Stabilization of an Induction Motor Drive

In a companion paper (Part I), we investigated stability of induction motor drives, with resonant input filters. By using a linearized feedback model of the drive, it was shown how stability specifications could be transformed into constraints on the input admittance of the voltage source inverter. The stabilization problem then becomes a standard feedback control loop-shaping problem, where the Nyquist curve of the inverter input admittance should satisfy certain constraints. In this paper (Part II), we design and analyze controllers to meet such specifications. This approach covers both field-oriented control as well as direct torque control. First, a general expression for the controllers in terms of the desired inverter input admittance is derived. Then we propose an explicit stabilization controller, which is easy to implement, while still providing a good compromise between robustness, damping of the DC-link and acceptable torque control. The performance of the proposed stabilization controller is verified through experiments with a hardware-in-the-loop simulator.