Simple Speed Control Strategy for a Mono-Inverter Dual Parallel Permanent Magnet Synchronous Motor Drive System

This article proposes a simple speed control strategy for a mono-inverter dual parallel (MIDP) permanent magnet synchronous motor (PMSM) drive system, where two motors are connected in parallel to a single inverter. Since an inverter operates with a single reference voltage vector, one of the motors operates in an open-loop configuration. Such a simple control structure induces system instability and causes a loss of synchronism in the motor. Various studies have been conducted to address these issues; however, the complex design processes of the conventional control schemes pose challenges for practical implementation in diverse applications. The proposed strategy overcomes these limitations by employing a proportional-integral (PI) speed controller, which indirectly controls a secondary motor by injecting additional currents. This method ensures speed synchronization of two motors and reduces torque oscillations in the system under varying load conditions. A linearization strategy is, furthermore, introduced to address singularity issues that arise from rotor position differences and improve system stability. The performance of the proposed method for a MIDP PMSM drive system is verified through simulations and experiments.