Sensorless interior permanent magnet synchronous motor drive system with a wide adjustable speed range

The authors propose a novel extended flux estimating method for an interior permanent magnet synchronous motor. By using the proposed method, an extended flux can be systematically derived. Then, the shaft position and speed of the motor can be obtained. Starting from a standstill and at a low-speed range control, a current-slope estimating method is used to replace the extended flux method because the estimating extended flux decreases as the motor speed is reduced. By combining the extended flux and the current-slope estimating methods, the interior permanent magnet synchronous motor drive system can be controlled in a wide range with satisfactory performance. The adjustable speed range is from 1 to 2000 r/min. In addition, the system performs fast transient responses and good load-disturbance responses. Moreover, a sensorless position control system has been well developed based on the speed control drive system. A TMS 320LF2407 digital signal processor is used to execute the rotor position estimation, rotor speed estimation, current-loop control, speed-loop control and position-loop control algorithms. The hardware circuit therefore is very simple. Several experimental results are provided to validate the theoretical analysis.