A Speed-Sensorless Vector Control of Parallel-Connected Multiple Induction Motor Drives with Adaptive Rotor Flux Observers

The purpose of this paper are to present the speed-sensorless vector control method of parallel connected multiple induction motors drive system fed by a single inverter using the averages and differences of the currents of each motor, and to show the stability with our method in unbalanced load. We have a model using the averages and differences of currents detected by sensors, rotor fluxes, motor speeds, and the parameters estimated by the adaptive rotor flux observers, respectively. Therefore, every equation for torques, rotor fluxes, and current references is expressed in averages and differences. So, the states of each motor are grasped accurately, even though the loads are unbalanced. Because of above reasons, we can control parallel-connected multiple induction motors in a stable manner, even if the extreme unbalanced load is applied for each motor. In order to compare with proposed method, we explain the method used currents detected in common part of each motor, which are applied in practical industrial applications. We explain them by simulations too. Further, we show that the proposed method can be applied for the system which is connected three or more motors in parallel