Discrete boundary layer current control for VSI-IM drive

Abstract

This paper discusses the time-discrete switched variable structure field oriented current control of an IM (induction motor) drive. VSI (voltage source inverter) is directly controlled, exploiting boundary layers and quantized field rotation velocity for addressing the switching table. In current control design, the fact that the calculation of the stator voltage vectors from the d-q control components does not have a unique solution is exploited. This is considered as design freedom, which is further extended by introduction of preassigned-order switching according to the time scale separation of magnetization and the generation of torque currents. Boundary layers with different reaching dynamics introduce motor stator zero voltage, which is selected by finite automaton from nearest VSI state.