Mechanical-sensorless robust control of permanent-magnet synchronous motorusing phase information of harmonic reactive power

This paper proposes a novel control strategy of a permanent-magnet synchron ous motor without mechanical sensors. The strategy is based on use of harmo nic reactive power and utilizes its relative phase information to estimate the rotor position, i.e., d-axis direction that corresponds to the magnetic poles on the rotor. The harmonic reactive power can be calculated by filte ring a specific harmonic voltage vector and a harmonic current vector and i s never affected by variation of the winding resistance that may be caused by temperature fluctuation or a skin effect due to the harmonies. Since the harmonic reactive power has a relative phase with respect to a phase refer ence signal, which is proportional to the estimation error of the rotor pos ition, the estimated position converges to the true value by zeroing the ph ase shift. To achieve this estimation algorithm, a phase-locked-loop (PLL) technique is employed in the rotor position estimator. In the PILL, the har monic reactive power is converted to a digital pulse to extract only the re lative phase information and to eliminate amplitude information that is rel evant to d-axis and q-axis inductance and the rotor speed. Therefore, the p roposed estimation technique is almost perfectly robust against every motor parameter and any operating conditions. The paper describes a theoretical aspect of the method and presents several computer simulation and experimen tal results to show the feasibility of the proposed strategy.