A Suitable Load Control Method for Constant Tip Speed Ratio Operation of Stand-alone Wind Turbine-Generator Systems (Part 1: Evaluation of Power Generation Capability and Output Fluctuation)

Abstract

A suitable load control method for a constant tip speed ratio operation of stand-alone systems using vertical axis wind turbines with a self-starting capability is discussed from the viewpoint of its power generation capability and output fluctuations. This study takes up a stand-alone system with a straight-wing-type turbine, which is mainly operated at a constant tip speed ratio. Two types of load control methods are considered: Method-1 wherein the load torque is controlled in proportion to the square of the rotational speed and Method-2 that adopts a feedback control of the rotational speed in response to the inflow wind speed. The computational results using the dynamic simulation model show that the decrease in the output fluctuations from Method-1 to Method-2 is much larger than the increase in the power generation capability from Method-2 to Method-1. Therefore, it is concluded that Method-1 is the suitable load control method.