PUBLICATIONS

 When paralleled inverters operate an electric motor, a circulating current is typically generated due to a device-switching timing error. To mitigate this error, an AC reactor is installed in the output of the inverters to reduce the circulating current. However, unbalanced output currents (UOCs) are produced due to the difference between the resistance and inductance in the AC reactor. When there is a difference in the output current of the inverters, a single inverter outputs excessive current, due to which the motor cannot be controlled to the maximum power. In this study, we perform mathematical modeling and analyze the causes for the generation of UOCs in parallel connected electric motor drive systems. Furthermore, we minimize the unbalanced load by controlling the current output based on the output status of the inverters in any control algorithms of a motor. The proposed control method is experimentally verified by implementing a system that connects three inverters in parallel.