Mitigation of Circulating Current in Diode clamped MLI fed Induction Motor Drive Using Carrier Shifting PWM Techniques

Abstract

Reduction in circulating current is one of the major considerations in inverter-fed electrical drives. Diode-clamped MLI (DC-MLI) enables higher output current per phase, thereby rating of the drive gets increased effectiveness. Various methods of triggering in the inverter legs create a better voltage profile and lead to the enabling of circulating current in the drive system. The induced circulating current (CC) flows through the apparatus neutral (N), and supply ground (G) is caused by the existence of parasitic capacitance. This circulating current may cause potential danger, especially when parasitic capacitance poses large. In the past, different modulation techniques and conversion topologies have been introduced to minimize the flow of circulating current. However, these techniques lead to complexity, high cost, low voltage profile, and efficiency due to lower modulation parameters. This paper proposes PS, POD, PD carrier shifting PWM algorithms for DC-MLI to tumbling the CC. The performances of the proposed algorithm, in terms of CC, THD, losses, and efficiencies are analyzed theoretically and are validated via simulation and experimental results.