Abstract

A novel direct power control (DPC) scheme, with virtual flux orientation based on the grid voltages, has been implemented for an induction motor drive (IMD) fed by an active front end converter (AFEC). The inverter considered here is a multilevel inverter controlled by predictive torque control (PTC). Estimation of instantaneous active (P) and reactive power (Q) of the AFEC is carried out using virtual flux from the main supply. The optimal switching states are selected from the switching table based on the errors in P and Q and hence the active and reactive power control is directly accomplished by the device switching states of the front-end rectifier. Multilevel inverter at the motor side is controlled using a newly proposed PTC algorithm. The proposed algorithm predicts the behavior of the drive under various load conditions which accordingly sets the power requirement for the AFEC. The optimal voltage vector selection in the proposed algorithm is applied to both rectifier and inverter, which reduces the number of switchings and therefore results in distinguishable reduction in the switching losses. Four quadrant operation of this multi-level inverter fed induction motor drive with DPC at the front end and PTC at the load end is implemented in Matlab/Simulink environment and the results are presented. The performance obtained for the drive with the proposed control configuration under various steady state and transient operating conditions show that the drive possesses an excellent dynamic response apart from having impeccable power quality at the front end.