Comparison Between Ring and Radial Configurations of the University of Trieste Campus MV Distribution Grid

Distribution systems are being pushed towards smarter architectures, management strategies, and controls. To develop new platforms and algorithms for distribution systems management, the University of Trieste is using its medium voltage MW-scale ring distribution system as a demonstrator. In addition to the installation of a real-time monitoring system, power system studies and analyses are required. The paper presents and compares some results concerning the power system operation in both closed (normal operation) and open (post fault operation) configurations, where the latter are identified by means of a quantitative dependability analysis. In particular, the voltage profile, the currents, and the losses in the system are studied, evaluating the impact of faults capable of opening the ring

Design of Zonal Electrical Distribution Systems for Ships and Oil Platforms: Control Systems and Protections

Complex energy vessels such as large platforms or drillships require more efficient use of electrical power. As shipboard electrical systems become larger, problems and limits arise with the ac distribution architecture. Hybrid ac/dc onboard distribution systems are today available, which provide higher efficiency and redundancy. IEEE Std. 1662, 1709 and 1826 set technical rules and recommendations for the design of hybrid ac/dc shipboard electrical systems. Among these, zonal electrical distribution systems (ZEDS) are considered a next technological evolution, as they provide optimal power sharing (and energy storage) along with high reliability

Impact of Fuel Switch to Methanol on the Design of an all Electric Cruise Ship

Current climate change policies require the reduction of both greenhouse gas and pollutant emissions of the marine sector. To achieve such a goal, the use of non-fossil fuels is one of the proposed solutions. Specifically, methanol has several advantages in respect to other fuels (both fossil and non-fossil), providing a feasible near-term solution for a more sustainable maritime transport. However, since methanol presents different characteristics in respect to actual fossil fuels, it is required to carefully evaluate the effect of its onboard integration on a ship to determine both the technical and economic feasibility of transitioning the onboard power production to such a fuel. The study presented in this paper analyzes the consequences deriving from equipping a modern all electric expedition cruise ship with methanol fuel, considering both technical and economic aspects

Reactive Power Resources Management in a Voltage Regulation Architecture Based on LQRI Control

The Italian transmission system's voltage control is based on its subdivision into decoupled control areas, where a hierarchical regulation architecture is applied. However, the structure and the voltage regulation of the electrical power system are being significantly impacted by the actions being taken to limit climate change. The increase in renewable energy sources exploitation is leading to a more-distributed and converter-based energy production. In addition, the forthcoming coal-fired plants shut-off will force the shift from providing regulation capability with a small number of big power plants, towards using a big number of smaller resources. Thus, in the near future a decrease in the effectiveness of the present voltage control architecture is expected. To solve such issue, a new voltage control architecture is needed, involving the more-distributed and converter-based energy production systems, as well as no longer relying on physically decoupled control areas. Therefore, in this paper a coordinated LQRI secondary voltage control is presented, able to use each grid-available reactive power source as an actuator. Furthermore, a bumpless transfer technique is proposed to solve the problem of managing a varying number of actuators (due to the reactive power resources' connection and disconnection)

Study on the State Feedback Selection and Measurement for the Application of an LQRI Secondary Voltage Regulator to a Transmission System

The electrical power system is being significantly affected by the climate change mitigation actions. The power generation, originally centralized, is transitioning towards a more decentralized paradigm due to the coal-fired power plants shut off and the increase in renewable power. Issues in transmission system's voltage control may arise, if the voltage regulation architecture is not modified accordingly. To this aim, in this paper it is investigated the use of a Linear Quadratic Regulator with Integral action (LQRI) for the secondary voltage regulation, aimed at exploiting several reactive power sources as actuators. Being the LQR class of regulators requiring the system state to correctly operate, and being a transmission system a complex system, a critical investigation must be done. In particular, it is needed to identify the variables that are directly measured in a real system, determine if they can be useful for the LQRI state feedback, and finally study the effect of the different possible feedback selection on the regulation performance

Feasibility Study of a Modular Multi-Purpose Frigate with an Integrated Power & Energy System

This paper presents a feasibility study of a modular multi-purpose frigate with an integrated power and energy system (IPES) and a Combined Diesel Electric and Gas (CODLAG) propulsion system. The modular design offers greater flexibility, enabling the vessel to perform a wider range of missions thanks to innovative hull form and a large capacity for carrying a containerized payload. The study evaluates also the feasibility and potential benefits of two possible configurations for the Energy Storage System (ESS) integration in the onboard IPES, enabled by the specific ship design. The utilization of peak shaving technology reliying on supercapacitors has a limited impact on the ship in terms of weight and volume, thus being the most appropriate solution for CODLAG frigates. Conversely, Li-ion batteries can enable zero-emission mode. A large ESS capacity can be integrated onboard in the available weight and volume margins (enabled by the specific ship design), aimed at improving energy efficiency in port, manoeuver, and combat modes (by avoiding non-optimal load rates on generators)

A review on energy efficiency in three transportation sectors: Railways, electrical vehicles and marine

The present paper is a review on efficiency issues related to three important sectors of the transportation systems: railways, electrical vehicles, and marine. For the three sectors, the authors, in reference of their knowledge and research area, show the results of a wide literature analysis, in order to highlight which are the measures, in terms of technological solutions and management techniques, which are recently investigated and implemented, for improving the three transportation systems, from the point of view of efficiency. In particular, for the railway transportation sector, a wide analysis is presented, detecting which are the main measures adopted for improving the efficiency, related to the power systems for supplying trains and to the train traffic control, with a focus on the storage system integration. For electric road vehicles the analysis is focused on the plug-in electrical vehicles and on the infrastructure for their recharge, with an emphasis on how these vehicles can support the grid, e.g., through Vehicle to Grid (V2G) applications. Finally, for the marine transport service the review is related to the propulsion systems and on how the different solutions can meet the objective of efficiency

Dependable design of all electric ships integrated power system: New design process

All Electric Ships (AESs) are becoming a standard for what it concerns large ships with large power requirements (for both propulsion and onboard loads). At present, the design of shipboard complex power system (namely the IPS - Integrated Power System) is done through a well-proven process, relying on historical data and trial-and-error procedures developed in nearly 30 years of design experience. However, the evolution in shipboard power systems (mainly due to more demanding requirements on Quality of Service and safety) is pushing towards new IPS architectures and subsystems, not covered by previous knowledge. Due to that, the conventional design process is becoming inefficient, thus demanding new design paradigms. In this regard, innovative concepts and tools can be adopted to achieve a "new design process". In this paper, after a brief analysis of conventional design process, a proposal about such a new design process is done, integrating both dependability theory and the dynamic power system simulators. Insights about its inclusion in conventional design process are also given, together with an application example, used to show the effectiveness of such a new process

Equivalent Inductance Evaluation for Cable Bundles in Shipboard Integrated Power and Energy Systems

Nowadays, the Integrated Power and Energy System (IPES) is no more a marginal part of the ship and the electrical equipment arrangement is becoming increasingly difficult. Indeed, an all-electric cruise ship has 65 km of cable trays and more than 4000 km of power cables to supply all the shipboard electric loads. In this scenario, the cable layout in the cable tray is not considered during the early stage design phase. Nevertheless, different cable arrangements can have undesired effects on the power line parameters. Thus, in this paper a Python code is compared to two different Finite Element Method (FEM) software to assess its effectiveness in calculating the inductance matrix considering the power line arrangement in the cable tray. Secondly, two methods are used to determine the equivalent inductance and evaluate its dependence over the cable layout. It is shown that the effect of cable arrangement in the cable tray on the power line equivalent inductance is not negligible and it should be taken into account in the early stage design phase

Dependability Analysis of a Digital Excitation Control System

The synchronous generators' excitation is usually regulated by means of a real-time digital control system, while other apparatuses are dedicated to secondary functions (e.g human machine interface, remote control unit, logic and control functions). A performance increase and a cost reduction can be achieved by integrating all the functions into a single platform. However, this requires assessing the dependability performance of the control systems currently in use, to set a base benchmark for future evaluations. In this paper, the quantitative dependability analysis of a digital excitation control system is performed, by using as a case study a real system installed in a hydroelectric power station. Two configurations are analyzed, and their dependability performance are compared