E-Drives Modeling and Torque Control for Electrical Vehicles

In the automobile industry, new technologies are becoming available with a strong chance of taking over as the standard design in the future. These systems rely on an electric traction system that can work in tandem with a traditional internal combustion engine or not. Nevertheless, as e-mobility is a young technology, there is still space for progress. In a world where the development of electric cars is constantly expanding, tactics for controlling the torque of electric machines have grown to be of the utmost importance. The basic objective of all implementable control techniques is to ensure that the machine’s torque regulation is maintained under all conceivable operating situations. For these reasons this thesis concerns unified torque control techniques of traction motors for electric vehicles. The thesis is carried out in the context of a research collaboration between the PEIC interdepartmental center of the Politecnico di Torino and the Punch Torino company. The first goal is to create an accurate simulation of the electric traction of a pure electric car or hybrid electric vehicle. This electric propulsion is made up of standard components such a converter, storage system, and electrical machine. A battery is first selected as the storage system. A three-phase inverter, specifically a two-level inverter, is the converter that was chosen. The high performance Internal Permanent Magnet (IPM) motor used in the electric machine allows it to operate very close to its limitations. Simulink has been used as the simulation environment, and each component has been simulated using either pre-existing blocks or newly constructed ones. The system generated in the simulation environments is tested in comparison to a model developed in another simulation tool (PLECS), highlighting its validity. The first goal of the thesis is to set up a new circuital model of the e-Drive, valid for instanataneous simulation, and also able to consider fault conditions. The modelling approach considered for the e-Motor is the Voltage Behind Reactance (VBR) model. It represents the motor as an RLE load, with coupled inductors and controlled voltage generators imposing the back EMF voltages computed by the motor model. The second aim of the thesis is to analyse the control method for the electric motor and generate it in C-code. The Field Oriented Control (FOC) solution has been developed for the IPM motor and it is based on multiple Look-up Tables (LUTs). In this approach, the optimal current setpoints are calculated from the operating conditions of the machine and data stored in precalculated LUTs. The developed 4D LUTs FOC has been compared with an existing Direct Flux Vector Control (DFVC) solution used as benchmark. Using the VBR model developed a control comparison between 4D FOC and DFVC is done. The result obtained attest that The 4D FOC represents also a valid control solution for the efficient control of the e-Drive taken into account. Also peculiar charactestic are shown like the capability to overcome the issues due to machine electric parameters variation with temperature. The greatest drawback resides in the difficulties in the elaboration of the 4D LUTs. Nevertheless LUTs computation is an offline operation that guarantees a fast and efficient online response of the control. The whole system developed with the powertrain circuital model and the control represents a valid simulation environment and also a strong base for future development in the optic of Fault Tolerance.