Analysis and control of an IPMSM for traction applications
This thesis presents methodologies to optimally design controllers of Interior Permanent Magnet Synchronous Motors (IPMSM's) for traction applications. These controllers include: optimal current reference calculation, optimal torque-speed trajectory design and sensorless control.
The design of the current controller reference requires an accurate machine model; the selected model was a cross saturated model. Cross-magnetization and saturation produce a reduction of the maximum power of the machine; their accurate calculation allows us to predict the generated torque and the stator voltage in the machine under field weakening. The current controller reference is based on maximum torque per ampere and field weakening; this current reference is designed such that the motor can operate with minimal losses over the whole speed and torque range while satisfying voltage and current limits.
Optimal trajectory design is used to generate the speed and torque references for two subsystems in a series Hybrid Electric Vehicles (HEV): traction motors and engine-generator. The trajectory optimization of the traction motors is designed to minimize losses while achieving the speed requirements. The trajectory of the engine- generator subsystem is designed to produce a requested amount of energy in a given period of time while minimizing the energy losses.
Sensorless control deals with the issues in practical implementation of the high- frequency injection methods for control of IPMSM machines without shaft position sensors. The controller is based on the high-frequency injection method, the injection is combined with an sliding mode observer eliminating the requirements of low-pass filters and improving the performance of the torque controller and hence improving the machine efficiency.
Simulation and experimental results are presented to validate the proposed controllers.