Active power distribution network rapid power restoration method based on intelligent switching-on self-healing strategy

Abstract

The invention discloses an active power distribution network rapid power recovery method based on an intelligent switching-on self-healing strategy, and the method comprises the steps: carrying out the non-voltage detection of a non-fault power-loss region after an active power distribution network breaks down, and switching on an interconnection switch to recover the power supply of the non-fault power-loss region if a non-voltage condition is satisfied; otherwise, performing synchronism detection, and closing the interconnection switch if a synchronism condition is met; if the switching-on time limit is exceeded and the non-voltage condition and the synchronization condition are still not met, judging whether the voltage change rate of the non-fault power-loss area is smaller than a set value or not; if the voltage change rate of the non-fault power-losing area is smaller than a set value, the interconnection switch is closed, otherwise, the small power supply branch of the non-fault power-losing area is cut in an interlinkage mode, and a non-voltage condition is created for the self-healing switch. Through an intelligent closing self-healing strategy combining non-voltage detection, synchronization detection and small power supply intertripping, self-healing closing is carried out under the condition that off-grid of the distributed power supply is avoided as far as possible, rapid power supply recovery of a non-fault power-loss area of the active power distribution network is realized, and the stability and reliability of a power distribution network system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of current protection for distribution networks, and in particular to a method for rapid power restoration of active distribution networks based on an intelligent closing self-healing strategy. Background Art

[0002] The power supply restoration technology of the distribution network can quickly restore the power supply to the non-fault area affected by the fault in the distribution network after a fault occurs in the distribution network. It has a significant effect on improving the power supply reliability of the distribution network. At the same time, it also helps to improve the system resilience of the distribution network and strengthen the emergency response capabilities of the distribution network in the event of faults and disasters. With the continuous research and development of smart distribution networks, self-healing has become one of the most important characteristics of smart distribution networks, among which the power supply restoration technology of the distribution network is a key technology required in smart distribution networks. Therefore, the power supply restoration technology of the distribution network is of great significance to the research and implementation of future smart distribution networks.

[0003] In the prior art, after the distribution network protection self-healing device isolates the fault, the interconnection switch is closed to restore the power supply to the non-fault power-off area. In order to avoid the impact on the system caused by asynchronous closing, it is usually necessary to create a voltage-free condition for the non-fault power-off area, including cutting off the small power supply in the area through the self-healing device, or cutting off the small power supply through anti-islanding protection, so that the non-fault power-off area can be closed and the power supply can be restored after the voltage-free condition is met. As more and more distributed power sources are continuously connected to the distribution network, the traditional distribution network has become a distribution network containing distributed power sources. In order to prevent the distributed power generation from operating in an isolated island, when a system fault occurs, the protection self-healing device will simultaneously cut off the distributed power generation in the non-fault power-off area while removing the fault. With the gradual increase in the penetration rate of distributed power generation, the existing technology may cause large-scale grid disconnection of distributed power generation, which has a greater impact on the non-fault power-off area of ​​the system. In addition, with the improvement of the requirements for the reliability of power supply of distribution networks, the distributed protection self-healing system of distribution networks is developing from pilot projects to popularization and application. When the non-fault power-off area caused by the isolation fault of the system resumes power supply after self-healing, the distributed power generation in the area needs to be reconnected to the grid and put into operation. The short-term off-grid operation of the distributed power generation may cause unnecessary impact on the system.

[0004] The proportion of distributed power sources will become higher and higher. When a distribution network fails, large-scale disconnection of distributed power sources should be avoided as much as possible, so as to improve the absorption capacity of distributed power sources and the stability of the system. Therefore, it is necessary to study the self-healing scheme under the grid-connected operation of distributed power sources, and avoid self-healing when the distributed power sources are off the grid as much as possible. This has two requirements for the self-healing function: 1) Due to the limited load capacity of distributed power sources, self-healing must be completed in a short time. At the same time, the closing time must consider the fault-crossing capability of the distributed power sources and cooperate with the protection on the distributed power source side to prevent the distributed power sources from being disconnected from the grid in advance; 2) Self-healing requires synchronous closing to prevent impact on the distributed power sources. When the synchronization conditions are not met for a certain period of time, the distributed power sources are directly connected to ensure the smooth execution of the subsequent self-healing logic. Summary of the invention

[0005] The present invention is mainly intended to solve the problem that as the penetration rate of distributed power sources gradually increases, the existing distribution network restoration technology may cause large-scale disconnection of distributed power sources. It provides an active distribution network rapid restoration method based on an intelligent closing self-healing strategy. Through an intelligent closing self-healing strategy that combines voltage detection, synchronization detection and small power supply linkage, self-healing is performed while avoiding the distributed power sources from being disconnected from the grid as much as possible, so as to achieve rapid power restoration in non-fault power-off areas of the active distribution network, thereby improving the distributed power supply absorption capacity and the stability and reliability of the distribution network system.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions.

[0007] A method for rapid power restoration of an active distribution network based on an intelligent closing self-healing strategy comprises the following steps: Step S1: monitor whether the active distribution network has a fault at every set time interval; Step S2: When a fault occurs in the active distribution network, the fault is removed and isolated, and the distributed power supply in the fault power-off area is removed at the same time; Step S3: Within the closing time limit, a voltage check is performed on the non-fault power-off area. If the voltage-free condition is met, the tie switch is closed to restore power supply to the non-fault power-off area; otherwise, a synchronization check is performed. If the synchronization condition is met, the tie switch is closed; Step S4: If the no-voltage condition and the synchronization condition are still not met after the closing time limit is exceeded, it is determined whether the voltage change rate of the non-fault power-off area is less than the set value; Step S5: If the voltage change rate of the non-fault power-off area is less than the set value, close the tie switch; otherwise, cut off the small power supply branch of the non-fault power-off area and return to step S3.

[0008] The present invention provides a method for rapid power restoration of an active distribution network based on an intelligent closing self-healing strategy. In view of whether a non-fault power-off area contains a small power source after a distribution network fault and the differences in the characteristics of the small power source, an intelligent closing self-healing strategy combining no-voltage detection, synchronization detection and joint cutting of small power sources is proposed. Self-healing is performed while avoiding the distributed power source from being disconnected from the grid as much as possible, so as to realize rapid power restoration of the non-fault power-off area of ​​the active distribution network. The specific process is: after a fault occurs in the distribution network system, the fault is quickly removed and isolated, and the distributed power source in the fault power-off area is removed at the same time; for the non-fault power-off area, when the connecting switch is closed, the protection self-healing device first checks for no voltage, and if the non-fault power-off area meets the no-voltage condition, the switch is quickly closed; if the no-voltage condition is not met, the synchronization is checked, and if the synchronization condition is met, the switch is closed; when the no-voltage detection and the synchronization detection are still not met within a period of time, it is judged whether the voltage change rate of the non-fault power-off area is less than the set value, and if Then the interconnection switch is closed forcefully, otherwise the strategy of cutting off small power sources is started to cut off the small power branches in the non-fault power-off area, and the interconnection switch is closed after creating a voltage-free condition for the self-healing switch. The present invention distinguishes the inertia of distributed power sources by the voltage change rate in the non-fault power-off area after a distribution network failure, avoids the impact of asynchronous closing on the system, and ensures the reliable and stable operation of the system; through the intelligent closing strategy combining adaptive closing and cutting off small power sources, the success rate of self-healing gates in the case of distributed power access is improved, and the rapidity and reliability of system power supply recovery are ensured; the continuous output capacity of distributed power sources in the case of system failure is improved, and the adverse effects caused by a large number of distributed power sources being disconnected from the grid are effectively avoided, and it has good application prospects.

[0009] Preferably, when the active distribution network fails, the distributed power grid connection point can detect the sudden change, and the specific process of step S1 includes the following steps: Step S11: collecting three-phase voltage and current of the voltage transformer and the current transformer at the distributed power grid connection point; Step S12: filtering and Fourier baseband extraction of the collected three-phase voltage and current to obtain sampling values ​​of the three-phase voltage and current; Step S13: Calculate the fault component values ​​of the three-phase voltage and current by detecting the sampling value of the cycle before the sudden change and the sampling value of the cycle after the sudden change; Step S14: Decoupling the fault component values ​​of the three-phase voltage and current into positive, negative and zero-sequence fault components of the current and voltage through phase mode transformation; Step S15: Calculate the equivalent backside impedance of the distributed power source equivalent to the Thevenin theorem using the positive sequence fault components of the current and voltage; Step S16: using the equivalent back impedance of the distributed power source to calculate in real time the setting values ​​of the adjacent protection points upstream and downstream of the distributed power source access point; Step S17: Compare the setting value of each protection point with the current value actually measured at the protection installation point. When the actual value is greater than the calculated setting value, it is determined that a fault has occurred.

[0010] Preferably, when a fault occurs in the active power distribution network, the entire power distribution network is divided into three parts, including a normal power supply area, a fault power loss area, and a non-fault power loss area downstream of the fault power loss area.

[0011] Preferably, a specific faulty component is determined by a fault location technology, and a protection device is used to isolate the faulty component within a certain area to obtain a fault power failure area of ​​the active distribution network.

[0012] Preferably, in a downstream area of ​​the fault power-off area, a non-fault power-off area of ​​the active power distribution network is obtained by searching the area.

[0013] Preferably, in the active power distribution network, the area excluding the fault power loss area and the non-fault power loss area is the normal power supply area of ​​the active power distribution network.

[0014] Preferably, a non-closed branch between a normal power supply area and a non-fault power failure area in the active distribution network is searched to obtain a backup contact line that can be used for power supply restoration in the active distribution network, and a contact switch is set on the backup contact line.

[0015] Preferably, in step S3, the voltage-free detection refers to detecting whether there is no voltage on the switch line side.

[0016] Preferably, in step S3, the synchronization check refers to detecting whether the grid voltage frequency, voltage amplitude and voltage phase on both sides of the grid connection point meet the synchronization conditions.

[0017] Therefore, the advantages of the present invention are: (1) Through the intelligent closing self-healing strategy that combines voltage detection, synchronization detection, and small power supply linkage, the self-healing circuit breaker is self-healed while avoiding the disconnection of distributed power sources as much as possible, so as to achieve rapid power supply restoration in the non-fault power-off area of ​​the active distribution network; (2) The inertia of distributed power sources can be distinguished by the voltage change rate in the non-fault power-off area after a distribution network fault occurs, so as to avoid the impact of asynchronous closing on the system and ensure the reliable and stable operation of the system; (3) Through the intelligent closing strategy combining adaptive closing and joint cutting of small power sources, the success rate of self-healing closing in the case of distributed power supply access is improved, ensuring the rapidity and reliability of system power supply recovery; (4) It improves the continuous output capacity of distributed power sources in the event of system failures, effectively avoids the adverse effects caused by a large number of distributed power sources being disconnected from the grid, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of a method for rapid power restoration of an active distribution network based on an intelligent closing self-healing strategy in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0020] A method for rapid power restoration of an active distribution network based on an intelligent closing self-healing strategy comprises the following steps: Step S1: monitor whether the active distribution network has a fault at every set time interval; Step S2: When a fault occurs in the active distribution network, the fault is removed and isolated, and the distributed power supply in the fault power-off area is removed at the same time; Step S3: Within the closing time limit, a voltage check is performed on the non-fault power-off area. If the voltage-free condition is met, the tie switch is closed to restore power supply to the non-fault power-off area; otherwise, a synchronization check is performed. If the synchronization condition is met, the tie switch is closed; Step S4: If the no-voltage condition and the synchronization condition are still not met after the closing time limit is exceeded, it is determined whether the voltage change rate of the non-fault power-off area is less than the set value; Step S5: If the voltage change rate of the non-fault power-off area is less than the set value, close the tie switch; otherwise, cut off the small power supply branch of the non-fault power-off area and return to step S3.

[0021] The present invention provides a method for rapid power restoration of an active distribution network based on an intelligent closing self-healing strategy. In view of whether a non-fault power-off area contains a small power source after a distribution network fault and the differences in the characteristics of the small power source, an intelligent closing self-healing strategy combining voltage detection, synchronization detection and joint cutting of small power sources is proposed. The self-healing switch is performed while avoiding the distributed power source from being disconnected from the grid as much as possible, so as to realize rapid power restoration of the non-fault power-off area of ​​the active distribution network. Figure 1 As shown in the figure, the specific process is as follows: after a fault occurs in the distribution network system, the fault is quickly removed and isolated, and the distributed power supply in the fault power-off area is removed at the same time; for the non-fault power-off area, when the protective self-healing device closes the tie switch, it first checks for no voltage, and if the non-fault power-off area meets the no voltage condition, it quickly closes the switch; if the no voltage condition is not met, it checks for synchronization, and closes the switch if the synchronization condition is met; when the no voltage check and the synchronization check are still not met within a period of time (closing time limit), it is determined whether the voltage change rate in the non-fault power-off area is less than the set value, and if Then the interconnection switch is closed forcefully, otherwise the strategy of cutting off small power sources is started to cut off the small power branches in the non-fault power-off area, and the interconnection switch is closed after creating a voltage-free condition for the self-healing switch. The present invention distinguishes the inertia of distributed power sources by the voltage change rate in the non-fault power-off area after a distribution network failure, avoids the impact of asynchronous closing on the system, and ensures the reliable and stable operation of the system; through the intelligent closing strategy combining adaptive closing and cutting off small power sources, the success rate of self-healing gates in the case of distributed power access is improved, and the rapidity and reliability of system power supply recovery are ensured; the continuous output capacity of distributed power sources in the case of system failure is improved, and the adverse effects caused by a large number of distributed power sources being disconnected from the grid are effectively avoided, and it has good application prospects.

[0022] When the active distribution network fails, the distributed generation grid connection point can detect the sudden change. The specific process of step S1 includes the following steps: Step S11: collecting three-phase voltage and current of the voltage transformer and the current transformer at the distributed power grid connection point; Step S12: filtering and Fourier baseband extraction of the collected three-phase voltage and current to obtain sampling values ​​of the three-phase voltage and current; Step S13: Calculate the fault component values ​​of the three-phase voltage and current by detecting the sampling value of the cycle before the sudden change and the sampling value of the cycle after the sudden change; Step S14: Decoupling the fault component values ​​of the three-phase voltage and current into positive, negative and zero-sequence fault components of the current and voltage through phase mode transformation; Step S15: Calculate the equivalent backside impedance of the distributed power source equivalent to the Thevenin theorem using the positive sequence fault components of the current and voltage; Step S16: using the equivalent back impedance of the distributed power source to calculate in real time the setting values ​​of the adjacent protection points upstream and downstream of the distributed power source access point; Step S17: Compare the setting value of each protection point with the current value actually measured at the protection installation point. When the actual value is greater than the calculated setting value, it is determined that a fault has occurred.

[0023] When an active distribution network fails, the entire distribution network is divided into three parts, including the normal power supply area, the fault power loss area, and the non-fault power loss area downstream of the fault power loss area.

[0024] The specific faulty component is determined through fault location technology, and the faulty component is isolated within a certain area using protection devices to obtain the fault power outage area of ​​the active distribution network.

[0025] In the downstream area of ​​the fault power-off area, the non-fault power-off area of ​​the active distribution network is obtained by searching the area.

[0026] In an active distribution network, the area excluding the fault power-off area and the non-fault power-off area is the normal power supply area of ​​the active distribution network.

[0027] Search for non-closed branches between the normal power supply area and the non-fault power outage area in the active distribution network to obtain a spare tie line that can be used for power supply restoration in the active distribution network, set a tie switch on the spare tie line, close the tie switch, and restore power supply to the non-fault power outage area.

[0028] In step S3, the voltage-free detection refers to detecting whether there is no voltage on the switch line side.

[0029] In step S3, synchronization check refers to detecting whether the grid voltage frequency, voltage amplitude, and voltage phase on both sides of the grid connection point meet the synchronization conditions.

[0030] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for rapid power restoration of an active distribution network based on an intelligent closing self-healing strategy, characterized in that: The following steps are involved: Step S1: monitor whether the active distribution network has a fault at every set time interval; Step S2: When a fault occurs in the active distribution network, the fault is removed and isolated, and the distributed power supply in the fault-affected area is removed at the same time; Step S3: Checking for no voltage in the non-fault power-off area within the closing time limit, and if the no voltage condition is met, closing the tie switch to restore power supply to the non-fault power-off area; otherwise, checking synchronization, and closing the tie switch if the synchronization condition is met; Step S4: If the no-voltage condition and the synchronization condition are still not met after the closing time limit is exceeded, it is determined whether the voltage change rate of the non-fault power-off area is less than the set value; Step S5: If the voltage change rate of the non-fault power-off area is less than the set value, close the tie switch; otherwise, cut off the small power supply branch of the non-fault power-off area and return to step S3.

2. According to claim 1, a method for rapid power restoration of active distribution network based on intelligent closing self-healing strategy is characterized in that: When the active distribution network fails, the distributed generation grid connection point can detect the sudden change. The specific process of step S1 includes the following steps: Step S11: collecting three-phase voltage and current of the voltage transformer and the current transformer at the distributed power grid connection point; Step S12: filtering and Fourier baseband extraction of the collected three-phase voltage and current to obtain sampling values ​​of the three-phase voltage and current; Step S13: Calculate the fault component values ​​of the three-phase voltage and current by detecting the sampling value of the cycle before the sudden change and the sampling value of the cycle after the sudden change; Step S14: Decouple the fault component values ​​of the three-phase voltage and current into positive, negative and zero current and voltage through phase mode transformation. Sequence fault component; Step S15: Calculate the equivalent backside impedance of the distributed power source equivalent to the Thevenin theorem using the positive sequence fault components of the current and voltage; Step S16: using the equivalent back impedance of the distributed power source to calculate in real time the setting values ​​of the adjacent protection points upstream and downstream of the distributed power source access point; Step S17: Compare the setting value of each protection point with the current value actually measured at the protection installation point. When the actual value is greater than the calculated setting value, it is determined that a fault has occurred.

3. A method for rapid power restoration of an active distribution network based on an intelligent closing self-healing strategy according to claim 1 or 2, characterized in that: When an active distribution network fails, the entire distribution network is divided into three parts, including the normal power supply area, the fault power loss area, and the non-fault power loss area downstream of the fault power loss area.

4. The method for rapid power restoration of active distribution network based on intelligent closing self-healing strategy according to claim 3 is characterized in that: The specific faulty component is determined by the fault location technology, and the faulty component is isolated within a certain area by using a protection device to obtain the fault power failure area of ​​the active distribution network.

5. The method for rapid power restoration of active distribution network based on intelligent closing self-healing strategy according to claim 4 is characterized in that: In the downstream area of ​​the fault power-off area, the non-fault power-off area of ​​the active distribution network is obtained by searching the area.

6. The method for rapid power restoration of active distribution network based on intelligent closing self-healing strategy according to claim 5 is characterized in that: In the active power distribution network, the area except the fault power loss area and the non-fault power loss area is the normal power supply area of ​​the active power distribution network.

7. The method for rapid power restoration of active distribution network based on intelligent closing self-healing strategy according to claim 6 is characterized in that: A non-closed branch between a normal power supply area and a non-fault power failure area in the active distribution network is searched to obtain a backup contact line that can be used for power supply restoration in the active distribution network, and a contact switch is set on the backup contact line.

8. The method for rapid power restoration of active distribution network based on intelligent closing self-healing strategy according to claim 1 is characterized in that: In step S3, the voltage-free detection refers to detecting whether there is no voltage on the switch line side.

9. A method for rapid power restoration of an active distribution network based on an intelligent closing self-healing strategy according to claim 1 or 8, characterized in that: In step S3, the synchronization check refers to detecting whether the grid voltage frequency, voltage amplitude, and voltage phase on both sides of the grid connection point meet the synchronization conditions.

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