Analysis on dead-time compensation method for direct-drive PMSM servo system

In permanent magnetic synchronous motor (PMSM) drive driven by three-phase full-bridge inverter, dead time is commonly added to the control signals to avoid the conduction of the bridges. But dead time will deteriorate output voltage, cause current distortion and lower motor performance. This paper firstly analyses how dead time influences inverter output, and then introduces a voltage space vector compensation method for dead time effect in SVPWM control PMSM drive where d-axis current equals zero. However, the original compensation method has problems in judging the direction and amplitude of the compensation vector. So the real current vector angle (calculated from i_α and i_β) is proposed as the direction judgment instead of rotor position angle, and the filtered real-time DC voltage of the inverter is proposed to be used in the amplitude calculation. Finally corresponding simulations and experiments were carried out, proving that the proposed improvements can effectively reduce the current distortion, torque ripple and speed fluctuation.