Experimental Vertical Axis Wind Turbine System

Abstract: Vertical axis wind turbines may have mechanical advantages compared to conventional horizontal axis wind turbines, which make vertical turbines interesting to study. A 12 kW straight-bladed Darrieus turbine has been designed and constructed by the Division of Electricity at Uppsala University. The aim of the project was to build a small scale model of a turbine that was system optimized, not optimized part by part. The constructed turbine has no mechanical control systems such as blade pitching; it is instead regulated electrically by power electronics connected to the generator. A control system has been built that can run the turbine at constant optimum tip speed ratio. To start the turbine a simple robust electrical starter has been developed. It consists of a six-step modulated inverter which is feedback-controlled from the generator rotor position. The power coefficient as a function of the tip speed ratio was determined during a long measurement campaign performed in spring 2009. The top power coefficient was measured to 0.29 at a tip speed ratio of 3.3.