Method for measuring broadband phasor of power system

Abstract

The invention relates to a measurement method for a broadband phasor of a power system. The measurement method comprises the following steps: acquiring a direct current side oscillation component of the power system; based on the direct-current side oscillation component, calculating and obtaining an alternating-current side oscillation component of the power system by adopting a first calculation relation; the first calculation relation is a calculation relation between the direct current side oscillation component and the alternating current side oscillation component; based on the alternating current side oscillation component, a second calculation relation is adopted to calculate and obtain a broadband phasor of the power system; the second calculation relation is a calculation relation between the alternating current side oscillation component and the broadband phasor; the DC-side oscillation component is smaller than the AC-side oscillation component. Compared with the mode of directly observing the alternating current side information and then obtaining the alternating current side oscillation component through calculation, the mode of observing the direct current side information, obtaining the direct current side oscillation component and then obtaining the alternating current side oscillation component through the first calculation relation has the advantages that the required time is shorter under the condition that the measurement precision is not changed; therefore, phasor measurement time can be reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power system operation monitoring, and particularly to a method for measuring broadband phasors of a power system. Background Art

[0002] In recent years, Modular Multilevel Converter High-Voltage DC (MMC-HVDC) transmission systems and AC-DC conversion of wind and solar power generation have been increasingly widely used in the power transmission and power generation projects of power systems, and new power systems exhibit the characteristics of AC-DC hybrid connection. Broadband phasor measurement technology is of great significance for the monitoring and relay protection of power systems. Traditional phasor measurement technology selects a relatively long observation time window to ensure the accuracy of phasor measurement, which increases the time for phasor measurement. Therefore, how to reduce the time for phasor measurement while ensuring the accuracy of phasor measurement has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0003] To solve the above technical problems or at least partially solve the above technical problems, the present disclosure provides a method for measuring broadband phasors of a power system.

[0004] The present disclosure provides a method for measuring broadband phasors of a power system, including: obtaining the DC-side oscillation component of the power system; based on the DC-side oscillation component, calculating and obtaining the AC-side oscillation component of the power system by using a first calculation relationship; the first calculation relationship is the calculation relationship between the DC-side oscillation component and the AC-side oscillation component; based on the AC-side oscillation component, calculating and obtaining the broadband phasor of the power system by using a second calculation relationship; the second calculation relationship is the calculation relationship between the AC-side oscillation component and the broadband phasor; wherein, the DC-side oscillation component is less than the AC-side oscillation component.

[0005] Optionally, the DC-side oscillation component includes the DC-side oscillation frequency; obtaining the DC-side oscillation component of the power system includes: based on the measurement algorithm of the digital processing unit, converting the DC-side electrical signal expression into a DC-side phasor expression; obtaining the DC-side oscillation frequency based on the DC-side phasor expression.

[0006] Optionally, the digital processing unit includes a window function; the window function is used to convert the DC-side electrical signal expression into a DC-side phasor expression.

[0007] Optionally, the window function includes a Kaiser window function.

[0008] Optionally, the DC-side electrical signal expression is:

[0009]

[0010] where A1 is the amplitude of the DC component of the electrical signal; A g is the amplitude of the oscillating component on the DC side; σ is the damping factor; f g is the oscillation frequency on the DC side; is the initial phase of the oscillating component on the DC side.

[0011] The phasor expression on the DC side is:

[0012]

[0013] where n ∈ [-N, N], 2N + 1 is the number of sampling points; h(n) is the expression of the digital processing unit; w(n) is the time-domain expression of the window function; the phasor expression on the DC side is used to calculate and obtain the estimated formula for the oscillation frequency on the DC side; the estimated formula for the oscillation frequency on the DC side is used to obtain the oscillation frequency on the DC side.

[0014] Optionally, the estimated formula for the oscillation frequency on the DC side is:

[0015]

[0016] where T s = 1 / f s is the sampling interval, f s is the sampling frequency.

[0017] Optionally, the broadband phasor includes a corrected frequency; before calculating and obtaining the broadband phasor of the power system using the second calculation relationship based on the oscillating frequency component on the AC side, the method further includes: obtaining the dynamic phasor on the AC side based on the electrical signal expression on the AC side; obtaining the main oscillating component of the signal on the AC side according to the dynamic phasor on the AC side; constructing an estimated formula for the corrected frequency according to the main oscillating component expression and the first derivative of the main oscillating component expression; where the second calculation relationship includes the estimated formula for the corrected frequency; obtaining the corrected frequency based on the estimated formula for the corrected frequency.

[0018] Optionally, the broadband phasor further includes an oscillation amplitude; before calculating and obtaining the broadband phasor of the power system using the second calculation relationship based on the oscillating component on the AC side, the method further includes: constructing a vector estimation formula according to the electrical signal expression on the AC side and the dynamic phasor on the AC side; where the second calculation relationship further includes the vector estimation formula; obtaining the oscillation amplitude based on the vector estimation formula and the main oscillating component expression.

[0019] Optionally, constructing a vector estimation formula according to the electrical signal expression on the AC side and the dynamic phasor on the AC side includes: constructing a vector estimation formula using the weighted least squares method according to the electrical signal expression on the AC side and the dynamic phasor on the AC side.

[0020] Optionally, the DC-side oscillation component includes the DC-side oscillation frequency; the AC-side oscillation component includes the AC-side main oscillation frequency and the AC-side coupled oscillation frequency;

[0021] The first calculation relationship includes:

[0022] fd = f0 + |fg

[0023] and

[0024] fp = |fg| - f0

[0025] where, f d is the AC-side main oscillation frequency, f g is the DC-side oscillation frequency, f 0 is the fundamental frequency of the power system, f p is the AC-side coupled oscillation frequency.

[0026] The present disclosure provides a method for measuring wide-band phasors of a power system. Since the DC-side signal of the power system is converted into an AC-side signal through a converter in the power system, there is a connection between the oscillation component on the AC side and the oscillation component on the DC side. Therefore, by obtaining the DC-side oscillation component of the power system and using the first calculation relationship between the DC-side oscillation component and the AC-side oscillation component, the AC-side oscillation component of the power system can be obtained. Furthermore, based on the AC-side oscillation component, the wide-band phasors of the power system can be obtained through the second calculation relationship. Since the DC-side oscillation component is smaller than the AC-side oscillation component, the present disclosure observes the DC-side information to obtain the DC-side oscillation component, and then obtains the AC-side oscillation component through the first calculation relationship. Compared with the method of directly observing the AC-side information and then calculating to obtain the AC-side oscillation component, the time required is shorter while ensuring the measurement accuracy remains unchanged. Therefore, the time for phasor measurement can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 is a schematic flowchart of a method for measuring wide-band phasors of a power system provided by an embodiment of the present disclosure.

[0029] Figure 2 is a schematic flowchart of a preferred method for measuring wide-band phasors of a power system provided by an embodiment of the present disclosure.

[0030] Figure 3Schematic diagram of the structure of a measurement system for wide - frequency phasors of a power system provided by an embodiment of the present disclosure. Detailed implementation manners

[0031] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In the following detailed description, many specific details are set forth in order to provide a comprehensive understanding of the present application. However, it will be apparent to those skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present application by showing examples of the present application.

[0032] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The embodiments will be described in detail below with reference to the drawings.

[0033] In recent years, modular multilevel converter high - voltage direct - current (MMC - HVDC) transmission systems and AC - DC conversion of wind and solar power generation have been increasingly widely used in the power transmission and power generation projects of power systems. The new - type power system shows the characteristics of AC - DC hybrid connection. In the related art, the phasor measurement of the electrical signals of the AC - DC hybrid system directly analyzes the AC side, collects the AC signals to obtain the AC signal information, then uses the phasor measurement algorithm to extract the AC signal characteristics, and finally obtains the phasor parameters of the measured signal. If f 0 represents the fundamental frequency of the power system, and f d represents the main oscillation frequency of the AC side, then the coupled oscillation frequency of the AC side can be expressed as 2f 0 -f d . Therefore, the oscillation components on the AC side appear at the main oscillation frequency f d and the coupled oscillation frequency 2f 0 -f d . Since the mutual interference between the frequency components on the AC side is relatively obvious, a long observation time window is required to ensure the accuracy of phasor measurement.

[0034] Moreover, since the AC - side signal is obtained by commutation of the DC - side signal through the converter, some information in the AC - side signal will also be reflected in the DC - side signal. It has been found by the inventors that when there are oscillation components on the AC side, there are also corresponding oscillation components on the DC side. The oscillation components on the DC side appear in the form of the DC - side oscillation frequency, and the DC - side oscillation frequency is f 0 -f d . That is, the main oscillation frequency f d and the coupled oscillation frequency 2f 0 -f d on the AC side only appear at the oscillation frequency f 0 -f dIt can be seen that, when ensuring the accuracy of phasor measurement remains unchanged, since the oscillation component on the DC side is smaller than that on the AC side, it means that when observing the information on the DC side, compared with observing the information on the AC side, a shorter observation time window can be used for phasor parameter estimation.

[0035] Figure 1 The flowchart of a method for measuring broadband phasors of a power system provided by the present disclosure is shown in Figure 1 As shown, the measurement method includes: S110 - S130.

[0036] S110. Obtain the oscillation component on the DC side of the power system.

[0037] S120. Based on the oscillation component on the DC side, calculate and obtain the oscillation component on the AC side of the power system by using a first calculation relationship. The first calculation relationship is the calculation relationship between the oscillation component on the DC side and the oscillation component on the AC side.

[0038] S130. Based on the oscillation component on the AC side, calculate and obtain the broadband phasor of the power system by using a second calculation relationship. The second calculation relationship is the calculation relationship between the oscillation component on the AC side and the broadband phasor.

[0039] Wherein, the oscillation component on the DC side is smaller than the oscillation component on the AC side.

[0040] Since the AC - side signal of the power system is obtained by transforming the DC - side signal through a converter, there is a certain calculation relationship between the oscillation component on the AC side and the oscillation component on the DC side. And because the oscillation component on the DC side is smaller than the oscillation component on the AC side, the time required to observe the information on the DC side is less than the time required to observe the information on the AC side. Therefore, when it is necessary to calculate and obtain the broadband phasor of the power system through the oscillation component on the AC side, the oscillation component on the DC side can be obtained and then the oscillation component on the AC side can be calculated through calculation, which can shorten the acquisition time of the oscillation component on the AC side.

[0041] In S110, first, the electrical signal on the DC side of the power system is obtained. The electrical signal on the DC side can be the current or voltage on the DC side. The digital processing unit processes the electrical signal on the DC side, and finally obtains the oscillation component on the DC side.

[0042] In S120, after obtaining the DC-side oscillation component, since there is a first calculation relationship between the DC-side oscillation component and the AC-side oscillation component, the first calculation relationship is used to calculate the DC-side oscillation component to obtain the AC-side oscillation component. Since the time required to observe the DC-side information is less than the time required to observe the AC-side information, the present disclosure observes the DC-side signal of the current system to obtain the DC-side oscillation component, and then calculates the AC-side oscillation component, realizing the rapid acquisition of the AC-side oscillation component.

[0043] In S130, after obtaining the AC-side oscillation component, the second calculation relationship is used to calculate the AC-side oscillation component to obtain the wide-frequency phasor of the power system. Since the acquisition time of the AC-side oscillation component is shortened, the time for obtaining the wide-frequency phasor is also shortened, thereby realizing the rapid acquisition of the wide-frequency phasor.

[0044] The present disclosure observes the DC-side information to obtain the DC-side oscillation component, and then obtains the AC-side oscillation component through the first calculation relationship. Compared with the method of directly observing the AC-side information and then calculating to obtain the AC-side oscillation component, the time required is shorter under the condition of ensuring the measurement accuracy unchanged. Therefore, the AC-side oscillation component can be obtained quickly and accurately, and the overall time for obtaining the wide-frequency phasor can also be shortened. Furthermore, the wide-frequency phasor can be obtained in a shorter time under the condition of ensuring the measurement accuracy unchanged, improving the acquisition efficiency of the wide-frequency phasor.

[0045] In some embodiments, the DC-side oscillation component includes the DC-side oscillation frequency; obtaining the DC-side oscillation component of the power system includes:

[0046] Based on the measurement algorithm of the digital processing unit, converting the DC-side electrical signal expression into a DC-side phasor expression; obtaining the DC-side oscillation frequency based on the DC-side phasor expression.

[0047] Exemplarily, before obtaining the DC-side phasor expression, it is necessary to obtain the DC-side electrical signal expression of the power system, and then through the measurement algorithm of the digital processing unit, convert the DC-side electrical signal expression into a DC-side phasor expression. The digital processing unit can be, for example, an FIR filter, and the measurement algorithm of the digital processing unit is the FIR filter phasor measurement method. According to the FIR filter phasor measurement method, the DC-side electrical signal expression is transformed into a DC-side phasor expression. According to the DC-side phasor expression, the frequency estimation formula of the DC-side oscillation frequency can be obtained, and then the DC-side oscillation frequency can be obtained.

[0048] The present disclosure observes the DC-side information of the power system to obtain the DC-side oscillation frequency, and then calculates the DC-side oscillation frequency through the measurement algorithm of the digital processing unit. Since the performance parameters of the digital processing unit are adjustable, the operating performance of the digital processing unit can be improved, thereby improving the accuracy of obtaining the DC oscillation frequency. After obtaining the DC-side oscillation frequency, the AC-side oscillation component is calculated according to the first calculation relationship. Without changing the measurement accuracy, since the time required for observing the DC-side information is shorter than that for observing the AC-side information, the AC-side oscillation component can be obtained accurately and quickly, and then the overall time for obtaining the wide-frequency phasor can be shortened, realizing obtaining the wide-frequency phasor in a shorter time without changing the measurement accuracy, and improving the acquisition efficiency of the wide-frequency phasor.

[0049] It should be noted that the digital processing unit can also be other digital processing units that can transform the DC-side electrical signal expression into the DC-side phasor expression in addition to the FIR filter, and no specific limitation is made here.

[0050] In some embodiments, the digital processing unit includes a window function; the window function is used to convert the DC-side electrical signal expression into the DC-side phasor expression.

[0051] Exemplarily, the digital processing unit can be, for example, an FIR filter, and the window function can include a Kaiser window function. The present disclosure adds a window function to the digital processing unit to better adjust and improve the performance of the digital processing unit. Moreover, the Kaiser window function can autonomously adjust the main lobe and sidelobe widths. Therefore, by adopting the Kaiser window function, the present disclosure can adjust the parameters of the window function, thereby regulating the window function bandwidth and improving the amplitude-frequency characteristics.

[0052] It should be noted that the digital processing unit can also include other window functions in addition to the Kaiser window function, and no specific limitation is made here.

[0053] In some embodiments, the DC-side electrical signal expression is obtained on the DC side of the power system:

[0054]

[0055] where A 1 is the amplitude of the DC component of the electrical signal; A g is the amplitude of the DC-side oscillation component; σ is the damping factor; f g is the DC-side oscillation frequency; is the initial phase of the DC-side oscillation component.

[0056] Taking the digital processing unit as an FIR filter as an example for introduction, the measurement algorithm of the digital processing unit is the phasor measurement method of the FIR filter. According to the phasor measurement method of the FIR filter, the DC-side electrical signal expression is transformed into:

[0057]

[0058] where \(n\in[-N,N]\), \(n\) is the time window, and \(2N + 1\) is the number of sampling points of the FIR filter; \(p\) g is the phasor of the DC-side oscillation component, and \(p\) g * is the conjugate component corresponding to the phasor of the DC-side oscillation component; \(T\) s \(= 1 / f\) s is the sampling interval of the FIR filter, and \(f\) s is the sampling frequency of the FIR filter. The expression of the phasor \(p\) g of the DC-side oscillation component is:

[0059]

[0060] Moreover, the digital processing unit is an FIR filter, and the window function is the Kaiser window function. Therefore, the expression of the windowed FIR filter is:

[0061]

[0062] where \(f\) c is the center frequency of the FIR filter; \(w(n)\) is the time-domain expression of the Kaiser window function. The time-domain expression of the Kaiser window function is:

[0063]

[0064] where \(\beta\) is the adjustable parameter of the Kaiser window function. By adjusting the \(\beta\) parameter of the Kaiser window function, the bandwidth of the Kaiser window function can be regulated and the amplitude-frequency characteristic can be improved. The expression of \(E\) 0 (x) is specifically:

[0065]

[0066] Thus, according to the above expressions, the DC-side phasor expression can be derived as:

[0067]

[0068] The DC-side phasor expression is used to calculate and obtain the DC-side oscillation frequency estimation formula; the DC-side oscillation frequency estimation formula is used to obtain the DC-side oscillation frequency.

[0069] Therefore, according to the DC-side vector expression, the DC-side oscillation frequency estimation formula can be obtained as:

[0070]

[0071] According to the DC-side oscillation frequency estimation formula, the DC-side oscillation frequency |fg| can be obtained. After obtaining the DC-side oscillation frequency |fg|, the present disclosure obtains the AC-side oscillation component through the first calculation relationship. Compared with the method of directly observing the AC-side information and then obtaining the AC-side oscillation component through calculation, the time required is shorter under the condition of ensuring the same measurement accuracy. Therefore, the AC-side oscillation component can be obtained quickly and accurately, and the overall time for obtaining the broadband phasor can be shortened. Furthermore, it is possible to obtain the broadband phasor in a shorter time while ensuring the same measurement accuracy, improving the acquisition efficiency of the broadband phasor.

[0072] It should be noted that the digital processing unit can also be other digital processing units that can transform the DC-side electrical signal expression into the DC-side phasor expression in addition to the FIR filter, and no specific limitation is made here.

[0073] It should be noted that the digital processing unit can also include other window functions in addition to the Kaiser window function, and no specific limitation is made here.

[0074] In some embodiments, the broadband phasor includes a corrected frequency; before calculating and obtaining the broadband phasor of the power system based on the AC-side oscillation frequency component using the second calculation relationship, the method further includes: obtaining the AC-side dynamic phasor based on the AC-side electrical signal expression; obtaining the main oscillation component of the AC-side signal according to the AC-side dynamic phasor; constructing a corrected frequency estimation formula according to the main oscillation component expression and the first derivative of the main oscillation component expression; wherein, the second calculation relationship includes the corrected frequency estimation formula; obtaining the corrected frequency based on the corrected frequency estimation formula.

[0075] Exemplarily, obtain the AC-side electrical signal expression:

[0076]

[0077] where A q represents the initial amplitude of the q-component of the AC-side signal; represents the initial phase of the q-component of the AC-side signal, and σ is the damping factor. The q-component can be any one of the 0-component, d-component, and p-component. The 0-component is the fundamental frequency component, the d-component is the main oscillation component, and the p-component is the coupling frequency component.

[0078] Perform transformation processing on the AC-side electrical signal expression,

[0079] Set the fundamental frequency phasor expression as:

[0080]

[0081] The phasor expression of the main oscillation frequency on the AC side is as follows:

[0082]

[0083] The phasor expression of the coupled oscillation frequency is as follows:

[0084]

[0085] Therefore, the expression of the transformed AC-side electrical signal can be further expressed as:

[0086]

[0087] Due to the effect of the damping factor σ, the amplitudes of the oscillation components and their coupled components on the AC side are dynamically changing. Based on the frequency-domain sampling theorem, the sum of multiple imaginary exponential functions within a finite observation time window can be used to approximately represent the AC-side dynamic phasor. Therefore, the AC-side dynamic phasor can be obtained based on the expression of the AC-side electrical signal:

[0088]

[0089] where k ∈ Z, t ∈ [-T, T], 2T is the observation window length, 2K is the order; Δf is the frequency-domain sampling interval; G q,k is the sample of the q component in the frequency domain.

[0090] According to the AC-side dynamic phasor, the main oscillation component of the AC-side signal at t = 0 can be obtained, and the expression of the main oscillation component is:

[0091]

[0092] The first derivative of the expression of the main oscillation component is:

[0093]

[0094] Based on the frequency measurement estimation formula defined in the relevant standards of the power system industry IEEE / IEC 60255-118-1, the corrected frequency can be estimated by integrating the expression of the main oscillation component and the first derivative of the expression of the main oscillation component. Therefore, according to the expression of the main oscillation component and the first derivative of the expression of the main oscillation component, a corrected frequency estimation formula is constructed, and the corrected frequency estimation formula is:

[0095]

[0096] The corrected frequency can be estimated according to the corrected frequency estimation formula. Moreover, since the corrected frequency can be used to correct the AC-side oscillation frequency calculated through the first calculation relationship based on the DC-side oscillation frequency, therefore, after obtaining the corrected frequency After that, the coupling frequency can also be calculated through the frequency relationship of the frequency coupling effect, that is

[0097]

[0098] In some embodiments, the wideband phasor further includes an oscillation amplitude; before calculating and obtaining the wideband phasor of the power system by using the second calculation relationship based on the AC-side oscillation component, the method further includes: constructing a vector estimation formula according to the AC-side electrical signal expression and the AC-side dynamic phasor; wherein, the second calculation relationship further includes the vector estimation formula; based on the vector estimation formula and the main oscillation component expression, the oscillation amplitude is obtained.

[0099] Exemplarily, it may be, for example, to construct a vector estimation formula by using the weighted least squares method. Therefore, constructing a vector estimation formula according to the AC-side electrical signal expression and the AC-side dynamic phasor includes: constructing a vector estimation formula by using the weighted least squares method according to the AC-side electrical signal expression and the AC-side dynamic phasor.

[0100] According to the transformed AC-side electrical signal expression:

[0101]

[0102] And the AC-side dynamic phasor:

[0103]

[0104] The matrix expression can be obtained:

[0105]

[0106] Wherein, S is a column vector containing 2N + 1 samples of S 2 (t); E is a matrix containing the sample information of and its conjugate, G q,k can be any one of G 0,k , G d,k and G p,k ; the vector G is a column vector containing the phasor sample G q,k .

[0107] Estimate the vector G by using the weighted least squares method to construct a vector estimation formula:

[0108]

[0109] Wherein, H represents the Hermitian operator; W is a weight matrix containing the AC-side window function information. Perform a modulus operation on the AC-side dynamic phasor, and it can be known that the value corresponding to the oscillation amplitude at t = 0 is the result of the main oscillation component expression Therefore, it can be calculated through the vector estimation formula Thus, the calculation of the oscillation amplitude is achieved.

[0110] It should be noted that constructing the vector estimation formula by using the weighted least squares method is only an example, and other methods can also be used to obtain the vector estimation formula, which is not specifically limited herein.

[0111] In some embodiments, the DC-side oscillation component includes the DC-side oscillation frequency; the AC-side oscillation component includes the AC-side main oscillation frequency and the AC-side coupled oscillation frequency.

[0112] The first calculation relationship includes:

[0113] fd = f0 + |fg

[0114] And

[0115] fp = |fg| - f0

[0116] Wherein, f d is the AC-side main oscillation frequency, f g is the DC-side oscillation frequency, f 0 is the fundamental frequency of the power system, f p is the AC-side coupled oscillation frequency.

[0117] Specifically, after obtaining the DC-side oscillation frequency f g , through the first calculation relationship, the AC-side main oscillation frequency f d and the AC-side coupled oscillation frequency f p can be calculated and obtained. Furthermore, based on the AC-side main oscillation frequency f d and the AC-side coupled oscillation frequency f p , the wideband phasor of the power system can be obtained through the second calculation relationship. By observing the DC-side information in the present disclosure, obtaining the DC-side oscillation frequency, and then obtaining the AC-side main oscillation frequency f d and the AC-side coupled oscillation frequency f p through the first calculation relationship, compared with the method of directly observing the AC-side information and then calculating to obtain the AC-side main oscillation frequency f d and the AC-side coupled oscillation frequency f p , the time required is shorter under the condition of ensuring the measurement accuracy remains unchanged. Therefore, the AC-side oscillation component can be obtained quickly and accurately, and the overall time for obtaining the wideband phasor can be shortened. Furthermore, the wideband phasor can be obtained in a shorter time while ensuring the measurement accuracy remains unchanged, improving the acquisition efficiency of the wideband phasor.

[0118] Figure 2 is a schematic flowchart of a preferred method for measuring the wideband phasor of a power system provided by an embodiment of the present disclosure, as shown in Figure 2As shown, the measurement method includes: S210 - S280.

[0119] S210. Obtain the DC - side electrical signal expression.

[0120] Specifically, the DC - side electrical signal expression:

[0121]

[0122] where A 1 is the amplitude of the DC component of the electrical signal; A g is the amplitude of the oscillation component on the DC side; σ is the damping factor; f g is the oscillation frequency on the DC side; is the initial phase of the oscillation component on the DC side.

[0123] S220. Based on the measurement algorithm of the FIR filter, convert the DC - side electrical signal expression into a DC - side phasor expression.

[0124] Specifically, according to the phasor measurement method of the FIR filter, the DC - side electrical signal expression is transformed into:

[0125]

[0126] where n ∈[-N, N], n is the time window, and 2N + 1 is the number of sampling points of the FIR filter; p g is the phasor of the oscillation component on the DC side, p g * is the conjugate component corresponding to the phasor of the oscillation component on the DC side; T s = 1 / f s is the sampling interval of the FIR filter, f s is the sampling frequency of the FIR filter. The expression of the phasor p g of the oscillation component on the DC side is:

[0127]

[0128] And, since the FIR filter includes the Kaiser window function, the expression of the windowed FIR filter is:

[0129]

[0130] where f c is the center frequency of the FIR filter; w(n) is the time - domain expression of the Kaiser window function. The time - domain expression of the Kaiser window function is:

[0131]

[0132] Among them, β is the adjustable parameter of the Kaiser window function. By adjusting the β parameter of the Kaiser window function, the bandwidth of the Kaiser window function can be regulated and the amplitude-frequency characteristic can be improved. E 0 The expression of E(x) is specifically:

[0133]

[0134] Therefore, according to the above expression, the phasor expression on the DC side can be derived as:

[0135]

[0136] The phasor expression on the DC side is used to calculate and obtain the estimation formula of the oscillation frequency on the DC side; the estimation formula of the oscillation frequency on the DC side is used to obtain the oscillation frequency on the DC side.

[0137] S230. Obtain the oscillation frequency on the DC side based on the phasor expression on the DC side.

[0138] Specifically, according to the phasor expression on the DC side, the estimation formula of the oscillation frequency on the DC side can be obtained as:

[0139]

[0140] According to the estimation formula of the oscillation frequency on the DC side, the oscillation frequency |fg| on the DC side can be obtained.

[0141] S240. Based on the oscillation frequency on the DC side, calculate and obtain the main oscillation frequency on the AC side and the coupled oscillation frequency on the AC side by using the first calculation relationship.

[0142] Specifically, the first calculation relationship includes:

[0143] fd = f0 + |fg|

[0144] And

[0145] fp = |fg| - f0

[0146] Among them, f d is the main oscillation frequency on the AC side, f g is the oscillation frequency on the DC side, f 0 is the fundamental frequency of the power system, f p is the coupled oscillation frequency on the AC side. After obtaining the oscillation frequency f g on the DC side, through the first calculation relationship, the main oscillation frequency f d on the AC side and the coupled oscillation frequency f p on the AC side can be calculated and obtained.

[0147] S250. Obtain the expression of the electrical signal on the AC side.

[0148] Specifically, the expression of the electrical signal on the AC side is:

[0149]

[0150] Among them, A q represents the initial amplitude of the q - component of the AC - side signal; represents the initial phase of the q - component of the AC - side signal, and σ is the damping factor. The q - component can be any one of the 0 - component, d - component, and p - component. The 0 - component is the fundamental - frequency component, the d - component is the main oscillation component, and the p - component is the coupling - frequency component.

[0151] Perform transformation processing on the AC - side electrical signal expression. Set the fundamental - frequency phasor expression as:

[0152]

[0153] The AC - side main - oscillation frequency phasor expression is:

[0154]

[0155] The coupling - oscillation frequency phasor expression is:

[0156]

[0157] Therefore, the transformed AC - side electrical signal expression can be further expressed as:

[0158]

[0159] S260. Based on the AC - side electrical signal expression, obtain the AC - side dynamic phasor using the frequency - domain sampling theorem; according to the AC - side dynamic phasor, obtain the main oscillation component of the AC - side signal.

[0160] Specifically, due to the effect of the damping factor σ, the amplitudes of the oscillation component and its coupling component of the AC - side signal are dynamically changing. Based on the frequency - domain sampling theorem, the sum of multiple complex - exponential functions within a finite observation time window can be used to approximately represent the AC - side dynamic phasor. Therefore, based on the AC - side electrical signal expression, the AC - side dynamic phasor can be obtained:

[0161]

[0162] where k ∈ Z, t ∈ [-T, T], 2T is the observation window length, 2K is the order; Δf is the frequency - domain sampling interval; G q,k is the sample of the q - component in the frequency domain.

[0163] According to the AC - side dynamic phasor, the main oscillation component of the AC - side signal at t = 0 can be obtained. The main oscillation component expression is:

[0164]

[0165] The first derivative of the main oscillation component expression is:

[0166]

[0167] S270. According to the AC-side electrical signal expression and the AC-side dynamic phasor, a vector estimation formula is constructed using the weighted least squares method, and, according to the main oscillation component expression and the first derivative of the main oscillation component expression, a corrected frequency estimation formula is constructed.

[0168] S280. Based on the vector estimation formula and the main oscillation component expression, the oscillation amplitude is obtained, and, based on the corrected frequency estimation formula, the corrected frequency is obtained.

[0169] Specifically, according to the transformed AC-side electrical signal expression and the AC-side dynamic phasor, a matrix expression can be obtained:

[0170]

[0171] where S is a column vector containing 2N + 1 samples of S 2 (t); E is a matrix containing the sample information of and its conjugate, and G q,k can be any one of G 0,k , G d,k and G p,k , and the vector G is a column vector containing the phasor sample G q,k .

[0172] The vector G is estimated using the weighted least squares method to construct a vector estimation formula:

[0173]

[0174] where H represents the Hermitian operator; W is a weight matrix containing the AC-side window function information. The modulus operation is performed on the AC-side dynamic phasor, and it can be known that the value corresponding to the oscillation amplitude at t = 0 is the result of the main oscillation component expression Therefore, it can be calculated through the vector estimation formula Thus, the calculation of the oscillation amplitude is realized.

[0175] Based on the frequency measurement estimation formula defined by the relevant standard IEEE / IEC 60255-118-1 in the power system industry, the corrected frequency can be estimated by comprehensively considering the main oscillation component expression and the first derivative of the main oscillation component expression. Therefore, according to the main oscillation component expression and the first derivative of the main oscillation component expression, a corrected frequency estimation formula is constructed, and the corrected frequency estimation formula is:

[0176]

[0177] The correction frequency can be estimated according to the correction frequency estimation formula.

[0178] Figure 3 The figure is a schematic structural diagram of a measurement system for broadband phasors of a power system provided by an embodiment of the present disclosure. As Figure 3 shown, the measurement system includes: a DC-side oscillation component acquisition module 310, an AC-side oscillation component acquisition module 320, and a broadband phasor acquisition module 330.

[0179] The DC-side oscillation component acquisition module 310 is configured to acquire the DC-side oscillation component of the power system.

[0180] The AC-side oscillation component acquisition module 320 is configured to calculate and acquire the AC-side oscillation component of the power system based on the DC-side oscillation component by using a first calculation relationship; the first calculation relationship is the calculation relationship between the DC-side oscillation component and the AC-side oscillation component.

[0181] The broadband phasor acquisition module 330 is configured to calculate and acquire the broadband phasor of the power system based on the AC-side oscillation component by using a second calculation relationship; the second calculation relationship is the calculation relationship between the AC-side oscillation component and the broadband phasor.

[0182] Wherein, the DC-side oscillation component is less than the AC-side oscillation component.

[0183] It can be understood that the measurement system for broadband phasors of a power system provided by an embodiment of the present application can achieve the corresponding beneficial effects of the measurement method for broadband phasors of a power system provided by the above-mentioned embodiment, which will not be elaborated here.

[0184] The present disclosure also provides a computer storage medium, on which a computer program is stored. When the computer program is executed, the steps of the measurement method for broadband phasors of a power system corresponding to any of the above embodiments are implemented.

[0185] It can be understood that the computer storage medium provided by an embodiment of the present application can achieve the corresponding beneficial effects of the measurement method for broadband phasors of a power system provided by the above-mentioned embodiment, which will not be elaborated here.

[0186] It should be noted that, in this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0187] The above are only specific embodiments of the present disclosure, enabling those skilled in the art to understand or implement the present disclosure. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to these embodiments herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for measuring broadband phasors in a power system, characterized in that: include: Obtaining a DC side oscillation component of the power system; Based on the DC side oscillation component, a first calculation relationship is used to calculate and obtain an AC side oscillation component of the power system; The first calculation relationship is a calculation relationship between the DC side oscillation component and the AC side oscillation component; Based on the AC side oscillation component, a second calculation relationship is used to calculate and obtain the broadband phasor of the power system; the second calculation relationship is a calculation relationship between the AC side oscillation component and the broadband phasor; The DC side oscillation component is smaller than the AC side oscillation component.

2. The measuring method according to claim 1, characterized in that: The DC side oscillation component includes a DC side oscillation frequency; The obtaining of the DC side oscillation component of the power system comprises: Based on the measurement algorithm of the digital processing unit, the DC side electrical signal expression is converted into the DC side phasor expression; The DC side oscillation frequency is obtained based on the DC side phasor expression.

3. The measuring method according to claim 2, characterized in that: The digital processing unit includes a window function; the window function is used to convert the DC side electrical signal expression into the DC side phasor expression.

4. The measuring method according to claim 3, characterized in that: The window function includes a Kaiser window function.

5. The measuring method according to claim 3, characterized in that: The DC side electrical signal expression is: Among them, A1 is the amplitude of the DC component of the electrical signal; A g is the amplitude of the oscillation component on the DC side; σ is the damping factor; f g is the DC side oscillation frequency; is the initial phase of the DC side oscillation component; The DC side phasor expression is: Among them, n∈[-N,N], 2N+1 is the number of sampling points; h(n) is the expression of the digital processing unit; w(n) is the time domain expression of the window function; the DC side phasor expression is used to calculate and obtain the DC side oscillation frequency estimation formula; the DC side oscillation frequency estimation formula is used to obtain the DC side oscillation frequency.

6. The measuring method according to claim 5, characterized in that: The DC side oscillation frequency estimation formula is: Among them, T s =1 / f s is the sampling interval, f s is the sampling frequency.

7. The measuring method according to claim 1, characterized in that: The broadband phasor includes a correction frequency; Before calculating and obtaining the wide-band phasor of the power system by using a second calculation relationship based on the AC side oscillation frequency component, the method further includes: Obtain the dynamic phasor of the AC side based on the AC side electrical signal expression; According to the AC side dynamic phasor, a main oscillation component of the AC side signal is obtained; Constructing a modified frequency estimation formula according to the main oscillation component expression and the first-order derivative of the main oscillation component expression; wherein the second calculation relationship includes the modified frequency estimation formula; The corrected frequency is acquired based on the corrected frequency estimation formula.

8. The measuring method according to claim 7, characterized in that: The broadband phasor also includes an oscillation amplitude; Before calculating and acquiring the wide-band phasor of the power system by using a second calculation relationship based on the AC side oscillation component, the method further includes: Constructing a vector estimation formula according to the AC side electrical signal expression and the AC side dynamic phasor; wherein the second calculation relationship also includes the vector estimation formula; Based on the vector estimation formula and the main oscillation component expression, the oscillation amplitude is obtained.

9. The measuring method according to claim 8, characterized in that: The constructing of a vector estimation formula according to the AC side electrical signal expression and the AC side dynamic phasor comprises: The vector estimation formula is constructed by using the weighted least square method according to the AC side electrical signal expression and the AC side dynamic phasor.

10. The measuring method according to claim 1, characterized in that: The DC side oscillation component includes a DC side oscillation frequency; the AC side oscillation component includes an AC side main oscillation frequency and an AC side coupling oscillation frequency; The first calculation relationship includes: fd=f0+|fg as well as fp=|fg|-f0 Among them, f d is the main oscillation frequency of the AC side, f g is the DC side oscillation frequency, f0 is the base frequency of the power system, and f p is the AC side coupling oscillation frequency.

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