Agus Suprajitno, a doctoral student of the Department of Electrical Engineering, Faculty of Engineering, Universitas Indonesia (DTE FTUI), successfully earned his Doctoral degree after completing an open dissertation defense on Wednesday (December 24). Through his dissertation entitled “Performance Improvement of Sensorless Induction Motor Control Based on an Adaptive Observer Using q-Axis Current Estimation Error Compensation,” Agus became the 190th Doctoral graduate of DTE FTUI and the 630th Doctoral graduate of FTUI, graduating with a Very Satisfactory predicate and a GPA of 3.87.
Agus’s research focused on induction motor control systems employing a vector control method known as Rotor Flux Oriented Control (RFOC). This system requires information on angular speed to transform motor current components into d-axis and q-axis currents. However, in sensorless induction motor control systems, when subjected to large, sudden load disturbances, the speed estimation response tends to converge slowly to the actual speed value. As a result, the actual motor speed responds more slowly in returning to its reference value, leading to degraded control system performance.
In this study, Agus investigated methods to overcome this issue when sensorless induction motor control systems are exposed to large, transient load disturbances. The research began by identifying parameters that are closely related to the motor speed estimation response. It was found that the q-axis current estimation error is strongly correlated with motor speed estimation errors.
Since information on q-axis current estimation error can be obtained in sensorless induction motor control systems, it was proposed to use this information to compensate the motor speed estimation calculation, with the aim of improving the system’s speed response. The proposed compensation method was analyzed to assess its impact on overall system stability by examining the eigenvalues of the compensated closed-loop system.
“It was found that all system eigenvalues lie within the stable region on the left side of the imaginary axis in the complex plane. The compensation method was also experimentally tested by applying large, transient load disturbances. The results show that the proposed speed estimation compensation method effectively addresses speed estimation issues, particularly under large load disturbances. The actual motor speed response in a closed-loop sensorless induction motor control system can be significantly improved, making it comparable to systems equipped with speed sensors,” Agus explained.
Dean of FTUI, Prof. Kemas Ridwan Kurniawan, S.T., M.Sc., Ph.D., commented on Agus’s research. “The system design developed in this research is highly comprehensive, ranging from mathematical modeling and observer formulation to adaptive algorithm design, as well as verification through simulation and experimental validation. We hope that this research can be implemented in relevant industries so that it does not remain limited to a dissertation, but can also be applied in real-world applications,” said Prof. Kemas.
The research findings were presented during the open doctoral promotion session chaired by Prof. Kemas Ridwan Kurniawan, S.T., M.Sc., Ph.D., as Chair of the Session, with Prof. Dr. Ir. Feri Yusivar, M.Eng., serving as Promotor, and Dr. Abdul Halim, M.Eng., as Co-Promotor. The panel of examiners consisted of Prof. Dr.Eng. Drs. Benyamin Kusumo Putro, M.Eng., Dr. Aries Subiantoro, S.T., M.Sc., Naufan Raharya, S.T., M.T., Ph.D., Prof. Dr. Ir. Andi Adriansyah, M.Eng. (external examiner from Universitas Mercu Buana), and Dr. Nanda Avianto Wicaksono, S.T., M.T. (external examiner from the Ministry of Energy and Mineral Resources of the Republic of Indonesia).
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