Low cost single-phase semi-Z-source inverter

This paper presents several single-phase non-isolated semi-Z-source inverters for small distributed power generator in grid-connected applications with low cost and doubly grounded features. These semi-Z-source inverters employ the Z-source/quasi-Z-source network and only two active switches to achieve the same output voltage as the traditional voltage-fed full-bridge inverter. The two active switches of the semi-Z-source inverter are controlled complementarily. Different from the traditional single-phase Z-source/quasi-Z-source inverter, shoot-through zero state is not applicable for the semi-Z-source inverter. The input dc source and the output ac voltage of the semi-Z-source inverter share the same ground, thus leading to less leakage ground current advantages over other non-doubly grounded inverters, such as voltage fed full-bridge inverter. This is a preferred feature for non-isolated grid-connected inverters especially in photovoltaic application. A revised non-linear sinusoid pulse width modulation method for semi-Z-source inverter is also proposed. By using this method, desired duty cycle can be generated to output the sinusoidal voltage. Other dc-dc converters with similar voltage gain curve, which can also be used as a single-phase inverter are also discussed and summarized. A single-phase semi-Z-source inverter prototype is built, experimental results are provided to verify and demonstrate the special features of the proposed circuit.