A sensorless position control for four-switch three-phase inverter-fed interior permanent magnet synchronous motor drive systems

In this paper, a sensorless position control for four-switch three-phase (FSTP) inverter-fed interior permanent magnet synchronous motor (IPMSM) drive systems is proposed and studied. Unlike traditional sensorless position controls that are based on zero-voltage switching mode generated by a six-switch three-phase (SSTP) inverter, the proposed method utilizes the nature of the FSTP inverter; that is, only four active-voltage switching modes are generated. Using basic circuit theory, the relationship between the rotor position and the current-slope differences can be derived and expressed as 24 transformation matrices. The current-slope differences are calculated by two stator current slopes corresponding to the two different active-voltage switching modes. By reducing the number of power switches and using the proposed method to eliminate the encoder, a cost-effective FSTP inverter-fed sensorless IPMSM drive system is developed. Moreover, no additional hardware circuits and no switching strategy change are required for existing drive systems. Simulation results are shown to demonstrate the feasibility and effectiveness of the proposed method.