Research On High-Voltage Static Var Generator

With the expectations on power supply quality rising, new technologies likeFlexible AC Transmission Systems (FACTS) have developed rapidly, thanks to itseffectiveness in power quality improvement. As a new and synthetic technology,FACTS is the application of power electronics technology, microprocessortechnology, control technology and other high tech in high voltage transmission anddistribution systems, so as to improve the reliability, controllability, performance andpower quality of the systems, while saving huge amounts of energy. Due to itsstate-of-the-art control qualities and good compensation effect, static var generator(SVG) has become the hot spot in developing FACTS devices. This paper mainlyconsists of following parts:(1) Currently, three-phase bridge inverter, which has disadvantages of highoutput voltage THD, low voltage and power level, difficult to implementationindividual control, and so on, is mostly used as the main circuit of SVG. In view ofthe disadvantages of three phase inverter, by comparing the pros and cons ofhigh-voltage high-power main circuit topology structures, this article select theappropriate one topology structure of high voltage SVG device, and apply cascadedmulti-level inverter to SVG. The most suitable PWM control method for the inverterin the cascade multi-level SVG was selected.(2) DC capacitor voltage balance is a particular problem faced by the cascademulti-level inverter, it affects the compensation performance and safe operation of thedevice. This paper analyze the mechanism of DC capacitor voltage unbalance, basedon voltage and current double closed-loop control strategy, the paper put forwardthe DC voltage balance control method. And the feasibility of the control strategy isverified by simulation.(3) Then the cascaded multi-level SVG device design method was elaborated,which include hardware design, software design and analysis of experimental results,and a summary of some of the key technologies. Experimental results show that thesystem is able to achieve high equivalent switching frequency when running at lowerswitching frequency, which has good output harmonic characteristics, and has a goodability to regulate reactive, good static and dynamic response characteristics, fasttracking speed. Based on the reactive power compensation device applied in high-voltagesituations, this paper studies the topology structure and control technology ofhigh-voltage SVG, and researches the manufacture of cascade multi-level SVG device,include the specific programs of some key technology. The contents of this paper canprovide reference for the development of high-voltage SVG.