High frequency transformer isolated Z-source inverters

This paper presents a family of high frequency transformer isolated impedance-source (Z-source) inverters and corresponding control method for DC to AC power conversion applications. The original single-stage Z-source inverter incorporates a unique passive impedance network coupled between the inverter main circuit and power source, thus overcoming some conceptual limitations of conventional voltage-fed and current-fed inverters. The proposed isolated Z-source inverters carefully integrate the Z-source network concept into the two-stage DC-DC-AC topology, by employing high frequency transformers. While inheriting the great merits of original Z-source inverters, such as wide input range, buck and boost functions, and high reliability against EMI noises, the proposed topologies can achieve input-output isolation and higher voltage boost ratio with reduced device stresses, with transformer secondary to primary turns ratio over 1. This paper concentrates on one example of a voltage-fed isolated Z-source inverter to elaborate the detailed operating principle and control. Simulation and experimental results are presented to verify the analysis and demonstrate the new features.