Decoupled Control of AC Machines Connected in Parallel

Abstract

The work presented in this thesis develops a new concept for independent control of two five-phase permanent magnet synchronous machines (PMSMs) connected in parallel and fed by a single five-leg inverter. The proposed scheme presented a reduction in the number of inverter legs, when compared to an equivalent two-machine three-phase drive system. It can be seen from the developed model only two stator current components (d-q) are responsible for torque and flux production, while other components (x-y) do not used. Through an appropriate phase transposition of the stator windings, the other components (x-y) it can be used to connect in parallel the other machine in such a way that the torque and flux producing current components of the first machine do not affect the production of torque and flux of the second machine and vice versa. The purpose decoupled control strategies for the two five-phase PMSM connected in parallel are made by using filed oriented control (FOC), conventional direct torque control (DTC) and DTC-SVM; all are based on sliding mode control (SMC). The SMC law improve the stability and robustness of parallel-connected two five-phase PMSMs with parameter variations, reduce the ripples of the torque and flux as well as improve the dynamic performance. In order to increase the proposed drive robustness and decrease the number of sensors as well as its cost, an Extended Kalman Filter (EKF) and sliding mode observer (SMO) scheme have been adopted. The results show better speed tracking performance at both dynamic and steady state, acceptable estimations errors, robustness in different tests