Hybrid direct-current circuit breaker capable of selectively turning off fault circuit
By designing a hybrid DC circuit breaker that transfers current through a current-limiting branch, the problem of unnecessary interruption during transient faults in hybrid DC circuit breakers is solved, thereby improving the stability and reliability of the power system.
Patent Information
- Application Number
- CN202422567116.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-23
- Publication Date
- 2025-11-14
- Estimated Expiration
- 2034-10-23
AI Technical Summary
Existing hybrid DC circuit breakers can interrupt circuits during transient faults, affecting the reliable and stable operation of the power system.
Design a hybrid DC circuit breaker that includes a current-limiting branch, a semiconductor commutation branch, a thyristor-controlled turn-off branch, and a fast mechanical switching branch. The current-limiting branch transfers current during transient faults to avoid direct circuit interruption and restores normal operation after the fault is cleared.
It improves the stability and reliability of the power system, avoids unnecessary circuit interruptions caused by transient faults, and ensures rapid system recovery.
Smart Images
Figure CN223553029U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a hybrid DC circuit breaker that can selectively shut off faulty circuits, belonging to the field of power electronics technology. Background Technology
[0002] With the large-scale grid connection of new energy power generation, flexible DC transmission has gained increasingly widespread application due to its advantages such as long-distance, large-capacity, and low-loss transmission. Compared with AC systems, DC systems, due to their low impedance, experience a faster rise rate and higher peak value of fault current when a short-circuit fault occurs. Furthermore, DC fault currents do not have a natural zero-crossing point, making interruption more difficult, and traditional circuit breakers are insufficient to meet the requirements. Therefore, researching new types of DC circuit breakers to reliably interrupt DC fault currents is of great significance for the stable operation of the system.
[0003] Based on different topologies, DC circuit breakers can be classified into: traditional mechanical DC circuit breakers, solid-state DC circuit breakers, and hybrid DC circuit breakers. Based on the method of interrupting fault current, DC circuit breakers can be divided into zero-current interruption and zero-voltage interruption. Zero-voltage interruption refers to the DC circuit breaker directly disconnecting the switch through the operating mechanism to create a break; zero-current interruption refers to injecting a directional current to make the current in the break branch zero when interrupting fault current, thereby interrupting the circuit. No arc is generated during the switching process. Traditional mechanical DC circuit breakers consist of a mechanical switch and a power-dissipating branch. During normal system operation, the system current flows through the mechanical switch branch, resulting in a large current carrying capacity and low losses, but a slow breaking speed. With the development of power electronics technology, solid-state DC circuit breakers have emerged. Compared to traditional mechanical DC circuit breakers, solid-state DC circuit breakers have significantly improved breaking speed. However, during normal current carrying, the conduction voltage drop and conduction resistance of power electronic devices cause significant on-state losses, limiting their development.
[0004] Hybrid DC circuit breakers combine the advantages of traditional mechanical DC circuit breakers and solid-state DC circuit breakers, and have broad application prospects. The topology of a hybrid DC circuit breaker includes a fast mechanical switching branch, a power electronic converter branch, a buffer branch, and a power dissipation branch. During normal system operation, the system current flows through the fast mechanical switching branch, resulting in high current capacity and low loss. In the event of a fault, the power electronic converter branch participates in the turn-off, providing rapid turn-off. However, current hybrid DC circuit breakers interrupt the circuit not only in the event of a permanent fault but also in the event of a transient fault. This is detrimental to the reliable and stable operation of the system and can negatively impact power quality. Utility Model Content
[0005] The purpose of this invention is to provide a hybrid DC circuit breaker that can selectively shut down faulty circuits, in order to solve the problem that the circuit cannot be selectively interrupted according to the fault type when a fault occurs in the power grid.
[0006] To achieve the above objectives, the solution of this utility model includes:
[0007] This utility model discloses a hybrid DC circuit breaker that can selectively shut off fault circuits, including a current limiting branch, a semiconductor commutation branch, a thyristor-controlled shutdown branch, and a fast mechanical switch branch connected in series with a fast mechanical switch.
[0008] A fast mechanical switch branch is used in series with the positive busbar;
[0009] The semiconductor commutation branch is connected in parallel with the fast mechanical switch branch, and the semiconductor commutation branch is connected in series with a first thyristor whose conduction direction is in the direction of the power supply current.
[0010] The thyristor-controlled turn-off branch includes a first capacitor with one end connected to the first thyristor cathode and the other end connected to the negative busbar, a second capacitor connected in series between the positive busbar and the negative busbar, and a second thyristor with the conduction direction facing the negative busbar.
[0011] The current-limiting branch is connected in parallel with the fast mechanical switch branch. The current-limiting branch includes a first resistor and a mechanical switch connected in series.
[0012] Furthermore, it also includes a first inductor connected in series with a fast mechanical switch and a first diode connected in reverse parallel across the first inductor.
[0013] Furthermore, the semiconductor commutation branch also includes a second inductor connected in series with the first thyristor and a second diode connected in reverse parallel across the second inductor.
[0014] Furthermore, it also includes a third diode connected between the positive bus and the negative bus, with the conduction direction of the third diode pointing towards the positive bus.
[0015] Furthermore, the first and second thyristors are semi-controlled thyristors.
[0016] Furthermore, the fast mechanical switch is driven by an electromagnetic mechanism for rapid response in opening and closing.
[0017] Furthermore, the thyristor-controlled turn-off branch also includes a second resistor connected in parallel across the second capacitor.
[0018] Furthermore, the first and second thyristors are two sets of anti-parallel thyristors.
[0019] The beneficial effects of this utility model are as follows:
[0020] This invention is groundbreaking. The hybrid DC circuit breaker of this invention, capable of selectively shutting off fault circuits, utilizes a current-limiting branch instead of the energy-consuming branch in traditional hybrid DC circuit breakers. When a permanent fault occurs, the fast-acting mechanical switch is disconnected, creating a break and interrupting the circuit. When a transient fault occurs, the fast-acting mechanical switch is first disconnected to transfer the current to the current-limiting branch. After a predetermined time interval, once the fault is cleared, a closing command is issued, transferring the current back to the fast-acting mechanical switch branch, and the system returns to normal operation. This hybrid DC circuit breaker avoids directly interrupting the circuit during transient faults, greatly improving the stability and reliability of power system operation. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the main structure of a hybrid DC circuit breaker that can selectively shut down faulty circuits.
[0022] Figure 2 This is a schematic diagram of the current flow of a hybrid DC circuit breaker that can selectively shut off faulty circuits during normal operation.
[0023] Figure 3 This is a schematic diagram of the current transfer to the semiconductor commutation branch of a hybrid DC circuit breaker that can selectively shut down faulty circuits.
[0024] Figure 4 This is a schematic diagram of the current transfer to the current-limiting branch of a hybrid DC circuit breaker that can selectively shut off faulty circuits.
[0025] Figure 5 This is another schematic diagram of the current transfer to the current-limiting branch of a hybrid DC circuit breaker that can selectively shut off faulty circuits.
[0026] Figure 6 This is a schematic diagram of the current transfer to the fast mechanical switch branch of a hybrid DC circuit breaker that can selectively shut off faulty circuits.
[0027] Figure 7 This is a schematic diagram of the discharge current flow when a hybrid DC circuit breaker circuit that can selectively shut off faulty circuits is turned off.
[0028] Figure 8 This is a schematic diagram of a hybrid DC circuit breaker that can selectively shut down faulty circuits in both directions. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments.
[0030] The present invention provides a hybrid DC circuit breaker capable of selectively shutting off faulty circuits, utilizing a current-limiting branch to replace the energy-consuming branch in traditional hybrid DC circuit breakers. In the event of a permanent fault, the fast-acting mechanical switch is disconnected, creating a break and interrupting the circuit. In the event of a transient fault, the fast-acting mechanical switch is first disconnected to transfer the current to the current-limiting branch. After a predetermined time interval, once the fault is cleared, a closing command is issued to transfer the current back to the fast-acting mechanical switch branch, and the system returns to normal operation. This hybrid DC circuit breaker avoids directly interrupting the circuit during transient faults, significantly improving the stability and reliability of power system operation.
[0031] Example:
[0032] like Figure 1 The hybrid DC circuit breaker shown is a selectively shut-off fault circuit, which consists of a fast mechanical switching branch, a semiconductor commutation branch, a thyristor-controlled shutdown branch and a current limiting branch, and also includes a first inductor L1 connected in series with the fast mechanical switching branch on the positive bus and a first diode D1 connected in reverse parallel across L1.
[0033] The fast mechanical switch branch consists of the fast mechanical switch FMS, which is connected in series with L1.
[0034] The semiconductor commutation branch consists of a first thyristor T1 with the conduction direction pointing in the direction of the supply current, a second inductor L2 connected in series with T1, and a second diode D2 connected in reverse parallel across L2. The semiconductor commutation branch is connected in parallel with the fast mechanical switch branch.
[0035] The thyristor-controlled turn-off branch includes a first capacitor C1 with one end connected to the cathode of T1 and the other end connected to the negative busbar, a second capacitor C2 connected in series between the positive busbar and the negative busbar, a second thyristor T2, and a second resistor R2 connected in parallel across the second capacitor C2. The conduction direction of T2 is towards the negative busbar.
[0036] The current-limiting branch consists of the first resistor R1 connected in series and the mechanical switch MS. The current-limiting branch is connected in parallel with the fast mechanical switch branch.
[0037] In addition, this circuit breaker also contains a third diode D3, whose cathode is connected to the positive busbar and whose anode is connected to the negative busbar.
[0038] The working principle of this circuit breaker is as follows: When the system is normally conducting current, the current flow direction is as follows: Figure 2As shown, mechanical switch MS and fast mechanical switch FMS remain closed, while the first thyristor T1 and the second thyristor T2 remain open. Since the contact resistance of the fast mechanical switch FMS is much smaller than that of the first resistor R1, the system current flows through the branch of the fast mechanical switch. When a system fault occurs, the circuit breaker needs to operate to limit the fault current or shut down the faulty circuit. The entire operation process can be divided into the following steps:
[0039] (1) When a fault occurs, the current flows as follows Figure 3 As shown, after the trip signal is issued, the drive circuit is triggered to disconnect the fast mechanical switch FMS and simultaneously control the first thyristor T1 to turn on. Under the action of the arc voltage, the system current is transferred from the fast mechanical switch branch to the semiconductor commutation branch. At the same time, the first capacitor C1 in the thyristor control turn-off branch is charged to prepare for the commutation turn-off of the first thyristor T1. The first inductor L1 plays a current limiting role.
[0040] (2) For example Figure 4 and Figure 5 As shown, when the second thyristor T2 is turned on, the first capacitor C1 discharges through the second capacitor C2 and the second thyristor T2 to generate a reverse current. At the same time, the current also flows through the second resistor R2, which controls the first thyristor T1 to commutate and turn off. Then, the second thyristor T2 turns off at zero under the action of the bus voltage and the capacitor voltage of the second capacitor C2, and the system current is transferred to the current-limiting branch.
[0041] (3) such as Figure 3 , Figure 4 and Figure 6 As shown, if a transient fault occurs, after a predetermined time limit, the first thyristor T1 is turned on, the current is transferred from the current limiting branch to the semiconductor commutation branch, and the first capacitor C1 is charged again. The second thyristor T2 is turned on and a closing signal is sent to trigger the drive circuit to close the fast mechanical switch FMS. The first thyristor T1 is turned off, and the current is transferred back to the fast mechanical switch branch.
[0042] (4) such as Figure 3 , Figure 4 and Figure 7 As shown, if a permanent fault occurs, the first thyristor T1 is turned on, and the current is transferred to the semiconductor commutation branch. Then, the mechanical switch MS is turned off, the second thyristor T2 is turned on, the first thyristor T1 is turned off, the second capacitor C2 discharges through the second resistor R2, and the inductance stored in the first inductor L1 and the second inductor L2 is released through the anti-parallel first diode D1 and the second diode D2, respectively, thus completing the circuit shutdown.
[0043] In the semiconductor commutation branch and the thyristor-controlled turn-off branch, the first thyristor T1 and the second thyristor T2 are semi-controlled devices. When the current flowing through them decreases to zero, the devices turn off. The fast mechanical switch FMS is driven by an electromagnetic mechanism and has a faster response speed and opening / closing speed than the mechanical switch MS.
[0044] As another implementation method: such as Figure 8 As shown, by replacing thyristors T1 and T2 with two sets of anti-parallel thyristors, bidirectional switching of the circuit can be achieved.
Claims
1. A hybrid DC circuit breaker capable of selectively shutting off faulty circuits, characterized in that, It includes current-limiting branches, semiconductor commutation branches, thyristor-controlled turn-off branches, and fast mechanical switch branches connected in series with fast mechanical switches; The fast mechanical switch branch is connected in series with the positive busbar; The semiconductor commutation branch is connected in parallel with the fast mechanical switch branch, and the semiconductor commutation branch is connected in series with a first thyristor whose conduction direction points to the direction of the power supply current. The thyristor-controlled turn-off branch includes a first capacitor with one end connected to the first thyristor cathode and the other end connected to the negative busbar, a second capacitor connected in series between the positive busbar and the negative busbar, and a second thyristor with the conduction direction facing the negative busbar. The current-limiting branch is connected in parallel with the fast mechanical switch branch, and the current-limiting branch includes a first resistor and a mechanical switch connected in series.
2. The hybrid DC circuit breaker with selective fault-blocking capability according to claim 1, characterized in that, It also includes a first inductor connected in series with the fast mechanical switch and a first diode connected in reverse parallel across the first inductor.
3. The hybrid DC circuit breaker with selective fault-blocking capability according to claim 1, characterized in that, The semiconductor commutation branch also includes a second inductor connected in series with the first thyristor and a second diode connected in reverse parallel across the second inductor.
4. The hybrid DC circuit breaker with selective fault-blocking capability according to claim 1, characterized in that, It also includes a third diode connected between the positive bus and the negative bus, wherein the conduction direction of the third diode is directed towards the positive bus.
5. The hybrid DC circuit breaker with selective fault-blocking capability according to claim 1, characterized in that, The first and second thyristors are semi-controlled thyristors.
6. The hybrid DC circuit breaker with selective fault-shutting capability according to claim 1, characterized in that, The fast mechanical switch is driven by an electromagnetic mechanism for rapid response in opening and closing.
7. The hybrid DC circuit breaker with selective fault-blocking capability according to claim 1, characterized in that, The thyristor-controlled shutdown branch also includes a second resistor connected in parallel across the second capacitor.
8. The hybrid DC circuit breaker with selective fault-blocking capability according to claim 1, characterized in that, The first and second thyristors are two sets of anti-parallel thyristors.