Design and Verification of Control Systems for Safe and Energy-efficient Vessels with Hybrid Power Plants

This D2V project is about the development of knowledge and competence on the design and verification of control systems for safe and energy-efficient vessels with hybrid power plants. Traditionally, a marine power plant consists normally of several diesel-generator sets connected to an AC or DC distribution system (power bus), separated by bus-tie breakers. In a hybrid marine power plant, the generators are assisted by the presence of energy storage devices (ESDs) such as batteries, super-capacitors, and fly wheels. We have in particular been investigating the potential to use batteries. ESD is a device that can charge up and store energy and deliver it on demand. As within the automotive industry, hybrid power plants on ships will improve safety and energy efficiency, since it can be used to reduce fuel consumption, emissions and power fluctuations. The project partners are NTNU, Kongsberg Maritime and DNV GL. The project has also been associated to the Centre of Excellence NTNU AMOS. The project covered 6 PhD studies on: Modelling and control of hybrid marine power plants including energy management; Transient performance and emissions of a turbocharged diesel engine for marine power plants; Scenario- and optimization-based control of marine electric power systems; Optimization-based control of diesel-electric ships in dynamic positioning; Hybrid electric power systems for dynamic positioning vessels: modelling, control and fault-tolerance; and Safety assessment and verification of advanced maritime systems. Several MSc theses were also associated to the project. The project results are published broadly at recognized international peer-review journals and conferences. A marine power plant simulator is developed as a part of the project, and associated to the project a marine hybrid power laboratory is also developed and used for model verification purposes. Electrical power plants with a set of diesel-generator sets segregated on several power buses have become the preferred solution for ships with a variation in operational profile and corresponding power demands. Examples of such ships are dynamically positioned (DP) vessels with electric power plants in the range of 10-80 MW used in the offshore oil and gas industry for various service, drilling, intervention and production operations. The operations are characterised as safety-critical and will take place all-year with large variations in the environmental loads acting on the ship due to wind, waves, ocean currents, and recently more operations in sea-ice. By proper design and control systems significant fuel savings can be achieved making the ships greener and safer. Redundancy and segregation are used to increase the overall safety by having more generators, buses, thrusters, and associated electrical equipment connected than what is strictly required by the total load, as well as physically and electrically segregating the equipment and cabling into different branches and zones of the ship. Any single fault on the redundant system should not lead to blackout, that is, a total loss of power. A contradiction may occur while optimizing both safety and fuel consumption. Unfortunately, safety-motivated minimum redundancy requirement far too often leads to operating conditions for the engine outside the optimal operating point, increasing fuel consumption and thereby the gas emissions. The introduction of improved generator protection systems, ESDs and smarter control systems may change this into a far better operation condition for the power plant and enabled engines. Even though marine operations and shipping are the most efficient transportation in terms of tons of goods per energy equivalent, the potential to improve fuel efficiency and reduce emissions are significant. The power and energy management system controlling the electrical power distribution, start and stop of generators, and the loads for propulsion, crane, drilling, ventilation, etc., is crucial in order to ensure safe and efficient operations. Successful operations of electrically powered vessels depend on advanced integrated software control functionality. Consequently, non-proper power plant designs and software-related problems, often in conjunction with hardware and/or human errors, may lead to unacceptable risk, increased gas emissions to the environment, and unwanted downtime during the operation. The associated loss of revenue and increased cost for the clients can be severe. Improved methods for testing and verification of hardware and software are important using improved simulation technology as well as laboratory testing. The trend in the maritime industry is towards increased level of autonomy. This will put even more requirements on relevant and effective testing methodology in a lifecycle perspective.

Objectives of the project: oGreener vessels: to develop new technology for safe and energy-efficient control of production, and consumption of electric power. o Safer vessels: to develop improved verification methods and procedures for reducing risks in n ew complex control systems. oProof of concept with pilot studies: The academic research carried out in Greener and Safer vessels will be prepared for pilot tests in order to check that the research can be applied in an industrial context. In addition t he project will increase the knowledge and awareness of operators and end clients (vessel owners, oil companies and other stakeholders) to critical issues regarding the technology and operation of complex marine vessels with electric power plants.