PLL method with speed feedforward compensation for extended EMF-based IPMSM sensorless control

This paper proposes a phase-locked loop (PLL) with a low bandwidth and high estimation performance in terms of position and speed through speed feedforward compensation for driving extended back electromotive force (EEMF)-based sensorless control for an interior permanent magnet synchronous motor (IPMSM). In this case, lowering the bandwidth to reduce sensitivity to disturbances of the PI controller, where the position error is controlled to zero, may create a problem of decreased estimation performance. The proposed method calculates speed through mathematical calculations of the EEMF, which is observed using an EEMF-based IPMSM model, and adds it to the output of the PLL. The added speed feedforward compensation reduces the computational burden of the PI controller. Therefore, fast estimation dynamic characteristics can be obtained even at low bandwidths. The improvement of the estimation performance of the proposed method is evaluated by analyzing the equivalent block diagram using the final value theorem theory. Through this, the estimation performance is shown. It can be seen that the position estimation error for various types of speed inputs converges to zero. In addition, validity and implementation of this method are verified by experimental results.