakers in the busbar area, and sends a locking instruction to the active area; When a fault is detected in the passive zone and the fault is an overload fault, the passive zone backup protection module performs harmonic definite time thermal overload protection and harmonic inverse time thermal overload protection. When a fault is detected in the passive zone and the fault is a tuning point offset fault, the passive zone backup protection module performs the corresponding passive zone detuning alarm action. When a fault is detected in the active zone and the fault is an overload fault, the active zone backup protection module performs harmonic definite time thermal overload protection and harmonic inverse time thermal overload protection. When a fault is detected in the active zone and the fault is a tuning point offset fault, the active zone backup protection module performs the corresponding active zone detuning alarm action. 3) When the corresponding fault still exists in the passive zone of the hybrid AC filter after the protection action, all AC filter branch group circuit breakers, AC field series circuit breakers and hybrid AC passive zone circuit breakers in the busbar area will be tripped; When the active zone of the hybrid AC filter still has a corresponding fault after the protection action, the hybrid AC active zone circuit breaker will be tripped.

2. The protection method of the hybrid AC filter according to claim 1, characterized in that: When the protection tripping contact of the passive zone is detected to be started, all passive AC filter branch group circuit breakers, AC field series circuit breakers and passive zone circuit breakers in the bus zone are tripped, and a locking instruction is sent to the active zone at the same time.

3. The protection method of the hybrid AC filter according to claim 1, characterized in that: In step 2): when a busbar area fault is detected and the fault is an internal phase-to-phase short circuit fault or a ground short circuit fault, the busbar area differential protection module performs a normal ratio differential protection action and a sudden ratio differential protection action.

4. The protection method of the hybrid AC filter according to claim 1, characterized in that: In step 2), when a fault is detected in the passive zone and the fault is an internal phase-to-phase short circuit fault or a ground short circuit fault, the passive zone main protection module performs ratio differential protection; when a fault is detected in the passive zone and the fault is an unbalanced capacitor group, the passive zone main protection module performs capacitor unbalance protection.

5. The protection method of the hybrid AC filter according to claim 1, characterized in that: In step 2), when a fault is detected in the active area and the fault is an internal phase-to-phase short circuit fault or a ground short circuit fault, the active area main protection module performs a ratio differential protection action; When a fault is detected in the active area and the fault is a valve unit overcurrent fault, a valve unit overvoltage fault, or a valve unit undervoltage fault, the active area valve group protection module executes the corresponding overcurrent protection action, the corresponding overvoltage protection action, and the corresponding undervoltage protection action; when a fault is detected in the active area and the fault is a valve group line fault, the active area valve group protection module executes the valve group overcurrent protection action; when a fault is detected in the active area and the fault is that the valve group is affected by an external fault and an overvoltage occurs, the active area valve group protection module executes the valve group overvoltage protection action; when a fault is detected in the active area and the fault is that the number of faulty valve units exceeds the allowable operating range, the active area valve group protection module executes the valve unit redundancy overlimit protection action; when a fault is detected in the active area and the fault is a valve group grounding fault, the active area valve group protection module executes the valve group differential protection action.

6. A protection system for a hybrid AC filter, characterized in that: The controller includes a controller configured to execute instructions to implement the following process: 1) Detecting the area where the hybrid AC filter fault occurs; the hybrid AC filter is divided into a busbar area, a passive area, and an active area; the passive area is connected to the busbar area through the busbar of the busbar area, and the other end of the passive area is connected to the active area; 2) When a busbar area fault is detected and the fault is an overvoltage, the busbar area overvoltage protection module trips all passive AC filter branch group circuit breakers, AC field string circuit breakers and passive area circuit breakers in the busbar area, and sends a locking instruction to the active area; When a fault is detected in the passive zone and the fault is an overload fault, the passive zone backup protection module performs harmonic definite time thermal overload protection and harmonic inverse time thermal overload protection. When a fault is detected in the passive zone and the fault is a tuning point offset fault, the passive zone backup protection module performs the corresponding passive zone detuning alarm action. When a fault is detected in the active zone and the fault is an overload fault, the active zone backup protection module performs harmonic definite time thermal overload protection and harmonic inverse time thermal overload protection. When a fault is detected in the active zone and the fault is a tuning point offset fault, the active zone backup protection module performs the corresponding active zone detuning alarm action. 3) When the corresponding fault still exists in the passive zone of the hybrid AC filter after the protection action, all AC filter branch group circuit breakers, AC field series circuit breakers and hybrid AC passive zone circuit breakers in the busbar area will be tripped; When the active zone of the hybrid AC filter still has a corresponding fault after the protection action, the hybrid AC active zone circuit breaker will be tripped.

7. The protection system of the hybrid AC filter according to claim 6, characterized in that: When the protection tripping contact of the passive zone is detected to be started, all passive AC filter branch group circuit breakers, AC field series circuit breakers and passive zone circuit breakers in the bus zone are tripped, and a locking instruction is sent to the active zone at the same time.

8. The protection system of the hybrid AC filter according to claim 6, characterized in that: It also includes a busbar area differential protection module; the busbar area differential protection module is used to perform conventional ratio differential protection action and sudden change ratio differential protection action when a fault is detected in the busbar area and the fault is an internal phase-to-phase short circuit fault or a ground short circuit fault.

9. The protection system of the hybrid AC filter according to claim 6, characterized in that: It also includes a passive zone main protection module; the passive zone main protection module is used to perform ratio differential protection when a fault is detected in the passive zone and the fault is an internal phase-to-phase short circuit fault or a ground short circuit fault; when a fault is detected in the passive zone and the fault is an unbalanced capacitor group, capacitor unbalance protection is performed.

10. The protection system of the hybrid AC filter according to claim 6, characterized in that: It also includes an active area main protection module and an active area valve group protection module; the active area main protection module is used to perform ratio differential protection action when it is detected that a fault occurs in the active area and the fault is an internal phase-to-phase short circuit fault or a ground short circuit fault; the active area valve group protection module is used to perform corresponding overcurrent protection action, corresponding overvoltage protection action, and corresponding undervoltage protection action when it is detected that a fault occurs in the active area and the fault is a valve unit overcurrent fault, a valve unit overvoltage fault, or a valve unit undervoltage fault; when it is detected that a fault occurs in the active area and the fault is a valve group line fault, the valve group overcurrent protection action is performed; when it is detected that a fault occurs in the active area and the fault is that the valve group is affected by an external fault and an overvoltage occurs, the valve group overvoltage protection action is performed; when it is detected that a fault occurs in the active area and the fault is that the number of faulty valve units exceeds the operating allowable range, the valve unit redundancy overlimit protection action is performed; when it is detected that a fault occurs in the active area and the fault is that the valve group has a ground fault, the valve group differential protection action is performed.

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