HVDC inverter bridge arm short circuit fault location method considering commutation failure

Abstract

This invention discloses a method for locating short-circuit faults in HVDC inverter arms that takes into account commutation failure. The method includes: considering the response characteristics of the HVDC control and protection system to valve short-circuit faults in the inverter-side system, acquiring the waveform data of the HVDC control and protection system after the fault and the valve conduction status of the inverter-side system after the fault, and analyzing the fault characteristics of valve short-circuit faults at different positions, wherein a certain fault characteristic has a unique correspondence with a valve short-circuit fault at a certain position; and locating the short-circuit fault in the inverter arm based on the acquired real-time fault characteristics. By analyzing the current loops of inverter arm short-circuit faults at different positions corresponding to each conduction stage of the converter in the fault data before the fault characteristics change, and based on the three-phase current change characteristics of the corresponding faulty bridge, the fault location is achieved. The proposed location method is based on actual control and protection waveform data and does not add any new arm current measurement points.

Description

Technical Field

[0001] This invention belongs to the field of power system analysis technology, and in particular relates to a method for locating short-circuit faults in the bridge arm of an HVDC inverter that takes into account commutation failure. Background Technology

[0002] With the commissioning of numerous ultra-high voltage direct current (UHVDC) projects in my country, various faults occur frequently during operation. Currently, after a fault, analysis mainly relies on experienced operators using control and protection waveforms stored in the SCADA system's backend. This analysis process is cumbersome and time-consuming. Therefore, rapid and accurate fault location is crucial for shortening maintenance time and improving accident handling efficiency. Regarding grounding faults within converter stations, some scholars have theoretically analyzed the fault characteristics of different fault locations under different valve conduction states, categorized and summarized these characteristics, extracted the inherent features of faults at different locations, and proposed a grounding fault location scheme for converter stations.

[0003] In addition, some scholars have used artificial intelligence algorithms to identify converter station faults based on a pre-established fault database, employing neural networks, deep learning, and other methods. However, for valve short-circuit faults in HVDC inverter stations, common methods include: 1) dividing the valve area into several regions based on the valve conduction sequence and identifying the fault region based on the differential current magnitude of each region, but this method cannot locate the bridge arm faults of two adjacent 6-pulse converters; 2) proposing a method to locate the faulty 6-pulse converter by dividing the fault time period based on the operation of two types of valve short-circuit protection, but this method does not have the function of locating the faulty bridge arm for valve short-circuit faults; 3) realizing the location of three types of valve short-circuit faults on the rectifier side based on the relationship between the integral of each bridge arm current and the three-phase current on the valve side of the converter transformer within the sampling window after the fault, but the bridge arm current cannot be obtained in actual engineering.

[0004] For HVDC projects that have been put into operation but have not set current measurement points for each bridge arm, method 3) cannot be applied to actual engineering projects at present, and this method will inevitably increase engineering costs. As for existing fault location methods that do not use bridge arm current, such as method 1) and method 2), although they consider the conduction stages of different valves, they fail to consider the influence of HVDC control system fault characteristics and fail to use control and protection actions to locate faulty bridge arms, making it impossible to comprehensively and accurately identify all faults that may lead to valve short circuit protection. Summary of the Invention

[0005] This invention provides a method for locating short-circuit faults in HVDC inverter bridge arms that takes into account commutation failure, in order to solve the technical problem of locating faulty bridge arms in a six-pulse converter without setting current measurement points for each bridge arm.

[0006] This invention provides a method for locating short-circuit faults in the bridge arm of an HVDC inverter that takes into account commutation failure, comprising:

[0007] Based on the response characteristics of the HVDC control and protection system to valve short-circuit faults in the inverter side system, the waveform data of the HVDC control and protection system after the fault and the valve conduction status of the inverter side system after the fault are obtained, and the fault characteristics of valve short-circuit faults in different positions are analyzed. Among them, there is a unique correspondence between a certain fault characteristic and a valve short-circuit fault in a certain position.

[0008] Short-circuit fault location of inverter bridge arm is performed based on the real-time fault characteristics obtained after the fault is acquired.

[0009] Furthermore, the valve short-circuit fault includes both Y-bridge valve short-circuit fault and D-bridge valve short-circuit fault; the response characteristics of the HVDC control and protection system to inverter-side valve short-circuit faults include:

[0010] If a short-circuit fault occurs in the Y-bridge inverter side valve, the HVDC control and protection system outputs the response characteristics of the Y-bridge valve short-circuit protection action;

[0011] If a short-circuit fault occurs in the inverter-side valve of the D-bridge, the HVDC control and protection system outputs the response characteristics of the D-bridge valve short-circuit protection action.

[0012] Furthermore, the acquisition of waveform recording data of the HVDC control and protection system after the fault and the valve conduction status of the inverter-side system after the fault, and the analysis of fault characteristics when valves at different positions experience short-circuit faults, include:

[0013] Based on the response characteristics of the short-circuit protection action of the output Y-bridge valve of the HVDC control and protection system, the waveform recording data of the HVDC control and protection system within 20ms after the fault and the valve conduction status of the inverter side system within 20ms after the fault are obtained. The waveform recording data includes the three-phase current data of the Y-bridge and the Y-bridge trigger pulse signal, and the valve conduction status includes the conduction status of each valve of the Y-bridge.

[0014] Based on the acquired three-phase current data of the Y-bridge, the trigger pulse signal of the Y-bridge, and the conduction status of each valve in the Y-bridge, the fault characteristics of valves at different positions when short-circuit faults are determined.

[0015] Furthermore, the step of obtaining the fault characteristics of valves at different positions during short-circuit faults based on the three-phase current data of the Y-bridge, the trigger pulse signal of the Y-bridge, and the conduction state of each valve in the Y-bridge includes:

[0016] When the first valve of the Y-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the second and third valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 6, and there are three consecutive sampling points that satisfy I. YA >0 and I YB >-1, where I YA I is the A-phase current value of the Y-bridge. YB This represents the B-phase current value of the Y-bridge.

[0017] When the second valve of the Y-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the third and fourth valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 12, and there are three consecutive sampling points that satisfy I. YA >1 and I YC <0, where I YA I is the A-phase current value of the Y-bridge. YC This represents the C-phase current value of the Y-bridge.

[0018] When the third valve of the Y-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the fourth and fifth valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 24, and there are three consecutive sampling points that satisfy I. YA >1 and I Y3 >0, where I YA I is the A-phase current value of the Y-bridge. YB This represents the B-phase current value of the Y-bridge.

[0019] When the fourth valve of the Y-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the fifth and sixth valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 48, and there are three consecutive sampling points that satisfy I. YA <0 and I YC >1, where I YA I is the A-phase current value of the Y-bridge. YC This represents the C-phase current value of the Y-bridge.

[0020] When the fifth valve of the Y-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the first and sixth valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 33, and there are three consecutive sampling points that satisfy I. YA >-1 and I YC >0, where I YA I is the A-phase current value of the Y-bridge. YC This represents the C-phase current value of the Y-bridge.

[0021] When the sixth valve of the Y-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the first and second valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 3, and there are three consecutive sampling points that satisfy I. YB <0 and I YC >1, where I YB I represents the B-phase current value of the Y-bridge. YC This represents the C-phase current value of the Y-bridge.

[0022] Furthermore, the acquisition of waveform recording data of the HVDC control and protection system after the fault and the valve conduction status of the inverter-side system after the fault, and the analysis of fault characteristics when valves at different positions experience short-circuit faults, also includes:

[0023] Based on the response characteristics of the short-circuit protection action of the output D-bridge valve of the HVDC control and protection system, the waveform recording data of the HVDC control and protection system within 20ms after the fault and the valve conduction status of the inverter side system within 20ms after the fault are obtained. The waveform recording data includes the three-phase current data of the D-bridge and the trigger pulse signal of the D-bridge. The valve conduction status includes the conduction status of each valve of the D-bridge.

[0024] Based on the acquired three-phase current data of the D-bridge, the trigger pulse signal of the D-bridge, and the conduction status of each valve in the D-bridge, the fault characteristics of valves at different positions when short-circuit faults are determined.

[0025] Furthermore, the step of obtaining the fault characteristics of valves at different positions during short-circuit faults based on the three-phase current data of the D-bridge, the trigger pulse signal of the D-bridge, and the conduction state of each valve in the D-bridge includes:

[0026] When the first valve of the D-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the second and third valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 6, and there are three consecutive sampling points that satisfy I. DA >0 and I DB <-1, where I DA I is the phase A current value of the D-bridge. DB This represents the B-phase current value of the D-bridge.

[0027] When the second valve of the D-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the third and fourth valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 12, and there are three consecutive sampling points that satisfy I. DA >1 and I DC <0, where I DA I is the phase A current value of the D-bridge. DC This represents the C-phase current value of the D-bridge.

[0028] When the third valve of the D-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the fourth and fifth valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 24, and there are three consecutive sampling points that satisfy I. DA >1 and I DB >0, where I DA I is the phase A current value of the D-bridge. DB This represents the B-phase current value of the D-bridge.

[0029] When the fourth valve of the D-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the fifth and sixth valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 48, and there are three consecutive sampling points that satisfy I. DA <0 and I DC >1, where I DA I is the phase A current value of the D-bridge. DC This represents the C-phase current value of the D-bridge.

[0030] When the fifth valve of the D-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the first and sixth valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 33, and there are three consecutive sampling points that satisfy I. DA >-1 and I DC >0, where I DA I is the phase A current value of the D-bridge. DC This represents the C-phase current value of the D-bridge.

[0031] When the sixth valve of the D-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the first and second valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 3, and there are three consecutive sampling points that satisfy I. DB <0 and I DC >1, where I DB I represents the B-phase current value of the D-bridge. DC This represents the current value of phase C of the D-bridge.

[0032] Furthermore, the valve short-circuit fault also includes a Y-bridge 6-pulsating converter short-circuit fault, a D-bridge 6-pulsating converter short-circuit fault, and a 12-pulsating converter short-circuit fault; the response characteristics of the HVDC control and protection system to inverter-side valve short-circuit faults include:

[0033] If a short-circuit fault occurs in the Y-bridge 6-pulse converter, the HVDC control and protection system outputs the response characteristics of the 6-pulse converter short-circuit fault.

[0034] If a short-circuit fault occurs in the D-bridge 6-pulse converter, the HVDC control and protection system outputs the response characteristics of the 6-pulse converter short-circuit fault.

[0035] If a short-circuit fault occurs in the 12-pulse converter, the HVDC control and protection system outputs the response characteristics of the 12-pulse converter short-circuit fault.

[0036] Furthermore, the acquisition of waveform recording data of the HVDC control and protection system after the fault and the valve conduction status of the inverter-side system after the fault, and the analysis of fault characteristics when valves at different positions experience short-circuit faults, also includes:

[0037] Based on the response characteristics of the 6-pulse converter short-circuit fault and the 12-pulse converter short-circuit fault output of the HVDC control and protection system, the waveform recording data of the HVDC control and protection system within 20ms after the fault and the valve conduction status of the inverter side system within 20ms after the fault are obtained. The waveform recording data includes Y-bridge three-phase current data, D-bridge three-phase current data, Y-bridge short-circuit protection action signal, D-bridge short-circuit protection action signal and commutation failure alarm signal.

[0038] Based on the acquired Y-bridge three-phase current data, D-bridge three-phase current data, Y-bridge short-circuit protection action signal, D-bridge short-circuit protection action signal, and commutation failure alarm signal, the fault characteristics of short-circuit faults in different position valves are determined.

[0039] Further, the step of determining the fault characteristics of short-circuit faults in different position valves based on the acquired Y-bridge three-phase current data, D-bridge three-phase current data, Y-bridge short-circuit protection action signal, D-bridge short-circuit protection action signal, and commutation failure alarm signal includes:

[0040] When the Y-bridge 6-pulsating converter is short-circuited, the fault characteristics corresponding to the short circuit of the Y-bridge 6-pulsating converter are: only a commutation failure alarm signal is present, and I... within 8ms after the fault... YMAX Equal to 0, and I DMAX Not equal to 0, where I YMAX I is the maximum value among the Y-bridge phase A current value, Y-bridge phase B current value, and Y-bridge phase C current value. DMAX It is the maximum value among the current values ​​of phase A, phase B, and phase C of bridge D;

[0041] When the D-bridge 6-pulsating converter is short-circuited, the fault characteristics corresponding to the short circuit of the D-bridge 6-pulsating converter are: only a commutation failure alarm signal is present, and within 8ms after the fault, I... DMAX Equal to 0, and I YMAX Not equal to 0;

[0042] When the 12-pulse converter is short-circuited, the fault characteristics corresponding to the short circuit of the D-bridge 6-pulse converter are: only a commutation failure alarm signal is present, and within 8ms after the fault, I... YMAX Equal to 0, and I DMAX It equals 0.

[0043] The proposed method for locating short-circuit faults in HVDC inverter arms that takes into account commutation failure analyzes the current loops of inverter arm short-circuit faults at different locations during each conduction stage of the converter in the fault data before the fault characteristics change. The method then locates the fault based on the three-phase current change characteristics of the corresponding faulty bridge. The proposed method is based on actual control and protection waveform recording data, does not add any new arm current measurement points, is applicable to engineering practice, can be directly applied in the field, and can identify the location of all inverter arm short-circuit faults. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1(a) is a first short-circuit fault circuit diagram of the first valve of the Y-bridge of the inverter at different times after the short circuit of the first valve and the different valve conduction states of the inverter according to a specific embodiment of the present invention.

[0046] Figure 1(b) is a second short-circuit fault circuit diagram of the inverter of a specific embodiment of the present invention, showing the conduction state of different valves after the first valve of the Y-bridge is short-circuited at different times.

[0047] Figure 1(c) is a third short-circuit fault circuit diagram of the inverter Y-bridge at different times after the first valve of the Y-bridge is short-circuited and the different valve conduction states of the inverter according to a specific embodiment of the present invention.

[0048] Figure 1(d) is a fourth short-circuit fault circuit diagram of the inverter of a specific embodiment of the present invention, showing the conduction state of different valves after the first valve of the Y-bridge is short-circuited at different times.

[0049] Figure 1(e) is a fifth short-circuit fault circuit diagram of the inverter in a specific embodiment of the present invention, showing the conduction state of different valves after the first valve of the Y-bridge is short-circuited at different times.

[0050] Figure 2 A waveform diagram of the first valve of the Y-bridge with commutation failure in a specific embodiment of the present invention is provided.

[0051] Figure 3A waveform diagram of a Y-bridge with a short-circuit fault in the first valve of the Y-bridge and no commutation failure, provided as an embodiment of the present invention.

[0052] Figure 4 A structural block diagram of a short-circuit fault location system for an HVDC inverter bridge arm considering commutation failure, provided as a specific embodiment of the present invention.

[0053] Figure 5 The flowchart illustrates a method for locating short-circuit faults in the bridge arm of an HVDC inverter, taking into account commutation failure, as provided in an embodiment of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] In one embodiment of the present invention, for the short-circuit protection of the inverter-side valve, it is configured according to a 6-pulse converter, so the faulty bridge can be located based on the operation of the Y / D bridge protection. Since the short-circuit fault characteristics of the Y / D bridge valves are basically the same, the Y bridge is mainly used as an example here.

[0056] For the short-circuit protection of the Y-bridge valve, the action criterion is as follows:

[0057] I YMAX -max(I DH I DN )>I set1 ,

[0058] I YMAX =max(abs(I YA I YB I YC )),

[0059] I set1 =I1+k1×max(I DH I DN ),

[0060] In the formula, I YA I YB I YC These represent the current values ​​of phase A, phase B, and phase C of the Y-bridge, respectively. YMAX I is the maximum value among the Y-bridge phase A current value, Y-bridge phase B current value, and Y-bridge phase C current value. DH I DNThese are the high-voltage DC bus current and the neutral bus DC current, respectively. set1 The protection action setting value is I1, which is the protection start setting value, generally taken as 0.5 times the rated current, and k1 is the proportional coefficient, taken as 0.2. The protection action delay is 500μs.

[0061] For inverter-side converter arm short-circuit faults, the converter has six conduction stages V Y1 The current loop diagram after the fault is shown in Figure 1(a)-(e), where V Y1 For the first valve of the Y-bridge, V Y2 For the second valve of the Y-bridge, V Y3 The third valve of the Y-bridge, V Y4 The fourth valve of the Y-bridge, V Y5 For the 5th valve of the Y-bridge, V Y6 This is the 6th valve of the Y-bridge.

[0062] 1) Analyze the converter at V based on Figure 1(a) Y3 V Y2 During the conduction phase, V Y1 Fault characteristics after a short circuit. Based on the three-phase voltage situation at this stage, it can be seen that U exists at this time. ba >0, U ba The phase-to-phase voltage between phase B and phase A is given. Therefore, in circuit 2, phase B of the Y-bridge converter transformer passes through the bridge arm under normal conduction (V). Y3 ) and faulty arm (V Y1 A phase-to-phase short circuit occurs between phase A of the converter transformer, causing the Y-bridge current I... YA I YB I YMAX Increase; Loop 1 consists of the sending-end system, DC line, and Y-bridge conducting arm (V Y1 V Y3 The circuit consists of a Y-bridge converter transformer, a D-bridge conducting arm, a D-bridge converter transformer, and a grounding electrode. Due to the phase-to-phase short circuit between phase B and phase A formed by circuit 2, the Y-bridge voltage U... dIY The current I in loop 1 decreases. DH I DN I DMAX Increase, where I DMAX This represents the maximum value among the current values ​​of phase A, phase B, and phase C of bridge D; since circuit 2 is equivalent to a phase-to-phase short circuit in the inverter-side AC system, its short-circuit current is significantly higher than that in circuit 1, therefore, I exists. YMAX >I DH Based on the protection type configured in the inverter-side converter, this fault characteristic only meets the criteria for the operation of the inverter-side valve short-circuit protection.

[0063] 2) When V Y4 After triggering, the converter is in V...Y3 V Y4 During the conduction phase, V Y4 With V Y1 The short-circuited branch forms a bypass pair, and its current loop is shown in Figure 1(b). The current in loop 1 is quickly shunted by loop 2 and drops to 0, i.e., the three-phase current I of the Y-bridge is reduced. YA I YB I YC I YMAX The value is 0; loop 2 is equivalent to short-circuiting the inverter-side Y-bridge, reducing the inverter-side voltage, and correspondingly increasing the loop current I. DH I DN I DMAX Increase. When the converter triggers V Y5 Then, its current loop is shown in Figure 1(c). Due to the presence of the bypass pair, V Y5 No current flows, so it cannot conduct normally, and the fault characteristics remain unchanged. Clearly, if the fault occurs at V... Y4 During the conduction phase, including V Y3 V Y4 and V Y5 V Y4 During the conduction phase, due to V Y4 With V Y4 A bypass pair is immediately formed, and its fault characteristics are all manifested as I. YMAX Reduce to 0, I DH I DN I DMAX As the fault increases, the fault characteristics at this stage are not affected by the timing of the fault.

[0064] 3) For converter V Y5 V Y6 During the conduction phase, the fault characteristics may vary depending on the impact of commutation failure. Specifically:

[0065] ①If in V Y6 and V Y4 V occurs after commutation. Y1 The short circuit and the current loop after the fault are shown in Figure 1(d). Due to the unidirectional conductivity of the thyristor, V0 Y5 Because of V Y1 Short circuit withstands reverse voltage and turns off; the converter's on-state is the same as when it is in normal V. Y6 V Y5 Change to V Y6 V Y1 When the circuit is turned on, the Y-bridge voltage changes from U... ba Reduced to u ba The current I in circuit 2 DH I DN I DMAX I YA I YB and IYMAX Increase.

[0066] After that, when V Y1 After triggering, the inverter side voltage gradually recovers to the rated voltage, and the circuit current also drops to the rated current.

[0067] Subsequently, when V Y2 After triggering, the converter is in V state. Y1 V Y2 During the conduction phase, V Y1 Short circuit without fault characteristics.

[0068] To V Y3 After triggering, the short-circuit bridge arm (V) Y1 ) and V Y3 A phase-to-phase short circuit is formed, and the fault characteristics are as follows: V Y3 V Y2 Analysis during the conduction phase.

[0069] Fault waveforms at each stage, including commutation failure, are as follows: Figure 2 As shown.

[0070] ②If V is triggered at the converter Y6 V occurred before Y1 A short circuit occurs because the control system needs a certain amount of time to respond to a fault. Therefore, when V... Y1 A short circuit triggers V near the converter. Y6 In the event of a time malfunction, the control system may not have enough time to function, resulting in V... Y4 With V Y6 A commutation failure occurs, and the current loop after the fault is shown in Figure 1(e). After the commutation failure process ends, the fault characteristics are still manifested as V. Y4 and V Y1 The corresponding fault characteristics are formed by the bypass pair.

[0071] After that, when V Y1 After triggering, due to commutation failure, the converter's conduction state changes from the normal V... Y1 V Y6 Change to V Y1 V Y4 The circuit is still open, but the fault characteristics are still manifested as V. Y4 and V Y1 The corresponding fault characteristics are formed by the bypass pair.

[0072] Subsequently, when V Y2 After triggering, due to V Y4 Turn on, making V Y2 The anode voltage becomes u a V Y2 Unable to be activated normally, the fault characteristics still manifest as V. Y4 and V Y1The corresponding fault characteristics are formed by the bypass pair.

[0073] Until V Y3 After triggering, V Y1 and V Y3 A phase-to-phase short circuit is formed, and the fault characteristics are as follows: V Y3 V Y2 Analysis during the conduction phase.

[0074] Fault waveforms at each stage where commutation failure did not occur are as follows: Figure 3 As shown.

[0075] Based on the above analysis, it can be seen that because the LCC_HVDC converter uses thyristor devices, it is prone to commutation failure after a short-circuit fault in the inverter-side valve. This results in variations in the fault characteristics of the converter at different conduction stages. However, for different V values ​​at different times... Y1 In terms of faults, it occurs when the converter is in V... Y2 and V Y3 At this time, the short-circuit current supplied by the inverter-side AC system is relatively stable, and the valve short-circuit protection will only activate during this stage; therefore, this stage can be considered as V. Y1 The characteristic time period of the fault.

[0076] Similarly, for the remaining bridge arms V Y2 ~V Y6 Analysis was conducted, and the characteristic time periods and fault characteristics corresponding to short circuits in different bridge arms are listed in Table 1. As can be seen from Table 1, the characteristic time periods and fault characteristics corresponding to short circuits in different bridge arms are different. Therefore, based on this, a criterion can be designed to locate short circuit faults in different bridge arms of the inverter-side converter.

[0077] Table 1. Characteristic time periods and fault characteristics of different bridge arm faults

[0078]

[0079] For short circuits on the output lines of 6-pulse and 12-pulse converters, the fault characteristic is that the inverter-side Y / D bridge current remains zero for an extended period. In this case, the control system's operation only affects the DC current amplitude and has no impact on the Y / D bridge fault characteristics. Therefore, I YMAX =0 and I DMAX When I = 0, it indicates a short circuit in the 12-pulse converter. YMAX When I = 0, it is a pulsating short circuit of Y-bridge 6, I DMAX When = 0, it indicates a pulsed short circuit in bridge D6.

[0080] The fault location method is implemented through an HVDC inverter bridge arm short-circuit fault location system, which is as follows: Figure 4As shown, the system comprises four parts: a valve short-circuit protection action type judgment module, a signal acquisition module, a signal processing module, and a result output module. The inverter station valve short-circuit protection action type judgment module and the signal acquisition module serve as inputs to the signal processing module. The signal processing module outputs the results obtained from the input information to the result output module. The valve short-circuit protection action type judgment module receives inverter station converter valve short-circuit protection action information output by the HVDC control and protection system, including two types: Y-bridge valve short-circuit protection action and D-bridge valve short-circuit protection action. The signal acquisition module acquires the three-phase current measured by the three-phase current transformers on the valve side of the inverter station's Y-bridge converter or D-bridge converter, as well as the trigger pulses CPRY or CPRD of each bridge arm of the Y-bridge converter issued by the control system. The signal processing module determines the fault location based on the protection action status and subsequently acquired analog and digital signals. The result output module displays the fault location based on the processing results of the signal processing module.

[0081] Specifically, this invention is based on a hybrid analog-digital simulation of an HVDC control and protection system whose RTDS parameters are completely consistent with actual engineering parameters. Please refer to [link / reference]. Figure 5 The diagram shows a flowchart of a method for locating short-circuit faults in the arm of an HVDC inverter that takes into account commutation failure, according to this application.

[0082] like Figure 5 As shown, the method for locating short-circuit faults in HVDC inverter bridge arms considering commutation failure specifically includes: Step S101, based on the response characteristics of the HVDC control and protection system to valve short-circuit faults in the inverter-side system, acquiring the waveform recording data of the HVDC control and protection system after the fault and the valve conduction status of the inverter-side system after the fault, and analyzing the fault characteristics of valve short-circuit faults at different positions, wherein a certain fault characteristic has a unique correspondence with a valve short-circuit fault at a certain position; Step S102, locating short-circuit faults in the inverter bridge arms based on the acquired real-time fault characteristics after the fault.

[0083] The specific implementation process is as follows:

[0084] A1. The valve short-circuit protection action type judgment module receives valve short-circuit protection action information output by the HVDC control and protection system. If the protection action information indicates that it is a Y-bridge valve short-circuit protection action, it proceeds to step B1. If the action information indicates that it is a D-bridge valve short-circuit protection action, it proceeds to step B2. If it indicates that there is no valve short-circuit protection action, it returns to continue judgment. If there is only a commutation failure alarm, it acquires the system electrical quantities and proceeds to step A2.

[0085] A2. Take data 8ms after the fault starts and determine if I always exists. YMAX =0, I DMAX=0; if it exists, it is determined that there is a short circuit in the output line of the 12-pulse converter; if it does not exist, it is determined whether I always exists. YMAX =0 or I DMAX =0; if it exists, it is determined that the corresponding 6-pulse (Y / D bridge) output line is short-circuited.

[0086] B1. The signal acquisition module obtains the current measured by the three-phase current transformer of the Y-bridge, controls the converter Y-bridge trigger pulse CPRY issued by the control system, and enters step C1.

[0087] B2. The signal acquisition module obtains the current measured by the three-phase current transformer of the D-bridge, controls the converter D-bridge trigger pulse CPRD issued by the control system, and enters step C1.

[0088] C1. If the short-circuit protection of the Y-bridge valve is activated, the three-phase current of the Y-bridge and the Y-bridge trigger pulse CPRY within 20ms after the fault starts are taken, and then proceed to step D1; if the short-circuit protection of the D-bridge valve is activated, the three-phase current of the D-bridge and the D-bridge trigger pulse CPRD within 20ms after the fault starts are taken, and then proceed to step D2.

[0089] D1. Based on the Y-bridge data input in step C1, determine the converter bridge arm conduction status according to CPRY, and then determine the normalized I... YA I YB I YC Determine the fault characteristics: Both the second and third valves of the Y-bridge are conducting; the value of the Y-bridge trigger pulse signal is 6; and there are three consecutive sampling points that satisfy I. YA >0 and I YB If the value is greater than -1, it is determined that the first valve of the Y-bridge is short-circuited; if the third and fourth valves of the Y-bridge are both conducting, the value of the Y-bridge trigger pulse signal is 12, and there are three consecutive sampling points that satisfy I YA >1 and I YC If the value is less than 0, it is determined that the second valve of the Y-bridge is short-circuited; if the fourth and fifth valves of the Y-bridge are both conducting, the value of the Y-bridge trigger pulse signal is 24, and there are three consecutive sampling points that satisfy I YA >1 and I YB If the value is greater than 0, it is determined that the third valve of the Y-bridge is short-circuited; if the fifth and sixth valves of the Y-bridge are both conducting, the value of the Y-bridge trigger pulse signal is 48, and there are three consecutive sampling points that satisfy I YA <0 and I YC If the value is greater than 1, it is determined that the fourth valve of the Y-bridge is short-circuited; if the first and sixth valves of the Y-bridge are both conducting, the value of the Y-bridge trigger pulse signal is 33, and there are three consecutive sampling points that satisfy I YA >-1 and I YC >0, where I YAI is the A-phase current value of the Y-bridge. YC If the current value of phase C of the Y-bridge is given, then the fault is determined to be a short circuit in the fifth valve of the Y-bridge; if both the first and second valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 3, and there are three consecutive sampling points that satisfy I. YB <0 and I YC If the value is greater than 1, then the fault is determined to be a short circuit in the 6th valve of the Y-bridge.

[0090] D2. Based on the D-bridge data input in step C1, determine the converter bridge arm conduction status according to CPRD, and then determine the normalized I... DA I DB I DC Determine the fault characteristics; if both the second and third valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 6, and there are three consecutive sampling points that satisfy I. DA >0 and I DB If the value is less than -1, it is determined that the first valve of the D-bridge is short-circuited; if the third and fourth valves of the D-bridge are both conducting, the value of the trigger pulse signal of the D-bridge is 12, and there are three consecutive sampling points that satisfy I DA >1 and I DC If the value is less than 0, it is determined that the second valve of the D-bridge is short-circuited; if the fourth and fifth valves of the D-bridge are both conducting, the value of the trigger pulse signal of the D-bridge is 24, and there are three consecutive sampling points that satisfy I DA >1 and I DB If the value is greater than 0, it is determined that the third valve of the D-bridge is short-circuited; if the fifth and sixth valves of the D-bridge are both conducting, the value of the trigger pulse signal of the D-bridge is 48, and there are three consecutive sampling points that satisfy I DA <0 and I DC If the value is greater than 1, it is determined that the fourth valve of the D-bridge is short-circuited; if the first and sixth valves of the D-bridge are both conducting, the value of the trigger pulse signal of the D-bridge is 33, and there are three consecutive sampling points that satisfy I DA >-1 and I DC If the value is greater than 0, it is determined that the 5th valve of the D-bridge is short-circuited; if the 1st and 2nd valves of the D-bridge are both conducting, the value of the D-bridge trigger pulse signal is 3, and there are three consecutive sampling points that satisfy I DB <0 and I DC If the value is greater than 1, it is determined that the 6th valve of bridge D is short-circuited.

[0091] In summary, the method of this application, combined with the actual protection action logic and waveform data of the control and protection system, identifies the valve conduction state through CPRY / D and Y / D bridge currents, considers the fault characteristics of different positions during different valve conduction stages, and realizes fault location based on the corresponding fault characteristics.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for locating short-circuit faults in the bridge arm of an HVDC inverter that takes into account commutation failure, characterized in that, include: Based on the response characteristics of the HVDC control and protection system to valve short-circuit faults in the inverter-side system, the waveform recording data of the HVDC control and protection system after the fault and the valve conduction status of the inverter-side system after the fault are obtained, and the fault characteristics of valve short-circuit faults at different positions are analyzed. A unique correspondence exists between a certain fault characteristic and a valve short-circuit fault at a certain position. The valve short-circuit faults include Y-bridge valve short-circuit faults and D-bridge valve short-circuit faults. The response characteristics of the HVDC control and protection system to valve short-circuit faults in the inverter-side system include: If a short-circuit fault occurs in the Y-bridge inverter side valve, the HVDC control and protection system outputs the response characteristics of the Y-bridge valve short-circuit protection action; If a short-circuit fault occurs in the inverter-side valve of the D-bridge, the HVDC control and protection system outputs the response characteristics of the D-bridge valve short-circuit protection action. Based on the response characteristics of the short-circuit protection action of the output Y-bridge valve of the HVDC control and protection system, the waveform recording data of the HVDC control and protection system within 20ms after the fault and the valve conduction status of the inverter side system within 20ms after the fault are obtained. The waveform recording data includes the three-phase current data of the Y-bridge and the Y-bridge trigger pulse signal, and the valve conduction status includes the conduction status of each valve of the Y-bridge. Based on the acquired three-phase current data of the Y-bridge, the trigger pulse signal of the Y-bridge, and the conduction status of each valve in the Y-bridge, the fault characteristics of valves at different positions when short-circuit faults are determined. Based on the response characteristics of the short-circuit protection action of the output D-bridge valve of the HVDC control and protection system, the waveform recording data of the HVDC control and protection system within 20ms after the fault and the valve conduction status of the inverter side system within 20ms after the fault are obtained. The waveform recording data includes the three-phase current data of the D-bridge and the trigger pulse signal of the D-bridge. The valve conduction status includes the conduction status of each valve of the D-bridge. Based on the acquired three-phase current data of the D-bridge, the trigger pulse signal of the D-bridge, and the conduction status of each valve in the D-bridge, the fault characteristics of valves at different positions when short-circuit faults are determined. Short-circuit fault location of inverter bridge arm is performed based on the real-time fault characteristics obtained after the fault is acquired.

2. The method for locating short-circuit faults in an HVDC inverter bridge arm considering commutation failure, as described in claim 1, is characterized in that... The method of determining the fault characteristics of valves at different positions during short-circuit faults based on the acquired three-phase current data of the Y-bridge, the Y-bridge trigger pulse signal, and the conduction status of each valve in the Y-bridge includes: When the first valve of the Y-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the second and third valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 6, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the Y-bridge. This represents the B-phase current value of the Y-bridge. When the second valve of the Y-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the third and fourth valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 12, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the Y-bridge. This represents the C-phase current value of the Y-bridge. When the third valve of the Y-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the fourth and fifth valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 24, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the Y-bridge. This represents the B-phase current value of the Y-bridge. When the fourth valve of the Y-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the fifth and sixth valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 48, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the Y-bridge. This represents the C-phase current value of the Y-bridge. When the fifth valve of the Y-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the first and sixth valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 33, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the Y-bridge. This represents the C-phase current value of the Y-bridge. When the sixth valve of the Y-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the first and second valves of the Y-bridge are conducting, the value of the Y-bridge trigger pulse signal is 3, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the B-phase current value of the Y-bridge. This represents the C-phase current value of the Y-bridge.

3. The method for locating short-circuit faults in an HVDC inverter bridge arm considering commutation failure, as described in claim 1, is characterized in that... The method of determining the fault characteristics of valves at different positions during short-circuit faults based on the acquired three-phase current data of the D-bridge, the trigger pulse signal of the D-bridge, and the conduction status of each valve in the D-bridge includes: When the first valve of the D-bridge experiences a short circuit fault, the fault characteristics corresponding to this fault are: both the second and third valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 6, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the D-bridge. This represents the B-phase current value of the D-bridge. When the second valve of the D-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the third and fourth valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 12, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the D-bridge. This represents the C-phase current value of the D-bridge. When the third valve of the D-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the fourth and fifth valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 24, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the D-bridge. This represents the B-phase current value of the D-bridge. When the fourth valve of the D-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the fifth and sixth valves of the D-bridge are conducting, the value of the D-bridge trigger pulse signal is 48, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the D-bridge. This represents the C-phase current value of the D-bridge. When the fifth valve of the D-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the first and sixth valves of the D-bridge are conducting, the trigger pulse signal value of the D-bridge is 33, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the A-phase current value of the D-bridge. This represents the C-phase current value of the D-bridge. When the sixth valve of the D-bridge experiences a short circuit, the fault characteristics corresponding to this fault are: both the first and second valves of the D-bridge are conducting, the trigger pulse signal value of the D-bridge is 3, and there are three consecutive sampling points that satisfy the following conditions. and ,in, This represents the B-phase current value of the D-bridge. This represents the current value of phase C of the D-bridge.

4. The method for locating short-circuit faults in an HVDC inverter bridge arm considering commutation failure, as described in claim 1, is characterized in that... The valve short-circuit faults also include short-circuit faults in the Y-bridge 6-pulsating converter, the D-bridge 6-pulsating converter, and the 12-pulsating converter; the response characteristics of the HVDC control and protection system to valve short-circuit faults in the inverter-side system include: If a short-circuit fault occurs in the Y-bridge 6-pulse converter, the HVDC control and protection system outputs the response characteristics of the 6-pulse converter short-circuit fault. If a short-circuit fault occurs in the D-bridge 6-pulse converter, the HVDC control and protection system outputs the response characteristics of the 6-pulse converter short-circuit fault. If a short-circuit fault occurs in the 12-pulse converter, the HVDC control and protection system outputs the response characteristics of the 12-pulse converter short-circuit fault.

5. A method for locating short-circuit faults in an HVDC inverter bridge arm considering commutation failure, as described in claim 4, is characterized in that... The acquisition of waveform recording data of the HVDC control and protection system after a fault and the valve conduction status of the inverter-side system after a fault, and the analysis of fault characteristics when valves at different positions experience short-circuit faults, also includes: Based on the response characteristics of the 6-pulse converter short-circuit fault and the 12-pulse converter short-circuit fault output of the HVDC control and protection system, the waveform recording data of the HVDC control and protection system within 20ms after the fault and the valve conduction status of the inverter side system within 20ms after the fault are obtained. The waveform recording data includes Y-bridge three-phase current data, D-bridge three-phase current data, Y-bridge short-circuit protection action signal, D-bridge short-circuit protection action signal and commutation failure alarm signal. Based on the acquired Y-bridge three-phase current data, D-bridge three-phase current data, Y-bridge short-circuit protection action signal, D-bridge short-circuit protection action signal, and commutation failure alarm signal, the fault characteristics of short-circuit faults in different position valves are determined.

6. The method for locating short-circuit faults in an HVDC inverter bridge arm considering commutation failure, as described in claim 5, is characterized in that... The method involves determining the fault characteristics of short-circuit faults in different position valves based on the acquired Y-bridge three-phase current data, D-bridge three-phase current data, Y-bridge short-circuit protection action signals, D-bridge short-circuit protection action signals, and commutation failure alarm signals, including: When the Y-bridge 6-pulsating converter is short-circuited, the fault characteristics corresponding to the short circuit are: only a commutation failure alarm signal is detected, and within 8ms after the fault occurs... It equals 0, and Not equal to 0, where, This represents the maximum value among the Y-bridge phase A current, Y-bridge phase B current, and Y-bridge phase C current. The maximum value among the current values ​​of phase A, phase B, and phase C of bridge D; When the D-bridge 6-pulsating converter is short-circuited, the fault characteristics corresponding to the short circuit of the D-bridge 6-pulsating converter are: only a commutation failure alarm signal is displayed, and within 8ms after the fault occurs... It equals 0, and Not equal to 0; When the 12-pulse converter is short-circuited, the fault characteristics corresponding to the short circuit of the D-bridge 6-pulse converter are: only a commutation failure alarm signal is detected, and within 8ms after the fault occurs... It equals 0, and It equals 0.

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