LMI Based Digital State Feedback Controller for a Wound Rotor Induction Drive with Guaranteed Closed Loop Stability

In this write-up, a novel approach for the design of a digital state feedback controller for the speed control of slip energy recovery system employing a wound rotor induction machine is proposed using digital redesign approach. The state feedback controllers for digital implementation are suitably redesigned in such a way that the discrete-time-system response and continuous-time response match at all sampling instants. As the digital implementation of the continuous time controller is very desirable when the designed continuous-time controller uses some recent and advanced control algorithms, the redesign problem boils down to an optimization problem minimizing the difference between the continuous-time system and discrete-time system subjected to some constraints. In this paper, the redesign problem is formulated as a generalized eigenvalue problem with linear matrix inequality constraints. The results obtained are compared with other methods. The proposed algorithm uses LQR approaches for the design of continuous-time controller and the approach is illustrated for slip energy recovery system with encouraging results.