Abstract: Aiming at the harmonic current of a permanent magnet synchronous motor steered by vehicle electric power at a low speed caused by dead time and on-voltage drop of a three-phase inverter,this paper proposes a variable step function compensation method for α and β axis voltages.Firstly,in order to obtain a more accurate three-phase current polarity to avoid compensation voltage perturbation,a current averaging method is proposed to replace the first-order low-pass filter.Secondly,in order to improve the quality of the output waveform and eliminate the zero-current clamping caused by inverter dead time of the motor at a low speed and light load,a variable trapezoid function is proposed for α and β axis voltage compensation.Finally,the harmonic current of a permanent magnet synchronous motor for vehicle electric power steering (EPS-PMSM) is evaluated based on the numerical simulation under three working conditions,including uncompensation,traditional average voltage compensation and variable step function compensation.The results show that,under the condition of a low speed and light load of the motor,compared with the traditional average voltage compensation method,the variable step function compensation method further reduces the total harmonic current distortion by about 23.42%,and eliminates the zero-current clamping.