A low cost stator flux oriented voltage source variable speed drive

A new control strategy for variable-speed drives is presented. It is aimed at improving or even replacing existing volts-per-hertz (V/f) open-loop variable-speed drives. This strategy generates d-q voltage commands in the stator-flux-oriented reference frame by closing a torque loop and a flux loop. Stator flux and electromagnetic torque feedback signals are derived from DC voltage, DC current, and inverter switching states. Digital implementation is seen to be possible with slight modification of existing V/f drives. Satisfactory performance was achieved on a prototype. The proposed strategy appears to be a good compromise between high-cost, high-performance field-oriented drives and low-cost, low-performance V/f drives.<>