Sensorless Control of PMSM by a Four-Switch Inverter with Compensation of Voltage Distortion and Adjustment of Position Estimation Gain

This paper proposes performance improvement schemes for sensorless PMSM control drive using a four-switch three-phase inverter (so-called B4 inverter). In the proposed scheme, the back-EMF estimation-based sensorless control algorithm is used to control the brushless PMSM without position sensors. In order to have stable operation, this paper presents a gain adjustment scheme that compensates the reduction of stable sensorless operation range as long as the rotor speed increases. In B4 topology, the center point of dc-link capacitors is connected to 3-phase load, and it is prone to have the load current distortion. Hence, to mitigate this problem, a distortion compensation scheme by modifying voltage commands using measured dc-link potentials is proposed in this paper. The validity of the proposed method is evaluated by simulations and experiments.