Speed sensorless with modified rotor flux field oriented control of faculty three-phase induction motor

Abstract

This thesis proposes a high performance speed sensorless vector control of star-connected three-phase Induction Motor (TPIM) under open-phase fault. The proposed drive system consists of two parts: Indirect Rotor flux Field-Oriented Control (Indirect RFOC) and speed estimation based on Model Reference Adaptive System (MRAS). In RFOC of TPIM, rotor speed estimation is required in order to implement the control algorithm. The rotor speed can either be obtained using a mechanical speed sensor or it can be estimated from the terminal variables of the TPIM using an observer. In this work, rotor speed is estimated using an observer which is based on MRAS. However, unlike other MRAS based speed estimators, the proposed observer is designed to work for both healthy and faulty TPIM. When a fault occurred, minimum changes to the control parameters and special transformation to the variables of the RFOC and MRAS speed estimator are performed. The ability of the drive system to work in both healthy and faulty conditions is important in some critical applications that require continuous operation of the drive systems. To verify the effectiveness and reliability of the proposed method, simulations and experiments are conducted. In this research, MATLAB/Simulink software is used to evaluate the effectiveness of the proposed method. Verification and validation of the proposed drive system are through hardware implementation using dSPACE DS 1104 ACE KIT and 1.5 kW TPIM. The simulation and experiment results show that satisfactory performance of the indirect RFOC and MRAS for a TPIM under open-phase fault is achieved. It is shown that the torque and speed oscillations caused by the unbalanced structure of the faulty TPIM are effectively reduced by more than 50%. Speed sensorlesss RFOC of TPIM under open-phase fault condition is shown to be capable of operating in speed range from zero to 60 rad/s, however with reduced torque capability.