Circuit breaker with current limiting reactor LR switching function

Abstract

The invention provides a circuit breaker with a current-limiting reactor LR switching function. The circuit breaker comprises a mechanical switch K1, a first thyristor D1, a current-limiting reactor LR, a coupling inductor LO and a power supply VDD, the positive electrode of the mechanical switch K1 is respectively connected with the current limiting reactor LR, the first thyristor D1 and the power supply VDD; the negative electrode of the mechanical switch K1 is respectively connected with the current limiting reactor LR, the first thyristor D1 and the vacuum switch K2 through the primary side of the coupling inductor LO; the negative electrode of the vacuum switch K2 is connected with the negative electrode of the power supply VDD through the load R. When the circuit breaker is in rated operation, current only passes through the mechanical switch and the vacuum switch, so that the system loss is reduced, and the energy transmission efficiency of the circuit breaker is improved; in a fault state, the current limiting reactor is put into use, so that the effect of limiting the rising rate of the fault current of the system can be achieved, and favorable guarantee is provided for fault removal of the circuit breaker; and the speed of transferring the fault transient current from the mechanical switch to the current limiting reactor is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit breakers, in particular to a circuit breaker with a current limiting reactor LR switching function. Background Art

[0002] With the widespread application of DC power supply technology in new energy, electric vehicles, high-voltage DC transmission (HVDC), and DC microgrids, DC system protection issues are gaining increasing attention. As a key protection device in DC systems, DC mechanical circuit breakers can effectively interrupt fault currents and protect power equipment from damage.

[0003] However, compared to AC systems, DC systems have no natural zero-crossing point for current. The rapid rise of fault current and the maintenance of arcs pose many challenges to the design and implementation of DC circuit breakers. DC mechanical circuit breakers are an important fault isolation device in DC systems, mainly consisting of a mechanical switch K1 and an auxiliary commutation circuit. Mechanical switch K1 serves as the main current path, responsible for breaking the DC fault current, while the auxiliary commutation circuit is used to achieve current switching and energy dissipation. During the circuit breaking process, the fault current is first transferred to the energy absorption element (such as a resistor or metal oxide varistor MOV) through the auxiliary commutation circuit, thereby reducing the current when the mechanical switch K1 is broken and reducing the difficulty of arc maintenance. After the commutation is completed, the mechanical switch K1 is quickly disconnected to achieve complete isolation of the circuit.

[0004] As DC system fault interruption currents increase, higher requirements are placed on circuit breaker interruption capabilities. When a short-circuit fault occurs in a DC system, the fault current rises rapidly. Failure to isolate the fault promptly can severely damage the system. Current-limiting reactors (LR), as current-limiting devices, can limit the rate of rise of fault current during transient conditions. Currently, circuit breaker structures with current-limiting capabilities connect the reactor in series with the rated current circuit. During rated operation, the rated current flows through the reactor. This increases circuit breaker losses and places higher demands on the power of the reactor. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a circuit breaker with a current limiting reactor LR switching function. The present invention can enable the current limiting reactor LR to operate only in a fault disconnecting state. During stable operation, the current is conducted by a mechanical switch K1.

[0006] The technical solution of the present invention is: a circuit breaker with a current-limiting reactor LR switching function, comprising a mechanical switch K1, a first thyristor D1, a current-limiting reactor LR, a coupling inductor LO, and a power supply VDD; the positive electrode of the mechanical switch K1 is respectively connected to one end of the current-limiting reactor LR, the anode of the first thyristor D1, and the positive electrode of the power supply VDD; the negative electrode of the mechanical switch K1 is connected to one end of the primary side of the coupling inductor LO;

[0007] The other end of the primary side of the coupling inductor LO is connected to the current limiting reactor LR, the cathode of the first thyristor D1, and the positive electrode of the vacuum switch K2 respectively; the negative electrode of the vacuum switch K2 is connected to the negative electrode of the power supply VDD through the load R.

[0008] Preferably, the other end of the primary side of the coupled inductor LO is also connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the anode of the second thyristor D2 via the second capacitor C2; the cathode of the second thyristor D2 is connected to the negative electrode of the power supply VDD via the load R.

[0009] Preferably, the other end of the primary side of the coupling inductor LO is also connected to the lightning arrester F, and the other end of the lightning arrester F is connected to the negative electrode of the power supply VDD via the load R.

[0010] Preferably, the secondary side of the coupled inductor LO is further connected in series with a third thyristor D3 and a first capacitor C1.

[0011] Preferably, when the circuit breaker is in a stable working state, the mechanical switch K1 and the vacuum switch K2 are turned on; the first thyristor D1 and the second thyristor D2 are in an off state; the system rated current flows from the power supply VDD side to the load R side through the mechanical switch K1 and the vacuum switch K2;

[0012] When the circuit breaker is in a fault-open state, the third thyristor D3 is triggered, the first capacitor C1 begins to discharge, and a voltage is induced on the primary side of the coupled inductor LO. As a result, the voltage in the branch formed by the mechanical switch K1 and the primary side of the coupled inductor LO rises. Furthermore, by triggering the first thyristor D1 to turn on and off, the current is commutated from the mechanical switch K1 to the current-limiting reactor LR, so that the current-limiting reactor LR plays a current-limiting role.

[0013] The beneficial effects of the present invention are:

[0014] 1. When the circuit breaker of the present invention is in rated operation, the current only passes through the mechanical switch and the vacuum switch, which reduces system loss and improves the energy transmission efficiency of the circuit breaker;

[0015] 2. In the event of a fault, the present invention puts the current-limiting reactor into operation, which can limit the rate of increase of the system fault current, thereby providing a favorable guarantee for the circuit breaker to cut off the fault;

[0016] 3. The present invention adopts a coordinated approach of a mechanical switch, a coupled inductor and a first thyristor to increase the rate at which the fault transient current is transferred from the mechanical switch to the current-limiting reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a circuit structure diagram of the circuit breaker of the present invention;

[0018] Figure 2 This is a current waveform diagram of the mechanical switch K1 when simulating fault current interruption in an embodiment of the present invention;

[0019] Figure 3 This is a current waveform diagram of the first thyristor D1 when simulating fault current interruption in an embodiment of the present invention;

[0020] Figure 4 This is a current waveform diagram of the current limiting reactor LR when simulating fault current interruption in an embodiment of the present invention;

[0021] Figure 5 This is a current waveform diagram of the vacuum switch K2 when simulating fault current interruption according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0023] like Figure 1 As shown, the present invention provides a circuit breaker with a current limiting reactor LR switching function, comprising a mechanical switch K1, a first thyristor D1, a current limiting reactor LR, a coupling inductor LO, and a power supply VDD; the positive electrode of the mechanical switch K1 is respectively connected to one end of the current limiting reactor LR, the anode of the first thyristor D1, and the positive electrode of the power supply VDD; the negative electrode of the mechanical switch K1 is connected to one end of the primary side of the coupling inductor LO;

[0024] The other end of the primary side of the coupling inductor LO is connected to the current limiting reactor LR, the cathode of the first thyristor D1, and the positive electrode of the vacuum switch K2 respectively; the negative electrode of the vacuum switch K2 is connected to the negative electrode of the power supply VDD through the load R.

[0025] The other end of the primary side of the coupling inductor LO is also connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the anode of the second thyristor D2 via the second capacitor C2; the cathode of the second thyristor D2 is connected to the negative electrode of the power supply VDD via the load R.

[0026] The other end of the primary side of the coupling inductor LO is also connected to the lightning arrester F, and the other end of the lightning arrester F is connected to the negative electrode of the power supply VDD via the load R.

[0027] The secondary side of the coupling inductor LO is further connected in series with a third thyristor D3 and a first capacitor C1.

[0028] When the circuit breaker is in a stable working state, the mechanical switch K1 and the vacuum switch K2 are turned on; the first thyristor D1 and the second thyristor D2 are in the off state; the system rated current flows from the power supply VDD side to the load R side through the mechanical switch K1 and the vacuum switch K2;

[0029] When the circuit breaker is in a fault-breaking state, and when the system is in a fault-breaking state, the mechanical switch K1 and the vacuum switch K2 begin to open, and the first thyristor D1, the second thyristor D2, and the third thyristor D3 are triggered to conduct. The primary side of the coupled inductor LO induces a voltage, and the branch voltage formed by the mechanical switch K1 rises. Therefore, the current can be transferred from the mechanical switch K1 to the first thyristor D1. The first thyristor D1 is turned off when the current passes through zero, and the current is transferred to the current-limiting reactor LR. The current-limiting reactor LR plays a fault current-limiting role, thereby limiting the rise of the fault current. The second capacitor C2 begins to discharge after the second thyristor D2 is triggered to conduct. When the capacitor discharge current is equal to the system fault current, the vacuum switch K2 current drops to 0 and is turned off. The remaining energy of the system is dissipated through the lightning arrester F. When the system energy dissipation is completed, the circuit breaker is disconnected.

[0030] To verify this embodiment, a simulation model was built in simulation software to examine the circuit breaker's interruption response when the system's rated current was 4kA and the circuit breaker's fault current was 40kA. In this simulation, the power supply voltage was 1.5kV, the simulated circuit breaker fault occurred at t = 50ms, and the circuit breaker began operating at t = 50ms.

[0031] Depend on Figures 2 to 5 It can be seen that because the first thyristor D1 quickly turns on in the fault state, the current of the mechanical switch K1 is quickly transferred to the first thyristor D1, and its current quickly drops to 0, while the current of the first thyristor D1 rises rapidly. After the first thyristor D1 turns off, the current is transferred to the current-limiting reactor LR, which limits the rate of rise of the fault current. After the vacuum switch K2 opens, the current of the current-limiting reactor LR drops to 0. In the simulation, the short-circuit current is set to 40kA, but during the actual opening process, the circuit breaker begins to function when the fault current rises to approximately 5.5kA, and the current of the vacuum switch K2 gradually drops to 0, thus shutting down. The simulation verifies the current-limiting effect of the current-limiting reactor and the feasibility of the commutation method of this embodiment.

[0032] Compared to traditional mechanical vacuum circuit breakers, the circuit breaker with a current-limiting reactor proposed in this embodiment can limit the rate of rise of fault current, thereby reducing the harm of fault current to the system. Compared to the method of directly connecting the current-limiting reactor in series with the system, this embodiment adopts a current-limiting reactor switching method. The current-limiting reactor only flows the fault current when the fault is in the interrupting state. Therefore, in steady-state operation, the circuit breaker has higher energy transmission efficiency. The current-limiting reactor only needs to conduct transient fault current and does not need to operate in the rated operating state for a long time, which can reduce the power demand of the current-limiting reactor.

[0033] The above embodiments and descriptions are only for explaining the principles and best embodiments of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, which shall fall within the scope of the invention to be protected.

Claims

1. A circuit breaker with a current limiting reactor LR switching function, characterized in that: It includes a mechanical switch K1, a first thyristor D1, a current limiting reactor LR, a coupled inductor LO, and a power supply VDD; the positive electrode of the mechanical switch K1 is connected to one end of the current limiting reactor LR, the anode of the first thyristor D1, and the positive electrode of the power supply VDD respectively; the negative electrode of the mechanical switch K1 is connected to one end of the primary side of the coupled inductor LO; The other end of the primary side of the coupling inductor LO is respectively connected to the current limiting reactor LR, the cathode of the first thyristor D1, and the positive electrode of the vacuum switch K2; the negative electrode of the vacuum switch K2 is connected to the negative electrode of the power supply VDD via the load R; the other end of the primary side of the coupling inductor LO is also connected to the negative electrode of the power supply VDD via the second thyristor D2 and the load R; and the secondary side of the coupling inductor LO is further connected in series with a third thyristor D3.

2. A circuit breaker with a current limiting reactor LR switching function according to claim 1, characterized in that: The other end of the primary side of the coupling inductor LO is also connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the anode of the second thyristor D2 via the second capacitor C2; the cathode of the second thyristor D2 is connected to the negative electrode of the power supply VDD via the load R.

3. A circuit breaker with a current limiting reactor LR switching function according to claim 2, characterized in that: The other end of the primary side of the coupling inductor LO is also connected to the lightning arrester F, and the other end of the lightning arrester F is connected to the negative electrode of the power supply VDD via the load R.

4. A circuit breaker with a current limiting reactor LR switching function according to claim 1, characterized in that: The secondary side of the coupling inductor LO is further connected in series with a first capacitor C1.

5. The circuit breaker with the current limiting reactor LR switching function according to claim 1, characterized in that: When the circuit breaker is in a stable working state, the mechanical switch K1 and the vacuum switch K2 are turned on; the first thyristor D1 and the second thyristor D2 are in the off state; the system rated current flows from the power supply VDD side to the load R side through the mechanical switch K1 and the vacuum switch K2.

6. A circuit breaker with a current limiting reactor LR switching function according to claim 5, characterized in that: When the circuit breaker is in a fault-opening state, the mechanical switch K1 and the vacuum switch K2 begin to open, and the first thyristor D1, the second thyristor D2, and the third thyristor D3 are triggered to conduct. A voltage is induced on the primary side of the coupled inductor LO, and the voltage of the branch formed by the mechanical switch K1 increases. As a result, the current is transferred from the mechanical switch K1 to the first thyristor D1. The first thyristor D1 is turned off when the current passes through zero, and the current is transferred to the current-limiting reactor LR. The current-limiting reactor LR performs a fault current-limiting function, limiting the rise of the fault current. The second capacitor C2 begins to discharge after the second thyristor D2 is triggered to conduct. When the capacitor discharge current equals the system fault current, the current of the vacuum switch K2 drops to zero and is turned off. The remaining energy of the system is dissipated through the lightning arrester F. When the system energy dissipation is completed, the circuit breaker is disconnected.

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