I. INTRODUCTION
Z-source inverters are new single-stage electronic power converters with both voltage-buck and boost capabilities that have been proposed for use in fuel cell energy conversion systems [1] and motor drives with a front-end diode rectifier [2], [3]. Compared with traditional voltage-source (VS) and current-source (CS) inverters, the sole difference of a Z-source inverter is its X-shaped impedance network implemented using a splitinductor ( and ) and capacitors ( and ), and connected between the input power source and inverter circuit, as shown in Fig. 1 for a VS-type Z-source inverter. (VS-type inverter is chosen for study in this paper because it is generally more established and can conveniently be constructed using low-cost, high-performance insulated gate bipolar transistor (IGBT) modules or intelligent power modules). This unique impedance network allows both switches within the same phase-leg (e.g. S1 and S4 in Fig. 1) to be turned ON simultaneously to introduce a shoot-through (dc bus short-circuiting) state for boosting the inverter output voltage (similar in theory to that of a dc-dc boost converter). As reported in [4], multiple shoot-through states can conveniently be introduced to traditional continuous and discontinuous pulse-width modulation (PWM) strategies for controlling a Z-source inverter with all steady-state performance merits of these PWM strategies retained.