Control system for vertical-axis WECS

This paper introduce the design of a static converter for a vertical-axis wind energy conversion system (WECS), based on permanent magnet generators. This turbine presents low speed and high torque, characteristics that will be explored in the converter project. The proposed topology, formed by a high frequency semi-controlled rectifier and a step-down dc-dc converter, realizes the turbine´s maximum power point tracking (MPPT) and protects battery from surge and over current. The principal advantages of using the semi-controlled rectifier are: simplicity, since all active switches are connected to a common point, robustness, as short-circuit through a leg is impossible to happen and high efficiency due to reduced number of elements. One disadvantage is the high total harmonic distortion (THD) produced; nevertheless, its value is in an acceptable range. A system overview, the vertical-axis wind turbine characteristics, the power generator, the power converter and control system are presented. Simulation results are compared with experimental results from a 1.5 kW laboratory prototype.