High-Gain Modular Three-Phase Hybrid Boost Rectifier for Small Wind Energy Harvesting System

Abstract

The use of small wind turbines for distributed generation has increased due to the pursuit of renewable and clean energy systems. Small wind turbines usually have low output voltage, therefore a conversion system is necessary to increase the voltage value in order to deliver the harvested energy to the commercial grid. This paper proposes a modular three-phase hybrid boost rectifier topology as the input stage for a wind energy conversion system (WECS). The proposed rectifier is a three-phase variation of the hybrid boost rectifier, which uses a ladder switched-capacitor cell to multiply its output voltage gain by an integer conversion ratio. The system is supplied by a small wind turbine with an open-end winding permanent magnet synchronous generator (PMSG), thus the use of a modular topology is possible and the converter can control the phase currents individually. The system is controlled by a maximum power point tracker (MPPT) that generates a peak current reference for the rectifier, which controls the input current of each phase to obtain a unity power factor. The output dc-link voltage is controlled by an inverter that delivers the extracted energy to the grid. An averaged equivalent circuit is proposed to improve simulation time and to obtain reduced order transfer functions. Theoretical analysis and simulations of a system with three-phase 84 V input, 220 V output phase voltages and 6.5 kVA rated power are presented.