A cage induction generator using back to back PWM converters for variable speed grid connected wind energy system

A new control scheme of a variable speed grid connected wind energy generation system is presented. The scheme uses a cage induction generator driven by an emulated wind turbine with two back-to-back voltage-fed PWM inverters to interface the generator and the grid. The machine currents are controlled using an indirect vector control technique. The generator torque is controlled to drive the machine to the speed for maximum wind turbine aerodynamic efficiency. The supply side converter currents are also controlled using a vector approach using a reference frame aligned with stator voltage vector. The DC link voltage of the power electronics interface is controlled acting upon the supply active power current component using a nonlinear control and a fuzzy based interpolation of linear PI controllers to improve the disturbance rejection and meet noise considerations in steady state. Experimental validation of the proposed control scheme on an emulated 3.2 kW wind energy system is shown.