Sensorless control of three-phase synchronous surface-mounted PM motors. Practical viewpoint and algorithm optimizations

This thesis aims to present the topic of sensorless control of three-phase synchronous surface-mounted permanent magnet motors through a detailed analysis of an industrial product. Theoretical backgrounds are illustrated along with the practical implementation, allowing the reader to gain a practical perspective on the topic. The first chapter introduces briefly the basic theoretical concepts, to which reference will be made where necessary. The second chapter consists of a description of an industrial product. The latter was analyzed during an internship at a company that manufactures fans. A product description is provided, both from a hardware and software perspective. The third chapter introduces the alignment and start-up problems and presents some solutions implemented on the physical product. In particular, a position detection method without rotor movement is proposed. The latter exploits the saturation effect to determine the initial rotor position, thus allowing a smooth start of the rotor. The fourth chapter presents the algorithms and techniques that allow the effective implementation of the core of a sensorless system: alternatively, the flux observer or the back-emf estimator. The just introduced chapters describe the respective topic and provide a practical insight into the physical device by analyzing data acquired during operation. Algorithms and solutions to practical problems are provided, and some optimizations are suggested. The fifth chapter illustrates a simplified model of the whole physical system, realized in Simulink. A model of the motor is implemented, together with a sensorless vector field-oriented control. Simulation results are shown and analyzed to verify that design requirements are met.