Optimal reference voltage saturation for nonlinear current control of synchronous machine drives

Abstract

An optimal reference voltage saturation (ORVS) for nonlinear current control of synchronous machine drives is presented. It is integrated into a nonlinear current control system based on input/output (I/O) linearization and proportional-integral (PI) controllers with anti-windup. The ORVS is derived from an optimization problem that can be solved analytically. The deviation between the desired current dynamics obtained by the proportional-integral (PI) current control system if the voltage constraints were not present and the feasible current dynamics due to the saturated voltage is minimized. Finally, the proposed ORVS is compared to (i) classical (vector-valued) reference voltage saturation and (ii) the absence of any saturation and/or anti-windup. The simulative comparison is done for a highly nonlinear, anisotropic reluctance synchronous machine (RSM) whose parameters and look-up tables were obtained from a real machine. The simulation results show that the proposed ORVS outperforms the other two approaches in terms of current tracking accuracy and faster current dynamics.