Single-Phase Isolated Impedance-Source Inverters

This paper presents a new class of impedance source inverters which offers high frequency isolation between the inverter bridge and the load. Conventional Z-source inverter which employs a impedance network consisting of inductors and capacitors have unique features which can be realized as both buck and boost functions without the need of dead time and overlap time, that cannot be achieved by traditional voltage-fed and current-fed inverters. This paper extends this novel concept by using electrical isolation in impedance source inverters. High frequency isolation itself have limitless advantages in terms of safety, reliability etc. when applied with impedance source inverter makes it a preferable choice for industrial applications. In PV systems a dc circulating current emerges and flows into grid which damages the whole system, electrical isolation prevents the injection of this dc current into the grid. Moreover the gain of the proposed inverter can also be adjusted by varying the turns ratio of the high frequency transformer giving more freedom in utilizing a higher modulation index, results in increased efficiency in terms of waveform quality, improved power factor, lower component voltage stress etc. An experimental prototype is constructed to validate the working operation of the proposed inverter.