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

Abstract

The application discloses a kind of harmonic analysis method, system, equipment and medium for flexible direct current converter, it is related to flexible direct current transmission technical field, the method includes: obtaining the key electrical parameter of to-be-tested flexible direct current converter;According to the high-frequency equivalent circuit corresponding to each target device is constructed according to key electrical parameter;According to the harmonic voltage component of the single bridge arm of the converter valve in to-be-tested flexible direct current converter is calculated according to key electrical parameter, to generate harmonic voltage source;High-frequency equivalent circuit and harmonic voltage source are integrated into simulation software to carry out transient simulation;According to simulation result, the harmonic voltage distribution and harmonic current distribution of to-be-tested flexible direct current converter are determined, to realize effectively avoiding equipment operation risk, reduce the failure rate of flexible power transmission equipment.

Description

Technical Field

[0001] This invention relates to the field of flexible DC transmission technology, and in particular to harmonic analysis methods, systems, equipment and media for flexible DC converters. Background Technology

[0002] Flexible DC transmission systems have four-quadrant operation capabilities and can operate independently without relying on the power grid. They are particularly suitable for large-scale new energy sources supplying power to load centers from weak AC grids and for transmitting deep-sea wind power. They are one of the main technical means for large-scale new energy transmission and deep-sea wind power transmission in the Gobi Desert region in the future.

[0003] Compared to conventional DC converter valves, flexible DC converter valves do not generate a large number of low- and mid-frequency harmonics and do not require AC / DC filters. However, recent studies have found that flexible DC systems with modular multilevel converters as their main topology still generate certain characteristic frequencies of relatively high harmonics, which are integer multiples of the pole control and valve control frequencies. Prolonged harmonic voltages and currents can damage critical equipment such as wall bushings and converter transformers. Therefore, quantitative analysis of the harmonic voltage and current parameters generated by flexible DC converters is crucial to provide effective data support for equipment manufacturing and protection, and to prevent equipment damage.

[0004] Traditional on-site measurement methods, such as those using probe equipment, are often subject to external environmental interference such as electromagnetic interference, are time-consuming, have low data accuracy, large errors, and low efficiency.

[0005] Therefore, how to effectively determine the high-frequency harmonic parameters of flexible DC converters and ensure data accuracy has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention provides a harmonic analysis method, system, device, and medium for flexible DC converters, solving the problem of how to achieve harmonic characteristic simulation analysis through equivalent models of various power transmission equipment, thereby improving the accuracy of the output results.

[0007] To address the aforementioned technical problems, embodiments of the present invention provide a harmonic analysis method for flexible DC converters, comprising: Obtain the key electrical parameters of the flexible DC converter under test; Construct high-frequency equivalent circuits for each target device in the flexible DC converter under test based on the key electrical parameters; Based on the key electrical parameters, the harmonic voltage components of a single bridge arm of the converter valve in the flexible DC converter under test are calculated to generate a harmonic voltage source. The high-frequency equivalent circuit and the harmonic voltage source are integrated into simulation software for transient simulation to obtain transient simulation results; The harmonic voltage distribution and harmonic current distribution of the flexible DC converter under test are determined based on the transient simulation results.

[0008] Furthermore, the acquisition of key electrical parameters of the flexible DC converter under test includes: The key electrical parameters of each target device in the flexible DC converter under test are measured using an impedance analyzer; the target devices include converter valve devices, transformer devices, and bushing devices.

[0009] Furthermore, the step of calculating the harmonic voltage components of a single bridge arm of the converter valve in the flexible DC converter under test based on the key electrical parameters to generate a harmonic voltage source includes: Based on the ratio of valve control frequency to power frequency, the number of bridge arm sub-modules, the converter valve modulation ratio, and the average capacitor voltage of a single sub-module in the key electrical parameters, calculate the harmonic voltage components of a single bridge arm at each frequency. The harmonic voltage source is constructed based on the harmonic voltage components.

[0010] Furthermore, the harmonic voltage components include the following formula: In the formula, M The modulation ratio, The number of bridge arm sub-modules. U c This represents the average voltage of the submodule capacitors. q This is the ratio of the valve control frequency to the power frequency. k It is a multiple of the valve control frequency. The amplitude of the component is represented. ω s The angular velocity corresponding to the pole control and valve control modulation frequencies of the flexible DC converter. ω 0 represents the angular velocity corresponding to the power frequency modulation wave.

[0011] Furthermore, the integration of the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation includes: The high-frequency equivalent circuit is integrated into the preset simulation software, and the harmonic voltage source is injected to form an AC harmonic path to construct the first simulation scenario. In the first simulation scenario, transient simulation is performed on the harmonic characteristics of the flexible DC converter under test.

[0012] Furthermore, the integration of the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation also includes: A third harmonic is injected into the flexible DC converter under test, and the harmonic voltage components are updated and calculated. Based on the updated harmonic voltage components, a DC-side harmonic voltage source is established; The DC harmonic voltage source is injected into the simulation software to form a DC harmonic path in order to construct a second simulation scenario; In the second simulation scenario, the harmonic characteristics of the flexible DC converter under test are simulated.

[0013] Furthermore, the integration of the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation also includes: During the simulation, the longitudinal insulation current of each target device was analyzed by spectrum analysis. Based on the spectrum analysis results, the longitudinal insulation current spectrum of each target device within the target frequency band is obtained; The spectral risk of each target device is determined based on the longitudinal insulation current spectrum of each target device within the target frequency band.

[0014] Another embodiment of the present invention provides a harmonic analysis system for a flexible DC converter, comprising: The parameter acquisition module is used to acquire the key electrical parameters of the flexible DC converter under test. The equivalent circuit construction module is used to construct the high-frequency equivalent circuits corresponding to each target device in the flexible DC converter under test based on key electrical parameters. The voltage source generation module is used to calculate the harmonic voltage components of a single bridge arm of the converter valve in the flexible DC converter under test based on key electrical parameters, so as to generate a harmonic voltage source. The simulation module is used to integrate high-frequency equivalent circuits and harmonic voltage sources into simulation software for transient simulation and to obtain transient simulation results. The harmonic parameter analysis module is used to determine the harmonic voltage and harmonic current distribution of the flexible DC converter under test based on transient simulation results.

[0015] Another embodiment of the present invention provides a computer device including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor executes the computer program to implement the harmonic analysis method for a flexible DC converter as described above.

[0016] In another embodiment of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium storing a computer program, wherein when the device containing the computer-readable storage medium executes the computer program, it implements the harmonic analysis method for flexible DC converters as described above.

[0017] Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following: This invention ensures the physical authenticity of the high-frequency resonant path by constructing an ultra-high frequency equivalent circuit that accurately considers the parasitic parameters of the valve tower, thus laying a reliable foundation for subsequent simulations. By combining the amplitude of harmonic voltage components to generate an injected harmonic voltage source, the high-frequency excitation source can be accurately reproduced, while reducing simulation errors and improving simulation efficiency. During the simulation phase, integrating the ultra-high frequency equivalent circuit and driving the harmonic voltage source accurately reproduces the characteristic distribution of harmonic voltage and current in the flexible DC converter. This ensures that the simulation results closely match the high-frequency harmonic parameter characteristics of the actual flexible DC converter, guaranteeing precise customization of the equipment protection scheme. This effectively avoids the risk of damage caused by ultra-high frequency harmonics during equipment operation, reduces the failure rate of flexible power transmission equipment, and significantly improves the safe operation level of the flexible DC converter. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of a harmonic analysis method for a flexible DC converter in one embodiment of the present invention; Figure 2 This is a high-frequency equivalent circuit model of a converter transformer considering stray parameters in one embodiment of the present invention; Figure 3 This 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 embodiment of the present invention. Figure 4 This 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 embodiment of the present invention. Figure 5 This is a schematic diagram of the high-frequency harmonic voltage amplitude at different frequency points in Example 1 of the present invention; Figure 6 This is a schematic diagram of the high-frequency harmonic current simulation results of converter transformer bushings and through-wall bushings at different frequency points in Example 1 of this invention. Figure 7 This is a schematic diagram of the high-frequency harmonic voltage amplitude at different frequency points in Example 2 of the present invention; Figure 8 This is a schematic diagram of the high-frequency harmonic current simulation results of converter transformer bushings and through-wall bushings at different frequency points in Example 2 of the present invention. Figure 9 This is a schematic diagram of the harmonic analysis system for a flexible DC converter in one embodiment of the present invention; Figure 10 A structural block diagram of a preferred embodiment of a computer device provided by the present invention; Figure reference numerals: 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 Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0022] In flexible DC systems, the submodule switching process is typically a nonlinear step process, each of which is rich in numerous harmonic voltage components. These harmonic frequencies are high and difficult to calculate. Therefore, one embodiment of this invention provides a harmonic analysis method for flexible DC converters. For details, please refer to... Figure 1 , Figure 1 The diagram shown is a schematic flowchart of a harmonic analysis method for a flexible DC converter according to one embodiment of the present invention, including the following steps: S1~S2: Obtain the key electrical parameters of the flexible DC converter under test, and construct the high-frequency equivalent circuits corresponding to each target device in the flexible DC converter under test based on the key electrical parameters.

[0023] In the selected target power transmission system, this embodiment uses an impedance analyzer to measure the key electrical parameters of each target device in the flexible DC converter under test. Specifically, the target devices measured include converter valve devices, transformer devices, and bushing devices.

[0024] The key electrical parameters of the converter valve equipment measured in this embodiment include: the equivalent capacitance C of a single valve layer to ground in the converter valve tower and the equivalent capacitance C between valve layers; and the stray inductance of a single submodule of the flexible DC converter valve obtained through single submodule switching tests. L SM Combined with the dynamic switching number of single-valve tower submodules N The overall stray inductance of the converter valve was calculated. L SMALL ( L SMALL = L SM * N ).

[0025] In addition, the measured transformer parameters include: segmented parameters of the converter transformer inter-turn capacitance, winding-to-ground capacitance, and inter-winding capacitance on the grid side and valve side; bushing parameters include parameters such as the through-wall bushing-to-ground capacitance.

[0026] Based on the measured key electrical parameters, high-frequency equivalent circuits corresponding to each target device are established and configured in simulation software for subsequent simulation. For example, please refer to... Figure 2 As shown, this illustrates the high-frequency equivalent circuit model of the converter transformer considering stray parameters established for this embodiment. It can be seen that this equivalent circuit model consists of several converter grid-side windings' ground capacitance, inter-turn capacitance, converter grid-side high / low voltage bushing ground capacitance, converter transformer valve-side bushing ground capacitance, and converter grid-side winding inductance and resistance connections.

[0027] S3. Calculate the harmonic voltage components of a single bridge arm of the converter valve in the flexible DC converter under test based on the key electrical parameters, so as to generate a harmonic voltage source.

[0028] This step involves quantifying the ultra-high frequency voltage components generated by the bridge arms of the converter valves in the flexible DC converter under test. Specifically, based on the ratio of valve control frequency to power frequency, the number of bridge arm sub-modules, the converter valve modulation ratio, and the average capacitor voltage of a single sub-module, the harmonic voltage components of a single bridge arm at each frequency are calculated, expressed by the following formula: In the formula, M The modulation ratio, The number of bridge arm sub-modules. Uc This represents the average voltage of the submodule capacitors. q This is the ratio of the valve control frequency to the power frequency. k A multiple of the valve control frequency ( k =1, 2, 3...); The amplitude of the component is represented by the fundamental frequency component of the modulation wave of the transmission system at the modulation frequency. High-frequency harmonic voltage components, among which... The angular velocity corresponding to the pole control and valve control modulation frequencies of the flexible DC converter. This represents the angular velocity corresponding to the power frequency modulation wave.

[0029] According to the above formula, the three-phase bridge arms of the harmonic voltage component are 120° out of phase and the upper and lower bridge arms are 180° out of phase. This allows a harmonic voltage source to be constructed, forming a harmonic current path on the AC side of the high-frequency equivalent circuit.

[0030] S4~S5. Integrate the high-frequency equivalent circuit and harmonic voltage source into the simulation software for transient simulation, and determine the harmonic voltage distribution and harmonic current distribution of the flexible DC converter under test based on the simulation results.

[0031] This embodiment further integrates the high-frequency equivalent circuit into a preset simulation software, injecting a harmonic voltage source to form an AC harmonic path to construct the first simulation scenario. For example, a suitable simulation software can be selected from EMTP-RV, PSCAD / EMTDC, and MATLAB / Simulink. The equivalent circuit and voltage source are integrated into the software, and the simulation step size is adjusted to 1µs. The distribution of harmonic current and harmonic voltage generated by the flexible DC converter under test is then analyzed and calculated. For details, please refer to... Figure 3 As shown, Figure 3 The diagram shows a high-frequency harmonic current path formed by the bridge arm reactor located on the AC side of the converter valve, i.e., the aforementioned AC harmonic path. From Figure 3 As can be seen from the diagram, the equivalent circuit consists of two sets of flexible DC converter valves.

[0032] Next, in the first simulation scenario, transient simulation of the harmonic characteristics of the flexible DC converter under test is performed to obtain the harmonic voltage and current distribution of the flexible DC converter under test.

[0033] It is worth noting that in some embodiments of the present invention, a DC harmonic path can also be formed to perform transient simulation of the flexible DC converter under test. Specifically, similar to the formation process of the AC harmonic path, the difference is that a third harmonic needs to be injected into the flexible DC converter under test, and the harmonic voltage components are updated and calculated. At this time, the amplitude of the updated components will increase, as specifically shown below: According to the above formula, the frequency is... kω s ±3 ω The third harmonic voltage component has the same phase in all three phases of the bridge arm, with a 180° phase difference between the upper and lower bridge arms. It should be understood that the third harmonic is injected as a modulating wave.

[0034] Based on the updated harmonic voltage components, a DC-side harmonic voltage source is established. Then, this DC-side harmonic voltage source is injected into the simulation software to form a DC harmonic path, thereby constructing the second simulation scenario. For details, please refer to... Figure 4 As shown, Figure 4 The diagram shows the high-frequency harmonic current path of the bridge arm reactor located on the DC side of the converter valve, i.e., the DC harmonic path. It can be seen that a converter transformer is connected between the two sets of flexible DC converter valves.

[0035] Similarly, in the second simulation scenario, the harmonic characteristics of the flexible DC converter under test are simulated, and the characteristics of the harmonic voltage and current of the flexible DC converter under test are determined based on the simulation results.

[0036] This embodiment provides the following two specific examples to describe in detail the above component calculation and simulation process: Example 1: In this example, the measured flexible DC voltage level is ±500kV, a single converter valve handles 500kV DC voltage, and the maximum modulation ratio of the converter valve is... M max =1.05, the number of submodules in a single bridge arm is N =264, the converter valve is a single valve tower, and the average voltage of the submodule capacitor is... U c =2.2kV; the pole control and valve control frequency is 10kHz, and its ratio 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.

[0037] A high-frequency harmonic electromagnetic transient simulation model of a flexible DC converter was constructed, with the converter transformer and converter valve modeled using a high-frequency approach. During the simulation, based on the measured parameter values ​​and the harmonic voltage component calculation formula, the high-frequency harmonic voltage amplitudes of the converter valve at 9950Hz, 10050Hz, 19950Hz, and 20050Hz were calculated to be 1.36kV, 1.35kV, 0.68kV, and 0.67kV, respectively. For details, please refer to [reference needed]. Figure 5 As shown, Figure 5 The following is an example of the high-frequency harmonic voltage amplitude at different frequency points in Example 1.

[0038] Furthermore, during the simulation, calculations determined that the harmonic current amplitude of the converter transformer valve-side bushing reached 0.3A, and the harmonic current amplitude of the through-wall bushing reached 0.5A. For details, please refer to [link / reference needed]. Figure 6 As shown, Figure 6 The simulation results of high-frequency harmonic currents for converter transformer bushings and through-wall bushings at different frequency points are shown in Example 1.

[0039] Example 2: In this example, the measured flexible DC voltage level is ±420kV, a single converter valve handles 840kV DC voltage, and the maximum modulation ratio of the converter valve is... M max =0.95, the number of submodules in a single bridge arm is N =540, the converter valve consists of 3 valve towers connected in parallel, the average value of the submodule capacitor voltage U c =2.2kV; the pole control and valve control frequency is 10kHz, and its ratio 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.

[0040] Similarly, a high-frequency harmonic electromagnetic transient simulation model of the flexible DC converter was constructed, with the converter transformer and converter valve modeled using a high-frequency approach. During the simulation, based on the aforementioned parameter values ​​and the corresponding harmonic voltage component calculation formulas, the high-frequency harmonic voltage amplitudes of the converter valve at 9950Hz, 10050Hz, 19950Hz, and 20050Hz were calculated to be 2.01kV, 1.99kV, 1.01kV, and 0.99kV, respectively. For details, please refer to [link / reference needed]. Figure 7 As shown, Figure 7 The following is an example of the high-frequency harmonic voltage amplitude at different frequency points in Example 2.

[0041] Furthermore, during the simulation, calculations determined that the harmonic current amplitude of the converter transformer valve-side bushing reached 0.3A, and the harmonic current amplitude of the through-wall bushing reached 0.5A. For details, please refer to [link / reference needed]. Figure 8 As shown, Figure 8 The results of high-frequency harmonic current simulations for converter transformer bushings and through-wall bushings at different frequency points are shown in Example 2.

[0042] Based on the above examples, it can be understood that this embodiment, by constructing a harmonic voltage component injection simulation environment, can accurately obtain the distribution of harmonic voltage and current generated by the converter under test. To further provide more effective data support for subsequent equipment maintenance and other processes, this embodiment of the invention will also analyze the spectral risks of the converter. Specifically, during the simulation process, the longitudinal insulation current generated by each target device is subjected to spectral analysis. Based on the analysis results, the longitudinal insulation current spectrum of each target device within the target frequency band is obtained. For example, this embodiment preferably uses a Fourier algorithm to perform Fast Fourier Decomposition on the longitudinal insulation current of each target device to obtain the longitudinal insulation current spectrum of each device within the 10kHz~500kHz frequency band.

[0043] Based on the longitudinal insulation current spectrum, the spectral risk of each target device is determined. For example, risk thresholds are set using industry standard data. If the current amplitude is >50mA in the 50~200kHz frequency band, a high risk of high-frequency grounding failure is considered. If, based on the spectrum, the current amplitude of a through-wall bushing at 45kHz is 65mA, a risk of leakage of ultra-high frequency noise from the valve tower through stray capacitance in the bushing is considered.

[0044] In summary, this embodiment of the invention reduces errors by performing refined high-frequency equivalent circuit modeling on the flexible DC converter system and quantifying the harmonic voltage amplitude using parameter values ​​collected by the measuring instrument to construct a harmonic voltage source. The voltage source and equivalent efficiency are integrated into electromagnetic transient simulation software for simulation, simulating the harmonic current and voltage distribution of the converter under test. This overcomes the difficulty in calculating ultra-high frequency harmonics in flexible DC converter valves, providing a basis for equipment manufacturing and maintenance. Furthermore, this embodiment performs FFT decomposition on the longitudinal current of key equipment such as converter transformer bushings and through-wall bushings, extracting the insulation current spectrum for risk assessment, effectively preventing equipment damage.

[0045] One embodiment of the present invention provides a harmonic analysis system for flexible DC converters. For details, please refer to [link to relevant documentation]. Figure 9 , Figure 9 The diagram shown illustrates the structure of a harmonic analysis system for a flexible DC converter according to one embodiment of the present invention, comprising: The parameter acquisition module M1 is used to acquire the key electrical parameters of the flexible DC converter under test. The equivalent circuit construction module M2 is used to construct the high-frequency equivalent circuits corresponding to each target device based on key electrical parameters. The voltage source generation module M3 is used to calculate the harmonic voltage components of a single bridge arm of the converter valve in the flexible DC converter under test based on key electrical parameters, so as to generate a harmonic voltage source. Simulation module M4 is used to integrate high-frequency equivalent circuits and harmonic voltage sources into simulation software for transient simulation. The harmonic parameter analysis module M5 is used to determine the harmonic voltage distribution and harmonic current distribution of the flexible DC converter under test based on the simulation results.

[0046] In this embodiment, the corresponding parameter data is acquired through the parameter acquisition module M1. Specifically, an impedance analyzer is used to measure the key electrical parameters corresponding to each target device in the flexible DC converter under test; the target devices include converter valve devices, transformer devices, and bushing devices. Furthermore, in this embodiment, an equivalent circuit is constructed through the equivalent circuit construction module M2.

[0047] In this embodiment, the driving power supply is generated by the voltage source generation module M3. Specifically, the harmonic voltage components of a single bridge arm at each frequency are calculated based on 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 then constructed based on the harmonic voltage components.

[0048] Harmonic voltage components include the following formulas: In the formula, M The modulation ratio, The number of bridge arm sub-modules. U c This represents the average voltage of the submodule capacitors. q This is the ratio of the valve control frequency to the power frequency. k It is a multiple of the valve control frequency. The amplitude of the component is represented. ω s The angular velocity corresponding to the pole control and valve control modulation frequencies of the flexible DC converter. ω 0 represents the angular velocity corresponding to the power frequency modulation wave.

[0049] Furthermore, in this embodiment, transient simulation is performed using simulation module M4, specifically as follows: The high-frequency equivalent circuit is integrated into the preset simulation software, and a harmonic voltage source is injected to form an AC harmonic path to construct the first simulation scenario; under the first simulation scenario, the harmonic characteristics of the flexible DC converter under test are transiently simulated.

[0050] In some embodiments of this example, the simulation process may also include: injecting a third harmonic into the flexible DC converter under test and updating the harmonic voltage components; establishing a DC harmonic voltage source based on the updated harmonic voltage components; injecting the DC harmonic voltage source into the simulation software to form a DC harmonic path, thereby constructing a second simulation scenario; and simulating the harmonic characteristics of the flexible DC converter under test in the second simulation scenario.

[0051] In some implementations of this embodiment, it should be understood that during the simulation process, the longitudinal insulation current of each target device is subjected to spectral analysis; based on the spectral analysis results, the longitudinal insulation current spectrum of each target device within the target frequency band is obtained; and based on the longitudinal insulation current spectrum of each target device within the target frequency band, the spectral risk of each target device is determined.

[0052] like Figure 10 As shown, this embodiment of the invention also provides a computer device. Figure 10 This is a structural block diagram of a preferred embodiment of a computer device provided by the present invention. The computer device includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the method described above.

[0053] Preferably, the computer program can be divided into one or more modules / units (such as computer program 1, computer program 2, ...), and the one or more modules / units are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and the instruction segments are used to describe the execution process of the computer program in the computer device.

[0054] The processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), 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 be any conventional processor. The processor is the control center of the terminal device, connecting various parts of the terminal device through various interfaces and lines.

[0055] The memory mainly includes a program storage area and a data storage area. The program storage area can store the operating system, applications required for at least one function, etc., while the data storage area can store related data, etc. Furthermore, the memory can be a high-speed random access memory, or a non-volatile memory, such as a plug-in hard drive, a SmartMedia Card (SMC), a Secure Digital (SD) card, and a Flash Card, or other volatile solid-state storage devices.

[0056] It should be noted that the aforementioned terminal devices may include, but are not limited to, processors and memory, as will be understood by those skilled in the art. Figure 10 The structural block diagram is merely an example of a terminal device and does not constitute a limitation on the terminal device. It may include more or fewer components than shown, or combine certain components, or use different components. Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium may be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0057] Accordingly, embodiments of the present invention provide a computer-readable storage medium, the computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform the steps in the method of the above embodiments, for example... Figure 1 Steps S1 to S5 as described above.

[0058] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A harmonic analysis method for flexible DC converters, characterized in that, include: Obtain the key electrical parameters of the flexible DC converter under test; Construct high-frequency equivalent circuits for each target device in the flexible DC converter under test based on the key electrical parameters; The harmonic voltage components of a single bridge arm of the converter valve in the flexible DC converter under test are calculated based on the key electrical parameters to generate a harmonic voltage source. Specifically, the harmonic voltage components of a single bridge arm at each frequency are calculated based on the ratio of valve control frequency to power frequency, the number of bridge arm sub-modules, the converter valve modulation ratio, and the average capacitor voltage of a single sub-module in the key electrical parameters. The harmonic voltage source is constructed based on the harmonic voltage components; the harmonic voltage components include the following formulas: In the formula, M The modulation ratio, The number of bridge arm sub-modules. U c This represents the average voltage of the submodule capacitors. q This is the ratio of the valve control frequency to the power frequency. k It is a multiple of the valve control frequency. The amplitude of the component is represented. ω s The angular velocity corresponding to the pole control and valve control modulation frequencies of the flexible DC converter. ω 0 represents the angular velocity corresponding to the power frequency modulation wave; The high-frequency equivalent circuit and the harmonic voltage source are integrated into simulation software for transient simulation to obtain transient simulation results; The harmonic voltage distribution and harmonic current distribution of the flexible DC converter under test are determined based on the transient simulation results.

2. The harmonic analysis method for flexible DC converters as described in claim 1, characterized in that, The acquisition of key electrical parameters of the flexible DC converter under test includes: measuring the key electrical parameters corresponding to each target device in the flexible DC converter under test using an impedance analyzer; the target devices include converter valve devices, transformer devices, and bushing devices.

3. The harmonic analysis method for flexible DC converters as described in claim 1, characterized in that, The step of integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation includes: The high-frequency equivalent circuit is integrated into the preset simulation software, and the harmonic voltage source is injected to form an AC harmonic path to construct the first simulation scenario. In the first simulation scenario, transient simulation is performed on the harmonic characteristics of the flexible DC converter under test.

4. The harmonic analysis method for flexible DC converters as described in claim 3, characterized in that, The step of integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation also includes: A third harmonic is injected into the flexible DC converter under test, and the harmonic voltage components are updated and calculated. Based on the updated harmonic voltage components, a DC-side harmonic voltage source is established; The DC-side harmonic voltage source is injected into the simulation software to form a DC harmonic path in order to construct a second simulation scenario; In the second simulation scenario, the harmonic characteristics of the flexible DC converter under test are simulated.

5. The harmonic analysis method for flexible DC converters as described in claim 1, characterized in that, The step of integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation also includes: During the simulation, the longitudinal insulation current of each target device was analyzed by spectrum analysis. Based on the spectrum analysis results, the longitudinal insulation current spectrum of each target device within the target frequency band is obtained; The spectral risk of each target device is determined based on the longitudinal insulation current spectrum of each target device within the target frequency band.

6. A harmonic analysis system for flexible DC converters, characterized in that, include: The parameter acquisition module is used to acquire the key electrical parameters of the flexible DC converter under test. The equivalent circuit construction module is used to construct the high-frequency equivalent circuits corresponding to each target device in the flexible DC converter under test based on key electrical parameters. The voltage source generation module is used to calculate the harmonic voltage components of a single bridge arm of the converter valve in the flexible DC converter under test based on key electrical parameters, so as to generate a harmonic voltage source; specifically, based on 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 components of a single bridge arm at each frequency are calculated. The harmonic voltage source is constructed based on the harmonic voltage components; the harmonic voltage components include the following formulas: In the formula, M The modulation ratio, The number of bridge arm sub-modules. U c This represents the average voltage of the submodule capacitors. q This is the ratio of the valve control frequency to the power frequency. k It is a multiple of the valve control frequency. The amplitude of the component is represented. ω s The angular velocity corresponding to the pole control and valve control modulation frequencies of the flexible DC converter. ω 0 represents the angular velocity corresponding to the power frequency modulation wave; The simulation module is used to integrate high-frequency equivalent circuits and harmonic voltage sources into simulation software for transient simulation and to obtain transient simulation results. The harmonic parameter analysis module is used to determine the harmonic voltage and harmonic current distribution of the flexible DC converter under test based on transient simulation results.

7. The harmonic analysis system for flexible DC converters as described in claim 6, characterized in that, The acquisition of key electrical parameters of the flexible DC converter under test includes: measuring the key electrical parameters corresponding to each target device in the flexible DC converter under test using an impedance analyzer; the target devices include converter valve devices, transformer devices, and bushing devices.

8. The harmonic analysis system for flexible DC converters as described in claim 6, characterized in that, The step of integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation includes: The high-frequency equivalent circuit is integrated into the preset simulation software, and the harmonic voltage source is injected to form an AC harmonic path to construct the first simulation scenario. In the first simulation scenario, transient simulation is performed on the harmonic characteristics of the flexible DC converter under test.

9. The harmonic analysis system for flexible DC converters as described in claim 8, characterized in that, The step of integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation also includes: A third harmonic is injected into the flexible DC converter under test, and the harmonic voltage components are updated and calculated. Based on the updated harmonic voltage components, a DC-side harmonic voltage source is established; The DC-side harmonic voltage source is injected into the simulation software to form a DC harmonic path in order to construct a second simulation scenario; In the second simulation scenario, the harmonic characteristics of the flexible DC converter under test are simulated.

10. The harmonic analysis system for flexible DC converters as described in claim 6, characterized in that, The step of integrating the high-frequency equivalent circuit and the harmonic voltage source into the simulation software for transient simulation also includes: During the simulation, the longitudinal insulation current of each target device was analyzed by spectrum analysis. Based on the spectrum analysis results, the longitudinal insulation current spectrum of each target device within the target frequency band is obtained; The spectral risk of each target device is determined based on the longitudinal insulation current spectrum of each target device within the target frequency band.

11. A computer device, characterized in that, It includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements the harmonic analysis method for a flexible DC converter as described in any one of claims 1 to 5.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein when the device containing the computer-readable storage medium executes the computer program, it implements the harmonic analysis method for flexible DC converters as described in any one of claims 1 to 5.

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