Harmonic analysis method, system and equipment for flexible direct current converter and medium

Abstract

The invention discloses a harmonic analysis method, system and device for a flexible direct current converter and a medium, and relates to the technical field of flexible direct current transmission, and the method comprises the steps: obtaining key electrical parameters of a to-be-tested flexible direct current converter; constructing a high-frequency equivalent circuit corresponding to each target device according to the key electrical parameters; calculating a harmonic voltage component of a single bridge arm of a converter valve in the to-be-tested flexible DC converter according to the key electrical parameters so as to generate a harmonic voltage source; integrating the high-frequency equivalent circuit and the harmonic voltage source into simulation software for transient simulation; and determining harmonic voltage distribution and harmonic current distribution of the to-be-tested flexible direct current converter according to the simulation result, thereby effectively avoiding the equipment operation risk and reducing the fault rate of the flexible power transmission equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible direct current transmission, in particular to a harmonic analysis method, system, device and medium for a flexible direct current converter. BACKGROUND

[0002] The flexible direct current transmission system has four-quadrant operation capability and can independently operate without relying on the power grid, and is particularly suitable for large-scale new energy weak alternating current power grid to power load centers and deep sea wind power transmission scenarios, and is one of the main technical means for large-scale new energy transmission in future desert and barren areas and deep sea wind power transmission.

[0003] Compared with the conventional direct current converter, the flexible direct current converter does not generate a large amount of low-frequency harmonic, and does not need AC / DC filter. However, recent research has found that the flexible direct current system with modular multilevel converter as the main topological structure still generates harmonic with certain characteristic frequency and high frequency, which is an integer multiple of the pole control and valve control frequency, and long-time harmonic voltage and harmonic current may cause damage to key equipment such as wall bushing and converter transformer. Therefore, it is very important to quantitatively analyze the harmonic voltage and current parameters generated by the flexible direct current converter, to provide effective data support for the manufacture and protection of the equipment, and to avoid equipment damage.

[0004] However, the traditional on-site measurement method such as using a probe device is often disturbed by external electromagnetic environment and is time-consuming, with low data accuracy, large error and low efficiency.

[0005] Therefore, how to effectively determine the high-frequency harmonic parameters of the flexible direct current converter and ensure the data accuracy has become a technical problem to be solved by those skilled in the art. SUMMARY

[0006] The present application provides a harmonic analysis method, system, device and medium for a flexible direct current converter, which solves how to realize simulation analysis of harmonic characteristics through the equivalent model of each power transmission equipment and improves the accuracy of the output results.

[0007] To solve the above technical problems, the present application provides a harmonic analysis method for a flexible direct current converter, comprising:

[0008] Obtaining the key electrical parameters of the to-be-tested flexible direct current converter;

[0009] According to the key electrical parameters, constructing a high-frequency equivalent circuit corresponding to each target device in the to-be-tested flexible direct current converter;

[0010] According to the key electrical parameters, calculating the harmonic voltage component of a single bridge arm of the converter valve in the to-be-tested flexible direct current converter to generate a harmonic voltage source;

[0011] Integrate the high-frequency equivalent circuit and the harmonic voltage source into simulation software for transient simulation to obtain a transient simulation result;

[0012] Determine a harmonic voltage distribution and a harmonic current distribution of the to-be-tested flexible DC converter according to the transient simulation result.

[0013] Further, the obtaining of the key electrical parameters of the to-be-tested flexible DC converter comprises:

[0014] The key electrical parameters corresponding to each of the target devices in the to-be-tested flexible DC converter are measured by using an impedance analyzer; the target devices comprise converter valve devices, transformer devices and bushing devices.

[0015] Further, the calculating of the harmonic voltage component of a single bridge arm of a converter valve in the to-be-tested flexible DC converter according to the key electrical parameters to generate a harmonic voltage source comprises:

[0016] The harmonic voltage component of a single bridge arm at each frequency is calculated according to a valve control frequency to power frequency ratio, a bridge arm submodule number, a converter valve modulation ratio and a single submodule capacitor voltage average in the key electrical parameters;

[0017] The harmonic voltage source is constructed according to the harmonic voltage component.

[0018] Further, the harmonic voltage component comprises the following formula:

[0019]

[0020] In the formula, M is a modulation ratio, N2 is a bridge arm submodule number, U c is a submodule capacitor voltage average, q is a valve control frequency to power frequency ratio, k is a valve control frequency multiple, is an amplitude of the component, ω s is an angle speed corresponding to a DC converter pole control and valve control modulation frequency, and ω0 is an angle speed corresponding to a power frequency modulation wave.

[0021] Further, the integrating of the high-frequency equivalent circuit and the harmonic voltage source into simulation software for transient simulation comprises:

[0022] The high-frequency equivalent circuit is integrated into a preset simulation software, the harmonic voltage source is injected to form an alternating current harmonic path to construct a first simulation simulation scene;

[0023] The harmonic characteristics of the to-be-tested flexible DC converter are simulated in the first simulation simulation scene.

[0024] Further, the integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation further comprises:

[0025] injecting a third harmonic to the to-be-tested flexible DC converter, and updating the calculation of the harmonic voltage component;

[0026] establishing a DC harmonic voltage source according to the updated harmonic voltage component;

[0027] injecting the DC harmonic voltage source into the simulation software to form a DC harmonic path, so as to construct a second simulation scenario;

[0028] simulating the harmonic characteristics of the to-be-tested flexible DC converter in the second simulation scenario.

[0029] Further, the integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation further comprises:

[0030] performing spectrum analysis on the longitudinal insulation current of each target device in the simulation process;

[0031] obtaining the longitudinal insulation current spectrum of each target device in the target frequency range based on the spectrum analysis result;

[0032] determining the spectrum risk of each target device according to the longitudinal insulation current spectrum of each target device in the target frequency range.

[0033] Another embodiment of the present application provides a harmonic analysis system for a flexible DC converter, comprising:

[0034] a parameter acquisition module configured to acquire key electrical parameters of a to-be-tested flexible DC converter;

[0035] an equivalent circuit construction module configured to construct a high-frequency equivalent circuit corresponding to each target device in the to-be-tested flexible DC converter according to the key electrical parameters;

[0036] a voltage source generation module configured to calculate a harmonic voltage component of a single bridge arm of a converter valve in the to-be-tested flexible DC converter according to the key electrical parameters, so as to generate a harmonic voltage source;

[0037] a simulation module configured to integrate the high-frequency equivalent circuit and the harmonic voltage source into simulation software for transient simulation, so as to obtain a transient simulation result;

[0038] a harmonic parameter analysis module configured to determine the harmonic voltage distribution and the harmonic current distribution of the to-be-tested flexible DC converter according to the transient simulation result.

[0039] A further embodiment of the present application provides a computer device comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the processor implementing the harmonic analysis method for a flexible DC converter as described above when executing the computer program.

[0040] A further embodiment of the present application provides a computer readable storage medium storing a computer program, wherein the computer program is executed by a device in which the computer readable storage medium is located to implement the harmonic analysis method for a flexible DC converter as described above.

[0041] Compared with the prior art, the beneficial effects of the embodiments of the present application are at least one of the following:

[0042] The present application constructs an ultra-high frequency equivalent circuit that accurately considers parasitic parameters of the valve tower, thereby ensuring the physical authenticity of the high-frequency resonance path and laying a reliable foundation for subsequent simulation; generates an injected harmonic voltage source in combination with the harmonic voltage component amplitude, which can accurately restore the high-frequency excitation source, while reducing simulation errors and improving simulation efficiency; in the simulation stage, the ultra-high frequency equivalent circuit is integrated and the harmonic voltage source is driven, which can accurately reproduce the characteristic distribution of the harmonic voltage and current of the flexible DC converter, thereby ensuring accurate customization of the equipment protection scheme on the basis that the simulation results closely match the high-frequency harmonic parameter characteristics of the actual flexible DC converter, effectively avoiding damage caused by ultra-high frequency harmonics during equipment operation, reducing the failure rate of flexible power transmission equipment, and significantly improving the safe operation level of the flexible DC converter. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a harmonic analysis method flowchart for a flexible DC converter in one of the embodiments of the present application;

[0044] Figure 2 is a high-frequency equivalent circuit model of a converter transformer considering stray parameters in one of the embodiments of the present application;

[0045] Figure 3 is a schematic diagram of the high-frequency harmonic current path of the bridge arm reactor located on the AC side of the converter valve in one of the embodiments of the present application;

[0046] Figure 4 is a schematic diagram of the high-frequency harmonic current path of the bridge arm reactor located on the DC side of the converter valve in one of the embodiments of the present application;

[0047] Figure 5 is a schematic diagram of the high-frequency harmonic voltage amplitude at different frequency points in Example 1 of the present application;

[0048] Figure 6is a high-frequency harmonic current simulation result schematic diagram of the converter transformer bushing and the wall bushing at different frequency points in example 1 of the present application;

[0049] Figure 7 is a high-frequency harmonic voltage amplitude schematic diagram at different frequency points in example 2 of the present application;

[0050] Figure 8 is a high-frequency harmonic current simulation result schematic diagram of the converter transformer bushing and the wall bushing at different frequency points in example 2 of the present application;

[0051] Figure 9 is a harmonic analysis system structure schematic diagram for the flexible DC converter in one of the embodiments of the present application;

[0052] Figure 10 is a structure block diagram of a preferred embodiment of a computer device provided by the present application;

[0053] The figure mark: C1~C2: converter transformer grid side winding to ground capacitance; C3~C5: converter transformer grid side winding inter-turn capacitance; C6: converter transformer grid side high voltage bushing to ground capacitance; C7: converter transformer grid side low voltage bushing to ground capacitance; C8~C9: converter transformer valve side bushing to ground capacitance; L1~L2: converter transformer grid side winding inductance; R1~R2: converter transformer grid side winding resistance. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. The purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0055] In the description of the present application, the terms "first", "second", "third", etc. are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", "third", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0056] In the description of the present application, it is necessary to explain that, unless otherwise defined, all the technical and scientific terms used by the present application are the same as the meanings understood by the persons skilled in the art. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application. For the persons skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0057] In the flexible DC system, the sub-module switching process is usually a nonlinear step process, each step process is rich in a large number of harmonic voltage components, the harmonic frequency is high and difficult to calculate. Based on this, an embodiment of the present application provides a harmonic analysis method for a flexible DC converter, specifically, please refer to Figure 1 , Figure 1 The flowchart of the harmonic analysis method for the flexible DC converter in one embodiment of the present application is shown, which includes the following steps:

[0058] S1-S2, obtain the key electrical parameters of the flexible DC converter to be measured, and construct the high-frequency equivalent circuit corresponding to each target device in the flexible DC converter to be measured according to the key electrical parameters.

[0059] In the selected target power transmission system, the impedance analyzer is used to measure the key electrical parameters of each target device in the flexible DC converter to be measured. Specifically, the target devices measured include converter valve devices, transformer devices and bushing devices.

[0060] Among them, the key electrical parameters of the converter valve device measured by the embodiment include: the equivalent capacitance C of the single valve layer of the single valve tower of the converter valve to ground and the equivalent capacitance C between the valve layers, the stray inductance L of the single sub-module of the flexible DC converter is measured by single sub-module switching test SM , the overall stray inductance L of the converter valve is calculated by combining the number N of single valve tower sub-module dynamic switching SMALL (L SMALL =L SM *N).

[0061] And the measured transformer parameters include: the turn-to-turn capacitance of the converter transformer, the winding-to-ground capacitance, and the segmented parameters of the inter-winding capacitance of the grid side and the valve side; The parameters of the bushing include the bushing-to-ground capacitance and other parameters.

[0062] According to the measured key electrical parameters, the high-frequency equivalent circuit corresponding to each target device is established to be configured in the simulation software to realize the subsequent simulation. Among them, for example, please refer to Figure 2As shown, it shows the high-frequency equivalent circuit model of the converter transformer considering the stray parameters established in the embodiment. As can be seen, the equivalent circuit model is composed of the ground capacitance of the converter transformer grid-side winding, the inter-turn capacitance, the ground capacitance of the converter transformer grid-side high / low voltage bushing, the ground capacitance of the converter transformer valve-side bushing, and the grid-side winding inductance and resistance of the converter transformer.

[0063] S3, calculating the harmonic voltage component of a single bridge arm of the converter valve in the to-be-tested flexible DC converter according to the key electrical parameters to generate a harmonic voltage source.

[0064] This step is the process of quantifying the ultra-high frequency voltage component generated by the bridge arm of the converter valve in the to-be-tested flexible DC converter. Specifically, according to the valve control frequency to power frequency ratio, the number of bridge arm sub-modules, the modulation ratio of the converter valve, and the average capacitor voltage of a single sub-module in the key electrical parameters, the harmonic voltage component of a single bridge arm at each frequency is calculated, which is represented by the following formula:

[0065]

[0066] In the formula, M is the modulation ratio, N2 is the number of bridge arm sub-modules, U c is the average capacitor voltage of the sub-module, q is the ratio of the valve control frequency to the power frequency, and k is the multiple of the valve control frequency (k = 1, 2, 3...); is the amplitude of the component, that is, the kω s ±ω0high-frequency harmonic voltage component formed by the power system modulation wave fundamental component at the modulation frequency, where ω s is the angular velocity corresponding to the pole control and valve control modulation frequency of the flexible DC converter, and ω0 is the angular velocity corresponding to the power frequency modulation wave.

[0067] According to the above formula, the three-phase bridge arm of the harmonic voltage component is phase-shifted by 120°, and the upper and lower bridge arms are phase-shifted by 180°, which can construct a harmonic voltage source and form a harmonic current path on the AC side of the high-frequency equivalent circuit.

[0068] S4-S5, integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation, and determining the harmonic voltage distribution and the harmonic current distribution of the to-be-tested flexible DC converter according to the simulation results.

[0069] In this embodiment, the high-frequency equivalent circuit is further integrated into the preset simulation software, the harmonic voltage source is injected to form an AC harmonic path to construct a first simulation simulation scene. For example, a suitable simulation software can be selected from EMTP-RV, PSCAD / EMTDC and MATLAB / Simulink, the equivalent circuit and the voltage source are integrated into the software to form a path, the simulation step is adjusted to 1us, and the harmonic current and the harmonic voltage distribution generated by the to-be-tested flexible DC converter are analyzed and calculated. For details, please refer toFigure 3 as shown, Figure 3 as shown, Figure 3 It can be seen from the equivalent circuit that the equivalent circuit includes two groups of flexible HVDC converter.

[0070] Then, in the first simulation scenario, the harmonic characteristics of the to-be-tested flexible HVDC converter are simulated to obtain the harmonic voltage and current distribution of the to-be-tested flexible HVDC converter.

[0071] It is worth noting that in some embodiments of the present application, a DC harmonic path can also be formed to simulate the to-be-tested flexible HVDC converter. Specifically, the process of forming the AC harmonic path is similar, except that the third harmonic needs to be injected into the to-be-tested flexible HVDC converter, and the harmonic voltage component is updated and calculated. At this time, the amplitude of the updated component will increase, which is specifically expressed as follows:

[0072]

[0073] According to the above formula, the harmonic voltage component with a frequency of kω s ±3ω0has the same phase in the three-phase bridge arm, and the upper and lower bridge arms have a phase difference of 180°. It should be understood that the third harmonic is a modulated wave.

[0074] According to the updated harmonic voltage component, a DC harmonic voltage source is established. Then, the DC harmonic voltage source is injected into the simulation software to form a DC harmonic path, so as to construct a second simulation scenario. For details, please refer to Figure 4 as shown, Figure 4 as shown,

[0075] Similarly, in the second simulation scenario, the harmonic characteristics of the to-be-tested flexible HVDC converter are simulated, so as to determine the harmonic voltage and current characteristics of the to-be-tested flexible HVDC converter according to the simulation results.

[0076] The present embodiment gives the following two specific examples to describe the component calculation and simulation process in detail:

[0077] Example 1: In this example, the measured HVDC voltage level is ±500kV, a single converter valve bears 500kV DC voltage, the maximum modulation ratio M max of the converter valve is 1.05, the number of single bridge arm sub-modules is N = 264, and the converter valve is a single valve tower, and the average value of the sub-module capacitor voltage U c= 2.2 kV; the pole control and valve control frequency is 10 kHz, the ratio of which to the power frequency is q = 200, the system uses third harmonic injection to improve the modulation ratio, and the third harmonic voltage amplitude is 1 / 6 of the fundamental frequency amplitude.

[0078] A high-frequency harmonic electromagnetic transient simulation model of the HVDC converter is built, in which the HVDC transformer and the converter valve are modeled in a high-frequency manner. During the simulation, based on the above measured parameter values and in combination with the harmonic voltage component calculation formula, the high-frequency harmonic voltage amplitudes of the converter valve at 9950 Hz, 10050 Hz, 19950 Hz and 20050 Hz are simulated to be 1.36 kV, 1.35 kV, 0.68 kV and 0.67 kV respectively. For details, please refer to Figure 5 , Figure 5 which shows the high-frequency harmonic voltage amplitudes at different frequency points in Example 1.

[0079] Further, during the simulation, it is determined by calculation that the harmonic current amplitude of the bushing on the HVDC transformer valve side reaches 0.3 A, and the harmonic current amplitude of the wall bushing reaches 0.5 A. For details, please refer to Figure 6 , Figure 6 which shows the high-frequency harmonic current simulation results of the bushing and the wall bushing of the HVDC transformer in Example 1.

[0080] Example 2: In this example, the measured HVDC voltage level is ±420 kV, a single converter valve bears 840 kV DC voltage, the maximum modulation ratio M max of the converter valve is 0.95, the number of sub-modules of a single bridge arm is N = 540, the converter valve is 3 valve towers in parallel, and the average value of the sub-module capacitor voltage U c = 2.2 kV; the pole control and valve control frequency is 10 kHz, the ratio of which to the power frequency is q = 200, the system uses third harmonic injection to improve the modulation ratio, and the third harmonic voltage amplitude is 1 / 6 of the fundamental frequency amplitude.

[0081] Similarly, a high-frequency harmonic electromagnetic transient simulation model of the HVDC converter is built, in which the HVDC transformer and the converter valve are modeled in a high-frequency manner. During the simulation, based on the above parameter values and in combination with the corresponding harmonic voltage component calculation formula, the high-frequency harmonic voltage amplitudes of the converter valve at 9950 Hz, 10050 Hz, 19950 Hz and 20050 Hz are simulated to be 2.01 kV, 1.99 kV, 1.01 kV and 0.99 kV respectively. For details, please refer to Figure 7 , Figure 7 which shows the high-frequency harmonic voltage amplitudes at different frequency points in Example 2.

[0082] Further, during the simulation, it is determined by calculation that the harmonic current amplitude of the bushing on the HVDC transformer valve side reaches 0.3 A, and the harmonic current amplitude of the wall bushing reaches 0.5 A. For details, please refer toFigure 8 shown, Figure 8 The high-frequency harmonic current simulation results of the converter transformer bushing and the wall bushing at different frequency points in Example 2 are shown.

[0083] In combination with the above examples, it can be understood that the embodiment can accurately obtain the harmonic voltage and current distribution generated by the to-be-tested converter by constructing a harmonic voltage component injection simulation environment. In order to further provide more effective data support for subsequent device maintenance and the like, the embodiment of the application further analyzes the frequency spectrum risk of the converter. Specifically, in the simulation process, the longitudinal insulation current generated by each target device is subjected to frequency spectrum analysis, and based on the analysis result, the longitudinal insulation current spectrum of each target device in the target frequency band range is obtained. For example, the embodiment preferably subjects the longitudinal insulation current of each target device to fast Fourier decomposition by using the Fourier algorithm to obtain the longitudinal insulation current spectrum of each device in the 10kHz-500kHz frequency band range.

[0084] According to the longitudinal insulation current spectrum, the frequency spectrum risk of each target device is determined. For example, in combination with the industry standard data, a risk threshold is set, such as that in the 50-200kHz frequency band, if the current amplitude is greater than 50mA, it is considered that there is a high risk of high-frequency ground fault. If it is considered according to the frequency spectrum that the current amplitude of the current at the 45kHz frequency point of the wall bushing is 65mA, it is considered that there is a risk that the very high frequency noise of the valve tower leaks through the stray capacitance of the bushing.

[0085] To sum up, the embodiment of the application reduces the error by modeling the fine high-frequency equivalent circuit of the flexible DC converter system, and quantitatively calculating the harmonic voltage amplitude by using the parameter values collected by the measuring instrument to construct the harmonic voltage source; the voltage source and the equivalent efficiency are integrated in the electromagnetic transient simulation software for simulation, and the harmonic current distribution and the harmonic voltage distribution of the to-be-tested converter are simulated, which solves the problem that the very high frequency harmonic of the flexible DC converter valve is difficult to calculate, and provides a basis for the manufacturing, maintenance and the like of the device; the embodiment further subjects the longitudinal current of the key devices such as the converter transformer bushing and the wall bushing to FFT decomposition, extracts the insulation current spectrum for risk judgment, and effectively avoids damage to the device.

[0086] An embodiment of the application provides a harmonic analysis system for a flexible DC converter. Figure 9 , Figure 9 The harmonic analysis system structure schematic diagram for the flexible DC converter in one of the embodiments of the application is shown, which comprises:

[0087] The parameter acquisition module M1 is used for acquiring the key electrical parameters of the to-be-tested flexible DC converter;

[0088] The equivalent circuit construction module M2 is used for constructing the high-frequency equivalent circuit corresponding to each target device according to the key electrical parameters.

[0089] a voltage source generation module M3, configured to calculate a harmonic voltage component of a single bridge arm of a converter valve in the flexible HVDC converter to be tested according to the key electrical parameters, so as to generate a harmonic voltage source;

[0090] a simulation module M4, configured to integrate the high-frequency equivalent circuit and the harmonic voltage source into a simulation software for transient simulation;

[0091] a harmonic parameter analysis module M5, configured to determine a harmonic voltage distribution and a harmonic current distribution of the flexible HVDC converter to be tested according to a simulation result.

[0092] In this embodiment, the parameter acquisition module M1 is used to acquire corresponding parameter data, specifically: an impedance analyzer is used to measure the key electrical parameters of each target device in the flexible HVDC converter to be tested respectively; the target device includes a converter valve device, a transformer device and a bushing device. Further, the equivalent circuit construction module M2 is used to construct an equivalent circuit.

[0093] In this embodiment, the voltage source generation module M3 is used to generate a driving power supply, specifically: according to the ratio of valve control frequency to power frequency, the number of bridge arm sub-modules, the modulation ratio of the converter valve and the average value of the capacitor voltage of a single sub-module in the key electrical parameters, the harmonic voltage component of a single bridge arm at each frequency is calculated; according to the harmonic voltage component, a harmonic voltage source is constructed.

[0094] The harmonic voltage component includes the following formula:

[0095]

[0096]

[0097] In the formula, M is the modulation ratio, N2 is the number of bridge arm sub-modules, U c is the average value of the sub-module capacitor voltage, q is the ratio of valve control frequency to power frequency, k is the multiple of valve control frequency, is the amplitude of the component, ω s is the angular velocity corresponding to the pole control and valve control modulation frequency of the HVDC converter, and ω0 is the angular velocity corresponding to the power frequency modulation wave.

[0098] Further, in this embodiment, the simulation module M4 is used for transient simulation, specifically:

[0099] The high-frequency equivalent circuit is integrated into a preset simulation software, the harmonic voltage source is injected to form an alternating current harmonic path to construct a first simulation simulation scene; under the first simulation simulation scene, the harmonic characteristics of the flexible HVDC converter to be tested are simulated.

[0100] In some embodiments of the present embodiment, the simulation process can also be: injecting a third harmonic into the to-be-tested flexible DC converter, updating the calculation of the harmonic voltage component; establishing a DC harmonic voltage source according to the updated harmonic voltage component; injecting the DC harmonic voltage source into the simulation software to form a DC harmonic path to construct a second simulation scenario; and simulating the harmonic characteristics of the to-be-tested flexible DC converter in the second simulation scenario.

[0101] In some embodiments of the present embodiment, it should be understood that, in the simulation process, the longitudinal insulation current of each target device is subjected to frequency spectrum analysis; based on the frequency spectrum analysis result, the longitudinal insulation current spectrum of each target device in the target frequency range is obtained; and the frequency spectrum risk of each target device is determined according to the longitudinal insulation current spectrum of each target device in the target frequency range.

[0102] As shown in Figure 10 The present embodiment also provides a computer device, Figure 10 A preferred embodiment of the computer device provided by the present embodiment is shown in a structure block diagram, the computer device comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the processor implementing the method as described above when executing the computer program.

[0103] Preferably, the computer program can be divided into one or more modules / units (such as computer program 1, computer program 2, …), which are stored in the memory and executed by the processor to complete the present embodiment. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the computer program in the computer device.

[0104] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor can also be any conventional processor. The processor is the control center of the terminal device, and connects various parts of the terminal device through various interfaces and lines.

[0105] The memory mainly includes a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required by a function, and the like, and the data storage area can store relevant data and the like. In addition, the memory can be a high-speed random access memory, and can also be a non-volatile memory such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, and the like, or the memory can also be other volatile solid-state storage devices.

[0106] It should be noted that the terminal device can include, but is not limited to, a processor and a memory, and those skilled in the art can understand that Figure 10 The structural block diagram is only an example of the terminal device, and does not constitute a limitation on the terminal device, and can include more or fewer components than the diagram, or combine certain components, or different components. Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above-mentioned embodiment methods. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), or the like.

[0107] Correspondingly, the embodiment of the present application provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the computer-readable storage medium is located is controlled to execute the steps in the above-mentioned embodiment methods, for example Figure 1 The steps S1-S5 described in the above-mentioned embodiment.

[0108] The above-mentioned embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the present application. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of protection of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A method for harmonic analysis of a flexible DC converter, characterized in that, The method comprises the following steps: obtaining key electrical parameters of a to-be-tested flexible DC converter; constructing a high-frequency equivalent circuit corresponding to each target device in the to-be-tested flexible DC converter according to the key electrical parameters; calculating harmonic voltage components of a single bridge arm of a converter valve in the to-be-tested flexible DC converter according to the key electrical parameters to generate a harmonic voltage source; integrating the high-frequency equivalent circuit and the harmonic voltage source into simulation software for transient simulation to obtain a transient simulation result; determining harmonic voltage distribution and harmonic current distribution of the to-be-tested flexible DC converter according to the transient simulation result.

2. The method for harmonic analysis of a flexible HVDC converter according to claim 1, characterized in that, The key electrical parameters of the to-be-tested flexible DC converter are obtained by using an impedance analyzer to measure the key electrical parameters corresponding to each target device in the to-be-tested flexible DC converter respectively; the target device includes a converter valve device, a transformer device and a bushing device.

3. The method for harmonic analysis of a flexible HVDC converter of claim 1, wherein, The harmonic voltage components of the single bridge arm of the converter valve in the to-be-tested flexible DC converter are calculated according to the key electrical parameters to generate the harmonic voltage source, which comprises the following steps: calculating the harmonic voltage components of the single bridge arm at each frequency according to the ratio of valve control frequency to power frequency, the number of bridge arm sub-modules, the modulation ratio of the converter valve and the average capacitor voltage of a single sub-module in the key electrical parameters; constructing the harmonic voltage source according to the harmonic voltage components.

4. The method for harmonic analysis of a flexible HVDC converter of claim 3, wherein, The harmonic voltage components include the following formula: In the formula, M is the modulation ratio, N2 is the number of bridge arm sub-modules, U c is the average value of sub-module capacitor voltage, q is the ratio of valve control frequency to power frequency, k is the multiple of valve control frequency, is the amplitude representation of the component, ω s is the angular velocity corresponding to the pole control and valve control modulation frequency of the flexible direct current converter, and ω0 is the angular velocity corresponding to the power frequency modulation wave.

5. The method for harmonic analysis of a flexible HVDC converter of claim 1, wherein, The high-frequency equivalent circuit and the harmonic voltage source are integrated into the simulation software for transient simulation, which comprises the following steps: integrating the high-frequency equivalent circuit into a preset simulation software, injecting the harmonic voltage source to form an alternating current harmonic path to construct a first simulation simulation scene; performing transient simulation on the harmonic characteristics of the to-be-tested flexible DC converter in the first simulation simulation scene.

6. The method for harmonic analysis of a flexible HVDC converter of claim 5, wherein, The high-frequency equivalent circuit and the harmonic voltage source are integrated into the simulation software for transient simulation, which further comprises the following steps: injecting a third harmonic into the to-be-tested flexible DC converter to update and calculate the harmonic voltage components; establishing a direct current harmonic voltage source according to the updated harmonic voltage components; injecting the direct current harmonic voltage source into the simulation software to form a direct current harmonic path to construct a second simulation simulation scene; simulating the harmonic characteristics of the to-be-tested flexible DC converter in the second simulation simulation scene.

7. The method for harmonic analysis of a flexible HVDC converter of claim 1, wherein, The high-frequency equivalent circuit and the harmonic voltage source are integrated into the simulation software for transient simulation, which further comprises the following steps: performing frequency spectrum analysis on the longitudinal insulation current of each target device during simulation; obtaining the frequency spectrum of the longitudinal insulation current of each target device within a target frequency range based on the frequency spectrum analysis result; determining the frequency spectrum risk of each target device according to the frequency spectrum of the longitudinal insulation current of each target device within the target frequency range.

8. A harmonic analysis system for a flexible DC converter, characterized by, The method comprises the following steps: a parameter acquisition module for obtaining key electrical parameters of a to-be-tested flexible DC converter; an equivalent circuit construction module for constructing a high-frequency equivalent circuit corresponding to each target device in the to-be-tested flexible DC converter according to the key electrical parameters; The voltage source generation module is configured to calculate harmonic voltage components of a single bridge arm of a converter valve in the to-be-tested flexible DC converter according to the key electrical parameters, so as to generate a harmonic voltage source; The simulation module is configured to integrate the high-frequency equivalent circuit and the harmonic voltage source into simulation software for transient simulation, so as to obtain a transient simulation result; The harmonic parameter analysis module is configured to determine harmonic voltage distribution and harmonic current distribution of the to-be-tested flexible DC converter according to the transient simulation result.

9. The harmonic analysis system for a flexible DC converter of claim 8, wherein, The key electrical parameters of the to-be-tested flexible DC converter are obtained by measuring the key electrical parameters corresponding to each target device in the to-be-tested flexible DC converter by using an impedance analyzer; the target device includes a converter valve device, a transformer device and a bushing device.

10. The harmonic analysis system for a flexible DC converter of claim 8, wherein, The harmonic voltage components of the single bridge arm of the converter valve in the to-be-tested flexible DC converter are calculated according to the key electrical parameters, so as to generate a harmonic voltage source, including: The harmonic voltage components of the single bridge arm at each frequency are calculated according to the ratio of valve control frequency to power frequency, the number of bridge arm sub-modules, the modulation ratio of the converter valve and the average capacitor voltage of a single sub-module in the key electrical parameters; The harmonic voltage source is constructed according to the harmonic voltage components.

11. The harmonic analysis system for a flexible DC converter of claim 10, wherein, The harmonic voltage components include the following formula: In the formula, M is the modulation ratio, N2 is the number of bridge arm sub-modules, U c is the average value of sub-module capacitor voltage, q is the ratio of valve control frequency to power frequency, k is the multiple of valve control frequency, is the amplitude representation of the component, ω s is the angular velocity corresponding to the pole control and valve control modulation frequency of the flexible direct current converter, and ω0 is the angular velocity corresponding to the power frequency modulation wave.

12. The harmonic analysis system for a flexible DC converter of claim 8, wherein, The high-frequency equivalent circuit is integrated into the preset simulation software, and the harmonic voltage source is injected to form an alternating current harmonic path to construct a first simulation simulation scene; The harmonic characteristics of the to-be-tested flexible DC converter are simulated under the first simulation simulation scene. The high-frequency equivalent circuit and the harmonic voltage source are integrated into the simulation software for transient simulation, including:

13. The harmonic analysis system for a flexible DC converter of claim 12, wherein, The third harmonic is injected into the to-be-tested flexible DC converter, and the harmonic voltage components are updated and calculated; The DC harmonic voltage source is established according to the updated harmonic voltage components; The DC harmonic voltage source is injected into the simulation software to form a DC harmonic path to construct a second simulation simulation scene; The harmonic characteristics of the to-be-tested flexible DC converter are simulated under the second simulation simulation scene. The high-frequency equivalent circuit and the harmonic voltage source are integrated into the simulation software for transient simulation, including:

14. The harmonic analysis system for a flexible DC converter of claim 8, wherein, During the simulation process, the longitudinal insulation current of each target device is subjected to frequency spectrum analysis; Based on the frequency spectrum analysis result, the longitudinal insulation current spectrum of each target device within a target frequency range is obtained; The frequency spectrum risk of each target device is determined according to the longitudinal insulation current spectrum of each target device within the target frequency range. The processor, the memory and the computer program stored in the memory and configured to be executed by the processor are included, and the processor implements the harmonic analysis method for the flexible DC converter according to any one of claims 1 to 7 when the computer program is executed.

15. A computer device, comprising: ​ 16. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and when a device where the computer readable storage medium is located executes the computer program, the harmonic analysis method for the flexible HVDC converter is realized.

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