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Abstract
The next generation Anti-Submarine Warfare Frigates (ASWF) of the Royal Dutch Navy is currently under
development. With these new vessels, the navy aims to enhance its capability to continue structural long-term
deployments. Besides facilitating directed-energy weapons and a high powered sensor suite, the vessels will
also embrace a sophisticated signature management system. These technologies require a highly efficient and
smart electric power generation and distribution system and the new vessels will therefore be equipped with DC
distribution grids and variable speed generator sets. While variable speed generator sets offer increased efficiency
and control possibilities compared to fixed speed generators, they may suffer from the lower dynamic performance
of the internal combustion engine driving the generator at variable speed. Depending on the engine’s operating
point within the operating envelope, a sudden load change might not only demand an increased torque from
the engine but also an increased rotational speed. Increasing the engine speed simultaneously requests additional
torque and can push the engine beyond its operational envelope, causing increased emissions of particulate matter,
high thermal engine loading or even compressor surging in the turbocharger. Since DC distribution grids do not
require a fixed grid frequency, larger transient tolerances of engine speed are allowed. Especially in combination
with Energy Storage Systems (ESS), DC distribution grids might be able to handle larger sudden load increases
compared to classical AC distribution grids. In this paper, we address the implications of DC distribution grids
and variable speed generation on the internal combustion engine with an emphasis on the dynamic response
characteristic of the engine. The study investigates different strategies for load sharing in combination with an
ESS to improve the dynamic response characteristic. We will discuss the effects of these load sharing strategies
on the air-excess ratio and thermal loading, aiming for a reduction in the emission of particulate matter and
soot, and a reduction in engine degradation. For this study, experiments on a variable speed generating set were
conducted and combined with simulation experiments with an extended Mean Value First Principle (MVFP)
engine model. Our results indicate that the dynamic response characteristics of the engine can be improved
by carefully considering the load sharing strategies of the ship’s electric power distribution system. Moreover,
emissions of particulate matter and soot, as well as exhaust gas temperatures, can be reduced, decreasing the
signatures of the vessels.