High-Efficiency Flux Reference of Direct Torque Controlled Induction Machine

When a direct torque control (DTC) of an induction motor drive is operated below its rated torque, the stator flux reference has to be set to an optimised value (which is below its rated) in order to minimise the losses thus optimised its energy usage. The optimal flux will be calculated once the steady-state speed is reached and normally it will take some time before the new optimal flux is obtained. In this paper, an almost-optimal stator flux for a DTC induction motor drive under light-loaded condition is calculated instantaneously. The high-efficiency flux reference (HEFR) scheme calculates the value of the stator flux reference, which is almost equal to the optimal flux reference, without having to wait for the steady-state condition. The proposed method aims to conserve the simple control structure of DTC drive system. The effectiveness of the proposed method is studied through MATLAB's simulation package.