Sensorless induction motor drive with a single dc-link current sensor and instantaneous active and reactive power feedback

This paper proposes a novel torque and speed control structure for low-cost induction motor variable-speed drives with a single de-link current sensor . The controller is based on reconstruction of the active and instantaneous reactive power from the de-link current,without the use of a shaft sensor, An effective way of achieving tracking of set values of motor torque and f lux is to base the estimation on the instantaneous active (P) and reactive power (Q). The paper proposes a way for extracting instantaneous P and Q in formation from the de-link current and the pulsewidth modulation, pattern. Torque and flux controllers suitable for general purpose and traction appli cations are proposed. The paper presents analytical considerations, straigh tforward design guidelines, and experimental results obtained from a tracti on system with a battery-fed three-phase inverter and a 7.5-kW traction mot or.