A broadband oscillation risk identification method and device

Abstract

The application discloses a wide-frequency oscillation risk identification method and device. The method obtains the operation parameters of a power electronic device, the first amplitude-frequency response characteristic curve of the power electronic device in a preset frequency band range and the first transfer function of a power system, then determines the order of the transfer function of the power electronic device according to the first amplitude-frequency response characteristic curve, and then fits the second transfer function of the power electronic device according to the order of the transfer function and the operation parameters, so as to obtain the third transfer function for characterizing the performance of a grid-connected system by combining the first transfer function and the second transfer function, and finally identifies the wide-frequency oscillation risk of the grid-connected system according to the third transfer function. Through the implementation of the application, the transfer function identification efficiency can be improved, so as to improve the wide-frequency oscillation risk identification precision between the power electronic device and the power system.

Description

Technical Field

[0001] The present invention relates to the field of power system risk identification, and in particular to a method and device for identifying broadband oscillation risks. 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 extremely helpful in identifying the risk of broadband oscillations in power systems.

[0003] However, when determining the transfer function, choosing an order that is too low may fail to fully capture the system's dynamic characteristics; choosing an order that is too high increases the computational burden and may introduce noise and errors. Observing the system's step response or impulse response is a traditional method for determining the order, but this approach has limitations. For simple, low-order systems, the order can be roughly estimated by observing the shape and decay rate of the response curve. However, when the system order is higher, its time domain response becomes extremely complex, making accurate estimation of the system order extremely difficult. This results 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, so as to achieve the purpose of improving the accuracy of broadband oscillation risk identification between power electronic equipment and power system.

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

[0006] Obtaining 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] fitting a second transfer function of the power electronic device according to the order of the transfer function and the operating parameters;

[0009] 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;

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

[0011] Furthermore, 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 to screen and obtain a first minimum 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 an inverse 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 inverse operation is performed;

[0016] Traversing the second amplitude-frequency response characteristic curve according to the identification window, and screening to obtain a second minimum 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] Furthermore, the calculating of the first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies includes:

[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 the numerator and the denominator of the transfer function;

[0022] Repeating a first iterative calculation operation based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response 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] Determining whether a ratio of a current second amplitude-frequency response to a current first amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the first parameter, adjusting the size of the current first amplitude-frequency response and the current second amplitude-frequency response, and using the adjusted first amplitude-frequency response and second amplitude-frequency response as inputs for the next first iterative calculation operation;

[0026] On the contrary, if 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] Furthermore, the calculating of 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 the numerator and the denominator of the transfer function;

[0030] Repeating a second iterative calculation operation based on the second parameter, the third initial amplitude-frequency response, and the fourth initial amplitude-frequency response 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] determining whether a ratio of a current fourth amplitude-frequency response to a current third amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the second parameter, adjusting the size of the current third amplitude frequency response and the current fourth amplitude frequency response, and using the adjusted third amplitude frequency response and fourth amplitude frequency response as inputs for the next second iterative calculation operation;

[0034] On the contrary, if 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] Furthermore, 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;

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

[0040] The first preselected order and the second preselected order are compared, and the preselected order with the 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 configured 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 configured 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 configured 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 configured to identify the broadband oscillation risk of the grid-connected system according to the third transfer function.

[0047] Furthermore, 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 to screen and obtain a first minimum 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 an inverse 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 inverse operation is performed;

[0052] Traversing the second amplitude-frequency response characteristic curve according to the identification window, and screening to obtain a second minimum 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] Furthermore, the calculating of the first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies includes:

[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 the numerator and the denominator of the transfer function;

[0058] Repeating a first iterative calculation operation based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response 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] Determining whether a ratio of a current second amplitude-frequency response to a current first amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the first parameter, adjusting the size of the current first amplitude-frequency response and the current second amplitude-frequency response, and using the adjusted first amplitude-frequency response and second amplitude-frequency response as inputs for the next first iterative calculation operation;

[0062] On the contrary, if 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] Furthermore, the calculating of 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 the numerator and the denominator of the transfer function;

[0066] Repeating a second iterative calculation operation based on the second parameter, the third initial amplitude-frequency response, and the fourth initial amplitude-frequency response 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] determining whether a ratio of a current fourth amplitude-frequency response to a current third amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the second parameter, adjusting the size of the current third amplitude frequency response and the current fourth amplitude frequency response, and using the adjusted third amplitude frequency response and fourth amplitude frequency response as inputs for the next second iterative calculation operation;

[0070] On the contrary, if 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] Furthermore, 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;

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

[0076] The first preselected order and the second preselected order are compared, and the preselected order with the 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, apparatus, device, and medium for identifying broadband oscillation risks. The method determines the order of a transfer function of a power electronic device based on a first amplitude-frequency response characteristic curve of the power electronic device within a preset frequency band. A second transfer function of the power electronic device is then fitted based on the order of the transfer function and operating parameters. The first and second transfer functions are combined to obtain a third transfer function corresponding to a grid-connected system. The broadband oscillation risk of the grid-connected system is then identified based on 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. In the subsequent fitting of the transfer function, the efficiency of transfer function identification can be effectively improved, so as to achieve the purpose of improving the accuracy of identifying broadband oscillation risks 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 following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0081] Figure 1 This is a flowchart of a method for identifying broadband oscillation risks provided by an embodiment of the present application;

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

[0083] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions in this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only 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 making any creative efforts 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 those skilled in the art 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" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0085] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0086] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, 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 this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects 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 expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0090] See also Figure 1 , is a flow chart of a method for identifying broadband oscillation risk provided by one 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 the 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 to screen and obtain a first minimum 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 an inverse 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 inverse operation is performed;

[0098] Traversing the second amplitude-frequency response characteristic curve according to the identification window, and screening to obtain a second minimum 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 within 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 this 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 find the corresponding first minimum point, the recognition window moves to the right by 1 frequency point; if the current recognition window finds the corresponding first minimum point, the recognition window 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, calculating the first order difference based on 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 the numerator and the denominator of the transfer function;

[0108] Repeating a first iterative calculation operation based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response 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] Determining whether a ratio of a current second amplitude-frequency response to a current first amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the first parameter, adjusting the size of the current first amplitude-frequency response and the current second amplitude-frequency response, and using the adjusted first amplitude-frequency response and second amplitude-frequency response 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, the first initial amplitude-frequency response A1 corresponding to the first frequency fs1 and the second initial amplitude-frequency response A2 corresponding to the 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 initialize the first parameter ΔM1, setting 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 adjusted 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 an inverse 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 taking the inverse;

[0121] Similarly, the second amplitude-frequency response characteristic curve L2 is traversed through the identification window, and 2*ΔT+1 frequency points in the identification window are searched. 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 this 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 identification window does not find the corresponding second minimum point, the identification window moves to the right by 1 frequency point; if the current identification window finds the corresponding second minimum point, the identification window moves to the right by ΔT frequency points;

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

[0124] In a preferred embodiment, 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 the numerator and the denominator of the transfer function;

[0127] Repeating a second iterative calculation operation based on the second parameter, the third initial amplitude-frequency response, and the fourth initial amplitude-frequency response 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] determining whether a ratio of a current fourth amplitude-frequency response to a current third amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the second parameter, adjusting the size of the current third amplitude frequency response and the current fourth amplitude frequency response, and using the adjusted third amplitude frequency response and fourth amplitude frequency response 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 initialize the second parameter ΔM2, setting 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] Otherwise, 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;

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

[0144] comparing the first preselected order and the second preselected order, and using the preselected order with the 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 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 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 a broadband oscillation risk of the grid-connected system according to the third transfer function;

[0153] Specifically, the stability of the system can be determined by observing the location of the poles of the third transfer function G3. If the poles are located in the left half of the complex plane, the system is stable; if the poles are located in the right half of the complex plane or on the imaginary axis, the system may be unstable or at risk of oscillation.

[0154] See 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 configured 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 configured 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 configured 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 configured 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 to screen and obtain a first minimum 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 an inverse 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 inverse operation is performed;

[0165] Traversing the second amplitude-frequency response characteristic curve according to the identification window, and screening to obtain a second minimum 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, calculating the first order difference based on 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 the numerator and the denominator of the transfer function;

[0171] Repeating a first iterative calculation operation based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response 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] Determining whether a ratio of a current second amplitude-frequency response to a current first amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the first parameter, adjusting the size of the current first amplitude-frequency response and the current second amplitude-frequency response, and using the adjusted first amplitude-frequency response and second amplitude-frequency response as inputs for the next first iterative calculation operation;

[0175] On the contrary, if 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, 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 the numerator and the denominator of the transfer function;

[0179] Repeating a second iterative calculation operation based on the second parameter, the third initial amplitude-frequency response, and the fourth initial amplitude-frequency response 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] determining whether a ratio of a current fourth amplitude-frequency response to a current third amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the second parameter, adjusting the size of the current third amplitude frequency response and the current fourth amplitude frequency response, and using the adjusted third amplitude frequency response and fourth amplitude frequency response as inputs for the next second iterative calculation operation;

[0183] On the contrary, if 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;

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

[0189] The first preselected order and the second preselected order are compared, and the preselected order with the 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 for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles 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: Obtaining 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; 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 to screen and obtain a first minimum 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 an inverse 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 inverse operation; Traversing the second amplitude-frequency response characteristic curve according to the identification window, and screening to obtain a second minimum 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; 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; fitting a second transfer function of the power electronic device according to the order of the transfer function and the operating parameters; 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; 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, wherein: 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 the numerator and the denominator of the transfer function; Repeating a first iterative calculation operation based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response 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: Determining whether a ratio of a current second amplitude-frequency response to a current first amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the first parameter, adjusting the size of the current first amplitude-frequency response and the current second amplitude-frequency response, and using the adjusted first amplitude-frequency response and second amplitude-frequency response as inputs for the next first iterative calculation operation; On the contrary, if 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.

3. The broadband oscillation risk identification method according to claim 1, wherein: The calculating 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 the numerator and the denominator of the transfer function; Repeating a second iterative calculation operation based on the second parameter, the third initial amplitude-frequency response, and the fourth initial amplitude-frequency response 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: determining whether a ratio of a current fourth amplitude-frequency response to a current third amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the second parameter, adjusting the size of the current third amplitude frequency response and the current fourth amplitude frequency response, and using the adjusted third amplitude frequency response and fourth amplitude frequency response as inputs for the next second iterative calculation operation; On the contrary, if 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.

4. The broadband oscillation risk identification method according to claim 1, wherein: 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: 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; determining a first preselected order of a transfer function of the power electronic device based on the first total and the first order difference; determining a second preselected order of a transfer function of the power electronic device based on the second total and the second order difference; The first preselected order and the second preselected order are compared, and the preselected order with the larger value is used as the order of the transfer function of the power electronic device.

5. 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 configured to create an identification window with a window width of M, wherein M is greater than 0; traverse the first amplitude-frequency response characteristic curve according to the identification window, and screen out a first minimum point of the first amplitude-frequency response characteristic curve; calculate a first order difference according to the amplitude-frequency response of the first amplitude-frequency response characteristic curve at different frequencies; perform an inverse operation on all sampling points in the first amplitude-frequency response characteristic curve, and form a second amplitude-frequency response characteristic curve based on all the sampling points after the inverse operation; traverse the second amplitude-frequency response characteristic curve according to the identification window, and screen out a second minimum point of the second amplitude-frequency response characteristic curve; calculate a second order difference according to the amplitude-frequency response of the second amplitude-frequency response characteristic curve at different frequencies; and determine 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; The power electronic device transfer function determination module is configured 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 configured 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 configured to identify the broadband oscillation risk of the grid-connected system according to the third transfer function.

6. The broadband oscillation risk identification device according to claim 5, wherein: 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 the numerator and the denominator of the transfer function; Repeating a first iterative calculation operation based on the first parameter, the first initial amplitude-frequency response, and the second initial amplitude-frequency response 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: Determining whether a ratio of a current second amplitude-frequency response to a current first amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the first parameter, adjusting the size of the current first amplitude-frequency response and the current second amplitude-frequency response, and using the adjusted first amplitude-frequency response and second amplitude-frequency response as inputs for the next first iterative calculation operation; On the contrary, if 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.

7. The broadband oscillation risk identification device according to claim 5, wherein: The calculating 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 the numerator and the denominator of the transfer function; Repeating a second iterative calculation operation based on the second parameter, the third initial amplitude-frequency response, and the fourth initial amplitude-frequency response 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: determining whether a ratio of a current fourth amplitude-frequency response to a current third amplitude-frequency response is less than N times the scaling factor, and determining 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 updating the second parameter, adjusting the size of the current third amplitude frequency response and the current fourth amplitude frequency response, and using the adjusted third amplitude frequency response and fourth amplitude frequency response as inputs for the next second iterative calculation operation; On the contrary, if 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.

8. The broadband oscillation risk identification device according to claim 5, wherein: 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: 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; determining a first preselected order of a transfer function of the power electronic device based on the first total and the first order difference; determining a second preselected order of a transfer function of the power electronic device based on the second total and the second order difference; The first preselected order and the second preselected order are compared, and the preselected order with the larger value is used as the order of the transfer function of the power electronic device.

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