Research Of Reactive Power Compensation Method In Medium-low Voltage Unbalanced Distribution Networks

In the medium-low voltage distribution networks, the inductive load and the loadimbalance caused great loss of power, low power factor problem. Especially in the vastrural areas particularly serious. This not only affect the operation efficiency of electricequipment, but also affects the safe operation of equipment. While the traditionalreactive power compensation technology,mostly for the symmetric system, in particularfor the asymmetric three-phase four-wire low-voltage distribution network ofasymmetric compensation of reactive power is very limited.This paper starting from reactive compensation algorithm, using FFT algorithm tocalculate the power, and puts forward a kind of applied both for three-phase three-wireway also applies to three-phase four-wire connection mode imbalance of reactive powercompensation optimization algorithm. Combined with reactive compensation try to onlyuse capacitor, do not use the inductance of the actual situation, in the only know eachphase active power,reactive power circumstances can determine the compensationcapacity. And satisfying the compensation effect, make the premise of reactive powercompensation device capacity to a minimum.Aiming at the disadvantages in the application of reactive power compensationdevice with electromagnetic or power electronic switches for pulling in or out thecapacitor, a reactive power compensation deviec based on the complex switch, whichcan realize grading and fast compensation for eaeh phase using both collectivecompensation and separatc compensation, is developed to switch capacitor. The voltageHad zero conduction and current had zero capacitor is cut off, no inrush current whenthe capacitor switching, no harmonic, low consumption, service life long characteristics.In addition, the paper analyzes the advantages and disadvantages of some currentcontrol method, combining with the practical experience is designed for reactive powercontrol as the basis, the voltage control for auxiliary of the comprehensive fuzzy controlmethod. This is one of the most direct control mode, testing and the quantity controltargets consistent, can both avoid switching oscillation, also can achieve a one-time, to avoid the repeated shots for grid and cut the harmful effects of capacitors.Finally using MATLAB simulation software of the system is simulated, theexperiment proves this compensation system both can compensate for reactive powerand can effectively correction unbalanced three-phase.