A hybrid DC switch based on artificial zero crossing

Abstract

This application discloses a hybrid DC switch based on artificial zero-crossing, relating to the field of DC switches. The switch includes a fast-opening circuit breaker and an artificial zero-crossing circuit. The artificial zero-crossing circuit includes an energy storage capacitor, a discharge switch, a charging control switch, and an isolated charging module. Under normal operating conditions, the fast-opening circuit breaker closes, the discharge switch closes, the charging control switch closes, and the isolated charging module charges the energy storage capacitor. Under fault-breaking conditions, the fast-opening circuit breaker opens, the charging control switch closes, the discharge switch closes, and the energy storage capacitor discharges through the discharge switch to generate a reverse current, extinguishing the arc between the contacts of the fast-opening circuit breaker. This application fully utilizes the strong short-time withstand capability of silicon controlled rectifiers (SCRs), featuring small size and low equipment cost, and can achieve rapid interruption of short-circuit current in DC systems.

Description

Technical Field

[0001] This application relates to the field of DC switches, and in particular to a hybrid DC switch based on artificial zero crossing. Background Technology

[0002] With the rapid development of data centers and artificial intelligence technologies, solid-state transformers (SSTs) have begun small-scale deployments, and large-scale application in data centers and other fields is imminent. The widespread use of SSTs has created an urgent demand for matching high-current DC fast-opening circuit breakers. Currently, research on high-current DC switches mainly focuses on pure solid-state fast-opening circuit breakers, traditional mechanical fast-opening circuit breakers, and hybrid DC fast-opening circuit breakers.

[0003] Pure solid-state fast-opening circuit breakers, primarily based on wide-bandgap semiconductors such as silicon carbide (SiC), are currently mainly concentrated in specifications of 100A and below. For high-current applications (especially above 1000A), the conduction losses of pure solid-state fast-opening circuit breakers are too high. For example, even with a conduction loss of less than 1%, an 800V / 2000A solid-state switch still has a full-load loss of around 16kW. Adding the power consumption of a water-cooling system, its operating energy consumption and cost are extremely high. The root cause is that the equivalent on-resistance of silicon carbide devices is still relatively large compared to the metal contact circuit resistance of mechanical contacts (typically in the micro-ohm range). Furthermore, high-capacity DC systems often require DC switches to have a certain short-time withstand capability, which poses a severe challenge to the thermal stability and current-carrying capacity of pure semiconductor devices.

[0004] On the other hand, although traditional molded case air-operated mechanical DC switches have extremely low conduction losses, their mechanical drive time and arc extinguishing time are too long, making it impossible to achieve rapid protection against fault currents and failing to meet the requirements of modern DC systems for millisecond-level rapid interruption.

[0005] Therefore, hybrid DC switches, combining the low losses of mechanical switches with the fast breaking capabilities of power electronic devices, have become the mainstream development direction for high-current DC switches. Existing hybrid DC switches mostly employ a topology of "fast mechanical switch in parallel with insulated-gate bipolar transistor (IGBT) and zinc oxide surge arrester (MOA)". The typical operating process is as follows: after the mechanical fast-opening circuit breaker opens, the IGBT undertakes a brief period of commutation, and then the IGBT is turned off. During the IGBT turn-off period, the zinc oxide surge arrester provides clamp protection for the IGBT and absorbs residual energy in the system. However, when the IGBT is turned on, it needs to withstand the already rising short-circuit current, requiring the IGBT to have a very large current capacity, resulting in high device costs. Simultaneously, to absorb the enormous energy generated by the short-circuit fault, a bulky zinc oxide surge arrester is required. This makes the overall device too large and expensive, and the cost-effectiveness fails to meet the requirements of practical engineering.

[0006] In summary, there is an urgent need for a hybrid DC switch that can both rapidly interrupt short-circuit current in DC systems and effectively reduce the capacity requirements of power electronic devices and the volume of energy-consuming components such as zinc oxide, thereby reducing equipment costs and minimizing space requirements. Summary of the Invention

[0007] The purpose of this application is to provide a hybrid DC switch based on artificial zero crossing, which features small size and low equipment cost and can achieve rapid interruption of short-circuit current in DC systems.

[0008] To achieve the above objectives, this application provides the following solution: This application provides a hybrid DC switch based on artificial zero crossing, including: A fast-opening circuit breaker is connected in series in the main circuit between the DC power supply and the load; A manual zero-crossing circuit is connected in parallel across the two ends of the fast-opening circuit breaker; The artificial zero-crossing circuit includes: an energy storage capacitor, a discharge switch, a charging control switch, and an isolated charging module; the discharge switch is a unidirectional thyristor or a silicon controlled rectifier (SCR). The first end of the energy storage capacitor is connected to the side of the main circuit closest to the DC power supply. The second end of the energy storage capacitor is connected to the first end of the discharge switch and the first end of the charging control switch. The second end of the discharge switch is connected to the side of the main circuit closest to the load. The second end of the charging control switch is connected to the output end of the isolated charging module. The reference end of the isolated charging module is connected to the first end of the energy storage capacitor. The isolated charging module is an isolated charging module with non-common grounds on both sides. The isolated charging module charges the energy storage capacitor using a constant current followed by a constant voltage method. Under normal operating conditions, the fast-opening circuit breaker is closed, the discharge switch is closed, the charging control switch is turned on, and the isolated charging module charges the energy storage capacitor. In the fault-disconnected state, the fast-opening circuit breaker opens, the charging control switch closes, the discharge switch opens, and the energy storage capacitor discharges through the discharge switch to generate a reverse current, extinguishing the arc between the contacts of the fast-opening circuit breaker.

[0009] Optionally, the fast-opening circuit breaker is an air-limiting contact or a vacuum contact; the inherent opening time of the fast-opening circuit breaker is less than or equal to 1 ms.

[0010] Optionally, the first end of the discharge switch is the anode, and the second end is the cathode.

[0011] Optionally, the energy storage capacitor is a non-polarized capacitor; the withstand voltage of the energy storage capacitor is greater than or equal to the rated voltage of the DC power supply.

[0012] Optionally, the charging control switch is an insulated gate bipolar transistor (IGBT); the IGBT is a transistor without a body diode, or a conventional IGBT with a diode connected in series.

[0013] Optionally, the hybrid DC switch based on artificial zero crossing provided in this application further includes a discharge circuit; the discharge circuit includes a discharge resistor and a discharge switch; The discharge resistor and the discharge switch are connected in series and then in parallel across the energy storage capacitor; the discharge switch closes after the fault disconnection state ends to release the residual charge on the energy storage capacitor.

[0014] Optionally, the hybrid DC switch based on artificial zero crossing provided in this application further includes a mechanical disconnect switch; the mechanical disconnect switch is connected in series between the DC power supply and the artificial zero crossing circuit, and is used to provide a physical break after the disconnection is completed.

[0015] Optionally, a current-limiting inductor is connected in series in the main circuit or the artificial zero-crossing circuit; the current-limiting inductor is a parasitic inductor or an independently set physical inductor, used to limit the rate of current rise when the energy storage capacitor discharges.

[0016] Optionally, under the normal operating condition, the isolated charging module charges the energy storage capacitor to a first voltage; the first voltage is higher than the rated voltage of the DC power supply. In the fault-disconnected state, after the energy storage capacitor completes its discharge and the contact arc is extinguished, it is reverse-charged by the DC power supply to the second voltage; the discharge switch is naturally turned off after the energy storage capacitor is fully charged by the reverse voltage; the second voltage is equal to or less than the rated voltage of the DC power supply.

[0017] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a hybrid DC switch based on artificial zero-crossing, which is connected in series with a fast-opening circuit breaker in the main circuit to carry the load current under normal operating conditions. Utilizing the extremely low (micro-ohm) resistance of the mechanical contact metal circuit of the fast-opening circuit breaker, the conduction loss during normal operation is reduced to an extremely low level (e.g., tens of watts), requiring only natural heat dissipation. This effectively overcomes the serious heat generation and high water cooling energy consumption problems caused by the large semiconductor equivalent conduction resistance of pure solid-state fast-opening circuit breakers in high-current (e.g., above 1000A) applications. By setting an artificial zero-crossing circuit connected in parallel across the fast-opening circuit breaker, at the instant the mechanical switch of the fast-opening circuit breaker opens, the discharge switch is controlled to open, causing the energy storage capacitor to release a reverse pulse current. The reverse pulse current and the main circuit current counteract each other between the mechanical switch contacts, achieving "artificial zero-crossing" arc extinguishing within tens to hundreds of microseconds. This achieves "full disconnection immediately upon switch opening," controlling the overall fault disconnection time (including transient processes) to within 2ms, completely solving the shortcomings of traditional mechanical DC switch drives and excessively long arc extinguishing times, which prevent rapid fault clearing. Utilizing the "DC blocking and AC passing" characteristics of the energy storage capacitor and its reverse charging mechanism, the discharge switch automatically turns off after the current naturally decays, eliminating the need for additional energy-consuming components. An isolated charging module ensures that when the discharge switch is open and the charging control switch is closed, other parasitic paths flowing from the power supply to the load are cut off, guaranteeing electrical isolation safety. Furthermore, since the discharge switch naturally turns off when the energy storage capacitor is reverse-charged by the DC power supply and the current approaches zero, it avoids overvoltage problems caused by sudden current changes (di / dt) in the circuit and eliminates the need for complex buffer absorption circuits, further simplifying the system topology and improving operational reliability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a hybrid DC switch structure based on artificial zero crossing in one embodiment of this application; Figure 2 This is a chart showing the analysis of zero crossings manually. Figure 3 This is a full physical model diagram that includes various equivalent resistances and parasitic inductances; Figure 4 This is a topology diagram of the actual product; Figure 5 This is a control timing diagram of a hybrid DC switch based on artificial zero crossing in one embodiment of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] In one exemplary embodiment, such as Figure 1 As shown, a hybrid DC switch based on artificial zero crossing is provided, which includes a fast-opening circuit breaker DLQ and an artificial zero-crossing circuit. The fast-opening circuit breaker DLQ is connected in series in the main circuit between the DC power supply DC_bus and the load D; The manual zero-crossing circuit is connected in parallel across the two ends of the fast-opening circuit breaker DLQ; The artificial zero-crossing circuit includes: an energy storage capacitor cap, a discharge switch Q1, a charging control switch Q2, and an isolated charging module M1; The first terminal C1 of the energy storage capacitor cap is connected to the side of the main circuit closest to the DC power supply DC_bus. The second terminal C2 of the energy storage capacitor cap is connected to the first terminal of the discharge switch Q1 and the first terminal of the charging control switch Q2. The second terminal of the discharge switch Q1 is connected to the side of the main circuit closest to the load D. The second terminal of the charging control switch Q2 is connected to the output terminal of the isolated charging module M1. The reference terminal of the isolated charging module M1 is connected to the first terminal of the energy storage capacitor cap. Under normal operating conditions, the fast-opening circuit breaker DLQ is closed, the discharge switch Q1 is closed, the charging control switch Q2 is open, and the isolated charging module M1 charges the energy storage capacitor cap. In the fault-disconnected state, the fast-opening circuit breaker DLQ opens, the charging control switch Q2 closes, the discharge switch Q1 opens, and the energy storage capacitor cap discharges through the discharge switch Q1 to generate a reverse current, extinguishing the arc between the contacts of the fast-opening circuit breaker DLQ.

[0023] The fast-opening circuit breaker DLQ has an air-limiting contact or a vacuum contact; the inherent opening time of the fast-opening circuit breaker DLQ is less than or equal to 1ms.

[0024] like Figure 1 As shown, contacts A and B are the contact positions of the fast-opening circuit breaker DLQ; contact A is connected to the system power supply DC_bus, and contact B is connected to the load D; The discharge switch Q1 is a unidirectional thyristor or a silicon controlled rectifier; the first terminal of the discharge switch Q1 is the anode, and the second terminal is the cathode. The discharge switch Q1 has a withstand voltage of over 1000V and is responsible for instantaneously releasing a large current in the direction from contact A to the first terminal C1 of the energy storage capacitor cap to the second terminal C2 of the energy storage capacitor cap; Among them, the current-carrying time of the unidirectional thyristor is less than 1ms. By utilizing the short-term overload tolerance capability of the unidirectional thyristor, the cost is reduced and the space is minimized.

[0025] The energy storage capacitor cap is a non-polarized capacitor; the withstand voltage of the energy storage capacitor cap is greater than or equal to the rated voltage of the DC power supply. The capacitor's "DC blocking and AC passing" property allows the current to naturally return to zero.

[0026] Specifically, the energy storage capacitor cap is a thin-film capacitor with a withstand voltage of over 1000V, and its function is energy storage; The charging control switch Q2 is an insulated gate bipolar transistor (IGBT). To ensure a single current direction and bidirectional isolation when off, the IGBT is a transistor without a body diode, or a conventional IGBT with a diode connected in series, with a typical withstand voltage of 1200V.

[0027] The isolated charging module M1 is an isolated charging module with no common ground on both sides; the isolated charging module M1 charges the energy storage capacitor cap in a constant current and then constant voltage manner. The isolated charging module M1 can ensure that there are no other parasitic channels flowing from the power supply to the load when the discharge switch Q1 is open and the charging control switch Q2 is closed.

[0028] As a specific embodiment, the hybrid DC switch based on artificial zero crossing provided in this application further includes a discharge circuit; the discharge circuit includes a discharge resistor and a discharge switch; The discharge resistor R and the discharge switch JDQ are connected in series and then in parallel across the energy storage capacitor cap; the discharge switch closes after the fault disconnection state ends to release the residual charge on the energy storage capacitor cap.

[0029] As a specific embodiment, the hybrid DC switch based on artificial zero crossing provided in this application also includes a mechanical disconnect switch; the mechanical disconnect switch is connected in series between the DC power supply and the artificial zero crossing circuit, and is used to provide a physical break after the disconnection is completed.

[0030] For example, in actual product design, to achieve an absolute break, a mechanical break might be added to the upper end of the manual zero-crossing circuit, such as... Figure 1 An isolating blade or contactor is added between the middle contact A and the first terminal C1 of the energy storage capacitor cap.

[0031] As a specific embodiment, a current-limiting inductor is connected in series in the main circuit or the artificial zero-crossing circuit; the current-limiting inductor is a parasitic inductance L, or an independently set physical inductor, used to limit the rate of current rise when the energy storage capacitor cap discharges.

[0032] For example, in actual product design, if the internal resistance of the capacitor and the parasitic inductance are too small, causing the thyristor to be unable to withstand the di / dt, a separate inductor in the tens of μH range can be designed. Figure 3 and Figure 4 The parasitic inductance L in the figure is a combination of physical inductance and parasitic inductance.

[0033] Under normal operating conditions, the isolated charging module M1 charges the energy storage capacitor cap to a first voltage; the first voltage is higher than the rated voltage of the DC power supply. In the fault-disconnected state, after the energy storage capacitor cap discharges and extinguishes the arc, it is reverse-charged by the DC power supply to the second voltage; the discharge switch Q1 is naturally turned off after the voltage of the energy storage capacitor cap reverses; the second voltage is equal to or less than the rated voltage of the DC power supply.

[0034] like Figure 5As shown in the timing diagram, a load short-circuit fault occurred at time t0, causing the bus voltage to drop and the load current to increase sharply. After detection and confirmation over tens of μs, a tripping command for the fast-opening circuit breaker DLQ was issued at time t1, simultaneously closing the charging control switch Q2. After several hundred μs to 1 ms, the contacts of the fast-opening circuit breaker DLQ opened, forming an arc, which triggered the discharge switch Q1 at time t2. After approximately several tens of μs, the arc extinguished at time t3, forming a break between the main contacts of the fast-opening circuit breaker DLQ, and the triggering command for the discharge switch Q1 was stopped. After several hundred μs, at time t4, the energy storage capacitor cap was reverse-charged, and the thyristor turned off naturally. Thus, the DC short-circuit fault tripping was completed. A detailed analysis follows: Under normal operating conditions, the fast-opening circuit breaker DLQ is closed, the discharge switch Q1 is closed, and the charging control switch Q2 is open. The energy storage capacitor cap is in a floating charge state, with the voltage at the first terminal C1 of the energy storage capacitor cap being low (C1 represents the charging reference ground) and the second terminal C2 of the energy storage capacitor cap being high. Since charging is a gradual process, the charging control switch Q2 can be a low-power surface-mount IGBT without a body diode. If the IGBT has a body diode, a diode needs to be connected in series to ensure that the current flows only from the isolated charging module M1 to the second terminal C2 of the energy storage capacitor cap. Taking DC 800V as an example, the capacitor charging voltage is 900V. The discharge switch Q1 and the charging control switch Q2 can be 1200V type, and the energy storage capacitor cap can also be 1200V rated. Therefore, after fully charging, the voltage at the second terminal C2 of the energy storage capacitor cap, referencing the first terminal C1, is 900V. Obviously, during normal operation, the load current only flows through the contacts of the fast-opening circuit breaker DLQ, and is labeled I1, as shown below. Figure 2 As mentioned above, since the circuit resistance of the contact is in the μΩ range, the power consumption is very low, approximately tens of W, and natural heat dissipation is sufficient.

[0035] When a voltage drop and current I1 increase are detected, the circuit breaker DLQ is immediately given a tripping command, and the charging control switch Q2 is closed to end the floating charge state of the capacitor. When the contacts of the fast-opening circuit breaker DLQ open within milliseconds, the main controller sends a conduction command to the discharge switch Q1. The discharge switch Q1 can open in the 10μs range, releasing a momentarily rising current I2. The current I2 and the current I1 counteract each other between the contacts of the fast-opening circuit breaker DLQ, quickly extinguishing the arc between the contacts. From an electric field perspective, when the discharge switch Q1 is turned on, the cathode of the discharge switch Q1 has a voltage as high as 900V relative to the first terminal C1 of the energy storage capacitor cap (i.e., contact A). Meanwhile, the voltage at contact B is only a few tens of V difference compared to contact A (contact B is lower than contact A). Clearly, the thyristor cathode forcibly pulls the voltage at contact B high, creating a potential difference between the contacts of the fast-opening circuit breaker DLQ (where contact A is lower than contact B), thus disrupting the electric field conditions of the arc and completing arc extinguishing. This current offset is essentially the artificial zero-crossing of the DC current. Obviously, the current I2 rises very quickly, almost like a pulse current, but its essence is still a creeping current limited by the equivalent resistance r (mΩ level) of the capacitor's internal resistance, the copper busbar's internal resistance, the discharge switch Q1 (SCR)'s internal resistance, and the parasitic inductance L (μH level) of the wiring (copper busbar). This current can rise to the tens of thousands of A level within 100μs. Figure 3 The diagram shows the full physical model of various equivalent resistances r and parasitic inductances L.

[0036] After the circuit breaker trips, due to the charge on the energy storage capacitor cap, a discharge resistor R needs to be added to the actual product to prevent electric shock. The fast-opening circuit breaker DLQ closes to complete the discharge, while the normally open fast-opening circuit breaker DLQ remains open. Figure 4 As shown, since this discharge process has already ended after the interruption, it can still slowly discharge in a "slow and steady" mode. Therefore, the discharge voltage R value can be a common high-resistance resistor, which is easy to control in terms of both price and size.

[0037] The isolated charging module M1 and the fast-opening circuit breaker DLQ in this application discharge through the discharge resistor R, both of which are of the "slow and steady" type. Therefore, the IGBT of the charging control switch Q2 and the discharge resistor R can both be of low power type. The IGBT of the charging control switch Q2 can be a small chip package that is soldered onto the circuit board, which is low in cost and does not take up much space.

[0038] The fault current interruption time of this application mainly depends on the inherent opening time of the fast-opening switch, which is generally several hundred μs to 1 ms. The shorter the opening time, the smaller the current rise in the circuit. If the product application does not require short-time withstand capability, the fast-opening circuit breaker DLQ can use air current-limiting contacts; if short-time withstand capability is required, vacuum contacts can be used. This application utilizes an artificial zero-crossing circuit to achieve "immediate full interruption upon opening" of the circuit breaker body. The current-carrying time of the thyristor is extremely short, with arc extinguishing in the range of tens to hundreds of μs. Such a short time can fully utilize the current-carrying capacity of the thyristor. For example, a 1000A thyristor can achieve a short-time current carrying capacity of 20000A. Moreover, the price of thyristors is much lower than that of IGBTs, so the cost of power electronic devices in this solution is very low. In addition, since there is no need for zinc oxide energy consumption, the product occupies a very small space.

[0039] This application is for a composite DC switch, whose main structure consists of a fast-opening circuit breaker DLQ (fast-opening switch) and an artificial zero-crossing circuit. The fast-opening circuit breaker DLQ is required to have an inherent opening time of 1ms or less, and the faster the better. The artificial zero-crossing circuit uses a thyristor to contact a pre-stored capacitor to form a countercurrent opposite to the contact current, and completes arc extinguishing in tens of microseconds, achieving "interruption as soon as the switch opens".

[0040] The fault handling time is mainly in the inherent opening time of the circuit breaker. With 1ms as a typical value, the overall fault breaking time (including transient process) can be controlled within 2ms. For application scenarios that do not require short-term tolerance, air-type current-limiting contacts can be designed and configured to further accelerate the opening speed.

[0041] In this application, all power electronic devices are turned off when the current is infinitely close to zero, so there will be no overvoltage due to di / dt, which further reduces materials and lowers costs.

[0042] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0043] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A hybrid DC switch based on artificial zero crossing, characterized in that, include: A fast-opening circuit breaker is connected in series in the main circuit between the DC power supply and the load; A manual zero-crossing circuit is connected in parallel across the two ends of the fast-opening circuit breaker; The artificial zero-crossing circuit includes: an energy storage capacitor, a discharge switch, a charging control switch, and an isolated charging module; the discharge switch is a unidirectional thyristor or a silicon controlled rectifier (SCR). The first end of the energy storage capacitor is connected to the side of the main circuit closest to the DC power supply. The second end of the energy storage capacitor is connected to the first end of the discharge switch and the first end of the charging control switch. The second end of the discharge switch is connected to the side of the main circuit closest to the load. The second end of the charging control switch is connected to the output end of the isolated charging module. The reference end of the isolated charging module is connected to the first end of the energy storage capacitor. The isolated charging module is an isolated charging module with non-common grounds on both sides. The isolated charging module charges the energy storage capacitor using a constant current followed by a constant voltage method. Under normal operating conditions, the fast-opening circuit breaker is closed, the discharge switch is closed, the charging control switch is turned on, and the isolated charging module charges the energy storage capacitor. In the fault-disconnected state, the fast-opening circuit breaker opens, the charging control switch closes, the discharge switch opens, and the energy storage capacitor discharges through the discharge switch to generate a reverse current, extinguishing the arc between the contacts of the fast-opening circuit breaker.

2. The hybrid DC switch based on artificial zero-crossing according to claim 1, characterized in that, The fast-opening circuit breaker has an air-limiting contact or a vacuum contact; the inherent opening time of the fast-opening circuit breaker is less than or equal to 1 ms.

3. The hybrid DC switch based on artificial zero-crossing according to claim 1, characterized in that, The first end of the discharge switch is the anode, and the second end is the cathode.

4. The hybrid DC switch based on artificial zero-crossing according to claim 1, characterized in that, The energy storage capacitor is a non-polarized capacitor; the withstand voltage of the energy storage capacitor is greater than the rated voltage of the DC power supply.

5. The hybrid DC switch based on artificial zero-crossing according to claim 1, characterized in that, The charging control switch is an insulated gate bipolar transistor (IGBT); the IGBT is a transistor without a body diode, or a conventional IGBT with a diode connected in series.

6. The hybrid DC switch based on artificial zero-crossing according to claim 1, characterized in that, It also includes a discharge circuit; the discharge circuit includes a discharge resistor and a discharge switch; The discharge resistor and the discharge switch are connected in series and then in parallel across the energy storage capacitor; the discharge switch closes after the fault disconnection state ends to release the residual charge on the energy storage capacitor.

7. The hybrid DC switch based on artificial zero-crossing according to claim 1, characterized in that, It also includes a mechanical disconnect switch; the mechanical disconnect switch is connected in series between the DC power supply and the artificial zero-crossing circuit, and is used to provide a physical break after the disconnection is completed.

8. The hybrid DC switch based on artificial zero-crossing according to claim 1, characterized in that, A current-limiting inductor is connected in series in the main circuit or the artificial zero-crossing circuit; the current-limiting inductor is a parasitic inductor or an independently set physical inductor, used to limit the rate of current rise when the energy storage capacitor discharges.

9. The hybrid DC switch based on artificial zero-crossing according to claim 1, characterized in that, Under normal operating conditions, the isolated charging module charges the energy storage capacitor to a first voltage; the first voltage is higher than the rated voltage of the DC power supply. In the fault disconnection state, after the energy storage capacitor completes arc extinguishing by discharging, it is reverse-charged to the second voltage by the DC power supply; the discharge switch naturally turns off after the energy storage capacitor is fully charged by the reverse voltage. The second voltage is equal to or less than the rated voltage of the DC power supply.

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