Zonal Distribution System Research Articles

Optimal‐droop voltage‐restorer for zonal dc distribution system with simultaneous consideration of dynamic current balance and power loss reduction

AbstractA dc voltage restorer (dc‐VR) with optimal droop control is developed to reduce the power loss and solve the dynamic current imbalance simultaneously of the zonal dc distribution system integrating multi‐parallel energy storage. Firstly, the power loss model composed of line loss and converter loss is built and it is proved to be a strictly convex function with respect to droop coefficients, which indicates the power loss can be mitigated by optimizing the current distribution. Thus, an image‐based droop optimization method is proposed to search for the optimal droop coefficients. Then, the economy of voltage compensation on power loss reduction is investigated and an ESS‐combined dc‐VR is designed, including an interleaved parallel architecture and a capacitor‐integrated electric spring (C‐ES). Unified virtual inertia is proposed for interleaved parallel bridge arms to make their dynamic performance consistent. And the newly introduced C‐ES can keep the bus voltage at the rated level to reduce the system cost. Therefore, the problem of dynamic currents imbalance is addressed from the points of converter structure (dc‐VR) and control system (unified inertia), and the power loss can be reduced by voltage recovery (C‐ES) and optimizing the current reallocation which is achieved by updating sharing coefficients from the image‐based droop optimization method. Finally, the simulation cases validate the effectiveness of the proposed optimal‐droop dc‐VR on dynamic current balance and power loss reduction, and hardware in the loop experiment results prove the consistent dynamic characteristics of the dc‐VR's arms.

Comparison of Radial and Zonal DC Distribution System for Hybrid-Powered Trimaran Vessels Power Flow Analysis

Two types of power grid structures have been applied to the shipboard, namely the radial and the zonal networks. These two distribution systems have different power characteristics transmitted to the bus panel. The power characteristics affect the power density of each bus at each level. This paper explores the power characteristics of the radial type and the zonal type power grid structures in a DC distribution system. The power flow of both distribution system types has been determined by the Adaptive Newton-Raphson method and simulated based on ship operation conditions using Electrical Power System Analysis Software (ETAP). In determining the power flow for the DC distribution system, one-line diagram modelling is developed in radial type and zonal type. The simulation parameters are adjusted to the operating conditions of the ship, namely sailing, manoeuvring, loading-unloading, and at the port. After that, a power flow simulation has been carried out using ETAP and has showed what had successfully implemented the power flow in the DC distribution system for radial and zonal types. The capacity of Power generation is adequate all through a ship operation. The characteristics of the transmitted power show that the zonal type has a higher efficiency rate than the radial type. The zonal type has a backup bus so that the electrical system's reliability is higher than the radial type. However, the power distributed to the equipment bus from the load bus, both the radial type and the zone type, has the exact power requirements.

An additional bus inductance-based protection scheme for shipboard DC zonal electric distribution systems

The shipboard DC zonal electric distribution system (DC ZEDS) has seen a recent explosion of interest for its high reliability and strong survivability. With multiple sources and zones, however, the complicated structure brings challenges to its protection design, in which the breaker coordination is one of the key issues. In this regard, this paper proposes a protection scheme based on the additional bus inductance (ABI) for the shipboard DC ZEDS, which meets the requirements on speed, selectivity and reliability in shipboard protection. The breaker configuration is analyzed based on the structure characteristics of DC ZEDS, and the breaker coordination is addressed from transverse and longitudinal directions. The ABI assists shipboard protection in identifying faults in different zones, improving operation speed and lessening fault severity. A reasonable simulation model has been built, in which breaker failures and different operation modes are considered. Simulation results are shown to verify the effectiveness and applicability of the proposed protection scheme. The sizing of the ABI is discussed in the paper to provide theoretical basis for engineering practice.

307.5: Deceased organ allocation and procurement of high risk organs in KSA (2013-2018).

Background: The organ donation is a need due to the huge gap between supply and demand. Proper identification and management of organs and determining prior conditions and/or pathology before and during organ allocation will help better assessment and judgment of the organs, thus improving the allocation process, organ acceptance and utilization by transplant centers. Objective: To evaluate the role of detection and allocation of high risk organs to improve the donation and utilization program in general. Methods: This retrospective study over a 6-year period from 2013-2018 of all consented brain death cases. Analysis of annual reports and collected SCOT data and also our dynamic cases study. Results: Over the 6-year period (2013-2018), a total of 3616 possible deceased donors were reported to SCOT. 2169 (60%) has been converted to potential donors. 1800 (83%) become eligible donors after family approached, 557 (31%) had been consented for organ donation and 539 (96.8%) consented donors were recovered. A total of 1,675 (70.6%) solid organs and 697 (29.4%) tissues were recovered. Organs recovered were, 787 transplanted kidneys, 56 kidneys (6.6%) were discarded mainly due to CKD and vascular diseases. 460 livers were recovered, wherein, 396 (86%) transplanted, 64 (14%) were discarded, 260 lungs were transplanted, with non-recovered lungs of 49%. 288 hearts were recovered of which, 113 (39%) transplanted and 175 recovered as source of heart for valves, and 53 pancreases were transplanted over the past 6 years. Deceased organ distribution and allocation is based on recipient priority criteria and zonal distribution system, following the Guidelines in the Directory of Regulations of Organ Transplantation. High-risk or marginal organs, such as 128 (18%) kidneys from extended criteria donors with the median age of 46 years and died due to CVA (63%) over the last 6 years, to prevent the delay of acceptance of these marginalized kidneys and improve its utilization, these kidneys were allocated to 5 transplant centers, 3 in central region, 1 in eastern and 1 in western which used to accept and transplant a marginal kidneys. Conclusions: Improving the deceased allocation and procurement of high risk organ requires a multifactorial approach which involves the cooperation between the doctors and surgeon in managing the high risk deceased donors. Improving the sharing of information on HLA cross-matching of the donors to all transplant centers. Giving recognition to these transplant centers and encouraging the ICU staff regarding the best practice of donor management and maintenance. Predicting organ pathology by providing medical imagery, such as ultrasounds, CT scans, bronchoscopy and heart echocardiograms prior organ allocation thus, improving organ allocation. Reconditioning and maintaining the marginal donors and organs and drafting a new regulation leads to more successful transplantation and less discarded organs.

Study of Shipboard Power Distribution System: Review on an Aplication of AC Zonal Distribution

The shipboard power distribution system has been developed in order to make it more efficient. AC zonal distribution system is one of the options in order to achieve the objection. This study aims to observe the shipboard application with AC zonal distribution system. The distribution system is modeled, simulated, analyzed, and compared with conventional system. Based on simulation, the AC zonal distribution system provide higher reliability, better power continuity, and more stable power generation. Therefore, development of the zonal distribution system continues to bring succeed in every mission. However, the system has several challenges for future work such as more complex transmission system, higher voltage drops, and the tendency to have instability power distribution when one generator fails.

Study of Shipboard Power Distribution System: Review on an Aplication of AC Zonal Distribution

The shipboard power distribution system has been developed in order to make it more efficient. AC zonal distribution system is one of the options in order to achieve the objection. This study aims to observe the shipboard application with AC zonal distribution system. The distribution system is modeled, simulated, analyzed, and compared with conventional system. Based on simulation, the AC zonal distribution system provide higher reliability, better power continuity, and more stable power generation. Therefore, development of the zonal distribution system continues to bring succeed in every mission. However, the system has several challenges for future work such as more complex transmission system, higher voltage drops, and the tendency to have instability power distribution when one generator fails.

Deceased Kidney Distribution and Allocation in the Kingdom of Saudi Arabia

Background The Saudi Center for Organ Transplantation (SCOT) is the sole supervising, regulating and coordinating body for organ donation and transplantation inside the Kingdom of Saudi Arabia. It is also the referral center for Gulf Cooperation Council (GCC) Countries and adopted the uniform law on regulation on organ sharing among GCC countries as guidelines. In deceased organ donation, kidneys from deceased donors is the most utilized organ in the kingdom, helping patients suffering from ESRD and improving their quality of life by means of kidney transplantation; Thus, we studied the distribution and allocation of these kidneys from the zonal distribution system to kidney allocation and its utilization. Methods & Materials A retrospective review was done during the period of 2014‐2016, using the Critical Pathway of Organ Donation comprising the potential, eligible, actual and utilized deceased kidneys inside the kingdom of Saudi Arabia. Results In 2014 to 2016 a total of 1,160 Potential Deceased Donors (DD) were recorded by SCOT, of which 944(81%) donor’s next of kin were approached for organ donation after declaration of death, and 313 (33%) had given their consent to donate the organs. A total of 626 kidneys were consented, of these 400 (65%) kidneys were transplanted (utilized) in KSA, 106 (17%) kidneys was also utilized by GCC countries including 2 kidneys shared by KSA to UAE, non-recovered kidneys were 96 (15%), while 24 (4%) kidneys were not utilized. In 400 kidneys transplanted in KSA, kidney donors were categorized using the Standard and Extended Criteria (SCD, ECD) and the Donors Kidney Donor Risk Index (KDRI). A total of 290 (72%) SCD kidneys and 110 (28%) ECD kidneys were transplanted while the kidneys transplanted from deceased donors with KRDI index of less than <0.8 were 17 (4%) kidneys, 0.8-1.15, 163 (41%), 1.15-1.45, 113 (28%) and >1.45, 107 (27%) with mean KDRI of 1.25. SCOT allocation protocol allotted 20% of SCD deceased kidneys to Pediatric recipients; in which, 70 kidneys were transplanted; wherein, 69 (99%) SCD kidneys including, 15 kidneys for urgent pediatric was transplanted, and 1 (1%) kidney from ECD donor. Kidneys transplanted for urgent recipient was implemented by SCOT through zonal distribution which amounted to 28 kidneys transplanted mainly due to loss of vascular access. The cold ischemia time (CIT) Ranges from 2 hrs – 34 hrs. with mean CIT of 12 hrs. Discarded kidneys inside the kingdom were 22 kidneys with most reasons are due to kidney related disease. Non-recovered kidneys 96, were mostly due to donor’s sudden cardiac arrest 52 (54%), followed by causes due to medical reasons 38 (40%) and technical reasons 6 (6%).Conclusion Kidney allocation and distribution is a vital role performed by SCOT. It assures, fair distribution of deceased kidneys to transplant centers based on recipient priority criteria and zonal distribution system following the Guidelines in the Directory of Regulations of Organ Transplantation. The SCOT constantly and closely monitor the kidney allocation for pediatric and patients on urgent waiting list were always given the priority. ECD kidneys were also used optimally by offering it to transplant centers thus, increasing the kidneys being utilized.

A Two-Level Topology Design Framework for Reliable Shipboard Power Systems

Ensuring a high level of service reliability is of paramount importance in an all-electric ship. In the literature, shipboard power systems (SPS) have been designed for improved survivability and quality of service (QOS) requirements. This paper presents a two-level topology design approach and develops system-level architectures for SPS that ensure continuity of service and survivability in the event of outage or failure. A reliable SPS architecture is obtained by (1) the choice of topology, (2) optimally placing equipment loads within a topology, and (3) designing a reliable distribution circuit topology. First, a theoretical framework is developed to demonstrate the relationship between the reliability of a distribution circuit and the high-level topology of its connections. For the ship’s primary distribution system, a breaker-and-a-half (BAAH) topology was observed to be the most reliable. The reliability indices are further improved by optimally placing equipment loads within the BAAH topology. For zonal electric distribution (ZED) systems, an algorithm to design an optimal topology by minimizing the number of conductors while satisfying a required reliability measure is proposed. It is concluded that the reliability of a distribution circuit depends on: (1) the topology of its connections, and (2) the relative placement of equipment loads and generators.

A Hybrid DC Vacuum Circuit Breaker for Medium Voltage: Principle and First Measurements

A novel concept of hybrid dc vacuum circuit breakers (VCBs), based on the combination of zero-voltage switching (ZVS) and zero current switching principle, was developed to meet the needs of the dc zonal distribution system on shipboard rated for a current of several kiloamperes and a voltage of several kilovolts. In normal operation, the VCB handles the continuous flow of dc current, minimizing the onstate losses. When protection against the fault is requested, the current is first divided between the VCB and the static branch before being quickly interrupted under a forced commutation principle. Laboratory tests have been dedicated to characterize the reliability of the high-current commutation from the VCB to the static branch and the turnoff characteristic of the silicon-controlled rectifier under high-current conditions. Finally, the critical design of the high-speed VCB is discussed.

Fault Location in a Zonal DC Marine Power System Using Active Impedance Estimation

Momentum is gathering on the development of dc power systems for naval platforms. However, the necessary accurate location and isolation of faults within the zonal distribution system remains a challenge. The method of “foldback” is an example of a technique which has been developed to exploit the fast control of the supply power converters to maintain bus currents to within acceptable levels. Techniques such as this need to be supported by equipment which can classify and localize the fault, so the fault can be cleared and the system can be reconfigured. A new technology - active impedance estimation - is presented which offers benefits to future marine power systems, and its application to dc zonal distribution systems is discussed. Experimental results from a dc system demonstrator show the potential of the new technique for fault location.

Active fault protection for an AC zonal marine power system

This study presents a method to protect the zonal distribution system proposed for future ships when fault occurs. By utilising a bus interface unit, the energy storage and grid interface within it provide one benefit that an independent fault protection scheme can be achieved. The new protection scheme is based on active impedance estimation. This technique actively imposes small transient disturbances onto the system at a point of measurement to excite the system in real time and estimate the system impedance at that point. The continuous wavelet transform is employed to achieve accurate impedance estimation over a broad frequency range from a small amount and very noisy data. The performance of this proposed technique is investigated both by simulation and experiment. The scheme exploits the increased use of power electronic devices to provide a useful complement to traditional protection strategies, which can also provide the necessary back up protection during extreme protection failure, without the need for communication channels.

Multi-agent based reconfiguration of AC-DC shipboard distribution power system

The integrated power system (IPS) within an AC-DC zonal distribution system helps to increase the ship survivability, flexibility and reliability. By reducing ship susceptibility to faults and disturbances, decentralized reconfiguration is preferable

Institutionalizing the Electric Warship

The Navy has invested a considerable amount of resources in developing Electric Warship technology in the past twenty years. We have witnessed a number of early technology demonstrations as well as incorporation of Integrated Power System (IPS) technology into ship programs such as LHD 8, T-AKE, DD(X), and CVN 21. Although these early adopters have paved the way for establishing the practice of electric warship design, we are now at a critical point in time for institutionalizing the electric warship. A technology is institutionalized when the following activities have occurred: ▪ Establish a common architecture and interfaces. ▪ Establish a common design processes. ▪ Incorporate the architecture and design processes into design tools. ▪ Codify the practice in government or industry specifications, standards, and guides. ▪ Teach the architecture and design process as part of a typical engineering school curriculum. This article reviews the progress in electric warship technology, describes progress (including ongoing efforts) in institutionalization, and highlights critical near term shortcomings. Some of the shortcomings in design processes and tools include: ▪ Undefined (in authoritative documentation) concepts such as zonal survivability and quality of service. ▪ Obsolete requirement terms such as “sustained speed” and “endurance speed/range” ▪ Conflicting design practices for propulsion and ship service prime mover sizing. ▪ Customized system protection strategies for different classes of ships. ▪ Ambiguous methods for the sizing of zonal distribution system components. ▪ Lack of integration of IPS design algorithms into ship concept tools such as ASSET. ▪ Lack of knowledge as to how to effectively use modeling and simulation to make electric plant design decisions for each stage of ship design. Additionally, the article details progress in updating standards and specifications, such as the Naval Vessel Rules and DOD-STD-1399. Finally, efforts to incorporate Electric Warship design into the curriculum at [RA1] traditional Naval Architecture are described.

A Model-in-the-Loop Interface to Emulate Source Dynamics in a Zonal DC Distribution System

A model-in-the-loop capability (MIL) has been developed to emulate the dynamics of alternative power sources in a hardware-based dc zonal electrical distribution system. Using this tool, models of the power sources are simulated in real-time and interfaced with hardware components at the voltage and current levels of the power system. Coupling between simulation and hardware is established through a dc/dc power converter using model/wall-clock time synchronization. The MIL capability is illustrated in the emulation of a synchronous machine/converter power source. Results of time-domain and frequency-domain studies are provided to validate the approach.

Zonal Electrical Distribution Systems: An Affordable Architecture for the Future

ABSTRACTThe electrical system of today's U. S. Navy ships was designed for reliability of power to vital loads. The existing radial electrical system architecture has evolved from World War II to an increasingly complex and expensive system as vital loads have grown and become more power quality sensitive for each new class of ships.The maze of normal and alternate cables on modern navy ships is almost impossible to protect and keep functioning during and after a casualty. The Navy is now demanding that future ships be more affordable while maintaining existing performance capabilities. New studies have shown that zonal electrical distribution system architecture provides a construction cost savings while inherently providing more operational flexibility.This paper will discuss cost and weight comparisons of existing conventional electrical distribution systems to proposed zonal distribution systems on DDG‐51 and LSD‐41 class ships. It will examine the weight impacts and affordability of installing the zonal distribution system on these ships. Further, it will discuss various zonal distribution system architectures, commonality of components with surface ship electrical distribution systems, and propose developments which will enhance future navy and maritime ship construction.