Single-drive multi-switch series-connection high-voltage solid-state circuit breaker circuit

Abstract

The invention discloses a single-drive multi-switch series-connection high-voltage solid-state circuit breaker circuit, which comprises at least two series-connection SiC MOSFET devices, a gate drive circuit controls a plurality of series-connection SiC MOSFET devices, each SiC MOSFET device is connected in parallel with a buffer circuit, the buffer circuit comprises a resistor and a capacitor which are connected in series, the other end of the resistor is connected with the drain electrode of the SiC MOSFET device, and the other end of the resistor is connected with the drain electrode of the SiC MOSFET device. The other end of the capacitor is connected with the source; each SiC MOSFET device corresponds to one piezoresistor, one end of each piezoresistor is connected with a source electrode of the corresponding SiC MOSFET device, the other end of each piezoresistor is connected with a grid electrode of the next SiC MOSFET device, and the piezoresistor of the last SiC MOSFET device is connected to a drain electrode and a source electrode of the last SiC MOSFET device in parallel. By adopting the improved grid control method, the grid oscillation phenomenon is successfully inhibited, and the stability of the circuit is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-voltage solid-state circuit breakers (SSCBs). The present invention relates to a high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series. The circuit is suitable for use in high-voltage DC power systems to achieve efficient fault clearing and stable voltage control. Background Art

[0002] With the continuous development of DC grids, the demand for safe disconnection of high-voltage circuits is increasing. Traditional mechanical circuit breakers have slow response speeds and are subject to mechanical wear, making them unable to meet the requirements of modern high-voltage DC grids. In contrast, solid-state circuit breakers, with their fast response, arc-free operation, and high reliability, are an ideal solution.

[0003] In existing technologies, many solid-state circuit breakers use multiple gate drive circuits to control series-connected power devices. While this multi-gate control approach offers certain advantages, it suffers from circuit complexity, high costs, and slow response times. Therefore, a new drive method is urgently needed to simplify the circuit structure and improve its performance. Summary of the Invention

[0004] The object of the present invention is to provide a high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series, which adopts an improved gate control method to successfully suppress gate oscillation and improve circuit stability.

[0005] The technical solutions for achieving the purpose of the present invention are: A single-drive, multi-switch series high-voltage solid-state circuit breaker circuit includes at least two SiC MOSFET devices connected in series. The multiple SiC MOSFET devices are controlled by a gate drive circuit. Each SiC MOSFET device is connected in parallel to a buffer circuit. The buffer circuit includes a resistor and a capacitor connected in series, with the other end of the resistor connected to the drain of the SiC MOSFET device and the other end of the capacitor connected to the source. Each SiC MOSFET device corresponds to a varistor. One end of the varistor is connected to the source of the SiC MOSFET device, and the other end is connected to the gate of the next SiC MOSFET device. The varistor of the last SiC MOSFET device is connected in parallel to the drain and source of the last SiC MOSFET device.

[0006] In a preferred technical solution, the gate of the first SiC MOSFET device is connected to the gate drive circuit via a first gate resistor, and the gates of the remaining SiC MOSFET devices are connected to the source of the first SiC MOSFET device via gate resistors and drive capacitors, respectively.

[0007] In a preferred technical solution, the other end of the varistor of the remaining SiC MOSFET devices except the last SiC MOSFET device is connected to the gate of the next SiC MOSFET device through a first diode, the anode of the first diode is connected to the gate of another SiC MOSFET device, and the cathode is connected to the varistor.

[0008] In a preferred technical solution, a gate capacitor is connected between the cathode of the first diode and the source of the subsequent SiC MOSFET device.

[0009] In a preferred technical solution, a second diode is connected between the cathode of the first diode and the source of the subsequent SiC MOSFET device, the cathode of the second diode is connected to the cathode of the first diode, and the anode of the second diode is connected to the source of the subsequent SiC MOSFET device.

[0010] In a preferred technical solution, the gate capacitor is used to mitigate gate voltage changes and help control the switching dynamics of the MOSFET.

[0011] The present invention also discloses a high-voltage direct current power system, comprising a high-voltage solid-state circuit breaker circuit. The high-voltage solid-state circuit breaker circuit is the above-mentioned single-drive multi-switches connected in series high-voltage solid-state circuit breaker circuit.

[0012] Compared with the prior art, the present invention has the following significant advantages: A single gate drive circuit controls multiple power devices in series, simplifying the circuit structure. The capacitive coupling drive method effectively reduces the number of external components and improves circuit compactness.

[0013] An improved gate control method was used to successfully suppress gate oscillation and improve circuit stability. A snubber circuit, consisting of a resistor and a capacitor connected in parallel with each device, provides static and dynamic voltage balance. This reduces current flow to minimize device stress during the off state, altering switching speed and improving the MOV's steep leading edge effect.

[0014] The fault clearing performance of the circuit breaker is improved, and the voltage withstand capability is increased to meet the requirements of the high-voltage DC power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a topological diagram of a high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series according to this embodiment; Figure 2 is a schematic diagram of the current path during the conduction transition period; Figure 3 is a schematic diagram of the current path during the turn-off transition; Figure 4a It is Vds and I line The simulation waveform of Figure 4b It is V ds The simulation waveform of Figure 4c It is V gs The simulation waveform. DETAILED DESCRIPTION

[0016] The principle of this invention is to employ an improved gate control method to successfully suppress gate oscillation and improve circuit stability. A snubber circuit, consisting of a resistor and a capacitor connected in parallel with each device, provides static and dynamic voltage balance. This reduces current flow to minimize device stress during the off state, alters switching speed, and improves the MOV's steep leading edge effect. This improves the circuit breaker's fault-clearing performance and withstands increased voltage, meeting the requirements of high-voltage DC power grids.

[0017] Example 1:

[0018] like Figure 1 As shown, a single-drive multi-switch series high-voltage solid-state circuit breaker circuit includes at least two SiC MOSFET devices connected in series. The multiple SiC MOSFET devices are controlled by a gate drive circuit. Each SiC MOSFET device is connected in parallel with a snubber circuit. The snubber circuit includes resistors (Rs1-Rs3) and capacitors (Cs1-Cs3) connected in series. The other end of the resistor is connected to the drain of the SiC MOSFET device, and the other end of the capacitor is connected to the source. Each SiC MOSFET device corresponds to a varistor (MOV1-MOV3). One end of the varistor (MOV1-MOV3) is connected to the source of the SiC MOSFET device, and the other end is connected to the gate of the next SiC MOSFET device. The varistor of the last SiC MOSFET device is connected in parallel to the drain and source of the last SiC MOSFET device.

[0019] The snubber circuit consists of a resistor and a capacitor in parallel with each device for static and dynamic voltage balance, which will reduce the current to reduce the stress of the device during the off state, change the switching speed and improve the MOV steep leading edge effect.

[0020] In a preferred implementation, the gate of the first SiC MOSFET device Q1 is connected to the gate drive circuit via a first gate resistor R1, and the gates of the remaining SiC MOSFET devices are connected to the source of the first SiC MOSFET device Q1 via gate resistors (R2, R3) and drive capacitors (C1, C2), respectively.

[0021] In a preferred implementation, the other end of the varistor (MOV1\MOV2) of the remaining SiC MOSFET devices except the last SiC MOSFET device Q3 is connected to the gate of the next SiC MOSFET device through the first diode (Dgs1 and Dgs2), the anode of the first diode (Dgs1 and Dgs2) is connected to the gate of another SiC MOSFET device, and the cathode is connected to the varistor (MOV1\MOV2).

[0022] In a preferred implementation, gate capacitors ( Cg1 and Cg2 ) are connected between the cathode of the first diode ( Dgs1 and Dgs2 ) and the source of the subsequent SiC MOSFET device.

[0023] In a preferred implementation, a second diode (Dg1 and Dg2) is connected between the cathode of the first diode (Dgs1 and Dgs2) and the source of the subsequent SiC MOSFET device, the cathode of the second diode (Dg1 and Dg2) is connected to the cathode of the first diode (Dgs1 and Dgs2), and the anode of the second diode (Dg1 and Dg2) is connected to the source of the subsequent SiC MOSFET device.

[0024] In a preferred implementation, gate capacitors (Cg1 and Cg2) are used to smooth gate voltage variations and help control the switching dynamics of the MOSFET.

[0025] In another embodiment, a high-voltage direct current power system includes a high-voltage solid-state circuit breaker circuit, which is the above-mentioned high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series.

[0026] Taking three SiC MOSFET devices (Q1, Q2, Q3) connected in series as an example, the present invention's single-drive multi-switch series high-voltage solid-state circuit breaker circuit is described in detail. The present invention adopts a capacitive coupling drive method, where a single gate drive circuit controls multiple SiC MOSFETs connected in series. Figure 1 shown. Figure 1 This paper describes the configuration of a proposed topology of three SiC MOSFETs in series. This topology is designed based on a coupled capacitor approach. Only a single gate driver is required to drive the multiple cascaded SiC MOSFETs. The switching of the top device is nearly synchronized with that of the bottom device. The driver capacitors C1 and C2 regulate the gate voltage of the power devices through charge transfer, thereby controlling the switching states of the devices. Another notable feature is that the topology requires only a small number of components, which reduces costs and improves circuit compactness.

[0027] Gate oscillation suppression: Specifically, resistors R1, R2, and R3 serve as gate resistors, while diodes Dg1 and Dg2 ensure a small negative voltage across Vgs to shut down Q2 and Q3. Furthermore, Dgs1 and Dgs2 are added between the gates of Q2 and Q3 and the cathodes of Dg1 and Dg2 to suppress charge sharing between parasitic components, thereby improving circuit stability. Gate capacitors Cg1 and Cg2 are specifically designed to suppress gate oscillations and improve overall circuit stability. They primarily serve to moderate gate voltage variations and help control the switching dynamics of the MOSFET. A snubber circuit, consisting of a resistor and a capacitor connected in parallel with each device, provides static and dynamic voltage balancing. This reduces current flow to minimize device stress during the off state, improves switching speed, and improves the MOV's steep leading edge effect.

[0028] like Figure 2 The figure illustrates the current path during the turn-on transition. For convenience, only two series-connected power devices are included, as Q3's switching process is similar to Q2. When the bottom device's turn-on signal is sent to Q1's gate, Q1's Cgs1 is charged, causing Vgs1 to increase. When Vgs1 exceeds the threshold voltage Vgs(th), Q1 fully turns on. Then, Q1's Vds begins to rapidly decrease. Simultaneously, capacitor C1 begins to discharge rapidly, and the charge moves along the path to Q2's gate. Notably, this charge does not flow into MOV1, as its impedance approaches infinite at this point. Subsequently, Q2's Cgs2 is charged, allowing Q2 to similarly turn on. The turn-on delay of both devices is very minimal, ensuring fault-clearing performance. In particular, the values ​​of C1 and C2 should be evaluated from different perspectives, as large capacitance accelerates the turn-on transition and increases the turn-on voltage level, but also hinders the turn-off transition, increasing switching losses.

[0029] The current path during the turn-off transition is as follows Figure 3 When a zero voltage signal is sent to the gate of Q1, Vgs1 decreases and Q1 turns off. At the same time, the current line charges the gate-drain and drain-source capacitance C1 of Q1.

[0030] The voltage across C1 and Q1 increases accordingly, and the current through Q1 flows to the snubber circuit and then the MOV circuit, which plays a vital role in managing transients and protecting the circuit from overvoltage.

[0031] As the charging current of C1 discharges Cgs2, Vgs2 decreases accordingly, and Q2 turns off. Finally, the Vds of both devices return to their steady-state value, half the bus voltage, which represents the equilibrium state of the system under no-load conditions.

[0032] Simulation and experimental verification: To verify the proposed topology, a 750μH inductive load at 1.35kV bus voltage was simulated on PSPICE.

[0033] The simulation waveform is as follows Figure 4a-4c As shown in Figure 1, the simulation waveforms of Vds, Iline and Vgs are shown. The main focus of the simulation results is the turn-off process.

[0034] The circuit breaker successfully cleared the fault current. Although the negative voltage spike on Vgs2 and Vgs3 approached -18V, it was transient and helped to effectively shut down the SiC MOSFET. During the voltage recovery process, the gate voltage was well suppressed without any oscillation, and the bus current exhibited no resonance and a sinusoidal waveform. The three drain-source voltages of the MOSFETs showed good consistency. Due to the coupling capacitors C1 and C2, the on-state voltages of Q2 and Q3 reached almost the same voltage level as Vgs1 (12V) without any losses. Therefore, the structural improvement was successful, and the designed SSCB performed well.

[0035] Through simulation and experimental verification, the present invention uses a single-gate drive method to control multiple series-connected power devices, offering advantages such as simplified circuitry, reduced costs, improved stability, and increased system scalability. It can also achieve rapid fault clearing in high-voltage DC power grids and exhibit high reliability.

[0036] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series, comprising at least two SiC MOSFET devices connected in series, wherein the multiple SiC MOSFET devices connected in series are controlled by a gate drive circuit, characterized in that: A buffer circuit is connected in parallel to each SiC MOSFET device, wherein the buffer circuit includes a resistor and a capacitor connected in series, the other end of the resistor is connected to the drain of the SiC MOSFET device, and the other end of the capacitor is connected to the source; Each SiC MOSFET device corresponds to a varistor. One end of the varistor is connected to the source of the SiC MOSFET device, and the other end is connected to the gate of the next SiC MOSFET device. The varistor of the last SiC MOSFET device is connected in parallel to the drain and source of the last SiC MOSFET device.

2. The high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series according to claim 1, characterized in that: The gate of the first SiC MOSFET device is connected to the gate driving circuit through a first gate resistor, and the gates of the remaining SiC MOSFET devices are connected to the source of the first SiC MOSFET device through gate resistors and driving capacitors respectively.

3. The high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series according to claim 1, characterized in that: The other end of the varistor of the remaining SiC MOSFET devices except the last SiC MOSFET device is connected to the gate of the next SiC MOSFET device through the first diode, the anode of the first diode is connected to the gate of another SiC MOSFET device, and the cathode is connected to the varistor.

4. The high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series according to claim 3, characterized in that: A gate capacitor is connected between the cathode of the first diode and the source of the subsequent SiC MOSFET device.

5. The high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series according to claim 3, characterized in that: A second diode is connected between the cathode of the first diode and the source of the subsequent SiC MOSFET device, the cathode of the second diode is connected to the cathode of the first diode, and the anode of the second diode is connected to the source of the subsequent SiC MOSFET device.

6. The high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series according to claim 4, characterized in that: The gate capacitance is used to smooth gate voltage variations and help control the switching dynamics of the MOSFET.

7. A high voltage direct current power system comprising a high voltage solid state circuit breaker circuit, characterized in that: The high-voltage solid-state circuit breaker circuit is a high-voltage solid-state circuit breaker circuit with a single drive and multiple switches connected in series as described in any one of claims 1 to 6.

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