Triac overvoltage protection circuit and solid-state circuit breaker

Abstract

The present application belongs to the technical field of power electronics. Disclosed are a TRIAC overvoltage protection circuit and a solid-state circuit breaker. The overvoltage protection circuit comprises a TRIAC, a drive circuit of the TRIAC, and a piezoresistor, wherein the drive circuit comprises a drive resistor and a drive capacitor, the drive resistor and the drive capacitor are connected in series, one end of the drive capacitor is connected to a gate electrode of the TRIAC, another end of the drive resistor is connected to the piezoresistor, and another end of the piezoresistor is connected to a first power end of the TRIAC. The present solution can achieve low costs and a small volume of a solid-state circuit breaker, and can reduce the difference between a clamping voltage and a bus voltage.

Description

A bidirectional thyristor overvoltage protection circuit and a solid-state circuit breaker Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a bidirectional thyristor overvoltage protection circuit, a solid-state circuit breaker, and an experimental circuit for overvoltage protection of the solid-state circuit breaker. Background Technology

[0002] Solid-state circuit breakers (SSDs) are protective devices for power systems. They use semiconductor devices to detect current and can quickly disconnect power in case of overload or short circuit. Overvoltage protection methods for SSDs include the varistor method and the active switch overvoltage protection method. The varistor method directly connects a varistor in parallel with the SSD, relying on the varistor's resistance changing with voltage to achieve overvoltage protection. However, this method results in a significant difference between the clamping voltage and the bus voltage, causing a reduction in the SSD's rated voltage.

[0003] The active switch overvoltage protection method uses a controllable switch connected in series with a varistor, which is then connected in parallel with a solid-state circuit breaker for overvoltage protection. When overvoltage protection is needed, the switch is turned on, and the varistor operates. When protection is not needed, the switch is turned off, and the varistor is not connected to the bus. Compared to the varistor method, this scheme ensures that the varistor in the circuit is not broken down by the bus voltage when it is not operating, thus reducing the difference between the clamping voltage and the bus voltage, and thereby increasing the bus voltage of the solid-state circuit breaker. However, this scheme results in a larger switch size and higher driving cost. Summary of the Invention

[0004] To address the problems existing in the prior art, this solution proposes a bidirectional thyristor overvoltage protection circuit and a solid-state circuit breaker, which can reduce the size and cost of the switch and decrease the difference between the clamping voltage and the bus voltage.

[0005] According to a first aspect of this application, a bidirectional thyristor overvoltage protection circuit is provided, comprising a bidirectional thyristor, a driving circuit for the bidirectional thyristor, and a varistor, wherein the driving circuit includes a driving resistor and a driving capacitor connected in series, the other end of the driving capacitor is connected to the gate of the bidirectional thyristor, the other end of the driving resistor is connected to the varistor, and the other end of the varistor is connected to the first power terminal of the bidirectional thyristor.

[0006] Optionally, in the bidirectional thyristor overvoltage protection circuit provided in this application, the resistance value of the drive resistor is calculated using the following formula:

[0007] Where R1 is the resistance value of the driving resistor, I GTM V is the maximum gate trigger current of a bidirectional thyristor. DC This refers to the bus voltage of the solid-state circuit breaker operating system.

[0008] Optionally, in the bidirectional thyristor overvoltage protection circuit provided in this application, the capacitance value of the driving capacitor is calculated using the following formula:

[0009] Where C1 is the capacitance of the driving capacitor, Δt is the conduction time of the bidirectional thyristor, and I... GTM and I GT These are the maximum and minimum gate trigger currents of the bidirectional thyristor, respectively.

[0010] Optionally, in the bidirectional thyristor overvoltage protection circuit provided in this application, the varistor is selected based on the relationship between the leakage current of the varistor and the bus voltage, so that the leakage current of the varistor is less than the holding current of the bidirectional thyristor.

[0011] According to a second aspect of this application, a solid-state circuit breaker is provided, comprising: a bidirectional thyristor overvoltage protection circuit as described in the first aspect of this application and a solid-state circuit breaker main switch, wherein a common terminal of a varistor and a drive resistor is connected to one end of the solid-state circuit breaker main switch; and a second power terminal of the bidirectional thyristor is connected to the other end of the solid-state circuit breaker main switch.

[0012] Optionally, in the solid-state circuit breaker provided in this application, when the main switch of the solid-state circuit breaker is turned off, the voltage change across the main switch causes a momentary current to be generated in the drive circuit, and the first and second power terminals of the bidirectional thyristor are bidirectionally turned on. The varistor is connected in parallel with the main switch of the solid-state circuit breaker through the turned-on bidirectional thyristor.

[0013] Optionally, in the solid-state circuit breaker provided in this application, the varistor is used to limit and absorb the overvoltage across the main switch of the solid-state circuit breaker. When the current flowing through the varistor is less than the holding current of the bidirectional thyristor, the bidirectional thyristor turns off automatically.

[0014] Optionally, in the solid-state circuit breaker provided in this application, after the main switch of the solid-state circuit breaker is turned off, the voltage across the main switch of the solid-state circuit breaker changes from zero voltage to peak voltage within 200ns, and the peak voltage of the solid-state circuit breaker is less than 1.5 times the bus voltage of the solid-state circuit breaker operating system.

[0015] According to a third aspect of this application, an overvoltage protection experimental circuit for a solid-state circuit breaker is provided, comprising: a DC power supply, a solid-state circuit breaker as described in the second aspect of this application, a line inductor, a load, and a fault switch device. The fault switch device includes a fault pulse generator, a fault drive, and a fault switch connected in series. The fault switch device is connected in parallel across the load. The common terminal of the varistor and the drive resistor is connected to one end of the main switch of the solid-state circuit breaker and then connected to the positive terminal of the DC power supply. The second power terminal of the bidirectional thyristor is connected to the other end of the main switch of the solid-state circuit breaker and then connected to the line inductor. The other end of the line inductor is connected to the fault switch device and the load. The other end of the fault switch device and the load is connected to the negative terminal of the DC power supply.

[0016] Optionally, in the overvoltage protection experimental circuit of the solid-state circuit breaker provided in this application, when the fault pulse generator sends a fault pulse, the fault pulse causes the fault switch to turn on through the fault drive, and the fault current rises linearly. When the fault current rises to the fault detection threshold current, the main switch of the solid-state circuit breaker turns off.

[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0019] Figure 1 shows a connection diagram of a bidirectional thyristor overvoltage protection circuit according to an embodiment of this application;

[0020] Figure 2 shows a schematic diagram of the circuit structure of a solid-state circuit breaker according to an embodiment of this application;

[0021] Figure 3 shows a schematic diagram of the connection of a solid-state circuit breaker in a DC system;

[0022] Figure 4 shows a hardware schematic diagram of an overvoltage protection experimental circuit for a solid-state circuit breaker according to an embodiment of this application;

[0023] Figure 5 shows the voltage and current waveforms of a solid-state circuit breaker according to an embodiment of this application;

[0024] Figure 6 shows a power terminal voltage waveform of a bidirectional thyristor according to an embodiment of this application. Detailed Implementation

[0025] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0026] Figure 1 shows a connection diagram of a bidirectional thyristor overvoltage protection circuit according to an embodiment of this application. As shown in Figure 1, the bidirectional thyristor overvoltage protection circuit includes a bidirectional thyristor S, a driving circuit for the bidirectional thyristor, and a varistor MOV. The bidirectional thyristor S has three terminals: a first power terminal T1, a second power terminal T2, and a gate G. The driving circuit includes a driving resistor R and a driving capacitor C, which are connected in series. The other end of the driving capacitor C is connected to the gate G of the bidirectional thyristor, and the other end of the driving resistor R is connected to the varistor MOV. The other end of the varistor MOV is connected to the first power terminal T1 of the bidirectional thyristor. By utilizing the bidirectional conduction of the bidirectional thyristor, the required switches and switch driving circuits of the system can be reduced.

[0027] The triac S can be controlled during both positive and negative half-cycles of alternating current. Its conduction state is triggered by the gate; applying a small trigger current to the gate G changes the triac from the off state to the on state. Once triggered, the triac remains on for both half-cycles of the alternating current until the current drops to a certain level (called the holding current), causing it to turn off again. By adjusting the signal on the gate, the timing of the triac's conduction can be controlled, thereby achieving regulation and control of the alternating current.

[0028] To ensure smooth conduction of the bidirectional thyristor S without overload degradation of the gate G, the drive resistor R and drive capacitor C need to be designed. According to one embodiment of this application, the resistance value of the drive resistor R can be calculated using the following formula:

[0029] Where R1 is the resistance value of the driving resistor R, I GTM V is the maximum gate trigger current of a bidirectional thyristor. DC This refers to the bus voltage of the solid-state circuit breaker operating system.

[0030] The capacitance value of the driving capacitor C can be calculated using the following formula:

[0031] Where C1 is the capacitance of the driving capacitor, Δt is the conduction time of the bidirectional thyristor, and I... GTM and I GTThese are the maximum and minimum gate trigger currents of the bidirectional thyristor, respectively.

[0032] Among them, the maximum gate trigger current I of the bidirectional thyristor GTM and minimum trigger current I GT All of these can be obtained from the datasheet of the bidirectional thyristor S.

[0033] In one embodiment of this application, a bidirectional thyristor overvoltage protection circuit is connected to the main switch of a solid-state circuit breaker to achieve overvoltage protection for the solid-state circuit breaker. Figure 2 shows a schematic diagram of the circuit structure of a solid-state circuit breaker according to an embodiment of this application. As shown in Figure 2, the solid-state circuit breaker includes a bidirectional thyristor overvoltage protection circuit and a solid-state circuit breaker main switch. The common terminal of the varistor MOV and the drive resistor R is connected to one end of the solid-state circuit breaker main switch; the second power terminal T2 of the bidirectional thyristor S is connected to the other end of the solid-state circuit breaker main switch.

[0034] The main switch of a solid-state circuit breaker is a semiconductor device such as a transistor or a silicon controlled rectifier (SCR), used to control the opening and closing of the circuit based on detected abnormal current or voltage signals. During the transient state of the main switch's turn-off, the voltage change across the main switch generates a transient current. This transient current flows through the gate G of the bidirectional SCR, causing the first power terminal T1 and the second power terminal T2 of the SCR to conduct bidirectionally. The conducting bidirectional SCR enables the parallel connection of a varistor MOV with the main switch of the solid-state circuit breaker. The varistor MOV absorbs and limits overvoltage. Therefore, the overvoltage when the main switch of the solid-state circuit breaker is turned off will be limited and absorbed by the varistor MOV connected in parallel.

[0035] After the varistor MOV has completed the limitation and absorption of overvoltage, the current flowing through the varistor MOV will decrease to less than the holding current of the bidirectional thyristor S, thereby causing the bidirectional thyristor S to turn off automatically.

[0036] To ensure the self-turn-off of the triac S, i.e., to ensure that the leakage current of the MOV is less than the holding current of the triac S under the system bus voltage, the varistor MOV can be selected according to the relationship between the leakage current of the varistor MOV and the system bus voltage given in the varistor MOV datasheet. The holding current can be obtained from the datasheet of the triac S.

[0037] The above technical solution can effectively avoid false triggering of bidirectional thyristors under normal voltage conditions, and absorb and disperse excess voltage when overvoltage is detected.

[0038] This solution fully considers factors such as turn-on speed, cost, and size, enabling the bidirectional thyristor overvoltage protection circuit to achieve the goal of low cost, small size, and fast turn-on of solid-state circuit breakers by utilizing bidirectional thyristors and varistors.

[0039] Figure 3 shows a schematic diagram of the solid-state circuit breaker connection in a DC system. To verify the overvoltage protection performance of the bidirectional thyristor overvoltage protection circuit, this embodiment of the application uses the above-mentioned bidirectional thyristor overvoltage protection circuit and establishes an overvoltage protection experimental platform based on the DC system shown in Figure 3 to conduct overvoltage protection experiments.

[0040] Figure 4 shows a hardware schematic diagram of an overvoltage protection experimental circuit for a solid-state circuit breaker according to an embodiment of this application. As shown in Figure 4, the experimental platform includes a line inductor L. line Load R L The fault switchgear consists of a fault pulse generator, a fault drive, and a fault switch, all connected in series. A bidirectional thyristor overvoltage protection circuit is located on the back of the solid-state circuit breaker. The fault switchgear is connected in parallel to the load R. L On both sides, the common terminal connecting the varistor MOV and the drive resistor R is connected to one end of the solid-state circuit breaker's main switch, and then connected to the positive terminal of the DC power supply. The second power terminal T2 of the bidirectional thyristor is connected to the other end of the solid-state circuit breaker's main switch, and then connected to the line inductor L. line Line inductance L line The other end connects to the fault switch and the load R L The other end of the fault switch and the load is connected to the negative terminal of the DC power supply. Table 1 shows the hardware parameters of this overvoltage protection experimental platform.

[0041] Table 1 Hardware parameters of the overvoltage protection experimental platform

[0042] In the overvoltage protection experiment, power is first supplied to the fault pulse generator and the drive and control circuits of the solid-state circuit breaker itself in the system, and the solid-state circuit breaker is ensured to be in the off state.

[0043] Closing the solid-state circuit breaker causes the system load R to... L Current begins to flow. Figure 5 shows the voltage and current waveforms of a solid-state circuit breaker according to an embodiment of this application. As shown in Figure 5, at time t1, a single fault pulse is generated by a fault pulse generator. This pulse drives the fault simulation thyristor (fault switch) in the fault switching device to conduct, and simultaneously, due to the line inductance L... line The fault current begins to rise linearly with time. At time t2, the fault current rises to the fault detection threshold current of 100A, so the main switch of the solid-state circuit breaker closes. In this embodiment, the bus voltage is 600V, and it can be seen that the peak voltage of the solid-state circuit breaker is 900V. Within the approximately 200ns turn-on time, the peak voltage is quickly limited to within 900V, and the peak voltage is limited to within 1.5V of the bus voltage.

[0044] As the voltage across the main switch of the solid-state circuit breaker increases, a pulse current flows through the drive circuit of the bidirectional thyristor S, causing S to conduct and the fault current to transfer to the bidirectional thyristor overvoltage protection circuit. The time period from t2 to t3 is the process of the varistor MOV clamping the voltage and absorbing system energy. At time t3, the leakage current of the varistor MOV will be less than the holding current of the bidirectional thyristor S, therefore, S will turn off automatically.

[0045] Figure 6 shows the power terminal voltage waveform of a bidirectional thyristor according to an embodiment of this application. As shown in Figure 6, after the bidirectional thyristor S turns off, the voltage at the first power terminal T1 and the second power terminal T2 of the bidirectional thyristor gradually recovers to the blocking state voltage of 55V. Therefore, the bidirectional thyristor S successfully turns off.

[0046] This application uses a bidirectional thyristor instead of other switches such as thyristors connected in series with a varistor. Only a current flowing in any direction is needed between the gate and power terminal of the bidirectional thyristor for it to conduct bidirectionally. Therefore, compared to traditional solutions, this significantly reduces the required number of switches and their driving circuitry.

[0047] This application, through the design of a suitable matching drive, achieves low cost and small size while ensuring a low clamping voltage and bus voltage difference. This makes the peak voltage of the solid-state circuit breaker less than 1.5 times the bus voltage of the solid-state circuit breaker operating system, and it can change from zero voltage to peak voltage within 200ns, resulting in fast turn-on speed.

[0048] In summary, the bidirectional thyristor overvoltage protection circuit and solid-state circuit breaker provided in this application can achieve low-cost, small-size solid-state circuit breaker overvoltage protection with a low difference between clamping voltage and bus voltage.

[0049] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0050] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more aspects, various features of this application are sometimes grouped together in a single embodiment, figure, or description thereof in the foregoing description of exemplary embodiments of this application. However, this approach to disclosure should not be construed as reflecting an intention that the claimed application requires more features than expressly recited in each claim. Rather, as reflected in the following claims, aspects consist of fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0051] As used herein, unless otherwise specified, the use of ordinal numbers such as “first,” “second,” “third,” etc., to describe ordinary objects merely indicates different instances of similar objects and is not intended to imply that the objects being described must have a given order in time, space, ordering, or any other manner.

[0052] Although this application has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of this application described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and edibility purposes, and not for the purpose of interpreting or limiting the subject matter of this application.

[0053] Therefore, many modifications and alterations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure made herein is illustrative rather than restrictive, and the scope of this application is defined by the appended claims.

Claims

1. A bidirectional thyristor overvoltage protection circuit, characterized in that, The device includes a bidirectional thyristor, a driving circuit for the bidirectional thyristor, and a varistor. The driving circuit includes a driving resistor and a driving capacitor connected in series. The other end of the driving capacitor is connected to the gate of the bidirectional thyristor. The other end of the driving resistor is connected to the varistor. The other end of the varistor is connected to the first power terminal of the bidirectional thyristor.

2. The bidirectional thyristor overvoltage protection circuit according to claim 1, characterized in that, The resistance value of the driving resistor is calculated using the following formula: Where R1 is the resistance value of the driving resistor, I GTM V is the maximum gate trigger current of the bidirectional thyristor. DC This refers to the bus voltage of the solid-state circuit breaker operating system.

3. The bidirectional thyristor overvoltage protection circuit according to claim 1, characterized in that, The capacitance value of the driving capacitor is calculated using the following formula: Where C1 is the capacitance value of the driving capacitor, Δt is the conduction time of the bidirectional thyristor, and I GTM and I GT These are the maximum and minimum gate trigger currents of the bidirectional thyristor, respectively.

4. The bidirectional thyristor overvoltage protection circuit according to claim 1, characterized in that, The varistor is selected based on the relationship between the leakage current of the varistor and the bus voltage, so that the leakage current of the varistor is less than the holding current of the bidirectional thyristor.

5. A solid-state circuit breaker, characterized in that, Includes a bidirectional thyristor overvoltage protection circuit and a solid-state circuit breaker main switch as described in any one of claims 1-4, wherein the common terminal of the varistor and the driving resistor is connected to one end of the solid-state circuit breaker main switch; and the second power terminal of the bidirectional thyristor is connected to the other end of the solid-state circuit breaker main switch.

6. The solid-state circuit breaker according to claim 5, characterized in that, When the main switch of the solid-state circuit breaker is turned off, the voltage change across the main switch causes a transient current to be generated in the drive circuit. The first and second power terminals of the bidirectional thyristor are bidirectionally turned on, and the varistor is connected in parallel with the main switch of the solid-state circuit breaker through the turned-on bidirectional thyristor.

7. The solid-state circuit breaker according to claim 6, characterized in that, The varistor is used to limit and absorb overvoltage across the main switch of the solid-state circuit breaker. When the current flowing through the varistor is less than the holding current of the bidirectional thyristor, the bidirectional thyristor turns off automatically.

8. The solid-state circuit breaker according to claim 6, characterized in that, After the main switch of the solid-state circuit breaker is turned off, the voltage across the main switch of the solid-state circuit breaker changes from zero voltage to peak voltage within 200ns. The peak voltage of the solid-state circuit breaker is less than 1.5 times the bus voltage of the solid-state circuit breaker operating system.

9. An overvoltage protection experimental circuit for a solid-state circuit breaker, characterized in that, include: The system comprises a DC power supply, a solid-state circuit breaker as described in any one of claims 5-8, a line inductor, a load, and a fault switch device, wherein the fault switch device includes a fault pulse generator, a fault drive, and a fault switch connected in series; the fault switch device is connected in parallel across the load; the common terminal of the varistor and the drive resistor is connected to one end of the main switch of the solid-state circuit breaker and then connected to the positive terminal of the DC power supply; the second power terminal of the bidirectional thyristor is connected to the other end of the main switch of the solid-state circuit breaker and then connected to the line inductor; the other end of the line inductor is connected to the fault switch device and the load; and the other ends of the fault switch device and the load are connected to the negative terminal of the DC power supply.

10. The overvoltage protection experimental circuit for a solid-state circuit breaker according to claim 9, characterized in that, When the fault pulse generator emits a fault pulse, the fault pulse causes the fault switch to turn on through the fault drive, and the fault current rises linearly. When the fault current rises to the fault detection threshold current, the main switch of the solid-state circuit breaker turns off.

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