I-type modularized direct-current solid-state circuit breaker

Abstract

The invention discloses an I-type modularized direct-current solid-state circuit breaker, which relates to the technical field of direct-current solid-state circuit breakers and comprises four horizontal bridge arms, namely an FBSM1, an FBSM2, an FBSM3 and an FBSM4, a vertical bridge arm group, and four inductors, namely an L1, an L2, an L3 and an L4. According to the circuit breaker, the removal time of monopole grounding and interelectrode short circuit faults is short and far faster than that of a traditional circuit breaker, and the impact of fault current on equipment can be greatly reduced. Differentiation module control is adopted for different faults, power supply of the other pole is not affected when the faults are removed, and the system reliability is improved. When inter-electrode short circuit occurs, forward voltage is inserted into the full-bridge sub-module to enable the voltage of a short-circuit point to be close to zero, reverse discharge of a capacitor is limited, fault current is cleared at the first zero crossing point of current, fault expansion is avoided, and the problems that an existing traditional solid-state circuit breaker is insufficient in single-pole grounding fault processing capacity, influences system power supply reliability, is single in function and the like are solved.

Description

Technical Field

[0001] This invention relates to the field of DC solid-state circuit breaker technology, and more particularly to a type I modular DC solid-state circuit breaker. Background Technology

[0002] In the process of transforming power systems towards higher efficiency and greater flexibility, medium-voltage direct current (MVDC) systems, with their advantages of high power density, low transmission loss, and strong compatibility, are widely used in key areas such as new energy grid connection, urban rail transit, and integrated ship power systems. However, DC systems do not have a natural zero-crossing point, and the fault current rises rapidly and reaches a high peak value when a short-circuit fault occurs. If fault isolation cannot be achieved within milliseconds or even microseconds, it will lead to serious consequences such as damage to converter valves and bus voltage collapse, threatening the safe and stable operation of the entire system.

[0003] Traditional DC fault protection schemes primarily rely on devices combining mechanical circuit breakers and power electronic components (such as hybrid circuit breakers) to achieve protection functions. However, these schemes have several inherent drawbacks. In terms of breaking speed, the contact breaking speed of mechanical circuit breakers is limited by mechanical inertia, with the fastest breaking time typically between 10-50 ms, making it difficult to match the rapid rise of DC fault current. From a structural and maintenance perspective, they are complex and bulky, and the contacts are prone to wear after repeated breaking operations, resulting in high maintenance costs and limited equipment lifespan. Furthermore, traditional circuit breakers have poor voltage level scalability; to adapt to higher voltage DC systems, the contact structure and insulation scheme must be redesigned, leading to long development cycles and low economic efficiency.

[0004] With the continuous development of power electronics technology, solid-state circuit breakers (SSCBs) have become an ideal solution for medium-voltage DC fault protection due to their outstanding advantages such as no moving mechanical parts, fast breaking speed (down to microseconds), and sensitive response. However, current solid-state circuit breakers still have some technical pain points: First, they lack topological flexibility and scalability, and most products are difficult to standardize and modularize for deployment; second, their fault adaptability is limited, with some designs only able to handle inter-pole short-circuit faults and lacking the ability to handle single-pole ground faults, or requiring the power supply to the entire system to be cut off when a ground fault occurs, failing to guarantee the continuous operation of non-faulty poles, thus reducing the reliability of the system power supply; third, their functions are relatively simple, with traditional solid-state circuit breakers only having fault protection functions and unable to integrate additional functions such as current compensation and energy buffering, making it difficult to meet the needs of medium-voltage DC systems for flexible control and multi-scenario adaptation.

[0005] To address the aforementioned technical challenges, there is an urgent need to develop a modular DC solid-state circuit breaker that is simple in structure, highly scalable, has a fast fault response, and is functionally expandable. This circuit breaker must achieve precise isolation of single-pole grounding faults and inter-pole short-circuit faults, while also possessing the ability to flexibly expand voltage levels and stably control capacitor voltage. Furthermore, it should be able to integrate additional functions through topology optimization, providing an efficient and reliable fault protection solution for medium-voltage DC systems and promoting its further application in fields such as new energy and rail transportation. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a Type I modular DC solid-state circuit breaker, which solves the problems of insufficient handling capability for single-pole grounding faults, impact on system power supply reliability, and limited functionality of existing traditional solid-state circuit breakers.

[0007] The objective of this invention can be achieved through the following technical solution: A type I modular DC solid-state circuit breaker, comprising:

[0008] Four horizontal bridge arms (FBSM1, FBSM2, FBSM3 and FBSM4) and one vertical bridge arm group, and four inductors (L1, L2, L3 and L4);

[0009] Among them, L1, FBSM1 and FBSM2 are connected in series, L2, FBSM4 and FBSM3 are connected in series, and L3, the vertical bridge arm group and L4 are connected in series.

[0010] L3 is connected between FBSM1 and FBSM2, and L4 is connected between FBSM3 and FBSM4.

[0011] As a further embodiment of the present invention, the vertical arm assembly includes four vertical arms HBSM1, HBSM2, HBSM3 and HBSM4.

[0012] As a further embodiment of the present invention, each horizontal bridge arm is composed of multiple full-bridge sub-modules, and each vertical bridge arm is composed of multiple half-bridge sub-modules, wherein the number of full-bridge sub-modules is equal to the number of half-bridge sub-modules.

[0013] As a further embodiment of the present invention, the full-bridge submodule includes switching transistors S1, S2, S3, and S4 and a capacitor C.

[0014] In this configuration, the source (S) of capacitor S1 is connected to the drain (D) of capacitor S3, the source (S) of capacitor S2 is connected to the drain (D) of capacitor S4, the drain (D) of capacitor S1 is connected to the drain (D) of capacitor S2, and the source (S) of capacitor S3 is connected to the source (S) of capacitor S4. One end of capacitor C is connected to the drains of capacitors S1 and S2, and the other end is connected to the source (S) of capacitors S3 and S4.

[0015] As a further aspect of the present invention, when the full-bridge submodule is actively charged, the equivalent capacitor voltage... The equation is expressed as:

[0016]

[0017]

[0018]

[0019]

[0020] in: For amplitude, The phase angle, Angular frequency, For equivalent inductance, This is the equivalent capacitance. The initial voltage, For the initial current, This is the characteristic impedance.

[0021] As a further aspect of the present invention, when the full-bridge submodule is actively charged, the equivalent current... The equation is expressed as:

[0022]

[0023]

[0024]

[0025]

[0026] in: For amplitude, The phase angle, Angular frequency, For equivalent inductance, This is the equivalent capacitance. The initial voltage, For the initial current, This is the characteristic impedance.

[0027] As a further aspect of the present invention, it is characterized in that:

[0028] When an inter-pole short circuit fault occurs, all submodule switching transistors are turned off.

[0029] When a positive DC bus ground short circuit occurs, all the switching transistors of the FBSM1, FBSM2, HBSM1 and HBSM2 submodules are turned off;

[0030] When a negative DC bus ground short circuit occurs, all the switching transistors of the FBSM3, FBSM4, HBSM3 and HBSM4 submodules will be turned off.

[0031] As a further embodiment of the present invention, the time of the first zero crossing of the equivalent circuit of a purely resistive load with a short circuit between electrodes. The formula is expressed as:

[0032]

[0033]

[0034] in, The initial voltage, For the initial current, The frequency of the damped oscillation. This is the power supply voltage. For equivalent inductance, This is the attenuation coefficient.

[0035] As a further embodiment of the present invention, the equivalent circuit of the capacitive load inter-electrode short circuit, the time of the first zero crossing. The formula is expressed as:

[0036]

[0037]

[0038] in, The initial voltage, For the initial current, For equivalent inductance, This is the equivalent capacitance. ω is the angular frequency.

[0039] The beneficial effects of this invention are:

[0040] 1. The circuit breaker of this invention provides a shorter clearing time for single-pole grounding and inter-pole short-circuit faults, significantly faster than traditional circuit breakers, greatly reducing the impact of fault current on equipment. Differentiated module control is used for different faults, ensuring that fault clearing does not affect the power supply to the other pole, thus improving system reliability. In the event of a short circuit, the full-bridge submodule inserts a forward voltage to bring the short-circuit point voltage close to zero, limiting reverse discharge of the capacitor. The fault current is cleared at the first zero-crossing point, preventing the fault from escalating.

[0041] 2. The topology of this invention consists of four horizontal bridge arms and a vertical bridge arm, resulting in a simple structure. Voltage levels can be flexibly expanded by adjusting the number of submodules N without requiring significant topology reconstruction, thus reducing design and modification difficulty. During normal operation, the horizontal bridge arms maintain stable capacitor voltage through active charging, while the vertical bridge arm capacitors continuously charge without additional adjustment, preventing voltage fluctuations from affecting performance.

[0042] 3. The horizontal bridge arm of this invention adopts PWM active charging with adjustable duty cycle. Short-time charging reduces line fluctuations, ensures current stability, and does not interfere with the system power supply. It can effectively handle faults regardless of whether the load is purely resistive or capacitive, and is suitable for various medium-voltage DC scenarios.

[0043] 4. The vertical bridge arm of this invention can release capacitor energy to compensate for line current through the switching half-bridge sub-module. If the capacitor is replaced with a supercapacitor or a battery to increase the capacity, the compensation effect can be further improved, and the functions of power regulation and current stabilization can be expanded, providing more support for medium-voltage DC systems. Attached Figure Description

[0044] Figure 1 This is a topology diagram of a Type I modular DC solid-state circuit breaker according to the present invention;

[0045] Figure 2 The equivalent circuit diagram a of the DC solid-state circuit breaker of the present invention when powered on;

[0046] Figure 3 The equivalent circuit diagram (b) of the DC solid-state circuit breaker of the present invention when powered on;

[0047] Figure 4 This is a switching diagram of the active charging full-bridge sub-module of the DC solid-state circuit breaker of the present invention;

[0048] Figure 5 This is the equivalent circuit for active charging of the DC solid-state circuit breaker of the present invention;

[0049] Figure 6 This is the equivalent circuit diagram of the inter-pole short circuit of the DC solid-state circuit breaker of the present invention;

[0050] Figure 7 This is a simplified equivalent circuit diagram of the DC solid-state circuit breaker for inter-pole short circuits of the present invention.

[0051] Figure 8 This is an equivalent model diagram of the DC solid-state circuit breaker of the present invention for a purely resistive load inter-electrode short circuit.

[0052] Figure 9 This is the equivalent model of the inter-electrode short circuit of the DC solid-state circuit breaker under capacitive load in this invention;

[0053] Figure 10 This is the waveform of the inter-pole short-circuit current of the DC solid-state circuit breaker of the present invention;

[0054] Figure 11 This is the capacitor voltage waveform of the horizontal bridge arm submodule of the DC solid-state circuit breaker of the present invention during inter-pole short circuit.

[0055] Figure 12 This is the inter-pole short-circuit load voltage waveform of the DC solid-state circuit breaker of the present invention;

[0056] Figure 13This is the waveform of the positive terminal grounding short-circuit current of the DC solid-state circuit breaker of the present invention;

[0057] Figure 14 This is the capacitor voltage waveform of the horizontal bridge arm submodule of the DC solid-state circuit breaker of the present invention during a positive-pole grounding short circuit.

[0058] Figure 15 This is the load voltage waveform of the DC solid-state circuit breaker with positive terminal grounding short circuit according to the present invention;

[0059] Figure 16 This is the waveform of the negative terminal grounding short-circuit current of the DC solid-state circuit breaker of the present invention;

[0060] Figure 17 This is the capacitor voltage waveform of the horizontal bridge arm submodule of the DC solid-state circuit breaker of the present invention during a negative-to-ground short circuit.

[0061] Figure 18 This is the load voltage waveform of the DC solid-state circuit breaker of the present invention when the negative terminal is grounded. Detailed Implementation

[0062] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0063] Example 1:

[0064] like Figure 1 As shown, the present invention discloses a type I modular DC solid-state circuit breaker, comprising: four horizontal bridge arms FBSM1, FBSM2, FBSM3 and FBSM4 and a vertical bridge arm group, and four inductors L1, L2, L3 and L4; wherein, the vertical bridge arm group comprises four vertical bridge arms HBSM1, HBSM2, HBSM3 and HBSM4 connected in series.

[0065] Each horizontal bridge arm can be composed of N full-bridge sub-modules, and each vertical bridge arm contains N half-bridge sub-modules, such that the number of full-bridge sub-modules is equal to the number of half-bridge sub-modules.

[0066] Among them, L1, FBSM1 and FBSM2 are connected in series, with the other end of L1 connected to the power supply side and the other end of FBSM2 connected to the load side. L2, FBSM4 and FBSM3 are connected in series, with the other end of L2 connected to the power supply side and the other end of FBSM3 connected to the load side. L3, the vertical bridge arm group and L4 are connected in series, with the other end of L3 connected between FBSM1 and FBSM2 and the other end of L4 connected between FBSM3 and FBSM4.

[0067] like Figure 1As shown, to simplify the model, N is set to 1, and the power supply voltage is... The rated voltage of the capacitors in the four horizontal bridge arm submodules is The rated voltage of the capacitors in the four vertical bridge arm submodules is During normal operation, the voltage of all submodule capacitors needs to be maintained near their rated values. In the event of a short-circuit fault, the fault current can be quickly cut off.

[0068] The circuit breaker's operating process is described below:

[0069] First, the circuit breaker operates in power-on mode. When first connected to the circuit, all submodule capacitors are de-charged and need to be charged before they can operate. During power-on, all bridge arm switches are turned off. The equivalent circuit diagram is as follows: Figure 2 As shown, all the capacitors in the submodules have the same capacitance value. In steady state, the capacitors are equivalent to an open circuit, and the load-side impedance is much smaller than the steady-state impedance of the capacitors. Therefore, it can be approximated as a voltage divider across all the capacitors. Using the voltage divider formula, we can obtain... , This is an approximate voltage that can be achieved when the capacitors of the four horizontal bridge arm submodules are stable. After the horizontal bridge arms are fully charged, the capacitors of the entire bridge submodules are bypassed, resulting in the equivalent circuit. Figure 3 As shown, at this time the entire Charge the capacitors of the four vertical submodules to their rated values. The power-on mode has been completed, and the line is now operating normally.

[0070] When the circuit breaker is operating normally, the horizontal bridge arm submodule needs to be in bypass mode for a long time. Due to the internal resistance of the capacitor and the voltage equalization resistor in the design, the voltage will continue to drop. Therefore, the capacitor needs to be actively charged after a period of time. However, the vertical bridge arm submodule is always in charging mode, so the voltage will not drop.

[0071] Taking FBSM1, which includes one full-bridge submodule, as an example, the full-bridge submodule includes switching transistors S1, S2, S3, and S4, and capacitor C, such as... Figure 4 As shown, the source (S) of capacitor S1 is connected to the drain (D) of capacitor S3, the source (S) of capacitor S2 is connected to the drain (D) of capacitor S4, the drain (D) of capacitor S1 is connected to the drain (D) of capacitor S2, and the source (S) of capacitor S3 is connected to the source (S) of capacitor S4. One end of capacitor C is connected to the drains of capacitors S1 and S2, and the other end is connected to the source (S) of capacitors S3 and S4.

[0072] During active charging, switches S1 and S2 are turned on, and S3 and S4 are turned off. The operation then switches to S1 and S4 being turned on, and S2 and S3 being turned off. The operating condition is as follows: Figure 4 As shown.

[0073] Since the load-side voltage is approximately equal to the supply voltage, the equivalent circuit is as follows: Figure 5As shown, within a short period, capacitor C1 and inductor L1 resonate and exchange energy. When energy is transferred from the inductor to the capacitor, the capacitor voltage rises. During the energy transfer from the capacitor to the inductor, the bypass capacitor is activated, and the circuit remains open. This process repeats, continuously raising the voltage of C1. When a set value is reached, active charging stops. Active charging resumes once the voltage drops below the lower limit. Other horizontal bridge arms operate similarly. A detailed analysis follows:

[0074] set up capacitor voltage Line current According to KVL, the equations can be written.

[0075]

[0076] Initial conditions , The expressions for capacitor voltage and line current can be derived as follows:

[0077]

[0078]

[0079] in,

[0080]

[0081]

[0082] in, Angular frequency, This is the characteristic impedance.

[0083] Visible line current With capacitor voltage It has become an alternating current, affecting the capacitor voltage. Further analysis:

[0084]

[0085]

[0086]

[0087] in: For amplitude, For the phase angle, because , Therefore .so It is The sinusoidal quantity increases with time, so the time for the capacitor to be inserted is the time when switch S4 is turned on, and the time for S2 and S3 to be turned off is less than [time value missing]. The capacitor voltage will then rise. Then, the bypass capacitor (i.e., switching transistors S1 and S2) will turn on, while S3 and S4 will turn off, allowing the current to return to normal. This process is repeated until the current returns to normal. It keeps rising to the upper limit of the threshold.

[0088] The expression for line current can be transformed into:

[0089]

[0090]

[0091]

[0092] in: For amplitude, For the phase angle, therefore It is The value decreases over time and is greater than 0, so the shorter the active charging time, the smaller the line fluctuation.

[0093] Based on this principle, Figure 4 A PWM with a very small duty cycle is applied to the S4 gate. The S2 and S4 signals are inverted, and the left arm S1 and S3 are inverted. S1 is always applied with a high level, which constitutes the simplest PWM active charging.

[0094] When an inter-pole short circuit fault occurs, all module switches are locked out; when a positive DC bus ground short circuit occurs, all switches of sub-modules FBSM1, FBSM2, HBSM1, and HBSM2 are turned off; when a negative DC bus ground short circuit occurs, all switches of sub-modules FBSM3, FBSM4, HBSM3, and HBSM4 are turned off.

[0095] When an inter-electrode short circuit occurs, the equivalent circuit is as follows: Figure 6 As shown. When a positive voltage is inserted into the circuit by the full-bridge submodule, at this time... Approximately equal to The voltage of the vertical bridge arm submodule capacitor is... Therefore, the diode locks it in, which can be considered as an open circuit in the vertical bridge arm. At this time, the voltage at the short circuit point is pulled down to near zero by the full bridge submodule, so the short circuit current is also pulled down.

[0096] To further explain the principle of fault current interruption, the circuit diagram is further equivalent, such as... Figure 7 As shown. The load is a purely resistive load, and the short-circuit resistance is... Equivalent inductance, equivalent capacitance ,in .inductance With capacitor Resonance occurs, and energy exchange takes place. When the capacitor voltage reaches its maximum value, the current in the circuit, i.e. the current in the inductor, is pulled to zero. Due to the limitation of the diode, the capacitor energy cannot be output, and the fault current is cleared at this time.

[0097] Specifically: To simplify the expression, let the module's equivalent capacitance be... Equivalent inductance Capacitor voltage Line current Power supply voltage short-circuit resistance The load is a purely resistive load, and the equivalent circuit is as follows: Figure 8 As shown.

[0098] According to KVL, the equation can be written as follows:

[0099]

[0100] Initial conditions , .

[0101]

[0102] Because R is very small during a short circuit, it is in an underdamped state.

[0103]

[0104]

[0105] , ,

[0106]

[0107] in: The attenuation coefficient is... The resonant angular frequency, The frequency of the damped oscillation. The oscillation frequency is such that the line current has become an oscillation frequency. The amount of communication.

[0108] Return to equivalence Figure 7 The capacitor is limited by an H-bridge consisting of four diodes, allowing current to flow in but not out. Therefore, the above response stops at the first zero-crossing point, where the current is zero, thus breaking the circuit and clearing the fault current. At this time, the capacitor voltage... The maximum value has been reached. According to... Expression, magnitude of communication classification It can be represented as:

[0109]

[0110] when At that time, the amplitude of the AC component This can reach the minimum value, explaining that the total rated voltage of the capacitors in the horizontal submodules equals the power supply. When absorbing fault current, the capacitor voltage rises by the least, reducing the capacitor pressure on the submodule.

[0111] Now let's discuss the time of the first midnight. Influencing factors, improve circuit breaking speed.

[0112]

[0113]

[0114]

[0115] The time of the first midnight can be calculated.

[0116]

[0117]

[0118] Initial voltage of capacitor Increase fault current Decreasing the time for the current to first cross zero Shorten. Take the initial voltage. In theory, this would cut off the fault current in slightly less than a quarter of a cycle.

[0119] If the load is capacitive, the equivalent circuit is as follows to simplify the calculation: Figure 9 As shown:

[0120] Assume the load capacitance Other parameters are the same as those of the equivalent circuit of resistive load.

[0121]

[0122] For capacitor Voltage, initial conditions , Considering It is very small, so the system is in an underdamped state.

[0123]

[0124]

[0125]

[0126] in: Angular frequency, This is the characteristic impedance.

[0127] The time of the first midnight can be calculated.

[0128]

[0129]

[0130] Initial voltage of capacitor Increase fault current Decreasing the time for the current to first cross zero Shorten. Take the initial voltage. In theory, this would cut off the fault current within a quarter of the cycle. Because generally... The first time past midnight It will be shorter.

[0131] The breaking principle of a single-pole ground fault is the same as above.

[0132] Set up the simulation in Simulink with the following parameters:

[0133] power supply 3000V 100uH Capacitors in all sub-modules 70uF Line current I 50A short-circuit resistor 1Ω Load type 400 uF load capacitor Active charging PWM frequency 10kHz PWM duty cycle 0.04

[0134] An inter-electrode short-circuit fault occurred at 2 seconds, triggering protection when the current reached 200A. The current waveform is as follows. Figure 10 As shown. There are 4 horizontal full-bridge submodules, each with a rated voltage of 750V. The upper and lower limits for simulation are set to 700V-800V, and the waveforms are as follows. Figure 11 As shown.

[0135] Based on the above theory, calculate the circuit closure time. The equivalent parameters are as follows:

[0136] , , , ,

[0137]

[0138] Since the capacitance of the actual load will drop, the longest circuit breaking time of a purely resistive load is calculated. .

[0139]

[0140] Therefore, the actual circuit breaker time It should satisfy:

[0141]

[0142] Load voltage waveform as follows Figure 12 As shown, the waveform of a positive ground fault is as follows: Figure 13 As shown, the capacitor voltage waveform of the positive-to-ground short-circuit horizontal bridge arm submodule is as follows: Figure 14 As shown, the load voltage waveform during a positive-to-ground short circuit is as follows: Figure 15 As shown, the waveform of the negative electrode grounding short-circuit current is as follows: Figure 16 As shown, the capacitor voltage waveform of the horizontal bridge arm submodule with negative terminal grounding short circuit is as follows: Figure 17 As shown, the load voltage waveform during a negative-to-ground short circuit is as follows: Figure 18 As shown.

[0143] Simulation results show that this circuit breaker can quickly clear single-pole ground faults and inter-pole short-circuit faults in DC systems, with a fault clearing time of [missing information]. The voltage drop can reach approximately 20µs. In the event of a single-pole ground fault, the circuit breaker can effectively disconnect the fault without affecting the energy transfer to the other pole. Because the capacitance of capacitive loads is limited, the aforementioned calculations assume an ideal situation where the load voltage will not drop. Therefore, the simulation's first zero-crossing point and the calculated value... It's a bit slow, but it's within the calculation range.

[0144] In addition, the vertical bridge arm can compensate for current in the line during operation. By turning the half-bridge sub-module of the vertical bridge arm on and off, the energy of the capacitor in the module can be released to compensate the line. This capacitor may need to be replaced with a supercapacitor or a battery to increase storage capacity.

[0145] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A type I modular DC solid-state circuit breaker, characterized in that, include: Four horizontal bridge arms (FBSM1, FBSM2, FBSM3 and FBSM4) and one vertical bridge arm group, and four inductors (L1, L2, L3 and L4); Among them, L1, FBSM1 and FBSM2 are connected in series, L2, FBSM4 and FBSM3 are connected in series, and L3, the vertical bridge arm group and L4 are connected in series. L3 is connected between FBSM1 and FBSM2, and L4 is connected between FBSM3 and FBSM4.

2. The circuit breaker according to claim 1, characterized in that, The vertical arm assembly includes four vertical arms: HBSM1, HBSM2, HBSM3, and HBSM4.

3. The circuit breaker according to claim 2, characterized in that, Each horizontal bridge arm consists of multiple full-bridge sub-modules, and each vertical bridge arm consists of multiple half-bridge sub-modules, wherein the number of full-bridge sub-modules is equal to the number of half-bridge sub-modules.

4. The circuit breaker according to claim 3, characterized in that, The full-bridge submodule includes switching transistors S1, S2, S3, and S4, and capacitor C; In this configuration, the source (S) of S1 is connected to the drain (D) of S3, the source (S) of S2 is connected to the drain (D) of S4, the drain (D) of S1 is connected to the drain (D) of S2, and the source (S) of S3 is connected to the source (S) of S4. One end of capacitor C is connected to the drains of S1 and S2, and the other end is connected to the source (S) of S3 and S4.

5. The circuit breaker according to claim 4, characterized in that, When the full-bridge submodule is actively charging, the equivalent capacitor voltage The equation is expressed as: in: For amplitude, The phase angle, Angular frequency, For equivalent inductance, This is the equivalent capacitance. The initial voltage, For the initial current, This is the characteristic impedance.

6. The circuit breaker according to claim 4, characterized in that, When the full-bridge submodule is actively charged, the equivalent current is The equation is expressed as: in: For amplitude, The phase angle, Angular frequency, For equivalent inductance, This is the equivalent capacitance. The initial voltage, For the initial current, This is the characteristic impedance.

7. The circuit breaker according to claim 4, characterized in that: When an inter-pole short circuit fault occurs, all submodule switching transistors are turned off. When a positive DC bus ground short circuit occurs, all the switching transistors of the FBSM1, FBSM2, HBSM1 and HBSM2 submodules are turned off; When a negative DC bus ground short circuit occurs, all the switching transistors of the FBSM3, FBSM4, HBSM3 and HBSM4 submodules will be turned off.

8. The circuit breaker according to claim 7, characterized in that, The time of the first zero crossing of the equivalent circuit of a purely resistive load with a short circuit between electrodes. The formula is expressed as: in, The initial voltage, For the initial current, The frequency of the damped oscillation. This is the power supply voltage. For equivalent inductance, This is the attenuation coefficient.

9. The circuit breaker according to claim 7, characterized in that, The equivalent circuit of a capacitive load with a short circuit between electrodes, the time of the first zero crossing. The formula is expressed as: in, The initial voltage, For the initial current, For equivalent inductance, This is the equivalent capacitance. ω is the angular frequency.

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