Nonlinear optimal control for VSI-fed asynchronous motors

In the article's control approach the nonlinear dynamic model of VSI-IMs undergoes approximate linearization around a temporary operating point which is recomputed at each iteration of the control method. This temporary operating point is defined by the present value of the VSI-fed IM state vector and by the last sampled value of the system's control inputs vector. The linearization relies on Taylor series expansion and on the system's Jacobian matrices. For the approximately linearized model of the VSI-fed IM an H-infinity feedback controller is designed. This controller achieves the solution of the nonlinear optimal control problem for the VSI-fed IM under model uncertainty and external perturbations. For the computation of the controller's feedback gains an algebraic Riccati equation is iteratively solved at each time-step of the control method. The global asymptotic stability properties of the control method are proven through Lyapunov analysis. Finally, to implement state estimation-based control for this system the H-infinity Kalman Filter is proposed as a state observer.