A composite triggering method and composite triggering device for a double-coil bypass switch

Abstract

The present invention discloses a composite triggering method for a dual-coil bypass switch, including a main triggering branch, an auxiliary triggering branch and a BOD overvoltage triggering branch. The main triggering branch and the auxiliary triggering branch each include a respective pull-in coil, and both use a control signal of a processor and / or a first overvoltage signal of a controlled object as a triggering signal to cause the pull-in coil to be energized, thereby performing a bypass operation on the controlled object; the BOD overvoltage triggering branch shares a corresponding pull-in coil with the main triggering branch or the auxiliary triggering branch, and uses a second overvoltage signal of the controlled object as a triggering signal to cause the pull-in coil to be energized, thereby performing a bypass operation on the controlled object. A composite triggering device for a dual-coil bypass switch is also disclosed. A BOD overvoltage triggering branch is added, and even if a processor or an overvoltage protection unit fails, the BOD overvoltage triggering branch can provide a closing current to the pull-in coil, thereby ensuring that the faulty submodule is reliably bypassed.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a composite triggering method and a composite triggering device for a double-coil bypass switch. Background Art

[0002] The broad series submodule field includes but is not limited to VSC-HVDC, SVG, SSC, over-capacity voltage balancing, DC ice melting, energy consumption devices, etc. Taking the typical application of series submodules in SVG system and SSC system as an example, the converter valve bridge arm of SVG system and SSC system is usually composed of hundreds of converter valve submodules in series, and the typical topology of converter valve submodule is full-bridge topology. The over-capacity valve branch of SSC system is usually composed of several to dozens of over-capacity valve submodules in series, and the typical topology of over-capacity valve submodule is half-bridge topology. In order to ensure the reliable operation of converter valves and over-capacity valves, the cascaded submodules will be equipped with bypass switches and matching bypass trigger circuits, so that when a submodule fails, the bypass trigger circuit can be used to close the bypass switch at the corresponding position.

[0003] Considering the failure risk of the single energy storage capacitor and the single pull-in coil in the conventional single-coil bypass switch, the dual-coil bypass switch is equipped with two completely independent bypass trigger systems, the main and auxiliary, without increasing the volume of the bypass switch itself. When a submodule fails, the two sets of bypass trigger signals can generate closing currents on the two pull-in coils. When one electromagnetic system refuses to move, the other electromagnetic system can still generate electromagnetic force, which then drives the moving iron core, the insulating structure and the contacts to complete the closing action of the bypass switch. The more mature triggering methods of the dual-coil bypass switch are as follows: Figure 1 shown.

[0004] In general, Figure 1 The two trigger units in the system can work normally. Both the optical fiber communication control unit in front of the trigger unit and the hardware overvoltage protection unit in front of the trigger unit rely on the control power supply of the submodule. If the submodule loses the control power supply, the optical fiber communication control unit and the overvoltage protection unit will fail at the same time. This faulty submodule that cannot be reliably bypassed will affect the reliable operation of the entire system. Summary of the invention

[0005] The present invention provides a composite triggering method and composite triggering device for a dual-coil bypass switch, which solves the technical problems that the optical fiber communication control unit and the overvoltage protection unit in the existing bypass triggering device fail at the same time, the faulty submodule cannot be reliably bypassed, and the reliable operation of the entire system will be affected.

[0006] The present invention can be achieved through the following technical solutions:

[0007] A composite triggering method for a dual-coil bypass switch, comprising a main triggering branch, an auxiliary triggering branch and a BOD overvoltage triggering branch, wherein the main triggering branch and the auxiliary triggering branch each comprise a respective pull-in coil, and each uses a control signal N1 of a processor and / or a first overvoltage signal N2 of a controlled object as a triggering signal to energize the pull-in coil, thereby performing a bypass operation on the controlled object;

[0008] The BOD overvoltage trigger branch shares a corresponding pull-in coil with the main trigger branch or the auxiliary trigger branch, and uses the second overvoltage signal of the controlled object as a trigger signal to energize the pull-in coil, thereby performing a bypass operation on the controlled object.

[0009] Further, a high-level bypass signal P is preset, and when the control signal N1 is at a low level, it indicates that the processor issues a bypass command, and when the first overvoltage signal N2 is at a low level, it indicates that the DC side voltage of the controlled object is greater than the first voltage threshold;

[0010] The main trigger branch and the auxiliary trigger branch each include a corresponding optical coupling unit, an energy storage capacitor, and a controllable switch;

[0011] The control signal N1 and the first overvoltage signal N2 generate a bypass signal N after logical AND calculation. The bypass signal N and the bypass signal P act together on the optocoupler unit, and the optocoupler unit is used to trigger the corresponding controllable switch to turn on, so that the energy storage capacitor releases energy through the corresponding pull-in coil, thereby triggering the bypass.

[0012] Furthermore, the BOD overvoltage trigger branch includes a breakdown diode BOD and its corresponding controllable switch, and shares a corresponding energy storage capacitor and a pull-in coil with the main trigger branch or the auxiliary trigger branch. When the DC side voltage of the controlled object is greater than the second voltage threshold, the breakdown diode BOD is turned on, triggering the corresponding controllable switch to turn on, so that the energy storage capacitor releases energy through the corresponding pull-in coil, thereby triggering the bypass.

[0013] Furthermore, the second voltage threshold is greater than the first voltage threshold.

[0014] A composite trigger device based on the composite trigger method of the double-coil bypass switch described above, wherein the main trigger branch and the auxiliary trigger branch also include corresponding optical coupling units, controllable switches, energy storage capacitors, and charging power supplies.

[0015] The cathodes of the light emitting diodes in the primary sides of the two optical coupling units are connected to the logic AND unit, and the anodes thereof are connected to the output pin corresponding to the bypass signal P;

[0016] The secondary sides of the two optical coupling units are respectively connected to the controllable ends of the corresponding controllable switches, and the body of the controllable switch is connected to the loop where the corresponding energy storage capacitor and the pull-in coil are located;

[0017] The two ends of the two energy storage capacitors are also connected to the two ends of the corresponding charging power source respectively.

[0018] Furthermore, the BOD overvoltage trigger branch includes a breakdown diode BOD and a corresponding controllable switch, one end of the breakdown diode BOD is connected to the DC side of the controlled object through a current limiting resistor, and the other end is connected to the controllable end of the controllable switch through a voltage-stabilizing diode, and the body of the controllable switch is connected to the loop where the energy storage capacitor and the pull-in coil are located corresponding to the main trigger branch or the auxiliary trigger branch.

[0019] Furthermore, the controllable switches are all thyristors.

[0020] Furthermore, the controlled object is configured as a submodule connected in series in an SVG system or an SSC system.

[0021] The beneficial technical effects of the present invention are:

[0022] 1. The composite bypass method of the present invention is used to generate a differential bypass signal through logic processing of the bypass control signal of the processor and the overvoltage signal generated by the overvoltage protection unit, and the differential bypass signal is uniformly given to the optocoupler unit, so that the loop of the bypass signal is simpler and the timing is more reliable.

[0023] 2. Connect an additional thyristor of the BOD overvoltage trigger branch in parallel at the position of the thyristor of the main trigger branch or the auxiliary trigger branch. In this way, even if the submodule loses the control power supply and causes the processor and the overvoltage detection unit to fail at the same time, the BOD overvoltage trigger branch can still provide closing current to the pickup coil to ensure that the faulty submodule is reliably bypassed, thereby improving the reliability of the operation of the series submodules;

[0024] 3. The device cost, heat dissipation requirements and device size of the BOD overvoltage trigger branch combined with the double-coil bypass switch are much smaller than those of the turning thyristor. In the early stage of configuring multi-stage bypass in the series sub-module system, there is the potential to reduce the cost and size of the sub-module. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of a double-coil bypass switch trigger circuit in the prior art;

[0026] Figure 2 It is a schematic diagram of the overall circuit structure of the present invention. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

[0028] like Figure 2As shown, the present invention provides a composite triggering method for a dual-coil bypass switch, including a main triggering branch, an auxiliary triggering branch and a BOD overvoltage triggering branch. The main triggering branch and the auxiliary triggering branch each include a respective pull-in coil, and both generate a triggering signal with the control signal N1 of the processor and / or the first overvoltage signal N2 of the controlled object, prompting the pull-in coil to be energized, thereby performing a bypass operation on the controlled object; the BOD overvoltage triggering branch shares the corresponding pull-in coil with the main triggering branch or the auxiliary triggering branch, and generates a triggering signal with the second overvoltage signal of the controlled object, prompting the pull-in coil to be energized, thereby performing a bypass operation on the controlled object. In this way, on the basis of the existing dual-coil bypass switch, a BOD overvoltage triggering branch is added. Even if the submodule loses the control power supply, causing the processor and the overvoltage detection unit to fail at the same time, so that the control signal N1 or the first overvoltage signal N2 cannot be generated normally, the BOD overvoltage triggering branch can still provide a closing current to the pull-in coil, ensuring that the faulty submodule is reliably bypassed, improving the reliability of the operation of the series submodule, and ensuring the safe operation of the entire system.

[0029] The details are as follows:

[0030] A dual-coil bypass switch usually includes a main trigger branch and an auxiliary trigger branch that are independent of each other. The energy storage capacitor in the branch is charged by a charging power supply in advance. When a bypass signal is received, the controllable switch is turned on, and the energy storage capacitor can release energy through the corresponding pull-in coil, closing the bypass switch contacts to achieve bypass operation.

[0031] In order to improve the anti-interference ability and ensure the stability of signal transmission, we add optical coupling units to both the main trigger branch and the auxiliary trigger branch, and also pre-set a high-level bypass signal P. When the control signal N1 is at a low level, it indicates that the processor sends a bypass command. When the first overvoltage signal N2 is at a low level, it indicates that the DC side voltage of the controlled object is greater than the first voltage threshold.

[0032] Then, the bypass signal N generated by the logic AND calculation of the control signal N1 and the first overvoltage signal N2 acts together with the bypass signal P on the optical coupling unit, and the optical coupling unit is used to trigger the corresponding controllable switch to turn on, so that the energy storage capacitor releases energy through the corresponding pull-in coil, thereby triggering the bypass. In this way, the bypass signal N is generated by performing a logic AND calculation on the control signal N1 and the first overvoltage signal N2, and then combined with the pre-set bypass signal P to act together with the optical coupling unit in a differential bypass command. Compared with a single-ended signal, it is easier to control the timing of high and low levels, and has better anti-interference ability, thereby reducing the risk of false triggering of the bypass command.

[0033] The BOD overvoltage trigger branch includes a breakdown diode BOD and its corresponding controllable switch, and shares the corresponding energy storage capacitor and pull-in coil with the main trigger branch or the auxiliary trigger branch. When the DC side voltage of the controlled object exceeds the second voltage threshold, the breakdown diode BOD is turned on, triggering the corresponding controllable switch to turn on, so that the energy storage capacitor releases energy through the corresponding pull-in coil, thereby triggering the bypass, wherein the second voltage threshold is greater than the first voltage threshold. In other words, on the basis of the existing double-coil bypass switch, there is no need to add additional energy storage capacitors and pull-in coils. When the first overvoltage signal N2 and / or the control signal N1 fail, the BOD overvoltage trigger branch can still trigger the bypass switch contacts to close and implement the bypass operation, thereby ensuring that the faulty submodule is reliably bypassed, improving the reliability of the operation of the series submodule, and ensuring the safe operation of the entire system.

[0034] The present invention also provides a composite triggering device based on the composite triggering method of the dual-coil bypass switch mentioned above, wherein the main triggering branch and the auxiliary triggering branch both include corresponding optocoupler units, controllable switches, energy storage capacitors, charging power supplies, and pull-in coils, wherein the cathodes of the light-emitting diodes in the primary sides of the two optocoupler units are connected to the output ends of the logic AND units, and the anodes thereof are connected to the output pins corresponding to the bypass signal P; the secondary sides of the two optocoupler units are respectively connected to the controllable ends of the corresponding controllable switches, and the body of the controllable switch is connected to the loop where the corresponding energy storage capacitor and the pull-in coil are located, so as to control the energy storage capacitor to release energy through the corresponding pull-in coil according to the bypass needs, and at the same time, the two ends of the two energy storage capacitors are also respectively connected to the two ends of the corresponding charging power supply, so as to facilitate the pre-energy storage of the energy storage capacitor.

[0035] The two input ends of the logic and unit are respectively connected to the overvoltage detection unit and the optical fiber control unit. The overvoltage detection unit is connected to the two ends of the DC side of the submodules in series in the controlled object, such as the SVG system or the SSC system, and is used to detect the overvoltage of the controlled object. Once the first voltage threshold is exceeded, the overvoltage detection unit will output the first overvoltage signal N2, and the optical fiber control unit is used to transmit the control signal N1 of the processor. Once the processor sends a bypass signal, the corresponding control signal N1 will be output through the optical fiber control unit, and the control signal N1 will be ANDed with the first overvoltage signal N2 through the logic and unit to generate a bypass signal. N, since when the control signal N1 or the first overvoltage signal N2 is at a low level, it indicates that the processor sends a bypass command or the overvoltage detection unit detects that the controlled object is overvoltage. Therefore, unless the control signal N1 and the first overvoltage signal N2 are both at a high level, the bypass signal N is always at a low level, and the bypass signal P is always at a high level. Therefore, as long as either the control signal N1 or the first overvoltage signal N2 is at a low level, the bypass signal N will be at a low level, and the optocoupler unit can trigger the controllable switches in the main trigger branch and the auxiliary trigger branch to turn on, thereby triggering the corresponding energy storage capacitor to release energy through the corresponding pull-in coil, triggering the bypass.

[0036] The BOD overvoltage trigger branch includes a breakdown diode BOD and a corresponding controllable switch. One end of the breakdown diode BOD is connected to the DC side of the controlled object through a current limiting resistor R3, and the other end is connected to the controllable end of the controllable switch through a voltage-stabilizing diode, that is, one end of the voltage-stabilizing diode is connected to the cathode of the controllable switch, and the other end is connected to the controllable end of the controllable switch through a current-limiting resistor R4. The body of the controllable switch is connected to the loop where the energy storage capacitor and the pull-in coil corresponding to the main trigger branch or the auxiliary trigger branch are located.

[0037] All controllable switches can be thyristors. The turned-on breakdown diode BOD or optocoupler unit generates a trigger current at the gate of the thyristor. The anode of the thyristor is connected to the pull-in coil, and the cathode of the thyristor is connected to the energy storage capacitor, thereby triggering the energy storage capacitor to release energy through the corresponding pull-in coil.

[0038] The cathodes of the other three groups of thyristors, the cathodes of the two groups of energy storage capacitors, and the negative input terminals of the two groups of charging power supplies can all be grounded on the circuit board, and the reference potential can be unified with the negative pole of the DC side of the sub-module. Therefore, the bypass command can turn on the thyristor and then generate a closing current on the corresponding pull-in coil.

[0039] The controlled object can be a submodule connected in series in an SVG system or an SSC system, or a submodule connected in series in a VSC-HVDC system, overcapacity voltage balancing, DC ice melting, or an energy-consuming device. The submodule can adopt a full-bridge topology or a half-bridge topology. In a full-bridge topology submodule, the switch contacts of the double-coil bypass switch are connected across the midpoints of the two bridge arms; in a half-bridge topology submodule, the switch contacts of the double-coil bypass switch are connected across the collector-emitter of the lower tube of the half-bridge. The broad series submodule topology includes but is not limited to the two typical topologies of full-bridge topology and half-bridge topology.

[0040] See attached Figure 2 , the working principle of the composite triggering method / composite triggering device of the double-coil bypass switch under different working conditions is further explained below, wherein the triggering parts of the main triggering branch and the auxiliary triggering branch are the control electric bypass triggering circuit 102, the main body of the double-coil bypass switch is the double-coil bypass switch 101, and the BOD overvoltage triggering branch is the BOD overvoltage bypass triggering circuit 103; the charging power supply, energy storage capacitor, pull-in coil, controllable switch, and optical coupling unit in the main triggering branch are respectively the charging power supply PS1, the energy storage capacitor C1, the pull-in coil L1, the thyristor SCR1, and the optical coupling unit OP1; the charging power supply, energy storage capacitor, pull-in coil, controllable switch, and optical coupling unit in the auxiliary triggering branch are respectively the charging power supply PS2, the energy storage capacitor C2, the pull-in coil L2, the thyristor SCR2, and the optical coupling unit OP2; the breakdown diode, the voltage regulator diode, and the controllable switch in the BOD overvoltage triggering branch are respectively the breakdown diode DB1, the voltage regulator diode DZ1, and the thyristor SCR3.

[0041] Working condition 1: When the bypass switch contact SW1 remains disconnected, the charging power supplies PS1 and PS2 charge the energy storage capacitors C1 and C2 independently through the charging current limiting resistors R1 and R2, respectively. The anode potential of the thyristor SCR1 is pulled up to the anode of the energy storage capacitor C1 by the pull-in coil L1, and the anode potentials of the thyristors SCR2 and SCR3 are simultaneously pulled up to the anode of the energy storage capacitor C2 by the pull-in coil L2. The cathodes of the energy storage capacitors C1, C2, thyristors SCR1, SCR2, and SCR3 are unified to the negative pole of the DC bus of the submodule by the BOD overvoltage trigger branch.

[0042] Working condition 2: Under normal working conditions of the submodule, the control circuit bypass trigger circuit 102 and the BOD overvoltage bypass trigger circuit 103 are not triggered, the bypass signal P and the bypass signal N are both kept high, the anode potentials of the thyristors SCR1, SCR2, and SCR3 are all pulled up to the anodes of their respective energy storage capacitors, the pull-in coils L1 and L2 will not generate closing current, and the bypass switch contact SW1 remains disconnected.

[0043] Working condition 3: A general fault occurs in the submodule and the logic unit U3 fails. Even if the control signal N1 and the first overvoltage signal N2 of the optical fiber control unit U1 and the overvoltage detection unit U2 are both set high, the failed logic unit U3 will pull the bypass signal N low, the primary sides of the optocoupler units OP1 and OP2 are forward-conducted, the thyristors SCR1 and SCR2 on the secondary sides are also turned on at the same time, the pull-in coils L1 and L2 will both generate closing current, and the bypass switch contact SW1 is connected.

[0044] Working condition 4: A general fault occurs in the submodule and a bypass command is received from the optical fiber. The optical fiber control unit U1 will pull down the control signal N1, and the overvoltage detection unit U2 that has not been triggered still keeps the first overvoltage signal N2 high. The logic AND unit U3 will pull down the bypass signal N, and the primary sides of the optocoupler units OP1 and OP2 are forward-conducted. The thyristors SCR1 and SCR2 on the secondary sides are also turned on at the same time. The pull-in coils L1 and L2 will both generate closing currents, and the bypass switch contact SW1 is connected.

[0045] Working condition 5: The submodule has a communication failure and cannot receive the PWM signal sent by the optical fiber. The submodule has not lost the control power supply. The faulty overvoltage submodule relies on the overvoltage detection unit U2 to pull down the first overvoltage signal N2. The optical fiber control unit U1 still keeps the control signal N1 high. The logic unit U3 will pull down the bypass signal N, and the primary sides of the optocoupler unit OP1 and the optocoupler unit OP2 are forward-conducted. The thyristors SCR1 and SCR2 on the secondary side are turned on at the same time. The pull-in coil L1 and the pull-in coil L2 will both generate a closing current, and the bypass switch contact SW1 is connected.

[0046] Working condition 6: The control power supply fails or the processor or overvoltage detection unit fails, causing U1 and U2 to fail to work normally. The primary sides of the optocoupler units OP1 and OP2 cannot be forward-conducted, and the thyristors SCR1 and SCR2 on the secondary sides cannot be turned on. The faulty overvoltage submodule will cause the breakdown diode DB1 to reach the overvoltage conduction threshold. The turned-on breakdown diode DB1 will generate a trigger current at the gate of the thyristor SCR3 through the voltage-stabilizing diode DZ1 and the trigger current-limiting resistor R4. The turned-on thyristor SCR3 will generate a closing current on the pull-in coil L2, and the bypass switch contact SW1 will be connected.

[0047] In summary, the present invention provides a composite triggering method and a composite triggering device for a dual-coil bypass switch. By setting a main triggering branch including an optocoupler unit and a logic AND unit, an auxiliary triggering branch and a BOD overvoltage triggering branch, the composite triggering of the dual-coil bypass switch is realized. Even if the processor or the overvoltage detection unit fails or even the faulty submodule loses control power, the BOD overvoltage triggering branch can still provide the faulty overvoltage submodule with a closing current for the suction coil, thereby ensuring that the faulty submodule is reliably bypassed and improving the reliability of the operation of the series submodules.

[0048] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to these embodiments without departing from the principles and essence of the present invention. Therefore, the scope of protection of the present invention is limited by the appended claims.

Claims

1. A composite triggering method for a dual-coil bypass switch, characterized in that: It includes a main trigger branch, an auxiliary trigger branch and a BOD overvoltage trigger branch. The main trigger branch and the auxiliary trigger branch each include a respective pull-in coil, and each uses a control signal N1 of a processor and / or a first overvoltage signal N2 of a controlled object as a trigger signal to energize the pull-in coil, thereby performing a bypass operation on the controlled object; The BOD overvoltage trigger branch shares a corresponding pull-in coil with the main trigger branch or the auxiliary trigger branch, and uses the second overvoltage signal of the controlled object as a trigger signal to energize the pull-in coil, thereby performing a bypass operation on the controlled object; A high-level bypass signal P is preset, when the control signal N1 is at a low level, it indicates that the processor issues a bypass command, and when the first overvoltage signal N2 is at a low level, it indicates that the DC side voltage of the controlled object is greater than a first voltage threshold; The main trigger branch and the auxiliary trigger branch each include a corresponding optical coupling unit, an energy storage capacitor, and a controllable switch; The control signal N1 and the first overvoltage signal N2 are logically ANDed to generate a bypass signal N, and the bypass signal N and the bypass signal P act together on the optical coupling unit, and the optical coupling unit is used to trigger the corresponding controllable switch to turn on, so that the energy storage capacitor releases energy through the corresponding pull-in coil, thereby triggering the bypass; The BOD overvoltage trigger branch includes a breakdown diode BOD and its corresponding controllable switch, and shares a corresponding energy storage capacitor and a pull-in coil with the main trigger branch or the auxiliary trigger branch. When the DC side voltage of the controlled object is greater than the second voltage threshold, the breakdown diode BOD is turned on, triggering the corresponding controllable switch to turn on, so that the energy storage capacitor releases energy through the corresponding pull-in coil, thereby triggering the bypass.

2. The compound triggering method of the double-coil bypass switch according to claim 1, characterized in that: The second voltage threshold is greater than the first voltage threshold.

3. A composite triggering device of the composite triggering method of the double-coil bypass switch according to claim 1, characterized in that: The main trigger branch and the auxiliary trigger branch also include corresponding optical coupling units, controllable switches, energy storage capacitors, and charging power supplies; The cathodes of the light emitting diodes in the primary sides of the two optical coupling units are connected to the logic AND unit, and the anodes thereof are connected to the output pin corresponding to the bypass signal P; The secondary sides of the two optical coupling units are respectively connected to the controllable ends of the corresponding controllable switches, and the body of the controllable switch is connected to the loop where the corresponding energy storage capacitor and the pull-in coil are located; The two ends of the two energy storage capacitors are also connected to the two ends of the corresponding charging power source respectively.

4. The composite trigger device of the double-coil bypass switch according to claim 3 is characterized in that: The BOD overvoltage trigger branch includes a breakdown diode BOD and a corresponding controllable switch, one end of the breakdown diode BOD is connected to the DC side of the controlled object through a current limiting resistor, and the other end is connected to the controllable end of the controllable switch through a voltage-stabilizing diode, and the body of the controllable switch is connected to the loop where the energy storage capacitor and the pull-in coil corresponding to the main trigger branch or the auxiliary trigger branch are located.

5. The composite trigger device of the double-coil bypass switch according to claim 4, characterized in that: The controllable switches are all thyristors.

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