Transition and Post-fault Correction Strategy for a Single-Phase Inverter With Improved Redundant Leg Utilization

Single-phase inverters are frequently employed in several applications with redundant switches, legs, or modules in the circuit. In this article, a transition scheme is developed which uses a redundant leg to achieve two distinct goals namely ripple compensation and fault tolerance in the inverter unit. To account for the second-harmonic ripple (SHR) using a redundant leg, a prefault control technique is created which ensures 0% to 100% compensation of the SHR in the dc-link current, minimizing the stress on the dc-link capacitor. On occurrence of a fault, the transition scheme securely switches the inverter operation from the prefault condition (ripple compensation mode) to the postfault correction (fault-tolerant mode) in the preparation stage using the same redundant leg. The inclusion of connecting devices and the modifications on the ac side filter are competent with the prefault and the postfault condition. The proposed transition and the correction scheme are tested on a single-phase inverter for different fault conditions.