This paper proposes a modular multilevel converter (MMC)-based control strategy for high-power permanent magnet synchronous motors (PMSM), covering both low- and high-speed ranges in electric vehicle applications. Specifically, an improved hybrid injection method based on phase voltage harmonics is introduced. The injection waveform is optimized considering the common-mode voltage, high-frequency circulating current, and phase voltage to minimize capacitor voltage fluctuations. In addition, a novel quasi-proportional-resonant (quasi-PR) controller based on an enhanced filter is developed to mitigate circulating current issues. Experimental results demonstrate that the proposed hybrid injection method effectively suppresses capacitor voltage fluctuations, reduces bridge-arm current amplitude, and improves system stability. Furthermore, the proposed quasi-PR controller achieves lower circulating current and further enhances system robustness and disturbance rejection capability.