Servo-performance hybrid vector control for sensorless induction motor drive

This paper presents typical results of an actual-machine-based performance evaluation test of a new frequency-hybrid vector control scheme for induction motors without speed or position sensors, which the authors have recently proposed. Their scheme utilizes a new indirect orientation scheme and stable-filter-embedded direct orientation scheme, and well exploits their advantages. It is confirmed through the extensive test by small to big standard motors such as 0.3, 3.7, 30 kW and a special low-voltage motor dedicated to electric scooter that their sensorless vector control scheme has the following potential performance: (1) it can make machines to produce about 300% rated torque at standstill; (2) in both modes of motoring and regenerating, rated torque can be produced even in very slow speed range including zero-speed and zero-frequency; (3) for constant speed, good linearity of torque response is attained; (4) it has ability to make machines to track variable speed command of acceleration up to /spl plusmn/6000 (rad/s/sup 2/) in mechanical sense; (5) it can accept zero-speed command and settles the machines at a stable standstill with no vibration; and (6) it accepts instant injection of rated load even for zero-speed control. The performance confirmed by the test is far away for previous schemes or sensorless drive apparatuses.