Abstract
This paper proposes a new rotor phase estimation method for sensorless drive of permanent‐magnet synchronous motors (PMSMs), which uses the motor‐driving stator voltage and current information for estimation. The proposed estimation method utilizes two high‐order low‐pass filters that can change their bandwidth according to the speed estimate. The high‐order filters are potentially able to attenuate sufficiently the harmonics contaminating the stator voltage and current and to produce an almost pure‐sinusoidal rotor flux estimate consisting of only the fundamental component. Such a sinusoidal rotor flux estimate allows highly accurate estimation of the rotor phase even at very low speed. In order to separate the fundamental component of the rotor flux estimate from its harmonics with no phase lag/lead in variable‐speed environments, the proposed low‐pass filters have the capability to change the bandwidth adaptively to the rotor speed. The sensorless drive system using the proposed phase estimation method has several strong capabilities: (1) it can start up PMSMs from standstill at the rated load; (2) it can drive PMSMs stably even at very low speed, such as 1/60 of the rated speed under the rated motoring/regenerating load; (3) it can drive PMSMs accompanied with an inertial load factor of over 50. The proposed estimation method is simple and easily installed into sensorless drive systems. This paper presents the new estimation method in detail and shows how it is installed into the drive systems by using a concrete example. The usefulness of the method and the performance of the drive system are examined and confirmed through extensive experiments. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(8): 1–14, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10286