Design, Operation, and Control of S3 Inverter for Single-Phase Microgrid Applications

A single-phase voltage source inverter with a front-end dc-dc conversion stage followed by a synchronized push-pull configuration operating at a desired fundamental frequency (FF) is presented. The duty cycle of the dc-dc conversion stage is varied in the form of a unidirectional sine wave to produce a similar output voltage across the dc-link capacitor. The unidirectional voltage is made into an alternating voltage by the synchronized push-pull configuration. This inverter employs three semiconductor switches, in which one is operating at a high frequency and the rest are operating at an FF. Hence, it is named as the S3 inverter. Furthermore, simple and cost-effective analog circuits are presented for the generation of switching pulses and the control of the amount of power fed to the grid. The hardware prototype of the S3 inverter has been built in a laboratory, and its performance during the stand-alone and grid-connected modes of operation is validated.