Pulse-width modulation of Z-source inverters

Z-Source inverters have recently been proposed as an alternative power conversion concept as they have both voltage buck and boost capabilities. These inverters use a unique impedance network, coupled between the power source and converter circuit, to provide both voltage buck and boost properties, which cannot be achieved with conventional voltage-source and current-source inverters. To facilitate understanding of Z-source inverter modulation, this paper presents a detailed analysis, showing how various conventional pulse-width modulation strategies can be modified to switch a voltage-type Z-source inverter either continuously or discontinuously, while retaining all the unique harmonic performance features of these conventional modulation strategies. The paper starts by analyzing the modulation requirements of a single-phase H-bridge Z-source inverter, and subsequently extends the analysis to cover the more complex three-phase-leg and four-phase-leg Z-source inverters, with carrier-based implementation reference equations derived for all the inverters. The theoretical and modulation concepts presented have been verified both in simulation and experimentally.