This paper proposes a novel sensorless control strategy for permanent magnet vernier machines (PMSMs) in high-power propulsion applications. Integrating fractional-order proportional-integral (PI) control with a fast terminal sliding mode observer (FTSMO), the approach enhances wide-speed sensorless control. The fractional-order PI controller mitigates torque ripples, while the FTSMO eliminates the need for a phase-locked loop (PLL), reducing computational load and design complexities. An adaptation law facilitates direct speed estimation, and a unique terminal sliding surface improves reaching phase dynamics, enhancing convergence rates and estimation precision. Validated through MATLAB simulations on a 5 MW high propulsion PMSM, the proposed method demonstrates effective sensorless control, emphasizing its potential for high-power propulsion application.