Design and implementation of sensor-based and sensorless control of a PMSM test system

Abstract: Transportation of liquids and gasses in industries in forms of pumping and fanning, constitutes asignificant part of the world-wide electric energy consumption. In order to meet global environmentalgoals of greenhouse gas emissions and sustainable material usage, the development of efficiency andtechnical lifetime of industrial pump and fan technology, are key. Innovative designs of electricmotors, motor control and electronics have improved the energy efficiency and technical lifetime ofresidual and wastewater pumps technologies. Mid-sized wastewater submersible pumps are oftenused in hazardous environments, where the pumped medium consists of a mixture of water, sludgeand solids. Solids in wastewater such as textiles are prone to get stuck in the impeller of the pump,thereby halting the motion, lower the efficiency or completely locking the rotor. An aspect ofimportance is henceforth the pump’s ability to provide full torque at low or start-up speed toovercome the blockade of the solids. “Xylem Water Solutions” most modern and advanced wastewater pump consists of a permanent magnet synchronous motor (PMSM) for obtaining a vastincrease of efficiency compared to induction motors traditionally used in wastewater pumpingapplications. Also, PMSM’s can provide full torque at zero speed. PMSM’s are commonly controlledby position-sensorless means. However, obtaining full torque at low- or zero speed is for sensorlessPMSM control extremely challenging.The thesis project examines sensor-based PMSM control and compares this to conventionalsensorless strategies. This was done both by building and analysing a simulated model inSIMULINK/MATLAB of both a sensor-based and sensorless drive system. Secondly, a laboratorytest system was implemented with a motor drive platform with programmable motor controlalgorithms. This was done partially to grasp the knowledge of implementation and design of motorcontrol, and partially to enable tests and comparisons between different motor control strategies in amotor brake bench test rig located at the lab of Xylem Water Solutions Sundbyberg.The implementation of the motor control platform lab system was successfully implemented and ranwith the vendors pre-configured sensorless control. An own interrupt-driven sensor-based cascadedmotor control algorithm was designed in SIMULINK where all suggestions of design andimplementation are outlined in the report. However, during an early step of the test procedure ofthe pre-programmed sensorless control code, the hardware equipment malfunctioned and caused abreakdown of the current-sensors of the controlled inverter. This led to disabled test equipment andleft the own-written code unverified at the time of the project’s end.The results from the simulation resulted in a successfully implemented SCVM model and a sensorbasedmotor control model. The sensored model was implemented by assuming synchronization atany given moment, whereas the SCVM finds the position angle by estimating the back-EMF of themotor. The simulated sensored and SCVM controls performs well for the targeted system application.Parametric study of the SCVM model suggests that both the stator winding resistance and thesynchronous inductance should be underestimated for guaranteed synchronization at start-up.