Optimal Transient Control Trajectories in Diesel-Electric Systems-Part 1: Modeling, Problem Formulation and Engine Properties
A non-linear four state-three input mean value engine
model, incorporating the important turbocharger dynamics,
is used to study optimal control of a diesel-electric powertrain
during transients. The optimization is conducted for
the two criteria, minimum time and fuel, where both engine
speed and engine power are considered free variables in the
optimization. First, steps from idle to a target power are
studied and for steps to higher powers the controls for both
criteria follow a similar structure, dictated by the maximum
torque line and the smoke-limiter. The end operating point,
and how it is approached, is however different. Then the
power transients are extended to driving missions, defined
as, that a certain power has to be met as well as a certain
energy has to be produced. This is done with both fixed output
profiles and with the output power being a free variable.
The time optimal control follows the fixed output profile even
when the output power is free. These solutions are found
to be almost fuel optimal despite being substantially faster
than the minimum fuel solution with variable output power.
The discussed control strategies are also seen to hold for sequences
of power and energy steps.
Martin Sivertsson and Lars Eriksson
Journal of Engineering for Gas Turbines and Power,
2015
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