Optimal configuration method for switching time of power exchange device applicable to incoming line of distribution network substation

Abstract

The present invention discloses a method for optimizing the switching time of a power exchange device for incoming lines of a distribution network substation. The method can effectively improve the safety of power supply of the distribution network and the reliability of power supply of the distribution network, and avoid equipment damage and power grid accidents. The method mainly verifies in advance whether the power flow after the closed-loop power exchange is overloaded and whether the bus voltages on both sides exceed the limit through power flow calculation, and optimizes the power exchange time parameters after the closed-loop power exchange to ensure that the transient process has ended and entered a stable state. Therefore, it is suitable for promotion and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system distribution network operation and control, and specifically, relates to a method for optimizing the switching time configuration of a power exchange device applicable to an incoming line of a distribution network substation. Background Art

[0002] With the rapid development of urban distribution networks, distribution networks mostly present a "closed-loop structure, open-loop operation" pattern. When the distribution network is under maintenance or fails, it is necessary to perform a loop-closing and power-changing operation to improve power supply reliability and avoid load loss. Since the voltage amplitude and phase angle of the busbars on both sides before the distribution network is closed are generally different, an impact will be generated at the closing point during the closing, causing system disturbances; after the closing, the closing point is powered by both sides, and the short-circuit current increases compared to before the closing, and there is a risk of short-circuit current exceeding the standard. In addition, the power-changing operation will also cause disturbances to the system; after the power-changing operation, the system will return to stability after a transient process, and the power flow will be redistributed, and there is a risk of power flow overload and voltage exceeding the limit. Summary of the invention

[0003] The purpose of the present invention is to provide a method for optimizing the switching time of a power exchange device suitable for a distribution network substation incoming line. The method can effectively improve the safety of the distribution network power supply and the reliability of the distribution network power supply, and avoid equipment damage and power grid accidents.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A method for optimizing the switching time of a power exchange device applicable to an incoming line of a distribution network substation comprises the following steps:

[0006] S1: Establish the substation topology and branch admittance analysis model;

[0007] S2: Collect the power of the incoming and outgoing branches of the substation, and the voltage and phase of bus I and bus II;

[0008] S3: Calculate the voltage amplitude difference △U and phase difference △Ψ between bus I and bus II;

[0009] S4: If △U / Un is less than the set ratio and △Ψ is less than the set angle, proceed to step S5; otherwise, proceed to step S2; wherein Un is the rated voltage;

[0010] S5: The bus tie between busbars I and II is closed, i.e. the device closing logic is executed;

[0011] S6: Calculate the bus voltage change rate δ%=(Umax-Umin) / Un every 1 second; where Umax is the maximum bus voltage and Umin is the minimum bus voltage;

[0012] S7: If δ% is less than the set ratio, proceed to step S9; otherwise proceed to step S8;

[0013] S8: counter count = 0, go to step S6;

[0014] S9: counter count=count+1, where the initial value of count is 0;

[0015] S10: If count is greater than the set value, go to step S11; otherwise go to step S6;

[0016] S11: Use the Newton-Raphson method to calculate the power flow distribution after the incoming branch to be disconnected is disconnected;

[0017] S12: If the power of all incoming branch lines is not overloaded and the bus voltage is not over the limit, then go to step S13; otherwise, go to step S14;

[0018] S13: executing the circuit breaker disconnection logic of the incoming branch to be disconnected, that is, executing the power replacement logic of the device;

[0019] S14: Device alarm message: The substation load is too large, resulting in an incoming power flow overload or bus voltage exceeding the limit. Consider re-switching after reducing the load, that is, the current power switching operation has failed;

[0020] S15: End the battery replacement.

[0021] Furthermore, in the present invention, in step S4, the setting ratio of ΔU / Un is 30%, and the setting angle of the phase difference ΔΨ is 30 degrees.

[0022] Furthermore, in the present invention, in step S7, the setting value of the primary bus voltage change rate δ% is 2%.

[0023] Furthermore, in the present invention, in step S10, the setting value of count is 20.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention uses power flow calculation to check in advance whether the power flow after the closed-loop power exchange is overloaded, whether the bus voltages on both sides are over-limited, and optimizes the power exchange time parameters after the closed-loop power exchange to ensure that the transient process has ended and entered a stable state. This method can avoid the risks of power flow overload and bus voltage over-limit in closed-loop power exchange and improve the power supply reliability of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the process structure of the method of the present invention.

[0027] Figure 2The figure is a schematic diagram of the admittance structure of the substation inlet branch in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments.

[0029] Example

[0030] like Figure 1 As shown, the present invention discloses a method for optimizing the switching time of a power exchange device applicable to a distribution network substation incoming line, comprising the following steps:

[0031] S1: Establish the substation topology and branch admittance analysis model; Figure 2 A common schematic diagram of substation incoming branch admittance structure is given.

[0032] S2: Collect the power of the incoming and outgoing branches of the substation, and the voltage and phase of bus I and bus II; mainly through the AC plug-in of the automatic ring-closing power switching device.

[0033] S3: Calculate the voltage amplitude difference △U and phase difference △Ψ between bus I and bus II; this part is mainly processed by the CPU module of the automatic closing-loop switching device.

[0034] S4: If △U / Un<30% and △Ψ<30 degrees, go to step S5; otherwise, go to step S2; wherein Un is the rated voltage; this part is mainly judged by the CPU module of the automatic closing-loop battery replacement device.

[0035] S5: The bus tie between busbars I and II is closed, i.e. the device closing logic is executed;

[0036] S6: Calculate the bus voltage change rate δ%=(Umax-Umin) / Un every 1 second; where Umax is the maximum bus voltage and Umin is the minimum bus voltage;

[0037] S7: If δ%<2%, proceed to step S9; otherwise proceed to step S8;

[0038] S8: counter count = 0, go to step S6;

[0039] S9: counter count=count+1, where the initial value of count is 0;

[0040] S10: If count>20, proceed to step S11; otherwise proceed to step S6; the switching time optimization configuration of this embodiment is equivalent to optimizing the switching time after the loop closing operation, that is, the device switching logic is considered to be executed only after count is greater than 20 and the bus voltage change rate is continuously less than 2% for more than 20s;

[0041] S11: Use the Newton-Raphson method to calculate the power flow distribution after the incoming branch to be disconnected is disconnected;

[0042] S12: If the power of all incoming branch lines is not overloaded and the bus voltage is not over the limit, then go to step S13; otherwise, go to step S14;

[0043] S13: executing the circuit breaker disconnection logic of the incoming branch to be disconnected, that is, executing the power replacement logic of the device;

[0044] S14: Device alarm message: The substation load is too large, resulting in an incoming power flow overload or bus voltage exceeding the limit. Consider re-switching after reducing the load, that is, the current power switching operation has failed;

[0045] S15: End the battery replacement.

[0046] The present invention uses power flow calculation to check in advance whether the power flow after the closed-loop power exchange is overloaded, whether the bus voltages on both sides are over-limited, and optimize the power exchange time parameters after the closed-loop power exchange to ensure that the transient process has ended and entered a stable state. This method can avoid the risks of power flow overload and bus voltage over-limit in the closed-loop power exchange, and improve the power supply reliability of the distribution network. Therefore, it is suitable for promotion and application.

[0047] The above embodiment is only one of the preferred implementation modes of the present invention and should not be used to limit the protection scope of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention.

Claims

1. A method for optimizing the switching time of a power exchange device for a distribution network substation incoming line, characterized in that: The following steps are involved: S1: Establish the substation topology and branch admittance analysis model; S2: Collect the power of the incoming and outgoing branches of the substation, and the voltage and phase of bus I and bus II; S3: Calculate the voltage amplitude difference △U and phase difference △Ψ between bus I and bus II; S4: If △U / Un is less than the set ratio and △Ψ is less than the set angle, proceed to step S5; otherwise, proceed to step S2; wherein Un is the rated voltage; S5: The bus tie between busbars I and II is closed, i.e. the device closing logic is executed; S6: Calculate the bus voltage change rate δ%=(Umax-Umin) / Un every 1 second; where Umax is the maximum bus voltage and Umin is the minimum bus voltage; S7: If δ% is less than the set ratio, proceed to step S9; otherwise proceed to step S8; S8: counter count = 0, go to step S6; S9: counter count=count+1, where the initial value of count is 0; S10: If count is greater than the set value, go to step S11; otherwise go to step S6; S11: Use the Newton-Raphson method to calculate the power flow distribution after the incoming branch to be disconnected is disconnected; S12: If the power of all incoming branch lines is not overloaded and the bus voltage is not over the limit, then go to step S13; otherwise, go to step S14; S13: executing the circuit breaker disconnection logic of the incoming branch to be disconnected, that is, executing the power replacement logic of the device; S14: Device alarm message: The substation load is too large, resulting in an incoming power flow overload or bus voltage exceeding the limit. Consider re-switching after reducing the load, that is, the current power switching operation has failed; S15: End the battery replacement.

2. The switching time optimization configuration method for the power exchange device applicable to the incoming line of the distribution network substation according to claim 1 is characterized in that: In step S4, the setting ratio of ΔU / Un is 30%, and the setting angle of the phase difference ΔΨ is 30 degrees.

3. The switching time optimization configuration method for the power exchange device applicable to the incoming line of the distribution network substation according to claim 2 is characterized in that: In step S7, the setting value of the primary bus voltage change rate δ% is 2%.

4. The switching time optimization configuration method for the power exchange device applicable to the incoming line of the distribution network substation according to claim 3 is characterized in that: In step S10 , the set value of count is 20.

Images