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This paper presents a single-phase to three-phase adjustable-speed drive (ASD) system, which consists of a diode rectifier and a single-stage boost inverter without electrolytic capacitors (E-caps). The system has no shoot-through issues and gains high reliability due to the shoot-through zero-state regulation method. By using electrolytic capacitors-less topology, the lifetime can be greatly increased. By properly designing the tapping position of the inductor, the system has a high boost-inversion gain and can ride through grid voltage sags. By using the proposed harmonic injection method, the system can realize high input power factor and small dc-link ripple voltage, simultaneously. Experimental results of the electrolytic capacitors-less single-stage boost inverter (E-caps-less SSBI) based single-phase to three-phase ASD system are obtained to verify the actual performances. [ABSTRACT FROM AUTHOR]

This letter presents a modulation technique for the modified coupled-inductor single-stage boost inverter (CL-SSBI)-based grid-connected photovoltaic (PV) system. This technique can reduce the system leakage current in a great deal and can meet the VDE0126-1-1 standard. To maintain the advantages of the impedance network, only a diode is added in the front of the original topology, to block the leakage current loop during the active vectors and open-zero vectors. On the other hand, the near-state pulse width modulation (NSPWM) technique is applied with one-leg shoot-through zero vectors in order to reduce the leakage current through the conduction path in the duration of changing from and to open-zero vectors. Simultaneously, the leakage current caused by other transitions can also be reduced due to the fact that the magnitude of common-mode voltages is reduced. Simulation results of the transformerless PV system are presented in two cases: modified CL-SSBI modulated by maximum constant boost (MCB) control method and NSPWM. Experimental results for both CL-SSBI topology modulated by the MCB control method and modified CL-SSBI topology modulated by NSPWM are also obtained to verify the accurateness of theoretical and simulation models. [ABSTRACT FROM AUTHOR]