Advanced Startup and Smooth Transition to Sensorless Field Oriented Control for CSI-Fed PMSM Drives in Submersible Pumps

This paper introduces a reliable startup method with a smooth transition to sensorless field-oriented control (FOC) in current source inverter (CSI)-fed Permanent Magnet Synchronous Motor (PMSM) drives used in submersible pump applications. The strategy ensures a smooth transition to sensorless control, enhancing efficiency, and improves the reliability of the drive system. The proposed method minimizes speed and current oscillations during the transition stages. Furthermore, the proposed method addresses these issues by eliminating the error between the estimated and reference frames. Subsequently, using the proposed error compensation strategy, the error between the real and estimated frames is corrected. This method ensures a smooth transition from synchronous startup to sensorless FOC without requiring exact q-axis current or alignment error calculations while minimizing speed and current oscillations. It offers a robust, adaptive shift from I-f startup to FOC under varying conditions. Additionally, the proposed position error compensation corrects rotor discrepancies from dead-time, control delays, and parameter variations, improving torque and flux control, reducing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i>-axis current and torque ripple, lowering copper losses, and eliminating steady-state errors. This results in a faster, more reliable transition, avoiding prolonged startup durations and enhancing system stability. Simulation and experimental results validate the method's effectiveness, demonstrating minimal oscillations in speed and current.