Shipboard Power System Research Articles

Development of Three-Phase Unbalanced Power Flow Using PV and PQ Models for Distributed Generation and Study of the Impact of DG Models

With the increased installations of distributed generators (DGs) within power systems, load flow analysis of distribution systems needs special models and algorithms to handle multiple sources. In this paper, the development of an unbalanced three-phase load flow algorithm that can handle multiple sources is described. This software is capable of switching the DG mode of operation from constant voltage to constant power factor. The algorithm to achieve this in the presence of multiple DGs is proposed. Shipboard power systems (SPS) have other special characteristics apart from multiple sources, which make the load flow difficult to converge. The developed software is verified for a distribution system without DG using the Radial Distribution Analysis Package (RDAP). The developed software analyzes an IEEE test case and an icebreaker ship system. System studies for the IEEE 37-node feeder without the regulator show the effect of different models and varying DG penetration related to the increase in loading. System losses and voltage deviations are compared.

Fault Detection, Diagnostics, and Prognostics: Software Agent Solutions

Fault diagnosis and prognosis are important tools for the reliability, availability, and survivability of navy all-electric ships (AES). Extending the fault detection and diagnosis into predictive maintenance increases the value of this technology. The traditional diagnosis can be viewed as a single diagnostic agent having a model of the component or the whole system to be diagnosed. This becomes inadequate when the components or system become large, complex, and even distributed as on navy electric ships. For such systems, the software multiagents may offer a solution. A key benefit of software agents is their ability to automatically perform complex tasks in place of human operators. After briefly reviewing traditional fault diagnosis and software agent technologies, this paper discusses how these technologies can be used to support the drastic manning reduction requirements for future navy ships. Examples are given on the existing naval applications and research on detection, diagnostic, and prognostic software agents. Current work on a multiagent system for shipboard power systems is presented as an example of system-level application.

Probability-based predictive self-healing reconfiguration for shipboard power systems

The electric power systems in US Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. During battle, various weapons may attack a ship causing severe damage to the electrical system on the ship. This damage can lead to de-energisation of critical loads which can eventually decrease a ship's survivability. It is very important therefore to maintain the availability of power to the loads that keep the power system operational. There exists technology for ships that can detect incoming weapons. This knowledge can be used to determine reconfiguration actions which can be taken before the actual hit to reduce the damage to the electrical system when the weapon hits. Then reconfiguration for restoration can be performed after the hit to reconfigure loads de-energised by the damage from the hit. A new automated probabilistic predictive self-healing methodology to determine such reconfiguration control actions is presented. Implementation of these actions will lead to less damage caused by a weapon hit and can considerably improve a ship's chances of surviving an attack. This probabilistic approach entails three major functions: weapon damage assessment, pre-hit reconfiguration before a weapon hit for damage reduction and reconfiguration for restoration after a weapon hit to restore de-energised loads. A case study is presented to illustrate the new methodology.

Distributed simulation for power system analysis including shipboard systems

Power systems are distributed in nature. Often they can be divided into sections or groups and treated separately. Terrestrial power systems are divided into separate utilities and are controlled by different regional transmission organization (RTO). Each RTO has detailed data for the area under its control, but only limited data and boundary measurements of the external network. Additionally, shipboard power systems may be divided into sections where local information is kept but not distributed to other parts of the system. Thus, performing a comprehensive power system analysis in such a case is challenging. Also, simulating a large-scale power system with detailed modeling of the components causes a heavy computational burden. One possible way of relieving this problem is to decouple the network into subsystems and solve the subsystems respectively, and then combine the results of the subsystems to get the solution. The way to decouple the network and represent the missing part will affect the result greatly. Also, due to information distribution in the dispatch or data centers, a problem of doing power system analysis with limited available data arises. The equivalent for other networks needs to be constructed to analyze the power system. In this paper, a distributed simulation algorithm is proposed to handle the issues above. A history of distributed simulation is briefly introduced. A generalized coupling method dealing with natural coupling is proposed. Distributed simulation models are developed and demonstrated in the virtual test bed (VTB). The models are tested with different network configurations. The test results are presented and analyzed. The performance of the distributed simulation is compared with the steady state and time domain simulation results.

A Wide Area Differential Backup Protection Scheme For Shipboard Application

A new wide area differential protection (WADP) system is proposed to suit the need of the shipboard application where short cables make conventional backup schemes impractical. The close proximity of all the components in a shipboard power system makes communication less of an issue than in a land-based system. With an overall view of the protected system and by use of a differential search algorithm, a minimum fault isolation area is decided. A built-in confirmation mechanism avoids unnecessary or false tripping due to protection component failure. The principle of the WADP system is described in detail in this paper. Simulation results are shown for a small Shipboard Power System (SPS).

Expert-system method for automatic reconfiguration for restoration of shipboard power systems

The electric-power systems in US Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. Faults in a shipboard power system (SPS) may occur owing to material casualties of electrical components or widespread faults owing to battle damage. These faults may interrupt the supply of electrical energy to loads that are not faulty or damaged. To enhance survivability of naval ships and meet reduced manning requirements, automatic reconfiguration for service restoration may be performed to restore the de-energised loads. The paper presents an automatic rule-based expert-system method for reconfiguration of electric-power systems on naval ships which determines the control operations necessary to restore power supply to de-energised loads after battle damage or cascading faults. A case study is presented to illustrate the effectiveness of the proposed method.

Geographical Information Systems for Automation of Shipboard Power Systems

The geographical information system (GIS) is a computerized system designed to capture, store, process, analyze and manipulate characteristic and spatial data. Shipboard power systems consist of components which are spread across the ship and are located at different geographical locations. This paper presents the design and development of a GIS modeling methodology for shipboard power systems and discusses some applications that use GIS models for shipboard power systems.

Self-Healing Reconfiguration for Restoration of Naval Shipboard Power Systems

Naval shipboard power systems form a critical component of the U.S. defense infrastructure. When there is a fault in a shipboard power system either due to battle damage or material casualty, it is important to quickly isolate the fault and restore supply to as many loads as possible. This paper presents an automated self-healing strategy for reconfiguration for service restoration in naval shipboard power systems. The proposed method is illustrated on a system developed based on a typical surface combatant ship.

Service restoration in naval shipboard power systems

Service restoration is an important problem in naval shipboard power systems. When faults occur as a result of battle damage or equipment failure and are isolated by protective devices, some critical loads are left without supply. Fast restoration of supply to these vital loads is necessary for system survivability. Loads have different priorities that must be considered during restoration in the shipboard power systems (SPS). These loads are categorised as vital or non-vital. Vital loads have two paths through which they can be supplied. Under some circumstances, it may be preferred to supply a vital load through one of the two paths. Butler et al have developed a method to restore maximum loads in SPS based on the fixed-charge network flow method. An enhancement to their method is proposed to handle priority for loads and paths while restoring service in SPS. The proposed method is illustrated with some case studies on a simplified SPS.

Shipboard power restored for active duty

Network reconfiguration for restoration in a military shipboard power system is a very important task that is performed in order to restore loads as a result of battle damage or system faults. This article features an expert-system-based reconfiguration methodology for load restoration in shipboard power systems. The power system considered in the present study is based on the layout profile of a US surface combatant ship. The methodology developed will determine whether the loads that lost supply are restorable. When considering loads, it gives precedence to high priority loads. It also determines if there is any violation of current constraints of any cables and voltage constraints at load nodes. If the load is restorable, as suggested by an expert system, and there is no violation of any constraints, then the load is said to be restorable and the operation sequence required in restoring that load would be given as the output. A CAD drawing of the power system and a database of the system information has been developed using a geographic information system (GIS). A software tool incorporating failure assessment and expert system restoration methodology was developed using Visual C++, Multilogic Exsys Developer, Alternate Transients Program (ATP), and Microsoft Access. Microstation has been used for GIS. Various fault cases were designed, and the developed tool was used to run them and perform expert system restoration.

Network Reconfiguration for Service Restoration in Shipboard Power Distribution Systems

The electric power systems of U.S. Navy ships supply energy to sophisticated systems for weapons, communications, navigation, and operation. Circuit breakers (CBs) and fuses are provided at different locations for isolation of faulted loads, generators, or distribution system from unfaulted portions of the system. These faults could be due to widespread system fault resulting from battle damage or material casualties of individual loads or cables. After the faults and subsequent isolation of the faults, there will be unfaulted sections that are left without supply. Fast restoration of supply to these unfaulted sections of the shipboard power system (SPS) is necessary for system survivability. This article presents a new method to reconfigure the network to restore service to unfaulted sections of the system. The problem is formulated as a variation of the fixed charge network flow problem. The method is illustrated using various case studies on a small power systems with topology similar to a shipboard power system.

Analysis of tools for simulation of Shipboard Electric Power Systems

Abstract Navy Shipboard Power Systems have different characteristics when compared with utility power systems. To conduct system studies on shipboard power systems, an effective simulation tool is required to model the Shipboard Electric Power Systems. This paper presents the results of the analysis of three popular simulation tools, ATP, PSpice and Saber for transient simulation of Shipboard Electric Power Systems (SPSs). The results suggest that ATP is a good tool for generating detailed component models and calculating model parameters directly from standard specifications and ratings of the equipment. PSpice and Saber have an excellent graphical interface for building complex SPSs and flexibility in establishing monitoring points and processing output data.

A novel Power Systems program at the Naval Postgraduate School

The Power Systems program at the Naval Postgraduate School is a unique academic endeavor which seeks to both educate Navy officers in relevant advanced technologies and to complement the research efforts on-going at the government laboratories. The move toward incorporating more-electric technology into naval combatant shipboard power systems and the requisite analysis of such finite-inertia, stiffly-connected systems have driven the development of a program that intermixes power electronics, electric machines, and microprocessors. Through work emphasizing analysis, hands-on hardware investigation and simulation, the students are exposed to the diverse issues encountered in power system research. The students are also presented unique opportunities to interact on-site with various government laboratory sponsors to further draw the connection between theory and hardware implementation.

Current and voltage controlled capacitor charging schemes

Future naval shipboard power systems for electrothermal chemical guns will require power conditioning to charge capacitors from a rectified generator source. This paper describes results of laboratory testing involving two low voltage capacitor charging schemes. These experiments demonstrate the power conditioning equipment's voltage and current control characteristics. The first sequence of tests utilized a phase-controlled rectifier to control the current. A series of constant phase delay angles and a predetermined phase delay angle profile were tested to produce a constant current charge on the capacitors. The second sequence utilized generator field control to ramp the charge voltage through a diode bridge to charge the capacitors. Using the results of each configuration, an optimum design of simultaneous current and voltage control can be developed. The control aspects of using combined generator field control and rectifier current control is addressed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

THE 400 HERTZ DILEMMA

ABSTRACTSince the advent of the modern combat system and use of sophisticated avionics test equipment, there has evolved an ever increasing problem in interfacing these loads to the normal Type I/Type II shipboard power system. This paper addresses past initiatives which led to a proliferation of motor‐generators in the fleet; the current major interface problems which have led to degraded performance of the ship service power system as well as the systems serviced, and makes recommendations to reverse the incompatibility. In order to ensure that the interface problem is understood, several specific current system problems are described and impending future potential problems assessed. The by‐product of this dialogue should be a better understanding of the interface problems which can occur in electrical and electronic systems and subsystems when early attention is not given to overall ship system design of both the power generation system and mission‐oriented payload systems and subsystems.

Transient performance of D-C machinery — I

PREVIOUS STUDIES HAVE STRESSED the need for more accuracy in the calculation of transient currents than is provided by present methods. For the design of shipboard power systems, these methods are not sufficiently accurate and do not adequately reflect the influence of initial conditions of load, voltage, and speed on peak currents. There was also a disappointing lack of experimental verification of the important assumptions upon which the theoreticians were proceeding. Before developing a new approach or following a published calculation, it becomes evident that the limitations of any relations are determined by the validity and accuracy of the assumptions employed. It is concluded from this work that a more fundamental knowledge of the internal phenomena of rotating machinery is required before developing relations describing transient response of a d-c machine within design accuracy. Flux variations are fundamental to machine behavior in that they govern generated voltage, leakage fluxes, commutation, coefficients of induction, and eddy currents.