Low-voltage direct-current power distribution network fault removal method, device and system based on all-solid-state circuit breaker

Abstract

The invention relates to a low-voltage direct-current power distribution network fault removal method, device and system based on an all-solid-state circuit breaker, and belongs to the field of direct-current system power distribution networks. According to the method, firstly, all-solid-state circuit breakers are used for replacing networking converters and circuit breakers on all local lines of the low-voltage direct-current power distribution network; secondly, when fault information of the low-voltage direct-current power distribution network is detected, firstly disconnecting an all-solid-state circuit breaker of the networking converter to enable the low-voltage direct-current power distribution network to be in an off-grid operation state, and then adjusting the power output size of an energy storage system and / or a power adjusting device to enable the low-voltage direct-current power distribution network to be in an off-grid operation state; and finally, the all-solid-state circuit breaker of the fault line is disconnected, so that the removal of the fault line is realized. The method is used for solving the problems of high investment cost, high failure rate, complex communication maintenance and the like caused by the fact that low-voltage bus protection and line protection measures in the prior art need to use optical fibers.

Description

Technical Field

[0001] The invention relates to a method, a device and a system for removing faults in a low-voltage direct current distribution network based on a full-solid-state circuit breaker, and belongs to the field of direct current system power distribution networks. Background Art

[0002] With the rapid development of power electronics technology and new energy power generation technology, a large number of distributed new energy sources have been connected to the distribution network, and the traditional distribution network structure and operation mode have been impacted. The traditional AC distribution network has been unable to meet the growing user needs, restricting the upgrading of energy structure and economic and social development. Compared with the AC distribution network, the DC system has the characteristics of low line cost, low line loss, high transmission efficiency, and excellent power supply quality, and has better reliability and economy in solving the problem of renewable energy consumption.

[0003] During a DC grid fault, there are significant characteristics of large short-circuit current and fast rise. Since DC short-circuit current has no difficulty in crossing the zero point to extinguish the arc, it will reach the current peak in a few milliseconds. If the DC circuit breaker cannot quickly remove the fault, the AC grid may have a three-phase short circuit and cause an overcurrent fault in the converter, which will expand the scope of the accident and cause a large-scale power outage in the low-voltage DC grid.

[0004] At present, in low-voltage DC power grids, low-voltage busbar protection and line protection are usually adopted to ensure that the system can act quickly when a typical fault occurs. This measure can ensure the safe and stable operation of the low-voltage DC power grid to a certain extent. However, since these two types of protection use optical fiber architecture, this architecture can achieve rapid fault removal through efficient optical fiber transmission, but it requires the laying of a large number of optical fibers, so the cost is expensive, resulting in large investments, high failure rates, and complex communication maintenance. It does not meet the conditions for large-scale promotion and application. Summary of the invention

[0005] The purpose of the present invention is to provide a low-voltage DC distribution network fault removal method, device and system based on an all-solid-state circuit breaker, so as to solve the problems of high investment cost, high failure rate, complex communication maintenance, etc. caused by the need to use optical fiber for low-voltage bus protection and line protection measures taken in the prior art to ensure the safe operation of the low-voltage DC power grid.

[0006] To achieve the above object, the solution of the present invention includes: A method for removing faults in a low-voltage DC distribution network based on a fully solid-state circuit breaker of the present invention comprises: When a fault is detected in the low-voltage DC distribution network, the circuit breaker in the networking converter is disconnected to put the low-voltage DC distribution network in an off-grid operation state, and the power output of the energy storage system and / or the power regulation device in the low-voltage DC distribution network is adjusted to meet the action requirements of the circuit breaker on the line where the fault is located in the low-voltage DC distribution network. After the adjustment, the circuit breaker on the faulty line is controlled to be disconnected to achieve the removal of the faulty line; the circuit breakers in the networking converter and the circuit breakers on the local lines of the low-voltage DC distribution network are all fully solid-state circuit breakers.

[0007] Furthermore, adjusting the power output of the energy storage system and / or the power regulation device in the low-voltage DC distribution network includes: first adjusting the power absorbed by the energy storage system and / or the power regulation device in the low-voltage DC distribution network to be the power emitted by the networked converter to the power grid, and then adjusting the power absorbed by the energy storage system and / or the power regulation device in the low-voltage DC distribution network to be the power on the line where the fault is located.

[0008] Furthermore, the fault is a low voltage fault or an over current fault.

[0009] Furthermore, the method also includes reclosing the circuit breaker of the interconnected converter after opening the circuit breaker of the faulty line.

[0010] Furthermore, after the circuit breaker of the interconnected converter is reclosed, the power output of the energy storage system and / or the power conditioning device in the low-voltage DC distribution network is adjusted again to restore the remaining load in the low-voltage DC distribution network to a normal working state.

[0011] The present invention also provides a low-voltage DC distribution network fault removal device based on a fully solid-state circuit breaker, comprising a fault detection unit, an intelligent analysis unit and an execution unit, wherein the fault detection unit is used to detect whether there is a fault in the low-voltage DC distribution network; the intelligent analysis unit is used to determine the power output of an energy storage system and / or a power regulation device in the low-voltage DC distribution network according to the power emitted by the networked converter to the power grid and the power of the line where the fault is located in the low-voltage DC distribution network, so as to balance the power of the distribution network after the circuit breaker of the faulty line is removed; the execution unit is used to disconnect the circuit breaker in the networked converter when the fault detection unit detects that there is a fault in the low-voltage DC distribution network, and control the circuit breaker on the faulty line to disconnect after the energy storage system and / or the power regulation device are adjusted according to the determined power output, so as to realize the removal of the faulty line; the circuit breaker in the networked converter and the circuit breakers on each local line of the low-voltage DC distribution network are all fully solid-state circuit breakers.

[0012] Furthermore, the faults detected by the fault detection unit include low voltage faults and over current faults.

[0013] Furthermore, it also includes a recovery unit, which is used to send an instruction to the execution unit to reclose the circuit breaker of the networked converter after the circuit breaker of the faulty line is disconnected.

[0014] Furthermore, the recovery unit also readjusts the power output of the energy storage system and / or the power regulation device to restore the distribution network to the stable operation before the adjustment.

[0015] The present invention also provides a low-voltage DC distribution network fault removal system based on an all-solid-state circuit breaker, comprising a processor, the processor being used to execute a computer program to implement the steps of the above-mentioned low-voltage DC distribution network fault removal method based on an all-solid-state circuit breaker.

[0016] The beneficial effects of the present invention are as follows: as an improved invention, the present invention first uses a fully solid-state circuit breaker to replace the networked converter and the circuit breakers on each local line of the low-voltage DC distribution network, and uses the advantage of the short response time of the fully solid-state circuit breaker to speed up the fault removal; secondly, when the fault information of the low-voltage DC distribution network is detected, the fully solid-state circuit breaker of the networked converter is first disconnected to put the low-voltage DC distribution network in an off-grid operation state, and then the power output of the energy storage system and / or the power regulation device is adjusted to meet the action requirements of the circuit breaker on the line where the fault is located in the low-voltage DC distribution network, and finally the fully solid-state circuit breaker of the fault line is disconnected to achieve the removal of the fault line, ensuring that the fault is quickly removed while avoiding the impact on other loads in the DC distribution network, and further improving the safety of the low-voltage DC distribution network. The existing low-voltage bus protection and line protection measures need to use optical fibers, which cause high investment costs, high failure rates, and complex communication maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a topological diagram of low voltage DC distribution network based on all solid state circuit breakers; Figure 2 It is a flow chart of a method for rapid fault removal of a low voltage DC distribution network based on a fully solid-state circuit breaker; Figure 3 It is a schematic diagram of a low voltage DC distribution network fault rapid removal device based on a fully solid-state circuit breaker; Figure 4 It is a schematic diagram of the operation of a low voltage DC distribution network fault state system based on a fully solid-state circuit breaker; Figure 5 It is a schematic diagram of the operation of a low-voltage DC distribution network fault removal system based on a fully solid-state circuit breaker. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail in a clear and complete manner in conjunction with the accompanying drawings and embodiments.

[0019] The concept of the present invention is that, firstly, the networked converter and the circuit breakers on each local line of the low-voltage DC distribution network all adopt all-solid-state circuit breakers, which control the on-off of the circuit through semiconductor devices, can interrupt the fault current without moving parts, have the advantages of short response time, limit the passing energy, etc., can speed up the on-off of the circuit, and help to quickly cut off the fault; secondly, when the fault information of the low-voltage DC distribution network is detected, the all-solid-state circuit breaker of the networked converter is first disconnected, so that the low-voltage DC distribution network is in an off-grid operation state, and then the power output of the energy storage system and / or the power regulation device is adjusted to meet the action requirements of the circuit breaker on the line where the fault is located in the low-voltage DC distribution network, and finally the all-solid-state circuit breaker of the fault line is disconnected to achieve the removal of the fault line, so that it can ensure that the fault is quickly removed while avoiding the impact on other loads in the DC distribution network, and further improve the safety of the low-voltage DC distribution network.

[0020] Method Example: The low voltage DC distribution network generally includes a power generation unit connected to a DC bus, an energy storage system, a power conditioning device and a load unit. The DC bus is connected to the AC grid through an AC / DC converter and a fully solid-state circuit breaker B0. For this embodiment, Figure 1 As shown, the power generation unit is distributed photovoltaic, and the power generation unit is connected to the DC bus through a DC / DC converter and an all-solid-state circuit breaker B1; the energy storage system is connected to the DC bus through a DC / DC converter and an all-solid-state circuit breaker B2; the load unit includes a charging pile, air conditioning, lighting and other loads, wherein the charging pile is connected to the DC bus through a DC / DC converter and an all-solid-state circuit breaker B3; the air conditioning, lighting and other loads are connected to the DC bus through an all-solid-state circuit breaker B5 and a DC / DC controller; the power regulating device adopts a power four-quadrant regulating device, which is connected to the DC bus through a DC / DC converter and an all-solid-state circuit breaker B4. As other implementation methods, the load can also be set according to actual conditions. The system has the ability to operate on / off the grid, wherein the capacity of the energy storage system and the power four-quadrant regulating device must meet the operation requirements of the low-voltage DC distribution network and be selected as 3 times the total load.

[0021] like Figure 2 The figure shows the implementation process of the method for fast fault removal in low voltage DC distribution network. Specifically, Figure 4 Taking the fault state system operation diagram shown in the figure as an example, when a fault occurs in the line where the charging pile is located, the steps for quickly eliminating the fault are as follows.

[0022] (1) Fault detection The present invention determines whether there is a fault based on the detected voltage and current by the AC / DC converter, where the voltage and current include the voltage and current on the DC bus and the voltage and current on each line connected to the DC bus. The faults that can be detected by the present invention mainly include low voltage faults and overcurrent faults, wherein the low voltage fault refers to the voltage value on the line being lower than the corresponding voltage threshold (the voltage threshold of each line can be specifically set according to the actual situation), and the overcurrent fault refers to the current value on the line being higher than the corresponding current threshold (the current threshold of each line can be specifically set according to the actual situation); further confirm the line where the fault is located, and the faulty line in this embodiment is the branch where the charging pile is located.

[0023] (2) Fault removal After a fault is detected, the all-solid-state circuit breaker in the networked converter is disconnected first, and then the power output of the energy storage system and / or the power regulation device in the low-voltage DC distribution network is adjusted to meet the action requirements of the circuit breaker on the line where the fault is located in the low-voltage DC distribution network. After the adjustment, the circuit breaker on the faulty line is controlled to be disconnected to achieve the removal of the faulty line.

[0024] For this embodiment, Figure 4 As shown, the all-solid-state circuit breaker B0 of the AC / DC networking converter is disconnected, so that the low-voltage DC distribution network is in an off-grid operation state. Since the fault in this embodiment occurs on the line where the charging pile is located, the all-solid-state circuit breaker B3 of the line where the charging pile is located should be disconnected. However, considering that direct disconnection may cause other loads to overload, before disconnecting the all-solid-state circuit breaker B3, power adjustment is performed inside the low-voltage DC distribution network to avoid overload problems of other loads. This embodiment can be achieved by adjusting the power output of the energy storage system and / or the power four-quadrant regulation device in the low-voltage DC distribution network. During the specific adjustment, one of the energy storage system and the power four-quadrant regulation device can be selected for adjustment. When the adjustment amount of one of them does not meet the requirements, the two can be used for adjustment at the same time. Assuming that both need to be adjusted at the same time, the power sent by the AD / DC converter to the power grid is N, and the power on the line where the charging pile is located is M. After the fault, the all-solid-state circuit breaker B0 is first disconnected, and the absorbed power of the energy storage and power four-quadrant regulation devices is adjusted to N; after a period of time, the absorbed power of the energy storage system and the power four-quadrant regulation device is adjusted to be equal to the power M on the line where the charging pile is located. In this way, after the adjustment, the all-solid-state circuit breaker B3 can be disconnected, as shown in FIG. Figure 5 As shown, the faulty line of the charging pile can be quickly disconnected (although the power adjustment and disconnection of the circuit breaker are sequential, they are almost performed at the same time). By adjusting the absorbed power of the energy storage system and the power four-quadrant adjustment device, the disconnection of the line where the charging pile is located will not affect other loads, thereby ensuring that the low-voltage DC distribution network can operate stably off-grid.

[0025] Since only the line where the charging pile is located has a fault in this embodiment, if other lines also have faults, the faulty line can be processed in the same way until all faulty lines are removed.

[0026] (3) Line recovery After disconnecting the circuit breakers of all faulty lines, reclose the circuit breaker of the networking converter, and adjust the power output of the energy storage system and / or the power regulation device in the low-voltage DC distribution network again to restore other loads to normal working conditions. For this embodiment, the status feedback signal of the all-solid-state circuit breaker B3 is received. When it is confirmed that the faulty line of the charging pile has been removed, that is, the state of B3 is disconnected, reclose the all-solid-state circuit breaker B0 of the AC / DC networking converter to achieve grid connection of the low-voltage DC distribution network. Since the low-voltage DC distribution network is already in a grid-connected operation state, the power grid can be used to balance the power of the low-voltage DC distribution network. At this time, the power output of the energy storage system and / or the power four-quadrant regulation device in the low-voltage DC distribution network can be readjusted to restore the low-voltage distribution network to stable operation before the adjustment. Figure 5 The diagram shows the system operation after the fault is removed.

[0027] Device Example: like Figure 3 The figure shows a schematic diagram of a low-voltage DC distribution network fault rapid removal device based on a fully solid-state circuit breaker. The removal device includes a fault detection unit, an intelligent analysis unit, an execution unit, and a recovery unit. The specific functions of each module are as follows: a. Fault detection unit: Based on the voltage and current, it is used to identify the fault information of the low-voltage DC distribution network and determine whether the fault branch and the AC / DC converter are communicating with each other; b. Intelligent analysis unit: used to calculate and analyze the power output of the energy storage system and the power four-quadrant regulation device when the system is off-grid, so that the system fault current meets the action requirements of the all-solid-state DC circuit breaker and balances the load power in the distribution network, so that the disconnection of the fault branch will not affect other loads, ensuring that the low-voltage DC distribution network can operate stably off-grid; c. Execution unit: sends opening and closing signals to disconnect the all-solid-state circuit breaker of the AC / DC converter and to remove one or more faulty branches; d. Recovery unit: It is used to receive the switch status feedback signal of the all-solid-state circuit breaker of the faulty line. After confirming that the faulty line has been cleared, it closes the all-solid-state circuit breaker of the AC / DC converter and readjusts the power output of the energy storage and / or power four-quadrant regulation device to restore the low-voltage distribution network to stable operation before the adjustment.

[0028] The specific excision steps have been clearly introduced in the method embodiment and will not be repeated here.

[0029] System Example: The present invention discloses a low-voltage DC distribution network fault removal system based on an all-solid-state circuit breaker. The system includes a processor, and the processor is used to execute computer program instructions to implement a low-voltage DC distribution network fault removal method based on an all-solid-state circuit breaker introduced in a method embodiment. The method has been clearly introduced in the method embodiment and will not be repeated here.

Claims

1. A method for removing faults in a low voltage DC distribution network based on a fully solid-state circuit breaker, characterized in that: The method includes: When a fault is detected in the low-voltage DC distribution network, the circuit breaker in the networking converter is disconnected to put the low-voltage DC distribution network in an off-grid operation state, and the power output of the energy storage system and / or the power regulation device in the low-voltage DC distribution network is adjusted to meet the action requirements of the circuit breaker on the line where the fault is located in the low-voltage DC distribution network, and after the adjustment, the circuit breaker on the faulty line is controlled to be disconnected to achieve the removal of the faulty line; the circuit breaker in the networking converter and the circuit breakers on the local lines of the low-voltage DC distribution network are all fully solid-state circuit breakers.

2. The method for removing faults in a low voltage DC distribution network based on a fully solid-state circuit breaker according to claim 1, characterized in that: Adjusting the power output of the energy storage system and / or the power regulation device in the low-voltage DC distribution network includes: first adjusting the power absorbed by the energy storage system and / or the power regulation device in the low-voltage DC distribution network to the power emitted by the networked converter to the grid, and then adjusting the power absorbed by the energy storage system and / or the power regulation device in the low-voltage DC distribution network to the power on the line where the fault is located.

3. The method for removing faults in a low voltage DC distribution network based on a fully solid-state circuit breaker according to claim 1, characterized in that: The fault is a low voltage fault or an over current fault.

4. The method for removing faults in a low voltage DC distribution network based on a fully solid-state circuit breaker according to claim 1, characterized in that: The method further includes reclosing the circuit breaker of the interconnecting converter after opening the circuit breaker of the faulty line.

5. The method for removing faults in a low voltage DC distribution network based on a fully solid-state circuit breaker according to claim 4, characterized in that: After the circuit breaker of the interconnected converter is closed again, the power output of the energy storage system and / or the power conditioning device in the low-voltage DC distribution network is adjusted again to restore the remaining load in the low-voltage DC distribution network to a normal working state.

6. A low voltage DC distribution network fault removal device based on a fully solid-state circuit breaker, characterized in that: It comprises a fault detection unit, an intelligent analysis unit and an execution unit, wherein the fault detection unit is used to detect whether there is a fault in the low-voltage DC distribution network; the intelligent analysis unit is used to determine the power output of the energy storage system and / or the power regulation device in the low-voltage DC distribution network according to the power emitted by the networked converter to the power grid and the power of the line where the fault is located in the low-voltage DC distribution network, so as to balance the power of the distribution network after the circuit breaker of the faulty line is removed; the execution unit is used to disconnect the circuit breaker in the networked converter when the fault detection unit detects that there is a fault in the low-voltage DC distribution network, and control the circuit breaker on the faulty line to disconnect after the energy storage system and / or the power regulation device are adjusted according to the determined power output, so as to realize the removal of the faulty line; The circuit breakers in the networked converter and the circuit breakers on each local line of the low-voltage DC distribution network are all fully solid-state circuit breakers.

7. The low voltage DC distribution network fault removal device based on all-solid-state circuit breaker according to claim 6, characterized in that: The faults detected by the fault detection unit include low voltage faults and over current faults.

8. The low voltage DC distribution network fault removal device based on all-solid-state circuit breaker according to claim 6, characterized in that: It also includes a recovery unit, which is used to send an instruction to the execution unit to reclose the circuit breaker of the networked converter after the circuit breaker of the faulty line is disconnected.

9. The low voltage DC distribution network fault removal device based on all-solid-state circuit breaker according to claim 8, characterized in that: The recovery unit also readjusts the power output of the energy storage system and / or the power regulation device to restore the distribution network to stable operation before the adjustment.

10. A low voltage DC distribution network fault removal system based on a fully solid-state circuit breaker, comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of a method for quickly clearing a low-voltage DC distribution network fault based on a fully solid-state circuit breaker as described in any one of claims 1 to 5.

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