Overview of current development in electrical energy storage technologies and the application potential in power system operation

DC microgrids (MGs) have been gaining a continually increasing interest over the past couple of years both in academia and industry. The advantages of dc distribution when compared to its ac counterpart are well known. The most important ones include higher reliability and efficiency, simpler control and natural interface with renewable energy sources, and electronic loads and energy storage systems. With rapid emergence of these components in modern power systems, the importance of dc in today's society is gradually being brought to a whole new level. A broad class of traditional dc distribution applications, such as traction, telecom, vehicular, and distributed power systems can be classified under dc MG framework and ongoing development, and expansion of the field is largely influenced by concepts used over there. This paper aims first to shed light on the practical design aspects of dc MG technology concerning typical power hardware topologies and their suitability for different emerging smart grid applications. Then, an overview of the state of the art in dc MG protection and grounding is provided. Owing to the fact that there is no zero-current crossing, an arc that appears upon breaking dc current cannot be extinguished naturally, making the protection of dc MGs a challenging problem. In relation with this, a comprehensive overview of protection schemes, which discusses both design of practical protective devices and their integration into overall protection systems, is provided. Closely coupled with protection, conflicting grounding objectives, e.g., minimization of stray current and common-mode voltage, are explained and several practical solutions are presented. Also, standardization efforts for dc systems are addressed. Finally, concluding remarks and important future research directions are pointed out.

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DC Microgrids—Part II: A Review of Power Architectures, Applications, and Standardization Issues

Annual Energy Outlook 2008 With Projections to 2030

Transportation electrification is one of the main research areas for the past decade. Electric vehicles (EVs) are taking over the market share of conventional internal combustion engine vehicles. The increasing popularity of EVs results in higher number of charging stations, which have significant effects on the electricity grid. Different charging strat2egies, as well as grid integration methods, are being developed to minimize the adverse effects of EV charging and to strengthen the benefits of EV grid integration. In this paper, a comprehensive review of the current situation of the EV market, standards, charging infrastructure, and the impact of EV charging on the grid is presented. The paper introduces the current EV status, and provides a comprehensive review on important international EV charging and grid interconnection standards. Different infrastructure configurations in terms of control and communication architectures for EV charging are studied and evaluated. The electric power market is studied by considering the participation roles of EV aggregators and individual EV owners, and different optimization and game based algorithms for EV grid integration management are reviewed. The paper specially presents an evaluation on how the future EV development, such as connected vehicles, autonomous driving, and shared mobility, would affect EV grid integration as well as the development of the power grid moves toward future energy Internet and how EVs would affect and benefit the development of the future energy Internet. Finally, the challenges and suggestions for the future development of the EV charging and grid integration infrastructure are evaluated and summarized.

Electric vehicles standards, charging infrastructure, and impact on grid integration: A technological review

The increasing penetration of renewable energy sources (RES) poses a major challenge to the operation of the electricity grid owing to the intermittent nature of their power output. The ability of utility-scale battery energy storage systems (BESS) to provide grid support and smooth the output of RES in combination with their decrease in cost has fueled research interest in this technology over the last couple of years. Power electronics (PE) is the key enabling technology for connecting utility-scale BESS to the medium-voltage grid. PE ensure energy is delivered while complying with grid codes and dispatch orders. Simultaneously, the PE must regulate the operating point of the batteries, thus for instance preventing overcharge of batteries. This paper presents a comprehensive review of PE topologies for utility BESS that have been proposed either within industry or the academic literature. Moreover, a comparison of the presently most commercially viable topologies is conducted in terms of estimated power conversion efficiency and relative cost.

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A Review of Power Electronics for Grid Connection of Utility-Scale Battery Energy Storage Systems

Corporate research centers, universities, power equipment vendors, end users, and other market participants around the world are beginning to explore and consider the use of dc in future transmission and distribution system applications. Recent developments and trends in electric power consumption indicate an increasing use of dc-based power and constant power loads. In addition, growth in renewable energy resources requires dc interfaces for optimal integration. A strong case is being made for intermeshed ac and dc networks, with new concepts emerging at the medium-voltage (MV) level for MV dc infrastructure developments.

Ship to Grid: Medium-Voltage DC Concepts in Theory and Practice

Grid level energy storage systems are a cornerstone of future power networks and smart grid development. Better energy storage systems are one of the last hurdles hindering the integration of renewable generation. There are currently many methods of implementing energy storage, ranging from pumped hydro storage to sodium-sulfur battery storage. All energy storage technologies share a common disadvantage which is high initial installation costs. This survey was undertaken with the intent of identifying the technological state of battery energy storage for power systems, as well as providing a background on the modeling and simulation of those battery technologies.

Survey of battery energy storage systems and modeling techniques

Power electronic conversion units will serve as a key enabling technology for assisting in the continued growth of grid-scale energy storage. This paper presents existing and future power electronic conversion systems and components that aid the interconnection of grid-scale energy storage or utilize storage to minimize grid disruption at all voltage classes including transmission, distribution, and future grid architectures such as the microgrid. New R&D solutions to aid the interconnection process including efforts in bidirectional charger design and potentially solid-state transformers (SSTs) are emphasized. The role of energy storage to support microgrid research and growth, while highlighting power electronic behavior within this environment, is considered. Last, an example that bridges the microgrid and energy storage theme is given through the design and operation of a direct current (dc) electric vehicle (battery) charging station. When appropriate, manufacturer solutions and success stories of utilizing latest battery technologies interfaced via power electronic solutions at the utility scale are provided.

Power Electronics for Grid-Scale Energy Storage

MVDC infrastructure serves as a platform for interconnecting many forms of renewable electric power generation, including wind and solar. Forthcoming abundant loads such as industrial facilities, data centers, and electric vehicle charging stations can be powered using MVDC technology. MVDC networks are expected to improve efficiency by serving as an additional layer between the transmission and distribution level voltages for which renewable resources could directly connect with smaller rated power conversion equipment. This work establishes a 5 kV MVDC architecture composed of 4, type 4 wind turbines (full converter) capable of supplying 20 MW and a photovoltaic plant supplying 1 MW of power. The load emphasized in this article is an electric vehicle charging station. Details of the modeling approach are presented as well as validated simulation results performed in PSCAD of the overall MVDC structure.

Advancements in medium voltage DC architecture development with applications for powering electric vehicle charging stations

The benefits provided by energy storage appear to be nearly limitless and this is especially true in regards to power systems. Gas turbine generators are needed to meet peak load demand but operating them is quite expensive. Energy storage can be used to flatten the electrical load by charging the storage when the system load is low and discharging the storage when the system load is high. If the system load is flat enough, the fast response time of gas turbine generators won't be needed. This study investigates the economic feasibility of NaS battery storage and pumped hydro energy storage used for the application of load leveling.

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Adam R. Sparacino

Papers

Ship to Grid: Medium-Voltage DC Concepts in Theory and Practice

Survey of battery energy storage systems and modeling techniques

Power Electronics for Grid-Scale Energy Storage

Advancements in medium voltage DC architecture development with applications for powering electric vehicle charging stations

Economic analysis of grid level energy storage for the application of load leveling