A Modified Three phase Current Source Inverter for Modular Photovoltaic Applications

Abstract

This paper proposes a circuit topology of a single-stage three-phase current-source photovoltaic (PV) gridconnected inverter with high voltage transmission ratio (VTR). Also, an improved zone sinusoidal pulse width modulation (SPWM) control strategy and an activeclamped sub circuit that can suppress the energy storage switch's turn-off voltage spike are introduced. The circuit topology, control strategy, steady principle characteristics, and high-frequency switching process are analyzed profoundly, as well as the VTR's expression and design criterion of the centertapped energy storage inductor. The improved zone SPWM control strategy consists of two control loops, namely, the outer loop of input dc voltage of PV cells with the maximum power point tracking and the inner loop of the energy storage inductor current. The experimental results of a 3-kW 96VDC/380V50Hz3φAC prototype have shown that this kind of a three-phase inverter has the excellent performances such as singlestage power conversion, high VTR and power density, and high conversion efficiency. Nonetheless, it has small energy storage inductor and output CLfilter, low output current total harmonic distortion, and flexible voltage configuration of the PV cells. This study provides an effective design method for single-stage three-phase inverting with high VTR. Index Terms-Current source, high voltage transmission ratio (VTR), photovoltaic (PV) grid-connected inverter, three-phase,zone Sinusoidal Pulse width modulation (SPWM) control strategy.