A study of position sensorelss control for IPMSM having non-sinusoidal inductance spatial distribution based on pattern matching method

A pattern matching method for position sensorless control of IPMSMs having non-sinusoidal inductance spatial distribution in standstill and very low speed region has been proposed. In the proposed method, the rotor position is estimated by comparing the phase current derivatives measured in a real-time with those in advanced. The current derivatives are obtained by measuring the phase currents twice at the certain voltage vector of inverter switching. The certain voltage vector not only must be created in all rotor position, but also must continue for at least a minimum time (t_min) to measure the currents twice. However there exists conditions which could not be secured t_min depending on the load current and the rotor position. In previous researches, switching-state phase shift method is utilized in order to create the certain voltage vector by injection high frequency voltage in all rotor position. In this paper, proposed various switching-state phase shift methods are explained and strong and weak points of each method are compared. Furthermore, the effectiveness and remaining issues of each methods are represented by experimental results.