Study On Low-voltage Static Var Generator

In electric power system, the harm to system for insufficient reactive power is not allowingneglect. There are many methods to control reactive power in electric power system, includingadopts synchronous compensator, shunt capacitor, static vat compensation(SVC) device and staticvar generator(SVG). Synchronous compensator as the typical representation of earlier reactivepower compensation device has the advantage of phase modulation, but the speed of dynamicresponse is slow, generate unit reactive power it has more active consumption, circulate andmaintenance are complex, not adapting the quickly change of all kinds nonlinear load. Shuntcapacitor compensation is simple and economic, but it can not follow the change of inductive loadin system, it can not achieve dynamic compensation of reactive power. SVC can carry throughreactive power compensation according to the condition of reactive power in power network, but inactual application, SVC can not work without big capacity energy storage element which has timedelay, it can not achieve instantaneous reactive power control. Compared with SVC, the speed ofSVG response faster, not only can act as reactive power supply but also can act as reactive powerload, generate few high- order harmonic, the range of regulate is wider, consumption and noise aresmall. Different from the SVG which applies in high voltage system, this paper study a static vargenerator which applies in low voltage distribution system.This paper carries through deepgoing systemic analysis about reactive power compensationtechnology, main circuit of SVG simulation system, hardware circuit of control system, software isdesigned and laboratory simulation system is made. In order to insure the accuracy of parameterand control strategy, computer simulate test is carried to key taches. To verify the function of thesystem, laboratory simulation system is made, after simulated experiment, it proves the system hasthe character that following the change of load character it can output reactive power automatically.In order to adapt the rural electricity system which has the character load fluctuate frequentand the range of fluctuate is large, this paper apply instantaneous reactive power theory to detectreactive current of the system, this method enhance the speed of detection, at the same time, it canassure the detection precision when the load of rural electricity system is dissymmetric. Though thesystemic research to the control method of SVG, adopting current direct control mode, enhancingthe speed of response and the precision of control of the system.The simulation system adopts PM15RSH120 intelligent power module (IPM) as the switch ofinverter which from company MITSUBISHI, the IPM interior integrates logic, control, detection and protect circuit, it is convenient to use, it not only reduce the volume of the system and theempolder time, but also increase the reliability of the system; The system adopts TMS320LF2407DSP evaluation board as main controller which from company TI, it overcomes the deficiency oftraditional single chip microcomputer which has low calculate speed and poor precision; using thetechnology of sinusoidal pulse-width modulation combine power module drive, protect, signalprocess, power supply etc. It can achieve signal collection, processing, system protection of staticvar generator and dynamic compensation of reactive power. The experiment result shows thesimulation system can achieve the expectant compensation effect.