Usefulness of a frequency-hybrid vector control for a sensorless induction motor drive

This paper examines and demonstrates the usefulness of a frequency-hybrid vector control scheme for sensorless induction motor drive through actual-machine-based performance evaluation tests. The new approach utilizes a new indirect orientation scheme and a stable-filter-embedded direct orientation scheme, and exploits their advantages. It is confirmed through extensive tests with small and large standard motors such as 0.3, 3.7, 30 kW and special low-voltage motors dedicated to electric vehicles that the sensorless vector control scheme has the following potential usefulness: (1) it can make machines that produce more than 200% rated torque at standstill, (2) in both motoring and regenerating modes, the rated torque can be produced even in the very slow speed range, including zero speed and zero frequency, (3) for constant speed, good linearity of torque response is attained, (4) it has the ability to track variable speed acceleration commands up to 5000 rad/sz in the mechanical frequency sense, (5) it can accept a zero-speed command and settles the machines to a stable standstill with no vibration, (6) it accepts instant injection of rated load even for zero-speed control, and (7) it accommodates a load with huge inertia. (C) 2002 Wiley Periodicals, Inc.