Low switching frequency space vector modulators for high power multimodule converters

Force-commutated multiconverter systems have been proposed and recently implemented for high power applications, particularly high-voltage direct current (HVDC) transmission and flexible ac transmission systems (FACTS) devices, including STAtic var COMpensators (STATCOM). This paper demonstrates that pulse-width modulation (PWM) based on space vector modulation (SVM), and using low switching frequencies (a few hundred Hertz) can be implemented in multimodule power converter systems. The proposed scheme is based on a delayed sampling technique and allows output voltage control and minimization of harmonic components. Pattern generation options are analyzed and system waveforms are presented for different switching frequencies and number of modules. Results are validated by simulation and confirmed by experiments on a 5-kVA prototype unit.