Buck-Boost Operation Using a Z-Source Inverter

An impedance-source (or impedance-fed) power converter (abbreviated as Z-source) and its control method for implementing dc-to-ac, ac-to-dc, ac-to-ac, and dc-to-dc power conversion are presented in this paper. This impedance converter employs a unique impedance network (or circuit) to couple the converter main circuit to the power source, hence provides a unique feature that cannot be obtained in the traditional converters where a capacitor and inductor are used, respectively. The Z-source converter overcomes the conceptual and theoretical barriers and limitations of the usual source converter (known as a V-source converter and I-source converter) and provides a novel power conversion concept. The Z-source concept can be applied to all ac-to-ac, dc-to-ac, dc-to-dc, and ac-to-dc power conversion. To describe the control and operating principal, this paper explains an example: a Z-source inverter for dc-ac power conversion needed in fuel cell applications. Experimental results and simulation are presented to demonstrate the new features.