Extraction method of reference voltage of dynamic voltage restorer in neutral point ungrounded system

Abstract

An extracting method of a reference voltage of a dynamic voltage restorer in an isolated neutral system comprises the steps that amplitudes of phase voltages of an A phase, a B phase and a C phase and amplitudes of three line voltages on the DVR system side are measured after faults, the minimum value and the maximum value of the amplitudes of the three line voltages are respectively obtained to judge whether falling off can be compensated, if falling off can be compensated, the measured amplitudes of the three phase voltages on the DVR system side can be compared with corresponding rated values, the procedure is completed when it is determined that no fault occurs according to comparing results, and voltages on the DVR load side after compensation are obtained according to fault types when it is judged that the faults occur; it is determined that reference voltages of the phases of a DVR are phasor differences of the voltages on the DVR system side after compensation and the voltage on the DVR system side after the faults. The voltages needing to be compensated by the DVR can be obtained only by detecting the amplitudes of the phase voltages and the amplitudes of the line voltages on the DVR system side, implementation is easy to achieve, and important practical value is brought to improvement on the practical level of the DVR in the isolated neutral system.

Description

technical field [0001] The invention belongs to the technical field of dynamic voltage restorers, and in particular relates to a method for extracting a reference voltage of a dynamic voltage restorer in a neutral point ungrounded system. Background technique [0002] The voltage sag problem is one of the most frequent and serious power quality problems in the distribution network at present, and the dynamic voltage restorer (Dynamic Voltage Restorer, DVR) is considered to be the most effective means to control the voltage sag problem. There are many reasons for voltage drop, including system short-circuit fault, switching of capacitor bank and starting of large-capacity induction motor. Among them, the most harmful ones are mainly caused by various short-circuit faults in the distribution network. In the 6-35kV distribution network, the neutral point non-effective grounding method is often used. The voltage drop caused by the asymmetric fault has its own particularity, and...

AI Technical Summary

Problems solved by technology

For the non-faulted phase voltage swell caused by asymmetrical faults in the neutral point ungrounded system, there are two methods to deal with it, one is not to deal with it, but this reference voltage calculation method with the phase voltage as the target is compensated The line voltage of the load must be unbalanced; if it is dealt with, it will cause the DVR to absorb active power, causing the DC side voltage to rise and endanger

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