Comparisons of controller performance for small-scale verti-cal axis wind turbines

Small-scale vertical axis wind turbines (VAWTs) are attractive for portable power generation. Controller performance is very important in rapidly varying gusty winds commonly observed in urban and rural areas. In this paper, a hill-climb searching (HSC) maximum power point tracking (MPPT), an energy-maximizing model predictive control (MPC) and a simple nonlinear control (SNC) as an MPC surrogate are presented. The control algorithms are tested through a software-only electromechanical model and with hardware-in-the loop test-bed that includes electromechanical and power electronics components. Effects of power coefficient oscillations on dynamic performance are investigated. Results show that proposed controllers perform satisfactorily for wind gust and real wind profiles; the SNC serves as a viable surrogate for the MPC; the model-free, wind speed sensorless MPPT is favorable for small-scale applications; and power coefficient oscillations do not have a significant impact on the dynamic performance of the controllers.