Iterative compensation synchronous phasor measurement method and device

Abstract

The invention discloses a synchronous phasor measurement method for iterative compensation, and the method comprises the steps: obtaining a target DFT sequence through window function windowing, discrete Fourier transform and averaging, calculating a first cost function after obtaining a cost parameter, and judging whether original data have out-of-band interference or not; then spectrum leakage compensation and cost function setting are carried out according to different conditions, along with the increase of the number of iterations, the cost function value is smaller and smaller, and the measurement precision is higher and higher, so that the optimal value of a cost parameter is obtained, the most accurate fundamental wave and interference parameters are measured, the synchronous phasor measurement precision is improved, and P-level and M-level performance requirements can be met at the same time; synchronous phasor measurement can be completed by only one device, so that the use cost is reduced; in consideration of the influence of out-of-band interference on a fundamental wave phasor, out-of-band interference compensation is carried out; considering that the device is deployed outdoors and the temperature changes drastically, a temperature drift compensation mechanism is added, and the synchronous phasor measurement performance is ensured. In addition, the effect of the measuring device is as above.

Description

Technical Field

[0001] The present invention relates to the technical field of power system measurement, and in particular to an iteratively compensated synchronous phasor measurement method and device. Background Art

[0002] In the process of building new power systems, a large number of power electronic devices and nonlinear loads are invested, and distributed new energy sources are continuously connected. The interference problem of modern power grids is becoming increasingly serious, and the operating environment is becoming more complex. Synchronous phasor measurement technology can obtain accurate absolute time through the global positioning system and measure high-precision synchronous phasor data. It is becoming an important technical means for dynamic security monitoring of power grids and enhancing the observation capability of power grids.

[0003] Existing synchronized phasor measurement algorithms include Discrete Fourier Transform (DFT), least squares method and Kalman filtering. In the development of actual synchronized phasor measurement units, DFT is widely used due to its low computational complexity, easy implementation and full harmonic elimination. However, DFT has many limitations and disadvantages, such as spectrum leakage and fence effect, which seriously affect the performance of synchronized phasor measurement. In addition, most of the existing synchronized phasor measurement algorithms can only meet the requirements of P or M level defined in IEEE STD.C37.118, which means that in actual application, two devices need to be placed at the same time, which also increases the cost of use. Summary of the invention

[0004] The purpose of the present application is to provide a method and device for synchronous phasor measurement with iterative compensation to solve the problem of synchronous phasor measurement performance.

[0005] In order to solve the above technical problems, the present application provides an iterative compensation synchronized phasor measurement method, comprising:

[0006] The voltage and current at a preset time are collected as raw data, a window function that meets the requirements is selected to perform multiple windowing on the raw data, and then a discrete Fourier transform is performed to obtain multiple groups of DFT sequences of the windowed raw data, and the multiple groups of DFT sequences are averaged to obtain the final target DFT sequence;

[0007] Performing a preliminary estimation on the target DFT sequence to obtain a cost parameter to restore a fundamental wave sequence in the target DFT sequence;

[0008] Calculating a first cost function according to the cost parameter, and determining whether the original data has out-of-band interference according to the first cost function:

[0009] If there is no out-of-band interference, spectrum leakage compensation is performed on the last fundamental wave sequence to estimate the fundamental wave parameters;

[0010] Calculate a second cost function according to the target DFT sequence and the fundamental wave sequence;

[0011] Determine whether the second cost function value is less than the accuracy threshold or whether the number of iterations n is greater than the maximum value N of the fundamental wave iteration;

[0012] If yes, then stop the compensation; if no, then return to the step of performing spectrum leakage compensation on the last fundamental wave sequence and estimating fundamental wave parameters, and the value of n is increased by one;

[0013] If out-of-band interference exists, separating an interference sequence from the target DFT sequence according to the last fundamental wave sequence, performing spectrum leakage compensation on the interference sequence, and estimating interference parameters;

[0014] Separating a fundamental wave sequence from the target DFT sequence according to the interference parameter, performing spectrum leakage compensation on the fundamental wave sequence, and estimating fundamental wave parameters;

[0015] Calculate a third cost function according to the interference sequence and the fundamental wave sequence;

[0016] Determine whether the third cost function value is less than the accuracy threshold or whether the number of iterations m is greater than the maximum interference iteration value M;

[0017] If yes, stop compensation; if not, return to the step of separating the interference sequence from the target DFT sequence according to the last fundamental wave sequence, performing spectrum leakage compensation on the interference sequence, estimating interference parameters, and increase the value of m by one;

[0018] According to the ambient temperature, the fundamental wave parameter and the interference parameter, respectively, temperature drift compensation is performed on the fundamental wave parameter and the interference parameter to obtain a target fundamental wave parameter and a target interference parameter;

[0019] The target fundamental wave parameter, the target interference parameter and the target time mark are reported to the master station, wherein the target time mark is the average value of the time information collected within a preset time.

[0020] Based on the above embodiment, as a preferred implementation mode, the sequence x'(n) after selecting a window function that meets the requirements to perform multiple windowing on the original data is:

[0021]

[0022] Among them, the first to fifth sections are windowed original data, x(n) represents the nth original data, w(n) represents the window function, and L represents the length of a single section of windowed original data.

[0023] Based on the above embodiment, as a preferred implementation mode, the multiple groups of DFT sequences x'(k) are:

[0024]

[0025]

[0026] Based on the above embodiment, as a preferred implementation mode, the target DFT sequence X(k) is:

[0027] X(k)=average(X′(k)).

[0028] Based on the above embodiment, as a preferred implementation mode, the preliminary estimation of the target DFT sequence to obtain the cost parameter δ to restore the fundamental sequence in the target DFT sequence is specifically:

[0029] Find the maximum sequence k according to the distribution of the target DFT sequence max Location, k max = argmax(X(k)), and obtain the trend factor ε and the cost parameter δ; and the cost parameter δ needs to be determined according to the selection of the specific window function,

[0030] According to the cost parameter δ and the window function type, the fundamental frequency, amplitude and phase are obtained.

[0031] The restored fundamental sequence for:

[0032]

[0033] in, represents the first fundamental wave sequence, represents the positive component of the first fundamental wave sequence, represents the negative component of the first fundamental wave sequence, Indicates the first fundamental amplitude, T total Indicates the preset time.

[0034] It should be further explained that the first cost function c(δ) is:

[0035] Wherein, X(k) represents the target DFT sequence.

[0036] Based on the above embodiment, as a preferred implementation mode, the spectral leakage compensation for the last fundamental wave sequence is specifically performed as follows:

[0037] Here, spec-compens represents spectrum leakage compensation.

[0038] It should be further explained that when there is no out-of-band interference, the fundamental wave parameters are:

[0039]

[0040] The second cost function is:

[0041]

[0042] It should be further noted that when out-of-band interference exists, the interference parameter is:

[0043] Where m is the number of iterations;

[0044] The fundamental wave parameters are:

[0045]

[0046] The third cost function c(δ) is:

[0047]

[0048] In order to solve the above technical problems, the present application also provides an iteratively compensated synchronized phasor measurement device corresponding to the iteratively compensated synchronized phasor measurement method, comprising:

[0049] It includes a collection module, a transformation module, a first compensation module, a second compensation module and a reporting module:

[0050] The acquisition module is used to collect voltage, current and ambient temperature at a preset time. The acquisition module is integrated with a time synchronization module, and the time synchronization module is used to collect time information;

[0051] The transformation module is used to select a window function that meets the requirements to perform discrete Fourier transform on the original data after performing multiple windowing, so as to obtain multiple groups of DFT sequences of the windowed original data, and to average the multiple groups of DFT sequences to obtain the final target DFT sequence;

[0052] The first compensation module is used to perform spectrum leakage compensation on the target DFT sequence;

[0053] The second compensation module is used to perform temperature drift compensation on the fundamental wave parameter and the interference parameter according to the ambient temperature, the fundamental wave parameter and the interference parameter, respectively, to obtain a target fundamental wave parameter and a target interference parameter;

[0054] The reporting module is used to report the target fundamental wave parameter, the target interference parameter and the target time mark to the master station, wherein the target time mark is the average value of the time information collected within a preset time.

[0055] Compared with the prior art, the invention provides an iteratively compensated synchronous phasor measurement method, which obtains the target DFT sequence through window function windowing, discrete Fourier transform and averaging, and calculates the first cost function after obtaining the cost parameter, and then determines whether the original data has out-of-band interference, and then performs spectrum leakage compensation and sets the cost function for different situations. As the number of iterations increases, the cost function value becomes smaller and smaller, and the measurement accuracy becomes higher and higher, so as to obtain the optimal value of the cost parameter, measure the most accurate fundamental wave and interference parameters, improve the synchronous phasor measurement accuracy, and can meet the P-level and M-level performance requirements at the same time, and only one device is needed to complete the synchronous phasor measurement, reducing the use cost; considering the influence of out-of-band interference on the fundamental wave phasor, the signal is compensated for out-of-band interference; considering that the device will be deployed outdoors and there are drastic temperature changes, a temperature drift compensation mechanism is added to ensure the synchronous phasor measurement performance. In addition, the present application also provides an iteratively compensated synchronous measurement device, and the effect is as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solution of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without inventiveness.

[0057] Figure 1 A flow chart of a synchronous phasor measurement method for iterative compensation provided in an embodiment of the present application;

[0058] Figure 2 A schematic structural diagram of a synchronous phasor measurement device for iterative compensation provided in an embodiment of the present application;

[0059] Figure 3 A fundamental signal test result diagram provided in an embodiment of the present application;

[0060] Figure 4 A harmonic distortion experiment result diagram provided in an embodiment of the present application;

[0061] Figure 5 An out-of-band interference experiment result diagram provided in an embodiment of the present application;

[0062] Figure 6 Another fundamental signal experimental result diagram provided in the embodiment of the present application;

[0063] Figure 7 Another harmonic distortion experimental result diagram provided in an embodiment of the present application;

[0064] Figure 8 Another out-of-band interference experiment result diagram provided in an embodiment of the present application.

[0065] In the figure: 201, acquisition module, 2011, time synchronization module, 202, transformation module, 203, first compensation module, 204, second compensation module, 205, reporting module. DETAILED DESCRIPTION

[0066] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0067] The core of the present application is to provide a method and device for synchronous phasor measurement with iterative compensation, which solves the problem of synchronous phasor measurement performance.

[0068] Figure 1 A flow chart of a synchronous phasor measurement method for iterative compensation provided in an embodiment of the present application, Figure 2 A schematic structural diagram of a synchronous phasor measurement device for iterative compensation provided in an embodiment of the present application; Figure 3 This is a fundamental signal test result diagram provided in an embodiment of the present application. Figure 4 A harmonic distortion experiment result diagram provided in an embodiment of the present application is shown in FIG. Figure 5 This is a graph of out-of-band interference experiment results provided by an embodiment of the present application. Figure 6 Another fundamental signal experimental result diagram provided in the embodiment of the present application is shown in FIG. Figure 7 Another harmonic distortion experimental result diagram provided in the embodiment of the present application is shown in FIG. Figure 8 Another out-of-band interference experiment result diagram provided in the embodiment of the present application is shown in FIG. Figures 1 to 8 shown.

[0069] A synchronous phasor measurement method with iterative compensation comprises the following steps:

[0070] S1, collect the voltage and current of the preset time as the original data, select the window function that meets the requirements to perform multiple windowing on the original data, and then perform discrete Fourier transform to obtain multiple groups of DFT sequences of the windowed original data, and average the multiple groups of DFT sequences to obtain the final target DFT sequence.

[0071] S2, preliminarily estimating the target DFT sequence to obtain cost parameters to restore the fundamental sequence in the target DFT sequence;

[0072] S3, calculating a first cost function according to the cost parameter, and determining whether the original data has out-of-band interference according to the first cost function:

[0073] If there is no out-of-band interference, proceed to step S4; if there is out-of-band interference, proceed to step S9;

[0074] S4, performing spectrum leakage compensation on the last fundamental wave sequence and estimating fundamental wave parameters;

[0075] S5, calculating a second cost function according to the target DFT sequence and the fundamental wave sequence;

[0076] S6, determining whether the second cost function value is less than the accuracy threshold or whether the number of iterations n is greater than the maximum value N of the fundamental wave iteration;

[0077] If yes, go to step S7, if no, go to step S8;

[0078] S7, stop compensation;

[0079] S8, return to step S4, and increase the value of n by one;

[0080] S9, separating the interference sequence from the target DFT sequence according to the last fundamental wave sequence, performing spectrum leakage compensation on the interference sequence, and estimating interference parameters;

[0081] S10, separating a fundamental wave sequence from a target DFT sequence according to interference parameters, performing spectrum leakage compensation on the fundamental wave sequence, and estimating fundamental wave parameters;

[0082] S11, calculating a third cost function according to the interference sequence and the fundamental wave sequence;

[0083] S12, determining whether the third cost function value is less than the accuracy threshold or whether the number of iterations m is greater than the maximum interference iteration value M;

[0084] If yes, go to step S13, if no, go to step S14;

[0085] S13, stop compensation;

[0086] S14, return to step S9, and increase the value of m by one;

[0087] S15, performing temperature drift compensation on the fundamental wave parameter and the interference parameter according to the ambient temperature, the fundamental wave parameter and the interference parameter, respectively, to obtain a target fundamental wave parameter and a target interference parameter;

[0088] S16, reporting the target fundamental wave parameters, target interference parameters and target time mark to the master station, wherein the target time mark is the average value of the time information collected within a preset time.

[0089] As a preferred implementation, a window function that meets the requirements is selected to perform multiple windowing on the original data, and the sequence x'(n) is:

[0090]

[0091] Among them, x1(n)-x5(n) represent the first to fifth segments of windowed original data, x(n) represents the nth original data, w(n) represents the window function, and L represents the length of a single segment of windowed original data.

[0092] As a preferred implementation, the multiple groups of DFT sequences x'(k) are:

[0093]

[0094]

[0095] As a preferred implementation, the target DFT sequence X(k) is:

[0096] X(k)=average(X(k)).

[0097] As a preferred implementation, the target DFT sequence is preliminarily estimated to obtain the cost parameter δ to restore the fundamental sequence in the target DFT sequence:

[0098] Find the maximum sequence k according to the distribution of the target DFT sequence max Location, k max = argmax(X(k)), and obtain the trend factor ε and the cost parameter δ; and the cost parameter δ needs to be determined according to the selection of the specific window function,

[0099] According to the cost parameter δ and the window function type, the fundamental frequency, amplitude and phase are obtained.

[0100] The restored fundamental sequence for:

[0101]

[0102] in, represents the first fundamental wave sequence, represents the positive component of the first fundamental wave sequence, represents the negative component of the first fundamental wave sequence, Indicates the first fundamental amplitude, T total Indicates the preset time.

[0103] As a preferred implementation, the first cost function c(δ) is:

[0104] Where X(k) represents the target DFT sequence. The first cost function c(δ) is used to determine whether the original data has out-of-band interference. If the value of the first cost function is less than the out-of-band interference threshold, it means that there is no out-of-band interference and only fundamental wave compensation is required; otherwise, out-of-band interference compensation is required.

[0105] As a preferred implementation, if there is no out-of-band interference, the spectrum leakage compensation for the last fundamental wave sequence is specifically performed as follows:

[0106] Here, spec-compens represents spectrum leakage compensation.

[0107] Find the position k of the maximum sequence according to the distribution of the target DFT sequence X(k) max , find the trend factor ε and cost parameter δ;

[0108] The frequency, amplitude and phase of the target DFT sequence X(k) are obtained according to the cost parameters to complete the spectrum leakage compensation.

[0109] As a preferred implementation, when there is no out-of-band interference, the estimated fundamental wave parameters of the restored input sequence positive frequency, negative frequency sequence and comprehensive sequence are:

[0110]

[0111] The second cost function is:

[0112]

[0113] Preferably, if there is out-of-band interference, the interference sequence is separated from the original DFT sequence according to the last fundamental sequence The spectrum leakage compensation is performed and the interference parameters are:

[0114] Where m is the number of iterations, which is used for counting and is used as a judgment on whether to stop compensation. The value increases by one after each cycle.

[0115] Restore interference sequence positive frequency, negative frequency sequence and comprehensive sequence:

[0116]

[0117] Preferably, when out-of-band interference exists, the fundamental wave parameters are:

[0118] The subscripts i and 0 are used to distinguish interference from fundamental wave. The subscript i indicates interference, and the subscript 0 indicates fundamental wave.

[0119] Restore the input sequence positive frequency, negative frequency sequence and comprehensive sequence:

[0120]

[0121] The third cost function c(δ) is:

[0122]

[0123] E after temperature drift compensation R Indicates the amplitude temperature drift compensation coefficient, E P Indicates the phase temperature drift compensation coefficient:

[0124] Wherein, T represents the ambient temperature.

[0125] If there is no out-of-band interference, the amplitude and phase of the interference are both 0:

[0126] Subscript 0 represents the fundamental wave parameter, subscript i represents the interference parameter, and A and φ represent the amplitude and phase respectively.

[0127] If there is out-of-band interference, the corresponding parameters are as follows

[0128]

[0129] like Figure 2 As shown, a synchronous phasor measurement device with iterative compensation includes an acquisition module 201, a transformation module 202, a first compensation module 203, a second compensation module 204 and a reporting module 205:

[0130] The acquisition module 201 is used to collect the voltage, current and ambient temperature at a preset time, sampling a set of voltage and current values ​​every 78.125us, and sampling the current ambient temperature every 20ms. The acquisition module 201 is integrated with a time synchronization module 2011, which is used to collect time information; the time synchronization module 2011 is implemented by combining the global positioning system and IEEE 1588, and determines the current time according to the precise 1pps second signal rising edge mark (one cycle is 1s, and the rising edge is the mark of the beginning of the current second).

[0131] The transformation module 202 is used to select a window function that meets the requirements to perform multiple windowing on the original data and then perform discrete Fourier transform to obtain multiple groups of DFT sequences of the windowed original data, and average the multiple groups of DFT sequences to obtain the final target DFT sequence;

[0132] A first compensation module 203, configured to perform spectrum leakage compensation on a target DFT sequence;

[0133] The second compensation module 204 is used to perform temperature drift compensation on the fundamental wave parameter and the interference parameter according to the ambient temperature, the fundamental wave parameter and the interference parameter, respectively, to obtain the target fundamental wave parameter and the target interference parameter;

[0134] The reporting module 205 is used to report the target fundamental wave parameters, target interference parameters and target time mark to the master station, wherein the target time mark is the average value of the time information collected within a preset time.

[0135] In order to enable those skilled in the art to better understand the present invention, the present invention is described in detail with specific embodiments below:

[0136] Example 1

[0137] The voltage or current is collected for 500ms to form a discrete sequence x(n) with a length of 5L.

[0138] Use the Hanning window function to window the original data:

[0139]

[0140] x′(n) is subjected to discrete Fourier transform to obtain multiple sets of DFT sequences of windowed original data:

[0141]

[0142] X(k)=average(X′(k)).

[0143] At this point, the maximum sequence k can be found based on the distribution of the target DFT sequence max Location max =argmax(X(k)), find the trend factor ε and cost parameter δ:

[0144]

[0145] According to the cost parameter δ, the fundamental frequency, amplitude and phase are obtained:

[0146]

[0147] Restore the fundamental positive frequency, negative frequency sequence and fundamental sequence:

[0148]

[0149] Calculate the first cost function value:

[0150]

[0151] According to the first cost function value, it is determined whether the original data has out-of-band interference, and the out-of-band interference threshold θ inter It is set to 0.0033. If the first cost function value is less than the out-of-band interference threshold, it means that there is no out-of-band interference and only fundamental wave compensation is required; otherwise, out-of-band interference compensation is required.

[0152] The specific steps of fundamental wave compensation are as follows:

[0153] Spectral leakage compensation for the last fundamental sequence

[0154] Find the position k of the maximum sequence according to the distribution of the target DFT sequence X(k) max , find the trend factor ε and cost parameter δ:

[0155]

[0156] The frequency, amplitude, and phase of the input sequence are obtained according to the cost parameters to complete the spectrum leakage compensation:

[0157]

[0158] Finally, restore the input sequence positive frequency, negative frequency sequence and comprehensive sequence:

[0159]

[0160] Calculate the second cost function value:

[0161]

[0162] If the second cost function value is less than the accuracy threshold θ accur Or the number of iterations n is greater than the maximum value N of the fundamental wave iteration, the compensation stops. Otherwise, repeat the above steps, and add one to n. accur and N are 1e-4 and 2 respectively.

[0163] The specific steps of out-of-band interference compensation are as follows:

[0164] Separate the interference sequence from the original DFT sequence based on the last fundamental sequence Perform spectrum leakage compensation and estimate interference parameters:

[0165]

[0166] Restore interference sequence positive frequency, negative frequency sequence and comprehensive sequence:

[0167]

[0168] According to the interference estimation result, the fundamental wave sequence is separated from the target DFT sequence, spectral leakage compensation is performed on the sequence, and the fundamental wave parameters are estimated:

[0169]

[0170] Restore the input sequence positive frequency, negative frequency sequence and comprehensive sequence:

[0171]

[0172] According to the above results, the third cost function value is calculated:

[0173]

[0174] If the cost function value is less than the accuracy threshold θ accur Or the number of iterations m is greater than the maximum value of interference iteration M, the compensation stops. Otherwise, repeat the above steps, increase the value of m by one, θ accur The values ​​of and M are 1e-4 and 28 respectively.

[0175] Finally, temperature drift compensation is performed to compensate the amplitude and phase of the fundamental wave and interference according to the temperature of the placement location. After temperature drift compensation, the target fundamental wave parameter E R and target interference parameter E P They are:

[0176]

[0177] If there is no out-of-band interference, the amplitude and phase of the interference are both 0:

[0178]

[0179] If there is out-of-band interference, the corresponding parameters are as follows:

[0180]

[0181] Next, we conducted tests based on the IEEE Std C37.118 measurement standard, collecting signals from low-temperature, normal, and high-temperature environments for simulation testing. The signals were specifically three types of signals with different frequencies: those containing only fundamental waves, those with harmonics, and those with out-of-band interference.

[0182] 1. Only includes fundamental signal test

[0183] The signal model x(t) is:

[0184] Among them, t represents time t, and the value range of f0 is 45-55Hz.

[0185] according to Figure 3 It can be seen that the TVE, FE, and RFE errors are all within the allowable range of class p and class m. TVE, FE, and RFE represent total vector error, frequency error, and frequency change rate error, respectively. This meaning is defined by the IEEE STD.C37.118 standard.

[0186] 2. Test for harmonic distortion

[0187] The signal model x(t) is:

[0188]

[0189] where n iis the harmonic number, the test range is 2-50 harmonics, according to Figure 4 It can be seen that the TVE, FE, and RFE errors are all within the allowable range of class p and class m.

[0190] 3. Test for out-of-band interference

[0191] The signal model x(t) is:

[0192]

[0193] where f i The out-of-band interference frequency, the test range is 2-50 harmonics, according to Figure 5 It can be seen that the TVE, FE, and RFE errors are all within the allowable range of class p and class m.

[0194] Table 1 shows the comparison of the maximum error values ​​under all temperature conditions with the requirements of Class P and Class M. It can be seen from the table that all maximum error values ​​are far lower than the standard requirements.

[0195] Table 1 Hanning window error statistics

[0196]

[0197] Example 2

[0198] The voltage or current is collected for 500ms to form a discrete sequence x(n) with a length of 5L.

[0199] Use a sine window function to window the original data:

[0200]

[0201] x(n) is subjected to discrete Fourier transform to obtain multiple sets of DFT sequences of windowed original data:

[0202]

[0203] X(k)=average(X′(k))

[0204] At this point, the maximum sequence position k can be found according to the distribution of the target DFT sequence max =argmax(X(k)), find the trend factor ε and cost parameter δ:

[0205]

[0206] According to the cost parameters, the fundamental frequency, amplitude and phase are obtained:

[0207]

[0208] Restore the fundamental positive frequency, negative frequency sequence and fundamental sequence:

[0209]

[0210] Calculate the first cost function value:

[0211]

[0212] According to the first cost function value, it is determined whether there is out-of-band interference, and the out-of-band interference threshold θ inter It is set to 0.0033. If the first cost function value is less than the out-of-band interference threshold, it means that there is no out-of-band interference and only fundamental wave compensation is required; otherwise, out-of-band interference compensation is required.

[0213] The specific steps of fundamental wave compensation are as follows:

[0214] Spectral leakage compensation for the last fundamental sequence

[0215] Find the position k of the maximum sequence according to the distribution of the target DFT sequence X(k) max , find the trend factor ε and cost parameter δ:

[0216]

[0217] The frequency, amplitude, and phase of the input sequence are obtained according to the cost parameters to complete the spectrum leakage compensation:

[0218]

[0219] Finally, restore the input sequence positive frequency, negative frequency sequence and comprehensive sequence:

[0220]

[0221] Calculate the second cost function value:

[0222]

[0223] If the second cost function value is less than the accuracy threshold θ accur Or the number of iterations n is greater than the maximum value N of the fundamental wave iteration, the compensation stops. Otherwise, repeat the above steps, and add one to n. accur and N are 1e-4 and 2 respectively.

[0224] The specific steps of out-of-band interference compensation are as follows:

[0225] Separate the interference sequence from the original DFT sequence based on the last fundamental sequence Perform spectrum leakage compensation and estimate interference parameters:

[0226]

[0227] Restore interference sequence positive frequency, negative frequency sequence and comprehensive sequence:

[0228]

[0229] According to the interference estimation result, the fundamental wave sequence is separated from the target DFT sequence, spectral leakage compensation is performed on the sequence, and the fundamental wave parameters are estimated:

[0230]

[0231] Restore the input sequence positive frequency, negative frequency sequence and comprehensive sequence:

[0232]

[0233] According to the above results, the third cost function value is calculated:

[0234]

[0235] If the third cost function value is less than the accuracy threshold θ accur Or the number of iterations m is greater than the maximum value of interference iteration M, the compensation stops. Otherwise, repeat the above steps, increase the value of m by one, θ accur The values ​​of and M are 1e-4 and 16 respectively.

[0236] Finally, temperature drift compensation is performed to compensate the amplitude and phase of the fundamental wave and interference according to the temperature of the placement location. After temperature drift compensation, the target fundamental wave parameter E R and target interference parameter E P They are:

[0237]

[0238] If there is no out-of-band interference, the amplitude and phase of the interference are both 0:

[0239]

[0240] If there is out-of-band interference, the corresponding parameters are as follows:

[0241]

[0242] Next, we conducted tests based on the IEEE Std C37.118 measurement standard, collecting signals from low-temperature, normal, and high-temperature environments for simulation testing. The signals were specifically three types of signals with different frequencies: those containing only fundamental waves, those with harmonics, and those with out-of-band interference.

[0243] 1. Only includes fundamental signal test

[0244] The signal model x(t) is:

[0245] Among them, t represents time t, and the value range of f0 is 45-55Hz.

[0246] according to Figure 6 It can be seen that the errors of TVE, FE and RFE are all within the allowable range of class p and class m. TVE, FE and RFE represent the total vector error, frequency error and frequency change rate error respectively.

[0247] 2. Test for harmonic distortion

[0248] The signal model x(t) is:

[0249]

[0250] where n i is the harmonic number, the test range is 2-50 harmonics, according to Figure 7 It can be seen that the errors of TVE, FE, and RFE are all within the allowable range of class p and class m.

[0251] 3. Test for out-of-band interference

[0252] The signal model x(t) is:

[0253]

[0254] where f i The out-of-band interference frequency, the test range is 2-50 harmonics, according to Figure 8 It can be seen that the TVE, FE, and RFE errors are all within the allowable range of class p and class m.

[0255] Table 2 shows the comparison of the maximum error values ​​under all temperature conditions with the requirements of Class P and Class M. It can be seen from the table that all maximum error values ​​are far lower than the standard requirements.

[0256] Table 2 Sine window error statistics

[0257]

[0258] The iterative compensation synchronous phasor measurement method provided in this embodiment includes at least the following beneficial effects: 1. Through spectrum leakage compensation and setting the cost function, as the number of iterations increases, the cost function value becomes smaller and smaller, and the measurement accuracy becomes higher and higher, so as to obtain the optimal value of the cost parameter, measure the most accurate fundamental wave and interference parameters, improve the synchronous phasor measurement accuracy, and can simultaneously meet the P-level and M-level performance requirements defined in IEEE STD.C37.118; 2. Considering the application of two typical window functions, Hanning and sine, different calculation formulas and rules are proposed for different window functions; 3. Considering the influence of out-of-band interference on the fundamental wave phasor, the signal is compensated for out-of-band interference; 4. Considering that the device will be deployed outdoors and there are drastic temperature changes, a temperature drift compensation mechanism is added. The synchronous phasor measurement performance is ensured, and only one device is needed to complete the synchronous phasor measurement, reducing the use cost.

[0259] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art disclosed in the present application. The specification and examples are to be regarded as exemplary only, and the true scope of the present application is indicated by the claims.

[0260] It should be understood that the present application is not limited to the precise structure described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The above-described embodiments of the present application do not constitute a limitation on the scope of protection of the present application.

Claims

1. A synchronous phasor measurement method with iterative compensation, characterized in that: Applicable to any synchronized phasor measurement device, including: Collect the voltage and current of the preset time as raw data, and collect the ambient temperature and time information; Select a window function that meets the requirements to perform multiple windowing on the original data and then perform discrete Fourier transform to obtain multiple groups of DFT sequences of the windowed original data, average the multiple groups of DFT sequences to obtain the final target DFT sequence; Performing a preliminary estimation on the target DFT sequence to obtain a cost parameter to restore a fundamental wave sequence in the target DFT sequence; Calculating a first cost function according to the cost parameter, and determining whether the original data has out-of-band interference according to the first cost function: If there is no out-of-band interference, spectrum leakage compensation is performed on the last fundamental wave sequence to estimate the fundamental wave parameters; Calculate a second cost function according to the target DFT sequence and the fundamental wave sequence; Determine whether the second cost function value is less than the accuracy threshold or whether the number of iterations n is greater than the maximum value N of the fundamental wave iteration; If yes, then stop the compensation; if no, then return to the step of performing spectrum leakage compensation on the last fundamental wave sequence and estimating fundamental wave parameters, and the value of n is increased by one; If out-of-band interference exists, separating an interference sequence from the target DFT sequence according to the last fundamental wave sequence, performing spectrum leakage compensation on the interference sequence, and estimating interference parameters; Separating a fundamental wave sequence from the target DFT sequence according to the interference parameter, performing spectrum leakage compensation on the fundamental wave sequence, and estimating fundamental wave parameters; Calculate a third cost function according to the interference sequence and the fundamental wave sequence; Determine whether the third cost function value is less than the accuracy threshold or whether the number of iterations m is greater than the maximum interference iteration value M; If yes, stop compensation; if not, return to the step of separating the interference sequence from the target DFT sequence according to the last fundamental wave sequence, performing spectrum leakage compensation on the interference sequence, estimating interference parameters, and increase the value of m by one; According to the ambient temperature, the fundamental wave parameter and the interference parameter, respectively, temperature drift compensation is performed on the fundamental wave parameter and the interference parameter to obtain a target fundamental wave parameter and a target interference parameter; The target fundamental wave parameter, the target interference parameter and the target time mark are reported to the master station, wherein the target time mark is the average value of the time information collected within a preset time.

2. The iteratively compensated synchronized phasor measurement method according to claim 1, characterized in that: The sequence x'(n) after selecting the window function that meets the requirements to perform multiple windowing on the original data is: Wherein, x1(n)-x5(n) represents the first to fifth segments of windowed original data, x(n) represents the nth original data, w(n) represents the window function, and L represents the length of a single segment of windowed original data.

3. The iteratively compensated synchronized phasor measurement method according to claim 2, characterized in that: The multiple groups of DFT sequences x'(k) are: in, represents the normalization factor, L represents the same as above, N represents the original data length, represents the rotation factor.

4. The iteratively compensated synchronized phasor measurement method according to claim 3, characterized in that: The target DFT sequence X(k) is: X(k)=average(X′(k)).

5. The iteratively compensated synchronized phasor measurement method according to claim 4, characterized in that: The preliminary estimation of the target DFT sequence to obtain the cost parameter δ to restore the fundamental sequence in the target DFT sequence is specifically: Find the maximum sequence k according to the distribution of the target DFT sequence max Location, k max = argmax(X(k)), and obtain the trend factor ε and the cost parameter δ; and the cost parameter δ needs to be determined according to the selection of the specific window function, According to the cost parameter δ and the window function type, the fundamental frequency, amplitude and phase are obtained. The restored fundamental sequence for: in, represents the first fundamental wave sequence, represents the positive component of the first fundamental wave sequence, represents the negative component of the first fundamental wave sequence, Indicates the first fundamental amplitude, T total Indicates the preset time.

6. The iteratively compensated synchronized phasor measurement method according to claim 5, characterized in that: The first cost function c(δ) is: Wherein, X(k) represents the target DFT sequence.

7. The iteratively compensated synchronized phasor measurement method according to claim 1, characterized in that: The spectral leakage compensation for the last fundamental wave sequence is specifically performed as follows: Here, spec-compens represents spectrum leakage compensation.

8. The iteratively compensated synchronized phasor measurement method according to claim 7, characterized in that: When there is no out-of-band interference, the fundamental wave parameters are: The second cost function is:

9. The iteratively compensated synchronized phasor measurement method according to claim 1, characterized in that: When there is out-of-band interference, the interference parameter is: Where m is the number of iterations; The fundamental wave parameters are: The third cost function c(δ) is:

10. A synchronous phasor measurement device with iterative compensation, characterized in that: It includes a collection module, a transformation module, a first compensation module, a second compensation module and a reporting module: The acquisition module is used to collect voltage, current and ambient temperature at a preset time. The acquisition module is integrated with a time synchronization module, and the time synchronization module is used to collect time information; The transformation module is used to select a window function that meets the requirements to perform discrete Fourier transform on the original data after performing multiple windowing, so as to obtain multiple groups of DFT sequences of the windowed original data, and to average the multiple groups of DFT sequences to obtain the final target DFT sequence; The first compensation module is used to perform spectrum leakage compensation on the target DFT sequence; The second compensation module is used to perform temperature drift compensation on the fundamental wave parameter and the interference parameter according to the ambient temperature, the fundamental wave parameter and the interference parameter, respectively, to obtain a target fundamental wave parameter and a target interference parameter; The reporting module is used to report the target fundamental wave parameter, the target interference parameter and the target time mark to the master station, wherein the target time mark is the average value of the time information collected within a preset time.

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