Predictive Torque Control of Induction Machines using Immediate Flux Control

In this paper a new concept for control of induction machines by generating the torque at the end of the sampling interval, is presented. The method uses the predictive algorithm and can be split into two parts. The purpose of the first part (PTC - predictive torque control) is to predict the reference flux vector corresponding to the reference torque. The aim of the second part is the optimal tracking of the reference flux by selecting either an active or a zero voltage vector. This method, called immediate flux control (IFC), has already been presented by the authors. There are two possible variants of IFC. The characteristic of the first variant is the selection between an active and zero voltage space vectors to be impressed throughout the entire sampling interval. The minimal flux error is obtained following a simple and fast algorithm. As a consequence, the switching frequency becomes very low, but current and torque ripple are considerable. The second IFC variant enables more accurate flux generation by applying an active vector throughout a calculated time interval within a sampling interval, thus requiring higher switching frequency. Both IFC variants together with PTC require minimal processing time. The method has been tested on a 3 kW induction machine laboratory model controlled by DSP. The experimental results confirm the validity of the approach