The Research On Sensorless Control Strategies Of High Power Induction Mortor

Multilevel inverters are very suitable for high-voltage and high power conversion applications, for they have the advantages such as low voltage stresses for power devices and absence of voltage evenness of power devices compared with the topology of series connection. And the space voltage vector control of induction motors has been widely used in recent years because of its simple methods and high stable/transient performance.This thesis comprehensively describes the development future and the present development condition of multilevel inverter. And then present the development of direct torque control algorithms for induction motors fed by three-level diode-clamped inverter (neutral-point clamped, NPC) .On the basis of theory of direct torque control, this thesis system analyses the inherent property of three-level inner vectors. and introduced the application of fixing vector compound. Based on the way of keeping neutral point balancing and reducing the pulsation torque. Aimed at high power induction motor, this thesis brought forward a way to form 12-borders stator magnetic field, it can reduce the frequency of switch.This thesis adopted MRAS way to observe the speed of motor. then this control way can remove the speed sensors in motor drivers.Finally, this thesis simulates algorithm proposed with MATLAB.