A Simple Sensorless MTPA Control Scheme for PMSM in PV-Fed Water Pumps

This paper introduces a new speed sensorless MTPA control strategy tailored for solar-powered Permanent Magnet Synchronous Motors (PMSM), predominantly employed in water pumping applications. Such drives often preclude the use of encoders due to the harsh, noise-prone environments. In addition, the fluctuations in input power, influenced by factors such as changes in irradiance and shading, yield considerable control challenges, particularly when a small decoupling capacitor is used for the DC link. Unlike conventional vector control schemes, the proposed control strategy eliminates the need for observers and avoids complex startup routines. Instead, the proposed controller tracks the Maximum Torque per Ampere (MTPA) trajectory by a simple selection of voltage gain coefficients that can be easily implemented using a low-cost microprocessor. The proposed controller is also capable of quickly stabilizing the drive under transients even with a DC link of low stiffness. Simulation and experimental results verify the effectiveness of the control scheme under varying operating conditions.