Control strategies for microgrid with multiple distributed energy resources

Microgrid is considered as a smart solution to the global energy crisis and environmental issues these days for employing green technology. This is a small scale, usually renewable energy based distributed generation system which basically serves local users and does not require transmission lines. However, Microgrid needs a suitable control system to improve its efficiency and reliability to work as a standalone unit or as parallel connected unit with the main utility grid. For instance, renewable energy sources such as, Solar Photovoltaics and Wind Turbine depend on weather conditions thus result in output power fluctuation. In this case, a storage unit is essential that can provide back up during low generation period and can store outstanding energy at the time of less demand. In addition, integration of multiple distribution energy resources raises the energy generation of Microgrid sufficiently but increases complications in operations as well. Besides, a communication network is also vital in this case for information transfer within the sources and other components of the structure. Hence, a study related to advance control system to maintain a smart energy management incorporation with fault detection and self-healing aspects of Microgrid is presented in this research. The purpose of this project is to find out the most advantageous control techniques for Microgrid with multiple distributed energy resources which need to be user-friendly as well. Research shows that, Droop control techniques are beneficial for above requirements performing Decentralized control method where communication networks are not essential. Moreover, in this paper some MATLAB/SIMULINK based simulations are presented. Where a Microgrid is modelled that consists of distributed energy resources namely Photovoltaic, Wind turbine and Fuel cells. Finally, simulation results of different droop control techniques are presented and some discussions regarding tested techniques are enclosed

Efficient Decentralized Economic Dispatch for Microgrids with Wind Power Integration

Decentralized energy management is of paramount importance in smart microgrids with renewables for various reasons including environmental friendliness, reduced communication overhead, and resilience to failures. In this context, the present work deals with distributed economic dispatch and demand response initiatives for grid-connected microgrids with high-penetration of wind power. To cope with the challenge of the wind's intrinsically stochastic availability, a novel energy planning approach involving the actual wind energy as well as the energy traded with the main grid, is introduced. A stochastic optimization problem is formulated to minimize the microgrid net cost, which includes conventional generation cost as well as the expected transaction cost incurred by wind uncertainty. To bypass the prohibitively high-dimensional integration involved, an efficient sample average approximation method is utilized to obtain a solver with guaranteed convergence. Leveraging the special infrastructure of the microgrid, a decentralized algorithm is further developed via the alternating direction method of multipliers. Case studies are tested to corroborate the merits of the novel approaches.Comment: To appear in IEEE GreenTech 2014. Submitted Sept. 2013; accepted Dec. 201

Reliability assessment of microgrid with renewable generation and prioritized loads

With the increase in awareness about the climate change, there has been a tremendous shift towards utilizing renewable energy sources (RES). In this regard, smart grid technologies have been presented to facilitate higher penetration of RES. Microgrids are the key components of the smart grids. Microgrids allow integration of various distributed energy resources (DER) such as the distributed generation (DGs) and energy storage systems (ESSs) into the distribution system and hence remove or delay the need for distribution expansion. One of the crucial requirements for utilities is to ensure that the system reliability is maintained with the inclusion of microgrid topology. Therefore, this paper evaluates the reliability of a microgrid containing prioritized loads and distributed RES through a hybrid analytical-simulation method. The stochasticity of RES introduces complexity to the reliability evaluation. The method takes into account the variability of RES through Monte- Carlo state sampling simulation. The results indicate the reliability enhancement of the overall system in the presence of the microgrid topology. In particular, the highest priority load has the largest improvement in the reliability indices. Furthermore, sensitivity analysis is performed to understand the effects of the failure of microgrid islanding in the case of a fault in the upstream network

A review of microgrid development in the United States – A decade of progress on policies, demonstrations, controls, and software tools

Microgrids have become increasingly popular in the United States. Supported by favorable federal and local policies, microgrid projects can provide greater energy stability and resilience within a project site or community. This paper reviews major federal, state, and utility-level policies driving microgrid development in the United States. Representative U.S. demonstration projects are selected and their technical characteristics and non-technical features are introduced. The paper discusses trends in the technology development of microgrid systems as well as microgrid control methods and interactions within the electricity market. Software tools for microgrid design, planning, and performance analysis are illustrated with each tool's core capability. Finally, the paper summarizes the successes and lessons learned during the recent expansion of the U.S. microgrid industry that may serve as a reference for other countries developing their own microgrid industries

Microgrids: Legal and Regulatory Hurdles for a More Resilient Energy Infrastructure

Natural disasters and climate change have made it apparent that energy infrastructure needs to be modernized and microgrids are one type of technology that can help the electricity grid become more resilient, reliable, and efficient. Different states have begun developing microgrid pilot projects including California, New York, Connecticut, and Pennsylvania. The City of Pittsburgh, Pennsylvania is the first city to propose implementing “energy districts” of microgrids that will serve as critical infrastructure, in the first phase, and then expand to commercial and community settings. This large project involves many shareholders including public utilities, government agencies, and private entities. Utilizing microgrids on such a large scale raises issues regarding its classification, as energy generation or energy storage, and whether it should be regulated by public utilities, private entities, or municipalities. In a state like Pennsylvania where the energy market has been deregulated, there is strong concern on what the public utilities involvement will be with microgrid projects. This Note focuses on the regulatory issues that are raised with the construction and operation of microgrids at such a large scale in Pittsburgh. It addresses the difficulties that arise when implementing microgrids in a deregulated energy market state such as Pennsylvania, where little to no statutory language exists regarding microgrids. It will give an overview of proposed Pennsylvania legislation that may impact a public utilities’ control over microgrid technology and the benefits and costs when examining the extent of the public utilities’ role regarding ownership and control of microgrids in a deregulated energy market