Harmonic-voltage measurement method and apparatus, and capacitance-type voltage transformer and controller

Abstract

A harmonic-voltage measurement method and apparatus, and a capacitance-type voltage transformer and a controller. The method is applied to a controller (A) in a capacitance-type voltage transformer, and the method comprises: when a harmonic-voltage source is connected and an alternating-current busbar (S) is disconnected, acquiring a harmonic voltage of a primary side (T1) of an intermediate transformer (T) and a harmonic voltage of a secondary side (T2) of the intermediate transformer (S202); determining a harmonic transfer coefficient according to the two harmonic voltages (S204); when the harmonic-voltage source is disconnected and the alternating-current busbar (S) is connected, acquiring an operating current of a high-voltage capacitor (C1), the impedance of the high-voltage capacitor (C1), and an operating voltage of the secondary side (T2) of the intermediate transformer (T) (S206); determining a harmonic voltage of a low-voltage capacitor (C2) according to the harmonic transfer coefficient and the operating voltage of the secondary side (T2) of the intermediate transformer (T), and determining a harmonic voltage of the high-voltage capacitor (C1) according to the operating current of the high-voltage capacitor (C1) and the impedance of the high-voltage capacitor (C1) (S208); and determining a harmonic voltage of the alternating-current busbar (S) according to the harmonic voltage of the low-voltage capacitor (C2) and the harmonic voltage of the high-voltage capacitor (C1) (S210).

Description

Harmonic voltage measurement method, device, capacitor voltage transformer, and controller Technical Field

[0001] The present application relates to the field of measurement technology, and in particular to a harmonic voltage measurement method, device, capacitive voltage transformer, and controller. Background Art

[0002] With the construction of power systems, a large number of power electronic equipment are connected to the power grid, resulting in increasingly prominent harmonic problems. The existence of harmonic voltages seriously affects the normal operation of the power grid system, among which the harmonic voltage of the AC bus of the converter station is particularly prominent.

[0003] Currently, capacitor type voltage transformers (CVTs) are mostly used to monitor the harmonic voltage of the AC busbar of a converter station. However, the above method still cannot accurately monitor the harmonic voltage of the AC busbar, and the cost of switching to voltage transformers other than capacitor type is too high.

[0004] Therefore, there is an urgent need for a harmonic voltage measurement method for an AC busbar that has both high measurement accuracy and low cost.

[0005] Summary of the Invention

[0006] Based on this, it is necessary to provide a harmonic voltage measurement method, device, capacitive voltage transformer, and controller that can achieve both high measurement accuracy and low cost in order to address the above technical problems.

[0007] In a first aspect, the present application provides a harmonic voltage measurement method, which is applied to a controller in a capacitor voltage transformer. The capacitor voltage transformer includes a high-voltage capacitor, a low-voltage capacitor, an intermediate transformer, and a controller. The first end of the high-voltage capacitor is used to connect to the AC bus, the second end of the high-voltage capacitor is connected to the first end of the low-voltage capacitor, the primary side of the intermediate transformer is connected to the first end of the low-voltage capacitor, the first end of the low-voltage capacitor is also used to connect to the harmonic voltage source, the secondary side of the intermediate transformer is used to connect to the load, the first end of the controller is connected to the primary side of the intermediate transformer, the second end of the controller is connected to the secondary side of the intermediate transformer, and the third end of the controller is connected to the second end of the high-voltage capacitor. The method includes:

[0008] When the harmonic voltage source is connected and the AC bus is disconnected, a first voltage and a second voltage are obtained; the first voltage is the harmonic voltage on the primary side of the intermediate transformer, and the second voltage is the harmonic voltage on the secondary side of the intermediate transformer;

[0009] Determining a harmonic transfer coefficient based on the first voltage and the second voltage; the harmonic transfer coefficient is used to characterize the degree of influence of the intermediate transformer on the first voltage;

[0010] When the harmonic voltage source is disconnected and the AC bus is connected, the target current, the high-voltage capacitor impedance, and the third voltage are obtained; the third voltage is the operating voltage on the secondary side of the intermediate transformer, and the target current is the operating current of the high-voltage capacitor;

[0011] Determine the low-voltage capacitor harmonic voltage based on the harmonic transfer coefficient and the third voltage, and determine the high-voltage capacitor harmonic voltage based on the target current and the high-voltage capacitor impedance;

[0012] The harmonic voltage of the AC bus is determined based on the low-voltage capacitor harmonic voltage and the high-voltage capacitor harmonic voltage.

[0013] In one embodiment, determining the low-voltage capacitor harmonic voltage according to the harmonic transfer coefficient and the third voltage includes:

[0014] performing Fourier decomposition on the third voltage according to a target Fourier series to determine harmonic components of the third voltage;

[0015] The low-voltage capacitor harmonic voltage is determined according to the harmonic component and harmonic transfer coefficient of the third voltage.

[0016] In one embodiment, determining the high-voltage capacitor harmonic voltage according to the target current and the high-voltage capacitor impedance includes:

[0017] Performing Fourier decomposition on the target current according to the target Fourier series to determine the harmonic components of the target current;

[0018] The high-voltage capacitor harmonic voltage is determined based on the harmonic components of the target current and the high-voltage capacitor impedance.

[0019] In one embodiment, the low voltage capacitor harmonic voltage can be obtained by the following expression: U C2 =K*U T2

[0020] Among them, U C2 is the low voltage capacitor harmonic voltage, K is the harmonic transfer coefficient, U T2 is the harmonic component of the third voltage.

[0021] In one embodiment, the high-voltage capacitor harmonic voltage can be obtained by the following expression: U C1 =Z C1 *I C1

[0022] Among them, U C1 is the high voltage capacitor harmonic voltage; Z C1 is the high voltage capacitor impedance; I C1 is the harmonic component of the first current.

[0023] In one embodiment, determining the target Fourier series includes:

[0024] The target Fourier series is determined to be the harmonic order of the first voltage.

[0025] In a second aspect, a capacitive voltage transformer is provided, which includes a high-voltage capacitor, a low-voltage capacitor, an intermediate transformer and a controller, wherein the first end of the high-voltage capacitor is used to connect to the AC bus, the second end of the high-voltage capacitor is connected to the first end of the low-voltage capacitor, the primary side of the intermediate transformer is connected to the first end of the low-voltage capacitor, the first end of the low-voltage capacitor is also used to connect to a harmonic voltage source, the secondary side of the intermediate transformer is used to connect to a load, the first end of the controller is connected to the primary side of the intermediate transformer, the second end of the controller is connected to the secondary side of the intermediate transformer, the third end of the controller is connected to the second end of the high-voltage capacitor, and the controller is used to execute the harmonic voltage measurement method in the above embodiment.

[0026] In a third aspect, a harmonic voltage measuring device is provided, which is applied to the controller in the above embodiment, and the device includes:

[0027] A first acquisition module is configured to acquire a first voltage and a second voltage when a harmonic voltage source is connected and the AC bus is disconnected; the first voltage is the harmonic voltage on the primary side of the intermediate transformer, and the second voltage is the harmonic voltage on the secondary side of the intermediate transformer;

[0028] A harmonic transfer coefficient determination module is used to determine the harmonic transfer coefficient based on the first voltage and the second voltage; the harmonic transfer coefficient is used to characterize the degree of influence of the intermediate transformer on the first voltage;

[0029] The second acquisition module is used to obtain the target current, the high-voltage capacitor impedance and the third voltage when the harmonic voltage source is disconnected and the AC bus is connected; the third voltage is the operating voltage of the secondary side of the intermediate transformer, and the target current is the operating current of the high-voltage capacitor;

[0030] a first voltage determination module, configured to determine the low-voltage capacitor harmonic voltage according to the harmonic transfer coefficient and the third voltage, and to determine the high-voltage capacitor harmonic voltage according to the target current and the high-voltage capacitor impedance;

[0031] The second voltage determination module is used to determine the harmonic voltage of the AC bus according to the low-voltage capacitor harmonic voltage and the high-voltage capacitor harmonic voltage.

[0032] In a fourth aspect, a controller is provided, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method in the above embodiment when executing the computer program.

[0033] In a fifth aspect, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method in the above embodiment are implemented.

[0034] The above-mentioned harmonic voltage measurement method, device, capacitor voltage transformer, and controller have at least the following beneficial effects:

[0035] When the above method is applied to the above-mentioned capacitor voltage transformer, the controller can obtain the harmonic voltage on the primary side of the intermediate transformer and the harmonic voltage on the secondary side of the intermediate transformer when the harmonic voltage source is connected and the AC bus is disconnected (before performing harmonic voltage measurement), and determine the harmonic transfer coefficient used to reflect the degree of influence of the intermediate transformer on the harmonic voltage input to the primary side of the intermediate transformer based on the above two harmonic voltages; and when the harmonic voltage source is disconnected and the AC bus is connected (during the performance of harmonic voltage measurement), the working current of the high-voltage capacitor, the high-voltage capacitor impedance and the working voltage on the secondary side of the intermediate transformer during the actual operation of the capacitor voltage transformer are obtained, and the controller can determine the harmonic voltage on the primary side of the intermediate transformer during the actual operation of the capacitor voltage transformer based on the harmonic transfer coefficient and the harmonic component of the working voltage on the secondary side of the intermediate transformer. Since the intermediate transformer is connected in parallel with the low-voltage capacitor, the harmonic transfer coefficient can also reflect the degree of change of the low-voltage capacitor harmonic voltage after passing through the intermediate transformer, and then the low-voltage capacitor harmonic voltage can be determined based on the parallel relationship; the controller can also determine the high-voltage capacitor harmonic voltage based on the harmonic component of the working current of the high-voltage capacitor and the high-voltage capacitor impedance; since the voltage of the AC bus is divided by the high and low voltage capacitors of the CVT, the harmonic voltage of the AC bus can be directly determined when the low-voltage capacitor harmonic voltage and the high-voltage capacitor harmonic voltage are determined. Compared with the traditional technology that directly uses the CVT primary and secondary transfer ratio of the fundamental frequency voltage component in the working voltage for measurement and calculation, the present application can better reflect the degree of influence of the intermediate transformer on the harmonic voltage through the harmonic transfer coefficient determined based on the loaded harmonic voltage, thereby more accurately measuring the harmonic voltage of the AC bus, and the harmonic voltage measurement can be achieved without changing the structure of the capacitive voltage transformer, which is beneficial to reducing measurement costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is an equivalent circuit diagram of a capacitive voltage transformer according to an embodiment;

[0037] FIG2 is a schematic flow chart of a harmonic voltage measurement method according to an embodiment;

[0038] FIG3 is a schematic diagram of waveforms of a target current and a third voltage in one embodiment;

[0039] FIG4 is a flow chart illustrating the steps of determining the harmonic voltage of a low-voltage capacitor according to the harmonic transfer coefficient and the third voltage in one embodiment;

[0040] FIG5 is a flow chart illustrating steps for determining the harmonic voltage of a high-voltage capacitor according to a target current and a high-voltage capacitor impedance in one embodiment;

[0041] FIG6 is a block diagram of a harmonic voltage measuring device according to an embodiment;

[0042] FIG7 is a diagram showing the internal structure of a controller in one embodiment. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0044] The harmonic voltage measurement method provided in the embodiment of the present application can be applied to the controller A in the capacitor voltage transformer as shown in Figure 1. The capacitor voltage transformer includes a high-voltage capacitor C1, a low-voltage capacitor C2, an intermediate transformer T, and a controller A. The first end of the high-voltage capacitor C1 is used to connect to the AC bus S, the second end of the high-voltage capacitor C1 is connected to the first end of the low-voltage capacitor C2, the primary side T1 of the intermediate transformer T is connected to the first end of the low-voltage capacitor C2, the first end of the low-voltage capacitor C2 is also used to connect to the harmonic voltage source, the secondary side T2 of the intermediate transformer T is used to connect to the load, the first end of the controller A is connected to the primary side T1 of the intermediate transformer T, the second end of the controller A is connected to the secondary side T2 of the intermediate transformer T, and the third end of the controller A is connected to the second end of the high-voltage capacitor C1; wherein the secondary side of the intermediate transformer is also used to connect to the load B. When the harmonic voltage source is connected and the AC bus S is disconnected, controller A obtains a first voltage and a second voltage; the first voltage is the harmonic voltage of the primary side T1 of the intermediate transformer T, and the second voltage is the harmonic voltage of the secondary side T2 of the intermediate transformer T; the harmonic transfer coefficient is determined based on the first voltage and the second voltage; the harmonic transfer coefficient is used to characterize the degree of influence of the intermediate transformer T on the first voltage; when the harmonic voltage source is disconnected and the AC bus S is connected, controller A obtains a target current, the impedance of the high-voltage capacitor C1 and a third voltage; the third voltage is the operating voltage of the secondary side T2 of the intermediate transformer T, and the target current is the operating current of the high-voltage capacitor C1; the harmonic voltage of the low-voltage capacitor C2 is determined based on the harmonic transfer coefficient and the third voltage, and the harmonic voltage of the high-voltage capacitor C1 is determined based on the target current and the impedance of the high-voltage capacitor C1; controller A determines the harmonic voltage of the AC bus S based on the harmonic voltage of the low-voltage capacitor C2 and the harmonic voltage of the high-voltage capacitor C1.

[0045] As can be seen from the above background technology, the operating voltage or operating current of the AC bus includes a fundamental frequency component and a harmonic component. Therefore, the operating voltage or operating current connected to the capacitor voltage transformer also includes a fundamental frequency component and a harmonic component. The inventors have discovered that the reason why the harmonic voltage of the AC bus S cannot be accurately measured using a capacitor voltage transformer is that the design of the existing capacitor voltage transformer only considers the measurement accuracy of the fundamental frequency component of the operating voltage or operating current. That is, the transfer ratio of the intermediate transformer T of the capacitor voltage transformer can only reflect the degree of change of the fundamental frequency component after passing through the intermediate transformer T, but cannot reflect the degree of change of the harmonic components of the operating voltage or operating current. If the measurement is based on the transfer ratio of the fundamental frequency component, it will inevitably lead to inaccurate harmonic voltage measurement.

[0046] In one embodiment, as shown in FIG2 , a harmonic voltage measurement method is provided. The method is described by taking the controller A in the capacitor voltage transformer in FIG1 as an example, wherein the capacitor voltage transformer includes a high-voltage capacitor C1, a low-voltage capacitor C2, an intermediate transformer T, and a controller A. The first end of the high-voltage capacitor C1 is used to connect to the AC bus S, the second end of the high-voltage capacitor C1 is connected to the first end of the low-voltage capacitor C2, the primary side T1 of the intermediate transformer T is connected to the first end of the low-voltage capacitor C2, the first end of the low-voltage capacitor C2 is also used to connect to the harmonic voltage source, the secondary side T2 of the intermediate transformer T is used to connect to the load, the first end of the controller A is connected to the primary side T1 of the intermediate transformer T, the second end of the controller A is connected to the secondary side T2 of the intermediate transformer T, and the third end of the controller A is connected to the second end of the high-voltage capacitor C1. The method includes the following steps:

[0047] S202 , when the harmonic voltage source is connected and the AC bus S is disconnected, obtain a first voltage and a second voltage; the first voltage is the harmonic voltage of the primary side T1 of the intermediate transformer T, and the second voltage is the harmonic voltage of the secondary side T2 of the intermediate transformer T.

[0048] Specifically, when the harmonic voltage source is connected and the AC bus S is disconnected, which is equivalent to the capacitor voltage transformer not being connected to the converter station AC bus S (this is before harmonic voltage measurement), the harmonic voltage is input to the first end of the low-voltage capacitor C2 via the harmonic power source. Since the low-voltage capacitor C2 is connected in parallel with the intermediate transformer T, the harmonic voltage on the primary side T1 of the intermediate transformer T is equal to the voltage of the low-voltage capacitor C2. The harmonic voltage is input to the intermediate transformer T through the primary side T1 of the intermediate transformer T, and after being modulated by the intermediate transformer T, it is output to the secondary side T2 of the intermediate transformer T. Controller A can obtain the above-mentioned first voltage and second voltage by measuring the voltage on the primary side T1 of the intermediate transformer T and the voltage on the secondary side T2 of the intermediate transformer T.

[0049] S204 , determining a harmonic transfer coefficient according to the first voltage and the second voltage; the harmonic transfer coefficient is used to characterize the degree of influence of the intermediate transformer T on the first voltage.

[0050] The harmonic transfer coefficient (HTC) characterizes the degree to which the intermediate transformer T modulates the first voltage input thereto. Since the intermediate transformer T modulates and isolates the input voltage, different parameter configurations of the intermediate transformer T will modulate voltages of varying frequencies differently. The capacitor voltage transformer (CVT) described in the background is designed for the fundamental frequency component of the operating voltage. The intermediate transformer T of this CVT maintains a fixed modulation of this fundamental frequency component. However, if the voltage frequency changes, the modulation degree will vary. For example, when the voltage input to the primary side T1 of the intermediate transformer T is 380V and the frequency is 50Hz, the voltage obtained on the secondary side T2 of the intermediate transformer T is 120V. However, when the voltage input to the primary side T1 of the intermediate transformer T is 380V and the frequency is 100Hz, the voltage obtained on the secondary side T2 of the intermediate transformer T becomes 60V. It should be noted that the specific parameters involved in the voltage modulation process of the intermediate transformer T described above are merely illustrative and are not intended to be limiting.

[0051] Specifically, according to the measurement requirements of the harmonic voltage, a harmonic voltage source can be used to input harmonic voltages of different harmonic orders to the first end of the low-voltage capacitor C2. By obtaining a first voltage before inputting the intermediate transformer T and comparing it with a second voltage after inputting the intermediate transformer T, the harmonic transfer coefficients of the harmonic voltages of different harmonic orders can be obtained. In a specific embodiment, the harmonic transfer coefficient can be determined by the following expression: K = U S / U T2_n

[0052] Where K is the harmonic transfer coefficient; U S is the first voltage; U T2_n is the harmonic voltage of the intermediate secondary side T2. For example, when the harmonic voltage source inputs the 5th harmonic voltage, the measured U S =0.707049∠149.884°; U T2_n =0.0752622∠-19.74°; then the harmonic transfer coefficient of the 5th harmonic voltage is K=U S / U T2_n =9.39447∠169.624°.

[0053] S206. When the harmonic voltage source is disconnected and the AC bus S is connected, obtain the target current, the impedance of the high-voltage capacitor C1, and the third voltage; the third voltage is the operating voltage of the secondary side T2 of the intermediate transformer T, and the target current is the operating current of the high-voltage capacitor C1.

[0054] Specifically, when the harmonic voltage source is disconnected and the AC bus S is connected, it is equivalent to the working voltage of the capacitor voltage transformer accessing the converter station AC bus S (at this time, it is in the measurement process of the harmonic voltage). When the capacitor voltage transformer is accessed to the working voltage of the AC bus S, by obtaining the working current of the high-voltage capacitor C1, the high-voltage capacitor C1 impedance and the working voltage of the secondary side T2 of the intermediate transformer T, the measurement result of the AC bus S is reflected in the actual working process of the capacitor voltage transformer, and a data basis is provided for the subsequent measurement and calculation of the harmonic voltage. For example, in a specific embodiment, the waveforms of the measured working current I of the high-voltage capacitor C1 and the working voltage U of the secondary side T2 of the intermediate transformer T are shown in Figure 3.

[0055] S208 , determining the harmonic voltage of the low-voltage capacitor C2 according to the harmonic transfer coefficient and the third voltage, and determining the harmonic voltage of the high-voltage capacitor C1 according to the target current and the impedance of the high-voltage capacitor C1 .

[0056] Specifically, based on the third voltage (the operating voltage of the secondary side T2 of the intermediate transformer T), the harmonic components of the operating voltage can be obtained, thereby determining the harmonic voltage of the secondary side T2 of the intermediate transformer T during the actual measurement of the capacitor voltage transformer. According to the structure of the capacitor voltage transformer and the significance of the harmonic transfer coefficient, based on the harmonic voltage and harmonic transfer coefficient of the secondary side T2 of the intermediate transformer T, the harmonic voltage of the primary side T1 of the intermediate transformer T during the actual measurement of the capacitor voltage transformer can be inferred, and based on the parallel relationship between the low-voltage capacitor C2 and the intermediate transformer T, the harmonic voltage of the low-voltage capacitor C2 during the actual measurement of the capacitor voltage transformer can be determined. Secondly, based on the target current (the operating current of the high-voltage capacitor C1), the harmonic components of the operating current can be obtained. When the impedance of the high-voltage capacitor C1 is known, the harmonic voltage of the high-voltage capacitor C1 during the actual measurement of the capacitor voltage transformer can be determined according to Ohm's law.

[0057] S210 , determining the harmonic voltage of the AC bus S according to the harmonic voltage of the low-voltage capacitor C2 and the harmonic voltage of the high-voltage capacitor C1 .

[0058] As mentioned above, since the voltage of the AC bus S is divided by the high and low voltage capacitors C2 of the CVT, the harmonic voltage of the AC bus S can be directly determined when the harmonic voltage of the low voltage capacitor C2 and the harmonic voltage of the high voltage capacitor C1 are determined.

[0059] Controller A can obtain the harmonic voltage of the primary side T1 of the intermediate transformer T and the harmonic voltage of the secondary side T2 of the intermediate transformer T when the harmonic voltage source is connected and the AC bus S is disconnected (before performing harmonic voltage measurement), and determine the harmonic transfer coefficient used to reflect the degree of influence of the intermediate transformer T on the harmonic voltage of the primary side T1 of the input intermediate transformer T based on the above two harmonic voltages; and when the harmonic voltage source is disconnected and the AC bus S is connected (during the performance of harmonic voltage measurement), obtain the working current of the high-voltage capacitor C1, the impedance of the high-voltage capacitor C1 and the working voltage of the secondary side T2 of the intermediate transformer T during the actual operation of the capacitive voltage transformer. Controller A can determine the harmonic voltage of the primary side T1 of the intermediate transformer T during the actual operation of the capacitive voltage transformer based on the harmonic transfer coefficient and the harmonic component of the working voltage of the secondary side T2 of the intermediate transformer T. Since the intermediate transformer T is connected in parallel with the low-voltage capacitor C2, the harmonic transfer coefficient can also reflect the degree of change of the harmonic voltage of the low-voltage capacitor C2 after passing through the intermediate transformer T, and then the harmonic voltage of the low-voltage capacitor C2 can be determined based on the parallel relationship; the controller A can also determine the harmonic voltage of the high-voltage capacitor C1 according to the harmonic component of the working current of the high-voltage capacitor C1 and the impedance of the high-voltage capacitor C1; since the voltage of the AC bus S is divided by the high and low-voltage capacitors C2 of the CVT, when the harmonic voltage of the low-voltage capacitor C2 and the harmonic voltage of the high-voltage capacitor C1 are determined, the harmonic voltage of the AC bus S can be directly determined. Compared with the traditional technology of directly using the CVT primary and secondary transfer ratio of the fundamental frequency voltage component in the working voltage for measurement and calculation, the present application can better reflect the degree of influence of the intermediate transformer T on the harmonic voltage through the harmonic transfer coefficient determined based on the loaded harmonic voltage, thereby more accurately measuring the harmonic voltage of the AC bus S, and achieving the measurement of the harmonic voltage without changing the structure of the capacitive voltage transformer, which is beneficial to reducing the measurement cost.

[0060] In one embodiment, as shown in FIG4 , determining the harmonic voltage of the low-voltage capacitor C2 according to the harmonic transfer coefficient and the third voltage includes:

[0061] S402 : Perform Fourier decomposition on the third voltage according to a target Fourier series to determine harmonic components of the third voltage.

[0062] The target Fourier series is the series required for Fourier decomposition.

[0063] Specifically, any periodic alternating current quantity can be decomposed into its components by Fourier decomposition. For example, for the third voltage described above, when the target Fourier series is 5, the 5th harmonic component of the third voltage can be obtained by Fourier decomposition of the third voltage.

[0064] S404 , determining the harmonic voltage of the low-voltage capacitor C2 according to the harmonic component and the harmonic transfer coefficient of the third voltage.

[0065] Specifically, by multiplying the harmonic component of the third voltage and the harmonic transfer coefficient, the harmonic voltage of the primary side T1 of the intermediate transformer T during the actual measurement of the capacitor voltage transformer corresponding to the harmonic component can be obtained, and based on the parallel relationship, the harmonic voltage of the low-voltage capacitor C2 during the actual measurement of the capacitor voltage transformer can be determined. In addition to directly multiplying the harmonic component of the third voltage and the harmonic transfer coefficient to obtain the harmonic voltage of the primary side T1 of the intermediate transformer T, a correction factor can also be added. For example, the correction factor can be a constant. The specific numerical value can be selected according to the needs of different power systems and is not limited here.

[0066] In one embodiment, the harmonic voltage of the low voltage capacitor C2 can be obtained by the following expression: C2 =K*U T2

[0067] Among them, U C2 is the harmonic voltage of low-voltage capacitor C2, K is the harmonic transfer coefficient, U T2 is the harmonic component of the third voltage. For example, when K is the harmonic transfer coefficient of the 5th harmonic voltage, K=9.39447∠169.624°; U T2 =0.00943956∠-19.6801°, at this time U C2 =K*U T2 =0.0886797∠149.944°.

[0068] In one embodiment, as shown in FIG5 , determining the harmonic voltage of the high-voltage capacitor C1 according to the target current and the impedance of the high-voltage capacitor C1 includes:

[0069] S502 , performing Fourier decomposition on the target current according to the target Fourier series to determine harmonic components of the target current.

[0070] The meaning represented by the target Fourier series in this embodiment can refer to the above embodiment, and the harmonic component of the target current is the harmonic component of the working current of the high-voltage capacitor C1 (ie, the harmonic current of the high-voltage capacitor C1).

[0071] Specifically, for example, when the target Fourier series is 5th, the target current is Fourier decomposed to obtain the 5th harmonic component of the target current (ie, the 5th harmonic current of the high-voltage capacitor C1 in the actual measurement process of the capacitor voltage transformer).

[0072] S504 , determining the harmonic voltage of the high-voltage capacitor C1 according to the harmonic components of the target current and the impedance of the high-voltage capacitor C1 .

[0073] Specifically, based on Ohm's law, after knowing the harmonic component of the target current (the harmonic current of the high-voltage capacitor C1 during the actual measurement of the capacitive voltage transformer) and the impedance of the high-voltage capacitor C1, the harmonic voltage of the high-voltage capacitor C1 during the actual measurement of the capacitive voltage transformer can be obtained. On this basis, different correction coefficients can be set according to the needs of the same power system to correct the impact of different power systems.

[0074] In one embodiment, the harmonic voltage of the high-voltage capacitor C1 can be obtained by the following expression: C1 =Z C1 *I C1

[0075] Among them, U C1 is the harmonic voltage of high-voltage capacitor C1; Z C1 is the impedance of high-voltage capacitor C1; I C1 is the harmonic component of the first current. For example, when I C1 is the fifth harmonic component of the first current, I C1 =6.484e-5∠-120.116°, Z C1 =124097.4236∠-90°, at this time U C1 =Z C1 *I C1 =8.04652∠-210.116°.

[0076] In one embodiment, the harmonic voltage of the AC bus S can be obtained by the following expression: AC =U C1 +U C2

[0077] Among them, U AC is the harmonic voltage of the AC bus S; U C1 is the harmonic voltage of high-voltage capacitor C1; U C2 is the harmonic voltage of the low voltage capacitor C2. For example, when U C1 =8.04652∠-210.116°, U C2 =K*U T2 =0.0886797∠149.944°, then U AC =U C1 +U C2 =8.1352∠149.884°.

[0078] In one embodiment, determining the target Fourier series includes:

[0079] The target Fourier series is determined to be the harmonic order of the first voltage.

[0080] Specifically, in order to match the measured harmonic transfer coefficient with the harmonic components of the third voltage and the target current, the target Fourier series is determined to be the harmonic order of the first voltage to improve measurement accuracy.

[0081] The present application also provides a capacitive voltage transformer, which includes a high-voltage capacitor C1, a low-voltage capacitor C2, an intermediate transformer T and a controller A. The first end of the high-voltage capacitor C1 is used to connect to the AC bus S, the second end of the high-voltage capacitor C1 is connected to the first end of the low-voltage capacitor C2, the primary side T1 of the intermediate transformer T is connected to the first end of the low-voltage capacitor C2, the first end of the low-voltage capacitor C2 is also used to connect to a harmonic voltage source, the secondary side T2 of the intermediate transformer T is used to connect to a load, the first end of the controller A is connected to the primary side T1 of the intermediate transformer T, the second end of the controller A is connected to the secondary side T2 of the intermediate transformer T, and the third end of the controller A is connected to the second end of the high-voltage capacitor C1. The controller A is used to execute the harmonic voltage measurement method in the above embodiment.

[0082] Among them, those skilled in the art can directly know the connection method and specific structure of each component in the capacitor voltage transformer by referring to Figure 1, and will not repeat them here. For how the capacitor voltage transformer measures the harmonic voltage of the AC bus S, please refer to the description in the above embodiment, and will not repeat them here.

[0083] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0084] Based on the same inventive concept, embodiments of the present application further provide a harmonic voltage measurement device for implementing the aforementioned harmonic voltage measurement method. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more of the following embodiments of the harmonic voltage measurement device can be found in the aforementioned limitations of the harmonic voltage measurement method and are not further elaborated here.

[0085] In one embodiment, as shown in FIG6 , a harmonic voltage measuring device is provided, comprising:

[0086] The first acquisition module 602 is used to obtain a first voltage and a second voltage when a harmonic voltage source is connected and the AC bus S is disconnected; the first voltage is the harmonic voltage of the primary side T1 of the intermediate transformer T, and the second voltage is the harmonic voltage of the secondary side T2 of the intermediate transformer T.

[0087] The harmonic transfer coefficient determination module 604 is configured to determine a harmonic transfer coefficient based on the first voltage and the second voltage. The harmonic transfer coefficient is used to characterize the degree of influence of the intermediate transformer T on the first voltage.

[0088] The second acquisition module 606 is used to obtain the target current, the impedance of the high-voltage capacitor C1 and the third voltage when the harmonic voltage source is disconnected and the AC bus S is connected; the third voltage is the operating voltage of the secondary side T2 of the intermediate transformer T, and the target current is the operating current of the high-voltage capacitor C1.

[0089] The first voltage determination module 608 is configured to determine the harmonic voltage of the low-voltage capacitor C2 according to the harmonic transfer coefficient and the third voltage, and to determine the harmonic voltage of the high-voltage capacitor C1 according to the target current and the impedance of the high-voltage capacitor C1.

[0090] The second voltage determination module 610 is configured to determine the harmonic voltage of the AC bus S according to the harmonic voltage of the low-voltage capacitor C2 and the harmonic voltage of the high-voltage capacitor C1.

[0091] In one embodiment, the first voltage determination module 608 includes:

[0092] The voltage harmonic component determining unit is configured to perform Fourier decomposition on the third voltage according to a target Fourier series to determine the harmonic components of the third voltage.

[0093] The low-voltage capacitor C2 harmonic voltage determining unit is used to determine the low-voltage capacitor C2 harmonic voltage according to the harmonic component and harmonic transfer coefficient of the third voltage.

[0094] In one embodiment, the low-voltage capacitor C2 harmonic voltage determination unit includes:

[0095] The low-voltage capacitor C2 harmonic voltage determination subunit is used to determine the low-voltage capacitor C2 harmonic voltage through the following expression: U C2 =K*U T2

[0096] Among them, U C2 is the harmonic voltage of low-voltage capacitor C2, K is the harmonic transfer coefficient, U T2 is the harmonic component of the third voltage.

[0097] In one embodiment, the first voltage determination module 608 further includes:

[0098] The current harmonic component determination unit is used to perform Fourier decomposition on the target current according to the target Fourier series to determine the harmonic components of the target current.

[0099] The high-voltage capacitor C1 harmonic voltage determining unit is used to determine the high-voltage capacitor C1 harmonic voltage according to the harmonic components of the target current and the impedance of the high-voltage capacitor C1.

[0100] In one embodiment, the high-voltage capacitor C1 harmonic voltage determination unit includes:

[0101] The high-voltage capacitor C1 harmonic voltage determination subunit is used to determine the high-voltage capacitor C1 harmonic voltage using the following expression: U C1 =Z C1 *I C1

[0102] Among them, U C1 is the harmonic voltage of high-voltage capacitor C1; Z C1 is the impedance of high-voltage capacitor C1; I C1 is the harmonic component of the first current.

[0103] In one embodiment, the voltage harmonic component determining unit and the current harmonic component determining unit include:

[0104] The target Fourier series determining unit is configured to determine the target Fourier series to be the harmonic order of the first voltage.

[0105] Each module in the harmonic voltage measurement device can be implemented in whole or in part through software, hardware, or a combination thereof. Each module can be embedded in or independent of a processor in a computer device in hardware form, or can be stored in a memory in the computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0106] In one embodiment, a computer device is provided, which may be a controller, and its internal structure diagram may be shown in Figure 7. The computer device includes a processor, a memory, an input / output interface (I / O) and a communication interface. The processor, the memory and the input / output interface are connected via a system bus, and the communication interface is connected to the system bus via the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store voltage, current and impedance data. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, a harmonic voltage measurement method is implemented.

[0107] Those skilled in the art will understand that the structure shown in FIG7 is merely a block diagram of a portion of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0108] In one embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0109] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0110] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0111] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0112] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that variations and improvements may be made by those skilled in the art without departing from the spirit of the present application, and such variations and improvements are within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A harmonic voltage measurement method, characterized in that: A controller applied to a capacitive voltage transformer, the capacitive voltage transformer comprising a high-voltage capacitor, a low-voltage capacitor, an intermediate transformer and a controller, wherein the first end of the high-voltage capacitor is used to connect to an AC bus, the second end of the high-voltage capacitor is connected to the first end of the low-voltage capacitor, the primary side of the intermediate transformer is connected to the first end of the low-voltage capacitor, the first end of the low-voltage capacitor is also used to connect to a harmonic voltage source, the secondary side of the intermediate transformer is used to connect to a load, the first end of the controller is connected to the primary side of the intermediate transformer, the second end of the controller is connected to the secondary side of the intermediate transformer, the third end of the controller is connected to the second end of the high-voltage capacitor, and the method comprises: When the harmonic voltage source is connected and the AC bus is disconnected, a first voltage and a second voltage are obtained; the first voltage is the harmonic voltage on the primary side of the intermediate transformer, and the second voltage is the harmonic voltage on the secondary side of the intermediate transformer; Determining a harmonic transfer coefficient according to the first voltage and the second voltage; the harmonic transfer coefficient is used to characterize the degree of influence of the intermediate transformer on the first voltage; When the harmonic voltage source is disconnected and the AC bus is connected, a target current, a high-voltage capacitor impedance and a third voltage are obtained; the third voltage is the operating voltage of the secondary side of the intermediate transformer, and the target current is the operating current of the high-voltage capacitor; Determine the low-voltage capacitor harmonic voltage according to the harmonic transfer coefficient and the third voltage, and determine the high-voltage capacitor harmonic voltage according to the target current and the high-voltage capacitor impedance; The harmonic voltage of the AC bus is determined according to the low-voltage capacitor harmonic voltage and the high-voltage capacitor harmonic voltage.

2. The method according to claim 1, characterized in that The step of determining the low-voltage capacitor harmonic voltage according to the harmonic transfer coefficient and the third voltage includes: Performing Fourier decomposition on the third voltage according to a target Fourier series to determine a harmonic component of the third voltage; The low-voltage capacitor harmonic voltage is determined according to the harmonic component of the third voltage and the harmonic transfer coefficient.

3. The method according to claim 1, characterized in that The step of determining the high-voltage capacitor harmonic voltage according to the target current and the high-voltage capacitor impedance includes: Performing Fourier decomposition on the target current according to a target Fourier series to determine a harmonic component of the target current; The high-voltage capacitor harmonic voltage is determined according to the harmonic component of the target current and the high-voltage capacitor impedance.

4. The method according to claim 2, characterized in that: The low voltage capacitor harmonic voltage can be obtained by the following expression: U C2 =K*U T2 Among them, U C2 is the low voltage capacitor harmonic voltage, K is the harmonic transfer coefficient, U T2 is the harmonic component of the third voltage.

5. The method according to claim 3, characterized in that: The high voltage capacitor harmonic voltage can be obtained by the following expression: U C1 =Z C1 *I C1 Among them, U C1 is the high voltage capacitor harmonic voltage; Z C1 is the high voltage capacitor impedance; I C1 is the harmonic component of the first current.

6. The method according to any one of claims 2 to 3, characterized in that The determination of the target Fourier series includes: The target Fourier series is determined to be a harmonic order of the first voltage.

7. A capacitive voltage transformer, characterized in that: The capacitive voltage transformer includes a high-voltage capacitor, a low-voltage capacitor, an intermediate transformer and a controller, wherein the first end of the high-voltage capacitor is used to connect to an AC bus, the second end of the high-voltage capacitor is connected to the first end of the low-voltage capacitor, the primary side of the intermediate transformer is connected to the first end of the low-voltage capacitor, the first end of the low-voltage capacitor is also used to connect to a harmonic voltage source, the secondary side of the intermediate transformer is used to connect to a load, the first end of the controller is connected to the primary side of the intermediate transformer, the second end of the controller is connected to the secondary side of the intermediate transformer, the third end of the controller is connected to the second end of the high-voltage capacitor, and the controller is used to execute the harmonic voltage measurement method described in any one of claims 1 to 6.

8. A harmonic voltage measuring device, characterized in that: Applied to the controller of claim 1, the device comprises: The first acquisition module is used for, when the harmonic voltage source is connected and the AC bus is disconnected, Acquire a first voltage and a second voltage; the first voltage is a harmonic voltage on the primary side of the intermediate transformer, and the second voltage is a harmonic voltage on the secondary side of the intermediate transformer; A harmonic transfer coefficient determination module, used to determine a harmonic transfer coefficient according to the first voltage and the second voltage; the harmonic transfer coefficient is used to characterize the influence of the intermediate transformer on the first voltage; A second acquisition module is used to acquire the target current, the high-voltage capacitor impedance and the third voltage when the harmonic voltage source is disconnected and the AC bus is connected; the third voltage is the working voltage of the secondary side of the intermediate transformer, and the target current is the working current of the high-voltage capacitor; a first voltage determination module, configured to determine a low-voltage capacitor harmonic voltage according to the harmonic transfer coefficient and the third voltage, and to determine a high-voltage capacitor harmonic voltage according to the target current and the high-voltage capacitor impedance; The second voltage determination module is used to determine the harmonic voltage of the AC bus according to the low-voltage capacitor harmonic voltage and the high-voltage capacitor harmonic voltage.

9. A controller, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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