Bidirectional silicon controlled rectifier overvoltage protection circuit and solid-state circuit breaker

Abstract

The invention discloses a bidirectional silicon controlled rectifier overvoltage protection circuit and a solid-state circuit breaker, and belongs to the technical field of power electronics, the overvoltage protection circuit comprises a bidirectional silicon controlled rectifier, a driving circuit of the bidirectional silicon controlled rectifier and a piezoresistor, the driving circuit comprises a driving resistor and a driving capacitor, and the driving resistor and the driving capacitor are connected in series. The other end of the driving capacitor is connected with the gate pole of the bidirectional silicon controlled rectifier, the other end of the driving resistor is connected with the piezoresistor, and the other end of the piezoresistor is connected with the first power end of the bidirectional silicon controlled rectifier. According to the scheme, low-cost, small-size, low-clamp-voltage and low-bus-voltage-difference overvoltage protection can be realized for the solid-state circuit breaker.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a bidirectional thyristor overvoltage protection circuit, a solid-state circuit breaker and an overvoltage protection experimental circuit of the solid-state circuit breaker. Background Art

[0002] A solid-state circuit breaker is a protective device for an electric power system that uses semiconductor devices to detect current and can quickly cut off power in the event of a current overload or short circuit. Overvoltage protection methods for solid-state circuit breakers include the varistor method and the active switch overvoltage protection method. Among them, the varistor method directly uses a varistor in parallel with a solid-state circuit breaker to achieve overvoltage protection by relying on the characteristic that the resistance of the varistor changes with voltage. The clamping voltage of this solution is significantly different from the bus voltage, resulting in a reduction in the rated voltage of the solid-state circuit breaker.

[0003] The active switch overvoltage protection method is to perform overvoltage protection by connecting a controllable switch in series with a varistor and then in parallel with a solid-state circuit breaker. When overvoltage protection is required, the switch is turned on and the varistor works. When protection is not required, the switch is turned off and the varistor is not connected to the bus. Compared with the varistor method, this solution can ensure that the varistor in the circuit is not broken down by the bus voltage when not working, so it can reduce the difference between the clamping voltage and the bus voltage, thereby increasing the bus voltage of the solid-state circuit breaker. However, the switch of this solution is larger in size and has a higher driving cost. Summary of the invention

[0004] In order to solve 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 reduce the difference between the clamping voltage and the bus voltage.

[0005] According to a first aspect of the present invention, a bidirectional thyristor overvoltage protection circuit is provided, comprising a bidirectional thyristor, a driving circuit of the bidirectional thyristor and a varistor, wherein the driving circuit comprises a driving resistor and a driving capacitor, the driving resistor and the driving capacitor are 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 end of the bidirectional thyristor.

[0006] The above technical solution utilizes the bidirectional conduction of the bidirectional thyristor, which can reduce the switches and switch driving circuits required by the system.

[0007] Optionally, in the bidirectional thyristor overvoltage protection circuit provided by the present invention, the resistance of the driving resistor is calculated by the following formula: Among them, R 1 is the resistance of the driving resistor, I GTM is the maximum gate trigger current of the bidirectional thyristor, VDC It is the bus voltage of the solid-state circuit breaker working system.

[0008] Optionally, in the bidirectional thyristor overvoltage protection circuit provided by the present invention, the capacitance value of the driving capacitor is calculated by the following formula: Among them, C 1 is the capacitance of the driving capacitor, Δt is the conduction time of the bidirectional thyristor, I GTM and I GT They are the maximum gate trigger current and minimum gate trigger current of the bidirectional thyristor respectively.

[0009] Optionally, in the bidirectional thyristor overvoltage protection circuit provided by the present invention, the varistor is selected according to the relationship between the leakage current of the varistor and the bus voltage, so that the leakage current of the varistor is smaller than the holding current of the bidirectional thyristor.

[0010] The above technical solution can effectively avoid false triggering of the bidirectional thyristor under normal voltage conditions, and absorb and disperse excess voltage when overvoltage is detected.

[0011] According to a second aspect of the present invention, a solid-state circuit breaker is provided, comprising: a bidirectional thyristor overvoltage protection circuit and a solid-state circuit breaker main switch as described in the first aspect of the present invention, wherein a common end where the varistor and the driving resistor are connected is connected to one end of the solid-state circuit breaker main switch; and a second power end 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 by the present invention, when the main switch of the solid-state circuit breaker is turned off, the voltage change at both ends of the main switch of the solid-state circuit breaker causes an instantaneous current to be generated in the drive circuit, the first power end and the second power end of the bidirectional thyristor are bidirectionally conductive, and the varistor is connected in parallel with the main switch of the solid-state circuit breaker through the conductive bidirectional thyristor.

[0013] Optionally, in the solid-state circuit breaker provided by the present invention, a varistor is used to limit and absorb overvoltage at both ends of the main switch of the solid-state circuit breaker, and when the current flowing through the varistor is less than the holding current of the bidirectional thyristor, the bidirectional thyristor is self-turned off.

[0014] Optionally, in the solid-state circuit breaker provided by the present invention, 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 working system.

[0015] According to a third aspect of the present invention, 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 the present invention, a line inductor, a load, and a fault switch device, wherein the fault switch device comprises a fault pulse generator, a fault drive, and a fault switch connected in series in sequence; the fault switch device is connected in parallel on both sides of the load, a common end of the varistor and the drive resistor is connected to one end of the solid-state circuit breaker main switch and then connected to the positive electrode of the DC power supply, a second power end of the bidirectional thyristor is connected to the other end of the solid-state circuit breaker main switch 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 electrode of the DC power supply.

[0016] Optionally, in the overvoltage protection experimental circuit of the solid-state circuit breaker provided by the present invention, when the fault pulse generator sends a fault pulse, the fault pulse causes the fault switch to be turned 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 is turned off.

[0017] The present invention uses bidirectional thyristors instead of other switches such as thyristors in series with varistor. Only current in any direction needs to flow between the gate and the power end of the bidirectional thyristor, and the bidirectional thyristor can conduct in both directions. Therefore, compared with the traditional solution, the required switches and switch driving circuits are significantly reduced.

[0018] The present invention can achieve low cost and small size by designing a suitable supporting drive, while ensuring a low clamping voltage and a bus voltage difference, so that the peak voltage of the solid-state circuit breaker is within 1.5 times the bus voltage of the solid-state circuit breaker working system, and can change from zero voltage to peak voltage within 200ns, with a fast opening speed.

[0019] In summary, the bidirectional thyristor overvoltage protection circuit and solid-state circuit breaker provided by the present invention can realize solid-state circuit breaker overvoltage protection with low cost, small size, and low clamping voltage and bus voltage difference.

[0020] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings: Figure 1 A connection diagram of a bidirectional thyristor overvoltage protection circuit according to an embodiment of the present invention is shown; Figure 2 A schematic diagram of a circuit structure of a solid-state circuit breaker according to an embodiment of the present invention is shown; Figure 3 A schematic diagram showing the connection of a solid-state circuit breaker in a DC system is shown; Figure 4 A hardware schematic diagram of an overvoltage protection experimental circuit of a solid-state circuit breaker according to an embodiment of the present invention is shown; Figure 5 shows a voltage and current waveform diagram of a solid-state circuit breaker according to an embodiment of the present invention; Figure 6 A power terminal voltage waveform diagram of a bidirectional thyristor according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0022] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0023] Figure 1 FIG. 2 shows a connection diagram of a bidirectional thyristor overvoltage protection circuit according to an embodiment of the present invention. Figure 1 As shown, the bidirectional thyristor overvoltage protection circuit includes a bidirectional thyristor S, a bidirectional thyristor driving circuit and a varistor MOV. The bidirectional thyristor S has three terminals, namely 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, the driving resistor R and the driving capacitor C are connected in series, the other end of the driving capacitor C is connected to the gate G of the bidirectional thyristor, the other end of the driving resistor R is connected to the varistor MOV, and the other end of the varistor MOV is connected to the first power terminal T1 of the bidirectional thyristor.

[0024] Among them, the bidirectional thyristor S can be controlled in the positive and negative half-cycles of the alternating current. Its conduction state is triggered by the gate. A small trigger current is applied to the gate G, and the bidirectional thyristor can change from the off state to the on state. Once triggered, the bidirectional thyristor will remain in the on state in the two 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 bidirectional thyristor's conduction can be controlled, thereby achieving the regulation and control of the alternating current.

[0025] In order to ensure that the bidirectional thyristor S is smoothly turned on and does not cause overload degradation to the gate G, the driving resistor R and the driving capacitor C need to be designed. According to one embodiment of the present invention, the resistance value of the driving resistor R can be calculated by the following formula: Among them, R 1 is the resistance of the driving resistor R, I GTM is the maximum gate trigger current of the bidirectional thyristor, V DC It is the bus voltage of the solid-state circuit breaker working system.

[0026] The capacitance value of the driving capacitor C can be calculated by the following formula: Among them, C 1 is the capacitance of the driving capacitor, Δt is the conduction time of the bidirectional thyristor, I GTM and I GT They are the maximum gate trigger current and minimum gate trigger current of the bidirectional thyristor respectively.

[0027] Among them, the maximum gate trigger current of the bidirectional thyristor is I GTM and minimum trigger current I GT Both can be obtained from the data sheet of the bidirectional thyristor S.

[0028] In one embodiment of the present invention, a bidirectional thyristor overvoltage protection circuit is connected to a main switch of a solid-state circuit breaker to implement overvoltage protection for the solid-state circuit breaker. Figure 2 FIG. 2 shows a circuit structure diagram of a solid-state circuit breaker according to an embodiment of the present invention. Figure 2 As shown, the solid-state circuit breaker includes a bidirectional thyristor overvoltage protection circuit and a solid-state circuit breaker main switch, the common end of the varistor MOV and the driving resistor R is connected to one end of the solid-state circuit breaker main switch; the second power end T2 of the bidirectional thyristor S is connected to the other end of the solid-state circuit breaker main switch.

[0029] The main switch of the solid-state circuit breaker is a semiconductor device such as a transistor or a thyristor, which is used to control the opening and closing of the circuit according to the detected current or voltage abnormality signal. When the main switch of the solid-state circuit breaker is turned off, the voltage change at both ends of the main switch will generate a transient current. This transient current flows through the gate G of the bidirectional thyristor, making the first power terminal T1 and the second power terminal T2 of the bidirectional thyristor S bidirectionally conductive. The turned-on bidirectional thyristor S realizes the parallel connection of the varistor MOV and the main switch of the solid-state circuit breaker, and the varistor MOV absorbs and limits the overvoltage. Therefore, the overvoltage when the main switch of the solid-state circuit breaker is turned off will be limited and absorbed by the parallel varistor MOV.

[0030] After the varistor MOV completes limiting and absorbing the overvoltage, the current flowing through the varistor MOV will be reduced to less than the holding current of the bidirectional thyristor S, thereby causing the bidirectional thyristor S to self-turn off.

[0031] In order to ensure the self-shutdown of the bidirectional thyristor S, that is, to ensure that the leakage current of the MOV is less than the holding current of the bidirectional thyristor 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 data sheet of the varistor MOV. The holding current can be obtained in the data sheet of the bidirectional thyristor S.

[0032] This solution fully considers the factors of opening speed, cost and volume, so that the bidirectional thyristor overvoltage protection circuit can achieve the purpose of low-cost, small-volume and fast opening of solid-state circuit breakers using bidirectional thyristors and varistors.

[0033] Figure 3 The figure shows a schematic diagram of the connection of a solid-state circuit breaker in a DC system. In order to verify the overvoltage protection performance of the bidirectional thyristor overvoltage protection circuit, the embodiment of the present invention adopts the above-mentioned bidirectional thyristor overvoltage protection circuit. Figure 3 The DC system shown establishes an overvoltage protection experimental platform for conducting overvoltage protection experiments.

[0034] Figure 4 FIG. 1 is a hardware schematic diagram of an overvoltage protection experimental circuit of a solid-state circuit breaker according to an embodiment of the present invention. Figure 4 As shown, the experimental platform includes a line inductor L line 、Load R L , fault switch device, the fault switch device includes a fault pulse generator, a fault driver and a fault switch, the three are connected in series in sequence, and the bidirectional thyristor overvoltage protection circuit is set on the back of the solid-state circuit breaker. The fault switch device is connected in parallel with the load R L On both sides, the common end of the varistor MOV and the driving resistor R is connected to one end of the solid-state circuit breaker main switch and then connected to the positive pole of the DC power supply. The second power end T2 of the bidirectional thyristor is connected to the other end of the solid-state circuit breaker main switch and then connected to the line inductor L. line , line inductance L line The other end is connected to the fault switch device and the load R L ; The other end of the fault switch device and the load is connected to the negative pole of the DC power supply. Table 1 shows the hardware parameters of the overvoltage protection experimental platform Table 1 Hardware parameters of overvoltage protection experimental platform In the overvoltage protection experiment, firstly, the fault pulse generator in the system and the driving and control circuits of the solid-state circuit breaker itself are powered, and it is ensured that the solid-state circuit breaker is in the off state.

[0035] Close the solid-state circuit breaker to make the system load R L Current begins to flow. Figure 5 FIG. 2 shows a voltage and current waveform diagram of a solid-state circuit breaker according to an embodiment of the present invention. Figure 5 As shown, at t 1 At this moment, a single fault pulse is sent out through the fault pulse generator. This pulse turns on the fault simulation thyristor (fault switch) through the driver in the fault switch device. At the same time, due to the line inductance L line The fault current begins to increase linearly with time. 2 At this moment, the fault current rises to the fault detection threshold current of 100A, so the main switch of the solid-state circuit breaker is closed. In this embodiment, the bus voltage is 600V. It can be seen that the peak voltage of the solid-state circuit breaker is 900V. Within the opening time of about 200ns, the peak voltage is quickly limited to within 900V, and the peak voltage is limited to within 1.5V times the bus voltage.

[0036] As the voltage across the main switch of the solid-state circuit breaker increases, a pulse current flows through the driving circuit of the bidirectional thyristor S, so the bidirectional thyristor S is turned on and the fault current is transferred to the bidirectional thyristor overvoltage protection circuit. 2 to 3 The time period is the process in which the varistor MOV clamps the voltage and absorbs the system energy. 3 At this moment, the leakage current of the varistor MOV will be smaller than the holding current of the bidirectional thyristor S, so the bidirectional thyristor S will turn off itself.

[0037] Figure 6 FIG. 2 shows a voltage waveform diagram of a power terminal of a bidirectional thyristor according to an embodiment of the present invention. Figure 6 As shown, the bidirectional thyristor S is self-turned off and then the voltages of the first power terminal T1 and the second power terminal T2 of the bidirectional thyristor gradually recover to the blocking state voltage 55V. Therefore, the bidirectional thyristor S is successfully self-turned off.

[0038] The present invention uses bidirectional thyristors instead of other switches such as thyristors in series with varistor. Only current in any direction needs to flow between the gate and the power end of the bidirectional thyristor, and the bidirectional thyristor can conduct in both directions. Therefore, compared with the traditional solution, the required switches and switch driving circuits are significantly reduced.

[0039] The present invention can achieve low cost and small size by designing a suitable supporting drive, while ensuring a low clamping voltage and a bus voltage difference, so that the peak voltage of the solid-state circuit breaker is within 1.5 times the bus voltage of the solid-state circuit breaker working system, and can change from zero voltage to peak voltage within 200ns, with a fast opening speed.

[0040] In summary, the bidirectional thyristor overvoltage protection circuit and solid-state circuit breaker provided by the present invention can realize solid-state circuit breaker overvoltage protection with low cost, small size, and low clamping voltage and bus voltage difference.

[0041] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0042] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the following intention: that the claimed invention requires more features than the features explicitly recited in each claim. More specifically, as reflected in the claims below, inventive aspects lie in less than all the features of the individual embodiments disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present invention.

[0043] As used herein, unless otherwise specified, the use of ordinal numbers "first," "second," "third," etc. to describe common objects merely indicates that different instances of similar objects are involved, and is not intended to imply that the objects so described must have a given order in time, space, order, or in any other manner.

[0044] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is primarily selected for readability and instructional purposes, rather than for explaining or limiting the subject matter of the present invention.

[0045] Therefore, without departing from the scope and spirit of the appended claims, many modifications and changes will be apparent to those of ordinary skill in the art. For the scope of the present invention, the disclosure made to the present invention is illustrative rather than restrictive, and the scope of the present invention is limited by the appended claims.

Claims

1. A bidirectional thyristor overvoltage protection circuit, characterized in that: It includes a bidirectional thyristor, a driving circuit of the bidirectional thyristor and a varistor, the driving circuit includes a driving resistor and a driving capacitor, the driving resistor and the driving capacitor are 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 end of the bidirectional thyristor.

2. The bidirectional thyristor overvoltage protection circuit according to claim 1, characterized in that: The resistance of the driving resistor is calculated by the following formula: Among them, R1 is the resistance of the driving resistor, I GTM is the maximum gate trigger current of the bidirectional thyristor, V DC It is the bus voltage of the solid-state circuit breaker working system.

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

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

5. A solid-state circuit breaker, characterized in that: It comprises a bidirectional thyristor overvoltage protection circuit and a solid-state circuit breaker main switch as described in any one of claims 1 to 4, wherein the common end of the varistor connected to the driving resistor is connected to one end of the solid-state circuit breaker main switch; and the second power end 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 at both ends of the main switch of the solid-state circuit breaker causes an instantaneous current to be generated in the drive circuit, the first power end and the second power end of the bidirectional thyristor are bidirectionally conductive, and the varistor is connected in parallel with the main switch of the solid-state circuit breaker through the conductive bidirectional thyristor.

7. The solid-state circuit breaker according to claim 6, characterized in that: The varistor is used to limit and absorb the overvoltage at both ends of 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 is automatically turned off.

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, 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 working system.

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

10. The overvoltage protection experimental circuit of the solid-state circuit breaker according to claim 9, characterized in that: When the fault pulse generator sends out a fault pulse, the fault pulse turns on the fault switch through the fault driver, 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 is turned off.

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