부산대학교 도서관

In this paper, a new approach for achieving speed control of induction motor and three phase inverter output balanced currents under unbalanced grid voltage condition are presented. The proposed method is based on vector control of induction motor by using field oriented control. In unbalanced grid voltage condition, negative sequence components appear on the grid voltage vector, leading to distorted currents of motor if the reference torque maintained constant. To overcome the problems related to grid voltage imbalance, inverter output current and voltage in unbalanced network are measured and positive and negative component of voltage and current are extracted. Then torque and flow components that are essential parameters of field-oriented control of induction motor are calculated. Torque and flow compensator components are obtained by decomposition of positive and negative components of current and flow then used to correct the reference of torque and flow. Speed control of induction motor and three phase inverter output balanced currents under unbalanced grid voltage condition are obtained by correcting the reference of torque and flow. The proposed method is simulated in MATLAB software and the results of the simulations confirm the validity of the proposed method.