Thyristor auxiliary commutation type solid-state circuit breaker for energy storage power station

Abstract

The thyristor auxiliary commutation type solid-state circuit breaker is composed of a current limiting assembly, a commutation branch, a through-flow branch and an energy consumption branch, the commutation branch is connected to the two ends of the current limiting assembly and the through-flow branch in parallel, the commutation branch comprises a forward commutation branch and a reverse commutation branch which are connected in parallel, and the forward commutation branch and the reverse commutation branch are connected in parallel. The forward commutation branch comprises a thyristor T1, a first thyristor passive trigger branch connected with the thyristor T1 in parallel and a pre-charging capacitor C2 connected with the thyristor T1 in series, the first thyristor passive trigger branch comprises a resistor R1, a diode D1, a breakdown diode BOD1, a resistor R2 and a capacitor C1, the resistor R1, the diode D1 and the breakdown diode BOD1 are connected in series, the resistor R2 and the capacitor C1 are connected in parallel, one end of a diode D2 and one end of a diode D3 are connected with the thyristor T1, and the other end of the diode D2 and the other end of a diode D3 are connected with the pre-charging capacitor C2. And the other end is connected between the breakdown diode BOD1 and the resistor R2 and the capacitor C1 which are connected in parallel. The energy consumption branch is connected to the two ends of the through-flow branch in parallel so as to absorb energy released in the fault period.

Description

Technical Field

[0001] This invention relates to the field of oil-immersed transformer testing technology, and in particular to a thyristor-assisted converter type solid-state circuit breaker and method for use in energy storage power stations. Background Technology

[0002] Currently, air circuit breakers used in energy storage power stations suffer from drawbacks such as long breaking times and poor reliability, and are accompanied by severe smoke and noise. In recent years, with the rapid development of power semiconductor devices, solid-state circuit breakers based on power electronic devices have been increasingly analyzed. Compared to traditional air circuit breakers, solid-state circuit breakers based on power electronic devices can achieve faster breaking, effectively shortening fault duration. Furthermore, they have a long electrical life and are clean and pollution-free, making them an ideal solution for the rapid and reliable protection of future energy storage power stations. Solid-state circuit breakers based on power electronic devices can quickly disconnect the connection between the energy storage battery and the grid in the event of grid anomalies, preventing accidents caused by battery overcharging, over-discharging, or other faults. Through precise control of the circuit breaker's operation, the operational stability and safety of the energy storage power station are ensured.

[0003] As a crucial component of DC distribution network protection equipment, the DC circuit breaker's response speed and capability to faults are of paramount importance. Since DC circuit breakers are mostly installed at line inlets and outlets, and numerous power electronic devices are also installed on the DC bus side, excessively high line currents and reduced DC bus voltage caused by DC faults directly affect the safe and stable operation of the DC bus and power equipment, and may even cause widespread power outages, disrupting users' daily lives. To mitigate the harm caused by such faults, stable and reliable DC circuit breaker devices need to be installed on the line side and at critical equipment terminals.

[0004] With the rapid advancement of semiconductor materials and manufacturing processes, all-solid-state DC circuit breakers (SSCBs) made from semiconductor switching devices have emerged. Common examples include electrostatic induction crystal metal-oxide-semiconductor (SIT), field-effect transistors (MOSFETs), junction field-effect transistors (JFETs), and insulated-gate bipolar transistors (IGBTs). These power semiconductor switching devices have received widespread attention in recent years due to their excellent characteristics such as fast switching speed, no mechanical contacts, arc-free breaking, high operating frequency, and long service life. The main structure of an SSCB consists of power solid-state switching devices and buffers, energy-absorbing elements, etc.

[0005] Existing power electronic devices have low surge current tolerance and limited breaking capacity. They typically require auxiliary commutation measures to improve breaking capacity, but these measures are complex and require additional control loops. Current DC solid-state circuit breakers do not include current-limiting modules. If a short-circuit fault occurs and the current rise rate is extremely high, the requirements for power device selection and breaking capacity are very stringent. This not only increases costs but also reduces equipment reliability, severely impacting the practicality of DC power distribution systems and increasing maintenance costs. Furthermore, conventional active auxiliary commutation schemes require external active control, which is complex and has low reliability.

[0006] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] To address the shortcomings or defects of the existing technology, a thyristor-assisted converter-type solid-state circuit breaker and method for energy storage power stations are provided. Due to its passive triggering structure, it is simple and reliable, and can significantly improve the turn-off capability of power electronic devices.

[0008] The objective of this invention is achieved through the following technical solutions.

[0009] A thyristor-assisted converter-type solid-state circuit breaker for an energy storage power station comprises a current-limiting component, a converter branch, a current-carrying branch, and an energy-dissipating branch. The current-carrying branch includes at least one set of main power electronic switches S1 and S2 connected in series to conduct load current under normal operating conditions. The current-limiting component includes a current-limiting inductor L connected in series with the current-carrying branch. The converter branch is connected in parallel across the current-limiting component and the current-carrying branch. The converter branch includes a forward converter branch and a reverse converter branch connected in parallel. The forward converter branch includes a thyristor T1, a first thyristor passive triggering branch connected in parallel with the thyristor T1, and a pre-charge capacitor C2 connected in series with the thyristor T1. The first thyristor passive triggering branch includes a resistor R1, a diode D1, a breakdown diode BOD1 connected in series, and a resistor R in parallel. 2. A series diode D2 and a capacitor C1 are connected at one end to thyristor T1, and at the other end to the breakdown diode BOD1 and the parallel resistor R2 and capacitor C1. The reverse commutation branch includes thyristor T2, a second thyristor passive triggering branch connected in parallel with thyristor T2, and a pre-charge capacitor C4 connected in series with thyristor T2. The second thyristor passive triggering branch includes a series resistor R3, a diode D4, a breakdown diode BOD2, and a parallel resistor R4 and capacitor C3. A series diode D5 and a diode D6 are connected at one end to thyristor T2, and at the other end to the breakdown diode BOD2 and the parallel resistor R4 and capacitor C3. The energy dissipation branch is connected in parallel across the current-carrying branch to absorb the energy released during a fault.

[0010] In the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, when a short-circuit fault occurs in the current-carrying branch, a positive voltage UL is induced on the current-limiting inductor L. The positive voltage UL is superimposed with the initial voltage UC on the pre-charge capacitor C2 and applied to the first thyristor passive triggering branch, causing the breakdown diode BOD1 to break down and conduct. Then, a trigger current is injected into the gate of the thyristor T1 through diodes D2 and D3, causing the thyristor T1 to conduct. The pre-charge capacitor C2 forms an LC oscillation circuit through the thyristor T1, the current-limiting inductor L, the main power electronic switch S1, and the main power electronic switch S2, forcing the current in the main power electronic switch S1 and the main power electronic switch S2 to decrease and be turned off at the zero crossing, realizing the transfer of current to the energy-consuming branch for energy discharge.

[0011] In the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the breakdown diode BOD1 or the breakdown diode BOD2 is an avalanche diode or a Zener diode, and its breakdown voltage is set to conduct only when the inductor induced voltage caused by a short circuit fault reaches a preset threshold, so as to avoid false triggering under normal fluctuations.

[0012] In the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the pre-charge capacitor C2 or pre-charge capacitor C4 is pre-charged to 50% to 100% of the rated voltage of the DC side of the system, and the charging polarity makes the discharge current direction opposite to the direction of the current in the current-carrying branch.

[0013] In the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the main power electronic switch S1 or the main power electronic switch S2 is composed of multiple IGBT, MOSFET or IGCT devices connected in series and parallel.

[0014] In the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the connection structure of the forward converter branch and the connection structure of the reverse converter branch are symmetrical.

[0015] In the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the current-limiting inductor L simultaneously undertakes the dual functions of limiting the rate of rise of fault current and providing the induced voltage required for triggering thyristor T1.

[0016] In the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the main power electronic switch S1 or the main power electronic switch S2 is a fully controlled semiconductor device that immediately receives a shutdown command and performs a shutdown action when it detects that the current has dropped to a set value or crossed zero.

[0017] In the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the energy-consuming branch includes a metal oxide varistor (MOV).

[0018] The operating method of a thyristor-assisted converter type solid-state circuit breaker used in energy storage power stations includes: During normal operation, the main power electronic switch S1 and the main power electronic switch S2 are in the conducting state, and the load current flows through the current-limiting inductor L and the current-carrying branch. When a short-circuit fault occurs in the current-carrying branch, the fault current rises rapidly, generating an induced voltage UL on the current-limiting inductor L. The induced voltage UL and the voltage UC on the pre-charge capacitor C2 are superimposed and act on the forward commutation branch; The breakdown diode BOD1 conducts due to overvoltage, and the trigger current flows through diodes D2 and D3 into the gate of thyristor T1, causing it to conduct. The pre-charge capacitor C2 forms an LC oscillation circuit through the thyristor T1, the current-limiting inductor L, the main power electronic switch S1 and the main power electronic switch S2. Reverse current is injected into the current-passing branch, which reduces the current in the main power electronic switch S1 and the main power electronic switch S2. When the current of the main power electronic switch S1 and the main power electronic switch S2 is detected to cross zero or drop to a safe level, a shutdown signal is issued to shut down the main power electronic switch S1 and the main power electronic switch S2. The fault current is transferred to the energy-consuming branch, where the MOV absorbs the remaining energy, thus completing the fault isolation.

[0019] Compared with the prior art, the beneficial effects of this invention are as follows: This invention detects short-circuit faults while simultaneously triggering capacitor discharge and commutation shutdown, improving both reliability and breaking capacity. The addition of a current-limiting inductor component limits the short-circuit current and simultaneously triggers the thyristor commutation branch, offering simplicity and reliability. The current-limiting inductor reduces the fault current rise rate, better protecting power electronic devices. The capacitor pre-charge voltage is flexible and controllable, adjustable according to the fault characteristics of different systems.

[0020] The description provided is merely an overview of the technical solution of this invention. In order to make the technical means of this invention clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and to make the described and other objects, features and advantages of this invention more obvious and understandable, specific embodiments of this invention are described below. Attached Figure Description

[0021] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0022] In the attached diagram: Figure 1 This is a schematic diagram of the topology of an auxiliary converter-type solid-state circuit breaker used in energy storage power stations. Figures 2(a) to 2(b) This is a schematic diagram of the normal current-carrying process of the circuit breaker of the present invention; Figures 3(a) to 3(c) This is a schematic diagram of the short-circuit current turn-off process of the circuit breaker of the present invention; Figures 4(a) to 4(b) This is a schematic diagram of the self-charging process of the circuit breaker capacitor according to the present invention.

[0023] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0024] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0025] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0026] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0027] To better understand, such as Figures 1 to 4(b) As shown, a thyristor-assisted converter-type solid-state circuit breaker for an energy storage power station comprises a current-limiting component, a converter branch, a current-carrying branch, and an energy-dissipating branch. The current-carrying branch includes at least one set of main power electronic switches S1 and S2 connected in series to conduct load current under normal operating conditions. The current-limiting component includes a current-limiting inductor L connected in series with the current-carrying branch. The converter branch is connected in parallel across the current-limiting component and the current-carrying branch. The converter branch includes a forward converter branch and a reverse converter branch connected in parallel. The forward converter branch includes a thyristor T1, a first thyristor passive triggering branch connected in parallel with the thyristor T1, and a pre-charging capacitor C2 connected in series with the thyristor T1. The first thyristor passive triggering branch includes a resistor R1, a diode D1, a breakdown diode BOD1 connected in series, and a parallel-connected capacitor C2. Resistor R2 and capacitor C1, diodes D2 and D3 connected in reverse series are connected at one end to thyristor T1, and at the other end between the breakdown diode BOD1 and the parallel resistor R2 and capacitor C1. The reverse commutation branch includes thyristor T2, a second thyristor passive triggering branch connected in parallel with thyristor T2, and a pre-charge capacitor C4 connected in series with thyristor T2. The second thyristor passive triggering branch includes a series resistor R3, diode D4, breakdown diode BOD2, and a parallel resistor R4 and capacitor C3. Diodes D5 and D6 connected in reverse series are connected at one end to thyristor T2, and at the other end between the breakdown diode BOD2 and the parallel resistor R4 and capacitor C3. The energy dissipation branch is connected in parallel across the current-carrying branch to absorb the energy released during a fault.

[0028] In a preferred embodiment of the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, when a short-circuit fault occurs in the current-carrying branch, a positive voltage UL is induced on the current-limiting inductor L. The positive voltage UL is superimposed with the initial voltage UC on the pre-charge capacitor C2 and applied to the first thyristor passive triggering branch, causing the breakdown diode BOD1 to break down and conduct. Then, a trigger current is injected into the gate of the thyristor T1 through diodes D2 and D3, causing the thyristor T1 to conduct. The pre-charge capacitor C2 forms an LC oscillation circuit through the thyristor T1, the current-limiting inductor L, the main power electronic switch S1, and the main power electronic switch S2, forcing the current in the main power electronic switch S1 and the main power electronic switch S2 to decrease and be turned off at the zero crossing, realizing the transfer of current to the energy-consuming branch for energy discharge.

[0029] In a preferred embodiment of the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the breakdown diode BOD1 or the breakdown diode BOD2 is an avalanche diode or a Zener diode, and its breakdown voltage is set to conduct only when the inductance voltage caused by a short circuit fault reaches a preset threshold, so as to avoid false triggering under normal fluctuations.

[0030] In a preferred embodiment of the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the pre-charge capacitor C2 or C4 is pre-charged to 50% to 100% of the rated voltage on the DC side of the system, and the charging polarity makes the discharge current direction opposite to the direction of the current in the current-carrying branch.

[0031] In a preferred embodiment of the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the main power electronic switch S1 or the main power electronic switch S2 is composed of multiple IGBT, MOSFET or IGCT devices connected in series and parallel.

[0032] In a preferred embodiment of the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the connection structure of the forward converter branch and the connection structure of the reverse converter branch are symmetrical.

[0033] In a preferred embodiment of the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the current-limiting inductor L simultaneously performs the dual functions of limiting the rate of rise of fault current and providing the induced voltage required for triggering thyristor T1.

[0034] In a preferred embodiment of the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the main power electronic switch S1 or the main power electronic switch S2 is a fully controlled semiconductor device that immediately receives a shutdown command and performs a shutdown action when it detects that the current has dropped to a set value or crossed zero.

[0035] In a preferred embodiment of the thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, the energy-consuming branch includes a metal oxide varistor (MOV).

[0036] The operating method of a thyristor-assisted converter type solid-state circuit breaker used in energy storage power stations includes: During normal operation, the main power electronic switch S1 and the main power electronic switch S2 are in the conducting state, and the load current flows through the current-limiting inductor L and the current-carrying branch. When a short-circuit fault occurs in the current-carrying branch, the fault current rises rapidly, generating an induced voltage UL on the current-limiting inductor L. The induced voltage UL and the voltage UC on the pre-charge capacitor C2 are superimposed and act on the forward commutation branch; The breakdown diode BOD1 conducts due to overvoltage, and the trigger current flows through diodes D2 and D3 into the gate of thyristor T1, causing it to conduct. The pre-charge capacitor C2 forms an LC oscillation circuit through the thyristor T1, the current-limiting inductor L, the main power electronic switch S1 and the main power electronic switch S2. Reverse current is injected into the current-passing branch, which reduces the current in the main power electronic switch S1 and the main power electronic switch S2. When the current of the main power electronic switch S1 and the main power electronic switch S2 is detected to cross zero or drop to a safe level, a shutdown signal is issued to shut down the main power electronic switch S1 and the main power electronic switch S2. The fault current is transferred to the energy-consuming branch, where the MOV absorbs the remaining energy, thus completing the fault isolation.

[0037] In one embodiment, the auxiliary commutation branch is composed of low-loss semiconductor switching devices S1 and S2. The auxiliary commutation branch is divided into two groups according to the commutation direction. The two groups have the same composition. The forward auxiliary commutation branch is composed of thyristor T1, thyristor passive triggering branch resistor R1, diodes D1 and D3, breakdown diode BOD1, Zener diode D2, filter buffer resistor R2, and capacitor C1. The self-charging branch is also divided into two groups according to the current direction. The forward self-charging branch is composed of inductor L2 and thyristor T3. The current limiting component is composed of inductor L1. The energy dissipation branch is composed of metal oxide surge arrester MOV.

[0038] (1) The current-carrying branch is composed of low-loss semiconductor switching devices S1 and S2, which are used for long-term current carrying of solid-state circuit breakers.

[0039] (2) The auxiliary converter branch is divided into two groups according to the converter direction. The two groups have the same composition. The forward auxiliary converter branch is composed of thyristor T1, thyristor passive trigger branch resistor R1, diodes D1 and D3, breakdown diode BOD1, Zener diode D2, filter buffer resistor R2, and capacitor C1. When a short circuit occurs, it is automatically triggered as the short circuit current rises, and the capacitor discharges to reduce the current of the power electronic devices in the current-carrying branch.

[0040] (3) The self-charging branch is also divided into two groups according to the current direction. The forward self-charging branch is composed of inductor L2 and thyristor T3, which is used to reverse the capacitor voltage after the turn-off.

[0041] (4) The current limiting component is composed of an inductor L1, which can limit the rate of rise of short-circuit fault current and detect short-circuit current by voltage.

[0042] (5) The energy-consuming branch is a metal oxide surge arrester (MOV) used to absorb residual energy in the system.

[0043] Under normal current-carrying conditions, the system current flows through the low-loss semiconductor switching devices S1 and S2 to maintain the normal operating current. At this time, no current flows through other branches.

[0044] When a forward current-carrying short circuit occurs, a voltage is induced on L1. The BOD1 of the auxiliary commutation branch breaks down under the combined action of the voltage of C2 and the voltage of L1, thereby triggering the thyristor T1. The pre-charge capacitor C2 in the auxiliary commutation branch discharges into the current-carrying branch, forming an LC oscillation circuit with L1, S1, S2, and T1.

[0045] When the current in inductor L1 oscillates across zero, the power electronic devices S1 and S2 in the current-carrying branch are turned off. The current continues to charge C2 through T1. When the voltage of C2 rises to a level higher than the system voltage and higher than the varistor voltage of the metal oxide surge arrester MOV, the thyristor T1 is turned off, and the current dissipates the residual energy of the system through L1 and MOV.

[0046] The capacitor self-charging process is triggered by thyristor T3. C2, L2, and T3 form an LC oscillation circuit. Due to the unidirectional conductivity of the thyristor, it will cut off when the oscillation reaches the half-wave with the opposite polarity of the capacitor voltage, thus preparing for the next short-circuit turn-off.

[0047] The reverse current flow process, short-circuit current turn-off process, and capacitor self-charging process are the same as those in claims 1, 2, and 3, with the application of another set of auxiliary commutation branches T2, C4, R3, D4, D5, D6, BOD2, R4, C3, and another set of self-charging branches T4, L3.

[0048] Figures 2(a) to 2(b) The normal current-carrying process of the circuit breaker is given. The following section will combine... Figures 2(a) to 2(b) Explain the normal flow process.

[0049] Normal flow is divided into forward flow and reverse flow. When the current is flowing in the forward direction, as shown in Figure 2(a), the current flows through the current-limiting inductor L1, the IGBT of S1, the anti-parallel diode of the IGBT of S2; When the current flows in reverse, as shown in Figure 2(b), the current flows through the current-limiting inductor L1, the anti-parallel diode of S1 IGBT, and S2 IGBT.

[0050] Figures 3(a) to 3(c) The short-circuit current turn-off process of the circuit breaker is given. The following section will combine... Figures 3(a) to 3(c) Explain this interruption process.

[0051] When a forward current short circuit occurs, as shown in Figure 3(a), a voltage is induced on L1, and the BOD1 of the auxiliary commutation branch breaks down under the combined action of the voltage of C2 and the voltage of L1.

[0052] As shown in Figure 3(b), after BOD1 breaks down, thyristor T1 is triggered, and the pre-charge capacitor C2 in the auxiliary commutation branch discharges into the current-carrying branch, forming an LC oscillation circuit with L1, S1, S2, and T1.

[0053] As shown in Figure 3(c), when the current in inductor L1 oscillates across zero, the power electronic devices S1 and S2 that turn off the current-carrying branch are shown.

[0054] The current continues to charge C2 through T1. When the voltage of C2 rises to a level higher than the system voltage and higher than the varistor voltage of the metal oxide surge arrester (MOV), the thyristor T1 is turned off, and the current dissipates the residual energy of the system through L1 and MOV.

[0055] Figures 4(a) to 4(b) The self-charging process of the circuit breaker's capacitor is given. The following section will combine... Figures 4(a) to 4(b) This explains the self-charging process.

[0056] As shown in Figure 4(a), after a short-circuit shutdown, the voltage across capacitor C2 is opposite in polarity to its pre-operation polarity, so L2 and T3 are needed to reverse it. The capacitor's self-charging process triggers thyristor T3, and C2, L2, and T3 form an LC oscillation circuit.

[0057] As shown in Figure 4(b), due to the unidirectional conductivity of the thyristor, it cuts off when the oscillation reaches the half-wave with the opposite polarity of the capacitor voltage, thus preparing for the next short-circuit turn-off.

[0058] In one embodiment, the thyristor-assisted converter-type solid-state circuit breaker for an energy storage power station comprises a current-limiting component, a converter branch, a current-carrying branch, and an energy-dissipating branch. The current-limiting component consists of a current-limiting inductor L; the converter branch consists of a thyristor T1 and passively triggered thyristor branches R1, R2, BOD1, C1, R2, D2, and D3; the current-carrying branch consists of power electronic switches S1 and S2; and the energy-dissipating branch consists of metal oxide surge arresters (MOVs). The power electronic components in the current-carrying branch are composed of series and parallel connections of power electronic components such as IGBTs (including but not limited to IGBTs, MOSFETs, and IGCTs).

[0059] The normal current-carrying state of the circuit breaker is as follows Figures 2(a) to 2(b)As shown, current flows through L and S1, S2. When a short circuit occurs, the fault current rises rapidly, inducing a UL voltage drop across the current-limiting inductor L. This voltage, superimposed with the voltage UC across capacitor C2, acts on the passive triggering branch of the thyristor. Under the combined action of the UL and UC voltages, the breakdown diode BOD1 in the thyristor triggering branch conducts due to the overvoltage. Current flows through Zener diodes D2 and D3 into the gate G of thyristor T1. Under the action of the thyristor triggering current IGK, the auxiliary commutation branch conducts, and the pre-charge capacitor C2 begins to discharge. After thyristor T1 is triggered, capacitor C2, inductors L, S1, and S2 form an LC oscillation circuit, and the current in S1 and S2 begins to decrease. When the LC oscillation current crosses zero, a signal is sent to turn off S1 and S2, and the current transfers from S1 and S2 to the MOV, where energy dissipation begins. The above explanation uses the forward current flow direction as an example. The process is the same in the reverse current flow direction, relying on capacitor C4, thyristor T2, and the passive triggering branch of the thyristor consisting of BOD2, C3, R4, D4, R3, D5, and D6. By adding a current-limiting inductor and a passive triggering branch of the thyristor, the current rise is limited while assisting the power electronic devices in commutation and turn-off, thereby improving the turning-off capability and reliability of the solid-state circuit breaker.

[0060] Furthermore, in this invention, a current-limiting inductor L is connected in series in the current-carrying branch to limit the rate of rise of the fault current (di / dt). This suppresses the rapid rise of current in the early stages of a short circuit, preventing damage to power electronic devices due to excessive current change rates. When the fault current changes abruptly, a high-amplitude induced voltage (UL = L·di / dt) is generated across the inductor. This voltage serves as the energy source for the subsequent passive triggering of the thyristor, detecting the short-circuit fault through the inductor voltage. Additionally, it triggers the thyristor, achieving a "dual-purpose inductor." Together with the pre-charge capacitor C2, it forms an oscillation circuit, providing the energy basis for forced commutation. The current-carrying branch consists of power electronic switches S1 and S2 (such as IGBTs and MOSFETs). Fully controlled devices can respond to turn-off commands within microseconds, improving the circuit breaker's operating speed. During normal operation, the on-state voltage decreases, reducing energy loss and improving system efficiency. After reverse current injection from the capacitor, the current naturally drops to near zero before turn-off, significantly reducing turn-off stress and electromagnetic interference. Pre-charge capacitors C2 (and C4) store energy and provide commutation energy. They discharge rapidly after the thyristors are turned on, generating a reverse current injection into the current-carrying branch. Together with the current-limiting inductor L, they form an LC oscillation circuit, forcing the current in the main power electronic switch to drop rapidly and turn off at the zero-crossing point, avoiding voltage spikes and device damage caused by hard turn-off. The voltage is highly adjustable: the pre-charge voltage can be flexibly set according to different system voltage levels and fault characteristics, enhancing applicability. Thyristors T1 and T2, as switching elements in the commutation branch, withstand large currents and high voltages. Thyristors have high surge current tolerance, making them suitable for conducting large currents during faults. This ensures controllable capacitor discharge current direction and precise reverse current injection. With a simple structure, low cost, and high reliability, compared to complex fully controlled devices, thyristors are more suitable as one-time commutation trigger elements. Without requiring an external controller or independent power supply, the thyristor automatically starts by triggering BOD1 through the superposition of the current-limiting inductor-induced voltage UL and the capacitor voltage UC. This eliminates the delay and fault points of traditional active control circuits, resulting in faster response and a simpler structure. By setting a breakdown voltage threshold for BOD1, it only activates during a true short-circuit fault, avoiding malfunctions under normal operation or disturbances. It conducts immediately when UL + UC exceeds its breakdown voltage, simplifying the gate drive structure and reducing cost and complexity. Nanosecond-level response speed ensures timely commutation initiation. Diodes D2 and D3 form the gate injection path, guiding the trigger current to the thyristor gate. D2 acts as an isolation layer to prevent reverse current backflow; D3 precisely injects the trigger current between the gate and cathode of T1, protecting BOD1 and the resistor branch from high-voltage backflow in the main circuit that could damage the trigger element.Metal oxide surge arresters (MOVs) act as energy-dissipating branches, absorbing fault energy: after the main switch is turned off, they receive the transferred fault current, safely dissipating the magnetic energy and some capacitive energy stored in the system; preventing overvoltage damage to other equipment during the breaking process; their nonlinear volt-ampere characteristics adapt to a wide range of energy absorption, conducting significantly even when the voltage slightly exceeds the threshold, providing strong protection capabilities. The bidirectional symmetrical topology supports bidirectional power flow in energy storage systems, suitable for forward and reverse current breaking in scenarios such as battery charging and discharging, and photovoltaic grid connection; it improves system symmetry and protection integrity, achieving fast protection with equivalent performance regardless of whether the fault occurs in charging or discharging mode. The main power electronic switch is composed of IGBTs / MOSFETs / IGCTs connected in series and parallel, meeting the requirements of high-voltage, high-current applications: by expanding the withstand voltage and current carrying capacity through series and parallel connections, it adapts to the high power levels of energy storage power stations; the failure of a single device does not affect the overall function, facilitating modular design and maintenance.

[0061] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0062] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A thyristor-assisted converter type solid-state circuit breaker for energy storage power stations, characterized in that, It consists of a current-limiting component, a commutation branch, a current-carrying branch, and an energy-dissipating branch. The current-carrying branch includes at least one set of main power electronic switches S1 and S2 connected in series to conduct the load current under normal operating conditions. The current-limiting component includes a current-limiting inductor L connected in series with the current-carrying branch. The commutation branch is connected in parallel across the current-limiting component and the current-carrying branch. The commutation branch includes a forward commutation branch and a reverse commutation branch connected in parallel. The forward commutation branch includes a thyristor T1, a first thyristor passive triggering branch connected in parallel with the thyristor T1, and a pre-charge capacitor C2 connected in series with the thyristor T1. The first thyristor passive triggering branch includes a resistor R1, a diode D1, a breakdown diode BOD1 connected in series, and a resistor R2 and a capacitor C1 connected in parallel. The reverse commutation branch... One end of diodes D2 and D3 are connected to thyristor T1, and the other end is connected between the breakdown diode BOD1 and the parallel resistor R2 and capacitor C1. The reverse commutation branch includes thyristor T2, the second thyristor passive triggering branch connected in parallel with thyristor T2, and the pre-charge capacitor C4 connected in series with thyristor T2. The second thyristor passive triggering branch includes the series resistor R3, diode D4, breakdown diode BOD2, and the parallel resistor R4 and capacitor C3. One end of diodes D5 and D6 connected in reverse series is connected to thyristor T2, and the other end is connected between the breakdown diode BOD2 and the parallel resistor R4 and capacitor C3. The energy dissipation branch is connected in parallel across the current-carrying branch to absorb the energy released during the fault.

2. The thyristor-assisted converter type solid-state circuit breaker for energy storage power stations as described in claim 1, characterized in that, Preferably, when a short circuit fault occurs in the current-carrying branch, a positive voltage UL is induced on the current-limiting inductor L. The positive voltage UL is superimposed with the initial voltage UC on the pre-charge capacitor C2 and applied to the passive triggering branch of the first thyristor, causing the breakdown diode BOD1 to break down and conduct. Then, a trigger current is injected into the gate of the thyristor T1 through diodes D2 and D3, causing the thyristor T1 to conduct. The pre-charge capacitor C2 forms an LC oscillation circuit through the thyristor T1, the current-limiting inductor L, the main power electronic switch S1, and the main power electronic switch S2, forcing the current in the main power electronic switch S1 and the main power electronic switch S2 to decrease and be turned off at the zero crossing, realizing the transfer of current to the energy-consuming branch for energy discharge.

3. The thyristor-assisted converter type solid-state circuit breaker for energy storage power stations as described in claim 1, characterized in that, The breakdown diode BOD1 or BOD2 is an avalanche diode or a Zener diode, and its breakdown voltage is set to conduct only when the inductance voltage caused by a short circuit fault reaches a preset threshold, so as to avoid false triggering under normal fluctuations.

4. The thyristor-assisted converter type solid-state circuit breaker for energy storage power stations as described in claim 1, characterized in that, The pre-charge capacitor C2 or C4 is pre-charged to 50% to 100% of the rated voltage on the DC side of the system, and the charging polarity makes the discharge current direction opposite to the direction of the current in the current-carrying branch.

5. The thyristor-assisted converter type solid-state circuit breaker for energy storage power stations as described in claim 1, characterized in that, The main power electronic switch S1 or the main power electronic switch S2 is composed of multiple IGBT, MOSFET or IGCT devices connected in series and parallel.

6. The thyristor-assisted converter type solid-state circuit breaker for energy storage power stations as described in claim 1, characterized in that, The connection structures of the forward converter branch and the reverse converter branch are symmetrical.

7. The thyristor-assisted converter type solid-state circuit breaker for energy storage power stations as described in claim 1, characterized in that, The current-limiting inductor L serves the dual function of limiting the rate of rise of the fault current and providing the induced voltage required to trigger the thyristor T1.

8. The thyristor-assisted converter type solid-state circuit breaker for energy storage power stations as described in claim 1, characterized in that, The main power electronic switch S1 or the main power electronic switch S2 is a fully controlled semiconductor device. When the current drops to the set value or crosses zero, it immediately receives the shutdown command and executes the shutdown action.

9. The thyristor-assisted converter type solid-state circuit breaker for energy storage power stations as described in claim 1, characterized in that, The power-consuming branch includes a metal oxide varistor (MOV).

10. A method of operating a thyristor-assisted converter type solid-state circuit breaker for an energy storage power station as described in any one of claims 1-9.

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