Control and performance identification for small vertical axis wind turbines

This paper presents the controller design and a simple method to identify the aerodynamic performance for an installed vertical axis wind turbine (VAWT). The hardware realization of the wind energy conversion system consists of a 1.5kW VAWT-driven permanent magnet synchronous generator (PMSG), a PWM rectifier and a grid-tied PWM inverter. The PWM inverter is mandatory to maintain the dc capacitor voltage mainly adapted for operating in parallel with the power grid. The PWM rectifier, serving as a speed governor, is employed to modulate the revolution speed of the VAWT according to the desired power-speed curve so as to extract maximum power from the wind. To guarantee the aerodynamic performance of the VAWT, a simple method, based on the long-term recorded energy efficiency, can determine the optimum power-speed curve for the VAWT. The effectiveness of the proposed strategy is assessed experimentally by examining the closed-loop system response to various wind speeds.