CN110048377A - The hybrid dc circuit breaker of multiport and control method suitable for DC distribution net - Google Patents

Abstract

The invention discloses a multi-port hybrid DC circuit breaker suitable for a DC distribution network and a control method, comprising: a main branch, a transfer branch and an energy consumption branch connected in parallel; the main branch includes: a plurality of The main branch units connected in parallel, each main branch unit is connected between the DC bus and its outlet; each main branch unit includes: an isolation switch, a fast mechanical switch and a load transfer switch connected in series in sequence; the isolation switch Connected to the outlet of the DC bus, the load transfer switch is connected to the DC bus; each main branch unit is connected to the transfer branch through a diode, and the DC bus is connected to the transfer branch through a diode. The beneficial effects of the invention are as follows: the multi-port hybrid DC circuit breaker can realize the opening and closing of normal lines, isolate fault lines or bus bars, and has the capability of fast mechanical switch failure protection.

Description

Multi-port hybrid DC circuit breaker suitable for DC distribution network and control method

technical field

The invention relates to the technical field of DC side fault clearance and isolation of a flexible DC distribution network, in particular to a multi-port hybrid DC circuit breaker suitable for a DC distribution network and a control method.

Background technique

The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

With the large-scale access of distributed power sources, the increase of DC loads and the demand for high-reliability power supply, the flexible DC distribution network based on modular multi-level converters has become a research hotspot at home and abroad.

In order to improve the reliability of power supply in the flexible DC distribution network, most of the converter stations are of symmetrical single-pole structure, and the ungrounded operation mode is adopted. When a single-pole grounding fault occurs on the DC side of the DC distribution network, due to the large resistance in the fault path, the fault current is mainly the charging and discharging current of the distributed capacitance of the DC line, and the amplitude is small and quickly decays to zero. The grid can operate with short-term faults. However, once an inter-pole short-circuit fault occurs on the DC side, the parallel capacitors of each DC/AC converter, DC/DC converter and converter station in the DC distribution network will discharge to the fault point at the same time, and the fault current will be discharged in a very short period of time. (millisecond level) will rise to a very large value. Therefore, in order to ensure the continued operation of sound lines in the DC distribution network and to avoid damage to the fragile power electronics in the converter station, the fault must be cleared and isolated within a few milliseconds. This characteristic of flexible DC distribution network determines that the required DC circuit breakers are very different from AC circuit breakers.

At present, DC circuit breakers mainly include mechanical DC circuit breakers, all-solid-state DC circuit breakers and hybrid DC circuit breakers. The mechanical DC circuit breaker has the characteristics of low investment and low operating loss, but because it uses a mechanical device and needs to extinguish the arc, the action speed is slow and the reliability is low. All solid-state DC circuit breakers use power electronic devices to break the fault current without breaking arcs, so the action speed is extremely fast, but because the load current needs to flow through a large number of power electronic devices during normal operation, the operating loss is large. The concept of hybrid DC circuit breaker was originally proposed by ABB, which combines the advantages of mechanical DC circuit breaker and all-solid-state DC circuit breaker, and has the characteristics of low operating loss and fast action speed. In the field of high-voltage flexible DC transmission, the 500kV hybrid DC circuit breaker developed by NARI Relay Company has been able to break the fault current of 25kA within 3ms.

The inventor found that although the hybrid DC circuit breaker has many excellent characteristics, it requires a large number of power electronic devices to bear the transient breaking voltage, so the cost is high, and it is difficult to be applied to the DC distribution network on a large scale.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention makes full use of the forced commutation characteristics of the branch of the hybrid DC circuit breaker, proposes a new multi-port hybrid DC circuit breaker and a control method, and analyzes its action under various working conditions process; the primary equipment investment of the DC circuit breaker is greatly reduced by sharing the transfer branch and the energy-consuming branch for each line.

In some embodiments, the following technical solutions are adopted:

A multi-port hybrid DC circuit breaker suitable for a DC distribution network includes: a main branch, a transfer branch and an energy consumption branch connected in parallel; the main branch includes: a plurality of main branch units connected in parallel, each A main branch unit is connected between the DC bus and its outgoing line; each main branch unit includes: an isolating switch, a fast mechanical switch and a load transfer switch connected in series in sequence; the isolating switch is connected with the outgoing line of the DC bus, the The load transfer switch is connected with the DC bus; each main branch unit is connected with the transfer branch through a diode, and the DC bus is connected with the transfer branch through a diode.

When the system is in normal operation, the load current flows through each main branch, and each diode has no current flow. When the line or bus fails, after the load transfer switch of the main branch is locked, the fault current will be commutated to the transfer branch through the diodes D1-D6 connected to each main branch unit and the diode D7 connected to the DC bus. road.

In other embodiments, the following technical solutions are adopted:

A control method of a multi-port hybrid DC circuit breaker suitable for a DC distribution network. When the i-th outlet wire connected to the multi-port hybrid DC circuit breaker fails or the i-th outlet wire needs to be cut off normally, the multi-port hybrid DC circuit breaker is controlled. The action process of the DC circuit breaker is as follows:

(1) Control the unlocking of each IGBT sub-module of the transfer branch and the locking of the load transfer switch of the i-th main branch unit. The fault current flowing through the isolation switch and fast mechanical switch of the main branch unit is reduced, and the fault current is replaced by the diode. flow to the transfer branch;

(2) When the current flowing through the fast mechanical switch of the main branch unit is close to zero, the fast mechanical switch is turned off;

(3) Each IGBT sub-module in the transfer branch is blocked, and the fault current charges the capacitor of each IGBT sub-module. When the capacitor voltage reaches the starting voltage of the energy-consuming branch MOV, the energy-consuming branch is turned on and begins to discharge energy. , after the fault current drops to zero, disconnect the isolating switch of the i-th main branch unit to achieve complete isolation of the i-th outgoing line.

As a further technical solution, in the step (2), if the opening action of the fast mechanical switch of the i-th main branch unit fails, the load transfer switch of the main branch unit is unlocked again, and the remaining main branch units are blocked. At this time, the fault current flowing through the remaining main branch units is reduced, and the fault current is commutated to the transfer branch through the diode;

When the current flowing through the fast mechanical switches of the remaining main branch units is close to zero, the fast mechanical switches are opened.

As a further technical solution, when the multi-port hybrid DC circuit breaker needs to remove the bus fault, the action process of the multi-port hybrid DC circuit breaker is as follows:

Unlock each IGBT sub-module of the transfer branch, block the load transfer switch of the main branch unit on all outgoing lines, the fault current flowing through the fast mechanical switch of each main branch unit gradually decreases, and the fault current is commutated to the transfer branch through the diode ;

When the fault current flowing through the fast mechanical switch of each main branch unit is close to zero, the fast mechanical switch of each main branch unit is opened;

Each IGBT sub-module of the transfer branch is blocked, and the fault current is transferred to the energy-consuming branch. After the energy in the fault current is discharged, the multi-port hybrid DC circuit breaker realizes the clearing of the fault current.

In other embodiments, the following technical solutions are adopted:

A controller for a multi-port hybrid DC circuit breaker suitable for a DC distribution network, comprising a server, the server comprising a memory, a processor and a computer program stored on the memory and running on the processor, the processing When the controller executes the program, the above-mentioned control method of the multi-port hybrid DC circuit breaker suitable for the DC distribution network is realized.

In other embodiments, the following technical solutions are adopted:

A computer-readable storage medium on which a computer program is stored, and when the program is executed by a processor, executes the above-mentioned control method of a multi-port hybrid DC circuit breaker suitable for a DC distribution network.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The multi-port hybrid DC circuit breaker greatly reduces the primary equipment investment of the DC circuit breaker by sharing the transfer branch and the energy-consuming branch of each line. It is an economical and feasible solution for the limited investment in the DC distribution network. plan;

(2) The multi-port hybrid DC circuit breaker can realize the opening and closing of normal lines, isolate faulty lines or busbars, and has the ability to protect against failure of fast mechanical switches;

(3) The multi-port hybrid DC circuit breaker has the characteristics of simple control, high modularity and easy expansion.

Description of drawings

The accompanying drawings that form a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute improper limitations on the present application.

FIG. 1 is a schematic topology diagram of a two-port hybrid DC circuit breaker in Embodiment 1;

Fig. 2 (a) is the current waveform of each branch of the hybrid DC circuit breaker in the first embodiment;

Figure 2(b) is the voltage waveform at both ends of the hybrid DC circuit breaker in the first embodiment;

3 is a topology of a multi-port hybrid DC circuit breaker in Embodiment 1;

Fig. 4 is the fault current flow path in the second embodiment;

Fig. 5 is the fault current flow path in the second embodiment;

Fig. 6 is the fault current flow path in the second embodiment;

7 is a simulation model of the DC distribution network in the third embodiment;

Fig. 8 is each line current and DC bus voltage waveforms in the third embodiment;

9 is the current waveform of each branch in MP-HCB ₁ in the third embodiment;

Figures 10(a)-(b) are the line current and bus voltage waveforms in the third embodiment;

11 is the current waveform of each branch in MP-HCB ₁ in the third embodiment;

Figure 12(a)-(b) are the line current and bus voltage waveforms in the third embodiment;

13 is the current waveform of each branch in MP-HCB ₁ in the third embodiment;

14(a)-(b) are the line current and bus voltage waveforms in the third embodiment.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

Example 1

The two-port hybrid DC circuit breaker (TP-HCB) combines the advantages of mechanical DC circuit breakers and all-solid-state DC circuit breakers, and uses the principle of forced commutation to realize the breaking of fault current. The structure is shown in Figure 1, including the main branch, the transfer branch and the energy consumption branch.

The main branch of the two-port hybrid DC circuit breaker is composed of a fast-mechanical switch (FMS) and a load communication switch (LCS), which are responsible for the conduction of the normal load current and the fault current during the operation of the DC circuit breaker. The transfer branch is composed of a large number of IGBT submodules (submodules, SM) in series, which are used to carry fault current for a short time and establish a transient breaking voltage, which is the part with the largest equipment investment in the hybrid DC circuit breaker; the energy consumption branch is composed of metal Oxide resistors (metal oxide varistor, MOV) are formed in series and parallel to limit the transient breaking voltage and dissipate the energy stored in the fault current. The action sequence of the two-port hybrid DC circuit breaker is shown in Figure 2, where i _main , i _transfer and i _MOV represent the currents in the main branch, the transfer branch and the energy-consuming branch, respectively.

As shown in Figure 2, the line fault occurs at time t ₀ , and the fault current begins to rise; at time t ₁ , the DC circuit breaker receives the trip command, unlocks each IGBT sub-module in the transfer branch and blocks the load transfer switch in the main branch, and the fault current The commutation from the main branch to the transfer branch begins, and the first commutation process begins; the first commutation process ends at time _t2 , the fault current in the main branch is close to zero, and the fast mechanical switch starts to open; _t3 At time, the fast mechanical switch opening of the main branch is completed, each IGBT sub-module of the transfer branch is blocked, the fault current begins to charge the capacitors of each IGBT sub-module, and the second commutation process begins _; at time t4, the capacitor voltage of the IGBT sub-module of the transfer branch When the starting voltage of the energy-consuming branch MOV is reached, the energy-consuming branch is turned on and begins to discharge energy, and the second commutation process ends _; at t5 time, the energy discharge in the fault current is completed, the fault current is cleared, and the DC circuit is disconnected. The voltage across the device is maintained at the system voltage.

In one or more embodiments, a multi-port hybrid DC circuit breaker suitable for a DC distribution network is disclosed. In view of the characteristic that there are multiple outgoing lines on the DC bus of the DC distribution network, the forced commutation characteristics of the branches are utilized. , a new type of multi-port hybrid DC circuit breaker is proposed. Its topology is shown in Figure 3, including: a main branch, a transfer branch and an energy-consuming branch connected in parallel; the main branch includes: a number of parallel connections Each main branch unit is connected between the DC bus and its outlet; each main branch unit includes: an isolation switch, a fast mechanical switch and a load transfer switch connected in series in sequence; the isolation switch and the DC bus Outgoing line connection, the load transfer switch is connected with the DC bus; the DC bus is connected with the transfer branch through the diode D7;

Referring to FIG. 3, between the isolation switch and the fast mechanical switch of each main branch unit, after connecting the diodes to the two ends, the connecting lines are respectively connected to the two ends of the transfer branch, and the DC bus is connected to the transfer branch through the diode D7. road connection. When the system is in normal operation, the load current flows through each main branch, and each diode has no current flow. When the line or bus fails, after the load transfer switch of the main branch is locked, the fault current will be commutated to the transfer branch through the diodes D1-D6 connected to each main branch unit and the diode D7 connected to the DC bus. road.

In Figure 3, FMS _i is a fast mechanical switch, LCS _i is a load transfer switch, _{Di is a diode series branch, DS i is} an isolation switch, and the multi-port hybrid DC circuit breaker transfers each IGBT submodule of the branch during normal operation All are blocked, and the load current all flows through the fast mechanical switch FMS _i and the load transfer switch LCS _i on each line.

Embodiment 2

In one or more embodiments, a control method of a multi-port hybrid DC circuit breaker suitable for a DC distribution network is disclosed, including:

Line fault circuit breaker control strategy. When a line connected to the multi-port hybrid DC circuit breaker fails or needs to be cut off normally (take Line 1 in Figure 3 as an example), the action process of the multi-port hybrid DC circuit breaker is as follows:

1) Control the unlocking of each IGBT sub-module of the transfer branch and the blocking of LCS _1. At this time, the fault current flowing through FMS ₁ and LCS ₁ begins to decrease, and the fault current is commutated to the diode branches D ₂ to D ₄ and the transfer branch;

2) When the current flowing through FMS ₁ is close to zero, FMS ₁ starts to open;

3) After a certain period of time (usually 2ms), the FMS ₁ opening is completed. At this time, the flow path of the fault current is indicated by the dotted line in Figure 4, and the light-colored portion indicates the area with no current flow;

4) The IGBT sub-modules in the transfer branch are blocked, the fault current is commutated to the energy-consuming branch, and the energy-consuming branch is turned on to discharge energy. After the fault current drops to zero, the isolation on the faulty line can be disconnected. The switch DS ₁ achieves complete isolation of the faulty line.

Circuit breaker failure protection control strategy. When the line Line 1 fails, after receiving the trip command, the DC circuit breaker first performs the isolation operation process of the normal fault line, and sequentially controls the load transfer switch LCS ₁ to block and the fast mechanical switch FMS ₁ to open. When the FMS ₁ starts to open, after a short time (set to 0.5ms in the present invention), the control system detects that the FMS ₁ fails to act, and judges that the FMS ₁ is out of order. At this time, the fast mechanical switch failure protection starts to act, and the action process is as follows. :

1) Re-unlock LCS ₁ , and then lock LCS ₂ and LCS ₃ . At this time, the fault current flowing through DS ₂ -FMS ₂ -LCS ₂ and DS ₃ -FMS ₃ -LCS ₃ begins to decrease, and the fault current begins to commutate to in the diode branches D ₂ to D ₄ , D ₇ and the transfer branch;

2) When the fault current flowing through FMS ₂ and FMS ₃ is close to zero, FMS ₂ and FMS ₃ start to open;

3) After 2ms, the opening of FMS ₂ and FMS ₃ is completed. At this time, the flow path of the fault current is shown in the dotted line in Figure 5. After that, the fault current can be commutated to the energy-consuming branch by blocking each IGBT sub-module of the transfer branch, and the fault current can be cleared through the energy-consuming branch;

4) It can be seen from Figure 5 that when the fast mechanical switch fails to protect, because the fast mechanical switches FMS ₂ and FMS ₃ are in the open state, the power exchange between Line 2 and Line 3 is interrupted. At this time, disconnect the isolating switch DS ₁ on the faulty line Line 1, and after completely isolating the fault line Line 1, close FMS ₂ and FMS ₃ in turn, unlock LCS ₂ and LCS ₃ , and restore the normal operation of Line 2 and Line 3.

Busbar fault circuit breaker control strategy. When the multi-port hybrid DC circuit breaker needs to remove the bus fault, the action process of the multi-port hybrid DC circuit breaker is as follows:

1) Unlock each IGBT sub-module of the transfer branch, block the load transfer switches LCS ₁ to LCS ₃ on all lines, and then the fault current flowing through FMS ₁ to FMS ₃ gradually decreases, and the fault current is commutated to the diode branch D ₁ ~ _D3 , D7 and transfer branch;

2) When the fault current flowing through FMS ₁ ~ FMS ₃ is close to zero, FMS ₁ ~ FMS ₃ start to open, and after about 2ms, the fast mechanical switch is completed. At this time, the flow path of the fault current is shown in the dotted line area in Figure 6;

3) Each IGBT sub-module of the transfer branch is blocked, and the fault current is transferred to the energy-consuming branch. After the energy in the fault current is discharged, the multi-port hybrid DC circuit breaker realizes the clearing of the fault current.

Embodiment 3

Using PSCAD/EMTDC software to build a 4-node flexible DC distribution network simulation model based on modular multi-level converters, the feasibility of the proposed multi-port hybrid DC circuit breaker is simulated and verified:

1) Build the model

In order to verify the feasibility of the multi-port hybrid DC circuit breaker proposed in the present invention, a 4-node ±10kV DC distribution network model based on modular multi-level converters was built on the PSCAD/EMTDC simulation platform, as shown in Figure 7 . Among them, each converter station of the DC distribution network is connected to the AC grid with a voltage level of 110kV, and the MMC converter station is a symmetrical single-pole structure, and the neutral point of the converter transformer is grounded through high resistance. A 10mH current-limiting reactor is connected in series with each pole at the outlet of the converter station to restrain the rising speed of the fault current and buy time for the protection and the action of the DC circuit breaker. The MMC1 converter station adopts the constant DC voltage control mode, and the MMC2 and MMC3 converter stations adopt the constant active power control mode. The main parameters are shown in Table 1. The DC/DC converter is a dual-active full-bridge structure, using a single-phase-shift control method, the rated voltage is 20kV/1.5kV, and the rated power of the DC load is 4MW. The DC line adopts a distributed frequency-dependent model, and the length of each line is shown in Figure 7. MP-HCB _i represents a multi-port hybrid DC circuit breaker, which is respectively arranged at each DC busbar and is responsible for removing the corresponding faulty components when the MMC converter station, DC line or busbar fails to ensure the safe and stable operation of the system. The parameters are shown in Table 2.

Table 1 Main parameters of DC distribution network converter station

Table 2 Main parameters of multi-port hybrid DC circuit breaker

2) Economic Analysis

The following is an economical comparison of the schemes of centralized configuration of multi-port hybrid DC circuit breakers on multiple lines in the DC distribution network and two-port hybrid DC circuit breakers distributed in each line. In order to compare the results simply and clearly, take Line 1 to Line 3 in Figure 7 as an example for analysis. Since the cost of the DC circuit breaker is greatly affected by the maximum transient voltage and the maximum fault current that the transfer branch needs to bear, each fault point is simulated on the PSCAD/EMTDC simulation platform, and it is concluded that after a fault current breaking cycle ( Including the fault detection time and the circuit breaker action time, the fault detection time in the present invention is 1ms, and the circuit breaker action time is 2.5ms) The maximum fault current that may appear on each line is shown in Table 3.

Table 3 Maximum fault current of each line

Table 4 shows the number of load transfer switches and fast mechanical switches required for the two different schemes, as well as the maximum transient breaking voltage and maximum fault current that the transfer branch withstands. Through comparison, it can be found that the two schemes require the same number of fast mechanical switches and load transfer switches, but the maximum transient voltage and fault current that the transfer branch of the multi-port hybrid DC circuit breaker needs to withstand is much smaller than the respective lines of each line. When configuring a two-port hybrid DC circuit breaker, three groups of transfer branches and energy-consuming branches are required for decentralized configuration, while one group of transfer branches and energy-consuming branches is shared for centralized configuration, which greatly reduces equipment costs.

Table 4 Comparison of device requirements for different schemes

3) Simulation of normal line opening

Take Line 1 in Figure 7 as an example to simulate normal line opening. At 1 second, the multi-port hybrid DC circuit breaker starts to perform the opening operation. The operation process is as described above. During the opening process, the current and DC bus voltage of each line connected to MP-HCB ₁ are shown in Figure 8(a)-(b ) shown. For the sake of clarity, the current waveforms in the following figures are positive current waveforms unless otherwise specified.

It can be seen from Figure 8(a)-(b) that after the DC circuit breaker operates for 1 second, the current of Line 1 drops to zero rapidly, the non-faulty lines Line 2 and Line 3 maintain normal current flow, and the normal line opening process is System voltage stabilization has little effect.

4) Line fault simulation

Since the DC distribution network is an ungrounded system, the fault current is very small when the single-pole grounding fault occurs, and the fault transient current quickly decays to zero. The isolated single-pole grounding fault line is the same as the normal line opening transient process. Repeat.

When a short-circuit fault occurs in the system, the fault will generate a very large fault current in a very short time. Assuming that the fault occurs at 1 second, the DC circuit breaker starts to operate after receiving the trip command at 1.001 seconds. The detailed operation process is as described above, and the simulation waveforms are shown in Figure 9 and Figure 10(a)-(b). Fig. 9 is the current waveform of each branch in MP-HCB ₁ , and Fig. 10(a)-(b) is the line current and DC bus voltage waveform of Line 1 to Line 3.

It can be seen from Figure 9 and Figure 10(a)-(b) that the DC circuit breaker removes the faulty line within 3 milliseconds, and the process of removing the faulty line does not affect the normal operation of the sound line, and the current of the non-faulty line passes through. After a brief fluctuation, it remained stable for 1.3 seconds, and the voltage of the DC distribution network system quickly returned to stability after a brief fluctuation.

5) Simulation of switch failure protection

When a fast mechanical switch of the multi-port hybrid DC circuit breaker fails, the fast mechanical switch failure protection action is performed, and the fast mechanical switch on each sound circuit replaces the failed switch to complete the fault current transfer function. Set 1 second when Line 1 has an inter-pole short-circuit fault, and at 1.001 seconds, the DC circuit breaker receives the trip command and starts to trip. Block the load transfer switch on Line 1 of the faulty line in turn, and start the fast mechanical switch to open. After 0.5 milliseconds, the control system detects that the fast mechanical switch does not act, and determines that the fast mechanical switch fails. At this time, the fast mechanical switch fails to protect the action. The specific action process is as described above. The transient process of the system during the operation of the DC circuit breaker is shown in Figure 11 and Figure 12(a)-(b).

It can be seen from Figure 11 and Figure 12(a)-(b) that the failure of the mechanical switch of the circuit breaker will lead to a slight increase in the fault clearing time. When the faulty line is completely isolated, the non-faulty line is put into operation again and remains stable after a transient process of about 0.25 seconds, and the system voltage returns to a normal state about 0.1 seconds after the DC circuit breaker operates.

6) DC bus fault simulation

When set for 1 second, the DC bus in MP-HCB ₁ has an interpole short-circuit fault. At this time, the fault current rises rapidly, and all lines inject fault current into the DC bus. At this time, it is the most severe work for the multi-port hybrid DC circuit breaker. state. The 1.001-second DC circuit breaker starts to operate after receiving the trip command. The detailed operation process is as described above. The current and voltage waveforms in the transient process of the system are shown in Figure 13 and Figure 14(a)-(b).

It can be seen from Figure 14(a)-(b) that the system voltage of the DC distribution network has _a tendency to deviate from the rated value. However, the MMC1 converter station is a constant voltage converter station, so after the DC bus is cut off, the power emitted in the DC distribution network is greater than the power consumed by the load, causing the system voltage to rise. At this time, in order to maintain the system voltage stability, the control mode of converter station MMC2 or MMC3 should be adjusted from constant active power control to constant voltage control.

The rapid development of DC distribution network urgently requires DC circuit breakers with good performance in terms of reliability, quickness and economy. In order to solve this problem, the present invention proposes a multi-port hybrid DC circuit breaker topology with the capability of opening and closing normal lines, isolating faulty lines or busbars, and fast mechanical switch failure protection. This topology has the advantages of simple control, high modularity and easy expansion. Compared with the scheme of configuring two-port hybrid DC circuit breakers separately for each line, the primary equipment investment is greatly reduced, especially in the case of limited investment in the DC distribution network. an economical and feasible solution.

Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the scope of protection of the present invention. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art do not need to pay creative work. Various modifications or deformations that can be made are still within the protection scope of the present invention.

Claims (7)

1. A multi-port hybrid DC circuit breaker suitable for a DC distribution network, comprising: a main branch, a transfer branch and an energy-consuming branch connected in parallel; Main branch unit, each main branch unit is connected between the DC bus and its outlet; each main branch unit includes: an isolation switch, a fast mechanical switch and a load transfer switch connected in series in sequence; the isolation switch and the DC bus The load transfer switch is connected to the DC bus; each main branch unit is connected to the transfer branch through a diode, and the DC bus is connected to the transfer branch through a diode. 2. A control method for a multi-port hybrid DC circuit breaker applicable to a DC distribution network, characterized in that, when the i-th outlet wire connected to the multi-port hybrid DC circuit breaker fails or needs to be normally cut off the i-th outlet wire , the action process of the multi-port hybrid DC circuit breaker is: (1) Control the unlocking of each IGBT sub-module of the transfer branch and the locking of the load transfer switch of the i-th main branch unit. The fault current flowing through the isolation switch and fast mechanical switch of the main branch unit is reduced, and the fault current is replaced by the diode. flow to the transfer branch; (2) When the current flowing through the fast mechanical switch of the main branch unit is close to zero, the fast mechanical switch is turned off; (3) Each IGBT sub-module in the transfer branch is blocked, and the fault current charges the capacitor of each IGBT sub-module. When the capacitor voltage reaches the starting voltage of the energy-consuming branch MOV, the energy-consuming branch is turned on and begins to discharge energy. , after the fault current drops to zero, disconnect the isolating switch of the i-th main branch unit to achieve complete isolation of the i-th outgoing line. 3. The control method of the multi-port hybrid DC circuit breaker applicable to the DC distribution network as claimed in claim 2, wherein in the step (2), if the fast mechanical If the switch opening fails, the load transfer switch of the main branch unit will be unlocked again, and the load transfer switches of the other main branch units will be blocked. At this time, the fault current flowing through the remaining main branch units will decrease, and the fault current will pass through the diode. commutate to the transfer branch; When the current flowing through the fast mechanical switches of the remaining main branch units is close to zero, the fast mechanical switches are opened. 4. The control method of a multi-port hybrid DC circuit breaker applicable to a DC distribution network as claimed in claim 3, characterized in that, after the ith outgoing line is isolated, the fast mechanical switches of the remaining main branch units are closed successively, Unlock the load transfer switches of the remaining main branch units and restore the normal operation of the remaining outlet lines. 5. The control method of a multi-port hybrid DC circuit breaker applicable to a DC distribution network according to claim 2, wherein when the multi-port hybrid DC circuit breaker needs to remove a bus fault, the multi-port hybrid DC circuit breaker The action process of the device is: Unlock each IGBT sub-module of the transfer branch, block the load transfer switch of the main branch unit on all outgoing lines, the fault current flowing through the fast mechanical switch of each main branch unit gradually decreases, and the fault current is commutated to the transfer branch through the diode ; When the fault current flowing through the fast mechanical switch of each main branch unit is close to zero, the fast mechanical switch of each main branch unit is opened; Each IGBT sub-module of the transfer branch is blocked, and the fault current is transferred to the energy-consuming branch. After the energy in the fault current is discharged, the multi-port hybrid DC circuit breaker realizes the clearing of the fault current. 6. A controller for a multi-port hybrid DC circuit breaker suitable for a DC distribution network, characterized in that it comprises a server, and the server includes a memory, a processor, and a controller that is stored in the memory and can run on the processor. A computer program, when the processor executes the program, the control method for a multi-port hybrid DC circuit breaker applicable to a DC distribution network according to any one of claims 2-5 is implemented. 7. A computer-readable storage medium on which a computer program is stored, characterized in that, when the program is executed by a processor, the multi-port hybrid system suitable for a DC distribution network according to any one of claims 2-5 is executed. The control method of the type DC circuit breaker.