Inhibition method for three-phase imbalance voltages of power distribution network

Abstract

The invention discloses an inhibition method for three-phase imbalance voltages of a power distribution network. The method includes the following steps: installing a controllable current source between a neutral point of the power distribution network and the ground; measuring three-phase voltages and a neutral-point displacement voltage of the power distribution network in a real-time manner; when the displacement voltage is larger than 5% of a rated phase voltage, identifying whether the operation state of the power distribution network is a three-phase imbalance state; and under a condition of the three-phase imbalance state of the power distribution network, injecting a power frequency current I <*> to the power distribution network through the controllable current source and searching for an optimal injection current phase and amplitude and inhibiting the neutral-point displacement voltage to be zero. The method uses the neutral-point displacement voltage as a control target and forces the neutral-point displacement voltage to be zero through injection of the current to the power distribution network so that neutral-point displacement overvoltage caused by asymmetry of three-phase to-ground parameters of the power distribution network is eliminated completely and thus inhibition of three-phase imbalance overvoltages of the power distribution network is realized.

Description

technical field [0001] The invention relates to a method for suppressing three-phase unbalanced voltage of a distribution network. Background technique [0002] The distribution network generally adopts the non-effective neutral point grounding method, and the zero-sequence impedance is large. If the parameters of the three phases are asymmetrical, it will cause a displacement voltage of the neutral point, and a large displacement voltage will affect the normal operation of the distribution network. [0003] There are many situations that cause the asymmetry of the three-phase-to-ground parameters of the distribution network, such as: the three-phase non-transposition of the overhead line, the single-phase high-voltage load in the distribution network, and the non-full phase disconnection of the distribution network. With the increase of the three-phase asymmetry of the distribution network, it will lead to a serious imbalance in the three-phase-to-earth leakage current, res...

AI Technical Summary

Problems solved by technology

The saturable reactor has the advantages of fast response and stable performance, but because the device needs to magnetize the iron core to reach the saturation state, it has the disadvantages of large noise, large power consumption, and high cost, so it has not been popularized and applied.

[0006] With the rapid development of power electronics technology, a three-phase unbalanced overvoltage suppression method for distribution networks based on thyristor-controlled switching capacitor banks has been proposed at home and abroad, but this method is expensive and prone to harmonics, and has not been popularized and applied.

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