Single-Stage NPC-Type Dual-Port Inverter for Integrated Wind/Battery Hybrid System

Wind power is inherently intermittent and poses challenges to the stable integration of wind turbines (WTs) into a power system. Battery energy storage systems (BESSs) are often used to mitigate wind power fluctuations, charging and discharging batteries depending on wind conditions. Like every multisource system, the WT-BESS hybrid system requires power electronic converters to control the dc and ac power flows. Multiple dc-dc and dc-ac power conversion stages enable high control flexibility, but have a low energy conversion efficiency and require several bulky passive filters. Single-stage multiport inverters (MPIs) that connect multiple sources to the ac grid in a single conversion stage have been increasingly investigated in recent years as a potential alternative. This paper examines the performance of the NPC-type Dual-Port Inverter (DPI) for a wind energy system based on a permanent magnet synchronous generator and battery storage device. The modulation of the DPI and the integrated BESS and WT maximum power point tracking control are presented and discussed. As proved by numerical simulations, the single-stage DPI can inject smooth electrical power into the grid at a unity power factor under highly variable speed conditions while always extracting the maximum power from the turbine.