Modern robust control of a CSI-fed induction motor drive system

The current source inverter (CSI)-fed induction motor (IM) drive system is an open loop stable system, however due to model uncertainties and operation at different operating points the system exhibits poor performance and may lose stability. This paper utilizes the H_∞ loop shaping design procedure (LSDP) with μ-analysis (μLSDP) to design a controller for a CSI-fed induction motor drive system in order to achieve robust stability and robust performance against various model uncertainties. First, the nonlinear dynamic equations of the CSI-fed IM are described in state space form, with emphasis on modeling errors (uncertainties), physical disturbances and noises, then these equations are linearized around an operating point. Second, the H_∞ LSDP with μ-analysis procedure is explained. Third, the H_∞ LSDP problem formulation is presented with emphasis on the selection of the frequency shaping functions which reflects the robust stability and performance goals. Finally, the μLSDP is applied to the controller design of an example system, and numerous simulation results are presented. The results showed that both robust stability and robust performance are achieved