PhD Thesis - Cranfield University

Chapter 2
Power
Load Demand
Time
Power Power
30
Power & Energy Management
Power from Type 1 ESS
Power from Type 2 ESS
Figure 2.3 Power split and energy expenditure between two energy sources
Time
Time
State of Charge
Energy level of Type 1 ESS
State of Charge
t
Energy level of Type 2 ESS
This vexing issue of controlling the power flow of two or more sources has been addressed
through various approaches. Jalil, Kher and Salman [19] suggested a rule-based framework
for power split between a battery pack and an internal combustion engine. The proposed
strategy ensured that both power sources operate at maximum efficiency whenever possible.
The concept demonstrated an increase in efficiency in terms of fuel economy. Recognising
that the battery energy expenditure as well as the system power split requires a controlled
intervention, Caratozzolo, Sera and Riera [20] also suggested an energy management
strategy derived from a heuristically composed rule-base. Due to the highly non-linear nature
of EV and HEV drivelines, the authors suggested a rule-base approach to provide an
employable scheme for arbitration of power flow under various operating modes of the
vehicle.
Steinmauer and Del Rel [21] stated that techniques that use a fixed controller structure and
then searches for optimal parameters to minimise a cost function yields only a solution that
is a consequence of the selected structure. They proposed to tackle the dual source power
split problem in terms of optimal control using statistical data of vehicle power demands for
known drive cycles. Their procedure addressed the problem by deriving optimal solutions
for a fixed set point, which was then extrapolated to various power demand profiles. The
authors demonstrated optimal power split between a battery and generator. The analysis
t