Grid-connected system eigenvalue calculation method, device and equipment and readable storage medium

Abstract

The application discloses a grid-connected system eigenvalue calculation method, device and equipment and a readable storage medium. The method first determines a frequency range corresponding to a grid-connected system eigenvalue. Then, an aggregated impedance amplitude frequency response curve of the grid-connected system can be drawn, and a minimum point of the aggregated impedance amplitude frequency response curve of the grid-connected system in the frequency range is determined. In this way, the aggregated impedance amplitude frequency response curve of the grid-connected system is easy-to-obtain frequency domain information, and the damping ratio corresponding to the grid-connected system eigenvalue can be estimated through the minimum point in the aggregated impedance amplitude frequency response curve. That is, the grid-connected system eigenvalue in the time domain can be calculated through the damping ratio. It can be seen that the grid-connected system eigenvalue in the time domain can be calculated through the easy-to-obtain frequency domain information according to the application, and the grid-connected system eigenvalue is provided as research basis for analyzing and understanding oscillation in the grid-connected system, so that the oscillation of the grid-connected system is reduced.

Description

Technical Field

[0001] This application relates to the field of power grid technology, and more specifically, to a method, apparatus, device, and readable storage medium for calculating the characteristic roots of a grid-connected system. Background Technology

[0002] After new energy generating units and synchronous generator units are connected to the power grid, they form a grid-connected system. During the operation of the grid-connected system, the dynamic interaction between various power devices and the grid may cause oscillations, which affect the stable operation of the grid-connected system. Therefore, reducing oscillations in the grid-connected system has become a focus of attention. From a mathematical perspective, the nature and characteristics of the above oscillation problem are completely determined by the characteristic roots of the grid-connected system. That is, a detailed understanding and analysis of oscillations in the grid-connected system can start from the characteristic roots of the grid-connected system. However, the characteristic roots of the grid-connected system cannot be determined through simulation analysis or theoretical derivation, which poses a significant challenge to reducing oscillations in the grid-connected system.

[0003] Therefore, in order to solve the above problems, a method for calculating the characteristic roots of a grid-connected system can be introduced to calculate the characteristic roots of the grid-connected system, thereby understanding the oscillations in the grid-connected system through characteristic root analysis and reducing the oscillations in the grid-connected system. Summary of the Invention

[0004] In view of this, this application provides a method, apparatus, device and readable storage medium for calculating the characteristic roots of a grid-connected system, for providing a method for calculating the characteristic roots of a grid-connected system.

[0005] To achieve the above objectives, the following solution is proposed:

[0006] A method for calculating the characteristic roots of a grid-connected system, comprising:

[0007] Estimate the frequency range corresponding to the characteristic roots of the grid-connected system;

[0008] Plot the aggregate impedance amplitude-frequency response curve of the grid-connected system, and determine the minimum point of the aggregate impedance amplitude-frequency response curve of the grid-connected system within the specified frequency range.

[0009] Based on the minimum point, determine the damping ratio of the characteristic root of the grid-connected system;

[0010] The characteristic roots of the grid-connected system are calculated based on the damping ratio.

[0011] Optionally, the grid connection system refers to the connection of power equipment into the power grid system;

[0012] The plotting of the aggregate impedance amplitude-frequency response curve of the grid-connected system includes:

[0013] Determine the power equipment impedance matrix of the grid-connected system in the frequency range, and the grid impedance matrix of the grid-connected system in the frequency range;

[0014] Based on the impedance matrix of the power equipment and the impedance matrix of the power grid, plot the aggregate impedance amplitude frequency response curve of the grid-connected system.

[0015] Optionally, determining the power equipment impedance matrix of the grid-connected system in the frequency range and the grid impedance matrix of the grid-connected system in the frequency range includes:

[0016] Based on the circuit parameters and control parameters of the power equipment in the grid-connected system, the frequency response relationship between the terminal voltage and terminal current of the power equipment is determined within the frequency range, and the frequency response relationship between the terminal voltage and terminal circuit of the power equipment is the impedance matrix of the power equipment.

[0017] Based on the circuit parameters and control parameters of the power grid in the grid-connected system, the frequency response relationship between the terminal voltage and terminal current of the power grid within the specified frequency range is determined, and the frequency response relationship between the terminal voltage and terminal circuit of the power grid is the power grid impedance matrix.

[0018] Optionally, the step of plotting the aggregate impedance amplitude frequency response curve of the grid-connected system based on the impedance matrix of the power equipment and the impedance matrix of the power grid includes:

[0019] Determine the frequency interval based on the frequency range;

[0020] Within the frequency range, frequency points are set at intervals of the frequency interval to obtain multiple frequency points;

[0021] Based on the power equipment impedance matrix and the power grid impedance matrix, determine the aggregate impedance amplitude corresponding to each frequency point;

[0022] Based on each frequency point and its corresponding aggregate impedance amplitude, plot the aggregate impedance amplitude frequency response curve of the grid-connected system.

[0023] Optionally, the frequency range includes multiple frequency points;

[0024] The step of determining the damping ratio of the characteristic root of the grid-connected system based on the minimum point includes:

[0025] Based on the range of values ​​for the characteristic root damping ratio of the grid-connected system, an arithmetic progression array of damping ratios is constructed, which contains multiple damping ratio values.

[0026] Based on the minimum point, calculate the target aggregate impedance value corresponding to each damping ratio value in the arithmetic progression array of damping ratios at each frequency point;

[0027] Calculate the difference between the target aggregate impedance value and the aggregate impedance amplitude at each frequency point for each damping ratio value, and obtain multiple differences corresponding to each damping ratio value. The aggregate impedance amplitude at that frequency point is the aggregate impedance amplitude corresponding to that frequency point in the aggregate impedance amplitude frequency response curve of the grid-connected system.

[0028] Calculate the root mean square error corresponding to each damping ratio value based on the multiple differences corresponding to each damping ratio value;

[0029] The damping ratio with the smallest mean square error is selected as the damping ratio of the characteristic root of the grid-connected system.

[0030] Optionally, based on the minimum point, the target aggregate impedance value corresponding to each damping ratio value in the arithmetic progression array of damping ratios at each frequency point is calculated, including:

[0031] Using the damping ratio arithmetic progression array, the real and imaginary parts of the aggregate impedance amplitude at the minimum point, the target aggregate impedance value corresponding to the damping ratio value at each frequency point is calculated.

[0032] Optionally, using each damping ratio value in the arithmetic progression array of damping ratios, and the real and imaginary parts of the aggregate impedance amplitude at the minimum point, the target aggregate impedance value corresponding to the damping ratio value at each frequency point is calculated, including:

[0033] Substitute each damping ratio value in the arithmetic progression array of damping ratios, the real part and the imaginary part of the aggregate impedance amplitude at the minimum point into the preset estimation formula to calculate the target aggregate impedance value corresponding to the damping ratio value at each frequency point.

[0034] The estimation formula is as follows:

[0035]

[0036]

[0037]

[0038] Among them, Rtot(f d Xtot(f) is the real part of the aggregation impedance magnitude at the minimum point. d f is the imaginary part of the magnitude of the polymer impedance at the minimum point. d Let f be the frequency corresponding to the minimum point, f be any value within the frequency range, ξ(N) be any damping ratio value in the arithmetic progression array of damping ratios, and Zni(f) be the target aggregate impedance value.

[0039] A grid-connected system characteristic root calculation device, comprising:

[0040] An estimation unit is used to estimate the frequency range corresponding to the characteristic roots of the grid-connected system;

[0041] The plotting unit is used to plot the aggregate impedance amplitude frequency response curve of the grid-connected system and determine the minimum point of the aggregate impedance amplitude frequency response curve of the grid-connected system within the frequency range.

[0042] A determining unit is used to determine the damping ratio of the characteristic roots of the grid-connected system based on the minimum point;

[0043] The calculation unit is used to calculate the characteristic roots of the grid-connected system based on the damping ratio.

[0044] A grid-connected system characteristic root calculation device, comprising a memory and a processor;

[0045] The memory is used to store programs;

[0046] The processor is used to execute the program to implement each step of the above-described method for calculating the characteristic roots of a grid-connected system.

[0047] A readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the grid-connected system characteristic root calculation method as described above.

[0048] As can be seen from the above technical solution, the method for calculating the eigenvalues ​​of a grid-connected system provided in this application can first determine the frequency range corresponding to the eigenvalues ​​of the grid-connected system. Since the eigenvalues ​​of the grid-connected system are a time-domain concept, determining the frequency range allows us to determine the time-domain range of the eigenvalues. Subsequently, we can plot the frequency response curve of the aggregated impedance amplitude of the grid-connected system and determine the minimum point of the curve within the specified frequency range. Thus, the frequency response curve of the aggregated impedance amplitude of the grid-connected system provides readily available frequency-domain information. The damping ratio corresponding to the eigenvalues ​​of the grid-connected system can be estimated using the minimum point in the curve. Once the damping ratio is determined, the eigenvalues ​​of the grid-connected system in the time domain can be calculated using this ratio. Therefore, this application can calculate the eigenvalues ​​of the grid-connected system in the time domain using readily available frequency-domain information, providing a basis for analyzing and understanding oscillations in the grid-connected system, thereby reducing oscillations in the grid-connected system.

[0049] Furthermore, this application starts with easily obtainable frequency domain information, determines the damping ratio through the minimum point, and thus calculates the characteristic roots of the grid-connected system. This reduces the difficulty of obtaining information in the process of calculating the characteristic roots of the grid-connected system, making this application easier to implement and improving its practicality and applicability. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0051] Figure 1 This is a flowchart of a method for calculating the eigenvalues ​​of a grid-connected system disclosed in an embodiment of this application;

[0052] Figure 2 This is a schematic diagram of the structure of a grid-connected system characteristic root calculation device disclosed in an embodiment of this application;

[0053] Figure 3 This is a hardware structure block diagram of a grid-connected system characteristic root calculation device disclosed in an embodiment of this application. Detailed Implementation

[0054] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0055] The method for calculating the characteristic roots of a grid-connected system provided in this application can be executed on various system platforms. The hardware supporting the system platform can be a PC, a terminal, or other processing devices, and the execution subject of the method can be the processor of the system platform.

[0056] Next, combine Figure 1 The method for calculating the characteristic roots of the grid-connected system in this application is described in detail, including the following steps:

[0057] Step S1: Estimate the frequency range corresponding to the characteristic roots of the grid-connected system.

[0058] Specifically, the grid-connected system can be simulated to obtain a grid-connected system simulation model, and the frequency range corresponding to the characteristic roots of the grid-connected system can be estimated based on the grid-connected system simulation model.

[0059] Step S2: Plot the frequency response curve of the aggregate impedance amplitude of the grid-connected system, and determine the minimum point of the frequency response curve of the aggregate impedance amplitude of the grid-connected system within the specified frequency range.

[0060] Specifically, the frequency response curve of the aggregated impedance amplitude of the grid-connected system reflects the relationship between the aggregated impedance and the frequency in the grid-connected system. The horizontal axis of the frequency response curve is the frequency, and the vertical axis is the aggregated impedance amplitude.

[0061] The minimum point can be the minimum point of the polymer impedance amplitude frequency response curve within the frequency range.

[0062] The coordinate points required to plot the aggregate impedance amplitude frequency response curve of a grid-connected system can be determined in various ways. For example, the frequency of the grid-connected system simulation model can be set, and the impedance parameters of the simulation model at that frequency can be collected. The aggregate impedance amplitude at that frequency can be determined using the impedance parameters. By adjusting different frequencies, the aggregate impedance amplitude at each frequency can be obtained, and the aggregate impedance amplitude frequency response curve of the grid-connected system can be plotted based on the aggregate impedance amplitude at each frequency. Alternatively, the aggregate impedance matrix in the grid-connected system can be determined based on the impedance matrix corresponding to the power equipment and the impedance matrix corresponding to the power grid in the grid-connected system, and the aggregate impedance amplitude frequency response curve of the grid-connected system can be plotted based on the aggregate impedance matrix.

[0063] Step S3: Determine the damping ratio of the characteristic root of the grid-connected system based on the minimum point.

[0064] Specifically, the characteristic roots of a grid-connected system are complex numbers. The real part of the characteristic roots of a grid-connected system indicates the stability of the grid-connected system. The larger the absolute value of the real part is, the more stable the grid-connected system is. The imaginary part of the characteristic roots of a grid-connected system indicates the oscillation frequency of the grid-connected system.

[0065] Verification shows that the frequency corresponding to the minimum point is approximately equal to the oscillation frequency of the grid-connected system.

[0066] The relationship between the aggregate impedance amplitude and the damping ratio at the minimum point near the minimum point can be determined based on the frequency response curve of the aggregate impedance amplitude of the grid-connected system.

[0067] Based on the relationship between the amplitude of the aggregate impedance and the damping ratio near the minimum point, the damping ratio of the characteristic root of the grid-connected system can be estimated.

[0068] Step S4: Calculate the characteristic roots of the grid-connected system based on the damping ratio.

[0069] Specifically, after determining the damping ratio of the characteristic roots of the grid-connected system, the characteristic roots of the grid-connected system can be calculated directly using the relationship between the damping ratio and the characteristic roots of the grid-connected system.

[0070] The relationship between the damping ratio and the characteristic root of the grid-connected system is shown in the following formula:

[0071]

[0072] Where ξ(Nmin) is the damping ratio of the characteristic roots of the grid-connected system, f d Let λ be the frequency corresponding to the minimum point, λ be the characteristic root of the grid-connected system, and j represent the imaginary unit.

[0073] As can be seen from the above technical solutions, the embodiments of this application provide a method for calculating the characteristic roots of a grid-connected system. Based on estimating the frequency range corresponding to the characteristic roots of the grid-connected system, this application can plot the frequency response curve of the aggregate impedance amplitude of the grid-connected system using the aggregate impedance amplitude at each frequency point that is relatively easy to obtain, and determine the minimum point on the curve. After determining the minimum point, the damping ratio corresponding to the characteristic roots of the grid-connected system can be determined, and the characteristic roots of the grid-connected system under the concept of time domain can be calculated.

[0074] After solving for the characteristic roots of the grid-connected system in the time domain, the stability and oscillation frequency of the grid-connected system can be understood through the real and imaginary parts of the characteristic roots. Therefore, based on this application, the safe, reliable and stable operation of the grid-connected system can be better maintained.

[0075] Furthermore, this application starts with easily obtainable frequency domain information, determines the damping ratio through the aggregate impedance amplitude frequency response curve and minimum point of the grid-connected system, and thus calculates the characteristic roots of the grid-connected system. This reduces the difficulty of obtaining information in the process of calculating the characteristic roots of the grid-connected system, making this application easier to implement and improving its practicality and applicability.

[0076] In some embodiments of this application, the process of plotting the aggregate impedance amplitude-frequency response curve of the grid-connected system in step S2 is described in detail, and the steps are as follows:

[0077] S20. Determine the power equipment impedance matrix of the grid-connected system in the frequency range, and the grid impedance matrix of the grid-connected system in the frequency range.

[0078] Specifically, a grid-connected system includes electrical equipment and a power grid. The connection point between the electrical equipment and the power grid is called the grid connection point. At the grid connection point, there is a three-phase voltage. The three-phase current flowing from the grid connection point to the electrical equipment is called the first three-phase current, and the three-phase current flowing from the grid connection point to the power grid is called the second three-phase current. The terms first and second three-phase currents are used only to distinguish between the three-phase currents flowing to the electrical equipment and those flowing to the power grid; they do not imply a sequential or magnitude relationship between the first and second three-phase currents.

[0079] Specifically, the power equipment impedance matrix represents the frequency response relationship between the voltage and current of any phase of the power equipment, while the power grid impedance matrix represents the frequency response relationship between the voltage and current of any phase of the power grid. Therefore, each element of the power equipment impedance matrix and the power grid impedance matrix is ​​frequency-dependent.

[0080] The impedance matrix of the power equipment and the impedance matrix of the grid-connected system within the specified frequency range can be determined in various ways. For example, the impedance matrix of the power equipment and the impedance matrix of the grid-connected system within the specified frequency range can be determined using circuit information such as voltage and current, as well as grid-connected system control parameters. Alternatively, the frequency of the grid-connected system simulation model can be directly adjusted, and impedance scans of the simulation model at various frequencies can be performed to obtain the impedance matrix of the power equipment and the impedance matrix of the grid.

[0081] S21. Based on the power equipment impedance matrix and the power grid impedance matrix, plot the aggregate impedance amplitude frequency response curve of the grid-connected system.

[0082] Specifically, the aggregate impedance amplitude can be obtained from the impedance matrix of the power equipment and the impedance matrix of the power grid. Since the impedance matrix of the power equipment and the impedance matrix of the power grid are related to the frequency, the aggregate impedance amplitude is related to the frequency. Based on this, the frequency response curve of the aggregate impedance amplitude of the grid-connected system can be plotted according to the correspondence between the aggregate impedance amplitude and the frequency.

[0083] As can be seen from the above technical solution, this embodiment provides an optional method for plotting the aggregate impedance amplitude-frequency response curve of a grid-connected system. Using this method, the correspondence between the aggregate impedance amplitude and frequency can be determined based on readily available power equipment impedance matrices and grid impedance matrices, and the aggregate impedance amplitude-frequency response curve of the grid-connected system can be plotted based on this relationship. Therefore, this application can better plot the aggregate impedance amplitude-frequency response curve of a grid-connected system.

[0084] In some embodiments of this application, the process of S20, determining the power equipment impedance matrix of the grid-connected system in the frequency range, and the grid impedance matrix of the grid-connected system in the frequency range are described in detail, and the steps are as follows:

[0085] S200. Based on the circuit parameters and control parameters of the power equipment in the grid-connected system, determine the frequency response relationship between the terminal voltage and terminal current of the power equipment within the frequency range. The frequency response relationship between the terminal voltage and terminal circuit of the power equipment is the impedance matrix of the power equipment.

[0086] Specifically, the three phases include phase A, phase B, and phase C. Therefore, at the grid connection point, there are phase A voltage, phase B voltage, and phase C voltage. There are first phase A current, first phase B current, and first phase C current flowing from the grid connection point to the power equipment, and second phase A current, second phase B current, and second phase C current flowing from the grid connection point to the power grid.

[0087] Based on the circuit parameters and control parameters of the power equipment in the grid-connected system, the frequency response relationship between Va(f), Va(2×fb-f) and I1a(f), I1a(2×fb-f) can be determined. This frequency response relationship is denoted as ZA(f), which is the impedance matrix of the power equipment.

[0088] Where Va(f) is the A-phase voltage at the grid connection point corresponding to frequency f, Va(2×fb-f) is the A-phase voltage at the grid connection point corresponding to frequency 2×fb-f, I1a(f) is the first A-phase current corresponding to frequency f, I1a(2×fb-f) is the first A-phase current corresponding to frequency 2×fb-f, and fb represents the fundamental frequency of the power grid.

[0089] S201. Based on the circuit parameters and control parameters of the power grid in the grid-connected system, determine the frequency response relationship between the terminal voltage and terminal current of the power grid within the frequency range. The frequency response relationship between the terminal voltage and terminal circuit of the power grid is the power grid impedance matrix.

[0090] Specifically, based on the circuit parameters and control parameters of the power grid in the grid-connected system, the frequency response relationship between Va(f), Va(2×fb-f) and I2a(f), I2a(2×fb-f) can be determined. This frequency response relationship is denoted as ZB(f), where ZB(f) is the power grid impedance matrix.

[0091] Where I2a(f) is the second phase A current corresponding to frequency f, and I2a(2×fb-f) is the second phase A current corresponding to frequency 2×fb-f.

[0092] It should be noted that the frequency response relationship between the voltage and current of any phase can be determined. Here, only phase A is used as an example. Similarly, the frequency response relationship between the voltage and current of phase B or phase C can be determined, thereby determining the impedance matrix of the power equipment and the impedance matrix of the power grid.

[0093] As can be seen from the above technical solution, this embodiment provides an optional method for determining the impedance matrix of power equipment and the impedance matrix of the power grid. Through the above method, the impedance matrix of power equipment and the impedance matrix of the power grid can be calculated by the circuit parameters and control parameters in the grid-connected system, the voltage and current of the power equipment and the voltage and current of the power grid. The circuit parameters and control parameters, the voltage and current of the power equipment and the voltage and current of the power grid are easy to obtain and the calculation is relatively simple, which can further improve the applicability of this application.

[0094] In some embodiments of this application, the process of step S21, which involves plotting the aggregate impedance amplitude frequency response curve of the grid-connected system based on the power equipment impedance matrix and the grid impedance matrix, is described in detail below:

[0095] S210. Determine the frequency interval based on the frequency range.

[0096] Specifically, the frequency range can be [f1, f2]. When f2 does not exceed 100Hz, the frequency interval can be 0.01Hz; when f1 exceeds 100Hz and f2 is not less than 300Hz, the frequency interval can be 0.1Hz; when f2 exceeds 300Hz, the frequency interval can be 1Hz.

[0097] S211. Within the frequency range, frequency points are set at intervals of the frequency interval to obtain multiple frequency points.

[0098] Specifically, with f1 as the first frequency point, a frequency point is set for each subsequent frequency interval until f2 is exceeded, resulting in multiple frequency points within the frequency range.

[0099] S212. Determine the aggregate impedance amplitude corresponding to each frequency point based on the power equipment impedance matrix and the power grid impedance matrix.

[0100] Specifically, the composition of the impedance matrix of the power equipment is as follows:

[0101]

[0102] The composition of the power grid impedance matrix is ​​shown below:

[0103]

[0104] Based on the composition of the power equipment impedance matrix and the power grid impedance matrix, the formula for calculating the aggregate impedance magnitude can be determined as follows:

[0105] Ztot(f) = [ZA 11 (f)+ZB 11 (f)]×[ZA 22(f)+ZB 22 (f)]-[ZA 12 (f)+ZB 12 (f)]×[ZA 21 (f)+ZB 21 (f)]

[0106] Ztot(f) is the amplitude of the polymer impedance at frequency f, where f is any frequency point.

[0107] Therefore, by determining the impedance matrix of the power equipment and the impedance matrix of the power grid equipment at each frequency point, the aggregate impedance amplitude at each frequency point can be obtained.

[0108] S213. Based on each frequency point and its corresponding aggregate impedance amplitude, plot the aggregate impedance amplitude frequency response curve of the grid-connected system.

[0109] Specifically, the frequency response curve of the aggregate impedance amplitude of the grid-connected system is plotted with each frequency point as the abscissa and the aggregate impedance amplitude corresponding to that frequency point as the ordinate.

[0110] As can be seen from the above technical solution, this embodiment provides an optional method for plotting the aggregate impedance amplitude frequency response curve of a grid-connected system. Through the above process, the aggregate impedance corresponding to each frequency point within each frequency range can be calculated using the power equipment impedance matrix and the grid impedance matrix. Based on this, the aggregate impedance amplitude frequency response curve of the grid-connected system is plotted. It is evident that this application can further determine the frequency interval based on the frequency range, thereby determining the number of plotting points based on the frequency range. This further improves the efficiency of this application by reducing the number of plotting points while ensuring the reliability of plotting the aggregate impedance amplitude frequency response curve of the grid-connected system.

[0111] In some embodiments of this application, the process of determining the damping ratio of the characteristic root of the grid-connected system based on the minimum point is described in detail, and the steps are as follows:

[0112] S30. Based on the range of values ​​of the characteristic root damping ratio of the grid-connected system, construct an arithmetic progression array of damping ratios, wherein the arithmetic progression array of damping ratios contains multiple damping ratio values.

[0113] Specifically, the damping ratio ξ ranges from [-1 to 1].

[0114] The tolerance can be determined in advance based on the required accuracy of the estimated damping ratio, and an arithmetic progression array of the damping ratio ξ can be constructed based on the tolerance and the range of values ​​for the damping ratio ξ.

[0115] Generally, the tolerance can be 0.01. Then, the arithmetic progression array of damping ratios that can be constructed is shown below:

[0116] ξ=[-1,-0.99,…-1+(N-1)×0.01,…1]

[0117] N represents the Nth damping ratio value in the arithmetic progression array of damping ratios.

[0118] S31. Based on the minimum point, calculate the target aggregate impedance value corresponding to each damping ratio value in the damping ratio arithmetic array at each frequency point.

[0119] Specifically, the target polymer impedance value corresponding to each damping ratio value at that frequency point can be determined based on the magnitude of the minimum point and each frequency point.

[0120] S32. Calculate the difference between the target aggregate impedance value and the aggregate impedance amplitude at each frequency point for each damping ratio value, and obtain multiple differences corresponding to each damping ratio value. The aggregate impedance amplitude at that frequency point is the aggregate impedance amplitude corresponding to that frequency point in the aggregate impedance amplitude frequency response curve of the grid-connected system.

[0121] Specifically, the polymer impedance amplitude at each frequency point can be determined from the polymer impedance amplitude-frequency response curve. The target polymer impedance value at each frequency point corresponding to each damping ratio value is compared with the polymer impedance amplitude at each frequency point to obtain the difference corresponding to that damping ratio value at each frequency point.

[0122] S33. Calculate the root mean square error corresponding to each damping ratio value based on the multiple differences corresponding to each damping ratio value.

[0123] Specifically, the root mean square error corresponding to a damping ratio value can be calculated based on the formula for calculating the root mean square error and the multiple differences corresponding to each damping ratio value.

[0124] The formula for calculating the root mean square error is as follows:

[0125]

[0126]

[0127] Where, N f This represents the total number of frequency points within the frequency range [f1, f2]. i ) represents the difference between any damping ratio value in the arithmetic progression array of damping ratios at the i-th frequency point.

[0128] Therefore, we can first calculate the average difference corresponding to each damping ratio value, then calculate the difference between the difference corresponding to each frequency point of the damping ratio value and the average difference based on the average difference, add the differences between the differences corresponding to each frequency point and the average difference to obtain the sum of the differences between the differences corresponding to each frequency point and the average difference, and calculate the ratio between the sum and the total number of frequency points. This ratio is the root mean square error corresponding to the damping ratio value.

[0129] S34. Select the damping ratio with the smallest root mean square error as the damping ratio of the characteristic root of the grid-connected system.

[0130] Specifically, the smallest mean square error means that the damping ratio value has the shortest Euclidean distance between the target aggregate impedance value and the aggregate impedance amplitude at each frequency point, and the difference is small. Therefore, the mean square errors can be sorted according to their absolute values, and the damping ratio value corresponding to the smallest mean square error can be selected as the damping ratio of the characteristic root of the grid-connected system.

[0131] As can be seen from the above technical solution, this embodiment provides an optional method for estimating the damping ratio of the characteristic roots of a grid-connected system. The damping ratio estimated by the above method has high accuracy, and the reliability and accuracy of the damping ratio estimation in this application can be improved by adjusting the number of frequency points and the frequency interval, thereby improving the reliability of this application.

[0132] In some embodiments of this application, the process of step S31, which involves calculating the target aggregate impedance value corresponding to each damping ratio value in the arithmetic progression array of damping ratios at each frequency point based on the minimum point, is described in detail below:

[0133] S310. Using the damping ratio arithmetic array, the real and imaginary parts of the aggregate impedance amplitude at the minimum point, calculate the target aggregate impedance value corresponding to the damping ratio value at each frequency point.

[0134] Specifically, the horizontal axis of the minimum point is the frequency, and the vertical axis is the amplitude of the aggregate impedance. The amplitude of the aggregate impedance includes both real and imaginary parts. Based on the real and imaginary parts of the amplitude of the aggregate impedance at the minimum point, the target aggregate impedance value of each damping ratio at each frequency point can be determined.

[0135] As can be seen from the above technical solution, this embodiment provides an optional method for calculating the target aggregate impedance value of each damping ratio value at each frequency point using the minimum point. Through the above method, we can focus on the vertical coordinate of the minimum point and calculate the target aggregate impedance value of each damping ratio value at each frequency point, thereby better calculating the target aggregate impedance value of each damping ratio value at each frequency point.

[0136] In some embodiments of this application, the process of calculating the target aggregate impedance value corresponding to each frequency point using each damping ratio value in the arithmetic progression array of damping ratios and the real and imaginary parts of the aggregate impedance amplitude at the minimum point is described in detail below:

[0137] S3100, Substitute each damping ratio value in the arithmetic progression array of damping ratios, the real part and the imaginary part of the aggregate impedance amplitude at the minimum point into the preset estimation formula, and calculate the target aggregate impedance value corresponding to the damping ratio value at each frequency point.

[0138] The estimation formula is as follows:

[0139]

[0140]

[0141]

[0142] Among them, Rtot(f d Xtot(f) is the real part of the aggregation impedance magnitude at the minimum point. d f is the imaginary part of the magnitude of the polymer impedance at the minimum point. d Let f be the frequency corresponding to the minimum point, f be any frequency point, ξ(N) be the Nth damping ratio value in the arithmetic progression array of damping ratios, and Zni(f) be the target polymer impedance value.

[0143] As can be seen from the above technical solution, this embodiment provides an optional method for calculating the target aggregate impedance value corresponding to the damping ratio value at each frequency point by using the real and imaginary parts of the aggregate impedance amplitude at the minimum point. Through the above method, the target aggregate impedance can be directly calculated, thereby improving the reliability of this application.

[0144] The following describes the characteristic root calculation device for a grid-connected system provided in the embodiments of this application. The characteristic root calculation device for a grid-connected system described below can be referred to in correspondence with the characteristic root calculation method for a grid-connected system described above.

[0145] See Figure 2 , Figure 2 This is a schematic diagram of the structure of a grid-connected system characteristic root calculation device disclosed in an embodiment of this application.

[0146] like Figure 2 As shown, the characteristic root calculation device for the grid-connected system may include:

[0147] Estimation unit 1 is used to estimate the frequency range corresponding to the characteristic roots of the grid-connected system;

[0148] Plotting unit 2 is used to plot the aggregate impedance amplitude frequency response curve of the grid-connected system and determine the minimum point of the aggregate impedance amplitude frequency response curve of the grid-connected system within the frequency range.

[0149] Determining unit 3 is used to determine the damping ratio of the characteristic root of the grid-connected system based on the minimum point;

[0150] Calculation unit 4 is used to calculate the characteristic roots of the grid-connected system based on the damping ratio.

[0151] Optionally, the drawing unit may include:

[0152] An impedance matrix determination subunit is used to determine the power equipment impedance matrix of the grid-connected system in the frequency range, and the grid impedance matrix of the grid-connected system in the frequency range;

[0153] The curve plotting subunit is used to plot the aggregate impedance amplitude frequency response curve of the grid-connected system based on the impedance matrix of the power equipment and the impedance matrix of the power grid.

[0154] Optionally, the impedance matrix determination sub-unit may include:

[0155] The first impedance matrix determination subunit is used to determine the frequency response relationship between the terminal voltage and terminal current of the power equipment within the frequency range based on the circuit parameters and control parameters of the power equipment in the grid-connected system. The frequency response relationship between the terminal voltage and terminal circuit of the power equipment is the impedance matrix of the power equipment.

[0156] The second impedance matrix determination subunit is used to determine the frequency response relationship between the terminal voltage and terminal current of the power grid within the frequency range based on the circuit parameters and control parameters of the power grid in the grid-connected system. The frequency response relationship between the terminal voltage and terminal circuit of the power grid is the power grid impedance matrix.

[0157] Optionally, the curve plotting subunit may include:

[0158] The first curve plotting subunit is used to determine the frequency interval based on the frequency range;

[0159] The second curve plotting subunit is used to set frequency points every frequency interval within the frequency range to obtain multiple frequency points.

[0160] The third curve plotting subunit is used to determine the aggregate impedance amplitude corresponding to each frequency point based on the power equipment impedance matrix and the power grid impedance matrix.

[0161] The fourth curve plotting subunit is used to plot the frequency response curve of the aggregate impedance amplitude of the grid-connected system based on each frequency point and its corresponding aggregate impedance amplitude.

[0162] Optionally, the determining unit may include:

[0163] An array construction sub-unit is used to construct an arithmetic progression array of damping ratios based on the range of values ​​of the characteristic root damping ratio of the grid-connected system. The arithmetic progression array of damping ratios contains multiple damping ratio values.

[0164] The impedance calculation subunit is used to calculate the target aggregate impedance value corresponding to each damping ratio value in the damping ratio arithmetic array at each frequency point based on the minimum point.

[0165] The difference calculation subunit is used to calculate the difference between the target aggregate impedance value and the aggregate impedance amplitude at each frequency point for each damping ratio value, and to obtain multiple differences corresponding to each damping ratio value. The aggregate impedance amplitude at that frequency point is the aggregate impedance amplitude corresponding to that frequency point in the aggregate impedance amplitude frequency response curve of the grid-connected system.

[0166] The root mean square error calculation subunit is used to calculate the root mean square error corresponding to each damping ratio value based on multiple differences corresponding to each damping ratio value.

[0167] The damping ratio selection sub-unit is used to select the damping ratio value with the smallest mean square error as the damping ratio of the characteristic root of the grid-connected system.

[0168] Optionally, the impedance calculation subunit may include:

[0169] The arithmetic progression array uses sub-units to calculate the target aggregate impedance value corresponding to the damping ratio value at each frequency point using each damping ratio value in the arithmetic progression array, the real part and the imaginary part of the aggregate impedance amplitude at the minimum point.

[0170] Optionally, the arithmetic progression array can utilize sub-cells that include:

[0171] The estimation formula utilizes a sub-unit to substitute the real and imaginary parts of each damping ratio value in the arithmetic progression array of damping ratios and the aggregate impedance amplitude at the minimum point into a preset estimation formula to calculate the target aggregate impedance value corresponding to the damping ratio value at each frequency point.

[0172] The estimation storage subunit is used to store the estimation formulas shown below:

[0173]

[0174]

[0175]

[0176] Among them, Rtot(f d Xtot(f) is the real part of the aggregation impedance magnitude at the minimum point. d f is the imaginary part of the magnitude of the polymer impedance at the minimum point. d Let f be the frequency corresponding to the minimum point, f be any value within the frequency range, ξ(N) be any damping ratio value in the arithmetic progression array of damping ratios, and Zni(f) be the target aggregate impedance value.

[0177] The grid-connected system characteristic root calculation device provided in this application embodiment can be applied to grid-connected system characteristic root calculation equipment, such as PC terminals, cloud platforms, servers, and server clusters. Optionally, Figure 3 The hardware structure block diagram of the characteristic root calculation device for the grid-connected system is shown. (Refer to...) Figure 3 The hardware structure of the characteristic root calculation device of the grid-connected system may include: at least one processor 1, at least one communication interface 2, at least one memory 3 and at least one communication bus 4;

[0178] In this embodiment of the application, the number of processor 1, communication interface 2, memory 3, and communication bus 4 is at least one, and processor 1, communication interface 2, and memory 3 communicate with each other through communication bus 4;

[0179] Processor 1 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention.

[0180] Memory 3 may include high-speed RAM, and may also include non-volatile memory, such as at least one disk storage device;

[0181] The memory stores a program, which the processor can call. The program is used for:

[0182] Estimate the frequency range corresponding to the characteristic roots of the grid-connected system;

[0183] Plot the aggregate impedance amplitude-frequency response curve of the grid-connected system, and determine the minimum point of the aggregate impedance amplitude-frequency response curve of the grid-connected system within the specified frequency range.

[0184] Based on the minimum point, determine the damping ratio of the characteristic root of the grid-connected system;

[0185] The characteristic roots of the grid-connected system are calculated based on the damping ratio.

[0186] Optionally, the refined and extended functions of the program can be referred to the above description.

[0187] This application embodiment also provides a readable storage medium that can store a program suitable for execution by a processor, the program being used for:

[0188] Estimate the frequency range corresponding to the characteristic roots of the grid-connected system;

[0189] Plot the aggregate impedance amplitude-frequency response curve of the grid-connected system, and determine the minimum point of the aggregate impedance amplitude-frequency response curve of the grid-connected system within the specified frequency range.

[0190] Based on the minimum point, determine the damping ratio of the characteristic root of the grid-connected system;

[0191] The characteristic roots of the grid-connected system are calculated based on the damping ratio.

[0192] Optionally, the refined and extended functions of the program can be referred to the above description.

[0193] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0194] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0195] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. The various embodiments of this application can be combined with each other. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating the characteristic roots of a grid-connected system, characterized in that, include: Estimate the frequency range corresponding to the characteristic roots of the grid-connected system, wherein the frequency range contains multiple frequency points; Plot the aggregate impedance amplitude-frequency response curve of the grid-connected system, and determine the minimum point of the aggregate impedance amplitude-frequency response curve of the grid-connected system within the specified frequency range. Determining the damping ratio of the characteristic root of the grid-connected system based on the minimum point includes: constructing an arithmetic progression array of damping ratios based on the range of values ​​for the damping ratios of the characteristic root of the grid-connected system, wherein the arithmetic progression array contains multiple damping ratio values; calculating the target aggregate impedance value corresponding to each damping ratio value at each frequency point based on the minimum point; calculating the difference between the target aggregate impedance value and the aggregate impedance amplitude at each frequency point for each damping ratio value, thereby obtaining multiple differences corresponding to each damping ratio value, wherein the aggregate impedance amplitude at that frequency point is the aggregate impedance amplitude corresponding to that frequency point in the frequency response curve of the aggregate impedance amplitude of the grid-connected system; calculating the root mean square error corresponding to each damping ratio value based on the multiple differences; and selecting the damping ratio value with the smallest root mean square error as the damping ratio of the characteristic root of the grid-connected system. The characteristic roots of the grid-connected system are calculated based on the damping ratio.

2. The method for calculating the characteristic roots of a grid-connected system according to claim 1, characterized in that, The grid connection system refers to the connection of power equipment into the power grid system; The plotting of the aggregate impedance amplitude-frequency response curve of the grid-connected system includes: Determine the power equipment impedance matrix of the grid-connected system in the frequency range, and the grid impedance matrix of the grid-connected system in the frequency range; Based on the impedance matrix of the power equipment and the impedance matrix of the power grid, plot the aggregate impedance amplitude frequency response curve of the grid-connected system.

3. The method for calculating the characteristic roots of a grid-connected system according to claim 2, characterized in that, Determining the power equipment impedance matrix of the grid-connected system in the frequency range, and the grid impedance matrix of the grid-connected system in the frequency range, includes: Based on the circuit parameters and control parameters of the power equipment in the grid-connected system, the frequency response relationship between the terminal voltage and terminal current of the power equipment is determined within the frequency range, and the frequency response relationship between the terminal voltage and terminal circuit of the power equipment is the impedance matrix of the power equipment. Based on the circuit parameters and control parameters of the power grid in the grid-connected system, the frequency response relationship between the terminal voltage and terminal current of the power grid within the specified frequency range is determined, and the frequency response relationship between the terminal voltage and terminal circuit of the power grid is the power grid impedance matrix.

4. The method for calculating the characteristic roots of a grid-connected system according to claim 2, characterized in that, Based on the impedance matrix of the power equipment and the impedance matrix of the power grid, plot the aggregate impedance amplitude frequency response curve of the grid-connected system, including: Determine the frequency interval based on the frequency range; Within the frequency range, frequency points are set at intervals of the frequency interval to obtain multiple frequency points; Based on the power equipment impedance matrix and the power grid impedance matrix, determine the aggregate impedance amplitude corresponding to each frequency point; Based on each frequency point and its corresponding aggregate impedance amplitude, plot the aggregate impedance amplitude frequency response curve of the grid-connected system.

5. The method for calculating the characteristic roots of a grid-connected system according to claim 1, characterized in that, Based on the minimum point, calculate the target aggregate impedance value corresponding to each damping ratio value at each frequency point in the arithmetic progression array of damping ratios, including: Using the damping ratio arithmetic progression array, the real and imaginary parts of the aggregate impedance amplitude at the minimum point, the target aggregate impedance value corresponding to the damping ratio value at each frequency point is calculated.

6. The method for calculating the characteristic roots of a grid-connected system according to claim 5, characterized in that, Using each damping ratio value in the arithmetic progression array of damping ratios, and the real and imaginary parts of the aggregate impedance amplitude at the minimum point, the target aggregate impedance value corresponding to the damping ratio value at each frequency point is calculated, including: Substitute each damping ratio value in the arithmetic progression array of damping ratios, the real part and the imaginary part of the aggregate impedance amplitude at the minimum point into the preset estimation formula to calculate the target aggregate impedance value corresponding to the damping ratio value at each frequency point. The estimation formula is as follows: in, Let be the real part of the polymerization impedance magnitude at the minimum point. This represents the imaginary part of the polymerization impedance amplitude at the minimum point. The frequency corresponding to the minimum point. For frequencies within the specified frequency range, Let be any one of the damping ratio values ​​in the arithmetic progression array of damping ratios. The target polymerization impedance value; As the first intermediate variable; It is the second intermediate variable.

7. A characteristic root calculation device for a grid-connected system, characterized in that, include: An estimation unit is used to estimate the frequency range corresponding to the characteristic roots of the grid-connected system; The plotting unit is used to plot the aggregate impedance amplitude frequency response curve of the grid-connected system and determine the minimum point of the aggregate impedance amplitude frequency response curve of the grid-connected system within the frequency range. A determining unit is configured to determine the damping ratio of the characteristic root of the grid-connected system based on the minimum point, comprising: constructing an arithmetic progression array of damping ratios based on the range of values ​​for the damping ratios of the characteristic root of the grid-connected system, wherein the arithmetic progression array contains multiple damping ratio values; calculating the target aggregate impedance value corresponding to each damping ratio value in the arithmetic progression array at each frequency point based on the minimum point; calculating the difference between the target aggregate impedance value and the aggregate impedance amplitude at each frequency point for each damping ratio value, thereby obtaining multiple differences corresponding to each damping ratio value, wherein the aggregate impedance amplitude at that frequency point is the aggregate impedance amplitude corresponding to that frequency point in the frequency response curve of the aggregate impedance amplitude of the grid-connected system; calculating the root mean square error corresponding to each damping ratio value based on the multiple differences corresponding to each damping ratio value; and selecting the damping ratio value with the smallest root mean square error as the damping ratio of the characteristic root of the grid-connected system. The calculation unit is used to calculate the characteristic roots of the grid-connected system based on the damping ratio.

8. A characteristic root calculation device for a grid-connected system, characterized in that, Including memory and processor; The memory is used to store programs; The processor is used to execute the program to implement each step of the grid-connected system characteristic root calculation method as described in any one of claims 1-6.

9. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements each step of the grid-connected system characteristic root calculation method as described in any one of claims 1-6.

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