Broadband oscillation risk identification method and device

Abstract

The invention discloses a broadband oscillation risk identification method and device, and the method comprises the steps: obtaining the operation parameters of power electronic equipment, a first amplitude-frequency response characteristic curve of the power electronic equipment in a preset frequency band range, and a first transfer function of a power system, and then obtaining the operation parameters of the power electronic equipment according to the first amplitude-frequency response characteristic curve; determining the order of a transfer function of the power electronic equipment according to the operation parameters, then fitting according to the order of the transfer function and the operation parameters to obtain a second transfer function of the power electronic equipment, and combining the first transfer function and the second transfer function to obtain a third transfer function for representing the performance of the grid-connected system. And finally, according to the third transfer function, identifying the broadband oscillation risk of the grid-connected system. According to the invention, the identification efficiency of the transfer function can be improved, and the purpose of improving the identification precision of the broadband oscillation risk between the power electronic equipment and the power system is achieved.

Description

Technical Field

[0001] The present invention relates to the field of power system risk identification, and in particular to a broadband oscillation risk identification method and device. Background Art

[0002] The transfer function is a tool for describing the input-output relationship of a linear time-invariant system. Its form is usually expressed as the ratio of a numerator polynomial to a denominator polynomial. Determining the transfer function is of great help in identifying the risk of broadband oscillations in power systems.

[0003] However, in the process of determining the transfer function, choosing too low an order may not fully capture the dynamic characteristics of the system; choosing too high an order will increase unnecessary computational burden and may introduce noise and errors. Observing the step response or impulse response of the system is one of the traditional methods for determining the order, but this method has limitations. For simple low-order systems, the order of the system can be roughly estimated by observing the shape and decay rate of the response curve. However, when the system order is high, its time domain response becomes extremely complex, making it extremely difficult to accurately estimate the system order, resulting in low accuracy in identifying broadband oscillation risks between power electronic equipment and power systems. Summary of the invention

[0004] The present invention provides a method and device for identifying broadband oscillation risks, which can improve the efficiency of transfer function identification to achieve the purpose of improving the accuracy of broadband oscillation risk identification between power electronic equipment and power systems.

[0005] An embodiment of the present invention provides a method for identifying broadband oscillation risk, comprising:

[0006] Acquiring operating parameters of the power electronic device, a first amplitude-frequency response characteristic curve of the power electronic device within a preset frequency band, and a first transfer function of the power system;

[0007] Determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve;

[0008] According to the order of the transfer function and the operating parameters, fitting and obtaining a second transfer function of the power electronic device;

[0009] Combining the first transfer function and the second transfer function, obtaining a third transfer function for characterizing the performance of a grid-connected system; wherein the grid-connected system is formed by the power electronic device and the power system being connected to the grid;

[0010] The broadband oscillation risk of the grid-connected system is identified according to the third transfer function.

[0011] Further, determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve includes:

[0012] Create a recognition window with a width of M, where M is greater than 0;

[0013] According to the identification window, traverse the first amplitude-frequency response characteristic curve, and screen and obtain a first minimum value point of the first amplitude-frequency response characteristic curve;

[0014] Calculating a first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies;

[0015] Performing a reciprocal operation on all sampling points in the first amplitude-frequency response characteristic curve, and forming a second amplitude-frequency response characteristic curve based on all sampling points after the reciprocal operation is performed;

[0016] According to the identification window, traverse the second amplitude-frequency response characteristic curve, and screen and obtain a second minimum value point of the second amplitude-frequency response characteristic curve;

[0017] Calculating a second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies;

[0018] The order of the transfer function of the power electronic device is determined according to the first minimum point, the first order difference, the second minimum point, and the second order difference.

[0019] Further, the first order difference is calculated according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies, including:

[0020] Obtaining a first initial amplitude-frequency response corresponding to a first frequency and a second initial amplitude-frequency response corresponding to a second frequency in a first amplitude-frequency response characteristic curve; wherein a ratio of the second frequency to the first frequency is less than a preset scaling factor;

[0021] Initializing a first parameter for characterizing the order difference between a numerator and a denominator of a transfer function;

[0022] Based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response, repeatedly performing a first iterative calculation operation until an iteration termination condition is satisfied, stopping the first iterative calculation operation, and obtaining a first order difference;

[0023] The first iterative calculation operation includes:

[0024] Determine whether the ratio of the current second amplitude-frequency response to the current first amplitude-frequency response is less than N times the scaling factor, and determine whether the current first amplitude-frequency response is greater than a first preset value; wherein, when the first iterative calculation operation is performed for the first time, the current first amplitude-frequency response is the first initial amplitude-frequency response, and the current second amplitude-frequency response is the second initial amplitude-frequency response;

[0025] If the judgment results are all yes, then the first parameter is updated, the size of the current first amplitude-frequency response and the size of the current second amplitude-frequency response are adjusted, and the adjusted first amplitude-frequency response and second amplitude-frequency response are used as inputs for the next first iterative calculation operation;

[0026] On the contrary, it is confirmed that the iteration termination condition is met, the first iterative calculation operation is stopped, and the first parameter of this iterative calculation operation is used as the first order difference corresponding to the first amplitude-frequency response characteristic curve.

[0027] Further, the calculating and obtaining the second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies includes:

[0028] Obtaining a third initial amplitude-frequency response corresponding to a third frequency and a fourth initial amplitude-frequency response corresponding to a fourth frequency in the second amplitude-frequency response characteristic curve; wherein a ratio of the fourth frequency to the third frequency is less than a preset scaling factor;

[0029] Initializing a second parameter for characterizing the order difference between a numerator and a denominator of a transfer function;

[0030] Based on the second parameter, the third initial amplitude-frequency response and the fourth initial amplitude-frequency response, repeatedly performing a second iterative calculation operation until an iteration termination condition is satisfied, stopping the second iterative calculation operation, and obtaining a second order difference;

[0031] The second iterative calculation operation includes:

[0032] Determine whether the ratio of the current fourth amplitude-frequency response to the current third amplitude-frequency response is less than N times the scaling factor, and determine whether the current third amplitude-frequency response is greater than a second preset value; wherein, when the second iterative calculation operation is performed for the first time, the current third amplitude-frequency response is the third initial amplitude-frequency response, and the current fourth amplitude-frequency response is the fourth initial amplitude-frequency response;

[0033] If the judgment results are all yes, then the second parameter is updated, the size of the current third amplitude-frequency response and the size of the current fourth amplitude-frequency response are adjusted, and the adjusted third amplitude-frequency response and fourth amplitude-frequency response are used as inputs for the next second iterative calculation operation;

[0034] On the contrary, it is confirmed that the iteration termination condition is met, the second iterative calculation operation is stopped, and the second parameter of this iterative calculation operation is used as the second order difference corresponding to the second amplitude-frequency response characteristic curve.

[0035] Further, determining the order of the transfer function of the power electronic device according to the first minimum point, the first order difference, the second minimum point, and the second order difference includes:

[0036] Count the number of all first minimum points to get the first total number;

[0037] Count the number of all second minimum points to get the second total number;

[0038] determining a first preselected order of a transfer function of the power electronic device based on the first total number and the first order difference;

[0039] determining a second preselected order of a transfer function of the power electronic device based on the second total number and the second order difference;

[0040] The first preselected order and the second preselected order are compared, and the preselected order with a larger value is used as the order of the transfer function of the power electronic device.

[0041] An embodiment of the present invention further provides a broadband oscillation risk identification device, comprising: a data acquisition module, an order determination module, a power electronic device transfer function determination module, a grid-connected system transfer function determination module, and a broadband oscillation risk identification module;

[0042] The data acquisition module is used to acquire operating parameters of the power electronic device, a first amplitude-frequency response characteristic curve of the power electronic device within a preset frequency band, and a first transfer function of the power system;

[0043] The order determination module is used to determine the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve;

[0044] The power electronic device transfer function determination module is used to obtain a second transfer function of the power electronic device by fitting according to the order of the transfer function and the operating parameters;

[0045] The grid-connected system transfer function determination module is used to combine the first transfer function and the second transfer function to obtain a third transfer function for characterizing the performance of the grid-connected system; wherein the grid-connected system is formed by the power electronic device and the power system being connected to the grid;

[0046] The broadband oscillation risk identification module is used to identify the broadband oscillation risk of the grid-connected system according to the third transfer function.

[0047] Further, determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve includes:

[0048] Create a recognition window with a width of M, where M is greater than 0;

[0049] According to the identification window, traverse the first amplitude-frequency response characteristic curve, and screen and obtain a first minimum value point of the first amplitude-frequency response characteristic curve;

[0050] Calculating a first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies;

[0051] Performing a reciprocal operation on all sampling points in the first amplitude-frequency response characteristic curve, and forming a second amplitude-frequency response characteristic curve based on all sampling points after the reciprocal operation is performed;

[0052] According to the identification window, traverse the second amplitude-frequency response characteristic curve, and screen and obtain a second minimum value point of the second amplitude-frequency response characteristic curve;

[0053] Calculating a second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies;

[0054] The order of the transfer function of the power electronic device is determined according to the first minimum point, the first order difference, the second minimum point, and the second order difference.

[0055] Further, the first order difference is calculated according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies, including:

[0056] Obtaining a first initial amplitude-frequency response corresponding to a first frequency and a second initial amplitude-frequency response corresponding to a second frequency in a first amplitude-frequency response characteristic curve; wherein a ratio of the second frequency to the first frequency is less than a preset scaling factor;

[0057] Initializing a first parameter for characterizing the order difference between a numerator and a denominator of a transfer function;

[0058] Based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response, repeatedly performing a first iterative calculation operation until an iteration termination condition is satisfied, stopping the first iterative calculation operation, and obtaining a first order difference;

[0059] The first iterative calculation operation includes:

[0060] Determine whether the ratio of the current second amplitude-frequency response to the current first amplitude-frequency response is less than N times the scaling factor, and determine whether the current first amplitude-frequency response is greater than a first preset value; wherein, when the first iterative calculation operation is performed for the first time, the current first amplitude-frequency response is the first initial amplitude-frequency response, and the current second amplitude-frequency response is the second initial amplitude-frequency response;

[0061] If the judgment results are all yes, then the first parameter is updated, the size of the current first amplitude-frequency response and the size of the current second amplitude-frequency response are adjusted, and the adjusted first amplitude-frequency response and second amplitude-frequency response are used as inputs for the next first iterative calculation operation;

[0062] On the contrary, it is confirmed that the iteration termination condition is met, the first iterative calculation operation is stopped, and the first parameter of this iterative calculation operation is used as the first order difference corresponding to the first amplitude-frequency response characteristic curve.

[0063] Further, the calculating and obtaining the second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies includes:

[0064] Obtaining a third initial amplitude-frequency response corresponding to a third frequency and a fourth initial amplitude-frequency response corresponding to a fourth frequency in the second amplitude-frequency response characteristic curve; wherein a ratio of the fourth frequency to the third frequency is less than a preset scaling factor;

[0065] Initializing a second parameter for characterizing the order difference between a numerator and a denominator of a transfer function;

[0066] Based on the second parameter, the third initial amplitude-frequency response and the fourth initial amplitude-frequency response, repeatedly performing a second iterative calculation operation until an iteration termination condition is satisfied, stopping the second iterative calculation operation, and obtaining a second order difference;

[0067] The second iterative calculation operation includes:

[0068] Determine whether the ratio of the current fourth amplitude-frequency response to the current third amplitude-frequency response is less than N times the scaling factor, and determine whether the current third amplitude-frequency response is greater than a second preset value; wherein, when the second iterative calculation operation is performed for the first time, the current third amplitude-frequency response is the third initial amplitude-frequency response, and the current fourth amplitude-frequency response is the fourth initial amplitude-frequency response;

[0069] If the judgment results are all yes, then the second parameter is updated, the size of the current third amplitude-frequency response and the size of the current fourth amplitude-frequency response are adjusted, and the adjusted third amplitude-frequency response and fourth amplitude-frequency response are used as inputs for the next second iterative calculation operation;

[0070] On the contrary, it is confirmed that the iteration termination condition is met, the second iterative calculation operation is stopped, and the second parameter of this iterative calculation operation is used as the second order difference corresponding to the second amplitude-frequency response characteristic curve.

[0071] Further, determining the order of the transfer function of the power electronic device according to the first minimum point, the first order difference, the second minimum point, and the second order difference includes:

[0072] Count the number of all first minimum points to get the first total number;

[0073] Count the number of all second minimum points to get the second total number;

[0074] determining a first preselected order of a transfer function of the power electronic device based on the first total number and the first order difference;

[0075] determining a second preselected order of a transfer function of the power electronic device based on the second total number and the second order difference;

[0076] The first preselected order and the second preselected order are compared, and the preselected order with a larger value is used as the order of the transfer function of the power electronic device.

[0077] The following beneficial effects are achieved by implementing the present invention:

[0078] The present invention provides a method, device, equipment and medium for identifying broadband oscillation risks. The method determines the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve of the power electronic device within a preset frequency band, and then fits the second transfer function of the power electronic device according to the order of the transfer function and the operating parameters, and combines the first transfer function and the second transfer function to obtain a third transfer function corresponding to the grid-connected system, and then identifies the broadband oscillation risk of the grid-connected system according to the third transfer function;

[0079] Since the first amplitude-frequency response characteristic curve can intuitively reflect the gain and phase changes of power electronic equipment at different frequencies, and these changes are closely related to its internal dynamic characteristics (i.e., the order and parameters of the transfer function), by analyzing the first amplitude-frequency response characteristic curve, the order of the transfer function can be more accurately estimated, providing a basis for subsequent function fitting, and effectively improving the transfer function identification efficiency when fitting the transfer function in the subsequent process, so as to achieve the purpose of improving the accuracy of broadband oscillation risk identification between power electronic equipment and power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the implementation manner will be briefly introduced below. Obviously, the drawings described below are only some implementation manners of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0081] Figure 1 It is a flowchart of a broadband oscillation risk identification method provided in a certain embodiment of the present application;

[0082] Figure 2 It is a structural schematic diagram of a broadband oscillation risk identification device provided in a certain embodiment of the present application. DETAILED DESCRIPTION

[0083] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0084] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0085] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0086] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0087] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0088] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0089] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0090] See also Figure 1 , is a flow chart of a broadband oscillation risk identification method provided by an embodiment of the present invention, comprising:

[0091] S1, obtaining operating parameters of a power electronic device, a first amplitude-frequency response characteristic curve of the power electronic device within a preset frequency band, and a first transfer function of a power system;

[0092] S2. determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve;

[0093] In a preferred embodiment, determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve includes:

[0094] Create a recognition window with a width of M, where M is greater than 0;

[0095] According to the identification window, traverse the first amplitude-frequency response characteristic curve, and screen and obtain a first minimum value point of the first amplitude-frequency response characteristic curve;

[0096] Calculating a first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies;

[0097] Performing a reciprocal operation on all sampling points in the first amplitude-frequency response characteristic curve, and forming a second amplitude-frequency response characteristic curve based on all sampling points after the reciprocal operation is performed;

[0098] According to the identification window, traverse the second amplitude-frequency response characteristic curve, and screen and obtain a second minimum value point of the second amplitude-frequency response characteristic curve;

[0099] Calculating a second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies;

[0100] Determining the order of the transfer function of the power electronic device according to the first minimum point, the first order difference, the second minimum point, and the second order difference;

[0101] Specifically, the second transfer function G2 of the power electronic device is obtained in the preset frequency band range 0≤f≤f by frequency scanning (small signal injection test). s The first amplitude-frequency response characteristic curve L1 within the embodiment, wherein the frequency interval is Δf;

[0102] Then, a recognition window with a window width of M is created, and 2*ΔT+1 frequency points are searched in the recognition window. If the amplitude A corresponding to the ΔT+1th frequency point in the current recognition window is the minimum value in the current recognition window, then the frequency point will be identified as a first minimum point on the first amplitude-frequency response characteristic curve L1;

[0103] When traversing the first amplitude-frequency response characteristic curve L1, if the current recognition window does not search for the corresponding first minimum point, the recognition window moves to the right by 1 frequency point; if the current recognition window searches for the corresponding first minimum point, it moves to the right by ΔT frequency points;

[0104] Thus, the first amplitude-frequency response characteristic curve L1 is traversed to obtain a plurality of first minimum value points of the curve L1.

[0105] In a preferred embodiment, the calculating the first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies includes:

[0106] Obtaining a first initial amplitude-frequency response corresponding to a first frequency and a second initial amplitude-frequency response corresponding to a second frequency in a first amplitude-frequency response characteristic curve; wherein a ratio of the second frequency to the first frequency is less than a preset scaling factor;

[0107] Initializing a first parameter for characterizing the order difference between a numerator and a denominator of a transfer function;

[0108] Based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response, repeatedly performing a first iterative calculation operation until an iteration termination condition is satisfied, stopping the first iterative calculation operation, and obtaining a first order difference;

[0109] The first iterative calculation operation includes:

[0110] Determine whether the ratio of the current second amplitude-frequency response to the current first amplitude-frequency response is less than N times the scaling factor, and determine whether the current first amplitude-frequency response is greater than a first preset value; wherein, when the first iterative calculation operation is performed for the first time, the current first amplitude-frequency response is the first initial amplitude-frequency response, and the current second amplitude-frequency response is the second initial amplitude-frequency response;

[0111] If the judgment results are all yes, then the first parameter is updated, the size of the current first amplitude-frequency response and the size of the current second amplitude-frequency response are adjusted, and the adjusted first amplitude-frequency response and second amplitude-frequency response are used as inputs for the next first iterative calculation operation;

[0112] Otherwise, it is confirmed that the iteration termination condition is met, the first iterative calculation operation is stopped, and the first parameter of this iterative calculation operation is used as the first order difference corresponding to the first amplitude-frequency response characteristic curve;

[0113] Specifically, a first initial amplitude-frequency response A1 corresponding to a first frequency fs1 and a second initial amplitude-frequency response A2 corresponding to a second frequency fs2 in the first amplitude-frequency response characteristic curve L1 are obtained; the ratio of the second frequency fs2 to the first frequency fs1 satisfies Wherein, the scaling factor k satisfies the condition 0<k<1;

[0114] Then, the first parameter ΔM1 is initialized, and ΔM1=0;

[0115] Performing the first iterative calculation operation based on the first parameter ΔM1, the first initial amplitude-frequency response A1, and the second initial amplitude-frequency response A2;

[0116] When the first iterative calculation operation is performed for the first time, the ratio of the second initial amplitude-frequency response A2 to the first initial amplitude-frequency response A1 is determined. is less than N times N*k of the scaling factor, and whether the first initial amplitude-frequency response A1 is greater than a first preset value ω1;

[0117] If the judgment results are all yes, let ΔM1 = ΔM1 + 1, through To adjust the size of the first amplitude-frequency response, and, through the formula to adjust the size of the second amplitude-frequency response, use the adjusted first amplitude-frequency response and the second amplitude-frequency response as inputs of the next first iterative calculation operation, and perform the next first iterative calculation operation;

[0118] Otherwise, it is confirmed that the iteration termination condition is met, the first iterative calculation operation is stopped, and the first parameter ΔM1 of this iterative calculation operation is used as the first order difference corresponding to the first amplitude-frequency response characteristic curve;

[0119] It should be noted that N can be adjusted according to actual conditions; in this embodiment, N=1.05, ω1=π·fs1.

[0120] Illustratively, after obtaining the first order difference ΔM1 corresponding to the first amplitude-frequency response characteristic curve L1, performing a reciprocal operation on all sampling points in the first amplitude-frequency response characteristic curve, and forming a second amplitude-frequency response characteristic curve L2 based on all sampling points after reciprocal operation;

[0121] Similarly, the second amplitude-frequency response characteristic curve L2 is traversed through the identification window to search for 2*ΔT+1 frequency points in the identification window. If the amplitude A' corresponding to the ΔT+1th frequency point in the current identification window is the minimum value in the current identification window, then the frequency point will be identified as a second minimum point on the second amplitude-frequency response characteristic curve L2;

[0122] When traversing the second amplitude-frequency response characteristic curve L2, if the current recognition window does not search for the corresponding second minimum point, the recognition window moves to the right by 1 frequency point; if the current recognition window searches for the corresponding second minimum point, it moves to the right by ΔT frequency points;

[0123] Thus, the second amplitude-frequency response characteristic curve L2 is traversed to obtain a plurality of second minimum value points of the curve L2.

[0124] In a preferred embodiment, the calculating the second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies includes:

[0125] Obtaining a third initial amplitude-frequency response corresponding to a third frequency and a fourth initial amplitude-frequency response corresponding to a fourth frequency in the second amplitude-frequency response characteristic curve; wherein a ratio of the fourth frequency to the third frequency is less than a preset scaling factor;

[0126] Initializing a second parameter for characterizing the order difference between a numerator and a denominator of a transfer function;

[0127] Based on the second parameter, the third initial amplitude-frequency response and the fourth initial amplitude-frequency response, repeatedly performing a second iterative calculation operation until an iteration termination condition is satisfied, stopping the second iterative calculation operation, and obtaining a second order difference;

[0128] The second iterative calculation operation includes:

[0129] Determine whether the ratio of the current fourth amplitude-frequency response to the current third amplitude-frequency response is less than N times the scaling factor, and determine whether the current third amplitude-frequency response is greater than a second preset value; wherein, when the second iterative calculation operation is performed for the first time, the current third amplitude-frequency response is the third initial amplitude-frequency response, and the current fourth amplitude-frequency response is the fourth initial amplitude-frequency response;

[0130] If the judgment results are all yes, then the second parameter is updated, the size of the current third amplitude-frequency response and the size of the current fourth amplitude-frequency response are adjusted, and the adjusted third amplitude-frequency response and fourth amplitude-frequency response are used as inputs for the next second iterative calculation operation;

[0131] Otherwise, it is confirmed that the iteration termination condition is met, the second iterative calculation operation is stopped, and the second parameter of this iterative calculation operation is used as the second order difference corresponding to the second amplitude-frequency response characteristic curve;

[0132] Specifically, a third initial amplitude-frequency response A3 corresponding to the third frequency fs3 and a fourth initial amplitude-frequency response A4 corresponding to the fourth frequency fs4 in the second amplitude-frequency response characteristic curve L2 are obtained; the ratio of the fourth frequency fs4 to the third frequency fs3 satisfies Wherein, the scaling factor k satisfies the condition 0<k<1;

[0133] Then, the second parameter ΔM2 is initialized, and ΔM2=0;

[0134] performing the second iterative calculation operation based on the second parameter ΔM2, the third initial amplitude-frequency response A3, and the fourth initial amplitude-frequency response A4;

[0135] When the second iterative calculation operation is performed for the first time, the ratio of the fourth initial amplitude-frequency response A4 to the third initial amplitude-frequency response A3 is determined. is less than N times N*k of the scaling factor, and whether the third initial amplitude-frequency response A3 is greater than a second preset value ω2;

[0136] If the judgment results are all yes, let ΔM2 = ΔM2 + 1, through To adjust the size of the third amplitude-frequency response, and, through the formula to adjust the size of the fourth amplitude-frequency response, and use the adjusted third amplitude-frequency response and the fourth amplitude-frequency response as inputs of the next second iterative calculation operation, and perform the next second iterative calculation operation;

[0137] On the contrary, it is confirmed that the iteration termination condition is met, the second iterative calculation operation is stopped, and the second parameter ΔM2 of this iterative calculation operation is used as the second order difference corresponding to the second amplitude-frequency response characteristic curve;

[0138] It should be noted that N can be adjusted according to actual conditions; in this embodiment, N=1.05, ω2=π·fs3.

[0139] In a preferred embodiment, determining the order of the transfer function of the power electronic device according to the first minimum point, the first order difference, the second minimum point, and the second order difference includes:

[0140] Count the number of all first minimum points to get the first total number;

[0141] Count the number of all second minimum points to get the second total number;

[0142] determining a first preselected order of a transfer function of the power electronic device based on the first total number and the first order difference;

[0143] determining a second preselected order of a transfer function of the power electronic device based on the second total number and the second order difference;

[0144] comparing the first preselected order and the second preselected order, and using the preselected order with a larger value as the order of the transfer function of the power electronic device;

[0145] Specifically, the number of all first minimum value points is counted to obtain a first total number S1, and the number of all second minimum value points is counted to obtain a second total number S2;

[0146] Then, the first preselected order D1 is calculated by D1=S1*2+ΔM1; the second preselected order D2 is calculated by D2=S2*2+ΔM2;

[0147] Then, the first preselected order D1 and the second preselected order D2 are compared, and the preselected order with the larger value is used as the order O=max(D1, D2) of the transfer function of the power electronic device.

[0148] S3, fitting and obtaining a second transfer function of the power electronic device according to the order of the transfer function and the operating parameters;

[0149] Specifically, after the order O of the transfer function of the power electronic device is determined, the second transfer function G2 of the power electronic device is obtained by fitting according to the order O and the operating parameters of the power electronic device.

[0150] S4, combining the first transfer function and the second transfer function to obtain a third transfer function for characterizing the performance of a grid-connected system; wherein the grid-connected system is formed by the power electronic device and the power system being connected to the grid;

[0151] Specifically, according to the first transfer function G1 of the power system and the second transfer function G2 of the power electronic device, a third transfer function G3 is fitted, and the third transfer function G3 is used to characterize the performance of the entire grid-connected system formed by the power electronic device and the power system after being connected to the grid.

[0152] S5. Identifying the broadband oscillation risk of the grid-connected system according to the third transfer function;

[0153] Specifically, by observing the pole position of the third transfer function G3, the stability of the system can be judged. If the pole is located in the left half of the complex plane, the system is stable; if the pole is located in the right half of the complex plane or on the imaginary axis, the system may be unstable or oscillate.

[0154] See also Figure 2 , is a broadband oscillation risk identification device provided by an embodiment of the present invention, comprising: a data acquisition module, an order determination module, a power electronic device transfer function determination module, a grid-connected system transfer function determination module and a broadband oscillation risk identification module;

[0155] The data acquisition module is used to acquire operating parameters of the power electronic device, a first amplitude-frequency response characteristic curve of the power electronic device within a preset frequency band, and a first transfer function of the power system;

[0156] The order determination module is used to determine the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve;

[0157] The power electronic device transfer function determination module is used to obtain a second transfer function of the power electronic device by fitting according to the order of the transfer function and the operating parameters;

[0158] The grid-connected system transfer function determination module is used to combine the first transfer function and the second transfer function to obtain a third transfer function for characterizing the performance of the grid-connected system; wherein the grid-connected system is formed by the power electronic device and the power system being connected to the grid;

[0159] The broadband oscillation risk identification module is used to identify the broadband oscillation risk of the grid-connected system according to the third transfer function.

[0160] In a preferred embodiment, determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve includes:

[0161] Create a recognition window with a width of M, where M is greater than 0;

[0162] According to the identification window, traverse the first amplitude-frequency response characteristic curve, and screen and obtain a first minimum value point of the first amplitude-frequency response characteristic curve;

[0163] Calculating a first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies;

[0164] Performing a reciprocal operation on all sampling points in the first amplitude-frequency response characteristic curve, and forming a second amplitude-frequency response characteristic curve based on all sampling points after the reciprocal operation is performed;

[0165] According to the identification window, traverse the second amplitude-frequency response characteristic curve, and screen and obtain a second minimum value point of the second amplitude-frequency response characteristic curve;

[0166] Calculating a second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies;

[0167] The order of the transfer function of the power electronic device is determined according to the first minimum point, the first order difference, the second minimum point, and the second order difference.

[0168] In a preferred embodiment, the calculating the first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies includes:

[0169] Obtaining a first initial amplitude-frequency response corresponding to a first frequency and a second initial amplitude-frequency response corresponding to a second frequency in a first amplitude-frequency response characteristic curve; wherein a ratio of the second frequency to the first frequency is less than a preset scaling factor;

[0170] Initializing a first parameter for characterizing the order difference between a numerator and a denominator of a transfer function;

[0171] Based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response, repeatedly performing a first iterative calculation operation until an iteration termination condition is satisfied, stopping the first iterative calculation operation, and obtaining a first order difference;

[0172] The first iterative calculation operation includes:

[0173] Determine whether the ratio of the current second amplitude-frequency response to the current first amplitude-frequency response is less than N times the scaling factor, and determine whether the current first amplitude-frequency response is greater than a first preset value; wherein, when the first iterative calculation operation is performed for the first time, the current first amplitude-frequency response is the first initial amplitude-frequency response, and the current second amplitude-frequency response is the second initial amplitude-frequency response;

[0174] If the judgment results are all yes, then the first parameter is updated, the size of the current first amplitude-frequency response and the size of the current second amplitude-frequency response are adjusted, and the adjusted first amplitude-frequency response and second amplitude-frequency response are used as inputs for the next first iterative calculation operation;

[0175] On the contrary, it is confirmed that the iteration termination condition is met, the first iterative calculation operation is stopped, and the first parameter of this iterative calculation operation is used as the first order difference corresponding to the first amplitude-frequency response characteristic curve.

[0176] In a preferred embodiment, the calculating the second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies includes:

[0177] Obtaining a third initial amplitude-frequency response corresponding to a third frequency and a fourth initial amplitude-frequency response corresponding to a fourth frequency in the second amplitude-frequency response characteristic curve; wherein a ratio of the fourth frequency to the third frequency is less than a preset scaling factor;

[0178] Initializing a second parameter for characterizing the order difference between a numerator and a denominator of a transfer function;

[0179] Based on the second parameter, the third initial amplitude-frequency response and the fourth initial amplitude-frequency response, repeatedly performing a second iterative calculation operation until an iteration termination condition is satisfied, stopping the second iterative calculation operation, and obtaining a second order difference;

[0180] The second iterative calculation operation includes:

[0181] Determine whether the ratio of the current fourth amplitude-frequency response to the current third amplitude-frequency response is less than N times the scaling factor, and determine whether the current third amplitude-frequency response is greater than a second preset value; wherein, when the second iterative calculation operation is performed for the first time, the current third amplitude-frequency response is the third initial amplitude-frequency response, and the current fourth amplitude-frequency response is the fourth initial amplitude-frequency response;

[0182] If the judgment results are all yes, then the second parameter is updated, the size of the current third amplitude-frequency response and the size of the current fourth amplitude-frequency response are adjusted, and the adjusted third amplitude-frequency response and fourth amplitude-frequency response are used as inputs for the next second iterative calculation operation;

[0183] On the contrary, it is confirmed that the iteration termination condition is met, the second iterative calculation operation is stopped, and the second parameter of this iterative calculation operation is used as the second order difference corresponding to the second amplitude-frequency response characteristic curve.

[0184] In a preferred embodiment, determining the order of the transfer function of the power electronic device according to the first minimum point, the first order difference, the second minimum point, and the second order difference includes:

[0185] Count the number of all first minimum points to get the first total number;

[0186] Count the number of all second minimum points to get the second total number;

[0187] determining a first preselected order of a transfer function of the power electronic device based on the first total number and the first order difference;

[0188] determining a second preselected order of a transfer function of the power electronic device based on the second total number and the second order difference;

[0189] The first preselected order and the second preselected order are compared, and the preselected order with a larger value is used as the order of the transfer function of the power electronic device.

[0190] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for identifying broadband oscillation risk, characterized in that: include: Acquiring operating parameters of the power electronic device, a first amplitude-frequency response characteristic curve of the power electronic device within a preset frequency band, and a first transfer function of the power system; Determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve; According to the order of the transfer function and the operating parameters, fitting and obtaining a second transfer function of the power electronic device; Combining the first transfer function and the second transfer function, obtaining a third transfer function for characterizing the performance of a grid-connected system; wherein the grid-connected system is formed by the power electronic device and the power system being connected to the grid; The broadband oscillation risk of the grid-connected system is identified according to the third transfer function.

2. The broadband oscillation risk identification method according to claim 1, characterized in that: Determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve includes: Create a recognition window with a width of M, where M is greater than 0; According to the identification window, traverse the first amplitude-frequency response characteristic curve, and screen and obtain a first minimum value point of the first amplitude-frequency response characteristic curve; Calculating a first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies; Performing a reciprocal operation on all sampling points in the first amplitude-frequency response characteristic curve, and forming a second amplitude-frequency response characteristic curve based on all sampling points after the reciprocal operation is performed; According to the identification window, traverse the second amplitude-frequency response characteristic curve, and screen and obtain a second minimum value point of the second amplitude-frequency response characteristic curve; Calculating a second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies; The order of the transfer function of the power electronic device is determined according to the first minimum point, the first order difference, the second minimum point, and the second order difference.

3. The broadband oscillation risk identification method according to claim 2, characterized in that: The calculating the first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies includes: Obtaining a first initial amplitude-frequency response corresponding to a first frequency and a second initial amplitude-frequency response corresponding to a second frequency in a first amplitude-frequency response characteristic curve; wherein a ratio of the second frequency to the first frequency is less than a preset scaling factor; Initializing a first parameter for characterizing the order difference between a numerator and a denominator of a transfer function; Based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response, repeatedly performing a first iterative calculation operation until an iteration termination condition is satisfied, stopping the first iterative calculation operation, and obtaining a first order difference; The first iterative calculation operation includes: Determine whether the ratio of the current second amplitude-frequency response to the current first amplitude-frequency response is less than N times the scaling factor, and determine whether the current first amplitude-frequency response is greater than a first preset value; wherein, when the first iterative calculation operation is performed for the first time, the current first amplitude-frequency response is the first initial amplitude-frequency response, and the current second amplitude-frequency response is the second initial amplitude-frequency response; If the judgment results are all yes, then the first parameter is updated, the size of the current first amplitude-frequency response and the size of the current second amplitude-frequency response are adjusted, and the adjusted first amplitude-frequency response and second amplitude-frequency response are used as inputs for the next first iterative calculation operation; On the contrary, it is confirmed that the iteration termination condition is met, the first iterative calculation operation is stopped, and the first parameter of this iterative calculation operation is used as the first order difference corresponding to the first amplitude-frequency response characteristic curve.

4. The broadband oscillation risk identification method according to claim 2, characterized in that: The calculating and obtaining the second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies includes: Obtaining a third initial amplitude-frequency response corresponding to a third frequency and a fourth initial amplitude-frequency response corresponding to a fourth frequency in the second amplitude-frequency response characteristic curve; wherein a ratio of the fourth frequency to the third frequency is less than a preset scaling factor; Initializing a second parameter for characterizing the order difference between a numerator and a denominator of a transfer function; Based on the second parameter, the third initial amplitude-frequency response and the fourth initial amplitude-frequency response, repeatedly performing a second iterative calculation operation until an iteration termination condition is satisfied, stopping the second iterative calculation operation, and obtaining a second order difference; The second iterative calculation operation includes: Determine whether the ratio of the current fourth amplitude-frequency response to the current third amplitude-frequency response is less than N times the scaling factor, and determine whether the current third amplitude-frequency response is greater than a second preset value; wherein, when the second iterative calculation operation is performed for the first time, the current third amplitude-frequency response is the third initial amplitude-frequency response, and the current fourth amplitude-frequency response is the fourth initial amplitude-frequency response; If the judgment results are all yes, then the second parameter is updated, the size of the current third amplitude-frequency response and the size of the current fourth amplitude-frequency response are adjusted, and the adjusted third amplitude-frequency response and fourth amplitude-frequency response are used as inputs for the next second iterative calculation operation; On the contrary, it is confirmed that the iteration termination condition is met, the second iterative calculation operation is stopped, and the second parameter of this iterative calculation operation is used as the second order difference corresponding to the second amplitude-frequency response characteristic curve.

5. The broadband oscillation risk identification method according to claim 2, characterized in that: Determining the order of the transfer function of the power electronic device according to the first minimum point, the first order difference, the second minimum point, and the second order difference comprises: Count the number of all first minimum points to get the first total number; Count the number of all second minimum points to get the second total number; determining a first preselected order of a transfer function of the power electronic device based on the first total number and the first order difference; determining a second preselected order of a transfer function of the power electronic device based on the second total number and the second order difference; The first preselected order and the second preselected order are compared, and the preselected order with a larger value is used as the order of the transfer function of the power electronic device.

6. A broadband oscillation risk identification device, characterized in that: include: Data acquisition module, order determination module, power electronic equipment transfer function determination module, grid-connected system transfer function determination module and broadband oscillation risk identification module; The data acquisition module is used to acquire operating parameters of the power electronic device, a first amplitude-frequency response characteristic curve of the power electronic device within a preset frequency band, and a first transfer function of the power system; The order determination module is used to determine the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve; The power electronic device transfer function determination module is used to obtain a second transfer function of the power electronic device by fitting according to the order of the transfer function and the operating parameters; The grid-connected system transfer function determination module is used to combine the first transfer function and the second transfer function to obtain a third transfer function for characterizing the performance of the grid-connected system; wherein the grid-connected system is formed by the power electronic device and the power system being connected to the grid; The broadband oscillation risk identification module is used to identify the broadband oscillation risk of the grid-connected system according to the third transfer function.

7. The broadband oscillation risk identification device according to claim 6, characterized in that: Determining the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve includes: Create a recognition window with a width of M, where M is greater than 0; According to the identification window, traverse the first amplitude-frequency response characteristic curve, and screen and obtain a first minimum value point of the first amplitude-frequency response characteristic curve; Calculating a first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies; Performing a reciprocal operation on all sampling points in the first amplitude-frequency response characteristic curve, and forming a second amplitude-frequency response characteristic curve based on all sampling points after the reciprocal operation is performed; According to the identification window, traverse the second amplitude-frequency response characteristic curve, and screen and obtain a second minimum value point of the second amplitude-frequency response characteristic curve; Calculating a second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies; The order of the transfer function of the power electronic device is determined according to the first minimum point, the first order difference, the second minimum point, and the second order difference.

8. The broadband oscillation risk identification device according to claim 7, characterized in that: The calculating the first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies includes: Obtaining a first initial amplitude-frequency response corresponding to a first frequency and a second initial amplitude-frequency response corresponding to a second frequency in a first amplitude-frequency response characteristic curve; wherein a ratio of the second frequency to the first frequency is less than a preset scaling factor; Initializing a first parameter for characterizing the order difference between a numerator and a denominator of a transfer function; Based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response, repeatedly performing a first iterative calculation operation until an iteration termination condition is satisfied, stopping the first iterative calculation operation, and obtaining a first order difference; The first iterative calculation operation includes: Determine whether the ratio of the current second amplitude-frequency response to the current first amplitude-frequency response is less than N times the scaling factor, and determine whether the current first amplitude-frequency response is greater than a first preset value; wherein, when the first iterative calculation operation is performed for the first time, the current first amplitude-frequency response is the first initial amplitude-frequency response, and the current second amplitude-frequency response is the second initial amplitude-frequency response; If the judgment results are all yes, then the first parameter is updated, the size of the current first amplitude-frequency response and the size of the current second amplitude-frequency response are adjusted, and the adjusted first amplitude-frequency response and second amplitude-frequency response are used as inputs for the next first iterative calculation operation; On the contrary, it is confirmed that the iteration termination condition is met, the first iterative calculation operation is stopped, and the first parameter of this iterative calculation operation is used as the first order difference corresponding to the first amplitude-frequency response characteristic curve.

9. The broadband oscillation risk identification device according to claim 7, characterized in that: The calculating and obtaining the second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies includes: Obtaining a third initial amplitude-frequency response corresponding to a third frequency and a fourth initial amplitude-frequency response corresponding to a fourth frequency in the second amplitude-frequency response characteristic curve; wherein a ratio of the fourth frequency to the third frequency is less than a preset scaling factor; Initializing a second parameter for characterizing the order difference between a numerator and a denominator of a transfer function; Based on the second parameter, the third initial amplitude-frequency response and the fourth initial amplitude-frequency response, repeatedly performing a second iterative calculation operation until an iteration termination condition is satisfied, stopping the second iterative calculation operation, and obtaining a second order difference; The second iterative calculation operation includes: Determine whether the ratio of the current fourth amplitude-frequency response to the current third amplitude-frequency response is less than N times the scaling factor, and determine whether the current third amplitude-frequency response is greater than a second preset value; wherein, when the second iterative calculation operation is performed for the first time, the current third amplitude-frequency response is the third initial amplitude-frequency response, and the current fourth amplitude-frequency response is the fourth initial amplitude-frequency response; If the judgment results are all yes, then the second parameter is updated, the size of the current third amplitude-frequency response and the size of the current fourth amplitude-frequency response are adjusted, and the adjusted third amplitude-frequency response and fourth amplitude-frequency response are used as inputs for the next second iterative calculation operation; On the contrary, it is confirmed that the iteration termination condition is met, the second iterative calculation operation is stopped, and the second parameter of this iterative calculation operation is used as the second order difference corresponding to the second amplitude-frequency response characteristic curve.

10. The broadband oscillation risk identification device according to claim 7, characterized in that: Determining the order of the transfer function of the power electronic device according to the first minimum point, the first order difference, the second minimum point, and the second order difference comprises: Count the number of all first minimum points to get the first total number; Count the number of all second minimum points to get the second total number; determining a first preselected order of a transfer function of the power electronic device based on the first total number and the first order difference; determining a second preselected order of a transfer function of the power electronic device based on the second total number and the second order difference; The first preselected order and the second preselected order are compared, and the preselected order with a larger value is used as the order of the transfer function of the power electronic device.

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