Analysis and simulation of a wind-electric battery charging system

A small commercial wind-electric battery-charging system based on a three-bladed rotor has been analysed in a detailed fashion. The system consists of a synchronous generator with permanent magnets, a six-pulse rectifier and a battery bank with charge controller. A steady-state power curve is predicted based on the electric characteristics found experimentally and the aerodynamic performance of the rotor simulated with a version of blade element momentum (BEM) theory developed in our group. The BEM code has been designed to account for variable Reynolds numbers at different blade sections and stall conditions. The findings are compared with the manufacturer's specifications, and a detailed discussion is provided. A very good agreement with the steady-state power curve given by the manufacturer has been obtained after accounting for different sources of power losses, such as voltage drops in the rectifier, Joule heating in the power cables and losses in the generator's core. The system is found to operate near the aerodynamic optimum for all wind speeds studied, whereas electrical losses are significant near rated power. Some recommendations for improving the system performance are provided. Copyright © 2005 John Wiley & Sons, Ltd.