Closed-Loop Voltage Control for Maximizing Inverter Output Voltage in the Field Weakening Region of Induction Machines

It is desirable in induction motors drives to maximize the inverter output voltage to increase the output torque and power in the field weakening (FW) region. Existing FW control methods produce high torque ripples and show high step reductions of the $d$ -axis current during the transient period from constant torque (CT) to FW. In addition, many proposed controllers are difficult to tune and require specific control algorithms to deal with parameter sensitivities. In this article, a closed-loop voltage control method is developed based on the $d$ -axis reference current to maximize the voltage extraction from dc-link voltage while minimizing the above disadvantages. This is achieved by applying the proposed $d$ -axis current, which compensates the difference between the hexagonal reference voltage and stator voltage for corresponding stator voltage vector position. Therefore, the output torque and power of the induction machine (IM) are maximized in the FW region. The proposed method is first presented analytically, and then, simulation and experimental results are included to verify the control method.