Control of Rotor Field-Oriented Induction Motor Drive During Input Supply Voltage Sag

This article proposes a speed control strategy for rotor field-oriented induction motor (RFO-IM) drive during input supply voltage sag (VS). The purpose of this control technique is to maintain the torque and speed constant during VS condition. In the control technique, reference d-axis and q-axis current commands are obtained by solving the voltage, current, and torque constraints in the current plane. In the event of VS beyond a limit, the control is made such that the motor delivers the load torque with reduced speed. Traversal of operating points of the motor during input supply VS for constant load torque and rated reference speed are analyzed, and the limit of reduction in d-axis current reference is also obtained. Mathematical equations explaining the current trajectory to be followed during VS, VS limit, and the settling speed are derived. The proposed control is simulated in MATLAB/Simulink and experimental validation is conducted on a 3-hp IM.