A method for loop closing power supply of a power distribution network system with phase angle difference

Abstract

The application relates to a loop closing power supply method of a power distribution network system with phase angle difference, which comprises the following steps: step S1, calculating impedance reference values of a left transformer and a right transformer of a loop closing point of a loop closing line; step S2, calculating a reference voltage of the loop closing point of the loop closing line; step S3, calculating a voltage reference value of the loop closing point of the loop closing line; step S4, calculating a current reference value of the loop closing point of the loop closing line; step S5, calculating a reference value of a loop closing current boundary value when the loop is closed; step S6, calculating a measured value of the loop closing current boundary value when the loop is closed; and step S7, judging whether the loop closing power supply can be performed. The application can effectively solve the problem that the existing power distribution network system does not consider the influence of distributed power operation when the loop closing power supply is performed, the improper loop closing is prone to occurring, the line is in disorder trip, the users are powered off, and the safe operation of the power grid is affected.

Description

Technical Field

[0002] This invention relates to the field of power distribution networks, and more particularly to a loop-to-loop power supply method for power distribution network systems with phase angle differences. Background Technology

[0004] Currently, when power distribution networks perform loop-connection and transfer operations, the commissioning of distributed generation sources is not considered, which breaks the traditional current and voltage constraints. Therefore, the phase angle of the transformer output voltage within the distribution network is assumed to be a fixed value. This fixed value is obtained through measurement after the distribution network is constructed, defined as the theoretical initial phase angle, and input into the SCADA system. During the operation of the distribution network, the factor of distributed generation sources is not considered when performing loop-connection and transfer operations. The loop-connection feasibility is determined solely based on the theoretical initial phase angle. This is because the phase angle of the output voltage of the transformers on the left and right sides of the line to be connected will frequently change due to the commissioning of distributed generation sources, whether they generate electricity or not, and the magnitude of their generation output. If the SCADA system is still used to call the theoretical initial phase angle for loop-connection feasibility determination, improper loop-connection can easily occur, leading to disorderly line tripping, power outages for users, and affecting the safe operation of the power grid. Summary of the Invention

[0006] The purpose of this invention is to provide a loop-locking power transfer method for distribution network systems with phase angle difference. This method can effectively solve the problem that existing distribution network systems, when performing loop-locking power transfer, do not consider the impact of distributed power generation, which can easily lead to improper loop-locking, resulting in disordered line tripping, power outages for users, and affecting the safe operation of the power grid.

[0007] The technical solution adopted by this invention to solve its technical problem is: a loop-connected power supply method for a distribution network system with phase angle difference, comprising the following steps:

[0008] Step S1: Calculate the per-unit impedance value of the transformer to the left of the loop-closing point in the circuit to be closed. and the per-unit impedance of the transformer on the right. ;

[0009] ,

[0010] In the formula, This is the short-circuit impedance of the transformer on the left. As the baseline capacity of the distribution network system, This refers to the rated capacity of the transformer on the left; here, "left" and "right" refer to the left and right sides of the loop-to-close point of the circuit to be closed.

[0011] ,

[0012] In the formula, This is the short-circuit impedance of the transformer on the right. As the baseline capacity of the distribution network system, This refers to the rated capacity of the transformer on the right; here, "left" and "right" refer to the left and right sides of the loop-to-close point of the circuit to be closed.

[0013] Step S2: Calculate the reference voltage at the loop-to-be-closed point of the circuit. ,

[0014] ,

[0015] In the formula, This represents the amplitude of the reference voltage of the transformer on the left. The theoretical initial phase angle of the output voltage of the left transformer is obtained directly from the system. This represents the amplitude of the reference voltage of the transformer on the right. The theoretical initial phase angle of the output voltage of the right-side transformer is obtained directly from the system; here, left and right refer to the left and right sides of the loop-to-close point of the circuit to be closed.

[0016] Step S3: Based on step S2, calculate the per-unit voltage value at the loop-closing point of the circuit to be closed. ,

[0017] ,

[0018] In the formula, The value of the voltage level of the line to be closed in the loop;

[0019] Step S4: Calculate the per-unit current value at the loop-to-close point of the circuit to be closed based on step S3. :

[0020] ;

[0021] Step S5: Based on step S4, calculate the reference value of the loop current boundary value when the loop is closed. :

[0022] , This represents the per-unit impedance value of the line to the left of the loop closure point. This represents the per-unit impedance value of the line to the right of the loop closure point;

[0023] Step S6: Measured values ​​of the loop current boundary values ​​when calculating the loop closure based on step S5. : ,

[0024] in, The measured phase angle of the transformer output voltage to the left of the loop-to-close point during the fitting loop is given. The measured phase angle of the transformer output voltage to the right of the loop-to-close point during the fitting process; Let be the phase angle difference between the output voltages of the transformer to the left and the output voltages of the transformer to the right of the loop-fitting point. This represents the theoretical initial phase angle difference between the output voltages of the transformer on the left and right sides of the loop to be closed.

[0025] Step S7: Based on the rated capacity of the transformer to the left of the loop point to be closed. The rated capacity of the transformer on the right side of the loop to be closed. and the current carrying capacity of the loop line to be closed. In step S6 and , , Compare the minimum of the three values. If the minimum value is less than or equal to N times, it is considered a compound cycle; if If the value is greater than N times the minimum value, it is determined that the loop cannot be closed. N times is the set threshold.

[0026] The beneficial effects of this invention are as follows: By considering the impact of distributed power generation commissioning, when determining the feasibility of loop-connection power transfer, the measured phase angles of the output voltage of the transformer on the left and right sides of the point to be connected are measured in real time, and then the measured values ​​of the loop-connection current boundary values ​​are calculated. Based on the measured values ​​of the loop-connection current boundary values, the conditions for loop-connection power transfer are determined. This effectively solves the problem that existing distribution network systems, when performing loop-connection power transfer, do not consider the impact of distributed power generation commissioning, which can easily lead to improper loop-connection, resulting in disordered line tripping, power outages for users, and affecting the safe operation of the power grid.

[0027] The following examples will provide a more detailed description of the present invention. Detailed Implementation

[0029] An embodiment of a loop-based power transfer method for a distribution network system with phase angle difference includes the following steps:

[0030] Step S1: Calculate the per-unit impedance value of the transformer to the left of the loop-closing point in the circuit to be closed. and the per-unit impedance of the transformer on the right. ,

[0031] ,

[0032] In the formula, This is the short-circuit impedance of the transformer on the left. As the baseline capacity of the distribution network system, This represents the rated capacity of the transformer on the left.

[0033] ,

[0034] In the formula, This is the short-circuit impedance of the transformer on the right. As the baseline capacity of the distribution network system, This is the rated capacity of the transformer on the right.

[0035] Step S2: Calculate the reference voltage at the loop-to-be-closed point of the circuit. ,

[0036] ,

[0037] In the formula, This represents the amplitude of the reference voltage of the transformer on the left. The initial phase angle of the output voltage of the left transformer is retrieved through the SCADA system. This represents the amplitude of the reference voltage of the transformer on the right. The initial phase angle of the output voltage of the right-side transformer is retrieved through the SCADA system;

[0038] Step S3: Based on step S2, calculate the per-unit voltage value at the loop-closing point of the circuit to be closed. ,

[0039] ,

[0040] In the formula, The value of the voltage level of the line to be closed in the loop;

[0041] Step S4: Calculate the per-unit current value at the loop-to-close point of the circuit to be closed based on step S3. :

[0042] ;

[0043] Step S5: Based on step S4, calculate the reference value of the loop current boundary value when the loop is closed. :

[0044] , This represents the per-unit impedance value of the line to the left of the loop closure point. This represents the per-unit impedance value of the line to the right of the loop closure point;

[0045] When it is inconvenient to measure and The value of can be 0.

[0046] Step S6: Measured values ​​of the loop current boundary values ​​when calculating the loop closure based on step S5. : ,

[0047] in, The measured phase angle of the transformer output voltage to the left of the loop-closing point during the fitting process was obtained through real-time measurement. The phase angle of the transformer output voltage to the right of the loop-to-close point is obtained through real-time measurement. Let be the phase angle difference between the output voltages of the transformer to the left and the output voltages of the transformer to the right of the loop-fitting point. The initial phase angle difference between the output voltages of the transformer on the left and right sides of the loop to be closed;

[0048] In a line with a 30° phase angle difference ;

[0049] Step S7: Based on the rated capacity of the transformer to the left of the loop point to be closed. The rated capacity of the transformer on the right side of the loop to be closed. and the current carrying capacity of the loop line to be closed. In step S6 and , , Compare the minimum of the three values. If the minimum value is less than or equal to N times, it is considered a compound cycle; if If the current carrying capacity of the line to be closed is greater than N times the minimum value, it is determined that the loop cannot be closed. This is the value specified in the power line operation regulations. N times is the set threshold, where N can be set to 2 or other suitable values, and is obtained based on the overload curve in the transformer operation regulations.

[0050] In step S3, The values ​​are for the voltage levels of the lines to be closed in the loop, where the value for the 0.4kV bus is 0.4kV, the value for the 10kV bus is 10.5kV, the value for the 35kV bus is 37kV, the value for the 110kV bus is 115kV, the value for the 220kV bus is 230kV, and the value for the 380V bus is 380V.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Additionally, the term "comprising" and any variations thereof are intended to cover non-exclusive inclusion.

[0052] The above embodiments are not intended to limit the scope of the invention, but rather to illustrate it. The scope of the invention is determined by the scope of the claims, not by the description itself, and should be interpreted as including all differences within the equivalent scope. Any non-substantial improvements made using the inventive concept and technical solutions, or the direct application of the above-described concepts and technical solutions of the invention to other situations without modification, are all within the protection scope of the invention.

Claims

1. A method for loop-to-loop power transfer in a distribution network system with phase angle difference, characterized in that: Includes the following steps: Step S1: Calculate the per-unit impedance value of the transformer to the left of the loop-closing point in the circuit to be closed. and the per-unit impedance of the transformer on the right. , ， In the formula, This is the short-circuit impedance of the transformer on the left. As the baseline capacity of the distribution network system, This represents the rated capacity of the transformer on the left. ， In the formula, This is the short-circuit impedance of the transformer on the right. As the baseline capacity of the distribution network system, This is the rated capacity of the transformer on the right. Step S2: Calculate the reference voltage at the loop-to-be-closed point of the circuit. , , In the formula, This represents the amplitude of the reference voltage of the transformer on the left. This represents the initial phase angle of the output voltage of the transformer on the left. This represents the amplitude of the reference voltage of the transformer on the right. This represents the initial phase angle of the output voltage of the transformer on the right. Step S3: Based on step S2, calculate the per-unit voltage value at the loop-closing point of the circuit to be closed. , ， In the formula, The value of the voltage level of the line to be closed in the loop; Step S4: Calculate the per-unit current value at the loop-to-close point of the circuit to be closed based on step S3. : ； Step S5: Based on step S4, calculate the reference value of the loop current boundary value when the loop is closed. : , This represents the per-unit impedance value of the line to the left of the loop closure point. This represents the per-unit impedance value of the line to the right of the loop closure point; Step S6: Measured values ​​of the loop current boundary values ​​when calculating the loop closure based on step S5. : , in, The measured phase angle of the transformer output voltage to the left of the loop-to-close point during the fitting loop is given. The measured phase angle of the transformer output voltage to the right of the loop-to-close point during the fitting process; Let be the phase angle difference between the output voltages of the transformer to the left and the output voltages of the transformer to the right of the loop-fitting point. The initial phase angle difference between the output voltages of the transformer on the left and right sides of the loop to be closed; Step S7: Based on the rated capacity of the transformer to the left of the loop point to be closed. Rated capacity of the transformer on the right side of the loop to be closed. and the current carrying capacity of the loop line to be closed. In step S6 and , , Compare the minimum of the three values. If the minimum value is less than or equal to N times, it is considered a compound cycle; if If the value is greater than N times the minimum value, it is determined that the loop cannot be closed. N times is the set threshold.

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