DC-Bus Capacitor Sizing in the Back-to-Back Converter

Renewable energy sources as wind power and hydropower plants are growing due to reducing environmental pollution. As the airspeed and river flow varies, it is advantageous to change a speed of the generator. For this purpose, it is necessary to use a back-to-back converter, which provides changing of both voltage and frequency. Optimizing the converter is an aim of this paper, namely regulating the converter to minimize ripple current to DC-link capacitor. This capacitor is huge and expensive part of the converter. Through appropriate controlling of the converter, it is possible to minimize the ripple current, thus to minimize the capacitor. Methods to control the converter are presented in this paper and simulated to determine the ripple current. Finally, the methods are compared, and the size of the capacitor is established.