Modelling and control of an innovative electrical drive for electrical vehicles

In the automotive world new technologies are entering the market with great potentialities of becoming the future dominant design. These technologies are based on electric traction system cooperating or not with classic combustion engine. In this innovation phase, it is fundamental to fill the gap between old technologies with new ones. For this reason new components and features have to be introduced in the future traction system. In this case study an innovative electromechanical actuator for safety purpose is proposed to be added in the electric traction system. It needs specific conditions to be actuated which are monitored through electric machine parameters. This innovative actuator will not be analysed, while the whole electric traction system and its relation with it will be treated. This thesis has different aims that comprehend all the aspects of the previously cited system. The first is to develop a complete model of the electric traction of an electric vehicle in a simulation environment. This electric traction is composed by typical elements as storage system, converter and electrical machine. The storage system is not strictly defined and a battery is chosen. The selected converter is a three-phase inverter, in specific a two-level inverter. The electric machine is a PMASR motor with high performance and it could work near to its limits. In addition to these, the mechanical load is also considered in order to simulate the mechanical dynamic too. The chosen simulation environment is Simulink in which every components have been modelled with pre-existing block or ad hoc generated one. The second aim is to analyse the control method for the electric motor and generate it in the specific programming language. The control method employed is the Direct Flux Vector Control, which is greatly suitable for an automotive electric motor since it is advantageous in flux-weakening operations. The third aim is to generate a secondary motor control that is active when a safety action of the innovative electromechanical actuator is required. The complete shut-down of the inverter and the electrical machine is necessary to allow the actuator operate. This task is performed by the secondary motor control through a sequence of precise actions. Specific conditions have to be monitored in order to trigger when necessary the actuator. The fourth aim is to analyse the different method employed to monitor these conditions, thus find out a procedure to estimate the necessary parameters. These quantities are the magnet temperature for safety issue and the magnet back-emf for the Uncontrolled Generation, which lead to the unsuccessful shut-down of the electrical system. The system generated in the simulation environments is tested in comparison to a model developed in another simulation tool, highlighting its validity. Further steps will be testing it in comparison to the real electric traction system after its built. Moreover the implemented control method for the motor, both the principal and the secondary one, are tested and simulation results are provided, showing their suitability and validity. A procedure to estimate the magnet temperature is developed and promising results are shown. The magnet back-emf is estimated as a direct consequence of the magnet temperature. These results are the basis for further developments and improvements of this estimation method, which should be tested in the real traction system.