Generalized Cockcroft-Walton Multiplier Voltage Z-Source Inverters

An impedance-source inverter can offer the voltage buck-boost function in a single-stage circuit. Its advantages include a simple structure, safety, and reliability. This article proposes a Cockcroft-Walton multiplier voltage (CWMV) impedance-source inverter consisting of a modified CWMV circuit and an impedance-source inverter. There are two types of circuits: the CWMV Z-source inverter (ZSI) and the CWMV quasi-Z-source inverter (qZSI). In a CWMV qZSI, the input current is continuous, the voltage overshoot across the bridge is small, and the boost capability is great, with the disadvantage is that its passive component count is increased. This article studies the static and dynamic characteristics of the two inverters. The operating modes of the CWMV qZSI is studied, the voltage and current stress of each device are analyzed, the small signal model of the circuit is established, and a proportional-integral-differential controller with good control performance is designed. Compared with existing impedance-source inverters, a CWMV qZSI has obvious advantages in terms of the voltage and current stresses on components, and also in terms of its inductor size, magnetic core volume, and overall efficiency. The theoretical analysis was verified by a 1 kW laboratory prototype. The experimental results were consistent with the theoretical analysis.