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The cross-coupling effect is the magnetic coupling effect of the flux caused by direct-axis current and quadrature-axis current due to nonlinear characteristics of core material. The knowledge of the cross-coupling inductance is of particular importance in order to obtain the angle deviation of magnetic axis from geometric axis of the rotor lamination, which will contribute to the minimization of rotor position estimation error. However, the cross-coupling inductance varies with operating conditions and is often ignored in rotor position estimator. This article proposes a general online method for sensorless predictive direct torque control identifying angle deviation of magnetic axis from geometric axis caused by the cross-coupling effect. Only intrinsic electrical signals for machine drives are employed to build response points distribution graph and implement the angle deviation identification. Experimental results verify that the proposed graphical method online identifies the angle deviation and effectively suppresses the estimation error in the rotor position estimator caused by the cross-coupling effect.

As a modulation technology for low electromagnetic interference, random pulsewidth modulation has been increasingly applied to inverter power supply for three-phase motors. This article proposes a random triangular carrier wave space vector pulse width modulation (RTCW-SVPWM) strategy with dual random parameters, which are subject to a uniform distribution. In this strategy, the shape of the triangular carrier wave changes with random carrier frequency and random pulse center position while the duty cycle of the pulse is the same as that in the conventional SVPWM. 2-D Fourier analysis is used to describe the basic principle of the harmonic dispersion effects in the proposed strategy. The simulation and experimental results show that the dominant harmonics of the output voltage at the integral multiples of the carrier frequency are scattered to their sidebands. Therefore, the prominent harmonic peaks can be greatly attenuated and the harmonics in the high-frequency band are evenly distributed.