High performance V/f control method for PM Motor

This paper proposes a novel V/f control method for PM motor drive system without position sensor. Unlike sensorless vector control, V/f method does not require high performance digital processing.This paper presents three novel topics for V/f control. At First, instability of conventional V/f control is shown, and a stabilization method consisting of a high-pass -filter and a feed back from d-axis current is proposed. After that, a control strategy yielding high efficiency is introduced. It is shown that the condition id=0, corresponding to high efficiency operation for SPM, can be achieved without explicit estimation of dq-axis. Furthermore, since this method is based on the evaluation of the reactive power, knowledge of R_??_ and e. m. f. is not required. At last, a starting method that does not need flux saturation to decode NS pole of permanent magnet, is proposed. The structure of the resulting control system is very simple and its effectiveness has been confirmed experimentally by using 1.5kW, 3600r/min and 3.7kW, 7200r/min PM motors.