Control device and method for three-phase unbalance and reactive power compensation

Abstract

The invention provides a control device and a method for three-phase unbalance and reactive power compensation. The control device comprises a three-phase switch control circuit, a filter module and a current sampling module, wherein the three-phase switch control circuit is connected to the power grid via the filter module; the three-phase switch control circuit and the filter module are connected onto A, B, C of a three-phase load and an N wire; and the three-phase output current of the three-phase load is respectively connected onto the filter module via the current sampling module. The three-phase output current is controlled through a loop of the three-phase switch control circuit, the sizes of each negative-sequence component instantaneous value and each zero-sequence component instantaneous value separated from the outputted three-phase inductor current are the same as those separated by the A, B, C three-phase output current at the three-phase load side but the directions are opposite, A, B, C three phases of current of the power grid are balanced, and the purposes of quick response, accurate three-phase unbalanced current dynamic compensation and reactive power compensation are realized.

Description

technical field [0001] The invention relates to a three-phase control device, in particular to a control device for three-phase unbalance and reactive power compensation, and to a control method using the control device for three-phase unbalance and reactive power compensation. Background technique [0002] A large number of three-phase four-wire wiring methods are used in urban and rural distribution networks. With the continuous improvement of people's living standards, the power load structure in the power system has undergone major changes. The types of residential electrical equipment increase, and the power consumption increases accordingly. There are many single-phase and three-phase loads, which makes the three-phase unbalance problem in the distribution network field more and more prominent, which leads to increasingly serious power quality problems in the power grid. In some areas, the current unbalance degree of the low-voltage side of the station substation excee...

AI Technical Summary

Problems solved by technology

[0003] However, the capacitance and inductance switching devices involved in the traditional technology cannot quickly compensate for reactive power, the compensation accuracy cannot be guaranteed, and the imbalance of three-phase active power (current) cannot be effectively adjusted; the imbalance degree still exceeds 5% after current imbalance adjustment , cannot meet the compensation accuracy requirements, and the adjustment ability is limited

[0004] SVG (Static Var Generator) is mainly used to compensate reactive power. It is mostly used in three-phase three-wire high-voltage systems without a neutral wire. Because it does not have a neutral wire, it cannot compensate zero-sequence current and cannot adjust the imbalance of reactive power.

APF (active filter) can only compensate the harmonics of the current, but cannot compensate the zero-sequence current, and has limited ability to compensate for the imbalance of three-phase active power

[0005] In addition, schemes such as three-phase four-leg can compensate zero-sequence current, but the efficiency is low and the cost is increased

That is to say, the shortcomings of the existing technology mainly include: it is mostly used in the three-phase three-wire system, and the zero line current of the three-phase four-wire system cannot be suppressed; the topology is complex, and the use of three-phase four-arm solutions increases the cost; The switching devices are used at the same time, and the current contains low-order harmonics such as 3, 5, 7, 9 and 11, which cause resonance; the reactive power and current imbalance cannot be compensated by one device, the time required for compensation is long, and the compensation accuracy cannot meet the requirements. Require

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