Sensorless estimation of surface-mounted permanent magnet synchronous motors based on polar-corrected feedforward quadrature phase-locked loop

• An enhanced quadrature phase-locked loop (EQPLL) with polarity correction and feedforward compensation is proposed to eliminate the 180° convergence deviation during motor reversal and reduce angle estimation errors during acceleration/deceleration. • The improved phase discriminator in the stationary frame enables polarity correction without relying on Park transform, avoiding accumulated estimation errors. • The feedforward compensation signal, filtered by an enhanced generalized integrator, achieves low-delay and low-noise angle error compensation. • Experimental validation shows the proposed scheme reduces noise mean square error by 24.33% compared to existing feedforward compensation methods.