Standalone SCIG-based wind energy conversion system using Z-source inverter with energy storage integration

Off-Grid small wind turbines provide a very attractive renewable energy source for remote communities and small businesses. Wind turbines using geared squirrel-cage induction generator are widely accepted due to robustness, simplicity, light weight and low cost. In contrast to commonly-used voltage-sourced inverters, Z-source inverters provide voltage boost and improve inverter reliability. This work develops a variable-speed wind energy conversion system using a squirrel-cage induction generator and a Z-source inverter as the interface with load side. The shoot-through mode of Z - source inverter is used to extract the maximum power from the wind turbine whilst modulation index is adjusted to produce the desired ac voltage at the load bus. A storage battery is integrated with the system through a bidirectional buck-boost DC/DC converter. The battery contributes to maintaining power balance and improvement of power quality by indirect control of the dc-side voltage of the inverter.