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

Abstract

The application discloses a kind of based on light control thyristor's flexible direct current converter valve submodule and black module defense method, the submodule is half-bridge module, it is built into flexible direct current converter valve;The submodule includes: bypass switch, light control thyristor, first IGBT, second IGBT, first diode, second diode, DC capacitor and voltage-sharing resistance;Bypass switch is parallel in bridge mouth, light control thyristor is parallel in bypass switch, the emitter of first IGBT is respectively connected with the gate of second IGBT and the anode of light control thyristor, second IGBT is parallel in light control thyristor, first diode is parallel in first IGBT, second diode is parallel in second IGBT, one end of DC capacitor is connected with the gate of first IGBT, the other end is connected with the emitter of second IGBT, voltage-sharing resistance is parallel in DC capacitor.The application solves the DC system trip outage fault condition caused by most black module failure, improves the operation stability of flexible direct current converter valve, with good industrial application value.

Description

Technical Field

[0001] This invention relates to the field of flexible DC transmission technology, and in particular to a flexible DC converter valve submodule based on optically controlled thyristors and a black module defense method. Background Technology

[0002] Flexible DC transmission technology integrates the most cutting-edge power electronics technologies and represents the pinnacle of DC transmission technology and even the entire power transmission technology field. Its outstanding technological advantages and wide application scope determine the broad prospects for its future development. Modular multilevel converters are widely used in flexible DC transmission projects, with each phase arm consisting of the same number of cascaded sub-modules.

[0003] During the unlocking and operation phase of the flexible DC converter valve, the system continues to operate even when a black module fault occurs. However, due to communication interruption, the module status cannot be uploaded and the valve control cannot issue commands. At this time, the bypass switch cannot operate due to other interferences, and the module continues to charge until the power device suffers overvoltage breakdown, which seriously affects the safe and stable operation of the DC transmission system.

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

[0005] The technical problem this invention aims to solve is how to prevent the bypass switch from malfunctioning due to a black module during the operation of a flexible DC-DC converter valve, which could lead to overvoltage damage to the power devices. To address this problem, this invention provides a flexible DC-DC converter valve submodule based on a light-controlled thyristor and a black module defense method.

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

[0007] The flexible DC converter 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 equalization resistor;

[0008] The bypass switch is connected in parallel to the bridge port, the optically controlled thyristor is connected in parallel to the bypass switch, the emitter of the first IGBT is connected to the gate of the second IGBT and the anode of the optically controlled thyristor, the second IGBT is connected in parallel to the optically 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 the cascading interface between each flexible DC converter valve sub-module.

[0009] Preferably, when a black module appears in the flexible DC converter valve during operation, the optical thyristor is controlled to conduct, thereby bypassing the black module.

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

[0011] Preferably, the optically controlled thyristor is turned on, including:

[0012] When the optically controlled thyristor is subjected to a positive voltage and receives a light trigger signal, it indicates that the optically controlled thyristor is normally turned on; when the voltage across the optically controlled thyristor is greater than the positive overvoltage protection threshold, it indicates that the optically controlled thyristor is forcibly turned on.

[0013] Secondly, embodiments of the present invention provide a black module defense method for flexible DC-DC converter valves based on optically controlled thyristors, applied to the flexible DC-DC converter valve sub-modules described above, including:

[0014] The flexible DC converter valve is subjected to black module detection based on black module detection conditions to obtain fault detection results; wherein, the black module detection conditions are that the flexible DC converter valve is in operation, and the black module detection is to determine whether the flexible DC converter valve submodule in the flexible DC converter valve is a black module.

[0015] Based on the fault detection results, 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, then the redundant modules with the same number of black modules in the bridge arm are run, and a trigger signal is emitted 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 it is, the corresponding black module is taken out of operation. Otherwise, the light-controlled thyristor is forcibly turned on by uncontrolled charging, and the corresponding black module is taken out of operation.

[0017] The redundant modules with the same number of black modules in the bridge arm are continuously operated until the flexible DC converter valve stops operating.

[0018] Based on the fault detection results, the flexible DC converter valve was inspected using a black module after it was 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 fiber optic failure and control unit failure.

[0020] Preferably, after determining 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 the number of redundant modules is determined to be less than the number of black modules, a trip request signal is sent to the polar controller through the valve control; based on the trip request signal, the flexible DC converter valve is shut down for maintenance.

[0022] Preferably, determining whether the optically controlled thyristor is normally turned on based on the optical trigger signal includes:

[0023] When the optically controlled thyristor is subjected to a positive voltage and receives an optical trigger signal, it indicates that the optically controlled thyristor is conducting normally.

[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 step of forcibly turning on the optically controlled thyristor through uncontrolled charging includes:

[0026] By continuously charging the black module corresponding to the light-controlled thyristor without control, the voltage across the light-controlled thyristor is made greater than the forward overvoltage protection threshold, thereby forcibly turning on the light-controlled thyristor.

[0027] Compared with existing technologies, the beneficial effects of the flexible DC converter valve submodule and black module defense method based on optically controlled thyristors in this embodiment of the invention are as follows: using optically controlled thyristors as a special bypass switch for the half-bridge submodule of the flexible DC converter valve, the faulty module is stably disconnected when a black module occurs in the flexible DC converter valve and the bypass switch fails to operate. This solves most of the DC system tripping and shutdown faults caused by black module failures, improves the operational stability of the flexible DC converter valve, and has good industrial application value. Attached Figure Description

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

[0029] Figure 2This is a flowchart illustrating a black module defense method for a flexible DC converter valve based on a light-controlled thyristor according to an embodiment of the present invention.

[0030] Figure 1 In the diagram, K is the bypass switch; T is the light-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 Implementation

[0031] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

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

[0033] like Figure 1 As shown, this embodiment of the invention provides a flexible DC converter 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 DC-DC converter valve submodule includes: 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, 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 is a half-bridge module, the bridge port refers to the cascading interface between the flexible DC converter valve sub-modules.

[0036] When a black module appears in the flexible DC-DC converter valve during operation, the optically controlled thyristor is turned on, bypassing the black module. A black module is a faulty module, including flexible DC-DC converter valve sub-modules that cannot receive commands from the valve control or whose module status cannot be uploaded to the valve control. In other words, during normal operation of the flexible DC-DC converter valve, if the control unit of any flexible DC-DC converter valve sub-module cannot receive commands from the valve control, or if the module status of the flexible DC-DC converter valve sub-module cannot be uploaded to the valve control, then that flexible DC-DC converter valve sub-module is defined as a black module. The optically controlled thyristor is turned on specifically when it is subjected to a forward voltage and receives a light trigger signal; when the voltage across the optically controlled thyristor exceeds the forward overvoltage protection threshold, it is forcibly turned on. It should be noted that since the flexible DC-DC converter valve sub-module is a half-bridge module, it is turned off when subjected to a reverse voltage. The photosensitive thyristor features a forward forced conduction function. It integrates a switching diode within the photosensitive area. When the voltage across the photosensitive thyristor, i.e., the bridge voltage, reaches or exceeds the designed forward overvoltage protection threshold, the switching diode breaks down, triggering the thyristor to conduct. This effectively protects the thyristor device while reliably bypassing the faulty black module, thereby improving the black module defense capability of the flexible DC 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 switching diode integrated in the photosensitive thyristor are all determined by this threshold.

[0037] like Figure 2 As shown, this embodiment of the invention provides a black module defense method for flexible DC-DC converter valves based on optically controlled thyristors, applied to the flexible DC-DC converter valve sub-module described above, including the following steps:

[0038] S1. Perform black module detection on the flexible DC converter valve based on the black module detection conditions to obtain the fault detection results;

[0039] Specifically, for simplicity, the flexible DC converter valve submodule will be referred to as the submodule below. The black module detection condition is that the flexible DC converter valve is in operation, specifically from the start of controllable charging until lockout. Black module detection is used to determine whether a submodule within the flexible DC converter valve is a black module.

[0040] The black module detection process in this embodiment will be described in detail below:

[0041] 1) When the submodule is a normal operating submodule, if the bypass switch can be closed normally, it means that the submodule bypass is successful. At this time, the number of closed bypass switches is reset to zero.

[0042] 2) If the submodule was previously a bypass switch closed submodule, and the uplink communication is detected to be normal and no bypass switch is closed for 2ms, then the submodule is determined to be a normal submodule, and the normal communication count is cleared to zero.

[0043] 3) If the submodule was previously a black module, and the bypass switch is detected to be closed for 150ms, then the submodule is determined to be a normal bypass submodule, and the bypass switch closure count is reset to zero.

[0044] 4) If the uplink communication is detected to be normal for 2ms, the submodule is determined to be a normal submodule, and the normal communication count is reset to zero.

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

[0046] Furthermore, the fault detection results include the fault type and the location of the black module. The fault types include power supply failure, communication fiber optic failure, and control unit failure, all manifesting as loss of communication between the submodule and the valve controller, with the faulty module entering an uncontrolled mode. Communication between the valve controller and the optically controlled thyristor is established using an independent optical fiber, which improves the anti-interference capability of the communication circuit and the black module defense capability.

[0047] S2. Based on the fault detection results, 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, then run the redundant modules with the same number of black modules in the bridge arm, and emit a trigger signal to the photoelectric thyristor of each black module through valve control.

[0048] Specifically, the optical trigger signal is a preset frequency optical signal that continues until the fault disappears or the flexible DC converter valve stops operating, ensuring stable triggering of the optically controlled thyristor when the bypass switch is not activated. Further, in this embodiment, the optical trigger signal is a 1kHz optical signal.

[0049] It is understandable that there are two possible outcomes when determining whether the number of redundant modules is greater than the number of black modules: 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 following steps are involved:

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

[0051] The valve controls the sending of a trip request signal to the polarity controller to prevent overvoltage damage to the power devices in the module.

[0052] 2) Based on the trip request signal, the flexible DC converter valve is shut down for maintenance.

[0053] S3. Determine whether the optical thyristor is conducting normally based on the optical trigger signal. If it is, exit the corresponding black module. Otherwise, force the optical thyristor to conduct through uncontrolled charging and exit the corresponding black module.

[0054] Specifically, when the optically controlled thyristor is subjected to a forward voltage and receives a light trigger signal, it indicates that the optically controlled thyristor is normally turned on. By continuously charging the black module corresponding to the optically controlled thyristor without control, the voltage across the optically controlled thyristor is made greater than the forward overvoltage protection threshold, thereby forcibly turning on the optically controlled thyristor.

[0055] For ease of understanding, when the bypass switch fails to operate for other reasons, the photoelectric thyristor has the normal conduction conditions. After conduction, it bypasses the module bridge port when it experiences a positive voltage. If the photoelectric thyristor fails to conduct, due to the interruption of communication between the black module and the valve control, the module's uncontrolled charging causes the bridge port voltage to reach or exceed the positive overvoltage protection threshold, forcing the photoelectric thyristor to conduct. This bypasses the module bridge port when it experiences a positive voltage. It should be noted that, because the flexible DC converter valve submodule of this invention is a half-bridge module, when the black module experiences a reverse voltage, it bypasses the black module through the second diode, causing the black module to exit operation.

[0056] S4. Continuously run the same number of redundant modules with the same number of black modules in the bridge arm until the flexible DC converter valve stops operating.

[0057] S5. Based on the fault detection results, perform black module maintenance on the flexible DC converter valve after it has been shut down.

[0058] Specifically, the black module is repaired or replaced based on the fault detection results recorded in the valve control log.

[0059] In summary, this invention provides a flexible DC-DC converter valve submodule based on optically controlled thyristors and a black module defense method. The optically controlled thyristors serve as a special bypass switch for the half-bridge submodule of the flexible DC-DC converter valve. When a black module appears in the flexible DC-DC converter valve and the bypass switch fails to operate, the faulty module is stably disconnected. This solves most DC system tripping and shutdown faults caused by black module failures, improves the operational stability of the flexible DC-DC converter valve, and has significant industrial application value.

[0060] The various embodiments in this specification are described in a progressive manner. For directly identical or similar parts of the various embodiments, refer to each other. Each embodiment focuses on its differences from other embodiments. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as these combinations of technical features do not contradict each other, they should be considered within the scope of this specification.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A light-controlled thyristor-based HVDC valve black module defense method applied to a HVDC valve sub-module, characterized in that, The flexible direct current valve sub-module is a half-bridge module, which is built-in the flexible direct current valve; The flexible direct current valve 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 a bridge port, the light-controlled thyristor is connected in parallel with the bypass switch, the emitter of the first IGBT is connected with the collector of the second IGBT and the anode of the light-controlled thyristor respectively, 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 collector of the first IGBT, the other end of the direct current capacitor is connected with the emitter of the second IGBT, and the voltage-sharing resistor is connected in parallel with the direct current capacitor; wherein the flexible direct current valve comprises a plurality of flexible direct current valve sub-modules, and the bridge port is a cascading interface between each flexible direct current valve sub-module; When a black module appears in the flexible direct current valve in the running state, the light-controlled thyristor is controlled to be turned on so that the black module is bypassed; The black module comprises a flexible direct current valve sub-module that cannot receive a valve control issued command or a flexible direct current valve sub-module whose module state cannot be uploaded to the valve control; The light-controlled thyristor turning on comprises: When the light-controlled thyristor bears a forward voltage and receives a light trigger signal, it is characterized that the light-controlled thyristor is normally turned on; when the voltage between the two ends of the light-controlled thyristor is greater than a forward overvoltage protection threshold, it is characterized that the light-controlled thyristor is forcibly turned on; The method comprises: Based on the black module detection condition, the flexible direct current valve is detected for a black module to obtain a fault detection result; wherein the black module detection condition is that the flexible direct current valve is in a running state, and the black module detection is to determine whether a flexible direct current valve sub-module in the flexible direct current valve is a black module; Based on the fault detection result, it is judged whether the number of redundant modules of a bridge arm where the black module is located is greater than the number of black modules; if it is judged that the number of redundant modules is greater than the number of black modules, the same number of redundant modules as the black modules in the bridge arm is run, and a light trigger signal is issued to the light-controlled thyristor of each black module through valve control; Based on the light trigger signal, it is judged whether the light-controlled thyristor is normally turned on; if yes, the corresponding black module is exited from running; otherwise, the light-controlled thyristor is forcibly turned on through uncontrolled charging, and the corresponding black module is exited from running; The same number of redundant modules as the black modules in the bridge arm is continuously run until the flexible direct current valve is shut down; Based on the fault detection result, the flexible direct current valve after shutdown is repaired for a black module.

2. The soft black module defense method of claim 1, wherein, The fault detection result comprises a fault type and a position of a black module, and the fault type comprises a power supply fault, a communication optical fiber fault and a control unit fault.

3. The soft black module defense method for a line commutated converter valve according to claim 1, characterized in that, After the judgment based on the fault detection result whether the number of redundant modules of a bridge arm where the black module is located is greater than the number of black modules, the method further comprises: 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 HVDC valve is shut down for maintenance based on the request trip signal.

4. The LIG module defense method of claim 1, wherein, The method further includes: When the light triggered thyristor is subjected to a forward voltage and receives a light trigger signal, it is determined that the light triggered thyristor is normally turned on.

5. The LIG module defense method of claim 1, wherein, The light trigger signal is a light signal of a preset frequency, which lasts until the fault disappears or the HVDC valve is shut down.

6. The LIG module defense method of claim 1, wherein, The method further includes: The light triggered thyristor is forced to be turned on by continuously charging the black module corresponding to the light triggered thyristor without control, so that the voltage across the light triggered thyristor is greater than a forward overvoltage protection threshold, thereby forcing the light triggered thyristor to be turned on.

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