A New Speed Estimation Method of the Direct Torque Control

The stator flux magnitude fluctuates in a given hysteresis-band and has an exiguity difference with the actual value in DTC (direct torque control), for the stator flux is controlled in close-loop method, the command value can replace the actual value in control system. On this foundation, fix the reference frame on the stator current vector and rotate synchronously (stator current orientation). The stator flux equation doesn’t use integrator including stator resistance. Therefore, the influences on flux estimation accuracy, caused by integrator error, are avoided. The speed estimation arithmetic deduced based on stator-current oriented, has the characteristics of small account, high estimation precision and easy to control in DSP. The experimental results of the DTC for the 4kW induction motor are given, and verify that theory analysis is right and practical.