A Current-Sharing Driving Method for Multilevel Current Reinjection Converter

Multilevel current reinjection (MLCR) converter has unique advantages over a pulsewidth modulation (PWM) converter in terms of capacity, efficiency, and harmonics, which leads to promising potential in the high voltage direct current transmission application. The imbalance of injection currents is a particularly critical problem that affects the input current harmonics and operation reliability of an MLCR converter. To cope with this problem, the state model of injection circuit is developed, and the decisive factor of its current-sharing performance is analyzed. Based on it, a current-sharing driving method for injection circuit is proposed by applying a phase-shift equal method to the basic switching function of injection switches. Simulation and experimental results show that the current-sharing performance of injection circuit is improved and the input current harmonics are reduced.