Direct-current power transmission system commutation failure fault diagnosis method and device and storage medium

Abstract

The invention discloses a direct-current power transmission system commutation failure fault diagnosis method and device and a storage medium, and belongs to the technical field of direct-current power transmission system fault diagnosis. According to the direct-current power transmission system commutation failure fault diagnosis method, the fault of a trigger system is diagnosed by detecting the commutation state of a converter valve group at the moment of direct-current bypass; or detecting the conduction time of the conduction phase of the three-phase alternating current in a preset time window at the moment of direct current bypass, and judging the fault type of the converter valve triggering system based on the maximum conduction time; according to the application, the fault type of the commutation failure can be quickly positioned only by detecting the commutation state of the converter valve group or detecting the maximum conduction time in the time window before the DC bypass moment, and which converter valve has the fault is further positioned through the valve side current or the trigger pulse signal word, so that the fault of the converter valve group can be accurately positioned. And operation and maintenance personnel can handle faults in time.

Description

Technical Field

[0001] The present application relates to the technical field of DC transmission system fault diagnosis, and specifically relates to a method, device and storage medium for diagnosing commutation failure faults in a DC transmission system. Background Art

[0002] The converter valve group is one of the most important devices in high-voltage DC transmission. There are two conditions for the thyristor of the converter valve to turn on: one is that a positive voltage is obtained on the valve group, and the other is that there is a trigger pulse. The commutation failure of the converter valve group is a common fault and phenomenon in high-voltage DC transmission. According to the two turn-on conditions of the converter valve, it can be known that the two main factors causing commutation failure are: AC system disturbance or fault, and converter valve trigger system fault.

[0003] At present, most studies focus on commutation failure caused by AC system disturbance or fault, and there is no research on commutation failure caused by trigger system fault. In actual DC projects, commutation failure caused by trigger system fault is also relatively common. For commutation failure caused by AC disturbance or fault, it generally does not need to be processed in the DC system, while for commutation failure caused by trigger system fault, defect elimination needs to be carried out in time; however, there is currently no fast and effective fault diagnosis method, and fault troubleshooting and defect elimination mainly rely on the experience of operation and maintenance personnel, with low efficiency and slow speed. There is an urgent need to explore a fast diagnosis method for commutation failure caused by converter valve trigger system fault to improve the speed and efficiency of on-site operation and maintenance personnel in handling faults and eliminating defects. Summary of the Invention

[0004] Object of the Invention: The purpose of the embodiments of the present application is to provide a method, device and storage medium for diagnosing commutation failure faults in a DC transmission system, aiming to solve the technical problem of how to diagnose commutation failure caused by trigger system fault.

[0005] Technical Solution: In a first aspect, the embodiments of the present application provide a method for diagnosing commutation failure faults in a DC transmission system. The DC transmission system includes a converter valve group and a converter valve trigger system. The AC side of the converter valve group is connected to a three-phase AC current, the DC side of the converter valve group is connected to a DC transmission line, and the converter valve trigger system is connected to the control end of the converter valve group to output a pulse signal word for commutation control of the converter valve group;

[0006] The method includes:

[0007] In response to detecting that the converter valve group is in a commutation state at the moment of DC bypass, it is determined that the converter valve trigger system has a lost pulse fault;

[0008] In response to detecting that the converter valve group is not in a commutation state at the moment of DC bypass, it is determined that the converter valve trigger system has a mis-triggering fault; or,

[0009] Within a time window preset before the instant of DC bypass, perform the following steps:

[0010] In response to detecting that the maximum conduction time among the conduction times of the conduction phases of the three-phase alternating current is greater than 120° electrical angle, determine that the commutation valve trigger system has the missing pulse fault;

[0011] In response to detecting that the maximum conduction time among the conduction times of the conduction phases of the three-phase alternating current is less than 120° electrical angle, determine that the commutation valve trigger system has the mis-triggering fault.

[0012] In some embodiments, the method for determining the instant of DC bypass includes:

[0013] Collect the three-phase alternating current at a preset sampling point;

[0014] The sampling moment corresponding to the first sampling point that satisfies the first preset condition is the instant of DC bypass, and the first preset condition is:

[0015] MAX{ABS(IVY_L1), ABS(IVY_L2), ABS(IVY_L3)} < k1 * ID_NOM;

[0016] MAX{ABS(IVD_L1), ABS(IVD_L2), ABS(IVD_L3)} < k1 * ID_NOM;

[0017] Wherein, ABS is the absolute value, MAX is the operation of taking the maximum value; IVY_L1 is the valve-side current of phase A of the Y-bridge; IVY_L2 is the valve-side current of phase B of the Y-bridge; IVY_L3 is the valve-side current of phase C of the Y-bridge; IVD_L1 is the valve-side current of phase A of the D-bridge; IVD_L2 is the valve-side current of phase B of the D-bridge; IVD_L3 is the valve-side current of phase C of the D-bridge; k1 is the first proportionality coefficient; ID_NOM is the rated DC current of the DC transmission line.

[0018] In some embodiments, the method for determining whether the commutation valve group is in the commutation state includes:

[0019] Obtain a first pulse signal word and a second pulse signal word, where the first pulse signal word is the pulse signal word at the instant of DC bypass, and the second pulse signal word is: the first pulse signal word different from the first pulse signal word searched forward from the instant of DC bypass;

[0020] The acquisition position of the first pulse signal word is the first position, and the acquisition position of the second pulse signal word is the second position;

[0021] In response to detecting that both the first position and the second position are within two adjacent pulse signal word sampling points, it is determined that the converter valve group is in the commutation state; otherwise, it is determined that the converter valve group is not in the commutation state.

[0022] In some embodiments, the step of determining that there is a missing pulse fault in the converter valve triggering system in response to detecting that the maximum conduction time in the conduction times of the three-phase alternating current conduction phases is greater than 120° electrical angle includes:

[0023] Obtain the conduction phase of the converter valve group based on a second preset condition;

[0024] Accumulate the sampling points of the conduction phase until the second preset condition is not satisfied, obtain the conduction sampling points of each conduction phase, and confirm the conduction time corresponding to the conduction phase based on the sampling points;

[0025] In response to the maximum conduction time in the conduction phases being greater than 120° electrical angle, it is determined that there is a missing pulse fault in the converter valve triggering system.

[0026] In some embodiments, the second preset condition includes:

[0027] ABS(IVY_L1)>k2*ID_NOM;

[0028] ABS(IVY_L2)>k2*ID_NOM;

[0029] ABS(IVY_L3)>k2*ID_NOM;

[0030] ABS(IVD_L1)>k2*ID_NOM;

[0031] ABS(IVD_L2)>k2*ID_NOM;

[0032] ABS(IVD_L3)>k2*ID_NOM;

[0033] Wherein, ABS is the absolute value; IVY_L1 is the valve-side current of phase A of the Y-bridge; IVY_L2 is the valve-side current of phase B of the Y-bridge; IVY_L3 is the valve-side current of phase C of the Y-bridge; IVD_L1 is the valve-side current of phase A of the D-bridge; IVD_L2 is the valve-side current of phase B of the D-bridge; IVD_L3 is the valve-side current of phase C of the D-bridge; k2 is the second proportionality coefficient; ID_NOM is the rated direct current of the HVDC transmission line.

[0034] In some embodiments, the step of obtaining the conduction phase of the converter valve group based on the second preset condition includes:

[0035] Collect the three-phase alternating current at a preset sampling point;

[0036] Determine the phase in which the alternating current satisfies the second preset condition as the conducting phase.

[0037] In some embodiments, when the maximum conduction time among the conduction times of the conducting phases of the three-phase current is less than 120° electrical angle, the commutation valve triggering system has a mis-triggering fault, including:

[0038] Obtain the conducting phase of the commutation valve group based on the second preset condition;

[0039] Accumulate the sampling points of the conducting phases that meet the third preset condition until they no longer meet the third preset condition, and obtain the conduction time of each conducting phase;

[0040] In response to the conduction time of each conducting phase being less than 120° electrical angle, determine that the commutation valve triggering system has a mis-triggering fault.

[0041] In some embodiments, the third preset condition includes:

[0042] IPOS > k3 * ID_NOM;

[0043] And INEG < -k3 * ID_NOM;

[0044] Wherein, IPOS is the conducting phase with a positive alternating current sampling value among the three phases; INEG is the conducting phase with a negative alternating current sampling value among the three phases; k3 is the third proportionality coefficient.

[0045] In some embodiments, the commutation failure fault diagnosis method for the HVDC system further includes:

[0046] In response to a pulse loss fault, obtain the trigger pulse signal word cpr1 at the instant of DC bypass and the trigger pulse signal word cpr2 before the DC bypass, and solve for the commutation valve with the lost pulse, including:

[0047] Determine the first logical AND result Vnum1, and the expression is as follows:

[0048] Vnum1 = cpr1 & cpr2;

[0049] Wherein, & is the bitwise AND operator;

[0050] In the first logical AND result Vnum1, search from the low bit to the high bit in binary number form, and obtain the position serial number of the first digit 1, which is determined as the number of the commutation valve with the lost pulse.

[0051] In some embodiments, the commutation failure fault diagnosis method for the HVDC system further includes:

[0052] Determine the phase with the maximum conduction time among the conduction times of the three-phase current conducting phases as the maximum conduction phase;

[0053] In response to the conduction time of the maximum conduction phase being greater than 120° electrical angle, based on the commutation sequence of the commutation valve, the commutation valve to be commutated corresponding to the maximum conduction phase is determined as the commutation valve with a lost pulse.

[0054] In some embodiments, the commutation failure fault diagnosis method for the HVDC transmission system further includes:

[0055] In response to a mis-triggering fault, obtain the trigger pulse signal word cpr1 at the moment of DC bypass;

[0056] Based on the trigger pulse signal word cpr1 at the moment of DC bypass, obtain the number combination cprm of the two bypass valve pairs of the conducting valve;

[0057] Obtain the first pulse signal word cprn after the HVDC transmission system resumes commutation;

[0058] Based on the number combination cprm of the two bypass valve pairs of the conducting valve at the moment of DC bypass and the first pulse signal word cprn after the HVDC transmission system resumes commutation, determine the number of the commutating valve mis-triggered:

[0059] Vnum2 = cprm ^ (cprm & cprn);

[0060] where Vnum2 is the second logical AND result;

[0061] In the second logical AND result Vnum2, search from the low bit to the high bit in binary form, obtain the position sequence number of the first digit 1, and determine it as the number of the commutating valve mis-triggered.

[0062] In some embodiments, the commutation failure fault diagnosis method for the HVDC transmission system further includes:

[0063] After the HVDC transmission system resumes commutation, calculate the AC current of each conducting phase in the HVDC transmission system;

[0064] Solve the conduction time of the maximum conduction phase based on the AC current of each conducting phase;

[0065] In response to the conduction time of the maximum conduction phase being greater than 120° electrical angle, the commutation valve corresponding to the AC current of the maximum conduction phase is the commutating valve mis-triggered.

[0066] In some embodiments, the value range of the preset time window is 0 - 1 cycle.

[0067] In some embodiments, the value range of the first proportionality coefficient is 0 - 0.1.

[0068] In some embodiments, the value range of the second proportionality coefficient is 0 - 0.1.

[0069] In some embodiments, the value range of the third proportionality coefficient is 0 - 0.1.

[0070] In a second aspect, the present application provides a commutation failure fault diagnosis device for a DC transmission system, including a processor and a memory. The memory stores a computer program executable by the processor, and when the processor executes the computer program, it implements the commutation failure fault diagnosis method for the DC transmission system described in any one of the first aspects.

[0071] In a third aspect, the present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is run by a processor, it executes the commutation failure fault diagnosis method for the DC transmission system described in any one of the first aspects.

[0072] Beneficial effects: Compared with the prior art, the present application embodiment provides a commutation failure fault diagnosis method for a DC transmission system. The commutation failure fault diagnosis method of the present application diagnoses the faults of the trigger system by detecting the state of the converter valve group at the moment of DC bypass. At the moment of DC bypass, if the converter valve group is in the commutation state, it is determined that the reason for the commutation failure of the DC commutation system is the loss of pulse fault in the converter valve trigger system; if the converter valve group is not in the commutation state, it is determined that the reason for the commutation failure of the DC commutation system is the mis-triggering fault in the converter valve trigger system; or, within a preset time window before the moment of DC bypass, the conduction time of the conduction phase of the three-phase alternating current is detected. If the conduction time of the maximum conduction phase is greater than 120° electrical angle, it is determined that there is a loss of pulse fault in the converter valve trigger system. If the conduction time of the maximum conduction phase is less than 120° electrical angle, it is determined that there is a mis-triggering fault in the converter valve trigger system. The present application can quickly locate the fault type of commutation failure only by detecting the commutation state of the converter valve group or detecting the maximum conduction time within the time window before the moment of DC bypass;

[0073] At the same time, the commutation failure fault diagnosis method provided by the embodiment of the present application further locates the specific converter valve where the fault occurs by detecting the valve-side current or the trigger pulse signal word, which helps the operation and maintenance personnel to dispose of the fault in time.

[0074] The embodiment of the present application provides a commutation failure fault diagnosis device for a DC transmission system, which is used to execute the commutation failure fault diagnosis method of the present application. The fault type of commutation failure can be quickly located only by detecting the commutation state of the converter valve group or detecting the maximum conduction time within the time window before the moment of DC bypass;

[0075] Meanwhile, a commutation failure fault diagnosis device provided by an embodiment of the present application can further locate the specific converter valve where the fault occurs by detecting the valve-side current or the trigger pulse signal word, which helps the operation and maintenance personnel to promptly handle the fault.

[0076] An embodiment of the present application provides a computer-readable storage medium for executing the commutation failure fault diagnosis method of the present application. By only detecting the commutation state of the converter valve group or detecting the maximum conduction time within a time window before the DC bypass moment, the fault type of commutation failure can be quickly located.

[0077] When a computer-readable storage medium provided by an embodiment of the application executes the commutation failure fault diagnosis method of the present application, the specific converter valve where the fault occurs can be further located by detecting the valve-side current or the trigger pulse signal word, which helps the operation and maintenance personnel to promptly handle the fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0079] Figure 1 It is a step flow chart of a commutation failure fault diagnosis method for a DC transmission system provided by an embodiment of the present application.

[0080] Figure 2 It is a step flow chart of Method 1 in a commutation failure fault diagnosis method for a DC transmission system provided by an embodiment of the present application.

[0081] Figure 3 It is a step flow chart of the steps related to determining the faulty converter valve in Method 2 of a commutation failure fault diagnosis method for a DC transmission system provided by an embodiment of the present application.

[0082] Figure 4 It is a step flow chart of determining the faulty converter valve when a lost pulse fault occurs in a commutation failure fault diagnosis method for a DC transmission system provided by an embodiment of the present application.

[0083] Figure 5 It is a step flow chart of determining the faulty converter valve when a mis-triggering fault occurs in a commutation failure fault diagnosis method for a DC transmission system provided by an embodiment of the present application.

[0084] Figure 6Schematic diagram of the lost pulse fault of the Y-bridge in Case 1. The first sub-diagram shows the three-phase currents IACY_L1, IACY_L2, and IACY_L3 on the valve star side, and the second sub-diagram shows the Y-bridge trigger pulse signal word CPRY;

[0085] Figure 7 Schematic diagram of the mis-triggering fault of the Y-bridge in Case 2. The first sub-diagram shows the three-phase currents IACY_L1, IACY_L2, and IACY_L3 on the valve star side, and the second sub-diagram shows the Y-bridge trigger pulse signal word CPRY;

[0086] Figure 8 Schematic diagram of the structure of the 12-pulse bridge converter valve in the inverter station. Specific implementation manners

[0087] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts belong to the scope of protection of the present application.

[0088] The terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0089] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0090] The DC power transmission system includes a converter valve group and a converter valve trigger system. The AC side of the converter valve group is connected to the three-phase AC current, the DC side of the converter valve group is connected to the DC power transmission line, and the converter valve trigger system is connected to the control end of the converter valve group to output a pulse signal word for phase commutation control of the converter valve group.

[0091] The commutation failure caused by the converter valve trigger system fault can be divided into mis-triggering fault and lost pulse fault (also called non-triggering fault), and the two have different fault characteristics. The mis-triggering principle can be described as: Please refer to Figure 8, Assume that the currently conducting converter valves are V1 and V2. If V4 or V5 is misapplied with a trigger pulse and conducts at this time, it will cause the DC bypass of phase A where V1 and V4 are located or phase C where V2 and V5 are located, resulting in commutation failure. The principle of pulse loss can be described as follows: Assume that the currently conducting converter valves are V1 and V2. Next, it should be the turn of V1 and V3 to commutate. If the trigger pulse is not applied to V3 due to a fault at this time, V3 cannot conduct, so V1 cannot turn off. Subsequently, after V2 and V4 commutate successfully normally, it will form a DC bypass of phase A where V1 and V4 are located, leading to commutation failure.

[0092] Based on the above principles of commutation failure caused by mis-triggering and pulse loss, the present invention proposes a method for diagnosing commutation failure faults in a DC system. The following takes a 6-pulse converter valve as an example for illustration. The content of the invention can be applied to both Y-bridge 6-pulse converter valves and D-bridge 6-pulse converter valves, and is not limited to two 6-pulse converter valves in series (i.e., 12-pulse converter valves), nor is it limited to topologies such as two 12-pulse converter valves in series or parallel.

[0093] Please refer to Figures 1 to 5 , The embodiment of the present application provides a method for diagnosing commutation failure faults in a DC transmission system. The method for diagnosing commutation failure faults in the DC transmission system of the present application diagnoses the faults of the trigger system by detecting the state of the converter valve group at the moment of DC bypass. At the moment of DC bypass, if the converter valve group is in the commutation state, it is determined that the reason for the commutation failure of the DC transmission system is a pulse loss fault in the converter valve trigger system; if the converter valve group is not in the commutation state, it is determined that the reason for the commutation failure of the DC transmission system is a mis-triggering fault in the converter valve trigger system; or, within a preset time window before the moment of DC bypass, the conduction time of the conducting phase of the three-phase alternating current is detected. If the conduction time of the maximum conducting phase is greater than 120° electrical angle, it is determined that there is a pulse loss fault in the converter valve trigger system. If the conduction time of the maximum conducting phase is less than 120° electrical angle, it is determined that there is a mis-triggering fault in the converter valve trigger system. The present application can quickly locate the fault type of commutation failure only by detecting the commutation state of the converter valve group at the moment of DC bypass, or detect the conduction time of the conducting phase of the three-phase alternating current within the time window before the moment of DC bypass to determine the fault type, which helps the operation and maintenance personnel to dispose of the fault in time.

[0094] The present application provides a method for diagnosing commutation failure faults in a DC transmission system, specifically including:

[0095] Please refer to Figure 1 and Figure 2 , Method 1: After the commutation failure of the DC transmission system, detect the commutation state of the converter valve group at the moment of DC bypass, and determine the fault type of the converter valve trigger system based on the commutation state of the converter valve group. Or,

[0096] Please refer to Figure 1 and Figure 3 Method 2: After commutation failure of the HVDC system, within a preset time window before the instant of DC bypass, detect the maximum conduction time in the conducting phase of the three-phase AC current, and determine the fault type of the converter valve triggering system based on the maximum conduction time in the conducting phase of the three-phase AC current.

[0097] Please refer to Figure 1 and Figure 2 In Method 1, this application provides a method for diagnosing commutation failure faults in an HVDC system, specifically including:

[0098] Step a: After commutation failure of the HVDC system, obtain the commutation state of the converter valve group at the instant of DC bypass, and determine the fault type of the converter valve triggering system.

[0099] Step a.1: After commutation failure of the HVDC system, determine the instant of DC bypass.

[0100] The method for determining the instant of DC bypass includes:

[0101] Collect the three-phase AC current at the preset sampling points;

[0102] The sampling moment corresponding to the first sampling point that satisfies the first preset condition is the instant of DC bypass. The first preset condition is:

[0103] The instant of DC bypass is judged by the formulas (1-1) and (1-2) of the first preset condition. The one that satisfies formula (1-1) is the instant of DC bypass of the Y-bridge, and the one that satisfies formula (1-2) is the instant of DC bypass of the D-bridge:

[0104] MAX{ABS(IVY_L1),ABS(IVY_L2),ABS(IVY_L3)}<k1*ID_NOM; Formula (1-1)

[0105] MAX{ABS(IVD_L1),ABS(IVD_L2),ABS(IVD_L3)}<k1*ID_NOM; Formula (1-2)

[0106] Where, ABS is the absolute value, MAX is the operation of taking the maximum value; IVY_L1 is the valve-side current of phase A of the Y-bridge; IVY_L2 is the valve-side current of phase B of the Y-bridge; IVY_L3 is the valve-side current of phase C of the Y-bridge; IVD_L1 is the valve-side current of phase A of the D-bridge; IVD_L2 is the valve-side current of phase B of the D-bridge; IVD_L3 is the valve-side current of phase C of the D-bridge; k1 is the first proportionality coefficient, and the value range is 0 to 0.1; ID_NOM is the rated DC current of the HVDC system.

[0107] In response to detecting that the DC bypass instantaneous converter valve group is in the commutation state, it is determined that there is a missing pulse fault in the converter valve triggering system.

[0108] Step a.2: After determining the DC bypass instant, determine the commutation state of the converter valve group.

[0109] Step a.2.1: Obtain a first pulse signal word and a second pulse signal word. The first pulse signal word is the pulse signal word at the DC bypass instant, and the second pulse signal word is the first pulse signal word different from the first pulse signal word searched forward from the DC bypass instant.

[0110] Specifically, take out the CPR value at the DC bypass instant, denoted as cpr1, as the first pulse signal word; search forward from the DC bypass instant to find the first CPR value different from cpr1, denoted as cpr2, as the second pulse signal word.

[0111] Step a.2.2: The acquisition position of the first pulse signal word is the first position, and the acquisition position of the second pulse signal word is the second position;

[0112] Specifically, the position where cpr1 is obtained is the first position, and the position where cpr2 is obtained is the second position.

[0113] Step a.2.3: In response to both the first position and the second position being within the sampling points of the CPR values of two adjacent pulse signal words, it is determined that the converter valve group is in the commutation state.

[0114] Step a.3: Based on the commutation state of the converter valve group, determine the specific fault.

[0115] Specifically, in response to detecting that the DC bypass instantaneous converter valve group is in the commutation state, it is determined that there is a missing pulse fault in the converter valve triggering system.

[0116] Specifically, in response to detecting that the DC bypass instantaneous converter valve group is not in the commutation state, it is determined that there is a mis-triggering fault in the converter valve triggering system.

[0117] Specifically, if the positions of cpr1 and cpr2 are within two adjacent sampling points, it is determined that the trigger pulse has just changed, that is, the converter valve group is in the commutation state, and it is judged as a missing pulse fault; otherwise, it is considered that the trigger pulse has not changed, and it is judged as a mis-triggering fault.

[0118] Please refer to Figure 1 and Figure 3 , in Method 2, the present application provides a method for diagnosing commutation failure faults in a DC power transmission system, which specifically includes:

[0119] Step b: After commutation failure occurs in the HVDC system, within a preset time window before the instant of DC bypass, obtain the maximum conduction time among the conduction times of the conducting phases of the three-phase alternating current, and determine the fault type of the converter valve triggering system.

[0120] Step b.1: After commutation failure occurs in the HVDC system, determine the instant of DC bypass, and within a preset time window before the instant of DC bypass, conduct fault determination.

[0121] Specifically, the step of determining the instant of DC bypass has been mentioned and will not be elaborated here. The value range of the time window is 0 to 1 cycle. In some embodiments, one cycle of a 50Hz AC system is 20ms, and one cycle of a 60Hz AC system is 16.67ms.

[0122] Step b.2: Obtain the conducting phases of the converter valve group.

[0123] Step b.2.1: Collect three-phase alternating current at a preset sampling point.

[0124] Step b.2.2: If the alternating current meets the second preset condition, it is determined as the conducting phase.

[0125] Among them, the second preset condition is: the absolute value of the alternating current is greater than the product of the rated DC current of the HVDC system and the second proportionality coefficient:

[0126] Specifically, ABS(IVY_L1)>k2*ID_NOM; Equation (2-1), phase A of the Y-bridge converter valve is the conducting phase;

[0127] ABS(IVY_L2)>k2*ID_NOM; Equation (2-2), phase B of the Y-bridge converter valve is the conducting phase;

[0128] ABS(IVY_L3)>k2*ID_NOM; Equation (2-3), phase C of the Y-bridge converter valve is the conducting phase;

[0129] ABS(IVD_L1)>k2*ID_NOM; Equation (2-4), phase A of the D-bridge converter valve is the conducting phase;

[0130] ABS(IVD_L2)>k2*ID_NOM; Equation (2-5), phase B of the D-bridge converter valve is the conducting phase;

[0131] ABS(IVD_L3)>k2*ID_NOM; Equation (2-6), phase C of the D-bridge converter valve is the conducting phase;

[0132] Among them, ABS is the absolute value, k2 is the second proportionality coefficient, and the value range is 0 to 0.1.

[0133] Step b.3: Obtain the maximum conduction time in the conduction phases of the three-phase current, and determine the cause of the fault based on the maximum conduction time.

[0134] Step b.3.a: Determine the missing pulse fault.

[0135] Step b.3.a.1: Accumulate the sampling points of the conduction phases until the second preset condition is not satisfied, obtain the conduction sampling points of each conduction phase, and confirm the conduction time of the corresponding conduction phase based on the sampling points;

[0136] Among them, the accumulated sampling points refer to the cumulative sampling point count when the second preset condition is satisfied.

[0137] Specifically, according to the sampling frequency, each sampling point corresponds to a time. For example, if 1000 points are sampled per second, then each sampling point corresponds to 1 ms. The accumulated sampling points can calculate the corresponding conduction time, and the conduction time corresponds to the electrical angle. For example, in a 50 Hz AC system, 20 ms corresponds to 360° electrical angle.

[0138] Step b.3.a.2: In response to the maximum conduction time corresponding to the conduction phase being greater than 120° electrical angle, determine that there is a missing pulse fault in the converter valve trigger system.

[0139] Step b.3.b: Determine the mis-triggering fault.

[0140] Step b.3.b.1: Accumulate the sampling points of the conduction phases that meet the third preset condition until the third preset condition is not satisfied, and obtain the conduction time of each conduction phase.

[0141] Among them, the third preset condition includes:

[0142] IPOS > k3 * ID_NOM; and INEG < -k3 * ID_NOM; Equation (3)

[0143] Among them, IPOS is the current of the conduction phase with a positive AC current sampling value among the three phases; INEG is the current of the conduction phase with a negative AC current sampling value among the three phases; k3 is the third proportionality coefficient, and the value range is 0 to 0.1.

[0144] Step b.3.b.2: In response to the conduction time of each conduction phase being less than 120° electrical angle, determine that there is a mis-triggering fault in the converter valve trigger system.

[0145] Please refer to Figure 4 and Figure 5 , after determining the fault type of the converter valve system based on steps a and b, the steps for determining the faulty valve group for different fault types include:

[0146] Step c: For the fault type of the converter valve, solve the faulty converter valve.

[0147] Step c.a: For the lost pulse fault, solve the converter valve with the lost pulse:

[0148] Step c.a.a: In response to the lost pulse fault, obtain the trigger pulse signal word cpr1 at the instant of DC bypass and the trigger pulse signal word cpr2 before the DC bypass, and solve the converter valve with the lost pulse.

[0149] Specifically, determine the first logical AND result Vnum1, and the expression is as follows:

[0150] Vnum1 = cpr1 & cpr2; Equation (4)

[0151] where, & is the bitwise AND operator;

[0152] In the first logical AND result Vnum1, search from the low bit to the high bit in binary number form, obtain the position serial number of the first digit 1, and determine it as the number of the converter valve with the lost pulse. Specifically, for example, cpry1 = 48 = 0x110000, cpry2 = 24 = 0x011000, then Vnum1 = 16 = 0x010000, and the valve with the lost pulse is V5.

[0153] Step c.a.b: Determine that the conduction time of the maximum conduction phase in the three-phase current conduction phases is greater than 120° electrical angle. Based on the commutation sequence of the converter valve, determine the valve to be commutated by the converter valve corresponding to the maximum conduction phase as the converter valve with the lost pulse.

[0154] Among them, the steps to determine the maximum conduction phase in the three-phase current conduction phases include:

[0155] Accumulate the sampling points of the conduction phases until the second preset condition is not satisfied, obtain the conduction sampling points of each conduction phase, confirm the conduction time of the corresponding conduction phase based on the sampling points, and the phase with the maximum conduction time is the maximum conduction phase, and determine that the conduction time of the maximum conduction phase is greater than 120° electrical angle.

[0156] Among them, the conduction sequence of each phase in the three-phase current is V1, V2... V6, V1 in turn and circularly; the commutation sequence of the converter valve is that the three valves of the upper half bridge and the lower half bridge commutate pairwise with each other, that is, V1V3 commutation, V3V5 commutation, V5V1 commutation, V2V4 commutation, V4V6 commutation, V6V2 commutation, which is also circular commutation.

[0157] Step c.b: For the mis-triggered pulse fault, solve the mis-triggered converter valve:

[0158] Step c.b.a: In response to a mis-triggering fault, obtain the number combinations of the two bypass pairs of valves of the DC bypass instant conduction valve and the first pulse signal word after the DC power transmission system resumes commutation, and determine the number of the mis-triggered converter valve;

[0159] Based on the trigger pulse signal word cpr1 at the instant of DC bypass, obtain the number combination cprm of the two bypass pairs of valves of the conduction valve;

[0160] Obtain the first pulse signal word cprn after the DC power transmission system resumes commutation;

[0161] Based on the number combination cprm of the two bypass pairs of valves of the conduction valve at the instant of DC bypass and the first pulse signal word cprn after the DC power transmission system resumes commutation, determine the number of the mis-triggered converter valve:

[0162] Vnum2 = cprm ^ (cprm & cprn); Equation (5)

[0163] Wherein, Vnum2 is the second logical AND result. In the second logical AND result Vnum2, search from the low bit to the high bit in binary number form, obtain the position serial number of the first digit 1, and determine it as the number of the mis-triggered converter valve.

[0164] Specifically, record the trigger pulse signal word at the instant of DC bypass as cpr1. Through cpr1, the numbers of the two bypass pairs of valves of the conduction valve can be obtained, and their number combination is recorded as cprm. Then, according to Equations (2-1) to (2-6), obtain the first pulse signal word after the DC power transmission system resumes commutation, recorded as cprn. Then, the specifically mis-triggered converter valve can be obtained through Equation (5).

[0165] Step c.b.b: After the DC power transmission system resumes commutation, obtain the conduction time of the maximum conduction phase and confirm the mis-triggered converter valve;

[0166] After the DC power transmission system resumes commutation, calculate the AC current of each conduction phase in the DC power transmission system;

[0167] Solve for the conduction time of the maximum conduction phase based on the AC current of each conduction phase;

[0168] In response to the conduction time of the maximum conduction phase being greater than 120° electrical angle, the converter valve corresponding to the AC current of the maximum conduction phase is the mis-triggered converter valve.

[0169] The following is introduced with a specific case:

[0170] Case 1: Before diagnosis, it is not known whether the fault occurs in pole one or pole two, and whether it is in the Y-bridge or D-bridge. Therefore, the method of the present invention is used to diagnose the Y-bridges and D-bridges of pole one and pole two respectively. The information of the fault-free parts is omitted here, and only the information of the Y-bridge of pole two where the fault occurs is shown.

[0171] According to the commutation failure fault diagnosis method for the HVDC transmission system of the present invention, first obtain the valve-side current of the converter valve and the trigger pulse signal word, and the following two methods are respectively used for diagnosis:

[0172] Method 1: When calculating the moment of DC bypass according to Equation (1-1), please refer to Figure 6 the annotation. At this point, the CPRY value is cpry1 = 48, and its previous CPRY value is cpry2 = 24. The sampling points between them are continuous. Therefore, it is considered that the CPRY just changes at the moment of DC bypass, that is, commutation is in progress at the moment of DC bypass. Therefore, it is diagnosed as a lost pulse fault.

[0173] Method 2: Starting from the moment of DC bypass, calculate the maximum conduction time of the conducting phase according to Equations (2-1) to (2-6). It is obtained that phase C conducts for about 10 ms, corresponding to about 180° electrical angle, which is greater than 120° electrical angle (6.67 ms). Therefore, it is diagnosed as a lost pulse fault.

[0174] Next, use two methods to further locate the converter valve where the lost pulse fault specifically occurs:

[0175] Method A: According to Equation (4), the valve with the lost pulse can be obtained as: Vnum1 = cpry1 & cpry2 = 48 & 24 = 16 = 0x010000, that is, the valve with the lost pulse is V5 of the Y bridge.

[0176] Method B: Calculate that the conduction time of the negative current of phase B is greater than 120° according to Equations (2-1) to (2-6). The valve corresponding to the conduction of the negative current of phase B is V3. According to the commutation sequence, V3 will commutate with V5 next. Therefore, the valve with the lost pulse is V5 of the Y bridge.

[0177] The process of the lost pulse is as follows: The previous CPRY value cpry3 = 12, that is, when V3V4 (cpry3 = 12) -> V4V5 (cpry2 = 24), that is, when V3 -> V5, V5 loses the pulse, resulting in V5 not being turned on and V3 not being turned off; then next V4V5 (cpry2 = 24) -> V5V6 (cpry1 = 48), that is, after the commutation of V4 -> V6 is successful, V3 and V6 form a bypass pair.

[0178] Case 2: Before diagnosis, it is not known whether the fault occurs in pole 1 or pole 2, and whether it is in the Y bridge or the D bridge. Therefore, the method of the present invention is used to diagnose the Y bridge and D bridge of pole 1 and pole 2 respectively. The information of the fault-free part is omitted here, and only the information of the Y bridge of pole 1 where the fault occurs is shown.

[0179] According to the diagnosis method of the present invention, first obtain the valve-side current of the converter valve and the trigger pulse signal word, and the following two methods are respectively used for diagnosis:

[0180] Method 1: When calculating the moment of DC bypass according to Equation (1-1), please refer to Figure 7 As shown in the annotation, the CPRY value at this point is cpry1 = 3, and its previous CPRY value is cpry2 = 33. The sampling points between the two values differ by 7 points. Therefore, it is considered that the CPRY does not change at the moment of DC bypass, that is, the commutation does not occur at the moment of DC bypass, so it is diagnosed as a mis-triggering fault.

[0181] Method 2: Starting from the moment of DC bypass and moving forward, calculate the conduction time of the conducting phase according to Equation (3). It is obtained that the positive current phase C conducts for 1.4 ms, and the negative current phase A conducts for 4.8 ms, both of which are less than 120° electrical angle (6.67 ms). Therefore, it is diagnosed as a mis-triggering fault.

[0182] Next, use two methods to further locate the specific converter valve where the mis-triggering fault occurs:

[0183] Method A: According to cpry1 = 3 = 0x000011, the valves that were originally conducting before the fault are V1 and V2, then their bypass pair valves are V4 and V5, so cprym = 24. Then use (2-1) to (2-6) to find the first pulse signal word cpryn = 12 after the DC transmission system resumes commutation. Calculate the mis-triggered valve using Equation (5): Vnum2 = cprym ^ (cprym & cpryn) = 24 ^ (24 & 12) = 24 ^ 20 = 16 = 0x010000. Therefore, the mis-triggered valve is valve V5 of Y-bridge.

[0184] Method B: Calculate the current after the DC resumes commutation according to (2-1) to (2-6). It can be obtained that the conduction time of the negative current of phase C is about 10 ms, which is greater than 120°. The valve corresponding to the negative current of phase C is V5. Therefore, the mis-triggered valve is V5.

[0185] The mis-triggering process is as follows: When V1 and V2 are conducting, V5 is misapplied with a pulse, resulting in the mis-opening of V5. Then V2 and V5 form a DC bypass, and V1 is turned off. Next, the control system sends trigger pulses to V2 and V3, hoping that V1 commutates to V3. However, since V1 has already been turned off, the commutation is not completed, and it is still V2 and V5 in DC bypass. Next, the control system sends trigger pulses to V3 and V4, and the commutation from V2 to V4 is successful. Then the DC resumes the commutation process, and V4 and V5 are conducting, and AC two-phase current appears. Next, the control system sends trigger pulses to V4 and V5. Since V5 is already conducting, V4 and V5 continue to conduct. Later, the DC resumes normal operation.

[0186] In some embodiments, the present application further provides a commutation failure fault diagnosis device for a DC transmission system, including a processor and a memory. The memory stores computer programs executable by the processor, and when the processor executes the computer programs, the commutation failure fault diagnosis method provided by the present application is implemented.

[0187] In some embodiments, the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is run by a processor, the commutation failure fault diagnosis method provided by the present application is executed.

[0188] The above has introduced in detail a commutation failure fault diagnosis method, device, and storage medium provided by the embodiments of the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method for diagnosing commutation failure faults in a DC power transmission system, characterized in that, The DC transmission system includes a converter valve group and a converter valve triggering system. The AC side of the converter valve group is connected to a three-phase AC current, the DC side of the converter valve group is connected to a DC transmission line, and the converter valve triggering system is connected to the control end of the converter valve group to output a pulse signal word for phase commutation control of the converter valve group; The method includes: In response to detecting that the converter valve group is in a commutation state at the moment of DC bypass, it is determined that the converter valve triggering system has a lost pulse fault; In response to detecting that the converter valve group is not in a commutation state at the moment of DC bypass, it is determined that the converter valve triggering system has a mis-triggering fault; or, Within a preset time window before the moment of DC bypass, the following steps are performed: In response to detecting that the maximum conduction time among the conduction times of the conduction phases of the three-phase AC current is greater than 120° electrical angle, it is determined that the converter valve triggering system has the lost pulse fault; In response to detecting that the maximum conduction time among the conduction times of the conduction phases of the three-phase AC current is less than 120° electrical angle, it is determined that the converter valve triggering system has the mis-triggering fault.

2. The method for diagnosing commutation failure faults in a DC power transmission system according to claim 1, characterized in that, The method for determining the moment of DC bypass includes: Collect the three-phase AC current at a preset sampling point; The sampling moment corresponding to the first sampling point that satisfies the first preset condition is the moment of DC bypass, and the first preset condition is: MAX{ABS(IVY_L1),ABS(IVY_L2),ABS(IVY_L3)}<k1*ID_NOM; MAX{ABS(IVD_L1),ABS(IVD_L2),ABS(IVD_L3)}<k1*ID_NOM; Where, ABS is the absolute value, MAX is the maximum value operation; IVY_L1 is the valve-side current of phase A of the Y-bridge; IVY_L2 is the valve-side current of phase B of the Y-bridge; IVY_L3 is the valve-side current of phase C of the Y-bridge; IVD_L1 is the valve-side current of phase A of the D-bridge; IVD_L2 is the valve-side current of phase B of the D-bridge; IVD_L3 is the valve-side current of phase C of the D-bridge; k1 is the first proportionality coefficient; ID_NOM is the rated DC current of the DC transmission line.

3. The method for diagnosing commutation failure faults in a DC power transmission system according to claim 1, characterized in that, The method for determining whether the converter valve group is in a commutation state includes: Obtain a first pulse signal word and a second pulse signal word. The first pulse signal word is the pulse signal word at the moment of DC bypass, and the second pulse signal word is the first pulse signal word different from the first pulse signal word searched forward from the moment of DC bypass; The acquisition position of the first pulse signal word is the first position, and the acquisition position of the second pulse signal word is the second position; In response to detecting that both the first position and the second position are within the sampling points of two adjacent pulse signal words, it is determined that the converter valve group is in the commutation state, otherwise it is determined that the converter valve group is not in the commutation state.

4. The method for diagnosing commutation failure faults in a DC power transmission system according to claim 1, characterized in that, The step of, in response to detecting that the maximum conduction time among the conduction times of the conduction phases of the three-phase AC current is greater than 120° electrical angle, determining that the converter valve triggering system has a lost pulse fault includes: Obtain the conduction phase of the converter valve group based on the second preset condition; Accumulate the sampling points of the conducting phases until the second preset condition is not satisfied, obtain the conduction sampling points of each of the conducting phases, and confirm the conduction time corresponding to each of the conducting phases based on the sampling points. In response to the maximum conduction time in the conducting phases being greater than 120° electrical angle, it is determined that there is a missing pulse fault in the converter valve triggering system.

5. The method for diagnosing commutation failure faults in a DC power transmission system according to claim 4, characterized in that, The second preset condition includes: ABS(IVY_L1)>k2*ID_NOM; ABS(IVY_L2)>k2*ID_NOM; ABS(IVY_L3)>k2*ID_NOM; ABS(IVD_L1)>k2*ID_NOM; ABS(IVD_L2)>k2*ID_NOM; ABS(IVD_L3)>k2*ID_NOM; Wherein, ABS is the absolute value; IVY_L1 is the valve-side current of phase A of the Y-bridge; IVY_L2 is the valve-side current of phase B of the Y-bridge; IVY_L3 is the valve-side current of phase C of the Y-bridge; IVD_L1 is the valve-side current of phase A of the D-bridge; IVD_L2 is the valve-side current of phase B of the D-bridge; IVD_L3 is the valve-side current of phase C of the D-bridge; k2 is the second proportionality coefficient; ID_NOM is the rated DC current of the DC transmission line.

6. The method for diagnosing commutation failure faults in a DC power transmission system according to claim 4, characterized in that, The step of obtaining the conducting phases of the converter valve group based on the second preset condition includes: Collect the three-phase alternating current at a preset sampling point. Determine the phases for which the alternating current satisfies the second preset condition as the conducting phases.

7. The commutation failure fault diagnosis method for a DC transmission system according to claim 5, wherein The case where, in response to the maximum conduction time among the conduction times of the conducting phases of the three-phase current being less than 120° electrical angle, there is a mis-triggering fault in the converter valve triggering system includes: Obtain the conducting phases of the converter valve group based on the second preset condition. Accumulate the sampling points of the conducting phases that satisfy the third preset condition until the third preset condition is not satisfied, and obtain the conduction time of each conducting phase. In response to the conduction time of each conducting phase being less than 120° electrical angle, it is determined that there is a mis-triggering fault in the converter valve triggering system.

8. The commutation failure fault diagnosis method for a DC transmission system according to claim 7, wherein The third preset condition includes: IPOS>k3*ID_NOM; And INEG<-k3*ID_NOM; Wherein, IPOS is the conducting phase with a positive sampling value of the alternating current among the three phases; INEG is the conducting phase with a negative sampling value of the alternating current among the three phases; k3 is the third proportionality coefficient.

9. The commutation failure fault diagnosis method for a DC transmission system according to claim 1, wherein The method for diagnosing commutation failure faults in the DC transmission system further includes: In response to a missing pulse fault, obtain the trigger pulse signal word cpr1 at the moment of DC bypass and the trigger pulse signal word cpr2 of the previous trigger pulse before DC bypass. The converter valve for solving the missing pulse includes: Determine the first logical AND result Vnum1, and the expression is as follows: Vnum1 = cpr1&cpr2; Wherein, & is the bitwise AND operator; In the first logical AND result Vnum1, search from the low bit to the high bit in binary number form, obtain the position serial number of the first digit 1, and determine it as the number of the converter valve with the missing pulse.

10. The commutation failure fault diagnosis method for a DC transmission system according to claim 1, wherein The method for diagnosing commutation failure faults in the DC transmission system further includes: Determine the phase with the maximum conduction time among the conducting phases of the three-phase current as the maximum conducting phase. In response to the conduction time of the maximum conduction phase being greater than 120° electrical angle, based on the commutation sequence of the commutation valve, the valve that commutates the commutation valve corresponding to the maximum conduction phase is determined as the commutation valve with a lost pulse.

11. The commutation failure fault diagnosis method for a DC transmission system according to claim 1, wherein The commutation failure fault diagnosis method for the DC power transmission system further includes: In response to a mis-triggering fault, obtain the trigger pulse signal word cpr1 at the instant of DC bypass; Based on the trigger pulse signal word cpr1 at the instant of DC bypass, obtain the number combination cprm of the two bypass pair valves of the conducting valve; Obtain the first pulse signal word cprn after the DC power transmission system resumes commutation; Based on the number combination cprm of the two bypass pair valves of the conducting valve at the instant of DC bypass and the first pulse signal word cprn after the DC power transmission system resumes commutation, determine the number of the mis-triggered commutation valve: Vnum2 = cprm ^ (cprm & cprn); Wherein, Vnum2 is the second logical AND result; In the second logical AND result Vnum2, search from the low bit to the high bit in binary number form, obtain the position serial number of the first digit 1, and determine it as the number of the mis-triggered commutation valve.

12. The commutation failure fault diagnosis method for a DC transmission system according to claim 1, wherein The commutation failure fault diagnosis method for the DC power transmission system further includes: After the DC power transmission system resumes commutation, calculate the AC current of each conducting phase in the DC power transmission system; Solve the conduction time of the maximum conduction phase based on the AC current of each conducting phase; In response to the conduction time of the maximum conduction phase being greater than 120° electrical angle, the commutation valve corresponding to the AC current of the maximum conduction phase is the mis-triggered commutation valve.

13. The commutation failure fault diagnosis method for a DC power transmission system according to claim 1, wherein The value range of the preset time window is 0 - 1 cycle.

14. The commutation failure fault diagnosis method for a DC power transmission system according to claim 2, wherein The value range of the first proportionality coefficient is 0 - 0.

1.

15. The commutation failure fault diagnosis method for a DC power transmission system according to claim 5, wherein The value range of the second proportionality coefficient is 0 - 0.

1.

16. The commutation failure fault diagnosis method for a DC power transmission system according to claim 8, wherein The value range of the third proportionality coefficient is 0 - 0.

1.

17. A commutation failure fault diagnosis device for a DC power transmission system, wherein It includes a processor and a memory, the memory stores a computer program executable by the processor, and when the processor executes the computer program, it implements the commutation failure fault diagnosis method for the DC power transmission system according to any one of claims 1 - 16.

18. A computer-readable storage medium, wherein A computer program is stored on this computer-readable storage medium, and when the computer program is run by a processor, it executes the commutation failure fault diagnosis method for the DC power transmission system according to any one of claims 1 - 16.

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