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.
This work was supported in part by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT (MSIT); in part by Korea Institute of Energy Technology Evaluation and Planning (KETEP); and in part by the Ministry of Trade, Industry and Energy (MOTIE) of Republic of Korea under Grant RS-2024-00333208 and Grant 20225500000110.
