Examenspresentation Hanna Hallberg och Julius Bengtsson

Opponents: Otto Eriksson and Alexander Odhner

Examiner: Jonas Sjöberg

Abstract:
An efficient thermal energy management (TEM) system is crucial to extend the
driving range of battery electric vehicles (BEV). To assess/evaluate its performance
during development, a time-efficient simulation tool is needed. At China Euro Vehicle
Technology AB (CEVT), the developed TEM software is tested using GT-SUITE
simulations. It is a very accurate simulation tool, but computationally heavy and
time-consuming with an execution time in the magnitude of days. Therefore, CEVT
has developed an analytical plant model of the TEM system for a specific ambient
temperature. This model is however limited to one ambient temperature and not
compatible with measurement data collected from their physical car. Therefore,
this thesis aims to develop a generalized mathematical plant model of the thermal
system in BEVs, which captures the TEM system’s behavior at a larger ambient
temperature range.
The components in the proposed model are designed individually, such that the refrigerant
and coolant circuit can be tested separately in addition to the performance
of the complete TEM model. Inputs to the plant model are explicitly control signals
enabling the model to function independently of unavailable measurements from the
vehicle. Therefore, the pressure difference in the refrigerant circuit must be determined
using control signals. The pressure difference over the two expansion valves is
modeled using a modified version of the Bernoulli equation for a single short orifice
valve.
Simulation results show that the proposed model represents the system with captured
system dynamics. Reasonable errors are present in the simulation, and the
model finds a new stable equilibrium point to operate at. All verified temperatures
show model outputs in an acceptable RMS range, indicating the model accomplishes
the aim of being general.

Welcome!

Julius, Hanna, and Jonas