An improved indirect vector controlled current source inverter fed induction motor drive with rotor resistance adaptation

The current source inverter (CSI) topology is well suited for high power medium voltage (MV) drive applications. For decoupled control of the machine flux and torque, indirect vector control (IVC) method is preferred because of its less calculational complexity and reduced machine parameter dependence. Because of the absence of a flux control loop, conventional IVC CSI drives exhibit poor dynamic performance and transient field misorientation. Hence by incorporating two additional proportional integral controllers with machine current feedback signals, modifications are done on the conventional IVC CSI drive to ensure superior decoupling and field orientation operation. For the feed forward adjustment of slip frequency rotor resistance is required which undergoes considerable variation leading to the coupling of the d-q axes variables and produce sluggish response. In order to achieve proper flux orientation in IVC induction machine drive, a model reference adaptive controller (MRAC) utilizing reactive power is used for online estimation of rotor resistance. A load torque observer with feedforward control is also employed to enhance the dynamic performance of the induction motor drive. The performance of an induction motor under improved IVC method and rotor resistance updation scheme based on model reference adaptive control (MRAC) has been studied and confirmed by simulation using MATLAB /SIMULINK.