Your concerned subject is similar to wind turbine generator as you can see in following figure. An optimum wind power generation system with a cage-type machine and two-sided PWM voltage-fed converter is shown in figure below. The machine excitation is supplied by the PWM rectifier, where the excitation current ids maintains the flux constant. Currents ids and iqs are controlled by vector control within the speed control loop, and the speed is programmed with the wind velocity Vw to extract the maximum output power. This means that the optimum operating speeds are ?r1, ?r2, ?r3, and ?r4 for wind velocities Vw1, Vw2, Vw3, and Vw4, respectively, as shown in the figure. Of course, the wind velocity requires monitoring for the control. The line-side converter is responsible to maintain the dc link voltage Vd constant as shown. The line phase voltage waves va, vb, and vc are sensed, and the corresponding co-phasal line current commands ia*, ib*, ic* are generated by multiplying them by the output of the Vd control loop as shown. The phase currents are then controlled by HB PWM current control. When the turbine output power tends to increase the dc link voltage, the line currents tend to increase so that a balance is maintained between the line output power and turbine power. 