A short circuit current test system and method for a converter valve

Abstract

The application relates to the technical field of electrical engineering, and discloses a short-circuit current test system and method for a converter valve, wherein a generator branch comprises a short-circuit generator, a short-circuit control unit and a bidirectional thyristor valve; one end of the generator branch is connected to one end of a test valve through the short-circuit control unit and the bidirectional thyristor valve in sequence; the other end of the test valve is connected to the other end of the generator branch; a capacitor branch is arranged in parallel at both ends of the test valve, and the capacitor branch comprises a short-circuit valve body control unit, a capacitor group and a direct-current power supply; one end of the short-circuit valve body control unit is connected to one end of the test valve, and the other end is connected to the other end of the test valve through the capacitor group; and the direct-current power supply is arranged in parallel on the capacitor group; the application realizes independent decoupling adjustment of short-circuit current AC and DC components, and meets the test requirements for gradually increased short-circuit current peak values, heat capacities and short-circuit currents containing high proportion of DC components.

Description

Technical Field

[0001] This invention relates to the field of electrical engineering technology, specifically to a short-circuit current testing system and method for converter valves. Background Technology

[0002] Short-circuit current testing is a key test item in converter valve type testing, focusing on assessing the performance of converter valves under fault conditions. It is an important means of evaluating the operational reliability and short-circuit fault resistance capability of converter valves. The currently used test method is a direct short-circuit generator test based on the fault current test of thyristor converter valves, which can meet the test requirements of voltage source converter valves where the DC component of the short-circuit current is not high.

[0003] With the further increase in the capacity of flexible DC transmission converter valves and the continuous deepening and development of hybrid DC transmission technology consisting of conventional DC and flexible DC, the short-circuit capacity of related projects is constantly increasing. On the other hand, the continuous increase in the capacitance value of the DC support capacitor of the flexible DC transmission converter valve further increases the proportion of the DC component in the short-circuit current, making the assessment of the short-circuit current withstand capability of the MMC converter valve increasingly stringent. Based on the above factors, the requirements for test methods and test parameter control in short-circuit current testing are becoming increasingly stringent, and the AC / DC components of the short-circuit current must meet the requirements of independent and precise control.

[0004] Current technology involves direct testing of the generator system, using a short-circuit generator system as the test power source. By adjusting parameter tuning equipment and valve triggering control timing, a multi-cycle short-circuit current containing a DC component is generated. In this direct testing method using a generator system, both the AC and DC components of the short-circuit test current are generated based on the inherent characteristics of the generator branches. The AC and DC components cannot be independently decoupled and adjusted, and the maximum value of the DC component is 100% of the AC component. This fails to meet the testing requirements for progressively increasing short-circuit current peak values ​​and thermal capacity assessments. Summary of the Invention

[0005] The purpose of this invention is to provide a short-circuit current testing system and method for converter valves, so as to solve the technical problems in the prior art that the AC and DC components cannot be independently decoupled and adjusted, and that the testing requirements for the gradually increasing peak value of short-circuit current, heat capacity, and short-circuit current containing a high proportion of DC component cannot be met.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a converter valve short-circuit current test system, including a generator branch, a capacitor branch, a test valve, and a valve control device; The generator branch includes a short-circuit generator, a short-circuit control unit, and a bidirectional thyristor valve; one end of the generator branch is connected to one end of the test valve in sequence via the short-circuit control unit and the bidirectional thyristor valve; the other end of the test valve is connected to the other end of the generator branch. The capacitor branch is connected in parallel across both ends of the test valve. The capacitor branch includes a short-circuit valve body control unit, a capacitor bank, and a DC power supply. One end of the short-circuit valve body control unit is connected to one end of the test valve, and the other end is connected to the other end of the test valve via the capacitor bank. The DC power supply is connected in parallel across the capacitor bank. The control terminal of the valve control device is connected to the bidirectional thyristor valve and the short-circuit valve body control unit via signal communication.

[0007] Preferably, the short-circuit control unit includes a short-circuit transformer, a first reactor group, and a first switch; One end of the short-circuit transformer is connected to one end of the short-circuit generator, and the other end is connected to the bidirectional thyristor valve via the first reactor group and the first switch in sequence.

[0008] Preferably, the short-circuit valve body control unit includes a second switch, a one-way thyristor valve, and a second reactor group; One end of the second switch is connected to one end of the test valve, and the other end is connected to the capacitor bank via a one-way thyristor valve and a second reactor group.

[0009] Furthermore, the unidirectional thyristor valve is connected to the control terminal of the valve control device.

[0010] Preferably, a freewheeling diode valve is also connected in parallel on the capacitor bank.

[0011] Preferably, a current-limiting resistor is provided between the DC power supply and the capacitor bank.

[0012] Secondly, the present invention also provides a method for testing the short-circuit current of a converter valve, based on the aforementioned short-circuit current testing system for a converter valve, comprising: When the second switch of the capacitor branch is closed, the DC power supply charges the capacitor bank through the current-limiting resistor; after the voltage of the capacitor bank reaches the required value, the DC power supply is disconnected from the capacitor bank. Close the first switch of the generator branch to short-circuit the generator and apply excitation. The valve triggering control timing of the unidirectional thyristor valve and the bidirectional thyristor valve is adjusted by the valve control device to make the circuit conduction so that the peak current of the generator branch and the peak current of the capacitor branch are superimposed at the same time. According to the number of cycles required for the short-circuit current, the triggering number of the bidirectional thyristor valve is controlled by the valve control device to inject the short-circuit current into the test valve.

[0013] Preferably, the generator branch uses a short-circuit generator as the test power source. By adjusting the parameters of the short-circuit generator and the triggering control sequence of the bidirectional thyristor valve, the short-circuit current is injected into the test valve.

[0014] Preferably, the capacitor branch uses a DC power supply to charge the capacitor bank through a current-limiting resistor, adjusts the triggering sequence of the capacitor bank and the unidirectional thyristor valve, and injects the decaying DC component of the short-circuit current into the test valve through the freewheeling diode valve.

[0015] Preferably, the test valve has a one-way conduction characteristic, which allows the short-circuit current of the generator branch and the short-circuit current of the capacitor branch to be superimposed and injected into the test valve.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides a converter valve short-circuit current testing system. By using parallel configurations of the generator and capacitor branches, and independent control of the bidirectional thyristor valve and short-circuit valve body control unit via a valve control device, it enables independent adjustment of the AC and DC components of the short-circuit current. This allows for more accurate simulation of short-circuit conditions during actual operation, thus providing a more precise evaluation of the converter valve's performance. The system's short-circuit generator, capacitor bank, and DC power supply components offer flexible adjustment methods. By adjusting the parameters of these components, the peak value, duration, and AC / DC component ratio of the short-circuit current can be easily changed to adapt to different test requirements and evaluation standards. This invention, through independent adjustment of the AC / DC components and flexible adjustment of short-circuit current parameters, can significantly reduce the number of tests and test time, thereby improving test efficiency.

[0017] Furthermore, by adjusting the parameters and configurations of the short-circuit generator excitation, short-circuit transformer turns ratio, and reactor group, the short-circuit current test requirements of different types and specifications of converter valves can be met.

[0018] Furthermore, the unidirectional thyristor valve and freewheeling diode ensure that the current in the capacitor branch can only flow in one direction. By adjusting the parameters and configuration of the capacitor bank and the second reactor bank, the system can adapt to the test requirements of different types and specifications of converter valves.

[0019] Furthermore, the valve control device can precisely control the unidirectional thyristor valve, including the opening and conduction angles, enabling the system to more accurately simulate short-circuit current conditions in actual operation and improve the accuracy of the test.

[0020] Furthermore, by limiting the charging current, the current-limiting resistor protects the DC power supply and capacitor bank from high current surges, extending the service life of the equipment and improving the reliability of the system.

[0021] This invention also provides a method for testing the short-circuit current of a converter valve. By first charging the capacitor bank, then applying excitation to the short-circuit generator, and adjusting the trigger control sequence of the unidirectional and bidirectional thyristor valves, the short-circuit conditions that the converter valve may encounter in actual operation can be accurately simulated. This accurate simulation helps to more accurately evaluate the performance of the converter valve under short-circuit conditions. By adjusting the trigger control sequence of the thyristor valve through the valve control device, and controlling the triggering frequency of the bidirectional thyristor valve according to the required number of cycles, parameters such as the peak value, duration, and superposition time of the short-circuit current can be flexibly controlled. This flexibility allows the test to adapt to different types and specifications of converter valves, as well as different test requirements and evaluation standards. The capacitor bank charging process is protected by a current-limiting resistor to avoid the large current surge at the beginning of charging. At the same time, during the short-circuit current injection process, the precise control of the thyristor valves ensures stable current flow, reduces the risk of equipment damage due to sudden current changes, and improves the safety and reliability of the test. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the short-circuit current test system for the converter valve in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the internal structure of the converter valve during the short-circuit current test in an embodiment of the present invention. In the diagram: 1. Generator branch; 2. Capacitor branch; 3. Test valve; 4. Valve control device; 11. Short-circuit generator; 12. Short-circuit transformer; 13. First reactor group; 14. First switch; 15. Bidirectional thyristor valve; 21. Second switch; 22. Unidirectional thyristor valve; 23. Second reactor group; 24. Freewheeling diode valve; 25. Capacitor group; 26. Current limiting resistor; 27. DC power supply. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0024] The purpose of this invention is to provide a short-circuit current test system and method for converter valves, so as to solve the technical problems in the prior art that the AC and DC components cannot be independently decoupled and adjusted, and that the test requirements for the gradually increasing peak short-circuit current and heat capacity assessment cannot be met.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1 See Figure 1 and Figure 2 In one embodiment of the present invention, a short-circuit current test system for a converter valve is provided, comprising a generator branch 1, a capacitor branch 2, a test valve 3, and a valve control device 4; the generator branch 1 includes a short-circuit generator 11, a short-circuit control unit, and a bidirectional thyristor valve 15; one end of the generator branch 1 is connected to one end of the test valve 3 sequentially via the short-circuit control unit and the bidirectional thyristor valve 15; the other end of the test valve 3 is connected to the other end of the generator branch 1; the capacitor branch 2 is connected in parallel across the two ends of the test valve 3, wherein the capacitor branch 2 includes a short-circuit valve body control unit, a capacitor bank 25, and a DC power supply 27; one end of the short-circuit valve body control unit is connected to one end of the test valve 3, and the other end is connected to the other end of the test valve 3 via the capacitor bank 25; the DC power supply 27 is connected in parallel across the capacitor bank 25; the control terminal of the valve control device 4 is connected to the bidirectional thyristor valve 15 and the short-circuit valve body control unit respectively via signal communication.

[0026] Specifically, the short-circuit control unit includes a short-circuit transformer 12, a first reactor group 13, and a first switch 14; one end of the short-circuit transformer 12 is connected to one end of the short-circuit generator 11, and the other end is connected to the bidirectional thyristor valve 15 via the first reactor group 13 and the first switch 14 in sequence.

[0027] In this embodiment, by adjusting the excitation of the short-circuit generator 11, the turns ratio of the short-circuit transformer 12, and the parameters and configuration of the reactor group, the short-circuit current test requirements of converter valves of different types and specifications can be met. Specifically, the short-circuit valve body control unit includes a second switch 21, a one-way thyristor valve 22, and a second reactor group 23; one end of the second switch 21 is connected to one end of the test valve 3, and the other end is connected to the capacitor group 25 in sequence via the one-way thyristor valve 22 and the second reactor group 23.

[0028] In this embodiment, the unidirectional thyristor valve 22 and the freewheeling diode ensure that the current in the capacitor branch 2 can only flow in one direction. By adjusting the parameters and configuration of the capacitor bank 25 and the second reactor bank 23, the system can adapt to the test requirements of different types and specifications of converter valves.

[0029] The unidirectional thyristor valve 22 is connected to the control terminal of the valve control device 4.

[0030] In this embodiment, the valve control device 4 can precisely control the unidirectional thyristor valve 22, including the opening and conduction angle, so that the system can more accurately simulate the short-circuit current situation in actual operation and improve the accuracy of the test.

[0031] Specifically, a freewheeling diode valve 24 is also connected in parallel on the capacitor bank 25.

[0032] Specifically, a current-limiting resistor 26 is provided between the DC power supply 27 and the capacitor bank 25.

[0033] In this embodiment, by limiting the charging current, the current-limiting resistor 26 protects the DC power supply 27 and the capacitor bank 25 from large current surges, extending the service life of the equipment and improving the reliability of the system.

[0034] In this embodiment, the unidirectional thyristor valve 22, the bidirectional thyristor valve 15, and the freewheeling diode valve 24 are mounted on a single integrated valve tower. The first layer consists of the freewheeling diode valve 24 connected in series alongside the unidirectional thyristor valve 22, and the second layer consists of the bidirectional thyristor valve 15, which is composed of two unidirectional thyristor valves connected in anti-parallel. The thyristor valve assembly includes a thyristor stage, a damping absorption circuit, a voltage equalization circuit, a thyristor control unit (TCU), valve control, protection, and detection function units, busbars and cables, and valve cooling pipes. The diode valve assembly includes a diode stage, a voltage equalization circuit busbar and cables, and valve cooling pipes. The thyristor valve drive power supply uses a power frequency isolation transformer and a magnetic ring current transformer (CT) for power transmission.

[0035] In this embodiment, the capacitor bank 25 and the reactor bank are equipped with switching / redirection switches, as well as corresponding connecting busbars or cables and short-circuit switches, etc., and the parameters can be freely adjusted according to requirements. The capacitor bank 25 is installed in a metal tower, with sufficient insulation distance reserved between the two layers and between the two capacitors, and is equipped with a safety discharge resistor and a local / remote safety discharge switch.

[0036] The DC power supply 27 should provide charging power to the capacitor bank 25 by charging the capacitor bank 25 through the current-limiting resistor 26. The number of DC power supplies 27 should correspond to the number of capacitor banks 25.

[0037] In summary, the converter valve short-circuit current test system provided in this embodiment, through the parallel arrangement of generator branch 1 and capacitor branch 2, and the independent control of bidirectional thyristor valve 15 and short-circuit valve body control unit by valve control device 4, can independently adjust the AC and DC components of the short-circuit current. This allows the test to more accurately simulate the short-circuit situation in actual operation, thereby more accurately evaluating the performance of the converter valve. The components in the system, such as short-circuit generator 11, capacitor bank 25, and DC power supply 27, provide flexible adjustment means. By adjusting the parameters of these components, the peak value, duration, and ratio of AC and DC components of the short-circuit current can be easily changed to adapt to different test requirements and evaluation standards. This invention, by independently adjusting the AC and DC components and flexibly adjusting the short-circuit current parameters, can significantly reduce the number of tests and test time, thus helping to improve test efficiency.

[0038] Example 2 This embodiment provides a method for testing the short-circuit current of a converter valve, based on the aforementioned short-circuit current testing system for a converter valve, including: When the second switch 21 of capacitor branch 2 is closed, DC power supply 27 charges capacitor bank 25 through current limiting resistor 26; after the voltage of capacitor bank 25 is charged to the required value, DC power supply 27 is disconnected from capacitor bank 25. Close the first switch 14 of generator branch 1 to short-circuit generator 11 and apply excitation; The valve triggering control sequence of the unidirectional thyristor valve 22 and the bidirectional thyristor valve 15 is adjusted by the valve control device 4 to make the circuit conduction so that the peak current of the generator branch 1 and the peak current of the capacitor branch 2 are superimposed at the same time. According to the number of cycles required for the short circuit current, the triggering number of the bidirectional thyristor valve 15 is controlled by the valve control device 4 to inject the short circuit current into the test valve 3.

[0039] In this embodiment, the multi-cycle short-circuit current is generated by combining the generator branch 1 and the capacitor branch 2. Generator branch 1 uses a short-circuit generator 11 system as the test power source. By adjusting the generator parameters, reactor parameters, and the triggering control sequence of the bidirectional thyristor valve 15, a short-circuit current containing both AC and DC components is generated based on the inherent characteristics of generator branch 1. The DC component reaches its maximum value at the first half-wave peak, which is 100% of the AC component. Capacitor branch 2 uses a DC power supply 27 to charge the capacitor bank 25 through the current-limiting resistor 26. By adjusting the parameters of the capacitor bank 25 and the reactor bank, and controlling the triggering sequence of the unidirectional thyristor valve through the freewheeling diode valve 24, a decaying DC component of the short-circuit current is generated. The test valve 3 is unidirectionally open, and the current from generator branch 1 is superimposed with the current from capacitor branch 2, resulting in a short-circuit current injected into the test valve 3.

[0040] This embodiment uses a converter valve short-circuit current test system composed of capacitor branch 2 and generator branch 1 to achieve independent adjustment of the AC and DC components of the short-circuit test current. It can provide a multi-cycle short-circuit current containing a high proportion (over 100%) of DC component. The test circuit has a wide current adjustment range and can meet the test requirements for AC and DC components, I... 2 The requirements for t and short-circuit frequency are met, and the short-circuit waveform generated by generator branch 1 can better meet the actual needs.

[0041] In this invention, the capacitor bank 25 is designed to be installed in the tower and is equipped with a switching switch, etc.

[0042] In this embodiment, the test valve 3 has a unidirectional conduction characteristic, which allows the short-circuit current of the generator branch 1 and the short-circuit current of the capacitor branch 2 to be superimposed and injected into the test valve 3. The test valve 3 is a half-bridge module, that is, the current flows through the diode, which has a unidirectional conduction characteristic. The test valve 3 can also be a thyristor, but the thyristor also needs to receive the valve control trigger signal before it conducts, and it also has a unidirectional conduction characteristic.

[0043] The capacitor bank 25 is equipped with a safety discharge resistor, a short-circuit switch, and local / remote discharge control to ensure rapid and safe discharge after testing; the thyristor valve and diode valve have built-in voltage equalization circuits, damping absorption circuits, and valve cooling pipes to prevent overvoltage or overheating of the devices; the drive power supply adopts the power frequency isolation transformer and magnetic ring CT for power transmission, which is safer, more convenient, and more stable.

[0044] In this embodiment, a converter valve short-circuit current test system composed of capacitor bank 25 and generator circuit is used. By adjusting parameters such as DC power supply 27, capacitor bank 25, and reactor bank, the DC component of the short-circuit current can be adjusted, and the AC component of the short-circuit current can be adjusted by adjusting the excitation current, thereby achieving independent adjustment of the AC and DC components of the short-circuit test current. By adjusting the firing angle of the single / bidirectional thyristor valve 15 and triggering it through the control and protection device, the peak current of generator branch 1 and the peak current of capacitor branch 2 are superimposed at the same time.

[0045] In summary, the short-circuit current test method for converter valves provided in this embodiment accurately simulates the short-circuit conditions that converter valves may encounter in actual operation by first charging the capacitor bank 25, then applying excitation to the short-circuit generator 11, and adjusting the trigger control timing of the unidirectional thyristor valve 22 and the bidirectional thyristor valve 15. This accurate simulation helps to more accurately evaluate the performance of the converter valve under short-circuit conditions. By adjusting the trigger control timing of the thyristor valves through the valve control device 4, and controlling the triggering frequency of the bidirectional thyristor valve 15 according to the required number of cycles, parameters such as the peak value, duration, and superposition time of the short-circuit current can be flexibly controlled. This flexibility allows the test to adapt to different types and specifications of converter valves, as well as different test requirements and evaluation standards. The charging process of the capacitor bank 25 is protected by the current-limiting resistor 26, avoiding the large current surge at the beginning of charging. At the same time, during the short-circuit current injection process, the precise control of the thyristor valves ensures stable current flow and reduces the risk of equipment damage caused by sudden current changes. These measures together improve the safety and reliability of the test.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A short-circuit current testing system for a converter valve, characterized in that, It includes a generator branch (1), a capacitor branch (2), a test valve (3), and a valve control device (4); The generator branch (1) includes a short-circuit generator (11), a short-circuit control unit, and a bidirectional thyristor valve (15); one end of the generator branch (1) is connected to one end of the test valve (3) in sequence via the short-circuit control unit and the bidirectional thyristor valve (15); the other end of the test valve (3) is connected to the other end of the generator branch (1). The capacitor branch (2) is connected in parallel across the two ends of the test valve (3). The capacitor branch (2) includes a short-circuit valve body control unit, a capacitor bank (25), and a DC power supply (27). One end of the short-circuit valve body control unit is connected to one end of the test valve (3), and the other end is connected to the other end of the test valve (3) via the capacitor bank (25). The DC power supply (27) is connected in parallel across the capacitor bank (25). The control terminal of the valve control device (4) is connected to the bidirectional thyristor valve (15) and the short-circuit valve body control unit respectively via signal communication; The short-circuit control unit includes a short-circuit transformer (12), a first reactor group (13), and a first switch (14). One end of the short-circuit transformer (12) is connected to one end of the short-circuit generator (11), and the other end is connected to the bidirectional thyristor valve (15) via the first reactor group (13) and the first switch (14). The short-circuit valve body control unit includes a second switch (21), a one-way thyristor valve (22), and a second reactor group (23). One end of the second switch (21) is connected to one end of the test valve (3), and the other end is connected to the capacitor bank (25) via the one-way thyristor valve (22) and the second reactor group (23).

2. The short-circuit current test system for a converter valve according to claim 1, characterized in that, The one-way thyristor valve (22) is connected to the control terminal of the valve control device (4).

3. The short-circuit current test system for a converter valve according to claim 1, characterized in that, A freewheeling diode valve (24) is also connected in parallel on the capacitor bank (25).

4. The short-circuit current test system for a converter valve according to claim 1, characterized in that, A current-limiting resistor (26) is provided between the DC power supply (27) and the capacitor bank (25).

5. A method for testing the short-circuit current of a converter valve, characterized in that, A converter valve short-circuit current test system according to any one of claims 1-4 includes: When the second switch (21) of the capacitor branch (2) is closed, the DC power supply (27) charges the capacitor bank (25) through the current limiting resistor (26); wherein, the current limiting resistor (26) is set between the DC power supply (27) and the capacitor bank (25); after the voltage of the capacitor bank (25) is charged to the required value, the DC power supply (27) is disconnected from the capacitor bank (25); Close the first switch (14) of the generator branch (1) to short-circuit the generator (11) and apply excitation; By adjusting the valve triggering control timing of the unidirectional thyristor valve (22) and the bidirectional thyristor valve (15) respectively by the valve control device (4), the circuit is turned on, so that the peak current of the generator branch (1) and the peak current of the capacitor branch (2) are superimposed at the same time. According to the number of cycles required for the short circuit current, the triggering number of the bidirectional thyristor valve (15) is controlled by the valve control device (4) to inject the short circuit current into the test valve (3).

6. The method for testing the short-circuit current of a converter valve according to claim 5, characterized in that, The generator branch (1) uses a short-circuit generator (11) as the test power source. By adjusting the parameters of the short-circuit generator (11) and the trigger control timing of the bidirectional thyristor valve (15), the short-circuit current is injected into the test valve (3).

7. The method for testing the short-circuit current of a converter valve according to claim 5, characterized in that, The capacitor branch (2) uses a DC power supply (27) to charge the capacitor bank (25) through a current limiting resistor (26), adjusts the parameters of the capacitor bank (25) and the triggering sequence of the unidirectional thyristor valve, and generates a decaying short-circuit current DC component through the freewheeling diode valve (24) and injects it into the test valve (3). The freewheeling diode valve (24) is connected in parallel on the capacitor bank (25).

8. The method for testing the short-circuit current of a converter valve according to claim 5, characterized in that, The test valve (3) has a unidirectional conduction characteristic, which allows the short-circuit current of the generator branch (1) and the short-circuit current of the capacitor branch (2) to be superimposed and injected into the test valve (3).

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