Dual-time-limit Adaptive Reclosing Method Applied to Distributed Power Access System

Abstract

The present invention discloses a dual-time-limit adaptive reclosing method applied to a distributed power access system, belonging to the field of relay protection of power systems. The present invention takes into account that the distributed power is disconnected from the network in the way of protection tripping or splitting, and based on this, the reclosing time limits on both sides of the line are set, which are respectively coordinated with the tripping delay and splitting delay of the distributed power to obtain the first and second reclosing time limits on the grid side and the distributed power side. The reclosing devices on both sides of the line detect whether the reclosing conditions are met within the corresponding reclosing time limits and make responses. On the one hand, by waiting for the distributed power to be disconnected from the network before reclosing, the success rate of reclosing is greatly improved. On the other hand, by setting two time limits to detect the reclosing conditions, the action time of reclosing is accelerated as much as possible, effectively solving the problem that it is difficult for the line to resume power supply through reclosing after the distributed power is connected, and improving the power supply reliability of the power system.

Description

Technical Field

[0001] The present invention belongs to the field of relay protection of power systems, and more specifically, relates to a dual-time-limit adaptive reclosing method applied to a distributed power source access system. Background Art

[0002] In a power system, line faults are mainly transient faults, which are eliminated after the circuit breakers on both sides of the line trip. The reclosing device can automatically close after a predetermined delay after the faulty line is disconnected, which can greatly improve the power supply reliability and reduce the number of line power outages. In a traditional power grid radial network, the reclosing is only configured on the grid side of the line network, and the load side does not need to be configured with a reclosing. After the distributed power source is connected, reclosing needs to be configured on both sides of the line. Since most distributed power sources are connected to the grid through power electronic devices, their electrical inertia is low and the fault characteristics are affected by the fault ride-through control strategy. The amplitude, phase, and frequency of the voltage on the distributed power source side are quite different from those on the system side, and it is difficult to achieve synchronous reclosing. Therefore, a new reclosing method needs to be proposed. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a dual-time-limit adaptive reclosing method applied to a distributed power source access system. By combining the protection and tripping and the distributed power source control strategy, a dual-time-limit reclosing method coordinated with the distributed power source disconnection time is proposed to solve the problem that the existing reclosing strategy cannot successfully reclose after the distributed power source is connected.

[0004] To achieve the above purpose, the present invention provides a dual-time-limit adaptive reclosing method applied to a distributed power source access system. Protection devices and reclosing devices are configured on both the line network side and the distributed power source side of the distributed power source access system. When the protection on the distributed power source side acts, it actively cuts off the distributed power source after a tripping delay Δt LQ ; and when the distributed power source detects island operation, it can self-disconnect and cut off from the power grid after a disconnection delay Δt JL ;

[0005] The method includes the following steps:

[0006] S1: Set the reclosing action time limits of the reclosing devices on the line network side and the distributed power source side according to dual action time limits, where the dual action time limits are coordinated with the distributed power source tripping delay and the disconnection delay respectively;

[0007] S2: After a fault occurs and the protection on the line network side acts, the network-side reclosing is started. After the first action time limit of the network-side reclosing, if the reclosing condition is met, the network-side reclosing acts; otherwise, continue to wait. After the second action time limit of the network-side reclosing, if the reclosing condition is met, the network-side reclosing acts; otherwise, the network-side reclosing does not act;

[0008] S3: After a fault occurs and the protection on the distributed power source side of the line operates, the reclosing of the distributed power source is started. After the first action time limit of the reclosing of the distributed power source, if the reclosing conditions are met, the reclosing of the distributed power source operates; otherwise, continue to wait. After the second action time limit of the reclosing of the distributed power source, if the reclosing conditions are met, the reclosing of the distributed power source operates; otherwise, the reclosing of the distributed power source does not operate.

[0009] Further, in step S1, the first action time limit of the network side reclosing coordinated with the distributed power source's tie-switching delay is: t AR-S1 = Δt LQ + t DG-II - t S-KS - t 合闸 + Δt rel ; the second action time limit of the network side reclosing coordinated with the distributed power source's disconnection delay is: t AR-S2 = Δt JL - t S-KS - t 合闸 + Δt rel ; where t DG-II is the longest action time limit of the main protection on the distributed power source side of the line, t S-KS is the shortest action time limit of the main protection on the network side of the line, t 合闸 is the breaker closing time, and Δt rel is the reliability delay.

[0010] Further, in step S1, the first action time limit of the reclosing of the distributed power source coordinated with the first action time limit of the network side reclosing is: t AR-DG1 = t AR-S1 + t S-II - t DG-KS + t AR延时 ; the second action time limit of the reclosing of the distributed power source coordinated with the second action time limit of the network side reclosing is: t AR-DG2 = t AR-S2 + t S-II - t DG-KS + t AR延时 ; where t S-II is the longest action time limit of the main protection on the network side of the line, t DG-KS is the shortest action time limit of the main protection on the distributed power source side of the line, and t AR延时 is the delay of the reclosing of the distributed power source relative to the reclosing of the network side.

[0011] Further, the disconnection delay Δt JL is taken according to the national standard, and the tie-switching delay Δt LQ is taken according to the communication situation between the distributed power source side protection device and the breaker of the distributed power source access line.

[0012] Further, the reliability delay Δt rel is taken as 20 ms, and the delay t of the reclosing of the distributed power source side relative to the network side reclosing AR延时 is taken as 20 ms.

[0013] Further, in step S2, the reclosing condition is: there is voltage on the bus and no voltage on the line.

[0014] Further, in step S3, the reclosing condition is: there is no voltage on the bus and voltage on the line, or there is voltage on the bus and the bus voltage and the line voltage meet the synchronous reclosing condition.

[0015] Generally speaking, through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0016] The present invention considers the disconnection of the distributed power source in the form of protection connection cutting or splitting, and based on this, the reclosing time limits on both sides of the line are set, which are respectively coordinated with the connection cutting delay and splitting delay of the distributed power source to obtain the first and second reclosing time limits on the network side and the distributed power source side. The reclosing devices on both sides of the line detect whether the reclosing conditions are met within the corresponding reclosing time limits and respond. On the one hand, by waiting for the distributed power source to disconnect from the network before reclosing, the success rate of reclosing is greatly improved. On the other hand, by setting two time limits to detect the reclosing conditions, the action time of reclosing is accelerated as much as possible, effectively solving the problem that it is difficult for the line to resume power supply through reclosing after the distributed power source is connected, and improving the power supply reliability of the power system. Brief Description of the Drawings

[0017] Figure 1 is a flowchart of a double-time-limit adaptive reclosing method applied to a distributed power source access system provided by the present invention;

[0018] Figure 2 is a flowchart of the network side reclosing of the line provided by the present invention;

[0019] Figure 3 is a flowchart of the distributed power source side reclosing of the line provided by the present invention;

[0020] Figure 4 is a schematic structural diagram of a typical distributed power source access system provided by the present invention, where: 1 - network side equivalent power source, 2 - network side 110 kV bus, 3 - network side circuit breaker, 4 - transmission line, 5 - distributed power source side circuit breaker, 6 - distributed power source side 110 kV bus, 7 - 110 kV transformer, 8 - 10 kV bus, 9 - 10 kV load, 10 - distributed power source outgoing line circuit breaker, 11 - distributed power source. Detailed Embodiment

[0021] To make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0022] In view of the problem that the line cannot correctly restore power supply through reclosing after the access of distributed power sources, the present invention proposes a dual-time-limit adaptive reclosing method applied to a distributed power source access system, and its logic block diagram is as Figures 1 to 3 shown, and the system structure schematic diagram of this embodiment is as Figure 4 shown.

[0023] Referring to Figure 1 , the present invention provides a dual-time-limit adaptive reclosing method applied to a distributed power source access system, including steps S1 to S3:

[0024] Step S1: Set the reclosing operation time limits of the line network side and distributed power source side reclosing devices according to dual operation time limits, where the dual operation time limits are respectively coordinated with the distributed power source tripping delay and islanding delay.

[0025] In this embodiment, in step S1, the first operation time limit of the network side reclosing coordinated with the distributed power source tripping delay is: t AR-S1 =Δt LQ +t DG-II -t S-KS -t 合闸 +Δt rel ; the second operation time limit of the network side reclosing coordinated with the distributed power source islanding delay is: t AR-S2 =Δt JL -t S-KS -t 合闸 +Δt rel . Among them, t DG-II is the longest operation time limit of the main protection on the distributed power source side of the line, for example, the operation time limit of the second section protection on the distributed power source side of the line, taking 600 ms, t S-KS is the shortest operation time limit of the main protection on the network side of the line, taking 30 ms, t 合闸 is the breaker closing time, taking 10 ms, the tripping delay Δt LQ takes 10 ms, the islanding delay Δt JL takes 2000 ms according to the national standard, and the reliability delay Δt rel takes 20 ms. Thus, the first operation time limit t AR-S1 =590 ms and the second operation time limit t AR-S2 =1980 ms of the network side reclosing can be obtained.

[0026] In this embodiment, in step S1, the first reclosing operation time limit of the distributed power source side coordinated with the first reclosing operation time limit of the network side is: t AR-DG1 = t AR-S1 + t S-II - t DG-KS + t AR延时 ; the second reclosing operation time limit of the distributed power source side coordinated with the second reclosing operation time limit of the network side is: t AR-DG2 = t AR-S2 + t S-II - t DG-KS + t AR延时 . Among them, t S-II is the longest operation time limit of the main protection on the network side of the line. For example, the operation time limit of the second section protection on the network side of the line is taken as 300 ms, t DG-KS is the shortest operation time limit of the main protection on the distributed power source side of the line, taken as 30 ms, t AR延时 is the delay of the reclosing on the distributed power source side relative to the reclosing on the network side, taken as 20 ms. Thus, the first reclosing time limit t AR-DG1 = 880 ms, and the second operation time limit t AR-DG2 = 2270 ms.

[0027] Step S2: After a fault occurs and the line network side protection operates, the network side reclosing is started. After the first reclosing operation time limit of the network side, if the reclosing condition is met, the network side reclosing operates; otherwise, continue to wait. After the second reclosing operation time limit of the network side, if the reclosing condition is met, the network side reclosing operates; otherwise, the network side reclosing does not operate.

[0028] In this embodiment, in step S2, after the line network side reclosing is started, at 590 ms of the first reclosing operation time limit of the network side, the reclosing device detects whether there is voltage on the bus and no voltage on the line. If so, the network side reclosing operates and sends a closing command to the network side circuit breaker; if not, continue to wait. When reaching 1980 ms of the second reclosing operation time limit of the network side, the reclosing device detects again whether there is voltage on the bus and no voltage on the line. If so, the network side reclosing operates and sends a closing command to the network side circuit breaker; if not, the network side reclosing does not operate.

[0029] Step S3: After a fault occurs and the line distributed power source side protection operates, the distributed power source side reclosing is started. After the first reclosing operation time limit of the distributed power source side, if the reclosing condition is met, the distributed power source side reclosing operates; otherwise, continue to wait. After the second reclosing operation time limit of the distributed power source side, if the reclosing condition is met, the distributed power source side reclosing operates; otherwise, the distributed power source side reclosing does not operate.

[0030] In this embodiment, in step S3, after the reclosing of the distributed power source on the line side is started, the distributed power source removal status flag is set to 0. When the first action time limit of 880 ms for the reclosing of the distributed power source on the line side is reached, the reclosing device of the distributed power source on the line side detects whether the bus has no voltage and the line has voltage, or detects whether the bus has voltage and the bus voltage and the line voltage meet the synchronous reclosing condition. If so, the reclosing of the distributed power source on the line side operates, and a closing command is sent to the circuit breaker on the distributed power source side; if not, the distributed power source removal status flag is set to 1.

[0031] After the distributed power source removal status flag is 1, after a time interval of 1390 ms, the reclosing device of the distributed power source on the line side detects again whether the bus has no voltage and the line has voltage, or detects whether the bus has voltage and the bus voltage and the line voltage meet the synchronous reclosing condition. If so, the reclosing of the distributed power source on the line side operates, and a closing command is sent to the circuit breaker on the distributed power source side; if not, the reclosing of the distributed power source on the line side does not operate.

[0032] Those skilled in the art can easily understand that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A dual-time-limit adaptive reclosing method applied to a distributed power access system, characterized in that In the distributed power access system, protection devices and reclosing devices are configured on both the line network side and the distributed power side. When the protection on the distributed power side operates, after the tripping delay it actively cuts off the distributed power; and when the distributed power detects island operation, after the islanding detection delay it can disconnect itself and be cut off from the power grid; The method includes the following steps: S1: Set the reclosing operation time limits of the reclosing devices on the line network side and the distributed power source side according to the double-action time limits, where the double-action time limits are coordinated with the disconnection delay and the islanding delay of the distributed power source respectively; S2: After a fault occurs and the line network side protection operates, the network side reclosing is started. After the first action time limit of the network side reclosing, if the reclosing conditions are met, the network side reclosing operates; otherwise, continue to wait. After the second action time limit of the network side reclosing, if the reclosing conditions are met, the network side reclosing operates; otherwise, the network side reclosing does not operate; S3: After a fault occurs and the line distributed power source side protection operates, the distributed power source side reclosing is started. After the first action time limit of the distributed power source side reclosing, if the reclosing conditions are met, the distributed power source side reclosing operates; otherwise, continue to wait. After the second action time limit of the distributed power source side reclosing, if the reclosing conditions are met, the distributed power source side reclosing operates; otherwise, the distributed power source side reclosing does not operate; The first operating time limit of the network reclosing in coordination with the disconnection delay of the distributed power source is: ; The second operating time limit of the network reclosing in coordination with the disconnection delay of the distributed power source is: ; Among them, is the longest operating time limit of the main protection on the distributed power source side of the line, is the shortest operating time limit of the main protection on the network side of the line, is the breaker closing time, is the reliability delay; In step S1, the first closing operation time limit of the distributed power source side coordinated with the first closing operation time limit of the network side is: ; the second closing operation time limit of the distributed power source side coordinated with the second closing operation time limit of the network side is: ; where is the longest operation time limit of the main protection on the network side of the line, is the shortest operation time limit of the main protection on the distributed power source side of the line, is the delay of the closing operation of the distributed power source side relative to the closing operation of the network side.

2. The method according to claim 1, wherein Link-cutting delay It is obtained according to the communication status between the distributed power source side protection device and the circuit breaker of the distributed power source access line.

3. The method according to claim 2, wherein Reliability delay Take 20 ms, the delay of reclosing of distributed power sources relative to that of the grid Take 20 ms.

4. The method according to claim 1, characterized in that, In step S2, the reclosing conditions are: there is voltage on the bus and no voltage on the line.

5. The method according to claim 1, characterized in that, In step S3, the reclosing conditions are: there is no voltage on the bus and voltage on the line, or there is voltage on the bus and the bus voltage and the line voltage meet the synchronous closing conditions.

Images