An integral method combining V/Hz and vector control of permanent magnet motor

This paper presents an original method for sensorless speed control of Permanent Magnet Motors (PMM). The proposed method is robust to parameter variations, does not require a starting sequence and shows good performance at low and high speeds operation. The benefits mentioned above are achieved by combining features of volts per hertz and vector control methods. The proposed method uses the q axis current regulator to estimate the angular speed of the PMM instead of providing the q axis voltage command for the inverter as is done in traditional motor control methods. The q axis voltage inverter command is calculated from q axis and d axis current references and motor parameters similar to V/Hz control method. An observer performs the estimation of q and d axis rotor fluxes, from measured and reference currents and voltages. The observer estimates are crucial for flux and consequently voltage estimation and robust operation of the method. In addition, the d axis current regulator performance is enhanced, with a feed-forward voltage signal calculated from motor parameters. The analysis presented in this paper, shows that error in the alignment with rotor flux position is proportional to the estimated rotor flux in q axis which was consequently used for rotor angle alignment.