Analysis of DMS-Controlled Three-Phase Single-Stage SEPIC Differential-Mode Grid-Connected Inverter

Analysis and performance of a three-phase single-stage SEPIC differential-mode inverter (DMI) using a discontinuous modulation scheme (DMS) are presented in this paper. Since the DMS was previously suggested in many inverter topologies to reduce the voltage stress of utilized switching devices and enhance inverter efficiency, a simple design process to integrate DMS into the SEPIC DMI is proposed in this work. With this modulation strategy, the discontinuity of the duty cycle for one-third of the entire grid frequency cycle thoroughly minimizes the conduction losses and switching losses into the SEPIC converters. Also, it is noted that the voltage stress is significantly reduced in passive elements as well as switching devices. Furthermore, the compensation of the negative sequence harmonic components is maintained without adding extra sensors. The inverter operation along with mathematical analysis of the DMS and grid current control is presented. A PSIM simulator is used to evaluate the behavior of the proposed modulation strategy. Finally, a comparison with the conventional continuous modulation scheme (CMS) is performed for a better assessment.