Influence of Load Level on Performance of Stand-alone Vertical Axis Wind Turbine System

The influence of load level on the performance of a stand-alone, straight-wing, vertical axis wind turbine system in terms of its power generation capability and output fluctuation during operation is numerically investigated using a dynamic simulation model. The system is mainly operated at a constant tip-speed ratio, i.e., at a maximum power coefficient point, by load control in proportion to the square of rotational speed. Thus, the steady-state performance and dynamic behavior of the system under four load levels are analyzed. Then, the dynamic system performance under different load levels is discussed. This work shows that, under high mean wind speed conditions, a low load level is undesirable because it would cause an increase in the output fluctuation. However, under low mean wind speed conditions, a low load level could be effective in improving the power generation capability, with only a slight increase in the output fluctuation.