The crowded axis of the frequency: Optimal pole/zero allocation for a full speed sensorless synchronous motor drives

Full speed sensorless Interior Permanent Magnet Synchronous Motor (IPM-SM) drives estimate the rotor speed and position by means of a HF voltage injection at standstill or low speed operation and by some form of back-electromotive force or PM flux estimator at the medium and high speed range. Both the estimation strategies include an inner loop closed by a PI+I regulator for extracting speed and position, as well as high-pass, low-pass filters devoted to the separation of the injected HF voltages from the fundamental power voltages. Gains and time constant of the regulator, together with filter bandwidths interfere with PWM and injected frequency as well as with current control and speed control bandwidths. In order to design a high performance drive, all these frequencies have to be appropriately allocated. The paper gives a deep theoretical insight of the subject, supported by simulations and experimental validations, aimed to propose a complete set of guidelines for the optimal design of the sensorless control of IPM-SM drives.