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

Abstract

The application provides an equivalent circuit of a converter valve tower, a method and a system for insulation detection of a converter valve, and the equivalent circuit comprises: a plurality of parallel load branches, each load branch comprises an equivalent load, different load branches comprise different equivalent loads, and the equivalent loads of different load branches are used to equivalent characteristics of the converter valve tower 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 inductance, a resistance, and a capacitance, wherein the characteristics of the converter valve tower are different when the converter valve tower operates in different frequency bands, and the characteristics include at least one of resistance, capacitance, and inductance. The equivalent circuit decouples the wideband equivalent load of the converter valve tower in the frequency domain, decouples the equivalent load into different circuits under different frequency bands for equivalent, can reduce the test cost, and can simulate the wideband impedance characteristics of the converter valve under high-frequency impulse voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-voltage direct current transmission, in particular to an equivalent circuit of a converter valve tower, a converter valve insulation detection method and a converter valve insulation detection system. BACKGROUND

[0002] At present, a converter valve includes multiple valve towers, and each valve tower includes multiple valve assemblies. When performing multiple valve insulation tests on an extra-high voltage converter valve, the most direct method is to suspend all valve units (valve towers) for testing. That is, all real valve units (valve towers) need to be connected according to the actual operating structure, and then jointly connected to a test loop for testing.

[0003] In an ultra-high voltage direct current (UHVDC) project, the multiple valve insulation test of a controllable commutation converter valve is a key link to ensure safe and reliable operation of the equipment. However, the traditional test method has key technical problems such as extremely high test cost, complex test loop, huge land occupation, and low test efficiency. SUMMARY

[0004] The main purpose of the present application is to provide an equivalent circuit of a converter valve tower, a converter valve insulation detection method and a converter valve insulation detection system to at least solve the problem of high test cost and low efficiency of the existing converter valve test method.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, an equivalent circuit of a converter valve tower is provided, comprising: multiple parallel load branches, each load branch comprising an equivalent load, different load branches comprising different equivalent loads, and the equivalent loads in different load branches being used to equivalent the characteristics of the converter valve tower in different frequency bands; wherein the equivalent load is one of an equivalent resistance load, an equivalent capacitance load, and a composite equivalent load composed of inductance, resistance and capacitance, wherein the characteristics of the converter valve tower in different frequency bands are different, and the characteristics include at least one of resistance, capacitance and inductance.

[0006] Optionally, the multiple load branches include a first load branch, and the first load branch comprises: a first resistance module, a first end of the first resistance module being used for electrical connection with a positive pole of a test voltage source, and a second end of the first resistance module being used for electrical connection with a negative pole of the test voltage source.

[0007] Optionally, in the case that the converter valve tower is a high-voltage valve tower, the resistance value of the first resistance module is a first preset multiple of the resistance value of the converter valve tower, and in the case that the converter valve tower is a low-voltage valve tower, the resistance value of the first resistance module is a second preset multiple of the resistance value of the converter valve tower, and the first preset multiple is greater than the second preset multiple.

[0008] Optionally, the converter valve tower comprises at least one converter valve assembly, and the plurality of load branches comprises a second load branch, the second load branch comprising: an inductance equivalent unit, a first end of the inductance equivalent unit being electrically connected to a first pole of a power supply, resistance and inductance characteristics of the inductance equivalent unit being identical to resistance and inductance characteristics of a saturable reactor of the converter valve; and a load equivalent unit, a first end of the load equivalent unit being electrically connected to a second end of the inductance equivalent unit, a second end of the load equivalent unit being electrically connected to a second pole of the power supply, resistance, capacitance and inductance characteristics of the load equivalent unit being identical to resistance, capacitance and inductance characteristics of the converter valve assembly, the converter valve assembly comprising at least fully-controlled electronic devices.

[0009] Optionally, the inductance equivalent unit comprises: a second resistance module, a first end of the second resistance module being electrically connected to the first pole of the power supply, a second end of the second resistance module being electrically connected to the load equivalent unit; and a first inductance, a first end of the first inductance being electrically connected to the first end of the second resistance module, a second end of the first inductance being electrically connected to the second end of the second resistance module.

[0010] Optionally, the load equivalent unit comprises equivalent modules of a damping circuit, equivalent modules of a voltage-sharing circuit and equivalent modules of a parallel structure, the parallel structure being a parallel structure composed of fully-controlled electronic devices and arresters.

[0011] Optionally, the equivalent modules of the damping circuit comprise: a first capacitance, a first pole of the first capacitance being electrically connected to the second end of the inductance equivalent unit; and a third resistance module, a first end of the third resistance module being electrically connected to a second pole of the first capacitance, a second end of the third resistance module being electrically connected to the second pole of the power supply.

[0012] Optionally, the equivalent modules of the voltage-sharing circuit comprise: a fourth resistance module, a first end of the fourth resistance module being electrically connected to the second end of the inductance equivalent unit, a second end of the fourth resistance module being electrically connected to the second pole of the power supply.

[0013] Optionally, the equivalent modules of the parallel structure comprise: a second inductance, a first end of the second inductance being electrically connected to the second end of the inductance equivalent unit; a second capacitance, a first pole of the second capacitance being electrically connected to a second end of the second inductance; and a fifth resistance module, a first end of the fifth resistance module being electrically connected to a second pole of the second capacitance, a second end of the fifth resistance module being electrically connected to the second pole of the power supply.

[0014] Optionally, the plurality of load branches comprises a third load branch, the third load branch comprising: a third capacitor, a first pole of the third capacitor being electrically connected to a positive pole of the test voltage source, a second pole of the third capacitor being electrically connected to a negative pole of the test voltage source, a capacitance value of the third capacitor being the same as a capacitance value of a distributed capacitance of the converter valve tower when the converter valve tower is operating in a third frequency band.

[0015] According to another aspect of the present application, there is provided a method for insulation detection of a converter valve, comprising: determining a test frequency band of the converter valve; determining a conducting branch of an equivalent circuit according to the test frequency band of the converter valve, the equivalent circuit being any one of the equivalent circuits of the converter valve tower, the conducting branch being at least one of a plurality of parallel load branches; inputting a corresponding test voltage into a target tower and the conducting branch according to the test frequency band of the converter valve, to perform insulation detection on the converter valve, the target tower being a tower with the highest potential in the converter valve.

[0016] Optionally, the plurality of load branches comprises a first load branch, a second load branch and a third load branch, the first load branch comprises a first resistance module, a first end of the first resistance module is configured to be electrically connected with a positive pole of a test voltage source, a second end of the first resistance module is configured to be electrically connected with a negative pole of the test voltage source, the second load branch comprises: a second resistance module, a first end of the second resistance module is electrically connected with a first pole of a power source, a second end of the second resistance module is electrically connected with a load equivalent unit; a first inductor, a first end of the first inductor is electrically connected with the first end of the second resistance module, a second end of the first inductor is electrically connected with the second end of the second resistance module; a first capacitor, a first pole of the first capacitor is electrically connected with a second end of an inductor equivalent unit; a third resistance module, a first end of the third resistance module is electrically connected with a second pole of the first capacitor, a second end of the third resistance module is electrically connected with a second pole of the power source; a fourth resistance module, a first end of the fourth resistance module is electrically connected with the second end of the inductor equivalent unit, a second end of the fourth resistance module is electrically connected with the second pole of the power source; a second inductor, a first end of the second inductor is electrically connected with the second end of the inductor equivalent unit; a second capacitor, a first pole of the second capacitor is electrically connected with a second end of the second inductor; a fifth resistance module, a first end of the fifth resistance module is electrically connected with a second pole of the second capacitor, a second end of the fifth resistance module is electrically connected with the second pole of the power source; the third load branch comprises: a third capacitor, a first pole of the third capacitor is electrically connected with a positive pole of a test voltage source, a second pole of the third capacitor is electrically connected with a negative pole of the test voltage source, a capacitance value of the third capacitor is the same as a capacitance value of a distributed capacitance of the converter valve tower when the converter valve tower operates in a third frequency band, determining a conducting branch of the equivalent circuit according to a test frequency band of the converter valve comprises: in a case where the test frequency band is a first frequency band, determining that the conducting branch of the equivalent circuit is the first load branch; in a case where the test frequency band is a second frequency band, determining that the conducting branch of the equivalent circuit is the first load branch and the second load branch, a minimum value of the second frequency band is greater than a maximum value of the first frequency band; in a case where the test frequency band is a third frequency band, determining that the conducting branch of the equivalent circuit is the first load branch, the second load branch and the third load branch, a minimum value of the third frequency band is greater than a maximum value of the second frequency band.

[0017] Optionally, inputting the corresponding test voltage into the target valve tower and the conducting branch according to the test frequency band of the converter valve comprises: in the case that the test frequency band is a first frequency band, inputting a direct current voltage into the target valve tower and the equivalent circuit; in the case that the test frequency band is a second frequency band, inputting a first impulse voltage into the target valve tower and the equivalent circuit; and in the case that the test frequency band is a third frequency band, inputting a second impulse voltage into the target valve tower and the equivalent circuit, the frequency band of the second impulse voltage being wider than that of the first impulse voltage.

[0018] According to another aspect of the present application, there is provided an insulation detection system of a converter valve, the converter valve comprising at least one valve tower, the insulation detection system comprising: a controller configured to perform any one of the insulation detection methods of the converter valve; and an equivalent circuit of the valve tower of the converter valve, electrically connected to the controller.

[0019] According to the technical solution of the present application, the equivalent circuit of the valve tower of the converter valve comprises: a plurality of parallel load branches, each load branch comprising an equivalent load, different load branches comprising different equivalent loads, the equivalent loads of different load branches being used to equivalently represent the characteristics of the valve tower of the converter valve in different frequency bands; and the equivalent load is one of an equivalent resistance load, an equivalent capacitance load, and a composite equivalent load composed of inductance, resistance, and capacitance, wherein the characteristics of the valve tower of the converter valve are different in different frequency bands, and the characteristics include at least one of resistance, capacitance, and inductance. The equivalent circuit is designed to decouple the equivalent loads in the frequency domain, wherein the valve of the converter valve presents resistance under direct current voltage, presents inductance under operating impulse, and presents capacitance under lightning and steep front impulse. Therefore, the equivalent loads are modularly designed, and different circuits in different frequency bands are equivalently represented. This not only reduces the test cost, but also, through the design of the equivalent circuit in different frequency bands, the real valve tower does not need to be assembled during the test, and only the equivalent circuit needs to be assembled. The assembly of the equivalent circuit is much simpler and easier than that of the real valve tower. Therefore, the time for assembling the circuit can be greatly reduced, the assembly efficiency is improved, and the problem of high test cost and low efficiency of the converter valve test method in the prior art is solved. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and serve as an explanation of the illustrative embodiments of the present application, and are not intended to impose any undue limitations on the present application. In the drawings:

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

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

[0023] FIGS. 3(a)-3(b) show equivalent principle schematic diagrams of a first load branch provided by an embodiment of the application;

[0024] Figure 4 A structural schematic diagram of a second load branch provided by an embodiment of the application is shown;

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

[0026] FIGS. 6(a)-6(b) show equivalent principle schematic diagrams of a second load branch provided by an embodiment of the application;

[0027] FIGS. 7(a)-7(b) show equivalent principle schematic diagrams of a third load branch provided by an embodiment of the application;

[0028] Figure 8 A structural schematic diagram of an equivalent device of a converter valve valve tower provided by an embodiment of the application is shown;

[0029] Figure 9 A flow schematic diagram of an insulation detection method of a converter valve provided by an embodiment of the application is shown;

[0030] Figure 10 A structural schematic diagram of an insulation detection system of a converter valve provided by an embodiment of the application is shown.

[0031] Among the above figures, the following reference signs are included:

[0032] 01, load branch; 10, first load branch; 11, first resistance module; 20, second load branch; 21, inductance equivalent unit; 22, load equivalent unit; 221, equivalent module of damping loop; 222, equivalent module of voltage-sharing loop; 223, equivalent module of parallel structure; 30, third load branch; R1, second resistance module; R2, third resistance module; R3, fourth resistance module; R4, fifth resistance module; L1, first inductance; L2, second inductance; C1, first capacitance; C2, second capacitance; C3, third capacitance; 100, controller; 200, equivalent circuit of converter valve valve tower. DETAILED DESCRIPTION

[0033] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0035] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0036] For the convenience of description, the following describes some nouns or terms related to the embodiments of the present application:

[0037] Ultra High Voltage Direct Current, abbreviated as UHVDC;

[0038] Integrated Gate-commutated Thyristor, abbreviated as IGCT. IGCT is a power electronic device that combines the high-power processing capability of thyristor and the fast gate control turn-off characteristics of insulated gate bipolar transistor (IGBT), and is suitable for high-voltage and high-power power conversion systems.

[0039] As introduced in the background, the most direct method in the prior art for carrying out multiple valve insulation tests of ultra-high voltage converter valve is to suspend all valve units (valve towers) for testing. That is, all real valve units (valve towers) need to be connected according to the actual running structure, and then jointly connected to the test circuit for testing. The core shortcomings and problems of using the above method are:

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

[0041] 2. The test circuit is complex and difficult to build. Multiple valve towers are physically connected to form a test circuit, which requires complex mechanical structures, a large number of high-voltage connection cables and supporting equipment. The circuit is very tedious, time-consuming and labor-intensive to build, and has safety hazards.

[0042] 3. The test site requires a huge space. Multiple large valve towers and their auxiliary equipment require extremely large test hall space, which imposes strict requirements on the area, height, and load-bearing capacity of the test site. The cost of building or renting a dedicated site to meet the test requirements of the ultra-high voltage multiple valve is extremely high.

[0043] 4. The test efficiency is low. Due to the complexity and time-consuming nature of test preparation, circuit construction, and site coordination, the entire multiple valve insulation test cycle is long and inefficient, which restricts the development and iteration of new converter equipment.

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

[0045] To solve the problem of high test cost and low efficiency of the existing converter valve test method, the embodiments of the present application provide an equivalent circuit of a converter valve tower, an insulation detection method of a converter valve, and an insulation detection system of a converter valve.

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

[0047] Figure 1 is a structural schematic diagram of an equivalent circuit of a converter valve tower according to the embodiments of the present application. As shown in Figure 1 the equivalent circuit includes a plurality of parallel load branches 01, each of the load branches 01 includes an equivalent load, different load branches 01 include different equivalent loads, and the equivalent loads included in different load branches 01 are used to equivalent the characteristics of the converter valve tower 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 inductance, resistance, and capacitance. The characteristics of the converter valve tower in different frequency bands are different, and the characteristics include at least one of resistance, capacitance, and inductance.

[0048] The converter valve tower is a converter valve structure using IGCT as a main active blocking device. In the converter valve structure using IGCT as a main active blocking device, the IGCT device and the lightning arrester have an influence, and therefore some common passive equivalent loads, i.e., a simple resistance, inductance and capacitance combination, are only applicable to middle and low frequency tests and cannot simulate the wideband impedance characteristics of the converter valve under high frequency impulse voltage. For active equivalent loads, although a wide frequency band can be covered, it is difficult to withstand 800 kV and above voltage and kiloampere current, and the equivalent impedance distribution when multiple valve strings are connected in series cannot be accurately simulated. The frequency band of the converter valve is generally divided into low frequency band, middle frequency band and high frequency band. Generally, under different frequency bands, the resistance, inductance and capacitance elements inside the valve tower respond differently to the current and voltage, resulting in changes in the impedance characteristics of the entire circuit. By combining these elements in a reasonable way and placing them in a specific load branch, it can be ensured that the equivalent circuit exhibits similar electrical characteristics to the real valve tower in a specific frequency band.

[0049] The above equivalent circuit of the present application can accurately simulate the complex impedance characteristics, dynamic response and energy absorption characteristics of the converter valve tower under wideband in insulation tests (especially lightning impulse, steep front impulse and other transient processes), and is suitable for multiple valve insulation tests of ultra-high voltage controllable commutation converter valves.

[0050] In ultra-high voltage direct current (UHVDC) engineering, the multiple valve insulation test of the controllable commutation converter valve is a key link to ensure the safe and reliable operation of the equipment. However, the traditional test method has key technical problems such as extremely high test cost, complex test circuit, huge land occupation and low test efficiency. To solve the above technical problems, the equivalent circuit of the present embodiment uses an equivalent load to replace part of the valve unit to carry out the test, thereby greatly reducing the number of test samples. In the multiple valve insulation test, the low-cost equivalent load is used to accurately simulate the wideband impedance characteristics of the non-critical valve unit. The above equivalent circuit can cover the entire frequency spectrum of direct current, power frequency and impulse (0~3MHz), and the equivalent error of the impedance under the impulse waveform is <5%, and the volume and cost are much lower than those of the converter valve tower.

[0051] The equivalent circuit abandons the active equivalent load scheme, bypasses the technical bottleneck of high-voltage amplifiers, and turns to passive network topology innovation. The equivalent load is designed for frequency domain decoupling. The converter valve presents resistance under direct current voltage, presents inductance under operating impact, and presents capacitance under lightning and steep wave front impact. Therefore, the equivalent load is designed in a modular manner and is decoupled into different equivalent circuits in different frequency bands. For example, a distributed water-cooled resistor network is equivalent in the low frequency band, a valve unit topology network is equivalent in the medium frequency band, and a distributed stray capacitance network is equivalent in the high frequency band. Finally, the equivalent load device is designed in a layered structure, and R, RL, RC, and RLC impedance networks are used for layered combination. Each layer of impedance network corresponds to a different part 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 of the present application includes a plurality of parallel load branches, each load branch including an equivalent load, different load branches including different equivalent loads, and different load branches including equivalent loads for equivalent characteristics of the converter valve tower 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 inductance, resistance, and capacitance. The characteristics of the converter valve tower in different frequency bands are different, including at least one of resistance, capacitance, and inductance. The equivalent circuit is designed for frequency domain decoupling of the wideband equivalent load. The converter valve presents resistance under direct current voltage, presents inductance under operating impact, and presents capacitance under lightning and steep wave front impact. Therefore, the equivalent load is designed in a modular manner, without the need to assemble the real valve tower during testing. Only the equivalent circuit needs to be assembled, and the assembly of the equivalent circuit is much simpler than the assembly of the real valve tower. Therefore, the assembly time of the circuit can be greatly reduced, the assembly efficiency is improved, and the problem of high testing cost and low efficiency of the converter valve testing method in the prior art is solved.

[0053] In some embodiments, as shown in Figure 2 The first load branch 10 includes a first resistance module 11. The first end of the first resistance module 11 is electrically connected to the positive pole of the test voltage source, and the second end of the first resistance module 11 is electrically connected to the negative pole of the test voltage source.

[0054] The first load branch is an equivalent load circuit of the converter valve tower in a low frequency band. When the converter valve tower is in a low frequency band, the converter valve tower mainly presents a resistance characteristic, and therefore the equivalent load needs to be equivalent to the distributed water-cooled resistance network of the multiple valve units. The first load branch simulates the resistive characteristic of the converter valve tower in a direct current and a low frequency band through a first resistance module. By directly connecting the first resistance module with the positive and negative poles of the power supply, the first load branch 10 can simplify the construction of the test circuit. In a traditional insulation test, if the resistive characteristic of the valve tower is to be simulated, a real valve tower needs to be connected, which has a complex structure and is complicated to connect. However, by using the equivalent circuit model, especially the design of the first load branch, the circuit construction work can be greatly reduced, and time and cost can be saved. By using the resistance module instead of the actual valve tower to simulate the low frequency band and direct current condition, the test cost is significantly reduced. At the same time, since the voltage and current in the test circuit can be controlled through the resistance module, the safety risk brought by high voltage and high current is avoided.

[0055] The traditional method is to estimate the size of the water-cooled resistance according to the length, inner diameter and cooling water conductivity of the water pipe, which has a certain deviation from the true value. However, in the case of known controllable commutation converter valve structure design, the geometric model of the valve tower can be established in COMSOL, and the parameters and boundary conditions of the model can be set, and the equivalent resistance of each part of the valve tower cooling water circuit can be calculated by simulation. Compared with the traditional method, this method well restores the actual water-cooled resistance network topology and improves the calculation accuracy of the water-cooled resistance.

[0056] As shown in FIGS. 3(a)-3(b), according to the electrical connection between the valve towers in actual operation, the water-cooled resistance of the valve tower can be further divided into valve bracket water-cooled resistances R W (R W1 , R W2 , R W3 , R W4 ) and internal valve water-cooled resistances R M (R M1 , R M2 , R M3 , R M4 ), the valve bracket water-cooled resistance R W refers to the resistance of the bracket at the top end of the valve tower, and the valve tower with the highest potential connected to the positive pole of the test voltage source is connected to the positive pole of the test voltage source from the bottom, therefore, the valve bracket water-cooled resistance R W and the internal valve water-cooled resistance R M are in series. And the valve bracket water-cooled resistance R W and the internal valve water-cooled resistance R M are in parallel.

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

[0058] The embodiment can determine the equivalent load DC resistance parameter based on the equivalent resistance network when all valve towers are suspended for the multiple valve insulation test, and can more accurately restore the distribution characteristics of the DC voltage in the multiple valve insulation test. Therefore, as shown in FIG. 3(a) and FIG. 3(b), the equivalent resistance network when all valve units are suspended for the insulation test, i.e. FIG. 3(a) and FIG. 3(b), can be given first, and then compared with the equivalent resistance network when the pole potential valve and the equivalent load are used for the insulation test, and then the resistance network corresponding to the equivalent load is obtained, and the resistance parameter of the equivalent load in the DC voltage withstand test of the valve tower (hereinafter referred to as high-end valve) and the valve tower under low voltage (hereinafter referred to as low-end valve) is calculated.

[0059] Among them, there are four valve towers in the valve hall, four valve towers need to be connected in the voltage range of 800kV~400kV, and only two valve towers need to be connected in the voltage range of 400kV~0kV. When testing the high-end valve (i.e. the voltage range of 800kV~400kV), the second, third and fourth valve towers need to be connected for testing, and the first valve tower (i.e. the first valve tower connected to the negative pole of the test voltage source) is bypassed. When testing the low-end valve (i.e. the voltage range of 400kV~0kV), half of the first valve tower (i.e. the first valve tower connected to the negative pole of the test voltage source) and the second valve tower need to be connected for testing.

[0060] In some embodiments, in the case of the above converter valve tower being a high-voltage valve tower, the resistance value of the first resistance module is a first preset multiple of the resistance value of the above converter valve tower, and in the case of the above converter valve tower being a low-voltage valve tower, the resistance value of the first resistance module is a second preset multiple of the resistance value of the above converter valve tower, and the first preset multiple is greater than the second preset multiple.

[0061] Among them, since more valve towers are connected in the high-voltage range, the equivalent resistance value needs to be larger, and fewer valve towers are connected in the low-voltage range, so the equivalent resistance value needs to be smaller. Therefore, generally, the first preset multiple is greater than the second preset multiple. Since there is a significant difference in the resistive characteristics of high-voltage valve towers and low-voltage valve towers, by setting the resistance value of the first resistance module to be a first preset multiple of the resistance value of the high-voltage valve tower and a second preset multiple of the resistance value of the low-voltage valve tower, it can be ensured that the equivalent circuit model can accurately simulate the resistive characteristics of the actual valve tower under different voltage levels. The above design can flexibly adjust the resistance value of the first resistance module according to the specific voltage level of the measured valve tower, so that the equivalent circuit model can adapt to the testing of different types of converter valves.

[0062] As shown in FIG. 3(a), the valve towers are high-end valves, from the side connected to the negative pole of the test voltage source to the side connected to the positive pole 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-end valve, the first valve tower is bypassed, and the second valve tower, the third valve tower and the fourth valve tower are connected for testing, while the fourth valve tower needs to be tested with a real valve tower, so only the second valve tower and the third valve tower are equivalent. That is, the valve internal water-cooled resistance R M2 , the valve support water-cooled resistance R W3 and the valve internal water-cooled resistance R M3 of the third valve tower, and the valve support water-cooled resistance R W4 and the valve internal water-cooled resistance R M4 of the fourth valve tower. The part in the A box in FIG. 3(a) is the equivalent part of the first load branch.

[0063] As shown in FIG. 3(b), the valve towers are low-end valves, from the side connected to the negative pole of the test voltage source to the side connected to the positive pole of the test voltage source, they 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 with a real valve tower, so only half of the first valve tower is equivalent. That is, the valve internal water-cooled resistance 1 / 2R M1 , the valve support water-cooled resistance R W1 , the valve support water-cooled resistance R W2 and the valve internal water-cooled resistance R M2 of the second valve tower. Similarly, the part in the B box in FIG. 3(b) is the equivalent part of the first load branch.

[0064] Among them, the valve support water-cooled resistance and the valve internal water-cooled resistance of all valve towers are the same, so the resistance value can be directly calculated.

[0065] In some embodiments, 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] The saturable reactor plays a key role in limiting the current rise rate and suppressing harmonics in the converter valve. The inductive equivalent unit, which combines the second resistance module R1 and the first inductance L1, can accurately reproduce the resistive and inductive characteristics of the saturable reactor during dynamic processes, enabling the test loop to more realistically reflect the electrical response of the converter valve under dynamic operating conditions such as operating surges. In high-voltage direct current transmission systems, dynamic events such as operating surges have a significant impact on the performance and safety of the converter valve. By precisely controlling the parameters of the inductive equivalent unit, the test loop can effectively simulate the response of the converter valve during these dynamic events, allowing for more in-depth testing and evaluation of the dynamic performance of the converter valve. Using low-cost second resistance module R1 and first inductance L1 instead of expensive saturable reactors can significantly reduce test costs. At the same time, the structure of the inductive equivalent unit is relatively simple, reducing the complexity of the test loop, facilitating quick setup and adjustment, and improving test efficiency.

[0072] In some embodiments, as shown in FIGS. 1 and 2, the equivalent load unit 22 includes an equivalent module 221 of the damping circuit, an equivalent module 222 of the voltage-sharing circuit, and an equivalent module 223 of the parallel structure composed of full-controlled electronic devices and arresters. Figure 2 and Figure 4 As shown in FIGS. 1 and 2, the equivalent load unit 22 includes an equivalent module 221 of the damping circuit, an equivalent module 222 of the voltage-sharing circuit, and an equivalent module 223 of the parallel structure composed of full-controlled electronic devices and arresters.

[0073] Since the controllable commutated converter valve uses a saturable reactor, the valve unit mainly exhibits inductive characteristics in the medium frequency band. The operating surge voltage in the insulation test corresponds to this frequency range, and the topology of the equivalent load can be designed according to the topology of the valve assembly. To improve the equivalence of the equivalent load, each branch in the circuit topology of the valve assembly is equivalent, including an equivalent branch of the saturable reactor, an equivalent module of the damping circuit, an equivalent module of the voltage-sharing circuit, and an equivalent module of the parallel structure. The electrical parameters of each element in the equivalent load topology can be determined from the design values of the electrical parameters of each element of the controllable commutated converter valve and the measurement results of the wideband impedance characteristics.

[0074] By designing equivalent branches to simulate the damping circuit (for absorbing the resonant energy generated when the switch operates), the voltage equalization circuit (for ensuring the voltage of each part of the converter valve is evenly distributed), and the parallel structure of IGCT devices and arresters (for protecting the devices from over-voltage damage), the load equivalent unit can comprehensively and accurately reproduce the electrical behavior of the converter valve in the medium and high frequency bands. This refined simulation capability helps to more accurately assess the actual operating performance and insulation level of the converter valve. The equivalent module design of the damping circuit and the voltage equalization circuit ensures that the dynamic balance mechanism inside the converter valve can be effectively captured and restored when simulating dynamic operating conditions such as operating impulse voltage. The simulation of the parallel structure of IGCT devices and arresters further enhances the testing of the protection mechanism of the converter valve and improves the reliability of the test results. Real IGCT devices and arresters have high safety risks when tested in a high-voltage and high-current environment. The design of the load equivalent unit allows the use of low-cost and safer equivalent elements for alternative testing, reducing the safety risks in the test and protecting the test personnel and test equipment.

[0075] In some embodiments, as shown in Figure 2 and Figure 4 , the equivalent module 221 of the above-mentioned damping circuit includes: a first capacitor C1, a first pole of the first capacitor C1 is electrically connected with a second end of the inductance equivalent unit 21; a third resistance module R2, a first end of the third resistance module R2 is electrically connected with a second pole of the first capacitor C1, and a second end of the third resistance module R2 is electrically connected with a second pole of the power supply.

[0076] Wherein, Figure 5 is the real converter valve electrical topology diagram. As shown in Figure 2 and Figure 5 , taking the first-stage converter valve as an example, the damping circuit is Figure 5 the branch composed of R s1 and C s1 , Figure 2 the branch composed of the first capacitor C1 and the third resistance module R2 is Figure 5 the branch composed of R s1 and C s1 .

[0077] The damping circuit plays an important role in absorbing and attenuating the resonant energy generated during the switching operation in the converter valve. The equivalent branch composed of the first capacitor C1 and the third resistance module R2 can accurately reproduce the capacitive and resistive response of the damping circuit under operating surges, ensuring that the test circuit can truly reflect the electrical behavior of the converter valve after switching operation. In the dynamic testing of the converter valve, especially in the operating surge voltage test, the first capacitor C1 can store and release electric charge, and the third resistance module R2 can consume this part of energy, thereby stabilizing the voltage and current waveforms of the test circuit, avoiding voltage overshoot and current oscillation caused by resonance effect, and improving the stability and reliability of the testing process. By using the equivalent branch of the first capacitor C1 and the third resistance module R2, high-capacity capacitors and high-power resistors can be avoided in the test, reducing the loss and safety risk of real devices in the high-voltage test environment, and protecting the test equipment and personnel. The values of the first capacitor C1 and the third resistance module R2 can be adjusted according to the testing requirements, which provides greater flexibility for test personnel, and can optimize the equivalent characteristics of the damping circuit according to different test conditions and targets to adapt to different types of converter valves and different levels of surge voltage.

[0078] In some embodiments, as shown in Figure 2 and Figure 4 , the equivalent module 222 of the above-mentioned voltage-sharing circuit comprises: a fourth resistance module R3, a first end of the fourth resistance module R3 is electrically connected with the second end of the inductance equivalent unit 21, and a second end of the fourth resistance module R3 is electrically connected with the second pole of the power supply.

[0079] wherein, Figure 5 is the real electrical topology of the converter valve. As shown in Figure 2 and Figure 5 , taking the first-stage converter valve as an example, the voltage-sharing circuit is Figure 5 R d1 in the branch, Figure 2 the fourth resistance module R3 in Figure 5 is the equivalent resistance of R d1 in

[0080] In particular, the fourth resistance module R3 is designed to effectively imitate the resistive characteristics of the voltage-sharing circuit of the converter valve, ensuring that the voltage distribution in the test circuit during the test, especially under conditions such as operating impulse voltage or lightning impulse, is similar to the voltage distribution when the converter valve is actually in operation, thereby verifying the voltage-sharing effect of the converter valve under these operating conditions. By adjusting the parameters of the fourth resistance module R3, the electrical characteristics thereof can be ensured to be highly matched with the resistance characteristics of the actual voltage-sharing circuit of the converter valve, ensuring the voltage balance between the components of the converter valve in the test environment, which is conducive to accurately evaluating the dynamic performance and insulation level of the converter valve. In traditional tests, in order to simulate the voltage-sharing circuit, a complex multi-component circuit including multiple resistors and other passive components is required. The design of the fourth resistance module R3 simplifies the test circuit, reduces the complexity of constructing and maintaining the test system, and saves costs and resources.

[0081] In some embodiments, as shown in Figure 2 and Figure 4 , the equivalent module 223 of the parallel structure includes: a second inductor L2, a first end of the second inductor L2 being electrically connected to a second end of the inductor equivalent unit 21; a second capacitor C2, a first pole of the second capacitor C2 being electrically connected to a second end of the second inductor L2; a fifth resistance module R4, a first end of the fifth resistance module R4 being electrically connected to a second pole of the second capacitor C2, and a second end of the fifth resistance module R4 being electrically connected to a second pole of the power supply.

[0082] The combination of the second inductor L2, the second capacitor C2 and the fifth resistance module R4 can accurately reproduce the wideband electrical characteristics of the IGCT device and the arrester in parallel. The inductive behavior of the IGCT device is simulated by the second inductor L2, while the capacitive characteristics of the arrester are reflected by the second capacitor C2, and the fifth resistance 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] wherein, Figure 5 is the actual electrical topology of the converter valve. As shown in Figure 2 and Figure 5 , taking the first-stage converter valve as an example, the device refers to the IGCT1 device in Figure 5 , and the arrester refers to the MOV1 in Figure 5 , L s1 is an inductor, Figure 2 The branch composed of the second inductor L2, the second capacitor C2 and the fifth resistance module R4 in Figure 5 is the IGCT1, MOV1 and L s1The equivalent circuit of the branch composed of the first capacitor C1, the third resistor module R2, the second inductor L2, the second capacitor C2 and the fifth resistor module R4. The lightning arrester plays a key role in overvoltage protection in the converter valve, and the parallel design of the second capacitor C2 can effectively absorb and disperse lightning impact or steep front impact voltage, protecting other sensitive elements in the test circuit from overvoltage damage, while ensuring the stability and safety of the test process. By using low-cost elements such as the second inductor L2, the second capacitor C2 and the fifth resistor module R4 to form the equivalent branch, the actual IGCT device and lightning arrester are replaced, greatly reducing the test cost. At the same time, this design simplifies the complexity of the test circuit, reduces the time for test preparation and setting, and improves the test efficiency. The combination of the second inductor L2 and the second capacitor C2 enhances the dynamic response capability of the test circuit in the high frequency band, more accurately simulates the impedance characteristics of the converter valve under high frequency impact, and improves the accuracy and reliability of the test results.

[0084] In addition, in the case of multiple levels of converter valve assemblies, Figure 2 The first capacitor C1 and the third resistor module R2 are used to equivalent R s and C s The fourth resistor module R3 is used to equivalent the resistance R d The second inductor L2, the second capacitor C2 and the fifth resistor module R4 are used to equivalent IGCT, MOV and L s .

[0085] As shown in FIGS. 6(a)-6(b), FIG. 6(a) is an equivalent circuit of the operating impulse test of the high-end valve. The high-end valve needs to be connected to three valve towers during testing, but the high-end valve tower with the highest potential does not need to be equivalent and can be directly connected, i.e., only the two valve towers with lower potential need to be equivalent. As shown in FIG. 6(a), MUV4 is the converter valve assembly structure of the high-end valve tower that does not need to be equivalent, i.e., represents the actual valve tower converter valve assembly structure, and MUV3 and MUV2 are the other two high-end valve towers that need to be equivalent.

[0086] That is, as shown in FIG. 6(a), from the side connected to the negative pole of the test voltage source to the side connected to the positive pole 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-end valve, the first valve tower is bypassed, and the second valve tower, the third valve tower and the fourth valve tower are connected for testing, but the fourth valve tower needs to be tested with a real valve tower, so only the second valve tower and the third valve tower need to be equivalent. That is, the fourth valve tower adopts a real structure, and MVU4 is the converter valve assembly structure of the fourth valve tower. The part in the C box in FIG. 6(a) is the part equivalent to the second load branch, i.e., 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 FIG. 6(a)-6(b), FIG. 6(b) is the equivalent circuit of the operating impulse test of the low-end valve, which needs to be connected to 1.5 valve towers during the test, and the highest potential low-end valve tower does not need to be equivalent, but can be directly connected, that is, only the lower half of the valve tower is equivalent. As shown in FIG. 6(b), from the side connected to the negative pole of the test voltage source to the side connected to the positive pole of the test voltage source, they 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, and the second valve tower needs to be tested with a real valve tower, so only half of the first valve tower is equivalent. That is, the circuit includes the parameters of the half valve thyristor assembly structure of the first valve tower and the thyristor assembly structure of the second valve tower. Similarly, the part in the D box in FIG. 6(b) is the equivalent part of the second load branch, that is, the half of the first valve tower thyristor assembly structure MVU1 needs to be equivalent.

[0088] As shown in some embodiments, Figure 2 The plurality of load branches include a third load branch 30, which includes a third capacitor C3. The first pole of the third capacitor C3 is electrically connected to the positive pole of the test voltage source, the second pole of the third capacitor C3 is electrically connected to the negative pole of the test voltage source, and the capacitance value of the third capacitor C3 is the same as the distributed capacitance value of the thyristor valve tower when operating in the third frequency band.

[0089] The capacitance value of the third capacitor C3 matches the distributed capacitance value of the thyristor valve tower when operating in the high frequency band, ensuring that the test circuit can accurately simulate the electrical characteristics of the actual thyristor valve under high frequency impulse, including lightning impulse and steep front impulse. Inside the thyristor valve, the distribution of high frequency voltage and the absorption of energy by the distributed capacitance play a key role. The accurate simulation of the third capacitor C3 enables the test circuit to truly reflect the high frequency response inside the thyristor valve, helping to verify the rationality of the thyristor valve design and optimize the valve tower structure. Using the third capacitor C3 to replace the high frequency distributed capacitance in the actual thyristor valve tower avoids the high cost and complexity of suspending all valve towers during testing, while reducing the demand for test sites and auxiliary equipment, achieving the economy and efficiency of the test. The capacitance value of the third capacitor C3 can be adjusted according to different test targets, providing greater flexibility for test personnel and enabling more comprehensive performance testing, including different frequencies, different voltage levels, etc.

[0090] Because the controllable commutation valve is large in size and high in integration, the ground stray capacitance is large in value, and mainly presents capacitive characteristics in the high frequency band, so the equivalent load needs to be equivalent to the distributed stray capacitance network of the multiple valve units. In the case of known controllable commutation valve structure design, the geometric model of the valve tower can be established in ANSYS Q3D, and the parameters and boundary conditions of the model are set, and the stray capacitance of the valve tower is calculated through electromagnetic field simulation.

[0091] The stray capacitance of the valve tower can be divided into shield-to-ground capacitance, shield-to-valve module capacitance, valve module-to-ground capacitance, valve module-to-valve module capacitance, etc. According to the electrical connection and stray capacitance distribution inside the valve tower, the equivalent circuit model of the valve tower under high frequency can be obtained. In the lightning impulse and steep wave front impulse test of the 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 all valve units are suspended for insulation test can be given first, and then compared with the stray capacitance network when the pole potential valve and the equivalent load are used for insulation test, and then the stray capacitance network corresponding to the equivalent load is obtained, and the capacitance parameters of the equivalent load in the impulse withstand voltage test of the high-end valve and the low-end valve are calculated.

[0092] As shown in FIG. 7(a), the valve tower is a high-end valve, and from the side connected to the negative pole of the test voltage source to the side connected to the positive pole of the test voltage source, they are respectively the first valve tower, the second valve tower, the third valve tower and the fourth valve tower. When testing the high-end valve, the first valve tower is bypassed, and the second valve tower, the third valve tower and the fourth valve tower are connected for testing, while the fourth valve tower needs to be tested with a real valve tower, so only the second valve tower and the third valve tower are equivalent. That is, the circuit includes the distributed capacitance C M2 of the second valve tower, the distributed capacitance C M3 of the third valve tower, the distributed capacitance C M4 of the fourth valve tower and the ground capacitance C0. The part in the E box in FIG. 7(a) is the part equivalent to the third load branch.

[0093] As shown in FIG. 7(b), the valve tower is a low-end valve, and from the side connected to the negative pole of the test voltage source to the side connected to the positive pole of the test voltage source, they are respectively the first valve tower and the second valve tower. 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 with a real valve tower. That is, the circuit includes the distributed capacitance C M1 of the connected half of the first valve tower and the distributed capacitance C M2 of the second valve tower. Similarly, the part in the F box in FIG. 7(b) is the part equivalent to the third load branch.

[0094] The above equivalent circuit decouples the wideband equivalent load of the controllable commutation valve in the frequency domain, and introduces the design method of the equivalent load module topology and electrical parameters in the low frequency band, the medium frequency band and the high frequency band. The parallel connection of the equivalent load modules in each frequency band can obtain the topology of the wideband equivalent load of the controllable commutation valve.

[0095] In addition, temperature changes directly affect the dielectric constant and loss tangent of the insulating material. High temperature can reduce the dielectric strength, and low temperature can increase the brittleness of the material, thereby affecting the insulation performance. Temperature rise also increases the contact resistance of the electrical connection point, reduces the heat dissipation efficiency, and causes further temperature rise, forming a vicious cycle.

[0096] In a high temperature environment, the dielectric constant and loss tangent of the insulating medium increase, so that the capacitance element in the equivalent circuit needs to be adjusted to a larger value to simulate the capacitance characteristics of the converter valve after the temperature rises. At the same time, considering the influence of temperature on the resistance value, the resistance element parameter in the equivalent circuit also needs to be appropriately corrected to reflect the resistance value change caused by temperature change. That is, the above method further includes the following steps:

[0097] Real-time monitoring of the ambient temperature of the valve tower, and determining the corresponding preset temperature threshold according to the test frequency band of the converter valve tower;

[0098] In the case where the above ambient temperature is greater than the above preset temperature threshold, determining the temperature difference between the above ambient temperature and the above preset temperature threshold;

[0099] According to the temperature difference, determining the capacitance correction amount of the capacitance element and / or the resistance correction amount of the resistance element in the corresponding equivalent circuit;

[0100] Adjusting the capacitance value of the capacitance element in the above equivalent circuit by using the capacitance correction amount of the capacitance element to obtain an adjusted capacitance, and / or adjusting the resistance value of the resistance element in the above equivalent circuit by using the resistance correction amount of the resistance element to obtain an adjusted resistance.

[0101] That is, real-time monitoring of the ambient temperature of the valve tower, when the ambient temperature is greater than the preset value, introducing a temperature compensation mechanism, using a temperature sensor to monitor the test environment, and adjusting the equivalent circuit parameters in real time to ensure the consistency and accuracy of the test results under different temperature conditions. For example, a PT100 temperature sensor is used to monitor the temperature, and then the correction amount of the resistance and capacitance in the equivalent circuit is calculated according to the temperature change formula, and the calculated correction amount is used to compensate the resistance and capacitance, so as to ensure the accuracy of the insulation test.

[0102] According to the topology of the wideband equivalent load, the structure of the equivalent load device is 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 medium-frequency module, and a high-frequency module, etc. The resistance, capacitance, and inductance in each module have multiple sets of parameters that can be selected and adjusted. The equivalent load device adopts the principle of layered design in structure: the DC resistance of the low-frequency module serves as a layer for equivalent to the water-cooled resistance network of the multi-valve unit; the medium-frequency module is divided into three layers, each of which is used for equivalent to the saturated reactor, damping branch, device, and arrester branch in the electrical topology of the multi-valve unit; the capacitance of the high-frequency module serves as a layer for equivalent to the stray capacitance network of the multi-valve unit.

[0103] The embodiments of the present application also provide an insulation detection method of a converter valve, as shown in the description. Figure 9 As shown, the above method comprises the following steps:

[0104] Step S101, determining a test frequency band of the converter valve;

[0105] Step S102, determining a conduction branch of an equivalent circuit according to the test frequency band of the converter valve, the equivalent circuit being any one of the equivalent circuits of the valve towers of the converter valve, and the conduction branch being at least one of a plurality of parallel load branches;

[0106] Step S103, inputting a corresponding test voltage into the target valve tower and the conduction branch according to the test frequency band of the converter valve to perform insulation testing on the converter valve, the target valve tower being the valve tower with the highest potential in the converter valve.

[0107] The selection of the test frequency band is based on the electrical environment that the converter valve may face under actual working conditions, including the electrical characteristics under multiple frequencies such as DC, power frequency, lightning impulse, and steep-front impulse. This ensures that the insulation testing can cover all key frequency bands of the converter valve operation, improving the comprehensiveness and pertinence of the detection.

[0108] The insulation detection method of the converter valve according to the present application determines the conduction branch of the equivalent circuit according to the test frequency band, which means that under different frequency bands, the equivalent circuit will automatically or manually adjust the connection state of its internal elements to activate the electrical characteristic simulation branch corresponding to the frequency band. This avoids unnecessary interference of elements during the testing process, ensuring the accuracy and effectiveness of the insulation testing. Since the equivalent circuit can adjust its internal connection according to different test frequency bands, this method enables the detection system to adapt to multiple types of converter valves and simulate electrical environments under various working conditions. This not only enhances the adaptability of the detection 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 equipment in the test loop, reducing the risk of the test sample being directly subjected to high-voltage voltage, thereby reducing the safety hazards that may occur during the detection process.

[0109] In some embodiments, the first load branch includes a first resistance module, a first end of the first resistance module is electrically connected to a positive pole of a test voltage source, a second end of the first resistance module is electrically connected to a negative pole of the test voltage source, the second load branch includes: a second resistance module, a first end of the second resistance module is electrically connected to a first pole of the power source, a second end of the second resistance module is electrically connected to the load equivalent unit; a first inductor, a first end of the first inductor is electrically connected to the first end of the second resistance module, a second end of the first inductor is electrically connected to the second end of the second resistance module; a first capacitor, a first pole of the first capacitor is electrically connected to the second end of the inductor equivalent unit; a third resistance module, a first end of the third resistance module is electrically connected to a second pole of the first capacitor, a second end of the third resistance module is electrically connected to a second pole of the power source; a fourth resistance module, a first end of the fourth resistance module is electrically connected to the second end of the inductor equivalent unit, a second end of the fourth resistance module is electrically connected to the second pole of the power source; a second inductor, a first end of the second inductor is electrically connected to the second end of the inductor equivalent unit; a second capacitor, a first pole of the second capacitor is electrically connected to the second end of the second inductor; a fifth resistance module, a first end of the fifth resistance module is electrically connected to a second pole of the second capacitor, a second end of the fifth resistance module is electrically connected to the second pole of the power source; the third load branch includes: a third capacitor, a first pole of the third capacitor is electrically connected to a positive pole of a test voltage source, a second pole of the third capacitor is electrically connected to a negative pole of the test voltage source, a capacitance value of the third capacitor is the same as a capacitance value of a distributed capacitance of the converter valve tower when the converter valve tower operates in a third frequency band, a plurality of load branches include the first load branch, the second load branch and the third load branch, and a conduction branch of the equivalent circuit is determined according to a test frequency band of the converter valve, including the following steps:

[0110] In step S1021, when the test frequency band is the first frequency band, the conduction branch of the equivalent circuit is determined as the first load branch.

[0111] In step S1022, when the test frequency band is the second frequency band, the conduction branch of the equivalent circuit is determined as the first load branch and the second load branch, and a minimum value of the second frequency band is greater than a maximum value of the first frequency band.

[0112] In step S1023, when the test frequency band is the third frequency band, the conduction branch of the equivalent circuit is determined as the first load branch, the second load branch and the third load branch, and a minimum value of the third frequency band is greater than a maximum value of the second frequency band.

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

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

[0115] Step S1031, in the case where the test frequency band is the first frequency band, a DC voltage is input into the target valve tower and the conducting branch;

[0116] Step S1032, in the case where the test frequency band is the second frequency band, a first impulse voltage is input into the target valve tower and the equivalent circuit;

[0117] Step S1033, in the case where the test frequency band is the third frequency band, a second impulse voltage is input into the target valve tower and the equivalent circuit, and the frequency band of the second impulse voltage is wider than that of the first impulse voltage.

[0118] The first impulse voltage is an operating impulse voltage, and the general wave front time is 250 microseconds. The second impulse voltage is a lightning impulse voltage or a steep wave impulse voltage. The wave front time of the lightning impulse voltage is generally 1.2 microseconds, and the wave front time of the steep wave impulse voltage is generally 0.2 microseconds. The shorter the wave front time, the wider the frequency band. The wave front time is the time for the amplitude of the wave 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 in the entire frequency band range from low frequency to high frequency is fully evaluated. This full-band test coverage is the basis for 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 operating impulse, is used to detect the dynamic response and energy absorption capacity of the medium frequency band; the second impulse voltage test, such as lightning impulse or steep front impulse, focuses on the response of the converter valve under high frequency impulse. Such a 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 more clear and specific, facilitating the analysis of the insulation condition of the converter valve under different frequency bands. The use of DC voltage, first impulse voltage, and second impulse voltage for testing avoids the use of full-size real valve towers, reduces the number of equipment and the size of the site required for testing, and effectively controls the test cost.

[0120] Specifically, during the insulation test, first, the equivalent load and the test valve (i.e., the target valve tower) are connected in series, and then the test valve (target valve tower) and the equivalent load are connected in parallel with the impulse power supply; then, according to the parameters and structure design of the test valve, the parameters in the equivalent load test are determined, and the corresponding connection of the elements inside the equivalent load is performed; secondly, DC, AC, operating, lightning, and steep front impulse withstand voltage tests are carried out respectively, and the test voltages on the test valve and the equivalent load are measured respectively; finally, it is checked whether the voltage division characteristics and insulation characteristics of the test valve and the equivalent load meet the test requirements.

[0121] Embodiments of the present 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 one of the insulation detection methods for a converter valve described above; and an equivalent circuit 200 of the valve tower of any one of the converter valves described above, which is electrically connected to the controller 100.

[0122] In addition, in some embodiments, the occurrence of valve tower insulation failure can also be predicted by a machine learning model through analysis of historical insulation test data.

[0123] For example, obtain the insulation test history data of the converter valve, the insulation test history data includes insulation test data of different frequency bands at different times and the environmental temperature at the time of test; sequentially perform data cleaning, preprocessing and feature extraction on the insulation test history data to obtain processed data; extract the test parameters of the converter valve from the processed data, the test parameters of the converter valve include the voltage, current and discharge amount of the converter valve; use a time series prediction algorithm to predict the trend of the test parameters of the converter valve over time to obtain a parameter prediction curve; input the parameter prediction curve into a neural network model to predict the probability of converter valve failure occurring in a future time period.

[0124] That is, first, a large amount of converter valve insulation test history data is collected, including test results of different frequency bands such as DC withstand voltage test, operating impulse test, lightning impulse test, and environmental conditions at the time of test. The original data is cleaned, preprocessed and feature extracted, for example, key features such as voltage distribution, current characteristics, discharge amount are extracted from the test results. Time series prediction methods such as ARIMA and Holt-Winters are used to analyze the trend of test results over time and identify early signs of insulation performance deterioration. A neural network model based on LSTM or GRU (Gated Recurrent Unit) is designed, the time series of historical test data is input, and the probability of failure occurring in a future time period is output. And according to the prediction result, the converter valve is checked and maintained.

[0125] Through such a comprehensive machine learning-based fault diagnosis and prediction system, intelligent maintenance of converter valves in high-voltage direct current transmission equipment can be realized, potential insulation problems can be detected in time, future possible failure trends can be predicted, and the operation efficiency and safety of the equipment can be significantly improved. At the same time, this method also provides data-driven decision support for the life cycle management of the equipment, which is expected to reduce the overall maintenance cost and prolong the service life of the equipment.

[0126] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0127] It is also important to note that the terms "comprising", "containing", or any other similar term as used herein are intended to be open-ended. These terms are intended to mean that the process, method, composition, or article of manufacture includes the stated elements, but not excluding other elements. In other words, these terms are intended to be synonymous with "including" or "having".

[0128] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0129] 1) The equivalent circuit of the above-mentioned converter valve tower of the present application comprises a plurality of parallel load branches, each load branch comprising an equivalent load, different load branches comprising different equivalent loads, and different load branches comprising equivalent loads for equivalent characteristics of the converter valve tower 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 inductance, resistance, and capacitance, wherein the characteristics of the converter valve tower in different frequency bands are different, and the characteristics include at least one of resistance, capacitance, and inductance. The equivalent circuit is designed for frequency domain decoupling of wideband equivalent loads, wherein the converter valve presents resistance under DC voltage, inductance under operating impulse, and capacitance under lightning and steep wave front impulse. Therefore, the equivalent load is modularly designed, and different circuits under different frequency bands are equivalent. This not only reduces the test cost, but also simulates the wideband impedance characteristics of the converter valve under high-frequency impulse voltage through the equivalent circuit design of different frequency bands, solving the problem of high test cost and low efficiency of the converter valve test method in the prior art.

[0130] 2) The above-mentioned insulation detection method of the converter valve of the present application determines the conduction branch of the equivalent circuit according to the test frequency band, which means that under different frequency bands, the equivalent circuit will automatically or manually adjust the connection state of its internal elements to activate the electrical characteristic simulation branch corresponding to the frequency band. In this way, unnecessary elements are avoided from interfering in the test process, 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 enables the detection system to adapt to multiple types of converter valves and simulate various working conditions. This not only enhances the adaptability of the detection 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 equipment in the test loop, reducing the risk of the test sample being directly subjected to high-voltage voltage, thereby reducing the safety hazards that may occur during the detection process.

[0131] The above descriptions are only the preferred embodiments of the present application, and are not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An equivalent circuit of a valve tower of a converter valve, characterized in that, The method comprises the following steps: a plurality of parallel load branches, each of the load branches comprises an equivalent load, different load branches comprise different equivalent loads, and different load branches comprise equivalent loads for equivalent different frequency bands within the valve tower of the converter valve; wherein the equivalent load is one of an equivalent resistance load, an equivalent capacitance load, and a composite equivalent load composed of inductance, resistance, and capacitance, wherein the characteristics of the valve tower in different frequency bands are different, and the characteristics include at least one of resistance, capacitance, and inductance.

2. The equivalent circuit of a valve tower of a commutation valve according to claim 1, characterized in that, A plurality of load branches include a first load branch, the first load branch includes: a first resistance module, a first end of the first resistance module is used for electrically connecting with a positive pole of a test voltage source, and a second end of the first resistance module is used for electrically connecting with a negative pole of the test voltage source.

3. The equivalent circuit of a valve tower of a commutation valve according to claim 2, characterized in that, In the case of the converter valve tower being a high-voltage valve tower, the resistance value of the first resistance module is a first preset multiple of the resistance value of the converter valve tower, and in the case of the converter valve tower being a low-voltage valve tower, the resistance value of the first resistance module is a second preset multiple of the resistance value of the converter valve tower, and the first preset multiple is greater than the second preset multiple.

4. The equivalent circuit of a valve tower of a commutation valve according to claim 1, characterized in that, The converter valve tower includes at least one converter valve assembly, and a plurality of load branches include a second load branch, the second load branch includes: an inductance equivalent unit, a first end of the inductance equivalent unit is electrically connected with a first pole of a power supply, and resistance characteristics and inductance characteristics of the inductance equivalent unit are the same as resistance characteristics and inductance characteristics of a saturable reactor of the converter valve; a load equivalent unit, a first end of the load equivalent unit is electrically connected with a second end of the inductance equivalent unit, a second end of the load equivalent unit is electrically connected with a second pole of the power supply, and resistance characteristics, capacitance characteristics, and inductance characteristics of the load equivalent unit are the same as resistance characteristics, capacitance characteristics, and inductance characteristics of the converter valve assembly, and the converter valve assembly at least includes a full-control electronic device.

5. The equivalent circuit of a valve tower of a commutation valve according to claim 4, characterized in that, The inductance equivalent unit includes: a second resistance module, a first end of the second resistance module is electrically connected with the first pole of the power supply, and a second end of the second resistance module is electrically connected with the load equivalent unit; a first inductance, a first end of the first inductance is electrically connected with the first end of the second resistance module, and a second end of the first inductance is electrically connected with the second end of the second resistance module.

6. The equivalent circuit of a valve tower of a commutation valve according to claim 4, characterized in that, The load equivalent unit includes an equivalent module of a damping circuit, an equivalent module of a voltage-sharing circuit, and an equivalent module of a parallel structure, and the parallel structure is a parallel structure composed of a full-control electronic device and a lightning arrester.

7. The equivalent circuit of a valve tower of a thyristor valve according to claim 6, characterized in that, The equivalent module of the damping circuit includes: a first capacitance, a first pole of the first capacitance is electrically connected with the second end of the inductance equivalent unit; a third resistance module, a first end of the third resistance module is electrically connected with a second pole of the first capacitance, and a second end of the third resistance module is electrically connected with the second pole of the power supply.

8. The equivalent circuit of a valve tower of a commutation valve according to claim 6, characterized in that, The equivalent module of the voltage-sharing circuit includes: A fourth resistor module, a first end of the fourth resistor module is electrically connected with the second end of the inductor equivalent unit, and a second end of the fourth resistor module is electrically connected with the second pole of the power supply.

9. The equivalent circuit of a valve tower of a commutation valve according to claim 6, characterized in that, The equivalent module in parallel structure comprises: A second inductor, a first end of the second inductor is electrically connected with the second end of the inductor equivalent unit; A second capacitor, a first pole of the second capacitor is electrically connected with the second end of the second inductor; A fifth resistor module, a first end of the fifth resistor module is electrically connected with the second pole of the second capacitor, and a second end of the fifth resistor module is electrically connected with the second pole of the power supply.

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

11. A method of insulation detection of a converter valve, characterized by Comprise: Determine the test frequency band of the converter valve; According to the test frequency band of the converter valve, determine the conducting branch of the equivalent circuit, the equivalent circuit is the equivalent circuit of the converter valve tower in any one of claims 1 to 10, and the conducting branch is at least one of a plurality of parallel load branches; According to the test frequency band of the converter valve, input the corresponding test voltage into the target tower and the conducting branch, so as to perform insulation test on the converter valve, and the target tower is the tower with the highest potential in the converter valve.

12. The insulation detection method according to claim 11, wherein 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 resistance module, a first end of the first resistance module is used for electrical connection with a positive pole of a test voltage source, a second end of the first resistance module is used for electrical connection with a negative pole of the test voltage source, the second load branch includes: a second resistance module, a first end of the second resistance module is electrically connected with a first pole of a power supply, a second end of the second resistance module is electrically connected with a load equivalent unit; a first inductor, a first end of the first inductor is electrically connected with the first end of the second resistance module, a second end of the first inductor is electrically connected with the second end of the second resistance module; a first capacitor, a first pole of the first capacitor is electrically connected with a second end of an inductor equivalent unit; a third resistance module, a first end of the third resistance module is electrically connected with a second pole of the first capacitor, a second end of the third resistance module is electrically connected with a second pole of the power supply; a fourth resistance module, a first end of the fourth resistance module is electrically connected with the second end of the inductor equivalent unit, a second end of the fourth resistance module is electrically connected with the second pole of the power supply; a second inductor, a first end of the second inductor is electrically connected with the second end of the inductor equivalent unit; a second capacitor, a first pole of the second capacitor is electrically connected with a second end of the second inductor; a fifth resistance module, a first end of the fifth resistance module is electrically connected with a second pole of the second capacitor, a second end of the fifth resistance module is electrically connected with the second pole of the power supply; the third load branch includes: a third capacitor, a first pole of the third capacitor is electrically connected with a positive pole of a test voltage source, a second pole of the third capacitor is electrically connected with a negative pole of the test voltage source, a capacitance value of the third capacitor is the same as a capacitance value of a distributed capacitance when the converter valve tower is running in a third frequency band, a conduction branch of an equivalent circuit is determined according to a test frequency band of the converter valve, including: In the case that the test frequency band is a first frequency band, the conduction branch of the equivalent circuit is determined as the first load branch; In the case that the test frequency band is a second frequency band, the conduction branch of the equivalent circuit is determined as the first load branch and the second load branch, a minimum value of the second frequency band is greater than a maximum value of the first frequency band; In the case that the test frequency band is a third frequency band, the conduction branch of the equivalent circuit is determined as the first load branch, the second load branch and the third load branch, a minimum value of the third frequency band is greater than a maximum value of the second frequency band.

13. The insulation detection method of claim 11, wherein According to the test frequency band of the converter valve, a corresponding test voltage is input into a target valve tower and the conduction branch, including: In the case that the test frequency band is a first frequency band, a direct current voltage is input into the target valve tower and the equivalent circuit; In the case that the test frequency band is a second frequency band, a first impulse voltage is input into the target valve tower and the equivalent circuit; In a case where the test frequency band is a third frequency band, a second impulse voltage is input to the target valve tower and the equivalent circuit, the frequency band of the second impulse voltage being wider than that of the first impulse voltage.

14. An insulation detection system of a converter valve, characterized by The converter valve comprises at least one valve tower, and the insulation detection system comprises: a controller configured to perform the insulation detection method of the converter valve according to any one of claims 11 to 13; and 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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