Current ripple reduction to improve electromagnetic torque and flux characteristics in AC drives

Abstract

ABSTRACT In this paper, an improved hysteresis-switching table-based current regulation for the field-oriented control (FOC) drive is designed. The control structure of the proposed scheme is similar to the direct torque control (DTC) scheme; therefore, it is named as the hybrid torque and flux control (HTFC) scheme. Conventional HTFC strategy suffers from high current ripple, due to its inefficiency in the selection of optimised switching voltage vectors from the switching table, while limiting d- and q-axes current errors within the hysteresis bands. This is because of the restricted availability of voltage vectors for two-level inverter drive control. To overcome the above problems, the switching table of the HTFC scheme is modified to incorporate intermediate voltage vectors, based on (a) rate of change in q-axis current error, (b) the four-level hysteresis controller state of the q-axis current error, and (c) the two-level hysteresis controller state of the d-axis current error. This proposed Mutated Switching Table – HTFC (MST-HTFC) scheme intends to increase the controllability over stator current component errors, and thus limiting the current ripple. The effectiveness of the MST-HTFC scheme over the HTFC scheme is verified using a 1 kW induction motor drive in simulation through MATLAB and validated experimentally.