New energy unit impedance correction method and system based on parameter fitting

Abstract

The invention discloses a new energy unit impedance correction method and system based on parameter fitting, and belongs to the technical field of impedance measurement error correction of new energy units. The method comprises the following steps: measuring the impedance of a new energy unit, and obtaining an impedance amplitude data array and an impedance phase data array under each frequency; calculating the impedance amplitude data array and the impedance phase data array to obtain an impedance real part data array and an impedance imaginary part data array; fitting the impedance real part data array equation coefficient and the impedance imaginary part data array equation coefficient to obtain a fitted impedance real part and an impedance imaginary part under each frequency; and calculating the corrected impedance amplitude and impedance phase under each frequency based on the fitted impedance real part and impedance imaginary part. According to the invention, random errors caused by sampling random errors, harmonic interference and other factors to impedance measurement results can be effectively suppressed.

Description

Technical Field

[0001] The present invention relates to the technical field of impedance measurement error correction for new energy units, and more specifically, to a new energy unit impedance correction method and system based on parameter fitting. Background Art

[0002] The large-scale penetration of new energy power generation systems such as wind power generation and photovoltaic power generation into the power system has brought great challenges to the stable operation of the power system and is prone to cause harmonic oscillations in the system. The control strategies of new energy generating units are relatively complex. Each new energy unit manufacturer samples its own control method, and there are multiple control parameters in the control method, which will all affect the stable operation ability of new energy units under different grid conditions. How to evaluate the stability of new energy units is an urgent problem to be solved.

[0003] The impedance stability theory can analyze and evaluate the stable operation ability of new energy units according to the impedance characteristics shown by new energy units to the outside world. Even if the control strategies and parameters inside the new energy units are unknown, the impedance of new energy can be measured by injecting external disturbances. However, the impedance measurement results of new energy units will be interfered by random factors such as sampling errors and harmonics, resulting in uncertain errors in the impedance amplitude and phase obtained by direct measurement. Reasonably correcting the impedance measurement error of new energy units caused by the above factors has important value for the impedance measurement and stable operation ability analysis of new energy units. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a new energy unit impedance correction method based on parameter fitting, including:

[0005] Measure the impedance of the new energy unit to obtain an impedance amplitude data array and an impedance phase data array at each frequency;

[0006] Calculate the impedance real part data array and the impedance imaginary part data array from the impedance amplitude data array and the impedance phase data array;

[0007] Fit the equation coefficients of the impedance real part data array and the equation coefficients of the impedance imaginary part data array to obtain the fitted impedance real part and impedance imaginary part at each frequency;

[0008] Based on the fitted impedance real part and impedance imaginary part, calculate the corrected impedance amplitude and impedance phase at each frequency.

[0009] Optionally, the calculation of the impedance amplitude data array and the impedance phase data array includes: sine calculation and cosine calculation.

[0010] Optionally, the method further includes:

[0011] Normalize the impedance angular frequency, and normalize the real part data array of impedance and the imaginary part data array of impedance.

[0012] Optionally, fit the equation coefficients of the real part data array of impedance and the equation coefficients of the imaginary part data array of impedance, including:

[0013] Establish an impedance transfer function, substitute the normalized impedance angular frequency, the real part data array of impedance, and the imaginary part data array of impedance into the transfer function, and respectively extract the equation of the real part data array of impedance and the equation of the imaginary part data array of impedance. Use the elements in the real part data array of impedance and the imaginary part data array of impedance as the dependent variables to fit the coefficients of the equation of the real part data array of impedance and the equation of the imaginary part data array of impedance.

[0014] On the other hand, the present invention also proposes a new energy unit impedance correction system based on parameter fitting, including:

[0015] A measurement unit for measuring the impedance of the new energy unit to obtain the impedance amplitude data array and the impedance phase data array at each frequency;

[0016] A calculation unit for calculating the impedance amplitude data array and the impedance phase data array to obtain the real part data array of impedance and the imaginary part data array of impedance;

[0017] A fitting unit for fitting the equation coefficients of the real part data array of impedance and the equation coefficients of the imaginary part data array of impedance to obtain the fitted real part of impedance and the imaginary part of impedance at each frequency;

[0018] A correction unit for calculating the corrected impedance amplitude and impedance phase at each frequency based on the fitted real part of impedance and the imaginary part of impedance.

[0019] Optionally, the calculation of the impedance amplitude data array and the impedance phase data array includes: sine calculation and cosine calculation.

[0020] Optionally, the fitting unit is further configured to:

[0021] Normalize the impedance angular frequency, and normalize the real part data array of impedance and the imaginary part data array of impedance.

[0022] Optionally, the fitting of the equation coefficients of the real part data array of impedance and the equation coefficients of the imaginary part data array of impedance includes:

[0023] Establish an impedance transfer function. Substitute the standardized impedance angular frequency, real part data array of impedance, and imaginary part data array of impedance into the transfer function, and respectively extract the real part data array equation of impedance and the imaginary part data array equation of impedance. Use the elements in the real part data array of impedance and the imaginary part data array of impedance as the dependent variables to fit the coefficients of the real part data array equation of impedance and the imaginary part data array equation of impedance.

[0024] On the other hand, the present invention also provides a computing device, including: one or more processors;

[0025] The processor is used to execute one or more programs;

[0026] When the one or more programs are executed by the one or more processors, the method as described above is implemented.

[0027] On the other hand, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed, the method as described above is implemented.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] The present invention provides a new energy unit impedance correction method based on parameter fitting, including: measuring the impedance of the new energy unit to obtain the impedance amplitude data array and impedance phase data array at each frequency; calculating the real part data array of impedance and the imaginary part data array of impedance from the impedance amplitude data array and impedance phase data array; fitting the coefficients of the real part data array equation of impedance and the coefficients of the imaginary part data array equation of impedance to obtain the fitted real part and imaginary part of impedance at each frequency; calculating the corrected impedance amplitude and impedance phase at each frequency based on the fitted real part and imaginary part of impedance. The present invention can effectively suppress the random errors brought by factors such as sampling random errors and harmonic interference to the impedance measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flowchart of the method of the present invention;

[0031] Figure 2 is a flowchart of an embodiment of the method of the present invention;

[0032] Figure 3 is the d-axis impedance correction result of the inverter of the photovoltaic power generation system in the embodiment of the method of the present invention;

[0033] Figure 4 is the q-axis impedance correction result of the inverter of the photovoltaic power generation system in the embodiment of the method of the present invention;

[0034] Figure 5The positive sequence impedance correction result of the inverter in the direct-drive wind turbine power generation system in the method embodiment of the present invention;

[0035] Figure 6 The structure diagram of the system of the present invention. Detailed implementation manners

[0036] Now, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely, and to fully convey the scope of the present invention to those skilled in the art. The terms in the exemplary embodiments shown in the drawings are not limitations on the present invention. In the drawings, the same units / elements are denoted by the same reference numerals.

[0037] Unless otherwise specified, the terms (including scientific and technical terms) used herein have the ordinary meaning understood by those skilled in the art. In addition, it can be understood that the terms defined in the commonly used dictionary should be understood as having a meaning consistent with the context of their related fields, and should not be understood as idealized or overly formal meanings.

[0038] Embodiment 1:

[0039] The present invention proposes a new energy unit impedance correction method based on parameter fitting, as Figure 1 shown, including:

[0040] Step 1: Measure the impedance of the new energy unit to obtain the impedance amplitude data array and the impedance phase data array at each frequency;

[0041] Step 2: Calculate the impedance real part data array and the impedance imaginary part data array from the impedance amplitude data array and the impedance phase data array;

[0042] Step 3: Fit the equation coefficients of the impedance real part data array and the equation coefficients of the impedance imaginary part data array to obtain the fitted impedance real part and impedance imaginary part at each frequency;

[0043] Step 4: Calculate the corrected impedance amplitude and impedance phase at each frequency based on the fitted impedance real part and impedance imaginary part.

[0044] Among them, the calculation of the impedance amplitude data array and the impedance phase data array includes: sine calculation and cosine calculation.

[0045] Among them, the method further includes:

[0046] Normalize the impedance angular frequency, and normalize the impedance real part data array and the impedance imaginary part data array.

[0047] Among them, fitting the coefficients of the impedance real part data array equation and the impedance imaginary part data array equation includes:

[0048] Establish an impedance transfer function, substitute the normalized impedance angular frequency, impedance real part data array, and impedance imaginary part data array into the transfer function, and respectively extract the impedance real part data array equation and the impedance imaginary part data array equation. Using the elements in the impedance real part data array and the impedance imaginary part data array as the dependent variables, fit the coefficients of the impedance real part data array equation and the impedance imaginary part data array equation.

[0049] The following further illustrates the present invention with specific cases:

[0050] Among them, the theoretical basis of the present invention is as follows:

[0051] The impedance of a new energy unit can be solved in a rotating coordinate system, and its impedance measurement results are generally:

[0052]

[0053] In the above formula, Z dd (s) represents the d-axis impedance, Z qq (s) represents the q-axis impedance, Z dq (s) and Z qd (s) represent the cross-impedance form of the d-axis and q-axis.

[0054] The impedance of a new energy unit can also be solved in the positive / negative sequence coordinate system, and its impedance measurement results are generally:

[0055]

[0056] In the above formula, Z pp (s) represents the positive sequence impedance, Z nn (s) represents the negative sequence impedance, Z pn (s) and Z np (s) represent the cross-impedance of the positive sequence and negative sequence.

[0057] In the first step, the array Z mag (ω k ) composed of the impedance amplitude data of the new energy unit at each measured frequency and the array A pha (ω k ) composed of the phase data are subjected to a secondary calculation to obtain the array Z imp_real (ω k ) composed of the real part data of the impedance and the array Z imp_imag (ω k ) composed of the imaginary part data of the impedance. The frequency information of the measured impedance is represented by ω kdenotes the angular frequency array of the measured impedance data, which consists of a series of angular frequencies ω k0 ~ω ka and a represents the number of frequencies contained in the frequency array. Here, the frequency f k can also be used to represent the frequency information at which the measured impedance is located, and there is a corresponding relationship between the angular frequency and the frequency ω k = 2πf k . The quadratic calculation method is as follows:

[0058] Z imp_real (ω k ) = Z mag cos[A pha (ω k )]

[0059] Z imp_imag (ω k ) = Z mag sin[A pha (ω k )]

[0060] In the above formula, cos and sin are cosine calculation and sine calculation respectively.

[0061] In the second step, when fitting the equation composed of polynomials with the array Z imp_real (ω k ) composed of the real part data of the impedance obtained by the quadratic calculation and the array Z imp_imag (ω k ) composed of the imaginary part data, the data is standardized.

[0062] The data standardization method standardizes each angular frequency, and the specific standardization method is as follows:

[0063]

[0064] In the above formula, ω sd represents the angular frequency array after standardization processing, Mean represents the average value of the corresponding array, and std represents the standard deviation of the corresponding array.

[0065] The data standardization method for the array Z imp_real (ω k ) and the array Z imp_imag (ω k ) is as follows:

[0066]

[0067] In the above formula, Z sd_real (ω k ) is the array composed of the real part data after standardization processing, Zsd_imag (ω k ) is an array composed of the imaginary part data after standardization processing, Max represents the maximum value of the response array, and Min represents the minimum value of the corresponding array.

[0068] In the third step, considering that impedance is a transfer function, the impedance Z dd (s), Z qq (s), Z dq (s) and Z qd (s), as well as the impedance Z pp (s), Z nn (s), Z pn (s) and Z np (s) can all be uniformly expressed in the complex frequency domain as:

[0069]

[0070] In the above formula, Z imp (s) is the transfer function of the impedance of the new energy unit, b 0 ~b n , c 0 ~c n-1 are correlation coefficients, s is the Laplace operator, and s = jω, j is the imaginary operator, and ω is the angular frequency variable.

[0071] Substitute s = jω into Z imp (s), and extract the real part and the imaginary part of the equation respectively, then the equation used to fit the angular frequency array, the real part data and the imaginary part data array is composed of a high-order polynomial, and the equation is as follows:

[0072]

[0073] In the above formula, Z ce_real (ω) and Z ce_imag (ω) are the real part and the imaginary part of the impedance at the mth angular frequency position obtained through polynomial calculation, ω km is the mth element in the standardized array ω sd , p r0 ~p rn , q r0 ~q rn , p i0 ~p in , q i0 ~q in-1 are the coefficients of the polynomial of the equation respectively, and n is the order of the polynomial.

[0074] Taking the elements in the angular frequency array ω sd as independent variables, and taking the arrays Z sd_real (ωk ) and the array Z sd_imag (ω k ) where the elements are dependent variables, for the coefficients p r0 ~p rn 、q r0 ~q rn 、p i0 ~p in 、q i0 ~q in-1 in the polynomial equation for fitting, and obtain the fitting results of these coefficients.

[0075] Fourth step, use the obtained equation composed of high-order polynomials and the fitted coefficients p r0 ~p rn 、q r0 ~q rn 、p i0 ~p in 、q i0 ~q in-1 to calculate the corresponding real part of impedance Z ce_real (ω) and the imaginary part Z ce_imag (ω) at each frequency one by one, and restore and calculate the real part and the imaginary part at each frequency.

[0076] According to the real part and the imaginary part of impedance obtained in the previous step, calculate the magnitude and phase of impedance at each frequency one by one. The calculation methods of the impedance magnitude and phase are as follows:

[0077]

[0078]

[0079] In the above formula, Zmagc(ωkm) and Amagc(ωkm) are the impedance magnitude and phase information at each frequency after error correction.

[0080] The results of impedance correction for the d-axis impedance and q-axis impedance of the photovoltaic inverter in the rotating coordinate system by using the method of the present invention are as shown in Figure 3 and Figure 4 , and the results of impedance correction for the positive-sequence impedance of the direct-drive wind turbine inverter by using the method of the present invention are as shown in Figure 5 .

[0081] The impedance of the new energy unit measured by the present invention, according to the method provided by the present invention, can effectively suppress the random errors brought by factors such as sampling random errors and harmonic interference to the impedance measurement results, and can obtain a specific equation characterizing the real part and the imaginary part of the impedance of the new energy unit under specific working conditions, providing a convenient interpolation method for the impedance measurement method at actual discontinuous frequencies, and can directly calculate the impedance of the new energy unit at unmeasured frequencies, thereby contributing to the formation of a database of new energy units.

[0082] Example 2:

[0083] The present invention also proposes a new energy unit impedance correction system 200 based on parameter fitting, as Figure 6 shown, including:

[0084] A measurement unit 201, configured to measure the impedance of the new energy unit to obtain an impedance amplitude data array and an impedance phase data array at each frequency;

[0085] A calculation unit 202, configured to calculate the impedance real part data array and the impedance imaginary part data array from the impedance amplitude data array and the impedance phase data array;

[0086] A fitting unit 203, configured to fit the equation coefficients of the impedance real part data array and the equation coefficients of the impedance imaginary part data array to obtain the fitted impedance real part and impedance imaginary part at each frequency;

[0087] A correction unit 204, configured to calculate the corrected impedance amplitude and impedance phase at each frequency based on the fitted impedance real part and impedance imaginary part.

[0088] Among them, the calculation of the impedance amplitude data array and the impedance phase data array includes: sine calculation and cosine calculation.

[0089] Among them, the fitting unit 203 is further configured to:

[0090] Standardize the impedance angular frequency and standardize the impedance real part data array and the impedance imaginary part data array.

[0091] Among them, the fitting of the equation coefficients of the impedance real part data array and the equation coefficients of the impedance imaginary part data array includes:

[0092] Establish an impedance transfer function, substitute the standardized impedance angular frequency, impedance real part data array and impedance imaginary part data array into the transfer function, and respectively extract the impedance real part data array equation and the impedance imaginary part data array equation, and use the elements in the impedance real part data array and the impedance imaginary part data array as the dependent variables to fit the coefficients of the impedance real part data array equation and the impedance imaginary part data array equation.

[0093] The present invention can effectively suppress the random errors brought by factors such as sampling random errors and harmonic interference to the impedance measurement results.

[0094] Example 3:

[0095] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory. The memory is used to store a computer program, and the computer program includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the method in the above embodiments.

[0096] Embodiment 4:

[0097] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and the operating system of the terminal is stored in this storage space. And, one or more instructions suitable for being loaded and executed by the processor are also stored in this storage space. These instructions may be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here may be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The one or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the steps of the method in the above embodiments.

[0098] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code. The solutions in the embodiments of the present invention can be implemented in various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript, etc.

[0099] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0100] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0101] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0102] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0103] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A new energy unit impedance correction method based on parameter fitting, characterized in that: The method comprises: Measure the impedance of the new energy unit and obtain the impedance amplitude data array and impedance phase data array at each frequency; Calculating the impedance amplitude data array and the impedance phase data array to obtain an impedance real part data array and an impedance imaginary part data array; Fitting the coefficients of the impedance real part data array equation and the impedance imaginary part data array equation to obtain the fitted impedance real part and impedance imaginary part at each frequency; Based on the fitted real impedance part and imaginary impedance part, the corrected impedance amplitude and impedance phase at each frequency are calculated.

2. The impedance correction method for new energy units according to claim 1 is characterized in that: The calculations performed on the impedance magnitude data array and the impedance phase data array include: sine calculations and cosine calculations.

3. The impedance correction method for new energy units according to claim 1 is characterized in that: The method further comprises: The impedance angular frequency is normalized, and the impedance real part data array and the impedance imaginary part data array are normalized.

4. The impedance correction method for new energy units according to claim 1 is characterized in that: The step of fitting the coefficients of the impedance real part data array equation and the coefficients of the impedance imaginary part data array equation includes: An impedance transfer function is established, and the standardized impedance angular frequency, impedance real data array and impedance imaginary data array are substituted into the transfer function, and the impedance real data array equation and the impedance imaginary data array equation are extracted respectively. The elements in the impedance real data array and the impedance imaginary data array are used as dependent variables, and the coefficients of the impedance real data array equation and the impedance imaginary data array equation are fitted.

5. A new energy unit impedance correction system based on parameter fitting, characterized in that: The system comprises: The measuring unit is used to measure the impedance of the new energy unit and obtain the impedance amplitude data array and the impedance phase data array at each frequency; A calculation unit, used for calculating the impedance amplitude data array and the impedance phase data array to obtain an impedance real part data array and an impedance imaginary part data array; A fitting unit, used for fitting the coefficients of the impedance real part data array equation and the impedance imaginary part data array equation to obtain the fitted impedance real part and impedance imaginary part at each frequency; The correction unit is used to calculate the corrected impedance amplitude and impedance phase at each frequency based on the fitted impedance real part and impedance imaginary part.

6. The impedance correction system for new energy units according to claim 5 is characterized in that: The calculations performed on the impedance magnitude data array and the impedance phase data array include: sine calculations and cosine calculations.

7. The impedance correction system for new energy units according to claim 5 is characterized in that: The fitting unit is further used for: The impedance angular frequency is normalized, and the impedance real part data array and the impedance imaginary part data array are normalized.

8. The impedance correction system for new energy units according to claim 5 is characterized in that: The step of fitting the coefficients of the impedance real part data array equation and the coefficients of the impedance imaginary part data array equation includes: An impedance transfer function is established, and the standardized impedance angular frequency, impedance real data array and impedance imaginary data array are substituted into the transfer function, and the impedance real data array equation and the impedance imaginary data array equation are extracted respectively. The elements in the impedance real data array and the impedance imaginary data array are used as dependent variables, and the coefficients of the impedance real data array equation and the impedance imaginary data array equation are fitted.

9. A computer device, characterized in that: include: one or more processors; a processor for executing one or more programs; When the one or more programs are executed by the one or more processors, the method according to any one of claims 1 to 4 is implemented.

10. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the method according to any one of claims 1 to 4 is implemented.

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