DC microgrids and distribution systems: An overview

The exploration of highly active and durable cathodic oxygen reduction reaction (ORR) catalysts with economical production costs is still the bottleneck to realize the large-scale commercialization of fuel cells In recent years, remarkable progress has been achieved in fabricating effective non-precious metal based ORR catalysts In particular, modified carbon materials have aroused extensive research interest because of their excellent performance and low cost In this review, we present an overview on recent advancements in developing defective carbon based materials for catalyzing the ORR In particular, three general kinds of defective carbon electrocatalysts will be summarized They are non-metal induced defective carbons (modified by heteroatoms), intrinsic defective carbons (defects created by a physical or chemical method), and atomic metal species induced/coordinated defective carbons (metal-macrocycle complexes with different coordination environments) The common configurations of various defective carbons will be discussed, with typical examples on recently developed both metal-free and precious/non-precious metal species coordinated carbons Finally, the future research directions of the defective carbon materials are proposed The newly established defect promoted catalysis mechanism will be beneficial for the design and fabrication of highly effective electrocatalysts for practical energy storage and conversion applications

/pdf/defects-on-carbons-for-electrocatalytic-oxygen-reduction-2coc877qu0.pdf

Defects on carbons for electrocatalytic oxygen reduction.

Renewable energy generation is rapidly growing in the power sector industry and widely used for two categories: grid connected and standalone system. This paper gives the insights about fuel cell operation and application of various power electronics systems. The fuel cell voltage decreases bit by bit with expansion in current because of losses associated with fuel cell. It is difficult in handling large rated fuel cell based power system without regulating mechanism. The issue connected with fuel based structural planning and the arrangements are widely investigated for all sorts of utilization. In order to improve the reliability of fuel cell based power system, the integration of energy storage system and advanced research methods are focused in this paper. The control algorithms of power architecture for the couple of well-known applications are discussed. Additionally, the paper addresses the suitable processor utilized as a part of the energy unit application on the premise of fuel cell characteristics. In this paper, the challenges to improve the dynamics of controller in fuel cell based applications are mentioned.

Recent advances and challenges of fuel cell based power system architectures and control – A review

In this paper, a novel high step-up converter is proposed for fuel-cell system applications. As an illustration, a two-phase version configuration is given for demonstration. First, an interleaved structure is adapted for reducing input and output ripples. Then, a C?uk-type converter is integrated to the first phase to achieve a much higher voltage conversion ratio and avoid operating at extreme duty ratio. In addition, additional capacitors are added as voltage dividers for the two phases for reducing the voltage stress of active switches and diodes, which enables one to adopt lower voltage rating devices to further reduce both switching and conduction losses. Furthermore, the corresponding model is also derived, and analysis of the steady-state characteristic is made to show the merits of the proposed converter. Finally, a 200-W rating prototype system is also constructed to verify the effectiveness of the proposed converter. It is seen that an efficiency of 93.3% can be achieved when the output power is 150-W and the output voltage is 200-V with 0.56 duty ratio.

A High-Efficiency High Step-Up Converter With Low Switch Voltage Stress for Fuel-Cell System Applications

Big data analytics (BDA) has increasingly attracted a strong attention of analysts, researchers and practitioners in railway transportation and engineering. This urges the necessity for a review of recent research development in this field. This survey aims to provide a comprehensive review of the recent applications of big data in the context of railway engineering and transportation by a novel taxonomy framework, proposed by Mayring (2003). The survey covers three areas of railway transportation where BDA has been applied, namely operations, maintenance and safety. Also, the level of big data analytics, types of big data models and a variety of big data techniques have been reviewed and summarized. The results of this study identify the existing research gaps and thereby directions of future research in BDA in railway transportation systems.

Recent applications of big data analytics in railway transportation systems: A survey

Fuel cells are considered to be one of the most promising sources of distributed energy because of their high efficiency, low environmental impact and scalability. Unfortunately, multiple complications exist in fuel cell operation. Fuel cells cannot accept current in the reverse direction, do not perform well with ripple current, have a low output voltage that varies with age and current, respond sluggishly to step changes in load and are limited in overload capabilities. For these reasons, power converters are often necessary to boost and regulate the voltage as a means to provide a stiff applicable DC power source. Furthermore, the addition of an inverter allows for the conversion of DC power to AC for an utility interface or for the application of an AC motor. To help motivate the use of power conditioning for the fuel cell, a brief introduction of the different types, applications and typical electrical characteristics of fuel cells is presented. This is followed by an examination of the various topologies of DC-DC boost converters and inverters used for power conditioning of fuel cells. Several architectures to aggregate multiple fuel cells for high-voltage/high-power applications are also reviewed.

/pdf/fuel-cell-power-conditioning-for-electric-power-applications-4ahhrth8ro.pdf

Fuel cell power conditioning for electric power applications: a summary

Power electronics can provide utilities the ability to more effectively deliver power to their customers while providing increased reliability to the bulk power system. In general, power electronics is the process of using semiconductor switching devices to control and convert electrical power flow from one form to another to meet a specific need. These conversion techniques have revolutionized modern life by streamlining manufacturing processes, increasing product efficiencies, and increasing the quality of life by enhancing many modern conveniences such as computers, and they can help to improve the delivery of reliable power from utilities. This report summarizes the technical challenges associated with utilizing power electronics devices across the entire spectrum from applications to manufacturing and materials development, and it provides recommendations for research and development (R&D) needs for power electronics systems in which the U.S. Department of Energy (DOE) could make a substantial impact toward improving the reliability of the bulk power system.

/pdf/power-electronics-for-distributed-energy-systems-and-4zakeicwf3.pdf

Power electronics for distributed energy systems and transmission and distribution applications

This paper proposes a general methodology to analyze the interleaved pulse width modulation (PWM) dc–dc converter. A unified and simple model is constructed and the complete electrical behaviors of the interleaved PWM dc–dc converter could be predicted. Features of the interleaved PWM dc–dc converter are investigated based on this model. Insightful conclusions are derived and can be used to guide designs. This model could serve as a solid foundation for further research, and it is valid to all the common interleaved PWM dc–dc topologies. As an example of its applications, the input current of the interleaved boost converter is investigated in detail. Simulation and experimental results have successfully validated against theoretical analysis.

A Unified Analytical Modeling of the Interleaved Pulse Width Modulation (PWM) DC–DC Converter and Its Applications

Very high switching frequency (1 MHz or more) is highly desired for dc-dc converters to achieve high power density. State-of-the-art dc-dc converters are capable of achieving high-efficiency with the high-switching frequency, which promotes an opportunity and challenge for a redesign of the traditional input filters. This paper describes an optimal input filter design with minimum components count, which consists of fewer passive components than common input filter topologies. The proposed methodology leverages parasitic parameters of both converter and filter elements in order to achieve optimal performance. It also features high flexibility without sacrificing performance. The stability analysis has been performed to ensure a stable system. A prototype has been realized for a transformer-coupled zero voltage switching buck-boost converter and performance has been successfully validated against design targets.

An Optimal Minimum-Component DC–DC Converter Input Filter Design and Its Stability Analysis

Distributed energy resources (DER) are quickly making their way to industry primarily as backup generation. They are effective at starting and then producing full-load power within a few seconds. DER can alleviate the burden on the utility grid by providing ancillary services, which also helps in justifying the installation cost for the DER owner. This paper describes ten types of these ancillary services, which DG can provide to the utility grid. Of these 10 services, the feasibility, control strategy, effectiveness, and cost benefits are all analyzed for the future utility power market.

Xiaoyan Yu

Papers

Fuel cell power conditioning for electric power applications: a summary

Power electronics for distributed energy systems and transmission and distribution applications

A Unified Analytical Modeling of the Interleaved Pulse Width Modulation (PWM) DC–DC Converter and Its Applications

An Optimal Minimum-Component DC–DC Converter Input Filter Design and Its Stability Analysis

Ancillary services provided from DER with power electronics interface