Realization of a high-dynamic discrete-time controller for PWM inverter-fed induction motor drives

This paper describes a controller of a PWM inverter-fed induction motor drive based on the well known principle of rotor flux orientation. A new aspect is the homogeneous discrete-time design of the complete control structure including measurement data acquisition and pulse width modulation. A discrete-time flux observer ensures accurate flux orientation even at standstill and additionally supplies one-step-ahead predicted current estimates, which compensates for computational delay. By these discrete-time considerations computing power can be saved whereas optimal control performance can be reached. The controller has been successfully proved in several drives up to a power of 960 kW. In all operation modes the control characteristics are comparable with those of DC drives