Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Modeling and control of ship propulsion with shaft generator and battery storage system
Fan Gao, Astrid H. Brodtkorb, Mehdi Zadeh
Department of Marine Technology, Norwegian University of Science and Technology (NTNU).
Trondheim, Trøndelag, Norway

propeller (CPP) (Carlton, 2018) can be formulated as the optimization ofa cost function. For example, many marine propulsion control systems
focus on reducing fuel consumption and avoiding cavitation at thepropellers. The combinator curve set used in this report is optimized for
maximizing efficiency. The optimal setpoints of propeller pitch and shaft
speed are chosen from the optimal combinator curve and are controlledindependently.

ABSTRACTThe use of shaft generators in marine applications makes it possible tooperate the main engine more efficiently and to provide additional power
to the electrical system. This paper develops a dynamic model andcontroller for a hybrid marine propulsion system that operates efficiently
in both mechanical and hybrid modes such as power take-off (PTO). A
simplified electric power system model with a shaft generator and abattery set is introduced into the ship propulsion system. The
corresponding control and switching logics are also described and areproved with simulations.

KEY WORDS: Ship propulsion; shaft generator; controllable -pitchpropeller; mode switching; marine batteries.
INTRODUCTION
Nowadays, hybrid ship propulsion systems are of great interest and theapplication of shaft generators (SGs) has developed rapidly. The
operation mode of a hybrid ship propulsion system can include power
take-in (PTI), power take-off (PTO), and boost mode (Sui, de Vos,
Stapersma, Visser, and Ding, 2020). In this paper, we investigate the useof optimal combinator curves for the control of a hybrid ship propulsion
system driven by an engine with and without a shaft generator.

Figure 1. Simplified diagram of the ship hybrid powertrain.

For marine applications, the main propeller can be driven by the engine,
and the shaft generator can be engaged to charge the battery set and/orpower the electric bus (PTO mode). Using the shaft generator system tocharge the battery is more efficient than starting auxiliary engines (Liu,Xue, and Ye, 2007; Prousalidis, et al., 2012; Sarigiannidis, Kladas,
Chatzinikolaou, and Patsios, 2015). Fig. 1 shows an overview of theproposed propulsion system, which consists of a main diesel engine (DE),a controllable pitch propeller, and a shaft generator (SG) connected tothe electric system (EL).
Since many combinations of shaft speed and propeller pitch can produce
the same thrust, the propulsion control problem with controllable pitch

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Mathematical modeling of marine diesel engines is performed withvarying fidelity for different purposes. For the purpose of higher level
controller simulation and testing, Fossen (2011) models the prime moversystem as a first-order transfer function with a time delay. The control
input to the engine system can be the fuel injection for the diesel engine
or the power required for the electric propulsion system to produce thedesired torque. These models do not account for the dynamics of marine
power systems. For diesel engines, load control is achieved by changing
the fuel injection in each cycle. Vrijdag and Stapersma (2017) explain
the reason for the time delay in engine modeling, claiming that theconversion from fuel injection command to actual fuel injection takes amaximum of two revolutions for a four-stroke diesel engine. Altosoleand Figari (2011) present three options for numerical modeling of marine
engines: Modeling using mathematical equations, numerical surfaces,and PI action. Altosole, Campora, Figari, Laviola, and Martelli (2019)present a high-fidelity model of the thermodynamic behavior of diesel