A multilevel inverter fed direct torque control strategy for an induction motor using pi controllers

Abstract

This paper presents a multilevel inverter fed direct torque control scheme for an open-end winding configured induction motor drive. Unlike the hysteresis controller based direct torque control strategy, the control scheme comprising of the torque and flux control by rotating reference frame quadrature-axis and direct-axis voltage components respectively. Here, Proportional Integral controllers are used for the generation of these voltage components. In the modulation part, a fractal based space vector direct torque control algorithm is used for sector identification and determination of associated switching vectors. Moreover, the algorithm incorporates a computationally efficient 60 0 coordinate system for representing the space vectors instead of the conventional Cartesian coordinate system. The speed reversal, steady-state and dynamic performance of the scheme is thoroughly analyzed under loading conditions. The multilevel inverter drive is implemented on an open-end winding type induction motor. A six level inverter fed direct torque controlled drive was designed and implemented by using a 2 Hp induction motor. The loading performance of the scheme is tested on a mechanical load with a 5Hp induction motor. All the experimental waveforms were captured under closed loop mode and the results are presented to validate the scheme.