Power distribution network neutral point displacement voltage identification method and active suppression method

Abstract

The invention discloses a power distribution network neutral point displacement voltage identification method, and belongs to the technical fields of electric power system analysis, operation and electric energy quality comprehensive treatment. The invention aims to provide the power distribution network neutral point displacement voltage identification method and an active suppression method, which are used for judging the cause of neutral point displacement voltage generation according to the ratio of an injection current signal to measured voltage, calculating an ideal injection current value by utilizing the asymmetry of a power grid and suppressing the generation of the neutral point displacement voltage. By measuring the change conditions of the real part and the imaginary part in admittance, the reason for generating the neutral point displacement voltage of the power distribution network is identified. According to the method, the reason of neutral point displacement voltage generation is judged according to the change conditions of conductance and susceptance in admittance measurement, the neutral point displacement voltage can be suppressed by injecting current before theneutral point voltage exceeds the specified 15% phase voltage, and whether the power grid has other fault types or not can be distinguished. An active inverter is controlled by a closed-loop controlmethod, so that the accuracy and controllability of the injection current are ensured.

Description

technical field [0001] The invention belongs to the technical field of power system analysis, operation and comprehensive control of power quality. Background technique [0002] my country's medium-voltage distribution network is generally dominated by arc-suppressing coils or ungrounded systems. In ungrounded systems, due to poor transposition of overhead lines, high-voltage loads in distribution networks, and the appearance of ferromagnetic resonance, etc. will cause The three phase-to-ground parameters are not equal to each other, making the neutral point appear asymmetrical voltage. [0003] In the system grounded by the arc-suppression coil, the input of the arc-suppression coil increases the zero-sequence impedance between the neutral point and the earth, which increases the displacement voltage of the neutral point, and the large overvoltage will cause power lines, transformers The efficiency and performance of electrical equipment such as transformers and transformer...

AI Technical Summary

Problems solved by technology

[0003]In the system grounded by the arc suppression coil, the input of the arc suppression coil increases the zero-sequence impedance between the neutral point and the earth, which makes the neutral point shift When the voltage increases, a large overvoltage will reduce the efficiency and performance of electrical equipment such as power lines, transformers, and transformers, and reduce the safety and economic performance of the power grid.

[0004]The existing neutral point displacement voltage suppression method of distribution network mainly adopts the method of switching three-phase coupling capacitors to compensate the unbalance of line-to-ground capacitance. The method is easy to operate and is widely used in power systems. However, in actual operation, it is difficult to track the dynamic changes of the power grid in real time and cannot achieve dynamic compensation of the neutral point voltage.

With the development of power electronics technology, the static synchronous compensator composed of self-commutated bridge circuit with turn-off IGBT can compensate the neutral point displacement voltage of low-voltage distribution network due to unbalanced three-phase load. The application of balanced load problem is more and more widely, but in the operation of medium-voltage distribution network, the main reason of three-phase unbalance is the unequal capacitance of line to ground, this method cannot suppress the overshoot caused by unbalanced parameters to ground. Voltage

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