직렬형 멀티레벨 인버터를 사용한 무효전력보상장치의 직류전압평형을 위한 새로운 제어기법

A New Control Scheme for Maintaining Balanced DC Voltages in Static Var Compensator(SVC) Using Cascade Multilevel Inverter

This paper examines the application of high voltage static var compensator(SVC) with cascade multilevel inverter which employs H-bridge inverter(HBI). A new switching scheme is developed for the SVC system. To improve the unbalanced problem of the DC capacitor voltages, the rotated switching scheme of fundamental frequency is newly used. The optimized fundamental switching pattern with low switching frequency is adapted to be suitable for high application. The selective harmonic elimination method(SHEM) allows to keep the total harmonic distortion(THD) low in the output voltage of multilevel inverter. The SVC system is modeled using the d-q transform which calculates the instantaneous reactive power. This model is used to design a controller and analyze the SVC system. Simulated and experimental results are also presented and discussed to validate the proposed schemes.