Wind turbine generator grid-connected broadband oscillation power grid simulation method, system, equipment and medium

Abstract

The invention provides a wind turbine generator grid-connected broadband oscillation power grid simulation method, system and device and a medium, and belongs to the technical field of power system new energy grid connection, and the method comprises the steps: carrying out the frequency sweeping of a network side part of a physical wind turbine generator grid-connected system, and obtaining a full-band dq impedance characteristic curve; performing segmentation processing on the full-band dq impedance characteristic curve according to frequency; performing rational function fitting on the dq impedance characteristic curve of each frequency band by using a least square method, and enabling the network side part of the physical wind turbine generator grid-connected system to be equivalent to an RLC branch; constructing an impedance circuit, a main circuit and a signal processing module for each frequency band, and completing the construction of a broadband oscillation working condition simulation circuit; and the broadband impedance dynamic characteristics of the physical wind turbine generator grid-connected system are reproduced through the broadband oscillation working condition simulation circuit, so that the grid-connected stability of the physical wind turbine generator is detected. According to the invention, the simulation precision of the power grid simulator based on the power electronic converter topology is prevented from being limited by switching frequency and control precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy grid-connected power system, and specifically relates to a method, system, equipment and medium for simulating grid-connected broadband oscillation of wind turbines. Background Art

[0002] With the development of new energy represented by wind power, the power system is moving towards a high proportion of new energy and high proportion of electronic electrification. The multi-time scale, complex coupling interaction of diversified equipment and broadband oscillation characteristics of the current power system are becoming increasingly prominent, making the power system prone to broadband oscillations of several hertz or even thousands of hertz, which seriously threatens the safe and stable operation of the power system.

[0003] Before leaving the factory, wind turbines need to undergo grid-connected stability tests. The wind turbines are placed in a simulated grid environment to evaluate whether the grid-connected oscillation characteristics of the wind turbines meet expectations. Existing grid simulators usually use power electronic converters as the basic topology and simulate grid impedance characteristics by formulating specific control strategies. However, the control structure of this scheme is relatively complex, and is restricted by the switching frequency of the device and the accuracy and stability of the control system, resulting in a limited number of simulated impedance orders, and the simulated impedance is not accurate enough, and cannot accurately reflect the impedance characteristics of complex power systems. Therefore, most of these grid simulators are only suitable for simulating grid line impedances with lower orders, and are not suitable for complex grid-connected systems with high-order impedance characteristics such as wind power transmission systems via flexible DC transmission. In addition, there are grid simulators that use hardware-in-the-loop simulation to simulate the impedance of the grid-connected system, but because its grid-connected system model still has errors compared to the real grid-connected system, it cannot guarantee accurate simulation of the grid-connected system impedance in the full frequency band. Summary of the invention

[0004] In a first aspect, an embodiment of the present application provides a method for simulating a broadband oscillation grid for a wind turbine generator system, comprising the following steps: S1. Sweep the grid side of the physical wind turbine grid-connected system to obtain a full-band dq impedance characteristic curve of the grid side of the physical wind turbine grid-connected system; S2. Process the full-band dq impedance characteristic curve in segments according to the frequency, so as to ensure that the bandwidth of each frequency band is maximized when the order required by the rational function is determined by fitting, and the order required by the rational function is minimized when the bandwidth of each frequency band is determined by fitting; S3. The dq impedance characteristic curve of each frequency band is fitted with a rational function using the least square method, and the grid-side part of the physical wind turbine grid-connected system is equivalent to an RLC branch according to the fitted rational function expression; S4. For each frequency band, an impedance circuit characterized by an oscillating current source and an equivalent RLC branch connected in series is constructed, a main circuit characterized by an industrial frequency voltage source and an oscillating voltage source connected in series is constructed, and a signal processing module is constructed to virtually connect the main circuit and the impedance circuit, thereby completing the construction of a broadband oscillation working condition simulation circuit; S5. The broadband impedance dynamic characteristics of the physical wind turbine grid-connected system are reproduced through a broadband oscillation working condition simulation circuit, and the grid-connected stability of the physical wind turbine is detected.

[0005] Furthermore, the specific steps of step S1 are as follows: S11. Determine the number of experiments N, N ≥ 2; S12. Injecting harmonic disturbance current into the physical wind turbine grid-connected system in each experiment; S13. The frequency of the injected harmonic disturbance current is changed according to the set amplitude, and the full-band dq impedance characteristic curve output by the grid-side part of the physical wind turbine grid-connected system according to the transmission mode is obtained by measurement and calculation; the transmission mode includes flexible direct current transmission, industrial frequency alternating current transmission, diode uncontrolled rectification transmission and frequency division transmission transmission; S14. Compare the full-band dq impedance characteristic curves obtained by N experiments, and determine that the difference between the full-band dq impedance characteristic curves is less than the set amplitude; If yes, the test result is credible, and the process goes to step S2; If not, the test result is unreliable, and the process returns to step S12.

[0006] Furthermore, the specific steps of step S2 are as follows: S21. Preliminarily divide the full-band dq impedance characteristic curve into several frequency bands; S22. fitting each frequency band using a rational function to determine the order required for fitting; S23. Determine whether the order required for fitting each frequency band is less than the set order threshold; If yes, go to step S25; If not, proceed to step S24; S24. Divide the full-band dq impedance characteristic curve into frequency bands again in a manner of reducing the frequency bandwidth, and return to step S22; S25. Determine whether the frequency bands can be merged under the condition that the required order of fitting of each current frequency band is fixed; If yes, go to step S26; If not, determine the division of each frequency band and proceed to step S3; S26. Merge the frequency bands to obtain a final frequency band division.

[0007] Furthermore, the specific steps of step S3 are as follows: S31. Select one frequency band from each frequency band divided by the full-band dq impedance characteristic curve as a test frequency band; S32. Use the least square method to fit the rational function of the dq impedance characteristic curve segment corresponding to the test frequency band, ensure the fitting accuracy and reduce the order to obtain a 2×2 order dq impedance rational function matrix; S33. Represent each impedance rational function in the 2×2 order dq rational function matrix as a real pole part, a conjugate complex pole part, a constant term and a linear term part; S34. Perform RLC branch equivalent on the 2×2 order dq impedance rational function matrix to obtain real pole term branch, conjugate complex pole term branch, constant term and linear term branch, and combine them with series or parallel implementation forms to obtain four equivalent RLC branches under a certain implementation form.

[0008] Furthermore, the specific steps of step S34 are as follows: S341. Determine the implementation form; If it is a serial implementation, go to step S342; If it is a parallel implementation, go to step S344; S342. Connecting the real pole term branch, the conjugate complex pole term branch, the constant term and the linear term branch in series; S343. Use a resistor and a capacitor in parallel to represent a real pole term branch, use a resistor and an inductor in series and then connect them in parallel with a resistor and a capacitor to represent a conjugate complex pole term branch, and use a resistor and an inductor in series to represent a constant term and a linear term branch, and obtain four equivalent RLC branches in the series realization form; S344. Connecting the real pole term branch, the conjugate complex pole term branch, and the constant term and the first order term branch in parallel; S345. Use a resistor and an inductor in series to represent the real pole term branch, use a resistor and a capacitor in parallel and then in series with an inductor and a resistor to represent the conjugate complex pole term branch, use a resistor and a capacitor in parallel to represent the constant term and the linear term branch, and obtain four equivalent RLC branches in parallel implementation form.

[0009] Furthermore, the specific steps of step S4 are as follows: S41. Connecting a controlled oscillating current source in series to each of the four equivalent RLC branches to obtain four sub-circuits as impedance circuits; S42. A power frequency voltage source and a controlled oscillation voltage source are connected in series to form a main circuit, an external port is reserved for connecting the physical wind turbine to be measured, and the voltage value of the power frequency voltage source is set to the grid-side three-phase AC voltage of the physical wind turbine grid-connected system under stable operating conditions; S43. Constructing a signal processing module including a voltage signal processing unit and a current signal processing unit; S44. The current control signal collected from the main circuit is converted into an oscillating current signal by the current signal processing unit to control the controlled oscillating current source of each sub-circuit in the impedance circuit to output dq-axis oscillating current; S45. The dq-axis oscillation voltage generated by each sub-circuit according to the dq-axis oscillation current is converted into an oscillation voltage signal through the voltage signal processing unit and fed back to the main circuit to control the controlled oscillation voltage source to output a three-phase oscillation voltage, and loaded to the AC side port of the physical wind turbine to generate an oscillation current, thereby completing the construction of a wide-band oscillation working condition simulation circuit.

[0010] Furthermore, the specific steps of step S5 are as follows: S51. Based on the establishment of a broadband oscillation condition simulation circuit to reproduce the oscillation condition, the control parameters of the physical wind turbine are changed; S52. Identify whether the oscillation characteristics of the wind turbine are consistent with the expected characteristics; If yes, go to step S53; If not, proceed to step S56; S53. Determine whether the test of each frequency band is completed; If yes, go to step S55; If not, proceed to step S54; S54. Select one frequency band from each frequency band divided by the full-band dq impedance characteristic curve as a test frequency band, and return to step S32; S55. Determine that the physical wind turbine generator system meets the requirements, the test passes, and the process ends; S56. Determine that the physical wind turbine generator set test has failed.

[0011] In a second aspect, the present application also provides a wind turbine grid-connected broadband oscillation power grid simulation system, comprising: A full-band impedance characteristic curve acquisition unit is used to perform a frequency sweep on the grid-side part of the physical wind turbine generator system to acquire a full-band dq impedance characteristic curve of the grid-side part of the physical wind turbine generator system; The impedance characteristic curve segmentation unit is used to segment the full-band dq impedance characteristic curve according to the frequency, so as to ensure that the bandwidth of each frequency band is maximized when the order required by the rational function is determined for fitting, and the order required by the rational function is minimized when the bandwidth of each frequency band is determined; The RLC branch equivalent unit is used to fit the dq impedance characteristic curve of each frequency band using the least square method to perform rational function fitting, and the grid-side part of the physical wind turbine grid-connected system is equivalent to the RLC branch according to the fitted rational function expression; The analog circuit building unit is used to build an impedance circuit represented by an oscillating current source and an equivalent RLC branch in series for each frequency band, build a main circuit represented by an industrial frequency voltage source and an oscillating voltage source in series, and build a signal processing module that virtually connects the main circuit and the impedance circuit, so as to complete the construction of a wide-band oscillation working condition simulation circuit; The oscillation condition reproduction unit is used to reproduce the broadband impedance dynamic characteristics of the physical wind turbine grid-connected system through a broadband oscillation condition simulation circuit, and to detect the grid-connected stability of the physical wind turbine.

[0012] In a third aspect, an embodiment of the present application further provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the method for simulating a wide-band oscillation grid connected to the grid for a wind turbine as described in the first aspect are implemented.

[0013] In a fourth aspect, an embodiment of the present application further provides a storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps of the method for simulating a wide-frequency oscillation power grid for connecting a wind turbine to the grid as described in the first aspect are implemented.

[0014] It can be seen from the above technical solutions that the present invention has the following advantages: In the wind turbine grid-connected broadband oscillation grid simulation method, system, equipment and medium provided by the present application, the impedance of the complex grid-connected system is equivalent to the RLC branch, avoiding the problem that the impedance order and accuracy simulated by the grid simulator based on the power electronic converter topology are limited by the switching frequency and control accuracy of the device; while improving the simulation accuracy of the grid-connected system impedance, there is no need for complex controller debugging, and it can simulate the impedance of complex grid-connected systems such as flexible DC transmission systems that are not suitable for power electronic converter type grid simulators, providing a good test environment for wind turbine grid-connected stability testing and broadening the test scenarios. The present application obtains the full-band real impedance characteristics from the actual physical grid-connected system, avoiding the problem that the accuracy of the simulated impedance characteristics is limited due to the error between the derived grid-connected model and the actual system of the grid simulator based on hardware-in-the-loop simulation. The simulated impedance characteristics are closer to the real grid-connected system impedance characteristics, and the simulation range can cover the entire frequency band, which is more suitable for the simulation of wind turbine grid-connected broadband oscillation conditions, and the grid stability test results obtained by the present invention are also more convincing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0016] Figure 1 It is a flow chart of Embodiment 1 of the method for simulating a broadband oscillation power grid for connecting a wind turbine to the grid according to the present invention.

[0017] Figure 2 It is a schematic diagram of the broadband oscillation grid simulation system for wind turbines connected to the grid according to the present invention.

[0018] Figure 3 It is the RLC branch topology diagram of the series implementation form of the present invention.

[0019] Figure 4 This is a topological diagram of the RLC branches in the parallel implementation form of the present invention.

[0020] Figure 5 This is a circuit structure diagram for simulating the wide-frequency oscillation working condition of the present invention.

[0021] Figure 6 This is a structural diagram of the current signal processing unit of the present invention.

[0022] Figure 7 It is a structural diagram of the voltage signal processing unit of the present invention. DETAILED DESCRIPTION

[0023] In the specific steps of the method for simulating a broadband oscillating power grid connected to the wind turbine generator system, various embodiments of the present disclosure will be described in detail below. The present disclosure may have various embodiments, and adjustments and changes may be made therein. However, it should be understood that there is no intention to limit the various embodiments of the present disclosure to the specific embodiments disclosed herein, but the present disclosure should be understood to cover all adjustments, equivalents and / or alternatives that fall within the spirit and scope of the various embodiments of the present disclosure.

[0024] For example, with the rapid development of new energy sources such as wind power, the power system is gradually transforming towards a high proportion of new energy and a high proportion of electronic electrification. During this transformation process, the power system presents characteristics such as multiple time scales, complex coupling interactions of diversified equipment, and broadband oscillations, which exacerbate the stability challenges of the power system, especially the broadband oscillation problem, whose frequency range may cover several hertz to several thousand hertz, posing a serious threat to the safe and stable operation of the power system.

[0025] As an important part of renewable energy power generation, wind turbines need to undergo grid-connected stability tests before leaving the factory to evaluate whether their grid-connected oscillation characteristics meet expectations. Existing power grid simulators usually use power electronic converters as the basic topology and simulate grid impedance characteristics through specific control strategies. However, this solution has many limitations, such as complex control structure, constraints on device switching frequency and control system accuracy and stability, resulting in limited simulated impedance order and insufficient accuracy. Therefore, this type of power grid simulator is mainly suitable for simulating low-order grid line impedance. For complex grid-connected systems with high-order impedance characteristics, such as wind power transmission systems via flexible direct current transmission, its applicability is limited. In addition, there are power grid simulators that use hardware-in-the-loop simulation to simulate grid-connected system impedance, but due to the difference between the model accuracy and the real system, it cannot guarantee comprehensive and accurate simulation of grid-connected system impedance. This limitation further limits the application of traditional power grid simulators in stability testing of complex grid-connected systems.

[0026] In view of the above problems, this embodiment provides a method for simulating a wide-band oscillation grid for grid-connected wind turbines, which avoids the problem that the simulation accuracy of a grid simulator based on power electronic converter topology is limited by switching frequency and control accuracy, and the simulation accuracy of a grid simulator based on hardware-in-the-loop simulation is limited by the error between the theoretical model and the actual system. It can detect the grid-connected stability of new energy units in a new energy grid-connected system.

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] See also Figure 1 The figure is a flow chart of a method for simulating a broadband oscillation power grid for connecting a wind turbine to the grid in a specific embodiment. The method comprises the following steps: S1. Sweep the grid side of the physical wind turbine grid-connected system to obtain a full-band dq impedance characteristic curve of the grid side of the physical wind turbine grid-connected system; It should be noted that the frequency sweep test can fully obtain the impedance characteristics of the grid-side part of the wind turbine grid-connected system within the full frequency range, providing data support for subsequent impedance characteristic analysis and simulation; S2. Process the full-band dq impedance characteristic curve in segments according to the frequency, so as to ensure that the bandwidth of each frequency band is maximized when the order required by the rational function is determined by fitting, and the order required by the rational function is minimized when the bandwidth of each frequency band is determined by fitting; It should be noted that segmented processing can simplify the description of impedance characteristics. By optimizing the frequency band division, it ensures that the impedance characteristics can be accurately fitted by a rational function of a lower order in each frequency band, thus reducing the complexity and amount of calculation of the simulation. S3. The dq impedance characteristic curve of each frequency band is fitted with a rational function using the least square method, and the grid-side part of the physical wind turbine grid-connected system is equivalent to an RLC branch according to the fitted rational function expression; It should be noted that by fitting the rational function, the complex impedance characteristics are converted into a simple RLC branch equivalent circuit, which is convenient for the design and implementation of the subsequent simulation circuit; S4. For each frequency band, an impedance circuit characterized by an oscillating current source and an equivalent RLC branch connected in series is constructed, a main circuit characterized by an industrial frequency voltage source and an oscillating voltage source connected in series is constructed, and a signal processing module is constructed to virtually connect the main circuit and the impedance circuit, thereby completing the construction of a broadband oscillation working condition simulation circuit; It should be noted that by constructing a simulation circuit, the broadband oscillation condition of the wind turbine grid-connected system can be reproduced, providing a realistic test environment for the wind turbine stability test; S5. Reproduce the broadband impedance dynamic characteristics of the physical wind turbine grid-connected system through a broadband oscillation condition simulation circuit, and detect the grid-connected stability of the physical wind turbine; It should be noted that by testing the analog circuit, it is possible to accurately evaluate whether the oscillation characteristics of the wind turbine under wide-frequency oscillation conditions are consistent with the expected characteristics, thereby ensuring its safety and reliability in grid-connected operation.

[0029] This embodiment simulates wide-band oscillation conditions by converting the impedance of a complex grid-connected system into a low-order RLC circuit within the accuracy range, and is used in the grid-connected stability test of new energy units such as wind turbines. This avoids the problem that the impedance order and accuracy of the existing oscillation condition simulation method are limited by the switching frequency and control accuracy of the device, and by the error between the theoretical model and the actual system. This embodiment is more suitable for impedance characteristic simulation of complex grid-connected systems such as wind turbines through flexible direct current transmission systems, and has stronger feasibility and wider applicability.

[0030] Further, as a refinement and extension of the specific implementation of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, another method for simulating a broadband oscillation grid connected to a wind turbine is provided, and the method includes the following steps: S1. Sweep the grid side of the physical wind turbine grid-connected system to obtain the full-band dq impedance characteristic curve of the grid side of the physical wind turbine grid-connected system; the specific steps of step S1 are as follows: S11. Determine the number of experiments N, N ≥ 2; S12. Injecting harmonic disturbance current into the physical wind turbine grid-connected system in each experiment; S13. The frequency of the injected harmonic disturbance current is changed according to the set amplitude, and the full-band dq impedance characteristic curve output by the grid-side part of the physical wind turbine grid-connected system according to the transmission mode is obtained by measurement and calculation; the transmission mode includes flexible direct current transmission, industrial frequency alternating current transmission, diode uncontrolled rectification transmission and frequency division transmission transmission; It should be noted that the present application is applicable to the grid connection stability test of new energy units in the new energy grid connection system, wherein the system transmission mode, in addition to the flexible direct current transmission, can also be various transmission modes such as industrial frequency alternating current transmission, diode uncontrolled rectification transmission and frequency division transmission; S14. Compare the full-band dq impedance characteristic curves obtained by N experiments, and determine that the difference between the full-band dq impedance characteristic curves is less than the set amplitude; If yes, the test result is credible, and the process goes to step S2; If not, the test result is unreliable, and the process returns to step S12; It should be noted that after determining the number of experiments, the frequency points are selected, and two harmonic disturbances are injected into each frequency point in each experiment, and the impedance of each frequency point is calculated. Through multiple experiments, the differences in experimental results can be compared, so as to evaluate the experimental error and uncertainty; if the results of multiple experiments are similar or consistent, then it can be considered that the measurement results have a high degree of credibility; although increasing the number of injections may provide more data points, it will also increase the complexity and cost of the experiment accordingly; therefore, by reasonably designing the experimental plan, the number and cost of experiments can be minimized while ensuring the accuracy of the measurement results; S2. The full-band dq impedance characteristic curve is processed in segments according to the frequency, so as to ensure that the bandwidth of each frequency band is the largest when the order required for fitting is determined by the rational function, and the order required for fitting is the smallest when the bandwidth of each frequency band is determined; the specific steps of step S2 are as follows: S21. Preliminarily divide the full-band dq impedance characteristic curve into several frequency bands; S22. fitting each frequency band using a rational function to determine the order required for fitting; S23. Determine whether the order required for fitting each frequency band is less than the set order threshold; If yes, go to step S25; If not, proceed to step S24; S24. Divide the full-band dq impedance characteristic curve into frequency bands again in a manner of reducing the frequency bandwidth, and return to step S22; S25. Determine whether the frequency bands can be merged under the condition that the required order of fitting of each current frequency band is fixed; If yes, go to step S26; If not, determine the division of each frequency band and proceed to step S3; S26. merging the frequency bands to obtain a final frequency band division; It should be noted that the full-band dq impedance characteristic curve is divided into frequency segments according to the complexity of the impedance curve amplitude and phase change, with the goal of making the order of rational function fitting as low as possible while the bandwidth of each frequency band is as large as possible; at this time, after processing, the full-band complex impedance characteristics of the original flexible direct current system are initially reduced to impedance characteristics under multiple frequency bands; S3. The dq impedance characteristic curve of each frequency band is fitted with a rational function using the least square method, and the grid-side part of the physical wind turbine grid-connected system is equivalent to an RLC branch according to the fitted rational function expression; the specific steps of step S3 are as follows: S31. Select one frequency band from each frequency band divided by the full-band dq impedance characteristic curve as a test frequency band; S32. Use the least squares method to perform rational function fitting on the dq impedance characteristic curve segment corresponding to the test frequency band, ensure the fitting accuracy and perform order reduction, and obtain the following 2×2 order dq impedance rational function matrix: (1) in, s is the frequency of the band; S33. Each impedance rational function in the 2×2 order dq rational function matrix is ​​represented as a real pole part, a conjugate complex pole part, a constant term and a first order term part as follows: (2) in, M is the number of real pole terms, N is the number of conjugate complex pole terms; S34. Perform RLC branch equivalence on the 2×2 order dq impedance rational function matrix to obtain real pole term branch, conjugate complex pole term branch, constant term and first order term branch, and combine the series or parallel implementation form to obtain four equivalent RLC branches under the determined implementation form; the specific steps of step S34 are as follows: S341. Determine the implementation form; If it is a serial implementation, go to step S342; If it is a parallel implementation, go to step S344; S342. Connect the real pole term branch, the conjugate complex pole term branch, the constant term and the first-order term branch in series, such as Figure 3 As shown; S343. Use a resistor and a capacitor in parallel to represent the real pole term branch, the component parameters are shown in the following formula (3), use a resistor and an inductor in series and then connect them in parallel with a resistor and a capacitor to represent the conjugate complex pole term branch, the component parameters are shown in the following formula (4), use a resistor and an inductor in series to represent the constant term and the linear term branch, the component parameters are shown in the following formula (5), and obtain the equivalent four RLC branches in the series realization form; (3) (4) (5) S344. Connect the real pole term branch, the conjugate complex pole term branch, the constant term and the first-order term branch in parallel, such as Figure 4 As shown; S345. Use a resistor and an inductor in series to represent the real pole term branch, and the component parameters are shown in the following formula (6). Use a resistor and a capacitor in series and then connect them in parallel with an inductor and a resistor to represent the conjugate complex pole term branch, and the component parameters are shown in the following formula (7). Use a resistor and a capacitor in parallel to represent the constant term and the linear term branch, and the component parameters are shown in the following formula (8). Four equivalent RLC branches in parallel realization form are obtained; (6) (7) (8) S4. For each frequency band, an impedance circuit is constructed by connecting an oscillating current source and an equivalent RLC branch in series, a main circuit is constructed by connecting an industrial frequency voltage source and an oscillating voltage source in series, and a signal processing module is constructed to virtually connect the main circuit and the impedance circuit. Figure 5 The construction of the broadband oscillation working condition simulation circuit shown in FIG. 4; the specific steps of step S4 are as follows: S41. Connecting a controlled oscillating current source in series to each of the four equivalent RLC branches to obtain four sub-circuits as impedance circuits; S42. A power frequency voltage source and a controlled oscillation voltage source are connected in series to form a main circuit, an external port is reserved for connecting the physical wind turbine to be measured, and the voltage value of the power frequency voltage source is set to the grid-side three-phase AC voltage of the physical wind turbine grid-connected system under stable operating conditions; It should be noted that stable operating conditions are ideal conditions, that is, the physical wind turbine grid-connected system can maintain the stability of parameters such as voltage, current, power, and frequency, and at the same time has good dynamic response capabilities and equipment operating status.

[0031] S43. Constructing a signal processing module including a voltage signal processing unit and a current signal processing unit; S44. The current control signal collected from the main circuit is converted into an oscillating current signal by the current signal processing unit to control the controlled oscillating current source of each sub-circuit in the impedance circuit to output dq-axis oscillating current; S45. The dq-axis oscillation voltage generated by each subcircuit according to the dq-axis oscillation current is converted into an oscillation voltage signal through the voltage signal processing unit and fed back to the main circuit to control the controlled oscillation voltage source to output a three-phase oscillation voltage, and loaded to the AC side port of the physical wind turbine to generate an oscillation current, thereby completing the formation of a wide-band oscillation working condition simulation circuit; It should be noted that the main circuit is a circuit externally connected to the wind turbine under test, which is composed of an industrial frequency voltage source and an oscillating voltage source connected in series; the industrial frequency voltage source is an ideal voltage source, and the voltage value is the three-phase AC voltage when the flexible DC system is in steady-state operation, representing the steady-state operating condition of the flexible DC system; the oscillating voltage source is a controlled voltage source, and its control signal is obtained by feedback from the impedance circuit, representing the oscillating voltage component when the system oscillates; since the impedance of the flexible DC system is equivalent to four RLC branches in the dq synchronous rotating coordinate system, it cannot be directly connected to the wind turbine in the abc three-phase stationary coordinate system and the industrial frequency voltage source, so the output dynamics of the flexible DC system are replaced by an oscillating voltage source and connected to the main circuit, forming a virtual connection between the impedance of the flexible DC system and the wind turbine and the industrial frequency voltage source; like Figure 5 As shown in the figure, the impedance circuit represents the impedance characteristics of the flexible DC system under a selected frequency band. It consists of four independent sub-circuits dd, dq, qd and qq, which represent the impedance Z dd , Z dq , Z qd and Z qq Each subcircuit consists of an oscillating current source and an RLC branch in series, where the oscillating current source is a controlled current source, and its control signal is acquired by the main circuit, representing the oscillating current component when the system oscillates; the voltage-current relationship in the impedance circuit follows the following formula (9); the input of the subcircuit dd is the d-axis oscillating current i rd , the output is the d-axis oscillating voltage component u rdd ; The input of subcircuit dq is the d-axis oscillating current i rd , the output is the q-axis oscillating voltage component u rdq ; The input of subcircuit qd is q-axis oscillating current i rq , the output is the d-axis oscillating voltage componentu rqd ; The input of subcircuit qq is the q-axis oscillating current i rq , the output is the q-axis oscillating voltage component u rqq ; (9) The signal processing module is responsible for connecting the main circuit and the impedance circuit. It consists of two parts: the voltage signal processing unit and the current signal processing unit. The purpose of the current signal processing is to convert the abc three-phase AC current collected in the main circuit into a dq axis oscillating current suitable for the oscillation circuit. The principle is as follows: Figure 6 As shown; the three-phase AC current abc is measured at the AC port of the wind turbine i abc , which is transformed into dq axis current after dq transformation i dq , where the phase angle of the dq transformation is the phase angle of the power frequency voltage source. Using the obtained dq axis current i dq Subtract the dq axis current when the system is running in steady state i dq0 , that is, the dq axis oscillating current is obtained i rdq If the system has no oscillation, the dq axis oscillation current is 0; The purpose of voltage signal processing is to convert the oscillation voltage collected in the oscillation circuit into an abc three-phase oscillation voltage suitable for the main circuit. The principle is as follows Figure 7 As shown; the voltages in the four sub-circuits in the oscillation circuit are measured respectively, and the obtained u rdd , u rdq , u rqd and u rqq ;Will u rdd and u rdq Add together to get the d-axis oscillation voltage u rd ;Will u rqd and u rqq Add together to get the q-axis oscillation voltage u rq ;right u rd and u rq Perform dq inverse transformation, and take the phase angle of the power frequency voltage source as the phase angle of the inverse transformation to obtain the abc three-phase oscillation voltage urabc ; S5. The broadband oscillation condition simulation circuit is used to reproduce the broadband impedance dynamic characteristics of the physical wind turbine grid-connected system, and the grid-connected stability of the physical wind turbine is detected; the specific steps of step S5 are as follows: S51. Based on the establishment of a broadband oscillation condition simulation circuit to reproduce the oscillation condition, the control parameters of the physical wind turbine are changed; S52. Identify whether the oscillation characteristics of the wind turbine are consistent with the expected characteristics; If yes, go to step S53; If not, proceed to step S56; S53. Determine whether the test of each frequency band is completed; If yes, go to step S55; If not, proceed to step S54; S54. Select one frequency band from each frequency band divided by the full-band dq impedance characteristic curve as a test frequency band, and return to step S32; S55. Determine that the physical wind turbine generator system meets the requirements, the test passes, and the process ends; S56. Determine that the physical wind turbine test fails; It should be noted that the working principle of the broadband oscillation condition simulation circuit is as follows: when the wind turbine control parameters are changed at a certain moment to make the system oscillate, the system voltage and current will show corresponding oscillation characteristics; in the main circuit, the abc three-phase current of the AC side port of the wind turbine is continuously measured. i abc , which is converted into an oscillating current signal by the current signal processing unit and input into the impedance circuit. The four controlled current sources in the impedance circuit output the corresponding dq axis oscillating current. i rdq ; The dq axis oscillating current flows through the RLC branch to generate a dq axis oscillating voltage u rdq , continuously obtain the oscillation voltage, convert it into an oscillation voltage signal through the voltage signal processing module and feed it back to the main circuit, control the oscillation voltage source to generate the corresponding abc three-phase oscillation voltage u rabc ; The three-phase oscillating voltage is loaded on the AC side port of the wind turbine, which will stimulate the corresponding oscillating current; by replacing the impedance circuits in different frequency bands in turn, the oscillation conditions of the wind turbine in the full frequency band can be obtained; through this interactive method, the wide-band oscillation condition simulation circuit can eventually simulate the wide-band oscillation condition of the grid-connected system.

[0032] If the oscillation characteristics of the wind turbine under test are found to be consistent with the expected oscillation characteristics after the wide-band oscillation working condition simulation circuit test, it means that the wind turbine meets the expected manufacturing goals and passes the test; if the oscillation characteristics of the wind turbine in some frequency bands do not match the expected oscillation characteristics, the wind turbine fails the test.

[0033] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0034] like Figure 2 As shown, the following is an embodiment of the wind turbine grid-connected broadband oscillation power grid simulation system provided by the embodiment of the present disclosure. The system and the wind turbine grid-connected broadband oscillation power grid simulation method of the above-mentioned embodiments belong to the same inventive concept. For details not described in detail in the embodiment of the wind turbine grid-connected broadband oscillation power grid simulation system, reference can be made to the embodiment of the above-mentioned wind turbine grid-connected broadband oscillation power grid simulation method.

[0035] The system includes: A full-band impedance characteristic curve acquisition unit is used to perform a frequency sweep on the grid-side part of the physical wind turbine generator system to acquire a full-band dq impedance characteristic curve of the grid-side part of the physical wind turbine generator system; The impedance characteristic curve segmentation unit is used to segment the full-band dq impedance characteristic curve according to the frequency, so as to ensure that the bandwidth of each frequency band is maximized when the order required by the rational function is determined for fitting, and the order required by the rational function is minimized when the bandwidth of each frequency band is determined; The RLC branch equivalent unit is used to fit the dq impedance characteristic curve of each frequency band using the least square method to perform rational function fitting, and the grid-side part of the physical wind turbine grid-connected system is equivalent to the RLC branch according to the fitted rational function expression; The analog circuit building unit is used to build an impedance circuit represented by an oscillating current source and an equivalent RLC branch in series for each frequency band, build a main circuit represented by an industrial frequency voltage source and an oscillating voltage source in series, and build a signal processing module that virtually connects the main circuit and the impedance circuit, so as to complete the construction of a wide-band oscillation working condition simulation circuit; The oscillation condition reproduction unit is used to reproduce the broadband impedance dynamic characteristics of the physical wind turbine grid-connected system through a broadband oscillation condition simulation circuit, and to detect the grid-connected stability of the physical wind turbine.

[0036] This embodiment can automatically complete the steps of acquiring the full-band impedance characteristic curve, segmenting, RLC branch equivalent, building an analog circuit, and reproducing the oscillation condition through the full-band impedance characteristic curve acquisition unit, the impedance characteristic curve segmentation unit, the RLC branch equivalent unit, the analog circuit assembly unit, and the oscillation condition reproduction unit, thereby improving the test efficiency and accuracy.

[0037] The wind turbine grid-connected broadband oscillation grid simulation method provided in the embodiment of the present application can be applied to electronic devices. Those skilled in the art will appreciate that the electronic device structure involved in the embodiment of the present invention does not constitute a limitation on the electronic device, and the electronic device may include more or fewer components than shown, or combine certain components, or arrange different components. In an embodiment of the present invention, the electronic device includes but is not limited to a laptop computer, a desktop computer, a workbench, a personal digital assistant, a server, a blade server, a mainframe computer, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the embodiments of the present application described and / or required herein.

[0038] The electronic device may include a processor, an external memory interface, an internal memory, a universal serial bus (USB) interface, a charging management module, a power management module, a battery, a wireless communication module, an audio module, a speaker, a microphone, a sensor module, buttons, a camera, a display, and a SIM card interface, etc.

[0039] It is to be understood that the structure illustrated in the embodiments of the present application does not constitute a specific limitation on the electronic device. In other embodiments of the present application, the electronic device may include more or fewer components than shown in the figure, or combine certain components, or split certain components, or arrange the components differently. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

[0040] The processor may include one or more processing units, for example, the processor may include a central processing unit (CPU), an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a memory, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural-network processing unit (NPU), etc. Among them, different processing units may be independent devices or integrated into one or more processors.

[0041] The processor can be the nerve center and command center of the electronic device. The controller can generate an operation control signal according to the instruction operation code and timing signal to complete the control of fetching and executing instructions.

[0042] A memory may also be provided in the processor for storing instructions and data. In some embodiments, the memory in the processor is a cache memory. The memory may store instructions or data that the processor has just used or is cyclically used. If the processor needs to use the instruction or data again, it may be directly called from the memory. This avoids repeated access, reduces the waiting time of the processor, and thus improves system efficiency.

[0043] The above-mentioned electronic device realizes the technical solution of the method for simulating the grid-connected broadband oscillation of the wind turbine set in the present application, which converts the complex grid-connected system impedance into the equivalent of a low-order RLC circuit within the accuracy allowed, and then simulates the broadband oscillation working condition, and is used in the grid-connected stability test of new energy units such as wind turbine sets, thereby achieving the beneficial effect of avoiding the problem that the simulation accuracy of the grid simulator based on the power electronic converter topology is limited by the switching frequency and control accuracy, and the simulation accuracy of the grid simulator based on hardware-in-the-loop simulation is limited by the error between the theoretical model and the real system.

[0044] The storage medium provided in the present application stores a program product capable of implementing a method for simulating a broadband oscillation power grid for connecting a wind turbine to the grid.

[0045] The method for simulating a broadband oscillation power grid connected to a wind turbine generator set includes: performing a frequency sweep on the grid-side part of a physical wind turbine generator set grid-connected system to obtain a full-band dq impedance characteristic curve of the grid-side part of the physical wind turbine generator set grid-connected system; segmenting the full-band dq impedance characteristic curve according to frequency to ensure that the bandwidth of each frequency band is maximized when the order required for fitting a rational function is determined, and the order required for fitting a rational function is minimized when the bandwidth of each frequency band is determined; fitting the dq impedance characteristic curve of each frequency band with a rational function using the least squares method, and obtaining the full-band dq impedance characteristic curve of the physical wind turbine generator set grid-connected system according to frequency ... The grid-side part of the physical wind turbine grid-connected system is equivalent to an RLC branch through a logical function expression; for each frequency band, an impedance circuit represented by an oscillating current source and an equivalent RLC branch in series is constructed, a main circuit represented by an industrial frequency voltage source and an oscillating voltage source in series is constructed, and a signal processing module that virtually connects the main circuit with the impedance circuit is constructed to complete the construction of a broadband oscillation operating condition simulation circuit; the broadband impedance dynamic characteristics of the physical wind turbine grid-connected system are reproduced through the broadband oscillation operating condition simulation circuit, and the grid-connected stability of the physical wind turbine is tested.

[0046] In some possible embodiments, the wind turbine grid-connected broadband oscillation grid simulation method disclosed herein can be implemented in the form of a program product, which includes a program code. When the program product is run on a terminal device, the program code is used to enable the terminal device to execute the steps described in the above "Exemplary Method" section of this specification according to various exemplary embodiments of the present disclosure.

[0047] The storage medium of the present disclosure can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium can be, for example, but not limited to, a system, device or device of electricity, magnetism, light, electromagnetic, infrared, or semiconductor, or any combination of the above. More specific examples (non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0048] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for simulating a broadband oscillation grid for a wind turbine generator system, characterized in that: The steps include: S1. Sweep the grid side of the physical wind turbine grid-connected system to obtain the full-band dq impedance characteristic curve of the grid side of the physical wind turbine grid-connected system; S2. Process the full-band dq impedance characteristic curve in segments according to the frequency, so as to ensure that the bandwidth of each frequency band is maximized when the order required by the rational function is determined by fitting, and the order required by the rational function is minimized when the bandwidth of each frequency band is determined by fitting; S3. The dq impedance characteristic curve of each frequency band is fitted with a rational function using the least square method, and the grid-side part of the physical wind turbine grid-connected system is equivalent to an RLC branch according to the fitted rational function expression; S4. For each frequency band, an impedance circuit characterized by an oscillating current source and an equivalent RLC branch connected in series is constructed, a main circuit characterized by an industrial frequency voltage source and an oscillating voltage source connected in series is constructed, and a signal processing module is constructed to virtually connect the main circuit and the impedance circuit, thereby completing the construction of a broadband oscillation working condition simulation circuit; S5. The broadband impedance dynamic characteristics of the physical wind turbine grid-connected system are reproduced through a broadband oscillation working condition simulation circuit, and the grid-connected stability of the physical wind turbine is detected.

2. The method for simulating a broadband oscillation grid for connecting a wind turbine to the grid according to claim 1, characterized in that: The specific steps of step S1 are as follows: S11. Determine the number of experiments N, N ≥ 2; S12. Injecting harmonic disturbance current into the physical wind turbine grid-connected system in each experiment; S13. The frequency of the injected harmonic disturbance current is changed according to the set amplitude, and the full-band dq impedance characteristic curve output by the grid-side part of the physical wind turbine grid-connected system according to the transmission mode is obtained by measurement and calculation; the transmission mode includes flexible direct current transmission, industrial frequency alternating current transmission, diode uncontrolled rectification transmission and frequency division transmission transmission; S14. Compare the full-band dq impedance characteristic curves obtained by N experiments, and determine that the difference between the full-band dq impedance characteristic curves is less than the set amplitude; If yes, the test result is credible, and the process goes to step S2; If not, the test result is unreliable, and the process returns to step S12.

3. The method for simulating a broadband oscillation grid for connecting a wind turbine to the grid according to claim 2, characterized in that: The specific steps of step S2 are as follows: S21. Preliminarily divide the full-band dq impedance characteristic curve into several frequency bands; S22. fitting each frequency band using a rational function to determine the order required for fitting; S23. Determine whether the order required for fitting each frequency band is less than the set order threshold; If yes, go to step S25; If not, proceed to step S24; S24. Divide the full-band dq impedance characteristic curve into frequency bands again in a manner of reducing the frequency bandwidth, and return to step S22; S25. Determine whether the frequency bands can be merged under the condition that the required order of fitting of each current frequency band is fixed; If yes, go to step S26; If not, determine the division of each frequency band and proceed to step S3; S26. Merge the frequency bands to obtain a final frequency band division.

4. The method for simulating a broadband oscillation grid for connecting a wind turbine to the grid according to claim 3, characterized in that: The specific steps of step S3 are as follows: S31. Select one frequency band from each frequency band divided by the full-band dq impedance characteristic curve as a test frequency band; S32. Use the least square method to fit the rational function of the dq impedance characteristic curve segment corresponding to the test frequency band, ensure the fitting accuracy and reduce the order to obtain a 2×2 order dq impedance rational function matrix; S33. Represent each impedance rational function in the 2×2 order dq rational function matrix as a real pole part, a conjugate complex pole part, a constant term and a linear term part; S34. Perform RLC branch equivalent on the 2×2 order dq impedance rational function matrix to obtain real pole term branch, conjugate complex pole term branch, constant term and linear term branch, and combine them with series or parallel implementation forms to obtain four equivalent RLC branches under a certain implementation form.

5. The method for simulating a broadband oscillation grid for connecting a wind turbine to the grid according to claim 4, characterized in that: The specific steps of step S34 are as follows: S341. Determine the implementation form; If it is a serial implementation, go to step S342; If it is a parallel implementation, go to step S344; S342. Connecting the real pole term branch, the conjugate complex pole term branch, the constant term and the linear term branch in series; S343. Use a resistor and a capacitor in parallel to represent a real pole term branch, use a resistor and an inductor in series and then connect them in parallel with a resistor and a capacitor to represent a conjugate complex pole term branch, and use a resistor and an inductor in series to represent a constant term and a linear term branch, and obtain four equivalent RLC branches in the series realization form; S344. Connecting the real pole term branch, the conjugate complex pole term branch, and the constant term and the first order term branch in parallel; S345. Use a resistor and an inductor in series to represent the real pole term branch, use a resistor and a capacitor in parallel and then in series with an inductor and a resistor to represent the conjugate complex pole term branch, use a resistor and a capacitor in parallel to represent the constant term and the linear term branch, and obtain four equivalent RLC branches in parallel implementation form.

6. The method for simulating a broadband oscillation grid for connecting a wind turbine to the grid according to claim 4, characterized in that: The specific steps of step S4 are as follows: S41. Connecting a controlled oscillating current source in series to each of the four equivalent RLC branches to obtain four sub-circuits as impedance circuits; S42. A power frequency voltage source and a controlled oscillation voltage source are connected in series to form a main circuit, an external port is reserved for connecting the physical wind turbine to be measured, and the voltage value of the power frequency voltage source is set to the grid-side three-phase AC voltage of the physical wind turbine grid-connected system under stable operating conditions; S43. Constructing a signal processing module including a voltage signal processing unit and a current signal processing unit; S44. The current control signal collected from the main circuit is converted into an oscillating current signal by the current signal processing unit to control the controlled oscillating current source of each sub-circuit in the impedance circuit to output dq-axis oscillating current; S45. The dq-axis oscillation voltage generated by each sub-circuit according to the dq-axis oscillation current is converted into an oscillation voltage signal through the voltage signal processing unit and fed back to the main circuit to control the controlled oscillation voltage source to output a three-phase oscillation voltage, and loaded to the AC side port of the physical wind turbine to generate an oscillation current, thereby completing the construction of a wide-band oscillation working condition simulation circuit.

7. The method for simulating a broadband oscillation grid for connecting a wind turbine to the grid according to claim 6, characterized in that: The specific steps of step S5 are as follows: S51. Based on the establishment of a broadband oscillation condition simulation circuit to reproduce the oscillation condition, the control parameters of the physical wind turbine are changed; S52. Identify whether the oscillation characteristics of the wind turbine are consistent with the expected characteristics; If yes, go to step S53; If not, proceed to step S56; S53. Determine whether the test of each frequency band is completed; If yes, go to step S55; If not, proceed to step S54; S54. Select one frequency band from each frequency band divided by the full-band dq impedance characteristic curve as a test frequency band, and return to step S32; S55. Determine that the physical wind turbine generator system meets the requirements, the test passes, and the process ends; S56. Determine that the physical wind turbine generator set test has failed.

8. A wind turbine grid-connected broadband oscillation power grid simulation system, characterized in that: include: A full-band impedance characteristic curve acquisition unit is used to perform a frequency sweep on the grid-side part of the physical wind turbine generator system to acquire a full-band dq impedance characteristic curve of the grid-side part of the physical wind turbine generator system; The impedance characteristic curve segmentation unit is used to segment the full-band dq impedance characteristic curve according to the frequency, so as to ensure that the bandwidth of each frequency band is maximized when the order required by the rational function is determined for fitting, and the order required by the rational function is minimized when the bandwidth of each frequency band is determined; The RLC branch equivalent unit is used to fit the dq impedance characteristic curve of each frequency band using the least square method to perform rational function fitting, and the grid-side part of the physical wind turbine grid-connected system is equivalent to the RLC branch according to the fitted rational function expression; The analog circuit building unit is used to build an impedance circuit represented by an oscillating current source and an equivalent RLC branch in series for each frequency band, build a main circuit represented by an industrial frequency voltage source and an oscillating voltage source in series, and build a signal processing module that virtually connects the main circuit and the impedance circuit, so as to complete the construction of a wide-band oscillation working condition simulation circuit; The oscillation condition reproduction unit is used to reproduce the broadband impedance dynamic characteristics of the physical wind turbine grid-connected system through a broadband oscillation condition simulation circuit, and to detect the grid-connected stability of the physical wind turbine.

9. An electronic device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for simulating a wide-frequency oscillation power grid for connecting a wind turbine to the grid as claimed in any one of claims 1 to 7 when executing the program.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for simulating a wide-frequency oscillation grid for connecting a wind turbine to the grid as claimed in any one of claims 1 to 7 are implemented.

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