Improvement of Indirect Vector Control Induction Motor Drive Performance under Low Speed Operation using Five-Level Inverter

Abstract

The dynamic performance of vector controlled induction motor drive is poor and peak motor torque decreases under low speed operation. This reduction in torque is due to the non-linearity of voltage to frequency (Hz) during low frequency operation. The non-linearity is caused by stator voltage drop which in turn requires a larger percentage of overall terminal voltage. To overcome these problems multilevel inverter fed induction motor drive is presented in this paper. For two-level and five-level inverter control SVM method is employed. A simplified space vector modulation technique is implemented for five-level inverter in order to reduce the computational difficulties. In this, the space vector diagram of the multilevel inverter is decomposed into six space vector diagrams of two-level inverters. The torque ripple and dynamic performance of induction motor drive are compared under different operating conditions with low speed operation.

Keywords: two-level inverter, five-level inverter, space vector modulation (SVM), indirect vector control, low speed, induction motor drive