Flexible DC converter valve submodule and black module defense method based on light-controlled thyristor

Abstract

The invention discloses a light-controlled thyristor-based flexible direct current converter valve sub-module and black module defense method, and the sub-module is a half-bridge module and is arranged in a flexible direct current converter valve; the sub-module comprises a bypass switch, a light-controlled thyristor, a first IGBT, a second IGBT, a first diode, a second diode, a direct-current capacitor and a voltage-sharing resistor. The bypass switch is connected in parallel with the bridge port, the light-controlled thyristor is connected in parallel with the bypass switch, an emitting electrode of the first IGBT is respectively connected with a grid electrode of the second IGBT and an anode of the light-controlled thyristor, the second IGBT is connected in parallel with the light-controlled thyristor, the first diode is connected in parallel with the first IGBT, the second diode is connected in parallel with the second IGBT, one end of the direct-current capacitor is connected with the grid electrode of the first IGBT, and the other end of the direct-current capacitor is connected with the anode of the light-controlled thyristor. The other end of the voltage-sharing resistor is connected with the emitter of the second IGBT; and the voltage-sharing resistor is connected in parallel with the DC capacitor. According to the method, most of the fault conditions of tripping and shutdown of the direct current system caused by black module faults are solved, the operation stability of the flexible direct current converter valve is improved, and the method has good industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current power transmission, and in particular to a flexible direct current commutation valve submodule based on a light-controlled thyristor and a black module defense method. Background Art

[0002] Flexible DC transmission technology integrates the most cutting-edge technologies of current power electronics and is the commanding height in the field of DC transmission and even the entire field of transmission technology. Its outstanding technical advantages and wide application space determine the broad prospects for the future development of this technology. Modular multilevel converters are widely used in flexible DC transmission projects, and each phase bridge arm is composed of the same number of sub-modules cascaded.

[0003] During the unlocking and operation stage of the flexible DC converter valve, it continues to operate when a black module fault occurs. However, due to communication interruption, the module status cannot be uploaded and the valve control cannot issue instructions. At this time, the bypass switch cannot operate due to other interference. The module continues to charge until the power device overvoltage breaks down, seriously affecting the safe and stable operation of the DC transmission system.

[0004] Therefore, it is necessary to propose a new submodule topology for the safe and stable operation of the flexible DC converter valve and equip it with a black module defense method with strong reliability. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to prevent the occurrence of a black module in the operation of a flexible direct current converter valve and the failure of the bypass switch to operate, which may lead to overvoltage in the module and damage to the power device. In order to solve the above technical problem, the present invention provides a flexible direct current converter valve submodule based on a light-controlled thyristor and a black module defense method.

[0006] In a first aspect, an embodiment of the present invention provides a flexible DC converter valve submodule based on a light-controlled thyristor, wherein the flexible DC converter valve submodule is a half-bridge module, which is built into the flexible DC converter valve;

[0007] The flexible direct current commutation valve submodule includes: a bypass switch, a light-controlled thyristor, a first IGBT, a second IGBT, a first diode, a second diode, a DC capacitor and a voltage-equalizing resistor;

[0008] The bypass switch is connected in parallel to the bridge port, the photo-controlled thyristor is connected in parallel to the bypass switch, the emitter of the first IGBT is respectively connected to the gate of the second IGBT and the anode of the photo-controlled thyristor, the second IGBT is connected in parallel to the photo-controlled thyristor, the first diode is connected in parallel to the first IGBT, the second diode is connected in parallel to the second IGBT, one end of the DC capacitor is connected to the gate of the first IGBT, the other end of the DC capacitor is connected to the emitter of the second IGBT, and the voltage-equalizing resistor is connected in parallel to the DC capacitor; wherein the flexible DC converter valve includes multiple flexible DC converter valve sub-modules, and the bridge port is a cascade interface between the flexible DC converter valve sub-modules.

[0009] Preferably, when a black module appears in the flexible DC converter valve in an operating state, the light-controlled thyristor is controlled to be turned on so that the black module is bypassed.

[0010] Preferably, the black module includes a flexible DC converter valve submodule that cannot receive a command sent by the valve control or a flexible DC converter valve submodule whose module status cannot be uploaded to the valve control.

[0011] Preferably, the light-controlled thyristor is turned on, comprising:

[0012] When the photo-controlled thyristor is subjected to a forward voltage and receives a light triggering signal, it indicates that the photo-controlled thyristor is normally turned on; when the voltage across the photo-controlled thyristor is greater than a forward overvoltage protection threshold, it indicates that the photo-controlled thyristor is forced to be turned on.

[0013] In a second aspect, an embodiment of the present invention provides a method for defending a black module of a flexible direct current converter valve based on a light-controlled thyristor, which is applied to the flexible direct current converter valve submodule as described above, and includes:

[0014] Performing black module detection on the flexible direct current converter valve based on a black module detection condition to obtain a fault detection result; wherein the black module detection condition is that the flexible direct current converter valve is in operation, and the black module detection is to determine whether a flexible direct current converter valve submodule in the flexible direct current converter valve is a black module;

[0015] Based on the fault detection result, it is determined whether the number of redundant modules in the bridge arm where the black module is located is greater than the number of black modules. If it is determined that the number of redundant modules is greater than the number of black modules, redundant modules with the same number of black modules in the bridge arm are operated, and a light trigger signal is sent to the photo-controlled thyristor of each black module through valve control;

[0016] Based on the light trigger signal, it is determined whether the light-controlled thyristor is normally turned on, if so, the corresponding black module is shut down, otherwise, the light-controlled thyristor is forced to be turned on by uncontrolled charging, and the corresponding black module is shut down;

[0017] Continuously operating redundant modules with the same number of black modules in the bridge arm until the flexible DC converter valve stops operating;

[0018] Based on the fault detection result, a black module maintenance is performed on the flexible direct current converter valve after it is shut down.

[0019] Preferably, the fault detection result includes the fault type and the location of the black module, and the fault type includes power supply failure, communication optical fiber failure and control unit failure.

[0020] Preferably, after judging whether the number of redundant modules in the bridge arm where the black module is located is greater than the number of black modules based on the fault detection result, the method further includes:

[0021] If it is determined that the number of redundant modules is less than the number of black modules, a request trip signal is sent to the pole control through the valve control; and the flexible direct current converter valve is shut down for maintenance based on the request trip signal.

[0022] Preferably, judging whether the light-controlled thyristor is normally turned on based on the light trigger signal comprises:

[0023] When the light-controlled thyristor is subjected to a forward voltage and receives a light triggering signal, it indicates that the light-controlled thyristor is normally turned on.

[0024] Preferably, the optical trigger signal is an optical signal of a preset frequency, which continues until the fault disappears or the flexible DC converter valve stops operating.

[0025] Preferably, the forcibly turning on the light-controlled thyristor by uncontrolled charging comprises:

[0026] The black module corresponding to the light-controlled thyristor is continuously charged without control, so that the voltage across the two ends of the light-controlled thyristor is greater than the forward overvoltage protection threshold, so as to force the light-controlled thyristor to be turned on.

[0027] Compared with the prior art, the flexible DC converter valve submodule and black module defense method based on photo-controlled thyristors in the embodiment of the present invention have the beneficial effect of using photo-controlled thyristors as a group of special bypass switches of the flexible DC converter valve half-bridge submodule, and stably cutting off the faulty module under the condition that a black module appears in the flexible DC converter valve and the bypass switch refuses to operate, thereby solving most of the DC system tripping and shutdown fault conditions caused by black module failures, improving the operating stability of the flexible DC converter valve, and having good industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the topological structure of a flexible DC commutation valve submodule based on a light-controlled thyristor according to an embodiment of the present invention;

[0029] Figure 2It is a flow chart of a method for defending against black modules of a flexible DC converter valve based on a light-controlled thyristor according to an embodiment of the present invention;

[0030] Figure 1 In the figure, K is the bypass switch; T is the photo-controlled thyristor; T1 is the first IGBT; T2 is the second IGBT; D1 is the first diode; D2 is the second diode; C is the DC capacitor; and R is the voltage-equalizing resistor. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0032] In the description of the present invention, it should be understood that the terms "first" and "second" etc. are used in the present invention to distinguish different objects rather than to describe a specific order.

[0033] like Figure 1 As shown, an embodiment of the present invention provides a flexible DC commutation valve submodule based on a light-controlled thyristor.

[0034] Specifically, the flexible DC converter valve submodule is a half-bridge module, which is built into the flexible DC converter valve.

[0035] The flexible direct current commutation valve submodule comprises: a bypass switch K, a light-controlled thyristor T, a first IGBT (T1), a second IGBT (T2), a first diode D1, a second diode D2, a DC capacitor C and a voltage-equalizing resistor R. Further, the bypass switch K is connected in parallel to the bridge port, the light-controlled thyristor T is connected in parallel to the bypass switch K, the emitter of the first IGBT (T1) is connected to the gate of the second IGBT (T2) and the anode of the light-controlled thyristor T respectively, the second IGBT (T2) is connected in parallel to the light-controlled thyristor T, the first diode D1 is connected in parallel to the first IGBT (T1), the second diode D2 is connected in parallel to the second IGBT (T2), one end of the DC capacitor C is connected to the gate of the first IGBT (T1), the other end of the DC capacitor C is connected to the emitter of the second IGBT (T2), and the voltage-equalizing resistor R is connected in parallel to the DC capacitor C. It should be noted that the flexible DC converter valve includes multiple flexible DC converter valve sub-modules. Since each flexible DC converter valve sub-module of the flexible DC converter valve is a half-bridge module, the bridge port refers to the cascade interface between the flexible DC converter valve sub-modules.

[0036] When a black module appears in the flexible direct current converter valve in the operating state, the light-controlled thyristor is turned on to bypass the black module. Among them, the black module is a faulty module, which includes a flexible direct current converter valve submodule that cannot receive the command issued by the valve control or a flexible direct current converter valve submodule whose module status cannot be uploaded to the valve control. That is to say, during the normal operation of the flexible direct current converter valve, when the control unit of any flexible direct current converter valve submodule cannot receive the command issued by the valve control, or the module status of the flexible direct current converter valve submodule cannot be uploaded to the valve control, the flexible direct current converter valve submodule is defined as a black module. The light-controlled thyristor is turned on, specifically, when the light-controlled thyristor is subjected to a forward voltage and receives a light trigger signal, it indicates that the light-controlled thyristor is normally turned on; when the voltage across the two ends of the light-controlled thyristor is greater than the forward overvoltage protection threshold, it indicates that the light-controlled thyristor is forced to turn on. It should be noted that since the flexible direct current converter valve submodule is a half-bridge module, it is turned off when the light-controlled thyristor is subjected to a reverse voltage. The light-controlled thyristor has a forward forced conduction function, and a turn-on diode is integrated inside the photosensitive area. When the voltage across the light-controlled thyristor, that is, the bridge voltage, reaches or exceeds the designed forward overvoltage protection threshold, the turn-on diode is broken down, triggering the thyristor to conduct, effectively protecting the thyristor device while reliably bypassing the faulty black module, thereby improving the black module defense capability of the flexible direct current converter valve. It should be noted that the forward overvoltage protection threshold is the maximum operating voltage limit of the module, and the parameters of the turn-on diode integrated in the light-controlled thyristor are determined by this threshold.

[0037] like Figure 2 As shown, an embodiment of the present invention provides a method for defending a black module of a flexible direct current converter valve based on a light-controlled thyristor, which is applied to the flexible direct current converter valve submodule as described above, and includes the steps of:

[0038] S1. Perform black module detection on the flexible direct current converter valve based on the black module detection condition to obtain a fault detection result;

[0039] Specifically, in order to simplify the description, the flexible direct current converter valve submodule is referred to as a submodule in the following. The black module detection condition is that the flexible direct current converter valve is in an operating state, and the operating state is after the start of controllable charging and before locking. The black module detection is to determine whether the submodule in the flexible direct current converter valve is a black module.

[0040] The black module detection process of this embodiment is specifically described below:

[0041] 1) When the submodule is a normal operating submodule, if the bypass switch can be closed normally, it means that the submodule is bypassed successfully, and the number of bypass switch closures is reset to zero;

[0042] 2) When the submodule was previously a bypass switch closed submodule, if the uplink communication is detected to be normal and there is no bypass switch closed for 2ms, the submodule is determined to be a normal submodule, and the normal communication count is reset;

[0043] 3) When the submodule was previously a black module, if the bypass switch is detected to be closed for 150ms, the submodule is determined to be a normal bypass submodule, and the bypass switch closing count is reset to zero;

[0044] 4) If the detection finds that the uplink communication is normal and lasts for 2ms, the submodule is determined to be a normal submodule, and the normal communication count is reset;

[0045] 5) If the bypass switch of the normal submodule is not closed, and the average voltage of the bridge arm reaches 600V within 1s and the module uplink communication fault lasts for 1s, the submodule is determined to be a black module, and the uplink communication fault count is reset.

[0046] Furthermore, the fault detection result includes the fault type and the location of the black module. Among them, the fault types include power supply failure, communication fiber failure and control unit failure, all of which are manifested in the loss of communication between the submodule and the valve control, and the faulty module enters the uncontrolled mode. The use of independent optical fibers to establish communication between the valve control and the light-controlled thyristor can improve the anti-interference ability of the communication circuit and the black module defense ability.

[0047] S2. Based on the fault detection result, determine whether the number of redundant modules in the bridge arm where the black module is located is greater than the number of black modules. If it is determined that the number of redundant modules is greater than the number of black modules, operate the redundant modules with the same number of black modules in the bridge arm, and send a light trigger signal to the photo-controlled thyristor of each black module through valve control;

[0048] Specifically, the optical trigger signal is an optical signal of a preset frequency, which lasts until the fault disappears or the flexible DC converter valve stops operating, ensuring that the optically controlled thyristor can be stably triggered when the bypass switch is not in operation. Further, the optical trigger signal in this embodiment is an optical signal of a frequency of 1 kHz.

[0049] It is understandable that there are two judgment results for judging whether the number of redundant modules is greater than the number of black modules, namely, the number of redundant modules is greater than the number of black modules and the number of redundant modules is less than the number of black modules. If the number of redundant modules is less than the number of black modules, the steps include:

[0050] 1) If it is determined that the number of redundant modules is less than the number of black modules, a request trip signal is sent to the pole control through the valve control;

[0051] A request trip signal is sent to the pole control through the valve control to prevent the module from overvoltage and damaging the power devices.

[0052] 2) Shut down and repair the flexible DC converter valve based on the request trip signal.

[0053] S3, judging whether the light-controlled thyristor is normally turned on based on the light trigger signal, if so, the corresponding black module is shut down, otherwise the light-controlled thyristor is forced to be turned on by uncontrolled charging, and the corresponding black module is shut down;

[0054] Specifically, when the light-controlled thyristor is subjected to a forward voltage and receives a light triggering signal, it indicates that the light-controlled thyristor is normally turned on. The black module corresponding to the light-controlled thyristor is continuously charged without control, so that the voltage across the light-controlled thyristor is greater than the forward overvoltage protection threshold, so as to force the light-controlled thyristor to be turned on.

[0055] It is easy to understand that when the bypass switch does not operate due to other reasons, the light-controlled thyristor has normal conduction conditions, and after it is turned on, the module bridge port is bypassed when it is subjected to a forward voltage; if the light-controlled thyristor is not turned on, due to the interruption of the communication between the black module and the valve control, the module does not control the charging so that the bridge port voltage reaches or exceeds the forward overvoltage protection threshold, the light-controlled thyristor is forced to turn on, and the module bridge port is bypassed when it is subjected to a forward voltage. It should be noted that since the flexible direct current commutation valve submodule of the present invention is a half-bridge module, when the black module is subjected to a reverse voltage, the black module is bypassed through the second diode, and the black module exits operation.

[0056] S4, continue to operate the redundant modules with the same number of black modules in the bridge arm until the flexible DC converter valve stops operating;

[0057] S5. Perform black module maintenance on the flexible direct current converter valve after shutdown based on the fault detection result.

[0058] Specifically, the black module is repaired or replaced according to the fault detection result recorded by the valve control system.

[0059] In summary, the embodiments of the present invention provide a flexible DC converter valve sub-module and a black module defense method based on photo-controlled thyristors. Photo-controlled thyristors are used as a group of special bypass switches of the half-bridge sub-module of the flexible DC converter valve. When a black module appears in the flexible DC converter valve and the bypass switch refuses to operate, the faulty module can be stably cut off, thereby solving most of the DC system tripping and shutdown fault conditions caused by black module failures, improving the operating stability of the flexible DC converter valve, and having good industrial application value.

[0060] Each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment can be directly referenced to each other, and each embodiment focuses on the differences from other embodiments. It should be noted that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A flexible DC commutation valve submodule based on light-controlled thyristors, characterized in that: The flexible direct current converter valve submodule is a half-bridge module, which is built into the flexible direct current converter valve; The flexible direct current commutation valve submodule includes: a bypass switch, a light-controlled thyristor, a first IGBT, a second IGBT, a first diode, a second diode, a DC capacitor and a voltage-equalizing resistor; The bypass switch is connected in parallel to the bridge port, the photo-controlled thyristor is connected in parallel to the bypass switch, the emitter of the first IGBT is respectively connected to the gate of the second IGBT and the anode of the photo-controlled thyristor, the second IGBT is connected in parallel to the photo-controlled thyristor, the first diode is connected in parallel to the first IGBT, the second diode is connected in parallel to the second IGBT, one end of the DC capacitor is connected to the gate of the first IGBT, the other end of the DC capacitor is connected to the emitter of the second IGBT, and the voltage-equalizing resistor is connected in parallel to the DC capacitor; wherein the flexible DC converter valve includes multiple flexible DC converter valve sub-modules, and the bridge port is a cascade interface between the flexible DC converter valve sub-modules.

2. The flexible direct current valve submodule according to claim 1, characterized in that: When a black module appears in the flexible DC converter valve in the operating state, the light-controlled thyristor is controlled to be turned on so that the black module is bypassed.

3. The flexible direct current valve submodule according to claim 2, characterized in that: The black module includes a flexible DC converter valve submodule that cannot receive a command sent by the valve control or a flexible DC converter valve submodule whose module status cannot be uploaded to the valve control.

4. The flexible direct current valve submodule according to claim 2, characterized in that: The light-controlled thyristor is turned on, comprising: When the photo-controlled thyristor is subjected to a forward voltage and receives a light triggering signal, it indicates that the photo-controlled thyristor is normally turned on; when the voltage across the photo-controlled thyristor is greater than a forward overvoltage protection threshold, it indicates that the photo-controlled thyristor is forced to be turned on.

5. A method for defending a black module of a flexible DC converter valve based on a light-controlled thyristor, applied to a flexible DC converter valve submodule as claimed in any one of claims 1 to 4, characterized in that: include: Performing black module detection on the flexible direct current converter valve based on a black module detection condition to obtain a fault detection result; wherein the black module detection condition is that the flexible direct current converter valve is in operation, and the black module detection is to determine whether a flexible direct current converter valve submodule in the flexible direct current converter valve is a black module; Based on the fault detection result, it is determined whether the number of redundant modules in the bridge arm where the black module is located is greater than the number of black modules. If it is determined that the number of redundant modules is greater than the number of black modules, redundant modules with the same number of black modules in the bridge arm are operated, and a light trigger signal is sent to the photo-controlled thyristor of each black module through valve control; Based on the light trigger signal, it is determined whether the light-controlled thyristor is normally turned on, if so, the corresponding black module is shut down, otherwise, the light-controlled thyristor is forced to be turned on by uncontrolled charging, and the corresponding black module is shut down; Continuously operating redundant modules with the same number of black modules in the bridge arm until the flexible DC converter valve stops operating; Based on the fault detection result, a black module maintenance is performed on the flexible direct current converter valve after it is shut down.

6. The method for defending against black modules of flexible direct current converter valves according to claim 5, characterized in that: The fault detection result includes the fault type and the location of the black module, and the fault type includes power supply failure, communication optical fiber failure and control unit failure.

7. The method for defending against black modules of flexible direct current converter valves according to claim 5, characterized in that: After judging whether the number of redundant modules in the bridge arm where the black module is located is greater than the number of black modules based on the fault detection result, the method further includes: If it is determined that the number of redundant modules is less than the number of black modules, a request trip signal is sent to the pole control through the valve control; and the flexible direct current converter valve is shut down for maintenance based on the request trip signal.

8. The method for defending against black modules of flexible direct current converter valves according to claim 5, characterized in that: The step of judging whether the light-controlled thyristor is normally turned on based on the light trigger signal comprises: When the light-controlled thyristor is subjected to a forward voltage and receives a light triggering signal, it indicates that the light-controlled thyristor is normally turned on.

9. The method for defending against black modules of flexible direct current converter valves according to claim 5, characterized in that: The optical trigger signal is an optical signal of a preset frequency, which continues until the fault disappears or the flexible DC converter valve stops operating.

10. The method for defending against black modules of flexible direct current converter valves according to claim 5, characterized in that: The method of forcibly turning on the light-controlled thyristor by uncontrolled charging includes: The black module corresponding to the light-controlled thyristor is continuously charged without control, so that the voltage across the two ends of the light-controlled thyristor is greater than the forward overvoltage protection threshold, so as to force the light-controlled thyristor to be turned on.

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