Equivalent circuit of converter valve tower, and insulation detection method and system of converter valve

Abstract

The invention provides an equivalent circuit of a converter valve tower and an insulation detection method and system of a converter valve, and the equivalent circuit comprises a plurality of load branches connected in parallel, each load branch comprises an equivalent load, and different load branches comprise different equivalent loads. Equivalent loads included in different load branches are used for being equivalent to characteristics of converter valve towers in different frequency bands; the equivalent load is one of an equivalent resistance load, an equivalent capacitance load and a composite equivalent load composed of an inductor, a resistor and a capacitor, the characteristics of the converter valve tower are different when the converter valve tower operates in different frequency bands, and the characteristics comprise at least one of resistance, capacitance and inductance. According to the equivalent circuit, the broadband equivalent load of the converter valve tower is subjected to frequency domain decoupling design, the equivalent load is decoupled into different circuits under different frequency bands for equivalence, the test cost can be reduced, and the broadband impedance characteristic of the converter valve under high-frequency impulse voltage can be simulated.

Description

Technical Field

[0001] This application relates to the field of high voltage direct current transmission technology, and more specifically, to an equivalent circuit of a converter valve tower, an insulation detection method for a converter valve, and an insulation detection system for a converter valve. Background Technology

[0002] Currently, converter valves consist of multiple valve towers, each containing multiple valve assemblies. When conducting multi-valve insulation tests on ultra-high voltage converter valves, the most direct method is to suspend all valve units (valve towers) for testing. This requires connecting all actual valve units (valve towers) according to their actual operating structure and connecting them together to the test circuit for testing.

[0003] In ultra-high voltage direct current (UHVDC) transmission projects, the multi-valve insulation test of controllable commutator valves is a crucial step in ensuring the safe and reliable operation of the equipment. However, traditional testing methods face key technical challenges such as extremely high testing costs, complex test circuits, huge footprints, and low testing efficiency. Summary of the Invention

[0004] The main objective of this application is to provide an equivalent circuit for a converter valve tower, an insulation detection method for a converter valve, and an insulation detection system for a converter valve, so as to at least solve the problems of high testing cost and low efficiency in the existing converter valve testing methods.

[0005] To achieve the above objectives, according to one aspect of this application, an equivalent circuit for a converter valve tower is provided, comprising: a plurality of parallel load branches, each load branch including an equivalent load, the equivalent loads included in different load branches being different, and the equivalent loads included in different load branches being used to equivalently represent the characteristics of the converter valve tower in different frequency bands; wherein the equivalent load is one of an equivalent resistive load, an equivalent capacitive load, and a composite equivalent load composed of inductance, resistance, and capacitance, wherein the characteristics of the converter valve tower operating in different frequency bands are different, and the characteristics include at least one of resistive, capacitive, and inductive.

[0006] Optionally, the plurality of load branches include a first load branch, the first load branch including: a first resistor module, a first end of the first resistor module being electrically connected to the positive terminal of the test voltage source, and a second end of the first resistor module being electrically connected to the negative terminal of the test voltage source.

[0007] Optionally, when the converter valve tower is a high-pressure valve tower, the resistance value of the first resistor module is a first preset multiple of the resistance value of the converter valve tower; when the converter valve tower is a low-pressure valve tower, the resistance value of the first resistor module is a second preset multiple of the resistance value of the converter valve tower, wherein the first preset multiple is greater than the second preset multiple.

[0008] Optionally, the converter valve tower includes at least one converter valve assembly, and the plurality of load branches include a second load branch, the second load branch including: an inductor equivalent unit, the first end of which is electrically connected to the first pole of the power supply, the resistance and inductance characteristics of which are the same as those of the saturated reactor of the converter valve; and a load equivalent unit, the first end of which is electrically connected to the second end of which is electrically connected to the second pole of the power supply, the resistance, capacitance, and inductance characteristics of which are the same as those of the converter valve assembly, and the converter valve assembly includes at least a fully controllable electronic device.

[0009] Optionally, the inductor equivalent unit includes: a second resistor module, the first end of which is electrically connected to the first pole of the power supply, and the second end of which is electrically connected to the load equivalent unit; and a first inductor, the first end of which is electrically connected to the first end of the second resistor module, and the second end of which is electrically connected to the second end of the second resistor module.

[0010] Optionally, the load equivalent unit includes an equivalent module of a parallel damping circuit, an equivalent module of a voltage equalization circuit, and an equivalent module of a parallel structure, wherein the parallel structure is a parallel structure composed of fully controlled electronic devices and surge arresters.

[0011] Optionally, the equivalent module of the damping circuit includes: a first capacitor, the first terminal of which is electrically connected to the second terminal of the inductor equivalent unit; and a third resistor module, the first terminal of which is electrically connected to the second terminal of the first capacitor, and the second terminal of which is electrically connected to the second terminal of the power supply.

[0012] Optionally, the equivalent module of the voltage equalization circuit includes: a fourth resistor module, the first end of which is electrically connected to the second end of the inductor equivalent unit, and the second end of which is electrically connected to the second pole of the power supply.

[0013] Optionally, the equivalent module of the parallel structure includes: a second inductor, the first end of which is electrically connected to the second end of the inductor equivalent unit; a second capacitor, the first terminal of which is electrically connected to the second end of the second inductor; and a fifth resistor module, the first end of which is electrically connected to the second terminal of the second capacitor, and the second end of which is electrically connected to the second terminal of the power supply.

[0014] Optionally, the plurality of load branches include a third load branch, the third load branch including: a third capacitor, the first terminal of the third capacitor being electrically connected to the positive terminal of the test voltage source, the second terminal of the third capacitor being electrically connected to the negative terminal of the test voltage source, and the capacitance value of the third capacitor being the same as the capacitance value of the distributed capacitance of the converter valve tower when it operates in the third frequency band.

[0015] According to another aspect of this application, an insulation testing method for a converter valve is provided, comprising: determining a test frequency band of the converter valve; determining a conducting branch of an equivalent circuit based on the test frequency band of the converter valve, wherein the equivalent circuit is an equivalent circuit of any of the converter valve towers described herein, and the conducting branch is at least one of a plurality of parallel load branches; inputting a corresponding test voltage to a target valve tower and the conducting branch based on the test frequency band of the converter valve to perform an insulation test on the converter valve, wherein the target valve tower is the valve tower with the highest potential among the converter valves.

[0016] Optionally, the plurality of load branches include a first load branch, a second load branch, and a third load branch. The first load branch includes a first resistor module, the first end of which is electrically connected to the positive terminal of the test voltage source, and the second end of which is electrically connected to the negative terminal of the test voltage source. The second load branch includes: a second resistor module, the first end of which is electrically connected to the first terminal of the power supply, and the second end of which is electrically connected to the load equivalent unit; a first inductor, the first end of which is electrically connected to the first terminal of the second resistor module, and the second end of which is electrically connected to the second terminal of the second resistor module; a first capacitor, the first terminal of which is electrically connected to the second terminal of the inductor equivalent unit; a third resistor module, the first end of which is electrically connected to the second terminal of the first capacitor, and the second end of which is electrically connected to the second terminal of the power supply; a fourth resistor module, the first end of which is electrically connected to the second terminal of the inductor equivalent unit, and the second end of which is electrically connected to the second terminal of the power supply; and a second inductor, the first end of which is electrically connected to the second terminal of the inductor equivalent unit. The second capacitor has its first terminal electrically connected to the second terminal of the second inductor; the fifth resistor module has its first terminal electrically connected to the second terminal of the second capacitor, and its second terminal electrically connected to the second terminal of the power supply; the third load branch includes: a third capacitor, the first terminal of which is electrically connected to the positive terminal of the test voltage source, and the second terminal of which is electrically connected to the negative terminal of the test voltage source. The capacitance value of the third capacitor is the same as the distributed capacitance value of the converter valve tower when it operates in the third frequency band, and is determined according to the test frequency band of the converter valve. The conducting branches of the equivalent circuit include: when the test frequency band is a first frequency band, determining the conducting branch of the equivalent circuit as the first load branch; when the test frequency band is a second frequency band, determining the conducting branches of the equivalent circuit as the first load branch and the second load branch, wherein the minimum value of the second frequency band is greater than the maximum value of the first frequency band; when the test frequency band is a third frequency band, determining the conducting branches of the equivalent circuit as the first load branch, the second load branch, and the third load branch, wherein the minimum value of the third frequency band is greater than the maximum value of the second frequency band.

[0017] Optionally, inputting a corresponding test voltage to the target valve tower and the conduction branch according to the test frequency band of the converter valve includes: when the test frequency band is a first frequency band, inputting a DC voltage to the target valve tower and the equivalent circuit; when the test frequency band is a second frequency band, inputting a first impulse voltage to the target valve tower and the equivalent circuit; and when the test frequency band is a third frequency band, inputting a second impulse voltage to the target valve tower and the equivalent circuit, wherein the bandwidth of the second impulse voltage is wider than that of the first impulse voltage.

[0018] According to another aspect of this application, an insulation detection system for a converter valve is provided, the converter valve including at least one valve tower, the insulation detection system comprising: a controller for executing any of the insulation detection methods for the converter valve described herein; and an equivalent circuit of any of the valve towers of the converter valve, electrically connected to the controller.

[0019] Applying the technical solution of this application, the equivalent circuit of the aforementioned converter valve tower includes: multiple parallel load branches, each load branch including an equivalent load, different load branches including different equivalent loads, and the equivalent loads included in different load branches are used to equivalently represent the characteristics of the converter valve tower in different frequency bands; the equivalent load is one of an equivalent resistive load, an equivalent capacitive load, and a composite equivalent load composed of inductance, resistance, and capacitance, wherein the characteristics of the converter valve tower are different when operating in different frequency bands, and the characteristics include at least one of resistive, capacitive, and inductive. This equivalent circuit employs frequency domain decoupling design for equivalent loads at different frequency bands. The converter valve exhibits resistive behavior under DC voltage, inductive behavior under operational shocks, and capacitive behavior under lightning and steep wave front shocks. Therefore, the equivalent load is modularly designed, and different circuits at different frequency bands are equivalent. This not only reduces testing costs but also eliminates the need to assemble the actual valve tower during testing. Only the equivalent circuit needs to be assembled, which is much simpler and easier than assembling the actual valve tower. This significantly reduces assembly time and improves assembly efficiency, solving the problems of high testing costs and low efficiency in existing converter valve testing methods. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 A schematic diagram of the equivalent circuit of a converter valve tower provided in an embodiment of this application is shown;

[0022] Figure 2A schematic diagram of the equivalent circuit of another converter valve tower provided according to an embodiment of this application is shown;

[0023] Figures 3(a)-3(b) show the equivalent principle schematic diagram of the first load branch provided according to the embodiments of this application;

[0024] Figure 4 A schematic diagram of a second load branch provided according to an embodiment of this application is shown;

[0025] Figure 5 A topological schematic diagram of a converter valve provided according to an embodiment of this application is shown;

[0026] Figures 6(a) and 6(b) show the equivalent principle schematic diagram of the second load branch provided according to the embodiments of this application;

[0027] Figures 7(a) and 7(b) show the equivalent principle schematic diagram of the third load branch provided according to the embodiments of this application;

[0028] Figure 8 A schematic diagram of the structure of an equivalent device for a converter valve tower according to an embodiment of this application is shown;

[0029] Figure 9 A schematic flowchart of an insulation testing method for a converter valve according to an embodiment of this application is shown.

[0030] Figure 10 A schematic diagram of the structure of an insulation detection system for a converter valve provided according to an embodiment of this application is shown.

[0031] The above figures include the following reference numerals:

[0032] 01. Load branch; 10. First load branch; 11. First resistor module; 20. Second load branch; 21. Inductor equivalent unit; 22. Load equivalent unit; 221. Equivalent module of damping circuit; 222. Equivalent module of voltage equalization circuit; 223. Equivalent module of parallel structure; 30. Third load branch; R1. Second resistor module; R2. Third resistor module; R3. Fourth resistor module; R4. Fifth resistor module; L1. First inductor; L2. Second inductor; C1. First capacitor; C2. Second capacitor; C3. Third capacitor; 100. Controller; 200. Equivalent circuit of converter valve tower. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] For ease of description, the following explains some of the nouns or terms used in the embodiments of this application:

[0037] Ultra-high voltage direct current (UHVDC) transmission;

[0038] Integrated Gate-Commutated Thyristor (IGCT): An IGCT is a power electronic device that combines the high power handling capability of a thyristor with the fast gate-controlled turn-off characteristics of an insulated-gate bipolar transistor (IGBT), making it suitable for high-voltage, high-power power conversion systems.

[0039] As described in the background section, the most direct method in current technology for conducting multi-valve insulation tests on UHV converter valves is to suspend all valve units (valve towers) for the test. This requires connecting all actual valve units (valve towers) according to their actual operating structure and connecting them together to the test circuit. The core drawback and problem of this method is:

[0040] 1. The number of test samples is huge and the cost is high. Using all real valve units for testing means that a large number of expensive equipment must be used as test samples, which greatly increases the testing cost (equipment procurement, maintenance, and wear and tear).

[0041] 2. The test circuit is complex and difficult to set up. Physically connecting multiple valve towers to form a test circuit requires complex mechanical structures, a large number of high-voltage connecting cables and supporting equipment. The circuit setup is very cumbersome, time-consuming and labor-intensive, and poses safety hazards.

[0042] 3. Huge demand for testing space. Multiple large valve towers and their auxiliary equipment require an extremely large testing hall space, placing stringent requirements on the area, height, and load-bearing capacity of the testing site. Constructing or leasing a dedicated site suitable for testing multiple valves under ultra-high voltage conditions is extremely costly.

[0043] 4. Low testing efficiency. Due to the complexity and time-consuming nature of sample preparation, circuit setup, and site coordination, the entire multi-valve insulation test has a long cycle and low efficiency, which restricts the research and development and iteration of new converter equipment.

[0044] 5. Lack of flexibility. Once the test circuit is set up, it is very difficult to replace or adjust the configuration of specific valve units for targeted testing.

[0045] To address the problems of high testing costs and low efficiency in existing converter valve testing methods, embodiments of this application provide an equivalent circuit of a converter valve tower, an insulation testing method for converter valves, and an insulation testing system for converter valves.

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0047] Figure 1 This is a schematic diagram of the equivalent circuit of the converter valve tower according to an embodiment of this application. Figure 1 As shown, the equivalent circuit includes: multiple parallel load branches 01, each of which includes an equivalent load. The equivalent loads included in different load branches 01 are different, and the equivalent loads included in different load branches 01 are used to represent the characteristics of the converter valve tower in different frequency bands. The equivalent load is one of the equivalent resistive load, the equivalent capacitive load, and a composite equivalent load composed of inductance, resistance, and capacitance. The characteristics of the converter valve tower when operating in different frequency bands are different, and the characteristics include at least one of resistive, capacitive, and inductive characteristics.

[0048] The converter valve tower is a converter valve structure that uses IGCTs as active shut-off devices. The converter valve structure using IGCTs as active shut-off devices is affected by the IGCT devices and surge arresters. Therefore, some existing common passive equivalent loads, i.e., simple combinations of resistors, inductors, and capacitors, are only suitable for low-to-medium frequency testing and cannot simulate the wide-band impedance characteristics of the converter valve under high-frequency impulse voltages. For active equivalent loads, although they can cover a wider frequency band, they are difficult to withstand voltages of 800kV and above and currents in the kiloampere range, and cannot accurately simulate the equivalent impedance distribution when multiple valves are connected in series. The frequency bands of converter valves are generally divided into low-frequency, mid-frequency, and high-frequency bands. Generally, at different frequency bands, the resistance, inductance, and capacitance elements inside the valve tower respond differently to current and voltage, causing the impedance characteristics of the entire circuit to change accordingly. By combining these components in a reasonable way and placing them in specific load branches, it can be ensured that the equivalent circuit exhibits similar electrical characteristics to the real valve tower within a specific frequency band.

[0049] The equivalent circuit described above in this application can accurately simulate the complex impedance characteristics, dynamic response, and energy absorption characteristics of the converter valve tower under wide frequency range during insulation tests (especially transient processes such as lightning impulse and steep wave front impulse), and is applicable to the multi-valve insulation test of UHV controllable commutation converter valve.

[0050] In ultra-high voltage direct current (UHVDC) transmission projects, the multi-valve insulation test of controllable commutation converter valves is a crucial step in ensuring the safe and reliable operation of the equipment. However, traditional testing methods suffer from significant technical challenges, including extremely high testing costs, complex test circuits, large footprints, and low testing efficiency. To address these challenges, this embodiment uses an equivalent load to replace some valve units in the equivalent circuit for testing, thereby significantly reducing the number of test samples. Furthermore, in the multi-valve insulation test, a low-cost equivalent load accurately simulates the wideband impedance characteristics of non-critical valve units. The aforementioned equivalent circuit can cover the entire spectrum (0~3MHz) of DC, power frequency, and impulse frequencies, with an equivalent impedance error of <5% under impulse waveforms, and its size and cost are far lower than those of converter valve towers.

[0051] The aforementioned equivalent circuit firstly abandons the active equivalent load scheme to circumvent the technical bottlenecks of high-voltage amplifiers, shifting towards passive network topology innovation. Secondly, it employs frequency-domain decoupling design for the wideband equivalent load. The converter valve exhibits resistive behavior under DC voltage, inductive behavior under operational shocks, and capacitive behavior under lightning and steep-wave frontal shocks. Therefore, the equivalent load is modularly designed, decoupled into different equivalent circuits for multiple frequency bands. For example: a distributed water-cooled resistor network equivalent in the low-frequency band, a valve unit topology network equivalent in the mid-frequency band, and a distributed stray capacitance network equivalent in the high-frequency band. Finally, a hierarchical structure design is implemented for the equivalent load device, using R, RL, RC, and RLC impedance networks for layered combination. Each layer of impedance network corresponds to different parts of the equivalent converter valve to respond to the impedance characteristics of multiple valve units in different frequency bands.

[0052] The equivalent circuit of the converter valve tower described in this application includes: multiple parallel load branches, each load branch including an equivalent load, the equivalent loads included in different load branches being different, and the equivalent loads included in different load branches being used to represent the characteristics of the converter valve tower in different frequency bands; the equivalent load is one of an equivalent resistive load, an equivalent capacitive load, and a composite equivalent load composed of inductance, resistance, and capacitance, wherein the characteristics of the converter valve tower are different when operating in different frequency bands, and the characteristics include at least one of resistive, capacitive, and inductive. This equivalent circuit employs frequency domain decoupling design for the wideband equivalent load. The converter valve exhibits resistive behavior under DC voltage, inductive behavior under operational shocks, and capacitive behavior under lightning and steep wave front shocks. Therefore, the equivalent load is modularly designed, eliminating the need to assemble the actual valve tower during testing. Only the equivalent circuit needs to be assembled, which is far simpler and easier than assembling the actual valve tower. This significantly reduces assembly time and improves assembly efficiency, solving the problems of high testing cost and low efficiency in existing converter valve testing methods.

[0053] In some embodiments, such as Figure 2 As shown, the plurality of load branches include a first load branch 10, the first load branch 10 including a first resistor module 11, the first end of the first resistor module 11 being electrically connected to the positive terminal of the test voltage source, and the second end of the first resistor module 11 being electrically connected to the negative terminal of the test voltage source.

[0054] The first load branch is the equivalent load circuit for the converter valve tower during low-frequency operation. When operating at low frequencies, the converter valve tower primarily exhibits resistive characteristics; therefore, the equivalent load needs to be equivalent to the distributed water-cooled resistor network of the multiple valve units. The first load branch simulates the resistive characteristics of the converter valve tower under DC and low-frequency conditions using a first resistor module. By directly connecting the first resistor module to the positive and negative terminals of the power supply, the first load branch 10 simplifies the setup of the test circuit. In traditional insulation tests, simulating the resistive characteristics of the valve tower requires connecting a real valve tower, which is complex and cumbersome. Using an equivalent circuit model, especially the design of the first load branch, can significantly reduce circuit setup work, saving time and cost. Using a resistor module instead of an actual valve tower for low-frequency and DC operation simulation significantly reduces test costs. Furthermore, since the voltage and current in the test circuit can be controlled by the resistor module, the safety risks associated with high voltage and high current are avoided.

[0055] Traditional methods estimate the water-cooling resistance based on the length, inner diameter, and conductivity of the water pipes, which deviates from the actual value. This embodiment, however, with a known controllable commutator valve structure design, allows for the creation of a geometric model of the valve tower in COMSOL, setting the model's parameters and boundary conditions, and calculating the equivalent resistance of each part of the valve tower's cooling water path through simulation. Compared to traditional methods, this approach accurately reproduces the actual water-cooling resistance network topology and improves the accuracy of water-cooling resistance calculations.

[0056] As shown in Figures 3(a) and 3(b), based on the electrical connections between the valve towers in actual operation, the water-cooling resistance of the valve tower can be further divided into the water-cooling resistance R of the valve support. W (R) W1 R W2 R W3 R W4 ) and the internal water-cooling resistance R of the valve M (R) M1 R M2 R M3 R M4 Valve bracket water-cooling resistor R W This refers to the resistance of the support at the top of the valve tower. The valve tower with the highest potential, connected to the positive terminal of the test voltage source, is connected from the bottom. Therefore, the water-cooled resistance R of the valve support of the valve tower with the highest potential is... W and the internal water-cooling resistance R of the valve M In series. Other valve towers have their valve support tops grounded, therefore the valve support water-cooling resistance R... W and the internal water-cooling resistance R of the valve M There is a parallel relationship.

[0057] In the DC withstand voltage test of a multi-valve unit, the voltage distribution of the multi-valve unit is mainly determined by the equivalent resistance network.

[0058] This embodiment can determine the DC resistance parameters of the equivalent load based on the equivalent resistance network when conducting a multi-valve insulation test with all valve towers suspended, which can more accurately restore the DC voltage distribution characteristics in the multi-valve insulation test. Therefore, as shown in Figures 3(a) and 3(b), the equivalent resistance network when conducting an insulation test with all valve units suspended can be given first, i.e., Figures 3(a) and 3(b). Then, it can be compared with the equivalent resistance network when conducting an insulation test using a potentiometer valve and an equivalent load. Then, the resistance network corresponding to the equivalent load can be obtained, and the resistance parameters of the equivalent load in the DC withstand voltage test of the valve tower under high voltage (hereinafter referred to as the high-end valve) and the valve tower under low voltage (hereinafter referred to as the low-end valve) can be calculated.

[0059] The valve hall contains four valve towers. When the voltage range is 800kV to 400kV, all four valve towers need to be connected. When the voltage range is 400kV to 0kV, only two valve towers need to be connected. When testing the high-end valves (voltage range 800kV to 400kV), the second, third, and fourth valve towers need to be connected for testing, while the first valve tower (the one connected to the negative terminal of the test voltage source) is bypassed. When testing the low-end valves (voltage range 400kV to 0kV), half of the first valve tower (the one connected to the negative terminal of the test voltage source) and the second valve tower need to be connected for testing.

[0060] In some embodiments, when the converter valve tower is a high-pressure valve tower, the resistance value of the first resistor module is a first preset multiple of the resistance value of the converter valve tower; when the converter valve tower is a low-pressure valve tower, the resistance value of the first resistor module is a second preset multiple of the resistance value of the converter valve tower, wherein the first preset multiple is greater than the second preset multiple.

[0061] Since more valve towers are connected in the high-pressure range, a larger equivalent resistance value is required, while fewer valve towers are connected in the low-pressure range, and a smaller equivalent resistance value is required. Therefore, the first preset multiple is generally greater than the aforementioned second preset multiple. Because the resistive characteristics of high-pressure and low-pressure valve towers differ significantly in numerical value, by setting the resistance value of the first resistor module to a first preset multiple of the high-pressure valve tower resistance and a second preset multiple of the low-pressure valve tower resistance, it can be ensured that the equivalent circuit model can accurately simulate the resistive characteristics of the actual valve tower at different voltage levels. The above design allows for flexible adjustment of the resistance value of the first resistor module according to the specific voltage level of the valve tower under test, thus enabling the equivalent circuit model to adapt to the testing of different types of converter valves.

[0062] As shown in Figure 3(a), the valve towers are high-end valves. From the side connected to the negative terminal of the test voltage source to the side connected to the positive terminal, they are the first valve tower, the second valve tower, the third valve tower, and the fourth valve tower, respectively. When testing the high-end valves, the first valve tower is bypassed, and the second, third, and fourth valve towers are connected for testing. However, the fourth valve tower needs to be tested using a real valve tower; therefore, only the second and third valve towers are equivalently tested. That is, the circuit includes the internal water-cooling resistor R of the second valve tower. M2 The water-cooled resistor R of the valve support of the third valve tower W3 and the internal water-cooling resistance R of the valve M3 The water-cooled resistor R of the valve support of the fourth valve tower W4 and the internal water-cooling resistance R of the valve M4 The portion in box A of Figure 3(a) is the equivalent portion of the first load branch.

[0063] As shown in Figure 3(b), the valve tower is a low-end valve. From the side connected to the negative terminal of the test voltage source to the side connected to the positive terminal of the test voltage source, there are the first valve tower and the second valve tower, respectively. When testing the low-end valve, half of the first valve tower and the second valve tower are connected for testing. However, the second valve tower needs to be tested using a real valve tower, so only half of the first valve tower is equivalently tested. That is, the circuit includes the internal water-cooling resistance 1 / 2R of half of the first valve tower. M1 Water-cooled resistor R of valve bracket W1 The water-cooled resistor R of the valve support of the second valve tower W2 and the internal water-cooling resistance R of the valve M2 Similarly, it can be concluded that the part in box B in Figure 3(b) is the equivalent part of the first load branch.

[0064] In this case, the water-cooled resistance of the valve support and the water-cooled resistance inside the valve are the same for all valve towers, so the resistance value can be calculated directly.

[0065] In some embodiments, such as Figure 2 and Figure 4As shown, the aforementioned converter valve tower includes at least one converter valve assembly, and the plurality of aforementioned load branches include a second load branch 20. The second load branch 20 includes: an inductance equivalent unit 21, the first end of which is electrically connected to the first pole of the power supply, and the resistance and inductance characteristics of the inductance equivalent unit 21 are the same as those of the saturated reactor of the converter valve; and a load equivalent unit 22, the first end of which is electrically connected to the second end of the inductance equivalent unit 21, and the second end of which is electrically connected to the second pole of the power supply. The first pole and the second pole of the power supply are, respectively, positive and negative. The resistance, capacitance, and inductance characteristics of the load equivalent unit 22 are the same as those of the converter valve assembly. The converter valve assembly includes at least a fully controllable electronic device.

[0066] The second load branch is the equivalent load circuit for the converter valve tower during mid-frequency operation. Since the controllable commutation converter valve uses a saturated reactor, the valve unit primarily exhibits inductive characteristics in the mid-frequency range. The resistance and inductance characteristics of the inductive equivalent unit are identical to those of the saturated reactor in the converter valve, meaning it can accurately replicate the behavior of the saturated reactor in the mid-frequency range. Saturated reactors play a crucial role in this type of power equipment, especially in their inductive response under operating impulse voltages. By using this equivalent circuit, the simulation of the saturated reactor characteristics in the experiment can be ensured to achieve extremely high accuracy. The load equivalent unit 22 includes not only resistance characteristics but also capacitance and inductance characteristics, reflecting the complex impedance behavior of the converter valve components (including but not limited to fully controlled electronic devices) over a wide frequency band. This design can better simulate the real response of the converter valve at different frequencies, ensuring that the experimental results are more consistent with actual operating conditions.

[0067] Furthermore, compared to testing with actual saturated reactors and converter valve assemblies, the circuit design of the second load branch simplifies the test loop and reduces the need for high-cost equipment such as large inductors and complex power electronics. This not only lowers testing costs but also improves testing convenience and shortens setup and commissioning time. Using an equivalent circuit model for testing, especially when simulating the behavior of a saturated reactor, significantly improves the safety of the testing process, avoiding the risks associated with operating actual equipment under high voltage and current conditions. In addition, since the parameters of the equivalent circuit can be adjusted according to testing requirements, this design also enhances the flexibility of the test, allowing testers to quickly adapt and adjust to different testing scenarios.

[0068] like Figure 5 As shown, a converter valve assembly consists of an IGCT device and a resistor R. s Capacitor C s Resistance Rd Inductor L s It consists of a surge arrester (MOV). Figure 5 The diagram shows a multi-stage converter valve assembly, specifically the first-stage converter valve assembly, which consists of an IGCT1 device and a resistor R. s1 Capacitor C s1 Resistance R d1 Inductor L s1 The surge arrester MOV1, ..., the nth stage converter valve assembly is composed of IGCT. n Devices, resistor R sn Capacitor C sn Resistance R dn Inductor L sn and surge arrester MOV n composition.

[0069] In some embodiments, such as Figure 2 and Figure 4 As shown, the inductor equivalent unit 21 includes: a second resistor module R1, the first end of which is electrically connected to the first pole of the power supply, and the second end of which is electrically connected to the load equivalent unit 22; and a first inductor L1, the first end of which is electrically connected to the first end of the second resistor module R1, and the second end of which is electrically connected to the second end of the second resistor module R1.

[0070] in, Figure 5 This is a real electrical topology diagram of a converter valve. (Example:) Figure 2 and Figure 5 As shown, saturated reactor L m It exhibits magnetic saturation characteristics; the inductance value decreases when the current reaches a certain value. Specifically, the second resistor module R1 and the first inductor L1 are saturated reactors L... m The equivalent circuit.

[0071] Saturated reactors play a crucial role in converter valves by limiting the rate of current rise and suppressing harmonics. The inductive equivalent unit, through the combination of a second resistor module R1 and a first inductor L1, can accurately reproduce the resistive and inductive characteristics of the saturated reactor during dynamic processes. This allows the test circuit to more realistically reflect the electrical response of the converter valve under dynamic conditions such as operational shocks. In high-voltage direct current transmission systems, dynamic events such as operational shocks have a significant impact on the performance and safety of converter valves. By precisely controlling the parameters of the inductive equivalent unit, the test circuit can effectively simulate the converter valve's response to these dynamic events, thereby enabling more in-depth testing and evaluation of the converter valve's dynamic performance. Using the low-cost second resistor module R1 and first inductor L1 instead of expensive saturated reactors can significantly reduce testing costs. Simultaneously, the relatively simple structure of the inductive equivalent unit reduces the complexity of the test circuit, facilitates rapid setup and adjustment, and improves testing efficiency.

[0072] In some embodiments, such as Figure 2 and Figure 4 As shown, the load equivalent unit 22 includes an equivalent module 221 of a parallel damping circuit, an equivalent module 222 of a voltage equalization circuit, and an equivalent module 223 of a parallel structure. The parallel structure is a parallel structure composed of fully controlled electronic devices and surge arresters.

[0073] Because the controllable commutator valve uses a saturated reactor, the valve unit primarily exhibits inductive characteristics in the mid-frequency range. The operating impulse voltage during insulation testing corresponds to this frequency range, and the equivalent load topology can be designed based on the valve assembly's topology network. To improve the equivalence of the equivalent load, each branch in the valve assembly circuit topology is equivalently represented, including the equivalent branch of the saturated reactor, the equivalent module of the damping circuit, the equivalent module of the voltage equalization circuit, and the equivalent module of the parallel structure. The electrical parameters of each component in the equivalent load topology can be determined by the design values ​​of the electrical parameters of each component of the controllable commutator valve and the measurement results of its broadband impedance characteristics.

[0074] By designing equivalent branches to simulate the damping circuit (used to absorb resonant energy generated during switching operations), the voltage equalization circuit (used to ensure balanced voltage distribution across the converter valve), and the parallel structure of IGCT devices and surge arresters (used to protect devices from overvoltage damage), the load equivalent unit can comprehensively and accurately reproduce the electrical behavior of the converter valve in the mid- and high-frequency ranges. This refined simulation capability helps to more accurately evaluate the actual operating performance and insulation level of the converter valve. The equivalent module design of the damping circuit and voltage equalization circuit ensures that the dynamic balance mechanism inside the converter valve can be effectively captured and restored when simulating dynamic conditions such as operating impulse voltages. The simulation of the parallel structure of IGCT devices and surge arresters further enhances the testing of the converter valve's protection mechanism and improves the reliability of the test results. Real IGCT devices and surge arresters pose significant safety risks when tested under high voltage and high current conditions. The design of the load equivalent unit allows for the use of low-cost and safer equivalent components for alternative testing, reducing safety risks during testing and protecting test personnel and equipment.

[0075] In some embodiments, such as Figure 2 and Figure 4 As shown, the equivalent module 221 of the damping circuit includes: a first capacitor C1, the first terminal of the first capacitor C1 being electrically connected to the second terminal of the inductor equivalent unit 21; and a third resistor module R2, the first terminal of the third resistor module R2 being electrically connected to the second terminal of the first capacitor C1, and the second terminal of the third resistor module R2 being electrically connected to the second terminal of the power supply.

[0076] in, Figure 5 This is a real electrical topology diagram of a converter valve. (Example:) Figure 2 and Figure 5 As shown, taking the first-stage converter valve as an example, the damping circuit is as follows: Figure 5 Chinese R s1 and C s1 The branch roads formed Figure 2 The branch consisting of the first capacitor C1 and the third resistor module R2 is Figure 5 Chinese R s1 and C s1 The equivalent circuit of the branch.

[0077] The damping circuit plays a crucial role in absorbing and attenuating the resonant energy generated during switching operations in converter valves. The equivalent branch consisting of the first capacitor C1 and the third resistor module R2 accurately reproduces the capacitive and resistive responses of the damping circuit under operational shocks, ensuring that the test circuit truly reflects the electrical behavior of the converter valve after switching operations. In dynamic testing of converter valves, especially in operational impulse voltage testing, the first capacitor C1 stores and releases charge, while the third resistor module R2 dissipates this energy, thereby stabilizing the voltage and current waveforms of the test circuit and preventing voltage overshoot and current oscillations caused by resonance effects, thus improving the stability and reliability of the testing process. By using the equivalent branch of the first capacitor C1 and the third resistor module R2, the direct use of high-capacity capacitors and high-power resistors can be avoided in the test, reducing the losses and safety risks of real devices under high-voltage testing environments, and protecting test equipment and personnel. The values ​​of the first capacitor C1 and the third resistor module R2 can be adjusted according to test requirements, providing testers with greater flexibility. The equivalent characteristics of the damping circuit can be optimized according to different test conditions and objectives to adapt to different types of converter valves and different impulse voltage levels.

[0078] In some embodiments, such as Figure 2 and Figure 4 As shown, the equivalent module 222 of the voltage equalization circuit includes: a fourth resistor module R3, the first end of the fourth resistor module R3 being electrically connected to the second end of the inductor equivalent unit 21, and the second end of the fourth resistor module R3 being electrically connected to the second pole of the power supply.

[0079] in, Figure 5 This is a real electrical topology diagram of a converter valve. (Example:) Figure 2 and Figure 5 As shown, taking the first-stage converter valve as an example, the pressure equalization circuit is as follows: Figure 5 Chinese R d1 The side road where it is located Figure 2 The fourth resistor module R3 is Figure 5 Chinese R d1 The equivalent resistance.

[0080] Specifically, the design of the fourth resistor module R3 effectively mimics the resistive characteristics of the converter valve's voltage equalization circuit. This ensures that during testing, especially under conditions such as operating impulse voltages or lightning strikes, the voltage distribution in the test circuit is similar to the voltage distribution during actual operation of the converter valve, thus verifying the voltage equalization effect of the converter valve under these conditions. By adjusting the parameters of the fourth resistor module R3, its electrical characteristics can be highly matched with the resistive characteristics of the actual voltage equalization circuit of the converter valve, guaranteeing voltage balance among the components of the converter valve under test conditions. This is beneficial for accurately evaluating the dynamic performance and insulation level of the converter valve. In traditional tests, simulating the voltage equalization circuit requires a complex multi-component circuit, including multiple resistors and other passive components. The design of the fourth resistor module R3 simplifies the test circuit, reduces the complexity of building and maintaining the test system, and saves costs and resources.

[0081] In some embodiments, such as Figure 2 and Figure 4 As shown, the equivalent module 223 of the above parallel structure includes: a second inductor L2, the first end of which is electrically connected to the second end of the inductor equivalent unit 21; a second capacitor C2, the first terminal of which is electrically connected to the second end of the second inductor L2; and a fifth resistor module R4, the first end of which is electrically connected to the second terminal of the second capacitor C2, and the second end of which is electrically connected to the second terminal of the power supply.

[0082] The combination of the second inductor L2, the second capacitor C2, and the fifth resistor module R4 can accurately reproduce the wideband electrical characteristics of the IGCT device and the surge arrester connected in parallel. The inductive behavior of the IGCT device is simulated by the second inductor L2, while the capacitive characteristics of the surge arrester are reflected by the second capacitor C2. The fifth resistor module R4 is used to simulate the resistive part of the IGCT device. This combination design enables the test circuit to accurately simulate the dynamic response of the device in the actual converter valve.

[0083] in, Figure 5 This is a real electrical topology diagram of a converter valve. (Example:) Figure 2 and Figure 5 As shown, taking the first-stage converter valve as an example, the device refers to... Figure 5 The IGCT1 device in the middle is a surge arrester. Figure 5 MOV1, L s1 For inductance, Figure 2 The branch consisting of the second inductor L2, the second capacitor C2, and the fifth resistor module R4 is Figure 5 IGCT1, MOV1 and L s1The equivalent circuit of the branch is shown. The surge arrester plays a crucial overvoltage protection role in the converter valve. The parallel design of the second capacitor C2 effectively absorbs and disperses lightning strikes or steep-front surge voltages, protecting other sensitive components in the test circuit from overvoltage damage, while ensuring the stability and safety of the test process. By using an equivalent branch composed of low-cost components such as the second inductor L2, the second capacitor C2, and the fifth resistor module R4, the actual IGCT device and surge arrester are replaced, significantly reducing test costs. Simultaneously, this design simplifies the complexity of the test circuit, reduces test preparation and setup time, and improves test efficiency. The combined design of the second inductor L2 and the second capacitor C2 enhances the dynamic response capability of the test circuit in the high-frequency range, more accurately simulating the impedance characteristics of the converter valve under high-frequency surges, and improving the accuracy and reliability of the test results.

[0084] In addition, when the converter valve assembly has multiple stages, Figure 2 The first capacitor C1 and the third resistor module R2 are used to equivalently represent R in all converter valve assemblies. s and C s The fourth resistor module R3 is used to equivalently measure the resistor R in all the converter valve components. d The second inductor L2, the second capacitor C2, and the fifth resistor module R4 are used to equivalently power all the IGCT, MOV, and L in the converter valve assembly. s .

[0085] As shown in Figures 6(a) and 6(b), Figure 6(a) shows the equivalent circuit for the operational impact test of the high-end valve. During the test, the high-end valve needs to be connected to three valve towers. However, the high-end valve tower with the highest potential does not need to be equivalent and can be directly connected; that is, only the two valve towers with lower potentials are equivalent. As shown in Figure 6(a), MUV4 is the converter valve assembly structure for the high-end valve tower that does not require equivalence, representing the actual converter valve assembly structure of the valve tower. MUV3 and MUV2 are the other two high-end valve towers that require equivalence.

[0086] As shown in Figure 6(a), from the side connected to the negative terminal of the test voltage source to the side connected to the positive terminal of the test voltage source, are the first valve tower, the second valve tower, the third valve tower, and the fourth valve tower, respectively. When testing the high-side valve, the first valve tower is bypassed, and the second, third, and fourth valve towers are connected for testing. However, the fourth valve tower needs to be tested using a real valve tower, so only the second and third valve towers are equivalent. That is, the fourth valve tower adopts the real structure, and MVU4 is the converter valve assembly structure of the fourth valve tower. The part in box C in Figure 6(a) is the equivalent part of the second load branch, that is, the converter valve assembly structure MVU2 of the second valve tower and the converter valve assembly structure MVU3 of the third valve tower need to be equivalent.

[0087] As shown in Figures 6(a) and 6(b), Figure 6(b) shows the equivalent circuit for the operational impact test of the low-end valve. The low-end valve requires connection to 1.5 valve towers during testing. The valve tower with the highest potential in the low-end valve does not need to be equivalent and can be directly connected; that is, only the half of the valve tower with the lower potential is equivalent. As shown in Figure 6(b), from the side connected to the negative terminal of the test voltage source to the side connected to the positive terminal of the test voltage source, are the first valve tower and the second valve tower, respectively. When testing the low-end valve, half of the first valve tower and the second valve tower are connected for testing. The second valve tower needs to be tested using a real valve tower; therefore, only half of the first valve tower is equivalent. That is, the circuit includes the parameters of the converter valve assembly structure of half of the first valve tower and the converter valve assembly structure of the second valve tower. Similarly, the part in box D in Figure 6(b) is the equivalent part of the second load branch, which requires equivalent half of the converter valve assembly structure MVU1 of the first valve tower.

[0088] In some embodiments, such as Figure 2 As shown, the multiple load branches mentioned above include a third load branch 30, which includes a third capacitor C3. The first terminal of the third capacitor C3 is electrically connected to the positive terminal of the test voltage source, and the second terminal of the third capacitor C3 is electrically connected to the negative terminal of the test voltage source. The capacitance value of the third capacitor C3 is the same as the capacitance value of the distributed capacitance of the converter valve tower when it operates in the third frequency band.

[0089] The capacitance value of the third capacitor C3 matches the distributed capacitance value of the converter valve tower during high-frequency operation, ensuring that the test circuit can accurately simulate the electrical characteristics of the actual converter valve under high-frequency impacts, including lightning strikes and steep-front impacts. Inside the converter valve, the distributed capacitance plays a crucial role in the distribution of high-frequency voltage and energy absorption. The accurate simulation of the third capacitor C3 allows the test circuit to realistically reflect the high-frequency response inside the converter valve, helping to verify the rationality of the converter valve design and optimize the valve tower structure. Using the third capacitor C3 to replace the high-frequency distributed capacitance in the actual converter valve tower avoids the high cost and complexity of suspending the entire valve tower during testing, while reducing the demand for test sites and auxiliary equipment, achieving both economic efficiency and high performance. The capacitance value of the third capacitor C3 can be adjusted according to different test objectives, providing greater flexibility for testers and enabling more comprehensive performance testing, including responses at different frequencies and voltage levels.

[0090] Due to the large size and high integration of the controllable commutator valve, its stray capacitance to ground is relatively large, exhibiting mainly capacitive characteristics at high frequencies. Therefore, the equivalent load needs to be equivalent to the distributed stray capacitance network of the multiple valve units. Given the structural design of the controllable commutator valve, a geometric model of the valve tower can be built in ANSYS Q3D, and the model parameters and boundary conditions can be set. The stray capacitance of the valve tower can then be calculated through electromagnetic field simulation.

[0091] The stray capacitance of a valve tower can be categorized into the capacitance between the shield and ground, the capacitance between the shield and valve modules, the capacitance between valve modules and ground, and the capacitance between valve modules. Based on the internal electrical connections and stray capacitance distribution of the valve tower, an equivalent circuit model of the valve tower at high frequencies can be obtained. In lightning impulse and steep-wave front impulse tests on multiple valve units, the voltage distribution of the multiple valve units is mainly determined by the stray capacitance network. Therefore, the stray capacitance network when suspending all valve units for insulation testing can be given first, and then compared with the stray capacitance network when using potentiometric valves and equivalent loads for insulation testing. The stray capacitance network corresponding to the equivalent load can then be obtained, and the capacitance parameters of the equivalent load in the impulse withstand voltage tests of the high-end and low-end valves can be calculated.

[0092] As shown in Figure 7(a), the valve towers are high-side valves. From the side connected to the negative terminal of the test voltage source to the side connected to the positive terminal of the test voltage source, they are the first valve tower, the second valve tower, the third valve tower, and the fourth valve tower, respectively. When testing the high-side valves, the first valve tower is bypassed, and the second, third, and fourth valve towers are connected for testing. However, the fourth valve tower needs to be tested using a real valve tower; therefore, only the second and third valve towers are equivalently tested. That is, the circuit includes the distributed capacitance C of the second valve tower. M2 The distributed capacitance C of the third valve tower M3 The distributed capacitance C of the fourth valve tower M4 And the capacitance to ground C0. The part in box E in Figure 7(a) is the equivalent part of the third load branch.

[0093] As shown in Figure 7(b), the valve tower is a low-end valve. From the side connected to the negative terminal of the test voltage source to the side connected to the positive terminal, there are the first valve tower and the second valve tower, respectively. When testing the low-end valve, half of the first valve tower and the second valve tower are connected for testing, while the second valve tower needs to be tested using a real valve tower. That is, the circuit includes the distributed capacitance C of the connected half of the first valve tower. M1 The distributed capacitance C of the second valve tower M2 Similarly, it can be concluded that the part in box F in Figure 7(b) is the equivalent part of the third load branch.

[0094] The above equivalent circuit performs frequency domain decoupling design on the wideband equivalent load of the controllable commutator valve, and introduces the design methods of the topology and electrical parameters of the equivalent load modules in the low-frequency, mid-frequency and high-frequency bands respectively. By connecting the equivalent load modules of each frequency band in parallel in the topology, the topology of the wideband equivalent load of the controllable commutator valve can be obtained.

[0095] Furthermore, temperature changes directly affect the dielectric constant and loss tangent of insulating materials. High temperatures reduce dielectric strength, while low temperatures may increase the brittleness of the material, thus affecting insulation performance. Rising temperatures also increase contact resistance at electrical connection points, reducing heat dissipation efficiency and further exacerbating the temperature rise, creating a vicious cycle.

[0096] In high-temperature environments, the dielectric constant and loss tangent of the insulating medium increase, necessitating larger values ​​for the capacitor elements in the equivalent circuit to simulate the capacitive characteristics of the converter valve after temperature rise. Simultaneously, considering the effect of temperature on resistance, the parameters of the resistive elements in the equivalent circuit also need appropriate correction to reflect the resistance changes caused by temperature variations. Therefore, the above method also includes the following steps:

[0097] The ambient temperature of the valve tower is monitored in real time, and the corresponding preset temperature threshold is determined according to the test frequency band of the aforementioned converter valve tower.

[0098] When the ambient temperature is greater than the preset temperature threshold, the difference between the ambient temperature and the preset temperature threshold is determined as the temperature difference.

[0099] Based on the above temperature difference, determine the capacitance correction amount of the capacitor element and / or the resistance correction amount of the resistor element in the corresponding equivalent circuit.

[0100] The capacitance value of the capacitor element in the equivalent circuit is adjusted by using the capacitance correction amount of the capacitor element to obtain the adjusted capacitance, and / or the resistance value of the resistor element in the equivalent circuit is adjusted by using the resistance correction amount of the resistor element to obtain the adjusted resistance.

[0101] This involves real-time monitoring of the ambient temperature of the valve tower. When the ambient temperature exceeds a preset value, a temperature compensation mechanism is introduced. A temperature sensor monitors the test environment, and the equivalent circuit parameters are adjusted in real time to ensure the consistency and accuracy of test results under different temperature conditions. For example, a PT100 temperature sensor is used to monitor the temperature, and then the correction amounts for the resistance and capacitance in the equivalent circuit are calculated based on the temperature change formula. These calculated correction amounts are then used to compensate for the resistance and capacitance, ensuring the accuracy of the insulation test.

[0102] Based on the proposed broadband equivalent load topology, the structure of the equivalent load device was further designed, such as... Figure 8As shown, the equivalent load device mainly consists of a shielding cover, an air cushion base, a low-frequency module, a mid-frequency module, and a high-frequency module. The resistors, capacitors, and inductors in each module have multiple sets of selectable and adjustable parameters. The equivalent load device adopts a layered design principle: the DC resistance of the low-frequency module serves as one layer for the water-cooled resistance network of the equivalent multi-valve unit; the mid-frequency module is divided into three layers, each used for the saturated reactor, damping branch, devices, and surge arrester branch in the equivalent multi-valve unit's electrical topology; and the capacitors of the high-frequency module serve as one layer for the stray capacitance network of the equivalent multi-valve unit.

[0103] Embodiments of this application also provide an insulation detection method for a converter valve, such as... Figure 9 As shown, the above method includes the following steps:

[0104] Step S101: Determine the test frequency band for the converter valve;

[0105] Step S102: Determine the conducting branch of the equivalent circuit according to the test frequency band of the converter valve. The equivalent circuit is any of the above-mentioned converter valve towers. The conducting branch is at least one of multiple parallel load branches.

[0106] Step S103: According to the test frequency band of the converter valve, the corresponding test voltage is input to the target valve tower and the conduction circuit to perform insulation test on the converter valve. The target valve tower is the valve tower with the highest potential among the converter valves.

[0107] The selection of the test frequency band is based on the electrical environment that the converter valve may face under actual operating conditions, including the electrical characteristics at various frequencies such as DC, power frequency, lightning impulse, and steep wave front impulse. This ensures that the insulation test can cover all critical frequency bands of the converter valve's operation, improving the comprehensiveness and specificity of the testing.

[0108] The insulation testing method for converter valves described in this application determines the conducting branch of the equivalent circuit based on the test frequency band. This means that at different frequency bands, the equivalent circuit will automatically or manually adjust the connection state of its internal components to activate the electrical characteristic simulation branch corresponding to that frequency band. This avoids unnecessary interference from components during the test, ensuring the accuracy and effectiveness of the insulation test. Since the equivalent circuit can adjust its internal connections according to different test frequency bands, this method allows the testing system to adapt to various types of converter valves and simulate electrical environments under various operating conditions. This not only enhances the adaptability of the testing system but also improves the comparability and reliability of the test results. Using an equivalent circuit instead of the actual valve tower for insulation testing reduces the number of high-voltage devices in the test circuit, reduces the risk of the test sample being directly exposed to high voltage, and thus reduces potential safety hazards during the testing process.

[0109] In some embodiments, the first load branch includes a first resistor module, a first terminal of which is electrically connected to the positive terminal of the test voltage source, and a second terminal of which is electrically connected to the negative terminal of the test voltage source. The second load branch includes: a second resistor module, the first terminal of which is electrically connected to the first terminal of the power supply, and the second terminal of which is electrically connected to the load equivalent unit; a first inductor, the first terminal of which is electrically connected to the first terminal of the second resistor module, and the second terminal of which is electrically connected to the second terminal of the second resistor module; a first capacitor, the first terminal of which is electrically connected to the second terminal of the inductor equivalent unit; a third resistor module, the first terminal of which is electrically connected to the second terminal of the first capacitor, and the second terminal of which is electrically connected to the second terminal of the power supply; and a fourth resistor module, the first terminal of which is electrically connected to the inductor... The second terminal of the equivalent unit is electrically connected, and the second terminal of the fourth resistor module is electrically connected to the second pole of the power supply; the first terminal of the second inductor is electrically connected to the second terminal of the inductor equivalent unit; the first pole of the second capacitor is electrically connected to the second terminal of the second inductor; the first terminal of the fifth resistor module is electrically connected to the second pole of the second capacitor, and the second terminal of the fifth resistor module is electrically connected to the second pole of the power supply; the third load branch includes: a third capacitor, the first pole of the third capacitor is electrically connected to the positive pole of the test voltage source, and the second pole of the third capacitor is electrically connected to the negative pole of the test voltage source. The capacitance value of the third capacitor is the same as the capacitance value of the distributed capacitance of the converter valve tower when it operates in the third frequency band. The multiple load branches include a first load branch, a second load branch, and a third load branch. Determining the conducting branch of the equivalent circuit according to the test frequency band of the converter valve includes the following steps:

[0110] Step S1021: When the test frequency band is the first frequency band, determine that the conducting branch of the equivalent circuit is the first load branch.

[0111] Step S1022: When the test frequency band is the second frequency band, the conducting branch of the equivalent circuit is determined to be the first load branch and the second load branch, and the minimum value of the second frequency band is greater than the maximum value of the first frequency band.

[0112] Step S1023: When the test frequency band is the third frequency band, the conducting branches of the equivalent circuit are determined to be the first load branch, the second load branch and the third load branch, and the minimum value of the third frequency band is greater than the maximum value of the second frequency band.

[0113] The first frequency band corresponds to low-frequency characteristics, the second frequency band covers the mid-frequency band, and the third frequency band covers the high-frequency band. By selecting different load branches for conduction, it is possible to ensure that the input of the test voltage source and the electrical characteristics of the converter valve are precisely matched in different frequency bands, thereby improving the accuracy of insulation testing. This frequency band division and load branch matching strategy ensures that the test circuit can accurately reproduce the electrical behavior of the converter valve in DC, power frequency, and lightning impulse and steep wave front impulse frequency bands. The design of the first, second, and third load branches covers a wide frequency band from low to high frequencies. This design can adapt to various testing requirements of converter valves in high-voltage direct current transmission systems, ensuring that the insulation performance and dynamic response of the converter valve can be comprehensively evaluated in different frequency bands.

[0114] In some embodiments, a corresponding test voltage is input to the target valve tower and the equivalent circuit according to the test frequency band of the aforementioned converter valve to perform an insulation test on the converter valve, including the following steps:

[0115] Step S1031: When the test frequency band is the first frequency band, the DC voltage is input to the target valve tower and the conduction branch.

[0116] Step S1032: When the test frequency band is the second frequency band, the first impulse voltage is input to the target valve tower and the equivalent circuit.

[0117] In step S1033, when the test frequency band is the third frequency band, the second impulse voltage is input to the target valve tower and the equivalent circuit, and the bandwidth of the second impulse voltage is wider than that of the first impulse voltage.

[0118] The first impulse voltage is the switching impulse voltage, typically with a wavefront time of 250 microseconds. The second impulse voltage is either a lightning impulse voltage or a steep wave impulse voltage. The wavefront time of a lightning impulse voltage is typically 1.2 microseconds, while that of a steep wave impulse voltage is typically 0.2 microseconds. A shorter wavefront time results in a wider frequency band. The wavefront time is the time it takes for the wave amplitude to rise from 10% to 90%.

[0119] The DC voltage test in the first frequency band, the first impulse voltage test in the second frequency band, and the second impulse voltage test in the third frequency band ensure that the insulation performance is fully evaluated across the entire frequency range from low to high frequencies. This full-band test coverage is the foundation for maintaining the reliability of the converter valve under complex operating environments. The DC voltage test is suitable for evaluating the insulation performance of the converter valve under continuous voltage; the first impulse voltage test, such as the operating impulse, is used to detect the dynamic response and energy absorption capacity in the mid-frequency range; the second impulse voltage test, such as the lightning impulse or steep wave front impulse, focuses on the converter valve's response to high-frequency impulses. This test design ensures that each test targets the key characteristics of the converter valve under specific operating conditions. The input of different types of test voltages makes the test results clearer and more specific, facilitating the analysis of the insulation status of the converter valve in different frequency bands. Using DC voltage, first impulse voltage, and second impulse voltage for testing avoids the use of a full-size actual valve tower, reduces the number of equipment and space required for testing, and effectively controls testing costs.

[0120] Specifically, the insulation test begins with wiring: connecting the equivalent load and the test valve (i.e., the target valve tower) in series, and then connecting the test valve (target valve tower) and the equivalent load together in parallel with the impulse power supply. Next, based on the parameters and structural design of the test valve, the parameters for the equivalent load test are determined, and the internal components of the equivalent load are connected accordingly. Then, DC, AC, switching, lightning, and steep wave front impulse withstand voltage tests are conducted, measuring the test voltages on the test valve and the equivalent load. Finally, the voltage divider characteristics and insulation characteristics of the test valve and the equivalent load are checked to ensure they meet the test requirements.

[0121] Embodiments of this application also provide an insulation detection system for a converter valve, wherein the converter valve includes at least one valve tower, such as Figure 10 As shown, the insulation detection system includes: a controller 100, which is used to execute any of the insulation detection methods of the converter valve described above; and an equivalent circuit 200 of any of the converter valve towers described above, which is electrically connected to the controller 100.

[0122] In addition, in some embodiments, the occurrence of valve tower insulation failures can be predicted by analyzing historical insulation test data and using machine learning models.

[0123] For example: acquire historical insulation test data of the converter valve, including insulation test data of different frequencies at different times and ambient temperature during testing; perform data cleaning, preprocessing, and feature extraction steps on the historical insulation test data to obtain processed data; extract the test parameters of the converter valve from the processed data, including the voltage, current, and discharge quantity of the converter valve; use a time series prediction algorithm to predict the changing trend of the test parameters of the converter valve over time to obtain parameter prediction curves; input the parameter prediction curves into a neural network model to predict the probability of converter valve failure in the future time period.

[0124] First, a large amount of historical insulation test data for converter valves is collected, including test results from different frequency bands such as DC withstand voltage tests, switching impulse tests, and lightning impulse tests, as well as the environmental conditions during the tests. The raw data is then cleaned, preprocessed, and feature extracted; for example, key features such as voltage distribution, current characteristics, and discharge quantity are extracted from the test results. Time series prediction methods such as ARIMA and Holt-Winters are used to analyze the changing trends of test results over time and identify early signs of insulation performance degradation. A neural network model based on LSTM or GRU (Gated Recurrent Unit) is designed, taking the time series of historical test data as input and outputting the probability of failure occurring in the future time period. The converter valves are then inspected and maintained based on the prediction results.

[0125] This comprehensive machine learning-based fault diagnosis and prediction system enables intelligent maintenance of converter valves in high-voltage direct current (HVDC) transmission equipment. It allows for the timely detection of potential insulation problems and the prediction of future fault trends, significantly improving equipment operating efficiency and safety. Furthermore, this approach provides data-driven decision support for equipment lifecycle management, potentially reducing overall maintenance costs and extending equipment lifespan.

[0126] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0128] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0129] 1) The equivalent circuit of the converter valve tower described above in this application includes: multiple parallel load branches, each load branch including an equivalent load, different load branches including different equivalent loads, and the equivalent loads included in different load branches are used to equivalently represent the characteristics of the converter valve tower in different frequency bands; the equivalent load is one of the equivalent resistive load, the equivalent capacitive load, and the composite equivalent load composed of inductance, resistance and capacitance, wherein the characteristics of the converter valve tower are different when operating in different frequency bands, and the characteristics include at least one of resistive, capacitive and inductive. This equivalent circuit employs frequency-domain decoupling design for the wideband equivalent load. The converter valve exhibits resistive behavior under DC voltage, inductive behavior under operational shock, and capacitive behavior under lightning and steep wave front shock. Therefore, the equivalent load is modularly designed, and different circuits under different frequency bands are equivalent. This not only reduces testing costs but also simulates the wideband impedance characteristics of the converter valve under high-frequency impulse voltage by designing equivalent circuits for different frequency bands. This solves the problem that existing converter valve testing methods are not only costly but also inefficient.

[0130] 2) The insulation testing method for the converter valve described in this application determines the conducting branch of the equivalent circuit according to the test frequency band. This means that under different frequency bands, the equivalent circuit will automatically or manually adjust the connection state of its internal components to activate the electrical characteristic simulation branch corresponding to that frequency band. This avoids unnecessary interference from components during the test, ensuring the accuracy and effectiveness of the insulation test. Since the equivalent circuit can adjust its internal connections according to different test frequency bands, this method allows the testing system to adapt to various types of converter valves and simulate electrical environments under various operating conditions. This not only enhances the adaptability of the testing system but also improves the comparability and reliability of the test results. Using the equivalent circuit to replace the actual valve tower for insulation testing can reduce the number of high-voltage devices in the test circuit, reduce the risk of the test sample being directly subjected to high voltage, and thus reduce potential safety hazards during the testing process.

[0131] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An equivalent circuit for a converter valve tower, characterized in that, include: Multiple load branches are connected in parallel, each load branch includes an equivalent load, and the equivalent loads included in different load branches are different. The equivalent loads included in different load branches are used to represent the characteristics of the converter valve tower in different frequency bands. The equivalent load is one of the equivalent resistive load, the equivalent capacitive load, and the composite equivalent load consisting of inductance, resistance, and capacitance. The converter valve tower has different characteristics when operating in different frequency bands, and the characteristics include at least one of resistive, capacitive, and inductive characteristics.

2. The equivalent circuit of the converter valve tower according to claim 1, characterized in that, The plurality of load branches include a first load branch, the first load branch comprising: The first resistor module has a first terminal for electrical connection to the positive terminal of the test voltage source and a second terminal for electrical connection to the negative terminal of the test voltage source.

3. The equivalent circuit of the converter valve tower according to claim 2, characterized in that, When the converter valve tower is a high-pressure valve tower, the resistance value of the first resistor module is a first preset multiple of the resistance value of the converter valve tower. When the converter valve tower is a low-pressure valve tower, the resistance value of the first resistor module is a second preset multiple of the resistance value of the converter valve tower, wherein the first preset multiple is greater than the second preset multiple.

4. The equivalent circuit of the converter valve tower according to claim 1, characterized in that, The converter valve tower includes at least one converter valve assembly, and the plurality of load branches include a second load branch, the second load branch comprising: An inductor equivalent unit, the first end of which is electrically connected to the first pole of the power supply, and the resistance and inductance characteristics of the inductor equivalent unit are the same as those of the saturated reactor of the converter valve. A load equivalent unit, wherein the first end of the load equivalent unit is electrically connected to the second end of the inductance equivalent unit, and the second end of the load equivalent unit is electrically connected to the second pole of the power supply. The resistance, capacitance and inductance characteristics of the load equivalent unit are the same as those of the converter valve assembly. The converter valve assembly includes at least a fully controllable electronic device.

5. The equivalent circuit of the converter valve tower according to claim 4, characterized in that, The inductor equivalent unit includes: The second resistor module has a first terminal electrically connected to the first pole of the power supply and a second terminal electrically connected to the load equivalent unit. A first inductor, wherein a first end of the first inductor is electrically connected to a first end of the second resistor module, and a second end of the first inductor is electrically connected to a second end of the second resistor module.

6. The equivalent circuit of the converter valve tower according to claim 4, characterized in that, The load equivalent unit includes an equivalent module of a parallel damping circuit, an equivalent module of a voltage equalization circuit, and an equivalent module of a parallel structure. The parallel structure is a parallel structure composed of fully controlled electronic devices and surge arresters.

7. The equivalent circuit of the converter valve tower according to claim 6, characterized in that, The equivalent module of the damping circuit includes: A first capacitor, wherein the first terminal of the first capacitor is electrically connected to the second terminal of the inductor equivalent unit; The third resistor module has its first end electrically connected to the second terminal of the first capacitor, and its second end electrically connected to the second terminal of the power supply.

8. The equivalent circuit of the converter valve tower according to claim 6, characterized in that, The equivalent module of the equalizing circuit includes: The fourth resistor module has its first end electrically connected to the second end of the inductor equivalent unit, and its second end electrically connected to the second pole of the power supply.

9. The equivalent circuit of the converter valve tower according to claim 6, characterized in that, The equivalent module of the parallel structure includes: The second inductor, the first end of which is electrically connected to the second end of the inductor equivalent unit; The second capacitor has its first terminal electrically connected to the second terminal of the second inductor. The fifth resistor module has its first terminal electrically connected to the second terminal of the second capacitor, and its second terminal electrically connected to the second terminal of the power supply.

10. The equivalent circuit of the converter valve tower according to claim 1, characterized in that, The plurality of load branches include a third load branch, the third load branch comprising: The third capacitor has its first terminal electrically connected to the positive terminal of the test voltage source and its second terminal electrically connected to the negative terminal of the test voltage source. The capacitance value of the third capacitor is the same as the capacitance value of the distributed capacitance of the converter valve tower when it operates in the third frequency band.

11. An insulation testing method for a converter valve, characterized in that, include: Determine the test frequency band for the converter valve; The conducting branch of the equivalent circuit is determined according to the test frequency band of the converter valve. The equivalent circuit is the equivalent circuit of the converter valve tower according to any one of claims 1 to 10. The conducting branch is at least one of a plurality of parallel load branches. According to the test frequency band of the converter valve, the corresponding test voltage is input to the target valve tower and the conduction branch to perform insulation test on the converter valve. The target valve tower is the valve tower with the highest potential among the converter valves.

12. The insulation testing method according to claim 11, characterized in that, The plurality of load branches include a first load branch, a second load branch, and a third load branch. The first load branch includes a first resistor module, with a first terminal electrically connected to the positive terminal of a test voltage source and a second terminal electrically connected to the negative terminal of the test voltage source. The second load branch includes: a second resistor module, with a first terminal electrically connected to a first terminal of a power supply and a second terminal electrically connected to a load equivalent unit; a first inductor, with a first terminal electrically connected to the first terminal of the second resistor module and a second terminal electrically connected to the second terminal of the second resistor module; a first capacitor, with a first terminal electrically connected to the second terminal of an inductor equivalent unit; and a third resistor module, with a first terminal electrically connected to the second terminal of the first capacitor and a second terminal electrically connected to the second terminal of the power supply. The circuit includes: a fourth resistor module, the first end of which is electrically connected to the second end of the inductor equivalent unit, and the second end of which is electrically connected to the second terminal of the power supply; a second inductor, the first end of which is electrically connected to the second end of the inductor equivalent unit; a second capacitor, the first terminal of which is electrically connected to the second end of the second inductor; a fifth resistor module, the first end of which is electrically connected to the second terminal of the second capacitor, and the second end of which is electrically connected to the second terminal of the power supply; the third load branch includes: a third capacitor, the first terminal of which is electrically connected to the positive terminal of the test voltage source, and the second terminal of which is electrically connected to the negative terminal of the test voltage source, the capacitance value of which is the same as the capacitance value of the distributed capacitance of the converter valve tower when it operates in the third frequency band; the conducting branch of the equivalent circuit is determined according to the test frequency band of the converter valve, including: When the test frequency band is the first frequency band, the conducting branch of the equivalent circuit is determined to be the first load branch; When the test frequency band is the second frequency band, the conducting branches of the equivalent circuit are determined to be the first load branch and the second load branch, and the minimum value of the second frequency band is greater than the maximum value of the first frequency band. When the test frequency band is the third frequency band, the conducting branches of the equivalent circuit are determined to be the first load branch, the second load branch, and the third load branch, and the minimum value of the third frequency band is greater than the maximum value of the second frequency band.

13. The insulation testing method according to claim 11, characterized in that, The corresponding test voltage is input to the target valve tower and the conduction branch according to the test frequency band of the converter valve, including: When the test frequency band is the first frequency band, a DC voltage is input to the target valve tower and the equivalent circuit; When the test frequency band is the second frequency band, the first impulse voltage is input to the target valve tower and the equivalent circuit; When the test frequency band is the third frequency band, a second impulse voltage is input to the target valve tower and the equivalent circuit, and the bandwidth of the second impulse voltage is wider than that of the first impulse voltage.

14. An insulation detection system for a converter valve, characterized in that, The converter valve includes at least one valve tower, and the insulation detection system includes: A controller for performing the insulation detection method for the converter valve according to any one of claims 11 to 13; The equivalent circuit of the converter valve tower according to any one of claims 1 to 10 is electrically connected to the controller.

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