A method, system, device and terminal for detecting faults in a flexible direct current transmission system

Abstract

The present invention belongs to the technical field of direct current transmission, and discloses a method, system, device and terminal for detecting faults in a flexible direct current transmission system, which analyzes the inductance change characteristics of a direct current limiter; sets fault detection parameters according to the inductance change characteristics of the direct current limiter; detects the voltage change rate at both ends of the direct current limiter, and compares the voltage change rate at both ends of the direct current limiter with the fault detection parameters, thereby realizing fault judgment. The method for detecting faults in a flexible direct current transmission system considering a direct current limiter provided by the present invention fully considers the influence of the inductance change of the direct current limiter on the fault characteristics of the transmission line, sets fault judgment parameters, and considers the inductance change characteristics of the direct current limiter, and uses the voltage change rate at both ends of the direct current limiter for fault judgment. At the same time, the method for detecting faults in a flexible direct current transmission system considering a direct current limiter provided by the present invention has a fast fault detection speed, high sensitivity and reliability, and can accurately distinguish faults within and outside the area.

Description

Technical Field

[0001] The present invention belongs to the technical field of direct current transmission, and in particular relates to a flexible direct current transmission system fault detection method, system, equipment and terminal. Background Art

[0002] With the development of economy and society, flexible direct current transmission will be widely used in power systems. However, when a bipolar short circuit fault occurs in the DC system, the fault current rises too fast, which will pose a serious threat to the safe and stable operation of the system.

[0003] The patent [A high-voltage DC system fault current limiter and method based on saturated iron core, CN201810678531.4] proposes a DC current limiter that can effectively suppress the fault current limit rise rate. When the system is operating normally, the current limiter core is in a saturated state, the inductance value is small, and it can replace the smoothing reactor; when a short-circuit fault occurs in the system, the current limiter core desaturates and the inductance value increases rapidly, thereby limiting the fault current rise rate and ensuring that the DC circuit breaker can operate reliably.

[0004] However, the change of the inductance of the DC current limiter will change the fault characteristics of the transmission line. The detection of short-circuit faults in the DC transmission system will be affected by the DC current limiter, resulting in a slow detection speed, insufficient sensitivity and reliability, and inability to accurately distinguish between internal and external faults. At present, there is still a lack of solutions to this problem at home and abroad. Therefore, it is urgent to design a new fault detection method for flexible DC transmission systems.

[0005] Through the above analysis, the problems and defects of the existing technology are as follows: for the flexible DC transmission system containing DC current limiter, the existing fault detection method has a slow detection speed, insufficient sensitivity and reliability, and cannot accurately distinguish between faults inside and outside the area, and cannot meet the actual needs of the project.

[0006] The significance of solving the above problems and defects is: it provides a technical approach for fault detection of flexible DC transmission systems containing DC current limiters, can quickly and accurately identify faults within and outside the area, and solves some technical problems in commissioning DC current limiters. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a method, system, device and terminal for detecting faults in a flexible direct current transmission system, and in particular, relates to a method, system, medium, device and terminal for detecting faults in a flexible direct current transmission system taking into account a direct current limiter.

[0008] The present invention is implemented as follows: a method for detecting faults in a flexible direct current power transmission system, the method comprising:

[0009] Analyze the inductance change characteristics of the current limiter and set the fault detection parameters according to the inductance change characteristics; monitor the voltage across the DC current limiter and record the fault judgment parameters, compare them with the relevant fault detection parameters, and make a fault judgment.

[0010] Furthermore, the fault judgment parameters also include:

[0011] Voltage U across the DC current limiter FCL , rise time interval Δt.

[0012] Furthermore, the fault detection parameters also include:

[0013] Initial threshold vt1, protection threshold vt2, rise time setting value Δt set , maintenance time Δt mt .

[0014] Furthermore, the flexible direct current transmission system fault detection method further comprises:

[0015] Analyze the inductance variation characteristics of the DC current limiter; calculate the voltage across the DC current limiter; determine the fault detection parameters; record the rising time interval Δt; determine whether Δt is less than Δt set ; If Δt is not less than Δt set , then return to the step of recording the rising time interval Δt; if Δt is less than Δt set , then judge the subsequent Δt mt During this period, U FCL Is it greater than vt2? FCL If U is not greater than vt2, return to the step of recording the rising time interval Δt; FCL If it is greater than vt2, the protection action is executed.

[0016] Furthermore, the flexible direct current transmission system fault detection method comprises the following steps:

[0017] Step 1: According to the inductance change characteristics of the DC current limiter, set the initial threshold vt1, protection threshold vt2, and rise time setting value Δt set and the holding time Δt mt ;

[0018] Step 2, measuring the voltage across the DC current limiter, and recording the rising time interval Δt of the voltage across the current limiter from vt1 to vt2;

[0019] Step 3: If Δt is less than the set value Δt set , then go to step 4; otherwise, return to step 2;

[0020] Step 4: Continue to measure the voltage across the current limiter. If the subsequent maintenance time Δt mtIf the voltage across the current limiter is always greater than the protection threshold vt2 during the time period, the protection action is triggered; otherwise, the protection does not take effect and returns to step 2.

[0021] Furthermore, in step 1, the initial threshold vt1, the protection threshold vt2, and the rise time setting value Δt are set according to the inductance change characteristics of the DC current limiter. set and the holding time Δt mt include:

[0022] (1) A two-stage model is used to equate the inductance change of the DC current limiter;

[0023] (2) Calculate the theoretical value of the voltage across the DC current limiter;

[0024] (3) According to the voltage across the DC current limiter obtained in step (1), set the initial threshold vt1, protection threshold vt2, and rise time setting value Δt set and the holding time Δt mt .

[0025] Furthermore, the equivalent formula for the inductance change of the DC current limiter using the two-stage model in step (1) is:

[0026]

[0027] Among them, L s is the saturated inductance of the DC current limiter, L u is the desaturated inductance of the DC current limiter, R s is the saturation magnetic resistance of the DC current limiter core, R u is the desaturated magnetic resistance of the DC current limiter core, R m is the reluctance of the permanent magnet.

[0028] Further, the theoretical value U of the voltage across the DC current limiter calculated in step (2) is tc The formula is:

[0029] U tc =L FCL [(AB)C1e (A-B)t +(A+B)C2e (A+B)t ];

[0030] Among them, C1 and C2 are the initial fault state coefficients, and A and B are the DC system characterization coefficients.

[0031] Another object of the present invention is to provide a flexible direct current transmission system fault detection system applying the flexible direct current transmission system fault detection method, the flexible direct current transmission system fault detection system comprising:

[0032] Current limiter analysis module, used to analyze the inductance variation characteristics of the DC current limiter;

[0033] A parameter setting module, used to set fault detection parameters according to the inductance variation characteristics;

[0034] The fault detection module is used to detect the voltage change rate at both ends of the DC current limiter, and compare the voltage change rate at both ends of the DC current limiter with the fault detection parameter to realize fault judgment.

[0035] Another object of the present invention is to provide a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the flexible direct current transmission system fault detection method.

[0036] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the flexible direct current transmission system fault detection method.

[0037] Another object of the present invention is to provide an information data processing terminal, wherein the information data processing terminal is used to implement the flexible direct current transmission system fault detection system.

[0038] In combination with the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solutions to be protected by the present invention from the following aspects:

[0039] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving the problems, the technical solutions to be protected by the present invention and the results and data during the research and development process are closely combined to analyze in detail and deeply how the technical solutions of the present invention solve the technical problems, and some creative technical effects brought about after solving the problems. The specific description is as follows:

[0040] Aiming at the influence of DC current limiter on DC system fault detection, the present invention proposes a flexible DC power transmission system fault detection method considering DC current limiter, by analyzing the inductance change characteristics of the current limiter and setting the fault detection parameters accordingly; detecting the voltage change rate at both ends of the DC current limiter and comparing it with the fault detection parameters to make a fault judgment. The flexible DC power transmission system fault detection method considering DC current limiter provided by the present invention has fast detection speed, high sensitivity and reliability, and can accurately distinguish between faults within and outside the area.

[0041] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0042] The present invention provides a flexible direct current transmission system fault detection method considering a direct current limiter, which fully considers the influence of the inductance change of the direct current limiter on the fault characteristics of the transmission line, sets fault judgment parameters, considers the inductance change characteristics of the direct current limiter, and uses the voltage change rate at both ends of the direct current limiter to perform fault judgment. The detection method is simple to implement, has a good detection effect, and can meet the actual needs of the project.

[0043] Third, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0044] The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0045] With respect to the research on fault detection methods for DC current limiters at home and abroad, the detection method provided by the present invention fills the gap in this aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0047] Figure 1 is a flow chart of a fault detection method for a flexible direct current transmission system provided by an embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of a fault detection method for a flexible direct current transmission system provided by an embodiment of the present invention;

[0049] Figure 3 is a structural schematic diagram of a DC current limiter provided in an embodiment of the present invention;

[0050] Figure 4 It is a waveform diagram of a simulated protection trigger signal according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] In view of the problems existing in the prior art, the present invention provides a method, system, device and terminal for detecting faults in a flexible direct current transmission system. The present invention is described in detail below with reference to the accompanying drawings.

[0053] like Figure 1As shown, the flexible direct current transmission system fault detection method provided by the embodiment of the present invention comprises the following steps:

[0054] S101, analyzing the inductance variation characteristics of the DC current limiter;

[0055] S102, setting fault detection parameters according to the inductance variation characteristics of the DC current limiter;

[0056] S103, detecting a voltage change rate at both ends of the DC current limiter, and comparing the voltage change rate at both ends of the DC current limiter with a fault detection parameter, thereby realizing fault judgment.

[0057] As a preferred embodiment, Figure 2 As shown, the flexible direct current transmission system fault detection method provided by the embodiment of the present invention specifically includes the following steps:

[0058] Step 1: According to the inductance change characteristics of the DC current limiter, set the initial threshold vt1, protection threshold vt2, and rise time setting value Δt set , maintenance time Δt mt ;

[0059] Step 2: Observe the current across the DC current limiter and record the time interval Δt for the voltage across the current limiter to rise from vt1 to vt2;

[0060] Step 3: If Δt is less than the set value Δt set , then go to step 4; otherwise, return to step 2;

[0061] Step 4: Continuously monitor the voltage across the current limiter. If it is maintained for time Δt mt If the voltage across the internal current limiter is always greater than the protection threshold vt2, the protection action is triggered; otherwise, the protection does not take effect and returns to step 2.

[0062] In the above-mentioned flexible DC transmission system fault detection method considering the DC current limiter, the implementation of step 1 includes:

[0063] Step 1.1: Use a two-stage model to equate the inductance change of the DC current limiter. The inductance L of the DC current limiter is FCL As shown in formula (1);

[0064]

[0065] Among them, L s is the saturated inductance of the DC current limiter, L u is the desaturated inductance of the DC current limiter, R s is the saturation magnetic resistance of the DC current limiter core, R u is the desaturated magnetic resistance of the DC current limiter core, R mis the magnetic reluctance of the permanent magnet. N1 is the number of turns of the coil winding.

[0066] Step 1.2: Calculate the voltage across the DC current limiter, as shown in equation (2):

[0067] U FCL =L FCL [(AB)C1e (A-B)t +(A+B)C2e (A+B)t ](2)

[0068] Among them, C1 and C2 are the initial state coefficients of the fault, A and B are the DC system characterization coefficients, and t is the time.

[0069] Step 1.3: According to the voltage across the DC current limiter obtained in step 1.2, set the initial threshold vt1, protection threshold vt2, and rise time setting value Δt set , maintenance time Δt mt .

[0070] The flexible direct current transmission system fault detection system provided by the embodiment of the present invention comprises:

[0071] Current limiter analysis module, used to analyze the inductance variation characteristics of the DC current limiter;

[0072] A parameter setting module, used to set fault detection parameters according to the inductance variation characteristics;

[0073] The fault detection module is used to detect the voltage change rate at both ends of the DC current limiter, and compare the voltage change rate at both ends of the DC current limiter with the fault detection parameter to realize fault judgment.

[0074] The embodiment of the present invention establishes a dual-port ±100kV DC transmission system simulation model, the transmission line length is 75km, and faults are set at 0km, 37.5km, and 75km at 10s. The flexible DC transmission system fault detection method considering the DC current limiter is implemented by the following technical scheme, including the following steps:

[0075] (1) A two-stage model is used to equate the inductance change of the DC current limiter. The schematic diagram of the DC current limiter is shown in Figure 3 The change of the inductance of the DC current limiter is shown in formula (1);

[0076]

[0077] Among them, L s is the saturated inductance of the DC current limiter, L u is the desaturated inductance of the DC current limiter, R s is the saturation magnetic resistance of the DC current limiter core, R u is the desaturated magnetic resistance of the DC current limiter core, Rm is the reluctance of the permanent magnet.

[0078] Calculate the voltage across the DC current limiter as shown in formula (2):

[0079] U FCL =L FCL [(AB)C1e (A-B)t +(A+B)C2e (A+B)t ](2)

[0080] Among them, C1 and C2 are the initial fault state coefficients, and A and B are the DC system characterization coefficients.

[0081] According to the voltage across the DC current limiter obtained by formula (2), the initial threshold vt1, protection threshold vt2, and rise time setting value Δt set , maintenance time Δt mt .

[0082] In the embodiment of the present invention, the initial threshold vt1 is selected as 5kV, the protection threshold vt2 is selected as 10kV, and the rise time setting value Δt set 100μs, holding time Δt mt is 20μs.

[0083] (2) Observe the current across the DC current limiter and record the time interval Δt for the voltage across the current limiter to rise from vt1 to vt2;

[0084] (3) If Δt is less than the set value Δt set , then go to step 4; otherwise, return to step 2;

[0085] (4) Continuously monitor the voltage across the current limiter. If the voltage is maintained for a period of time Δt mt If the voltage across the internal current limiter is always greater than the protection threshold vt2, the protection action is triggered; otherwise, the protection does not take effect and returns to step (2).

[0086] Through the above steps, the protection trigger signal waveform can be obtained as follows: Figure 4 shown.

[0087] Obviously, the detection method provided by the present invention can accurately identify faults within 300 μs.

[0088] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0089] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for detecting faults in a flexible direct current transmission system, characterized in that: The flexible direct current transmission system fault detection method comprises: Analyze the inductance change characteristics of the current limiter and set the fault detection parameters according to the inductance change characteristics; detect the voltage change rate at both ends of the DC current limiter and compare it with the fault detection parameters to make a fault judgment; The flexible direct current transmission system fault detection method further comprises: Analyze the inductance variation characteristics of the DC current limiter; calculate the voltage across the DC current limiter; determine the fault detection parameters; record the time interval Δt; determine whether Δt is less than Δt set ; If Δt is not less than Δt set , then return to the step of recording the time interval Δt; if Δt is less than Δt set , then judge Δt mt Within, whether UFCL is greater than vt2; if UFCL is not greater than vt2, return to the step of recording the time interval Δt; if UFCL is greater than vt2, perform the protection action; The flexible direct current transmission system fault detection method comprises the following steps: Step 1: According to the inductance change characteristics of the DC current limiter, set the initial threshold vt1, protection threshold vt2, and rise time setting value Δt set and the holding time Δt mt ; Step 2, observe the current at both ends of the DC current limiter, and record the time interval Δt for the voltage at both ends of the current limiter to rise from vt1 to vt2; Step 3: If Δt is less than the set value Δt set , then go to step 4; otherwise, return to step 2; Step 4: Continuously monitor the voltage across the current limiter. If the voltage is maintained for a period of time Δt mt If the voltage across the internal current limiter is always greater than the protection threshold vt2, the protection action is triggered; otherwise, the protection does not take effect and returns to step 2; In step 1, the initial threshold vt1, the protection threshold vt2, and the rise time setting value Δt are set according to the inductance change characteristics of the DC current limiter. set and the holding time Δt mt include: (1) A two-stage model is used to equate the inductance change of the DC current limiter; (2) Calculate the voltage across the DC current limiter; (3) According to the voltage across the DC current limiter obtained in step (1), set the initial threshold vt1, protection threshold vt2, and rise time setting value Δt set and the holding time Δt mt .

2. The method for detecting faults in a flexible direct current transmission system according to claim 1, characterized in that: The formula for equivalently calculating the inductance change of the DC current limiter using the two-stage model in step (1) is: Among them, L s is the saturated inductance of the DC current limiter, L u is the desaturated inductance of the DC current limiter, R s is the saturation magnetic resistance of the DC current limiter core, R u is the desaturated magnetic resistance of the DC current limiter core, R m is the reluctance of the permanent magnet.

3. The fault detection method for a flexible direct current transmission system according to claim 1, characterized in that: The formula for calculating the voltage across the DC current limiter in step (2) is: U FCL =L FCL [(A-B)C1e (A-B)t +(A+B)C2e (A+B)t ]; Among them, C1 and C2 are the initial fault state coefficients, and A and B are the DC system characterization coefficients.

4. A flexible direct current transmission system fault detection system using the flexible direct current transmission system fault detection method according to any one of claims 1 to 3, characterized in that: The flexible direct current transmission system fault detection system comprises: Current limiter analysis module, used to analyze the inductance variation characteristics of the DC current limiter; A parameter setting module, used to set fault detection parameters according to the inductance variation characteristics; The fault detection module is used to detect the voltage change rate at both ends of the DC current limiter, and compare the voltage change rate at both ends of the DC current limiter with the fault detection parameter to realize fault judgment.

5. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the flexible direct current transmission system fault detection method according to any one of claims 1 to 3.

6. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the method for detecting faults in a flexible direct current transmission system according to any one of claims 1 to 3.

7. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the flexible direct current transmission system fault detection system as claimed in claim 4.

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