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

Microgrid architectures for low voltage distributed generation

[EN] The high penetration of distributed generators, most of them based on renewable energy sources, is modifying the traditional structure of the electric distribution grid. If the power of distributed generators is high enough to feed the loads of a certain area, this area could be disconnected from the main grid and operate in islanded mode. Microgrids are composed by distributed generators, energy storage devices, intelligent circuit breakers and local loads. In this paper, a review of the main microgrid architectures proposed in the literature has been carried out. The microgrid architectures are first classified regarding their AC or DC distribution buses. Besides, more complex microgrid architectures are shown. Both advantages and disadvantages of each one of the microgrid families are discussed.This work is supported by the Spanish Ministry of Science and Innovation under Grant ENE2012-37667-C02-01.Patrao Herrero, I.; Figueres Amorós, E.; Garcerá Sanfeliú, G.; González Medina, R. (2015). Microgrid architectures for low voltage distributed generation. Renewable and Sustainable Energy Reviews. 43:415-424. https://doi.org/10.1016/j.rser.2014.11.054S4154244

Microgrids:experiences, barriers and success factors

Although microgrids have been researched for over a decade and recognized for their multitude of benefits to improve power reliability, security, sustainability, and decrease power costs for the consumer, they have still not reached rapid commercial growth. The main aim of this research is to identify the common barriers and ultimate success factors to implementing a microgrid in the real world. We found that microgrids vary significantly depending on location, components, and optimization goals, which cause them to experience different types of challenges and barriers. However, the most common barriers were identified and grouped into four categories: technical, regulatory, financial, and stakeholder, based on the literature and overlying patterns recognized amongst the thirteen case studies. The most common technical barriers include problems with technology components, dual-mode switching from grid-connected to island mode, power quality and control, and protection issues. There is extensive research on how to overcome these issues, so technical solutions are becoming available yet case specific. Regulatory barriers exist due to interconnection rules with the main grid and the prohibition of bi-directional power flow and local power trading between microgrid and the main network. The latter issue is the barrier experienced most often and has only recently been addressed, so solutions need further research. The main financial barrier is still the burden of high investment and replacement costs of the microgrid. This can be resolved with proper market support in the short term and might naturally resolve itself through learning over the long run. Lastly, stakeholder barriers include issues with conflicting self-interest and trust, and having the expertise to manage operations. These stakeholder barriers are not yet addressed in the literature and need to be further researched

Development of Microgrid Test Bed for Testing Energy Management System

Today the world population has reached 7.5 billion, and this number is expected to grow at the rate of 1.13% every year [1]. With this increase in population, the total demand for electricity has also increased. More people means the need for more power: electricity to power homes, schools, industries, hospitals, and so on. In today’s world, where most of the daily activities are dependent on electricity, demand for electricity, therefore, continues to rise. Currently, managing this growing need for electricity is one of the challenges the world is facing. In addition to this, approximately 1.2 billion people live in remote parts of the world where the electricity supply is either limited or non-existent [2]. Providing an affordable and easily available source of electricity to this population is another challenge. In response to these challenges, a significant number of countries are investing in the integration of renewable resources for energy production. Renewable resources such as the sun, wind, and water are free, clean, and readily available. Remote and poor parts of the world can also benefit by utilizing these available energy sources for electricity generation. The use of renewables helps to decrease the overall cost of electricity generation as well. This need for clean and safe energy has contributed to creating and promoting the concept of microgrids around the world. Microgrids are defined as small-scale power distribution networks with distributed energy sources, loads, and storage. They can operate in either grid-connected or islanded mode. Renewable sources are intermittent in nature, and uncertainties are always present in the microgrid operation when using these resources. The Energy Management technique is required for the coordination of these resources in order to mitigate the potential risks. Some studies have been conducted in the area of microgrid operation, stability, and control, and various types of laboratory-based microgrid test beds have been developed. A microgrid test bed allows testing of scaled down systems in order to test and simulate large real-world microgrid projects. The objective of this study is to develop a reconfigurable microgrid test bed. This test bed is created on a laboratory scale and is capable of testing energy management algorithms to validate real-time operation. A novel approach to automatic microgrid operation is proposed with the use of commercial off-the-shelf equipment and the Controller Area Network (CAN) protocol. The OPAL-RT 5600 real-time simulator is used as a central controller for controlling and scheduling microgrid sources to supply the load, charge the battery and, read a state of charge values. The CAN communication protocol is used by the controller to control and coordinate different components. Different cases are studied in order to support the reconfigurability, automatic operation, and energy management in the microgrid test bed using the CAN bus

Challenges to the Integration of Renewable Resources at High System Penetration

Successfully integrating renewable resources into the electric grid at penetration levels to meet a 33 percent Renewables Portfolio Standard for California presents diverse technical and organizational challenges. This report characterizes these challenges by coordinating problems in time and space, balancing electric power on a range of scales from microseconds to decades and from individual homes to hundreds of miles. Crucial research needs were identified related to grid operation, standards and procedures, system design and analysis, and incentives, and public engagement in each scale of analysis. Performing this coordination on more refined scales of time and space independent of any particular technology, is defined as a “smart grid.” “Smart” coordination of the grid should mitigate technical difficulties associated with intermittent and distributed generation, support grid stability and reliability, and maximize benefits to California ratepayers by using the most economic technologies, design and operating approaches

Microgrids of commercial buildings: strategies to manage mode transfer from grid connected to islanded mode

Microgrid systems located within commercial premises are becoming increasingly popular and their dynamic behavior is still uncharted territory in modern power networks. Improved understanding in design and operation is required for the electricity utility and building services design sectors. This paper evaluates the design requirements for a commercial building microgrid system to facilitate seamless mode transition considering an actual commercial building microgrid system. A dynamic simulation model of the proposed microgrid system is established (utilizing DIgSILENT Power Factory) to aid the development of planning and operational philosophy for the practical system. An economic operational criterion is developed for the microgrid to incorporate selective mode transition in different time intervals and demand scenarios. In addition, a multi-droop control strategy has been developed to mitigate voltage and frequency variations during mode transition. Different system conditions considering variability in load and generation are analyzed to examine the responses of associated microgrid network parameters (i.e., voltage and frequency) with the proposed mode transition strategy during planned and unplanned islanding conditions. It has been demonstrated that despite having a rigorous mode transition strategy, control of certain loads such as direct online (DOL) and variable-speed-drive (VSD) driven motor loads is vital for ensuring seamless mode-transition, in particular for unplanned islanding conditions