Method and device for determining working voltage in neutral point ungrounded system

Abstract

The application provides a method and device for determining working voltage in a neutral point ungrounded system. The power system comprises three-phase lines and three capacitor banks. One end of each capacitor bank is connected to a phase circuit, and the other end is connected to each other to form a neutral point. The capacitor bank comprises a plurality of capacitors. The method comprises: periodically sampling the phase voltage of each phase line to obtain a plurality of groups of real-time phase voltage sampling values, each group of real-time phase voltage sampling values comprising the sampling value of the phase voltage of each phase line obtained by simultaneously measuring each phase line; determining the imbalance rate between the capacitor banks based on the plurality of groups of real-time phase voltage sampling values, the imbalance rate being the ratio of the capacitance values between each two phase lines; and determining the working voltage of the neutral point ungrounded system according to the imbalance rate. The imbalance rate between the capacitor banks is obtained through the real-time measurement of the phase voltage sampling value, and the accurate working voltage is determined according to the imbalance rate, so that subsequent operations can be accurately performed.

Description

Technical Field

[0001] This invention relates to the field of power systems, and in particular to a method and apparatus for determining the operating voltage in a neutral-point ungrounded system. Background Technology

[0002] A neutral-point ungrounded system refers to a three-phase AC power grid where the neutral point is not electrically connected to the ground; that is, the neutral point is not artificially connected to the ground. For example... Figure 1 The diagram shows a structural schematic of a neutral-point ungrounded system. The system includes three-phase lines (A, B, and C) and three capacitor banks: capacitor bank 14 (A-phase), capacitor bank 15 (B-phase), and capacitor bank 16 (C-phase). One end of each capacitor bank is connected to one phase circuit, and the other ends are interconnected to form a neutral point 101. Each capacitor bank contains multiple capacitors connected in series and / or parallel. The system assumes that the capacitance values ​​of each capacitor bank are equal, i.e., at phase C... A =C B =C C In this case, the sampled values ​​of the phase voltage on each phase line are equal, where C A C represents the capacitance value on phase A. B Indicates the capacitance value on phase B, C C I represents the capacitance value on phase C. A Let I be the current in phase A of the circuit. B For the current in phase B line, I C This represents the current in phase C. At this time, the operating voltage of this ungrounded neutral system is 0.

[0003] However, in actual use, due to manufacturing errors or the breakdown of small internal capacitors, the capacitance value of the capacitors cannot be exactly the same as the preset value, and it is also not easy to measure the capacitance value of each capacitor. This may lead to the operating voltage of the ungrounded neutral point system exceeding the preset threshold even when no fault has occurred, which in turn may cause the relay protection device corresponding to the capacitor bank to malfunction. Summary of the Invention

[0004] In view of this, the present invention proposes a method for determining the operating voltage in a neutral-point ungrounded power system. The power system includes three-phase lines and three capacitor banks. One end of each capacitor bank is connected to one phase circuit, and the other ends are interconnected to form a neutral point. Each capacitor bank includes multiple capacitors. The determination method includes:

[0005] The phase voltage of each phase line is periodically sampled to obtain multiple sets of real-time phase voltage sample values. Each set of real-time phase voltage sample values ​​includes the phase voltage sample values ​​of each phase line obtained by simultaneously measuring each phase line.

[0006] determining an unbalance rate between the capacitor groups based on the sample values of the real-time phase voltages, the unbalance rate being a ratio of capacitance values between each two-phase line;

[0007] determining an operating voltage of the neutral non-grounded system according to the unbalance rate.

[0008] According to the determination method as described above, optionally, determining the unbalance rate between the capacitor groups based on the sample values of the real-time phase voltages comprises:

[0009] determining the unbalance rate K between the capacitor groups based on the following formula AB and K AC :

[0010] R=(X′X) -1 X′Y,

[0011] wherein, x 1n represents x1, x 2n represents x2, y n represents y obtained through the nth measurement, x1=(V X -V B ), x2=(V X -V C ), y=V A -V X ,

[0012] V X represents a sample value of the zero sequence voltage of the neutral point, V A represents a sample value of the phase voltage of the A-phase line,

[0013] V B represents a sample value of the phase voltage of the B-phase line, V C represents a sample value of the phase voltage of the C-phase line,

[0014] C A represents a capacitance value of the A-phase line, C B represents a capacitance value of the B-phase line, C C represents a capacitance value of the C-phase line.

[0015] According to the determination method as described above, optionally, the operating voltage is

[0016] wherein

[0017] V0=(V A +V B +VC ) / 3.

[0018] According to the determination method, optionally, the number of groups of the sampling values of the real-time phase voltages is 2-10 groups.

[0019] According to the determination method, optionally, after determining the working voltage of the neutral point ungrounded system according to the imbalance rate, the method further comprises:

[0020] If it is identified that the neutral point ungrounded system has a fault, it is determined according to the working voltage whether the fault is an internal fault, the internal fault indicating that a capacitor in the capacitor bank has a fault.

[0021] Determining according to the working voltage whether the fault is an internal fault comprises:

[0022] If the value of the working voltage is greater than or equal to a preset threshold, it is determined that the fault is an internal fault.

[0023] The application further provides a determination device of a working voltage of a neutral point ungrounded system, the power system comprising three-phase lines and three capacitor banks, one end of each capacitor bank being connected to a phase circuit, and the other end being connected to each other to form a neutral point, the capacitor bank comprising a plurality of capacitors, the determination device comprising:

[0024] a sampling unit configured to periodically sample phase voltages of the phase circuits to obtain a plurality of groups of sampling values of real-time phase voltages, each group of the sampling values of the real-time phase voltages comprising sampling values of the phase voltages of the phase circuits obtained by simultaneously measuring the phase circuits;

[0025] a first determination unit configured to determine an imbalance rate between the capacitor banks based on the plurality of groups of the sampling values of the real-time phase voltages, the imbalance rate being a ratio of capacitance values between each two phase circuits;

[0026] a second determination unit configured to determine the working voltage of the neutral point ungrounded system according to the imbalance rate.

[0027] According to the determination device, optionally, the first determination unit is specifically configured to:

[0028] determine the imbalance rate K between the capacitor banks based on the following formula AB and K AC :

[0029] R=(X′X) -1 X′Y,

[0030] wherein, x 1n x1, x2, …, xn represent x1, x2, …, xn obtained by the nth measurement.2n represents x2, y obtained by the n-th measurement n represents y obtained by the n-th measurement, x1=(V X -V B ), x2=(V X -V C ), y=V A -V X ,

[0031] V X represents a sampling value of the zero sequence voltage of the neutral point, V A represents a sampling value of the phase voltage of the A-phase line,

[0032] V B represents a sampling value of the phase voltage of the B-phase line, V C represents a sampling value of the phase voltage of the C-phase line,

[0033] C A represents a capacitance value of the A-phase line, C B represents a capacitance value of the B-phase line, C C represents a capacitance value of the C-phase line.

[0034] According to the determination device as described above, optionally, the working voltage is

[0035] wherein

[0036] V0=(V A +V B +V C ) / 3.

[0037] According to the determination device as described above, optionally, the number of groups of the sampling values of the real-time phase voltage is 2-10 groups.

[0038] According to the determination device as described above, optionally, further comprising:

[0039] a third determination unit, configured to determine whether the fault is an internal fault according to the working voltage if it is identified that the neutral point ungrounded system is faulty, wherein the internal fault represents that a capacitor in the capacitor bank is faulty;

[0040] determining whether the fault is an internal fault according to the working voltage comprises:

[0041] if the value of the working voltage is greater than or equal to a preset threshold value, it is determined that the fault is an internal fault.

[0042] The application further provides a device for determining the working voltage in a neutral point ungrounded system, the power system comprising three-phase lines and three capacitor banks, one end of each capacitor bank being connected to a phase circuit, and the other end being connected to each other to form a neutral point, the capacitor banks comprising a plurality of capacitors, the device comprising:

[0043] at least one memory for storing instructions;

[0044] at least one processor for executing the instructions stored in the memory to perform the method for determining the working voltage in a neutral point ungrounded system according to any one of the above.

[0045] The application further provides a readable storage medium, the readable storage medium storing machine readable instructions, the machine readable instructions being executed by a machine to perform the method for determining the working voltage in a neutral point ungrounded system according to any one of the above.

[0046] The imbalance rate between the capacitor banks is obtained by the sampling value of the real-time measured phase voltage, and the accurate working voltage is determined according to the imbalance rate, so that the subsequent operation can be accurately performed. BRIEF DESCRIPTION OF DRAWINGS

[0047] The preferred embodiments of the application will be described in detail below with reference to the accompanying drawings, so that the above and other features and advantages of the application can be more clearly understood by those skilled in the art, in which:

[0048] Figure 1 It is a structural schematic diagram of a neutral point ungrounded system according to an embodiment of the application.

[0049] Figure 2 It is a flowchart of a method for determining the working voltage in a neutral point ungrounded system according to another embodiment of the application.

[0050] Figure 3 It is a flowchart of a method for determining the working voltage in a neutral point ungrounded system according to another embodiment of the application.

[0051] Figure 4A It is a structural schematic diagram of a device for determining the working voltage in a neutral point ungrounded system according to an embodiment of the application.

[0052] Figure 4B It is a structural schematic diagram of a device for determining the working voltage in a neutral point ungrounded system according to another embodiment of the application. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the application more clear, the application will be further described in detail below with examples.

[0054] For ungrounded neutral systems, faults can be categorized into internal and external faults. Internal faults indicate a problem within the capacitor bank of the ungrounded neutral system, such as a ground fault or capacitor breakdown. External faults indicate a problem not caused by a capacitor failure, but by a fault in equipment outside the protection range of the relay protection device corresponding to the capacitor bank. In the event of an external fault, the relay protection device corresponding to the capacitor bank should not activate. Whether the relay protection device activates can be determined by whether the operating voltage exceeds a preset threshold. If the operating voltage is greater than or equal to the preset threshold, protection should be activated; otherwise, it should not activate. Therefore, the accuracy of the operating voltage plays a crucial role. The inventors discovered that the operating voltage is related to the ratio between capacitor banks. Based on this, the inventors provide a method for determining the ratio between capacitor banks, thereby obtaining an accurate operating voltage.

[0055] Example 1

[0056] This embodiment provides a method for determining the operating voltage in a neutral-point ungrounded system. The method is executed by a device for determining the operating voltage in a neutral-point ungrounded system. This device can be integrated into a relay protection device or set up separately.

[0057] like Figure 2 The diagram shown is a flowchart illustrating the method for determining the operating voltage in a neutral-point ungrounded system according to this embodiment. The method for determining the operating voltage in this neutral-point ungrounded system includes:

[0058] Step 201: Periodically sample the phase voltage of each phase line to obtain multiple sets of real-time phase voltage sampling values. Each set of real-time phase voltage sampling values ​​includes the phase voltage sampling values ​​of each phase line obtained by simultaneously measuring each phase line.

[0059] The phase voltage of each phase is sampled continuously and periodically. This period can be set according to actual needs, for example, once every 1 millisecond. Furthermore, sampling of each phase circuit is performed simultaneously. Specifically, the phase voltage sampling values ​​can be obtained using voltage sensors.

[0060] The number of sampling values ​​for real-time phase voltage can be 2-10 sets. This provides sufficient data for determining the accurate operating voltage and allows the operating voltage to be determined as quickly as possible.

[0061] Step 202: Determine the unbalance rate between capacitor banks based on the sampled values ​​of multiple sets of real-time phase voltages. The unbalance rate is the ratio of the capacitance values ​​between each pair of phase lines.

[0062] Due to process errors and other reasons, the capacitance values of each capacitor bank cannot be completely equal, and it is very difficult to obtain the capacitance value of each capacitor in each capacitor bank through measurement. The inventor adopts the way of determining the ratio of the capacitance values between capacitor banks based on the sampling value of real-time phase voltage to determine the working voltage with higher accuracy.

[0063] For example, the unbalance rate K between capacitor banks is determined based on the following formula AB and K AC :

[0064] R=(X′X) -1 X′Y,

[0065] wherein, x 1n represents x1, x 2n represents x2, y n obtained through the nth measurement, x1=(V X -V B ), x2=(V X -V C ), y=V A -V X ,

[0066] V X represents the sampling value of zero sequence voltage of the neutral point, V A represents the sampling value of phase voltage of the A-phase line,

[0067] V B represents the sampling value of phase voltage of the B-phase line, V C represents the sampling value of phase voltage of the C-phase line,

[0068] C A represents the capacitance value of the A-phase line, C B represents the capacitance value of the B-phase line, C C represents the capacitance value of the C-phase line.

[0069] Step 203, determining the working voltage of the neutral point ungrounded system according to the unbalance rate.

[0070] The working voltage can be defined according to needs, for example, configured according to the corresponding relay protection device.

[0071] In the present application, the working voltage is, for example, |V X (1+K AB +K AC )-3V0+V B (1-K AB )+VC (1-K AC ), wherein, wherein V0= (V A + V B + V C ) / 3, C A represents the capacitance value of the A-phase line, C B represents the capacitance value of the B-phase line, C C represents the capacitance value of the C-phase line.

[0072] Optionally, after step 203, the method further comprises: returning to step 201 for periodic repetition, so as to realize continuous determination of the sampling value of the phase voltage. In the embodiment, the staff can trigger step 201 according to actual needs, or the device can periodically execute steps 201 to 203 to realize automatic determination of the working voltage.

[0073] Optionally, after step 203, the method further comprises: if it is identified that the neutral point ungrounded system has a fault, determining whether the fault is an internal fault according to the working voltage, the internal fault indicating that a capacitor in the capacitor bank has a fault. If it is determined that the fault is an internal fault, the relay protection device corresponding to the capacitor bank should act to remove the fault, and if it is determined that the fault is a non-internal fault, i.e., an external fault, the relay protection device corresponding to the capacitor bank should not act. As an exemplary illustration, if the value of the working voltage is less than a preset threshold, it is determined that the fault is an external fault, and if the value of the working voltage is greater than or equal to the preset threshold, it is determined that the fault is an internal fault. The preset threshold can be determined according to actual needs, and will not be described here.

[0074] The embodiment obtains the unbalance rate between the capacitor banks by the sampling value of the phase voltage measured in real time, and then determines the accurate working voltage according to the unbalance rate, so that subsequent operations can be accurately performed.

[0075] Embodiment Two

[0076] The embodiment further supplements the method for determining the working voltage in the neutral point ungrounded system of embodiment one. As shown in the flowchart of the method for determining the working voltage in the neutral point ungrounded system according to the embodiment. Figure 3 The method for determining the working voltage in the neutral point ungrounded system comprises:

[0077] Step 301: periodically sampling the sampling value of the phase voltage of each phase line to obtain a plurality of groups of real-time phase voltage sampling values under the condition that it is determined that the capacitor bank has a fault, each group of real-time phase voltage sampling values comprising the sampling value of the phase voltage of each phase line obtained by simultaneously measuring the phase lines.

[0078] The specific operation of this step 301 is consistent with step 201, which will not be repeated here.

[0079] The number of groups of real-time phase voltage sample values here can be 2-10 groups, and specifically 5 groups can be selected.

[0080] Step 302, determine the imbalance rate K between the capacitor groups based on the following formula AB and K AC :

[0081] R = (X'X) -1 X'Y,

[0082] wherein, x 1n represents x1, x 2n obtained by the nth measurement, y n represents y obtained by the nth measurement, x1 = (V X -V B ), x2 = (V X -V C ), y = V A -V X , wherein V X represents the sample value of the zero sequence voltage of the neutral point of the neutral point non-grounded system, V A represents the sample value of the phase voltage of the A-phase line, V B represents the sample value of the phase voltage of the B-phase line, V C represents the sample value of the phase voltage of the C-phase line, represents the capacitance value of the A-phase line, C B represents the capacitance value of the B-phase line, C C represents the capacitance value of the C-phase line.

[0083] This is because, for the neutral point non-grounded system without fault of the capacitor group, that is, for the neutral point non-grounded system in which the sample values of the phase voltages of the three-phase lines are all equal, the sum of the currents of the three-phase lines is 0, that is:

[0084] IA+I B +I C = jωC A (V A -V X ) + jωC B (V B -V X ) + jωC C (V C -V X ) = 0 (1.1)

[0085] wherein, I Ais a current of the A-phase line, I B is a current of the B-phase line, I C is a current of the C-phase line, V A is a sampled value of a phase voltage of the A-phase line, V B is a sampled value of a phase voltage of the B-phase line,

[0086] V C is a sampled value of a phase voltage of the C-phase line, V X is a sampled value of a zero sequence voltage of a neutral point of the neutral point ungrounded system, C A is a capacitance value of the A-phase line, C B is a capacitance value of the B-phase line, C C is a capacitance value of the C-phase line, j represents an imaginary symbol, and ω is an angular frequency of the neutral point ungrounded system.

[0087] The inventor found, through creative work, that if the above formula is simultaneously divided by jωC A after that, the above formula (1.1) is rewritten as the following formula (1.2):

[0088]

[0089] Assuming and 3V0= (V A + V B + V C ), the above formula (1.2) is rewritten as the following formula (1.3):

[0090] V X (1 + K AB + K AC )- 3V0+ V B (1-K AB )+ V C (1-K AC )= 0 (1.3)

[0091] Assuming where Vop is an operating voltage.

[0092] In order to find K AB and K AC , such that Vop = 0, i.e., |V x (1 + K AB + K AC )- 3V0+ V B (1-K AB )+ V C (1-K AC )| = 0, the above formula (1.3) is rewritten as the following formula (1.4):

[0093] K AB (V X -V B )+K AC (V X -V C )=3V0-(V X +V B +V C ) (1.4)

[0094] Assume: x1=(V X -V B ), x2=(V X -V C ), y=3V0-(V X +V B +V C )=V A -V X , a=K AB , b=K AC , then the above formula (1.4) is rewritten as ax1+bx2=y. According to this formula, assume that the x1 obtained by the first measurement is x 11 , x 21 , the x2 obtained by the second measurement is x 12 , x 22 , and so on, and a total of 5 measurements are made, then the following formula is obtained

[0095] ax 11 +bx 21 =y1

[0096] ax 12 +bx 22 =y2

[0097] ax 13 +bx 23 =y3

[0098] ax 14 +bx 24 =y4

[0099] ax 15 +bx 25 =y5

[0100] The above formula group is rewritten as the following matrix formula (1.5)

[0101]

[0102] wherein,

[0103] that is, the matrix formula (1.5) is XR=Y.

[0104] According to the Least Square Method, the following formula (1.6) is obtained according to the matrix formula (1.5):

[0105] R = (X'X) -1 X'Y (1.6)

[0106] where X' is the transposed matrix of matrix X, (X'X) -1 represents the inverse of X'X, and how to calculate it belongs to the prior art, which will not be described here. Since each measurement will have a corresponding error, finally a R will be obtained according to the above matrix formula, and then K AB and K AC are obtained. Based on the imbalance rate, the foregoing matrix formula (1.5) is brought in, and the accurate Vop can be obtained.

[0107] The following is described by taking three measurements as an example.

[0108] ax 11 + bx 21 = y1

[0109] ax 12 + bx 22 = y2

[0110] ax 13 + bx 23 = y3

[0111] Then the above formula is rewritten as: XR = Y.

[0112] Since the values in matrix X and matrix Y can be obtained by measurement, R can be determined by the following formula, that is,

[0113] R = (X'X) -1 X'Y.

[0114]

[0115] Suppose,

[0116]

[0117]

[0118] where,

[0119]

[0120] Q = x 11 x 21 + x 12 x 22 +13 x 23

[0121] M=x 11 y1+x 12 y2 + x 13 y3

[0122] N=x 21 y1+x 22 y2+x 23 y3

[0123]

[0124]

[0125] Since each of the above can be directly obtained by measurement, the corresponding imbalance rate K can be solved AB and K AC .

[0126] Step 303, determining the working voltage of the neutral point ungrounded system according to the imbalance rate.

[0127] Steps 301 and 302 are determined when the neutral point ungrounded system does not appear to be faulty, and the working voltage of the neutral point ungrounded system can be determined in real time according to the imbalance rate when no fault occurs, for example, by formula

[0128] to determine the working voltage.

[0129] Step 304, judging whether the working voltage is greater than or equal to a preset threshold value, if the judgment result is yes, it is determined that the internal fault of the neutral point ungrounded system occurs.

[0130] If the working voltage is still 0 or less than a preset threshold value, it means that no internal fault occurs, if the working voltage is greater than or equal to a preset threshold value, it means that an internal fault occurs, and the corresponding relay protection device needs to act to cut off the fault. The preset threshold value is, for example, 0.5V. Otherwise, it is an external fault.

[0131] In this way, according to the accurate working voltage, it can be determined whether an internal fault or an external fault occurs, so as to avoid the misoperation of the relay protection device. When a capacitor in a capacitor bank fails, for example, is broken down, the capacitance value on the phase line will not be equal to that of the other two phase lines, thereby causing the voltage on the phase circuit to be not equal to that of the other two phases.

[0132] According to the embodiment, the actual operating voltage can be determined by determining the unbalance rate between the capacitor banks, so that the operating voltage can be continuously monitored to determine whether a capacitor in the capacitor bank fails and whether the corresponding relay protection device needs to act.

[0133] Embodiment three

[0134] The embodiment provides a determination device of an operating voltage in a neutral point ungrounded system, wherein the power system comprises three-phase lines and three capacitor banks, one end of each capacitor bank is connected to a phase circuit, and the other end is connected to each other to form a neutral point, and the capacitor bank comprises a plurality of capacitors, that is, one capacitor bank is composed of a plurality of capacitors in series and parallel.

[0135] As shown in Figure 4A , it is a structural schematic diagram of the determination device of the operating voltage in the neutral point ungrounded system according to the embodiment. The determination device of the operating voltage in the neutral point ungrounded system comprises a sampling unit 401, a first determination unit 402 and a second determination unit 403.

[0136] The sampling unit 401 is configured to periodically sample the phase voltage of each phase line to obtain a plurality of groups of real-time phase voltage sampling values, each group of real-time phase voltage sampling values comprising the sampling values of the phase voltage of each phase line obtained by simultaneously measuring each phase line; the first determination unit 402 is configured to determine the unbalance rate between the capacitor banks based on the plurality of groups of real-time phase voltage sampling values, the unbalance rate being the ratio of the capacitance values between each two phase lines; and the second determination unit 403 is configured to determine the operating voltage of the neutral point ungrounded system according to the unbalance rate.

[0137] Optionally, the first determination unit 402 is specifically configured to:

[0138] determine the unbalance rate K between the capacitor banks based on the following formula AB and K AC :

[0139] R=(X′X) -1 X′Y,

[0140] wherein x 1n represents x1, x 2n represents x2, y n represents y obtained by the nth measurement, x1=(V X -V B ), x2=(V X -V C ), y=V A -V X ,

[0141] V X a sampling value of a zero sequence voltage representing a neutral point, V A a sampling value of a phase voltage representing an A-phase line,

[0142] V B a sampling value of a phase voltage representing a B-phase line, V C a sampling value of a phase voltage representing a C-phase line,

[0143] C A a capacitance value representing an A-phase line, C B a capacitance value representing a B-phase line, C C a capacitance value representing a C-phase line.

[0144] Optionally, the working voltage is wherein V0=(V A +V B +V C ) / 3.

[0145] Optionally, the number of groups of the sampling values of the real-time phase voltage is 2-10 groups.

[0146] Optionally, as shown in Figure 4B the determining device further comprises a third determining unit 404, configured to determine whether the fault is an internal fault according to the working voltage if it is identified that the neutral point ungrounded system is faulty, wherein the internal fault represents a fault of the capacitor in the capacitor bank.

[0147] The determination of whether the fault is an internal fault according to the working voltage comprises:

[0148] if the value of the working voltage is greater than or equal to a preset threshold, it is determined that the fault is an internal fault.

[0149] The working method of each unit of the embodiment is the same as that of the foregoing embodiments, and will not be described here again.

[0150] According to the determining device of the working voltage in the neutral point ungrounded system, the unbalance rate between the capacitor banks is obtained by the sampling values of the real-time phase voltage, and the accurate working voltage is determined according to the unbalance rate, so that the subsequent operation can be accurately performed.

[0151] The application also provides a device for determining the working voltage in a neutral point ungrounded system. The power system comprises three-phase lines and three capacitor banks. One end of each capacitor bank is connected to a phase circuit, and the other end is connected to each other to form a neutral point. The capacitor bank comprises a plurality of capacitors connected in series and / or parallel. The device comprises at least one memory and at least one processor. The memory is used to store instructions; the processor is used to execute the method for determining the working voltage in a neutral point ungrounded system according to the instructions stored in the memory.

[0152] The embodiments of the application also provide a readable storage medium. The readable storage medium stores machine-readable instructions. When the machine-readable instructions are executed by a machine, the machine executes the method for determining the working voltage in a neutral point ungrounded system according to any of the preceding embodiments.

[0153] The readable medium stores machine-readable instructions. When the machine-readable instructions are executed by a processor, the processor executes any of the preceding methods. Specifically, a system or device equipped with a readable storage medium can be provided. The readable storage medium stores software program codes for implementing the functions of any of the preceding embodiments. The computer or processor of the system or device reads and executes the machine-readable instructions stored in the readable storage medium.

[0154] In this case, the program codes read from the readable medium can implement the functions of any of the preceding embodiments. Therefore, the machine-readable codes and the readable storage medium storing the machine-readable codes constitute part of the application.

[0155] The embodiments of the readable storage medium include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROM. Alternatively, the program codes can be downloaded from a server computer or the cloud through a communication network.

[0156] Those skilled in the art should understand that various modifications and changes can be made to the above disclosed embodiments without departing from the spirit of the application. Therefore, the scope of protection of the application should be defined by the appended claims.

[0157] It should be noted that not all steps and units in the above flowcharts and system structure diagrams are necessary, and some steps or units can be omitted according to actual needs. The execution order of each step is not fixed and can be adjusted as needed. The device structure described in each of the above embodiments can be a physical structure or a logical structure, that is, some units can be implemented by the same physical entity, or some units can be implemented by multiple physical entities, or can be implemented by some components in multiple independent devices together.

[0158] In each of the above embodiments, a hardware unit can be implemented mechanically or electronically. For example, a hardware unit or processor can include permanent dedicated circuitry or logic (such as a dedicated processor, FPGA, or ASIC) to perform the corresponding operation. The hardware unit or processor can also include programmable logic or circuitry (such as a general-purpose processor or other programmable processor), which can be temporarily configured by software to perform the corresponding operation. The specific implementation method (mechanical method, or dedicated permanent circuit, or temporarily configured circuit) can be determined based on cost and time considerations.

[0159] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for determining the operating voltage in a neutral-point ungrounded system, wherein the power system includes three-phase lines and three capacitor banks, one end of each capacitor bank is connected to one phase circuit, and the other ends are interconnected to form a neutral point, wherein each capacitor bank includes multiple capacitors, characterized in that... The determination method includes: The phase voltage of each phase line is periodically sampled to obtain multiple sets of real-time phase voltage sample values. Each set of real-time phase voltage sample values ​​includes the phase voltage sample values ​​of each phase line obtained by simultaneously measuring each phase line. The imbalance rate between the capacitor banks is determined based on the sampled values ​​of the multiple sets of real-time phase voltages, and the imbalance rate is the ratio of the capacitance values ​​between each pair of phase lines. The operating voltage of the neutral point ungrounded system is determined based on the unbalance rate. Determining the imbalance rate among the capacitor banks based on the sampled values ​​of the multiple sets of real-time phase voltages includes: The imbalance rate among the capacitor banks is determined based on the following formula. and : R=( ， in, , = R= , Represents the result obtained through the nth measurement. , Represents the result obtained through the nth measurement. , Represents the result obtained through the nth measurement. , = , , = , The sampled value of the zero-sequence voltage at the neutral point is represented. This represents the sampled value of the phase voltage of phase A of the line. This represents the sampled value of the phase voltage of phase B line. This represents the sampled value of the phase voltage of phase C of the line. = , , This indicates the capacitance value of phase A of the circuit. This indicates the capacitance value of phase B of the circuit. This indicates the capacitance value of the C-phase line.

2. The determination method according to claim 1, characterized in that, The operating voltage is ,in = .

3. The determination method according to claim 1, characterized in that, The number of sampled values ​​of the real-time phase voltage is 2-10.

4. The determination method according to any one of claims 1-3, characterized in that, After determining the operating voltage of the neutral-point ungrounded system based on the unbalance rate, the method further includes: If a fault is detected in the neutral point ungrounded system, it is determined whether the fault is an internal fault based on the operating voltage. An internal fault indicates that a capacitor in the capacitor bank has failed. Determining whether the fault is internal based on the operating voltage includes: If the operating voltage is greater than or equal to a preset threshold, the fault is determined to be an internal fault.

5. A device for determining the working voltage in a neutral-point ungrounded system, wherein the power system includes three-phase lines and three capacitor banks, one end of each capacitor bank is connected to one phase circuit, and the other ends are interconnected to form a neutral point, wherein each capacitor bank includes multiple capacitors, characterized in that... The determining device includes: A sampling unit is used to periodically sample the phase voltage of each phase line to obtain multiple sets of real-time phase voltage sampling values. Each set of real-time phase voltage sampling values ​​includes the phase voltage sampling values ​​of each phase line obtained by simultaneously measuring each phase line. A first determining unit is configured to determine the imbalance rate between the capacitor banks based on the sampled values ​​of the multiple sets of real-time phase voltages, wherein the imbalance rate is the ratio of the capacitance values ​​between each pair of phase lines. A second determining unit is configured to determine the operating voltage of the neutral-point ungrounded system based on the unbalance rate; The first determining unit is specifically used for: The imbalance rate among the capacitor banks is determined based on the following formula. and : R=( ， in, , = R= , Represents the result obtained through the nth measurement. , Represents the result obtained through the nth measurement. , Represents the result obtained through the nth measurement. , = , , = , The sampled value of the zero-sequence voltage at the neutral point is represented. This represents the sampled value of the phase voltage of phase A of the line. This represents the sampled value of the phase voltage of phase B line. This represents the sampled value of the phase voltage of phase C of the line. = , , This indicates the capacitance value of phase A of the circuit. This indicates the capacitance value of phase B of the circuit. This indicates the capacitance value of the C-phase line.

6. The determining device according to claim 5, characterized in that, The operating voltage is ,in = .

7. The determining device according to claim 5, characterized in that, The number of sampled values ​​of the real-time phase voltage is 2-10.

8. The determining device according to any one of claims 5-7, characterized in that, Also includes: A third determining unit is used to determine, based on the operating voltage, whether the fault is an internal fault if a fault is identified in the neutral point ungrounded system, where an internal fault indicates a fault in a capacitor in the capacitor bank. Determining whether the fault is internal based on the operating voltage includes: If the operating voltage is greater than or equal to a preset threshold, the fault is determined to be an internal fault.

9. A device for determining the operating voltage in a neutral-point ungrounded system, wherein the power system includes three-phase lines and three capacitor banks, one end of each capacitor bank is connected to one phase circuit, and the other ends are interconnected to form a neutral point, wherein each capacitor bank includes multiple capacitors, characterized in that... The determining device includes: At least one memory for storing instructions; At least one processor is configured to execute, according to instructions stored in the memory, a method for determining the operating voltage in a neutral-point ungrounded system as described in any one of claims 1-4.

10. A readable storage medium, characterized in that, The readable storage medium stores machine-readable instructions, which, when executed by a machine, perform the method for determining the operating voltage in a neutral-point ungrounded system according to any one of claims 1-4.

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