A Single-Phase Embedded Z-Source DC-AC Inverter by Symmetric and Asymmetric Voltage Control

In the case of the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DCAC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, equivalent level of AC output voltages can be obtained. Moreover, by controlling asymmetrically the output capacitor voltages, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments are performed under the condition of the DC source 38V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that the efficiency of the proposed inverter can be achieved up to 95% and 97%, respectively, by symmetric and asymmetric control.