Session: 06-04-01 Marine Engineering and Technology I

Paper Number: 121041

121041 - Modeling and Controller Design for Hybrid Ship Power and Propulsion Systems With Shaft Generator 

The marine diesel engine works well for ships operating at designed speed for most of their lifetime, but for ships frequently switching between different operational modes, part-load conditions of the engines are not desired due to low fuel efficiency and high emission. In this case, the shaft generator can function as a pivotal link bridging the mechanical propulsion system and the electric power system. Advantages of shaft generator implementation are discussed in literature [1].

This paper proposes a novel modeling and control approach for the hybrid power and propulsion system of a line-fishing ship M/S Geir, comprising an electric power system with auxiliary genset, shaft generator, and a battery set integrated, a main diesel engine, a gearbox, and a controllable-pitch propeller. The electrical system in our study is constructed using a power-based electrical bus, as well as simplified generator and converter models. The bidirectional drive can operate the shaft generator both in generator and motor mode, converting and transferring power between the mechanical shaft and the electrical grid. The diesel engine is modeled using a first-order system with time delay to mimic its dynamics. The open-water characteristics of the controllable-pitch propeller are used to model the propeller behavior. The control system design and modeling of the hybrid system are analyzed through case studies, where the adoption of shaft generator enables hybrid propulsion including mechanical, PTI, PTO, Boost mode.

The mechanical mode is mostly used for ship navigation with the main engine operating around the design point. In PTO mode, the shaft generator uses the shaft’s rotational motion to generate electricity, with a frequency converter supplying three-phase current to the bus. This enables the main engine to operate with heightened efficiency even under partial-load conditions, thereby bolstering overall performance. In PTI/Boost mode, the shaft motor reverses its operation to transfer energy in the opposite direction, driving the main propeller. The difference lies in the operational context: in PTI mode, the main engine disengages, while in Boost mode, the electric motor supplements the shaft system, ensuring the ship can maintain high speeds even in adverse weather conditions. PTI mode is desirable for low-speed operation or as an emergency backup machinery to propel the ship if the main engine goes out of operation. Specifically for M/S Geir in case study, PTI mode is predominantly utilized during berthing maneuvers (5% of the time) and when hauling lines (95% of the time).

The control strategies for grid-connected operation of the shaft generator have been presented in [2] and [3], but the detailed efficiency modeling content is absent. Additionally, [4] introduced an electrical system with shaft generator aimed at improving fuel efficiency, albeit with a simplified propulsion model and without providing an explicit efficiency model for the hybrid propulsion system. In our paper, we will bridge these gaps by offering a comprehensive approach that focuses on efficiency and dynamic modeling, and control techniques, for an integrated marine power and propulsion system that includes a shaft generator.

 

References

 

[1]

A. Sarigiannidis, A. Kladas and E. Chatzinikolaou, "High efficiency Shaft Generator drive system design for Ro-Ro trailer-passenger ship application.," in International Conference on Electrical Systems for Aircraft, Railway, Ship Propulsion and Road Vehicles (ESARS), 2015.

[2]

Y. Langtao, T. Jiawan, L. Yusheng and Y. Hui, "Modeling of Marine Asynchronous Shaft Generator and Simulation of Subsynchronization State.," Mathematical Problems in Engineering, pp. 1-11, 2020.

[3]

S. Li, P. Yang, L. Liu, L. Chen, L. Bi, G. Cui and C. Zhang, "Research on grid-connected operation of novel variable speed constant frequency (VSCF) shaft generator system on modern ship.," in 15th International Conference on Electrical Machines and Systems (ICEMS), 2012.

[4]

A. G. Sarigiannidis, E. Chatzinikolaou, C. Patsios and A. G. Kladas, "Shaft generator system design and ship operation improvement involving SFOC minimization, electric grid conditioning, and auxiliary propulsion.," IEEE Transactions on Transportation Electrification, pp. 558-569, 2016.

Presenting Author: Fan Gao Norwegian University of Science and Technology

Presenting Author Biography: Fan Gao is a PhD candidate at the Norwegian University of Science and Technology (NTNU) with a passion for advancing energy-efficient maritime solutions. Her research focuses on pioneering optimization methods for hybrid ship propulsion systems, with a primary focus on enhancing fuel efficiency and minimizing environmental impact. She also has the background with underwater technology in mission planning and replanning, path planning and collision avoidance for ROVs.

Authors:

Fan Gao Norwegian University of Science and Technology
Astrid H. Brodtkorb Norwegian University of Science and Technology
Mehdi Zadeh Norwegian University of Science and Technology
Sigrid Marie Mo Brunvoll AS