Interleaved PWM with Discontinuous Space-Vector Modulation

This paper describes the effect of interleaved discontinuous space-vector modulation (SVM) in paralleled threephase systems using three-phase pulsewidth modulation (PWM) rectifiers as an example. At the discontinuous point of the SVM, the phase shift between the switching signals of the paralleled modules generates a zero-sequence excitation to the system. Because the conventional control in a balanced three-phase system with only dq channels cannot reject this disturbance, a beatfrequency circulating current will develop on the zero axis. Based on this observation, a SVM without using zero vectors is used to eliminate the cause of pure zero-sequence current for parallel operation. Using this SVM, the circulating current is observable in dq channels. It can be suppressed dynamically by strong current loops of power-factor-correction (PFC) circuits. The concept is verified experimentally on a breadboard system.