Design of multi-parallel drive technique for system with numbers of Permanent Magnet Synchronous Motors

This paper discusses a multi-parallel drive system, which uses two types of inverters; A main inverter with V/f control and numbers of auxiliary inverter with vector control and damping control to control multiple numbers of Permanent Magnet Synchronous Motors (PMSMs). In addition, in PMSMs, the auxiliary windings are placed in the slots together with the conventional windings. The auxiliary windings are used in the auxiliary inverter with damping control to suppress the torque vibration when the motor speed is converged. From the simulation and experimental results, the proposed system achieves a stable operation with two parallel connected PMSMs. Furthermore, the experimental results demonstrate the effectiveness of the proposed system even if the output power of the auxiliary inverter is less than 10% of the main inverter. Moreover, the relationship among the response of the damping control, the overshoot of the motor speed and the power capacity of the auxiliary inverter are investigated in simulation and experiments. From the results, it can be confirmed that if the application requires a slow response of the motor speed, the smaller power capacity of the auxiliary inverter can be designed to be 10% compared with the main inverter capacity.