A detection system and method for thyristors of a power module of a converter valve

Abstract

The application discloses a detection system and method for a thyristor of a power module of a converter valve. The system comprises a charging module, a resonance module, a control module and a power module. The control module comprises a triggering unit, a current detection unit and a control unit. The power module comprises a thyristor unit and a power unit. The charging module is used for charging the resonance module. The resonance module is used for providing a resonance current to the power module. The triggering unit is used for triggering the thyristor unit to conduct when an overcurrent fault occurs in the power module. The current detection unit comprises a first current detection unit and a second current detection unit. The first current detection unit is arranged between the resonance module and the power module and is used for detecting the resonance current output by the resonance module. The second current detection unit is arranged on a branch of the thyristor unit and is used for detecting the current flowing through the thyristor unit. The control unit is used for judging whether the thyristor unit is normal according to the resonance current output by the resonance module and the current flowing through the thyristor unit.

Description

Technical Field

[0001] The embodiments of the present invention relate to flexible DC transmission technology, and more particularly to a detection system and method for thyristors in a converter valve power module. Background Technology

[0002] The core of a flexible DC transmission system is a voltage source converter based on fully controlled components. Multilevel technology is the preferred solution for realizing high-voltage, high-capacity voltage source converters. Compared to two-level converters, multilevel converters can achieve high-voltage output using low-voltage components. In recent years, the emergence of modular multilevel converters (MMCs) has enabled the successful application of multilevel converters in the field of flexible DC transmission.

[0003] The converter valve design of the modular multilevel converter consists of several identical half-bridge power modules connected in series. In actual operation, if an inter-pole short-circuit fault occurs, the converter valve must trigger the thyristor to conduct and complete the fault ride-through, thus ensuring the safe operation of the flexible DC system.

[0004] Currently, when a short circuit occurs between poles in a flexible DC converter valve, if the thyristor in the converter valve power module is triggered or the thyristor shunt ratio is insufficient, the power module of the flexible DC converter valve will be damaged. Therefore, it is necessary to find a method to detect thyristor failure when a short circuit occurs between poles in a flexible DC converter valve in order to verify the integrity of the thyristor device. Summary of the Invention

[0005] This invention provides a detection system and method for thyristors in a converter valve power module, so as to reliably verify whether the thyristor triggering is normal when an inter-pole short circuit fault occurs in a flexible DC converter valve.

[0006] In a first aspect, embodiments of the present invention provide a detection system for the thyristor of a converter valve power module, the detection system comprising: a charging module, a resonant module, a control module, and a power module;

[0007] The control module includes a trigger unit, a current detection unit, and a control unit; the power module includes a thyristor unit and a power unit; the thyristor unit and the power unit are connected in parallel.

[0008] The charging module is electrically connected to the resonant module and is used to charge the resonant module.

[0009] The resonant module, the thyristor unit, and the power unit are connected in parallel in sequence; the resonant module is used to provide resonant current to the power module.

[0010] The triggering unit is electrically connected to the control terminal of the thyristor unit and is used to trigger the thyristor unit to conduct when the power module experiences an overcurrent fault.

[0011] The current detection unit includes a first current detection unit and a second current detection unit; both the first current detection unit and the second current detection unit are electrically connected to the control unit; the first current detection unit is disposed between the resonant module and the power module, and is used to detect the resonant current output by the resonant module; the second current detection unit is disposed on the thyristor unit branch, and is used to detect the current flowing through the thyristor unit;

[0012] The control unit is used to determine whether the thyristor unit is normal based on the resonant current output by the resonant module and the current flowing through the thyristor unit.

[0013] Optionally, the charging module includes a DC power supply and a first control switch;

[0014] The first end of the DC power supply is electrically connected to the first input end of the resonant module, the second end of the DC power supply is electrically connected to the first end of the first control switch, and the second end of the first control switch is electrically connected to the second input end of the resonant module.

[0015] Optionally, the resonant module includes a first DC capacitor, a reactor, and a second control switch;

[0016] The first end of the first DC capacitor is electrically connected to the first end of the DC power supply and the first end of the reactor; the second end of the first DC capacitor is electrically connected to the second end of the first control switch and the first end of the second control switch; the second end of the reactor is electrically connected to the first end of the thyristor unit; and the second end of the second control switch is electrically connected to the second end of the thyristor unit.

[0017] Optionally, the power unit includes at least one power subunit: each of the power subunits is connected in series.

[0018] Each power subunit includes a first semiconductor device, a first freewheeling diode, a second semiconductor device, a second freewheeling diode, a second DC capacitor, and a discharge resistor;

[0019] The first semiconductor device is connected in anti-parallel to the first freewheeling diode; the second semiconductor device is connected in anti-parallel to the second freewheeling diode; the first terminal of the first semiconductor device is electrically connected to the first terminal of the second DC capacitor and the first terminal of the discharge resistor; the second terminal of the first semiconductor device is electrically connected to the first terminal of the second semiconductor device and the first terminal of the thyristor unit; the second terminal of the second semiconductor device is electrically connected to the second terminal of the thyristor unit, the second terminal of the second DC capacitor and the second terminal of the discharge resistor.

[0020] Secondly, embodiments of the present invention also provide a method for detecting thyristors in a converter valve power module. This detection method is applied to the detection system for thyristors in a converter valve power module described in the first aspect above. The detection method includes:

[0021] The control unit controls the charging module to work in order to charge the resonant module;

[0022] The control unit controls the charging module to be inactive and controls the resonant module to be active so that the resonant module provides resonant current to the power module;

[0023] When the power module experiences an overcurrent fault, the triggering unit triggers the thyristor unit to conduct.

[0024] The first current detection unit detects the resonant current output by the resonant module; the second current detection unit detects the current flowing through the thyristor unit;

[0025] The control unit determines whether the thyristor unit is functioning properly based on the resonant current output by the resonant module and the current flowing through the thyristor unit.

[0026] Optionally, the control unit determines whether the thyristor unit is functioning correctly based on the resonant current output by the resonant module and the current flowing through the thyristor unit, including:

[0027] When the ratio of the resonant current output by the resonant module to the current flowing through the thyristor unit is less than a preset value, the control unit determines that the thyristor unit has experienced a triggering fault.

[0028] Optionally, the control unit determines whether the thyristor unit is functioning correctly based on the resonant current output by the resonant module and the current flowing through the thyristor unit, including:

[0029] When the ratio of the resonant current output by the resonant module to the current flowing through the thyristor unit is greater than the preset value, the control unit determines that the thyristor unit is triggering normally.

[0030] Optionally, the charging module includes a DC power supply and a first control switch;

[0031] The control unit controls the charging module to operate in order to charge the resonant module, including:

[0032] The control unit controls the first control switch to close so that the DC power supply charges the resonant module.

[0033] Optionally, the resonant module includes a first DC capacitor, a reactor, and a second control switch;

[0034] The control unit controls the charging module to be inactive and controls the resonant module to be active so that the resonant module provides resonant current to the power module, including:

[0035] The control unit controls the first control switch to open and controls the second control switch to close so that the resonant module provides resonant current to the power module.

[0036] Optionally, the triggering unit triggers the thyristor unit to conduct by: the triggering unit sending a triggering command through an optical fiber to trigger the thyristor unit to conduct.

[0037] In this embodiment of the invention, a control unit controls the charging module to charge the resonant module. After the resonant module is fully charged, the control unit disables the charging module and activates the resonant module to provide resonant current to the power module. When an overcurrent fault occurs in the power module, a trigger unit activates the thyristor unit. A first current detection unit detects the resonant current output by the resonant module, and a second current detection unit detects the current flowing through the thyristor unit. The control unit then determines whether the thyristor unit is functioning correctly based on the resonant current output by the resonant module and the current flowing through the thyristor unit. Thus, this solution reliably verifies whether the thyristor triggering is functioning correctly. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of a detection system for the thyristor of a converter valve power module provided in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of a detection system for the thyristor of a converter valve power module provided in an embodiment of the present invention;

[0040] Figure 3 This is a flowchart illustrating a method for detecting thyristors in a converter valve power module according to an embodiment of the present invention. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0042] Figure 1 This is a schematic diagram of the structure of a detection system for the thyristor of a converter valve power module provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the detection system includes: a charging module 10, a resonant module 20, a control module 30, and a power module 40; the control module 30 includes a trigger unit 31, a current detection unit 32, and a control unit 33; the power module 40 includes a thyristor unit 41 and a power unit 42; the thyristor unit 41 and the power unit 42 are connected in parallel; the charging module 10 is electrically connected to the resonant module 20 and is used to charge the resonant module 20; the resonant module 20, the thyristor unit 41, and the power unit 42 are connected in parallel in sequence; the resonant module 20 is used to provide resonant current to the power module 40; the trigger unit 31 is electrically connected to the control terminal of the thyristor unit 41 and is used to trigger the power module 40 when a current occurs. In the event of an overcurrent fault, the thyristor unit 41 is triggered to conduct; the current detection unit 32 includes a first current detection unit 321 and a second current detection unit 322; both the first current detection unit 321 and the second current detection unit 322 are electrically connected to the control unit 33; the first current detection unit 321 is located between the resonant module 20 and the power module 40, and is used to detect the resonant current output by the resonant module 20; the second current detection unit 322 is located on the branch of the thyristor unit 41, and is used to detect the current flowing through the thyristor unit 41; the control unit 33 is used to determine whether the thyristor unit 41 is normal based on the resonant current output by the resonant module 20 and the current flowing through the thyristor unit 41.

[0043] The charging module 10 can provide a DC source to charge the resonant module 20; the resonant module 20 can include capacitors and inductors and can provide resonant current; the power unit 42 in the power module 40 includes power sub-units connected in series. In this embodiment, when the power module 40 experiences an overcurrent fault, for example, when each power sub-unit in the flexible DC converter valve experiences an inter-electrode short-circuit fault, the trigger unit 31 will trigger the thyristor unit 41 to conduct, thereby diverting the large current of the power sub-unit inter-electrode short-circuit fault; if the trigger unit 31 triggers the thyristor unit 41 to conduct, the second current detection unit 322 detects the current flowing through the thyristor unit 41 and the first current. When the ratio of the resonant current output by the resonant module 20 detected by the detection unit 321 is greater than a preset value, it is determined that the thyristor unit 41 is triggering normally. When the ratio of the current flowing through the thyristor unit 41 detected by the second current detection unit 322 to the resonant current output by the resonant module 20 detected by the first current detection unit 321 is less than a preset value, the thyristor unit 41 has a small current shunt, and it is determined that the thyristor unit 41 is triggering abnormally, and the thyristor unit 41 has a triggering fault. For example, the first current detection unit 321 and the second current detection unit 322 can be current sensors. In this way, the solution achieves the effect of reliably verifying whether the thyristor triggering is normal.

[0044] Optional, Figure 2 This is a schematic diagram of another detection system for the thyristor of the converter valve power module provided in an embodiment of the present invention; as shown. Figure 2 As shown, the charging module 10 includes a DC power supply E1 and a first control switch K1; the first end of the DC power supply E1 is electrically connected to the first input end of the resonant module 20, the second end of the DC power supply E1 is electrically connected to the first end of the first control switch K1, and the second end of the first control switch K1 is electrically connected to the second input end of the resonant module 20.

[0045] Optional, refer to Figure 2 The resonant module 20 includes a first DC capacitor C1, a reactor L1, and a second control switch K2. The first terminal of the first DC capacitor C1 is electrically connected to the first terminal of the DC power supply 11 and the first terminal of the reactor L1. The second terminal of the first DC capacitor C1 is electrically connected to the second terminal of the first control switch K1 and the first terminal of the second control switch K2. The second terminal of the reactor L1 is electrically connected to the first terminal of the thyristor unit 41, and the second terminal of the second control switch K2 is electrically connected to the second terminal of the thyristor unit 41. When the first control switch K1 is closed, the DC power supply E1 charges the first DC capacitor C1. When the first DC capacitor C1 is fully charged, the second control switch K2 is closed, and the first DC capacitor C1 discharges through the reactor L1, generating a resonant current.

[0046] Optional, refer to Figure 2The power unit 42 includes at least one power sub-unit: each power sub-unit is connected in series; each power sub-unit includes a first semiconductor device T1, a first freewheeling diode D1, a second semiconductor device T2, a second freewheeling diode D2, a second DC capacitor C2, and a discharge resistor R; the first semiconductor device T1 is connected in anti-parallel to the first freewheeling diode D1; the second semiconductor device T2 is connected in anti-parallel to the second freewheeling diode D2; the first terminal of the first semiconductor device T1 is connected to the first terminal of the second DC capacitor C2 and the first terminal of the discharge resistor R1; the second terminal of the first semiconductor device T1 is connected to the first terminal of the second semiconductor device T2 and the first terminal of the thyristor unit 41; the second terminal of the second semiconductor device T2 is connected to the second terminal of the thyristor unit 41, the second terminal of the second DC capacitor C2, and the second terminal of the discharge resistor R. When an overcurrent fault occurs in the power module 40, for example, when an inter-electrode short-circuit fault occurs in any power sub-unit within the flexible DC converter valve, the short-circuit current at point X1 between the electrodes increases. The trigger unit 31 will then trigger the thyristor unit 41 to conduct. The short-circuit current will pass through the thyristor unit 41 and the second freewheeling diode D2. In this way, the thyristor unit 41 can shunt the short-circuit current, preventing excessive current flowing through the second freewheeling diode D2 from damaging it. If the ratio of the actual current flowing through the thyristor unit 41 to the resonant current output by the resonant module 20 is small (i.e., the actual current flowing through the thyristor unit 41 is small and the shunt ratio of the thyristor unit 41 is not reached), the thyristor unit 41 will not trigger properly. When the ratio of the actual current flowing through the thyristor unit 41 to the resonant current output by the resonant module 20 is large, the thyristor unit 41 will trigger normally, and the power module 40 will output different voltage levels through the semiconductor devices within each power sub-unit.

[0047] This invention also provides a method for detecting the thyristors in a converter valve power module. Figure 3 This is a flowchart illustrating a method for detecting thyristors in a converter valve power module according to an embodiment of the present invention. Figure 3 As shown, the detection method includes the following steps:

[0048] S110, the control unit controls the charging module to charge the resonant module.

[0049] S120: The control unit controls the charging module to not work and controls the resonant module to work so that the resonant module provides resonant current to the power module.

[0050] The detection method is applied to the detection system for the thyristor of the converter valve power module in the above embodiment, referring to... Figure 2The charging module 10 includes a DC power supply E1 and a first control switch K1; the resonant module 20 includes a first DC capacitor C1, an inductor L1, and a second control switch K2; specifically, the control unit 33 controls the first control switch K1 to close so that the DC power supply E1 charges the first DC capacitor C1; when the first DC capacitor C1 is fully charged, the control unit 33 controls the first control switch K1 to open and controls the second control switch K2 to close so that the resonant module 20 provides resonant current to the power module 40.

[0051] S130. When an overcurrent fault occurs in the power module, the trigger unit triggers the thyristor unit to conduct.

[0052] The power module includes multiple power sub-units. When an overcurrent fault occurs in the power module, for example, when an inter-electrode short-circuit fault occurs in each power sub-unit, the triggering unit 31 triggers the transistor unit 41 to conduct. The short-circuit current will pass through the thyristor unit 41 and the second freewheeling diode D2. In this way, the thyristor unit 41 can shunt the short-circuit current, avoiding the damage to the second freewheeling diode D2 caused by excessive current flowing through it.

[0053] S140, the first current detection unit detects the resonant current output by the resonant module; the second current detection unit detects the current flowing through the thyristor unit.

[0054] S150: The control unit determines whether the thyristor unit is normal based on the resonant current output by the resonant module and the current flowing through the thyristor unit.

[0055] Specifically, if the ratio of the actual current flowing through the thyristor unit 41 detected by the second current detection unit to the resonant current output by the resonant module 20 detected by the first current detection unit is less than a preset value, that is, when the actual current flowing through the thyristor unit 41 is small and the shunt ratio of the thyristor unit 41 is not reached, then the thyristor unit 41 is judged to be abnormally triggered. When the ratio of the actual current flowing through the thyristor unit 41 to the resonant current output by the resonant module 20 is detected to be greater than the preset value, the thyristor unit 41 is considered to be normally triggered. Thus, this solution achieves the effect of reliably verifying whether the thyristor triggering is normal by having the triggering unit send a trigger command through optical fiber to trigger the thyristor unit when an overcurrent fault occurs in the power module, based on the current values ​​detected by each current detection unit.

[0056] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A detection system for thyristors in a converter valve power module, characterized in that, include: Charging module, resonant module, control module, and power module; The control module includes a trigger unit, a current detection unit, and a control unit; the power module includes a thyristor unit and a power unit; the thyristor unit and the power unit are connected in parallel. The charging module is electrically connected to the resonant module and is used to charge the resonant module. The resonant module, the thyristor unit, and the power unit are connected in parallel in sequence; the resonant module is used to provide resonant current to the power module. The triggering unit is electrically connected to the control terminal of the thyristor unit and is used to trigger the thyristor unit to conduct when the power module experiences an overcurrent fault. The current detection unit includes a first current detection unit and a second current detection unit; both the first current detection unit and the second current detection unit are electrically connected to the control unit; the first current detection unit is disposed between the resonant module and the power module, and is used to detect the resonant current output by the resonant module; the second current detection unit is disposed on the thyristor unit branch, and is used to detect the current flowing through the thyristor unit; The control unit is used to determine whether the thyristor unit is functioning properly based on whether the ratio of the resonant current output by the resonant module to the current flowing through the thyristor unit is greater than a preset value.

2. The detection system for the thyristor of the converter valve power module according to claim 1, characterized in that, The charging module includes a DC power supply and a first control switch; The first end of the DC power supply is electrically connected to the first input end of the resonant module, the second end of the DC power supply is electrically connected to the first end of the first control switch, and the second end of the first control switch is electrically connected to the second input end of the resonant module.

3. The detection system for the thyristor of the converter valve power module according to claim 2, characterized in that, The resonant module includes a first DC capacitor, a reactor, and a second control switch. The first end of the first DC capacitor is electrically connected to the first end of the DC power supply and the first end of the reactor; the second end of the first DC capacitor is electrically connected to the second end of the first control switch and the first end of the second control switch; the second end of the reactor is electrically connected to the first end of the thyristor unit; and the second end of the second control switch is electrically connected to the second end of the thyristor unit.

4. The detection system for the thyristor of the converter valve power module according to claim 3, characterized in that, The power unit includes at least one power sub-unit: each of the power sub-units is connected in series. Each power subunit includes a first semiconductor device, a first freewheeling diode, a second semiconductor device, a second freewheeling diode, a second DC capacitor, and a discharge resistor; The first semiconductor device is connected in anti-parallel to the first freewheeling diode; the second semiconductor device is connected in anti-parallel to the second freewheeling diode; the first terminal of the first semiconductor device is electrically connected to the first terminal of the second DC capacitor and the first terminal of the discharge resistor; the second terminal of the first semiconductor device is electrically connected to the first terminal of the second semiconductor device and the first terminal of the thyristor unit; the second terminal of the second semiconductor device is electrically connected to the second terminal of the thyristor unit, the second terminal of the second DC capacitor and the second terminal of the discharge resistor.

5. A method for detecting thyristors in a converter valve power module, characterized in that, The detection system applied to the thyristor of the converter valve power module according to any one of claims 1-4, the detection method comprising: The control unit controls the charging module to work in order to charge the resonant module; The control unit controls the charging module to be inactive and controls the resonant module to be active so that the resonant module provides resonant current to the power module; When the power module experiences an overcurrent fault, the triggering unit triggers the thyristor unit to conduct. The first current detection unit detects the resonant current output by the resonant module; the second current detection unit detects the current flowing through the thyristor unit; The control unit determines whether the thyristor unit is functioning properly based on whether the ratio of the resonant current output by the resonant module to the current flowing through the thyristor unit is greater than a preset value.

6. The method for detecting the thyristor of the converter valve power module according to claim 5, characterized in that, The control unit determines whether the thyristor unit is functioning correctly based on the resonant current output by the resonant module and the current flowing through the thyristor unit, including: When the ratio of the current flowing through the thyristor unit to the resonant current output by the resonant module is less than a preset value, the control unit determines that the thyristor unit has experienced a triggering fault.

7. The method for detecting the thyristor of the converter valve power module according to claim 6, characterized in that, The control unit determines whether the thyristor unit is functioning correctly based on the resonant current output by the resonant module and the current flowing through the thyristor unit, including: When the ratio of the current flowing through the thyristor unit to the resonant current output by the resonant module is greater than the preset value, the control unit determines that the thyristor unit is triggering normally.

8. The method for detecting the thyristor of the converter valve power module according to claim 5, characterized in that, The charging module includes a DC power supply and a first control switch; The control unit controls the charging module to operate in order to charge the resonant module, including: The control unit controls the first control switch to close so that the DC power supply charges the resonant module.

9. The method for detecting the thyristor of the converter valve power module according to claim 8, characterized in that, The resonant module includes a first DC capacitor, a reactor, and a second control switch. The control unit controls the charging module to be inactive and controls the resonant module to be active so that the resonant module provides resonant current to the power module, including: The control unit controls the first control switch to open and controls the second control switch to close so that the resonant module provides resonant current to the power module.

10. The method for detecting the thyristor of the converter valve power module according to claim 8, characterized in that, The triggering unit triggers the thyristor unit to conduct, including: The triggering unit sends a triggering command via optical fiber to trigger the thyristor unit to conduct.

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