US-12618904-B2 - Valve-level fault location method and system for conveters based on horizontal and vertical state differences of valves

US12618904B2US 12618904 B2US12618904 B2US 12618904B2US-12618904-B2

Abstract

A valve-level fault location method and system for converters based on horizontal and vertical state differences of valves are disclosed. The method includes: collecting current data of a converter; calculating a time width of each valve conduction state, an alternating current conduction width, and a direct current conduction width based on the current data; constructing horizontal and vertical timing features on a circuit structure of the converter according to the alternating current conduction width and the direct current conduction width; comparing the time width of each valve conduction state with a time width of a normal valve conduction state, and outputting each valve state signal; and implementing valve-level fault location for the converter according to the time width of each valve conduction state, the alternating current conduction width, the direct current conduction width, the horizontal and vertical timing features, each valve state signal, and the current data. By constructing a difference between horizontal and vertical conduction widths of an alternating current and a direct current based on current timing features, valve-level faults of converters can be accurately located.

Inventors

Xiaohua Li
Shanshan Yin
Hao Li
Yuchen He
Yixin ZHENG

Assignees

SOUTH CHINA UNIVERSITY OF TECHNOLOGY

Dates

Publication Date: 20260505
Application Date: 20221008
Priority Date: 20220413

Claims (8)

1 . A valve-level fault location method for a converter based on horizontal and vertical state differences of valves, performed by a fault location system, the method being used for monitoring the converter of a high-voltage direct current transmission system, the method comprising: measuring three-phase alternating currents of a high-voltage bridge of the converter via a high-voltage bridge alternating-current three-phase current transformer, and measuring three-phase alternating currents of a low-voltage bridge of the converter via a low-voltage bridge alternating-current three-phase current transformer; the high-voltage bridge and the low-voltage bridge each comprising a plurality of valves; measuring a direct-current high-voltage current and a direct-current neutral current of the converter via a direct-current high-voltage direct current transformer and a direct-current neutral direct current transformer respectively; executing the following steps by a processor: collecting current data of the converter, the current data comprising three-phase alternating currents of a j bridge, the direct-current high-voltage current, and the direct-current neutral current, wherein the j bridge is the high-voltage bridge or the low-voltage bridge and j=Y/D, Y representing a high voltage, and D representing a low voltage; calculating a time width of each valve conduction state based on the current data; constructing an alternating current conduction width according to the time width of each valve conduction state, the alternating current conduction width comprising an alternating current outflow conduction width and an alternating current inflow conduction width; constructing a direct current conduction width according to a direct-current high-voltage current amplitude and a direct-current neutral current amplitude, the direct current conduction width comprising a direct current inflow conduction width and a direct current outflow conduction width; constructing horizontal and vertical timing features on a circuit structure of the converter according to the alternating current conduction width and the direct current conduction width; comparing the time width of each valve conduction state with a time width of a normal valve conduction state, and outputting each valve state signal; and locating at least one of a faulty valve, a faulty phase, an external fault, or a line fault for the converter according to the time width of each valve conduction state, the alternating current conduction width, the direct current conduction width, the horizontal and vertical timing features, each valve state signal, and the current data; the alternating current conduction width being constructed according to the time width of each valve conduction state based on the following formulas: { t Y _ ⁢ bottom = Y YHV ⁢ 1 + Y YHV ⁢ 3 + Y YHV ⁢ 5 t Y ⁢ _ ⁢ top = Y YHV ⁢ 2 + Y YHV ⁢ 4 + Y YHV ⁢ 6 ; { t D _ ⁢ bottom = Y DHV ⁢ 1 + Y DHV ⁢ 3 + Y DHV ⁢ 5 t D ⁢ _ ⁢ top = Y YHV ⁢ 2 + Y YHV ⁢ 4 + Y YHV ⁢ 6 wherein t Y_bottom represents a high-voltage bridge alternating current inflow conduction width, t Y_top represents a high-voltage bridge alternating current outflow conduction width, t D_bottom represents a low-voltage bridge alternating current inflow conduction width, t D_top represents a low-voltage bridge alternating current outflow conduction width, t YHV1 , t YHV3 , and t YHV5 represent time widths of a high-voltage bridge common anode valve conduction state, t YHV2 , t YHV4 , and t YHV6 represent time widths of a high-voltage bridge common cathode valve conduction state, t DHV1 , t DHV3 , and t DHV5 represent time widths of a low-voltage bridge common anode valve conduction state, and t DHV2 , t DHV4 , and t DHV6 represent time widths of a low-voltage bridge common cathode valve conduction state; the horizontal and vertical timing features being constructed on the circuit structure of the converter according to the alternating current conduction width and the direct current conduction width based on the following formulas: { t DCVTF = t dH - t dN t ACVTF ⁢ _ ⁢ HB = t Y ⁢ _ ⁢ top - t Y _ ⁢ bottom t ACVTF ⁢ _ ⁢ LB = t D ⁢ _ ⁢ top - t D _ ⁢ bottom t ACVTF ⁢ _ ⁢ HLB = t Y_bottom - t D ⁢ _ ⁢ top ; { t THTF ⁢ _ ⁢ HB = t dH - t Y ⁢ _ ⁢ top t THTF ⁢ _ ⁢ LB = t dH - t D _ ⁢ top t BHTF ⁢ _ ⁢ HB = t dN - t Y _ ⁢ bottom t BHTF ⁢ _ ⁢ LB = t dN - t D ⁢ _ ⁢ bottom wherein t DCVTF represents a direct-current vertical timing feature, t ACVTF_HB represents a high-voltage bridge vertical timing feature, t ACVTF_LB represents a low-voltage bridge vertical timing feature, t ACVTF_HLB represents a double-bridge vertical timing feature, t THTF_HB represents a high-voltage bridge top horizontal timing feature, t THTF_LB represents a low-voltage bridge top horizontal timing feature, t BHTF_HB represents a high-voltage bridge bottom horizontal timing feature, t BHTF_LB represents a low-voltage bridge bottom horizontal timing feature, t dH represents a direct current inflow conduction width, t dN represents a direct current outflow conduction width, t Y_top represents a high-voltage bridge alternating current outflow conduction width, t Y_bottom represents a high-voltage bridge alternating current inflow conduction width, t D_top represents a low-voltage bridge alternating current outflow conduction width, and t D_bottom represents a low-voltage bridge alternating current inflow conduction width; and adjusting the high-voltage direct current transmission system based on fault location to ensure power transmission of the high-voltage direct current transmission system.
2 . The valve-level fault location method for the converter according to claim 1 , wherein the calculating a time width of each valve conduction state, an alternating current conduction width, and a direct current conduction width based on the current data specifically comprises: calculating a plurality of valve currents of the j bridge and a valve current base value of the j bridge according to absolute values of the three-phase alternating currents of the j bridge; selecting a ratio of one of the valve currents to the valve current base value as a valve current relative relationship, so as to obtain a plurality of valve current relative relationships; and obtaining a plurality of valve conduction states according to each valve current relative relationship, and integrating each valve conduction state to obtain a time width of each valve conduction state.
3 . The valve-level fault location method for the converter according to claim 2 , wherein the plurality of valve currents of the j bridge are calculated according to the absolute values of the three-phase alternating currents of the j bridge based on the following formulas: i jV ⁢ 4 = { i ja ; i ja > 0 0 ; i ja ≤ 0 i jV ⁢ 1 = { - i ja ; i ja < 0 0 ; i ja ≥ 0 | i jV ⁢ 6 = { i jb ; i jb > 0 0 ; i jb ≤ 0 i jV ⁢ 3 = { - i jb ; i jb < 0 0 ; i jb ≥ 0 | i jV ⁢ 2 = { i jc ; i jc > 0 0 ; i jc ≤ 0 i jV ⁢ 5 = { - i jc ; i jc < 0 0 ; i jc ≥ 0 wherein j=Y/D, i jV1 represents a j-bridge V1 valve current, i jV2 represents a j-bridge V2 valve current, i jV3 represents a j-bridge V3 valve current, i jV4 represents a j-bridge V4 valve current, i jV5 represents a j-bridge V5 valve current, and i jV6 represents a j-bridge V6 valve current, wherein i ja , i jb , and i jc , ijb, ijc represent the three-phase alternating current of the j bridge; and the calculating a valve current base value of the j bridge according to absolute values of the three-phase alternating currents of the j bridge specifically comprises: selecting half of a maximum value in the absolute values of the three-phase alternating currents of the j bridge as a valve current base value i jbase of the j bridge.
4 . The valve-level fault location method for the converters according to claim 2 , wherein the obtaining a plurality of valve conduction states according to each valve current relative relationship and integrating each valve conduction state to obtain a time width of each valve conduction state specifically comprises: inputting each valve current relative relationship into a single-phase comparator, and obtaining a duty ratio of each valve current; selecting a state in which the duty ratio of the valve current is greater than 1 as a valve conduction state, so as to obtain a plurality of valve conduction states; and integrating each valve conduction state to obtain the time width of each valve conduction state based on the following formula: t jHVm = ∫ - T 0 S jHVm ⁢ dt wherein j=Y/D, m=1, 2, 3, 4, 5, 6, S jHVm represents a j-bridge Vm valve conduction state, t jHVm represents a time width of the j-bridge Vm valve conduction state, and T represents a time width of a power frequency cycle.
5 . The valve-level fault location method for the converter according to claim 2 , wherein—the constructing a direct current conduction width according to a direct-current high-voltage current amplitude and a direct-current neutral current amplitude specifically comprises: defining a flow state of a direct-current high-voltage current and a flow state of a direct-current neutral current according to the direct-current high-voltage current amplitude and the direct-current neutral current amplitude based on the following formulas: S dH = { 1 ; i dH ≥ i set 0 ; i dH < i set ; S dN = { 1 ; i dN ≥ i set 0 ; i dN < i set wherein i dH represents the direct-current high-voltage current, id represents the direct-current neutral current, S dH represents the flow state of the direct-current high-voltage current, S dN represents the flow state of the direct-current neutral current, and i set represents a threshold of a direct current flow state; and integrating the flow state of the direct-current high-voltage current and the flow state of the direct-current neutral current in each power frequency cycle to obtain a direct current conduction width based on the following formulas: t dH = ∫ t - T t S dH ⁢ dt ; t dN = ∫ t - T t S dN ⁢ dt wherein t dH represents a direct current inflow conduction width, t dN represents a direct current outflow conduction width, and T represents a time width of a power frequency cycle.
6 . The valve-level fault location method for the converter according to claim 1 , wherein the implementing valve-level fault location for the converter according to the time width of each valve conduction state, the alternating current conduction width, the direct current conduction width, the horizontal and vertical timing features, each valve state signal, and the current data specifically comprises: determining whether the direct current inflow conduction width is less than the power frequency cycle; determining that a fault is a line fault k9 if the direct current inflow conduction width is less than the power frequency cycle; determining whether the direct-current vertical timing feature satisfies t dH −t dN >Δ if the direct current inflow conduction width is greater than or equal to the power frequency cycle, wherein Δ represents a value greater than 0; determining whether the high-voltage bridge vertical timing feature satisfies t Y_top ≠t Y_bottom or whether the low-voltage bridge vertical timing feature satisfies t D_top ≠t D_bottom if the direct-current vertical timing feature satisfies t dH −t dN >Δ; determining that the fault is an external fault k7 if the high-voltage bridge vertical timing feature satisfies t Y_top ≠t Y_bottom or the low-voltage bridge vertical timing feature satisfies t D_top ≠t D_bottom ; determining that the faults are internal fault k4 and k5 if the high-voltage bridge vertical timing feature does not satisfy t Y_top ≠t Y_bottom or the low-voltage bridge vertical timing feature does not satisfy t D_top ≠t D_bottom ; determining whether the valve state signal is abnormal according to each valve state signal if the direct-current vertical timing feature does not satisfy t dH −t dN >Δ; determining, if the valve state signal is abnormal, whether three conditions are simultaneously satisfied: a maximum value of the direct-current high-voltage current and the direct-current neutral current is greater than a maximum value of the three-phase alternating currents of the j bridge, commutation fails, and there is no difference in high-voltage bridge or low-voltage bridge top horizontal timing features, if yes, determining that the faults are external faults k6 and k8, and if no, determining that the faults are internal faults k1, k2, and k3; and returning to collecting current data of a converter if the valve state signal is not abnormal.
7 . The valve-level fault location method for the converter according to claim 6 , further comprising: further locating the internal faults to implement fault valve and fault phase location, specifically: determining each internal fault type using data of the horizontal and vertical timing features in a time window width according to internal faults k1-k5, and obtaining internal fault types of k1, k3, and k5 which are successfully determined; and implementing fault valve and fault phase location using data of the time width of each valve conduction state in a converter bridge where the internal fault types of k1, k3, and k5 are located in the time window width.
8 . A valve-level fault location system for a converter based on horizontal and vertical state differences of valves, the fault location system being used for monitoring the converter of a high-voltage direct current transmission system, the fault location system comprising: . . . a collection unit, configured to collect current data of the converter, the current data . . . and t D_bottom represent a low-voltage bridge alternating current inflow conduction width; and adjusting the high-voltage direct current transmission system based on fault location to ensure power transmission of the high-voltage direct current transmission system.

Description

FIELD OF THE INVENTION The present disclosure relates to a valve-level fault location method and system for converters based on horizontal and vertical state differences of valves, which fall within the technical field of high-voltage direct current transmission. BACKGROUND OF THE INVENTION As a core element of a high-voltage direct current transmission system, a converter realizes the function of alternating current and direct current conversion. However, the converter is characterized by being easily damaged and expensive, and it is therefore necessary to ensure the operation safety of the converter. Therefore, it is of great significance to quickly locate faults of the converter to clear the faults in time and ensure the power transmission. The existing methods are to mainly locate fault points through protection actions of the converter in combination with fault response features within a period of time after the converter is faulted. However, the methods mainly have the following two problems: firstly, under the action of a control system, current amplitude features after the converter is faulted are not obvious, which easily leads to the failure of the existing fault location methods; secondly, under the condition of external faults, the response of the converter makes electrical features of the external faults similar to electrical features of internal faults, which results in the uncertainty of the protection actions, thus easily leading to the misjudgment of fault locations. Further, even if current research is capable of correctly determine fault types, fault valves and fault phases under fault types cannot be identified. In order to quickly locate the fault valves and the fault phase, it is proposed to add current measuring points on each bridge arm of the converter. However, the addition of the measuring points is not easy to realize in engineering, increases the equipment cost, and has great limitations in engineering application. For this reason, there is an urgent need for a valve-level fault location method for converters based on horizontal and vertical state differences of valves, which has small limitations, low cost and can quickly locate fault valves and fault phases. SUMMARY OF THE INVENTION In view of this, the present disclosure provides a valve-level fault location method and system for converters based on horizontal and vertical state differences of valves. By constructing a difference between horizontal and vertical conduction widths of an alternating current and a direct current based on current timing features, valve-level faults of converters can be accurately located, thereby assisting in adjusting a power system and handling faults by staff. A first object of the present disclosure is to provide a valve-level fault location method for converters based on horizontal and vertical state differences of valves. A second object of the present disclosure is to provide a valve-level fault location system for converters based on horizontal and vertical state differences of valves. A third object of the present disclosure is to provide a computer device. A fourth object of the present disclosure is to provide a storage medium. The first object of the present disclosure may be achieved by adopting the following technical solution. The valve-level fault location method for converters based on horizontal and vertical state differences of valves includes: collecting current data of a converter, the current data including three-phase alternating currents of a j bridge, a direct-current high-voltage current, and a direct-current neutral current, where j=Y/D, Y representing a high voltage, and D representing a low voltage;calculating a time width of each valve conduction state, an alternating current conduction width, and a direct current conduction width based on the current data;constructing horizontal and vertical timing features on a circuit structure of the converter according to the alternating current conduction width and the direct current conduction width;comparing the time width of each valve conduction state with a time width of a normal valve conduction state, and outputting each valve state signal; andimplementing valve-level fault location for the converter according to the time width of each valve conduction state, the alternating current conduction width, the direct current conduction width, the horizontal and vertical timing features, each valve state signal, and the current data. Further, the calculating a time width of each valve conduction state, an alternating current conduction width, and a direct current conduction width based on the current data specifically includes: calculating a plurality of valve currents of the j bridge and a valve current base value of the j bridge according to absolute values of the three-phase alternating currents of the j bridge;selecting a ratio of one of the valve currents to the valve current base value as a valve current relative relations