Current reconstruction method for PMSM drive system with a DC link shunt resistor

For the cost reduction of the inverter system, a DC link shunt resistor can be used to obtain the phase current of the AC motor. However, the phase current cannot be obtained from the shunt resistor when the duration of the active vector is shorter than the minimum time to sample the DC link current accurately. Conventional methods to reconstruct the phase current have some problems such as the high THD (Total Harmonic Distortion), the acoustic noise and the inaccurate reconstruction of the phase current in the low modulation region. In this paper, the cause of the noise in the conventional method is analyzed. To solve the acoustic noise problem, current reconstruction method based on current estimation is proposed. Intermittent PWM shift method is also proposed to enhance the accuracy of the reconstructed current in the low modulation region. The effectiveness of the proposed methods is verified through the simulations and the experiments. The usefulness of the proposed method is also proven by measuring the sound in the anechoic room.