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

Electric Power Conversion and Micro-Grids

This edited volume is a collection of reviewed and relevant research chapters offering a comprehensive overview of recent achievements in the field of micro-grids and electric power conversion. The book comprises single chapters authored by various researchers and is edited by a group of experts in such research areas. All chapters are complete in themselves but united under a common research study topic. This publication aims at providing a thorough overview of the latest research efforts by international authors on electric power conversion, micro-grids, and their up-to-the-minute technological advances and opens new possible research paths for further novel developments

A review of optimal operation of microgrids

The term microgrid refers to small-scale power grid that can operate autonomously or in concurrence with the area’s main electrical grid. The intermittent characteristic of DGs which defies the power quality and voltage manifests the requirement for new planning and operation approaches for microgrids. Consequently, conventional optimization methods in new power systems have been critically biased all through the previous decade. One of the main technological and inexpensive tools in this regard is the optimal generation scheduling of microgrid. As a primary optimization tool in the planning and operation fields, optimal operation has an undeniable part in the power system. This paper reviews and evaluates the optimal operation approaches mostly related to microgrids. In this work, the foremost optimal generation scheduling approaches are compared in terms of their objective functions, techniques and constraints. To conclude, a few fundamental challenges occurring from the latest optimal generation scheduling techniques in microgrids are addressed

Electric thermal storage in isolated wind diesel power systems: use of distributed secondary loads for frequency regulation

Thesis (Ph.D.) University of Alaska Fairbanks, 2017Isolated coastal utilities in Arctic villages commonly use a mix of diesel and wind power to provide electrical service to their consumers. It is common for such communities to experience periods of high wind generation for which no immediate demand exists and either waste, curtail, or poorly utilize the surplus. The objective of the present work is to explore (through mathematical and numerical modelling) the technical feasibility of and optimization strategies for distributing this excess wind energy as domestic space heat for use as a cleaner, more economical alternative to fossil fuels. Autonomously controlled Electric Thermal Storage (ETS) devices are considered as a solution to decouple the supply of excess wind power with domestic heat demand without the need for communication infrastructure or a second distribution circuit. First, using numerical heat transfer analysis, it is shown that the performance of an ETS heater core can be generalized and expressed in terms of its physical properties and simple geometric dimensions in such a way as to inform system sizing and economic performance studies for prospective applications. Furthermore, a collection of autonomous ETS units is shown (using a full-scale lab-validated mathematical model) to possess the ability to assume the role of partial and/or sole frequency regulator on a hybrid wind-diesel system. Several design changes are proposed, which render the commercially-available units more amenable to frequency regulation. Ultimately, ETS is shown to be a promising alternative means of utilizing excess renewable energy for domestic space heat while providing additional stability to the electrical grid.Chapter 1 Introduction -- 1.1 Hybrid Wind-Diesel Systems -- 1.2 Frequency Regulation -- 1.3 Voltage Regulation -- 1.4 Energy Storage -- 1.5 Secondary Loads -- 1.6 Electric Thermal Storage -- 1.7 Summary and Organization of Subsequent Chapters -- 1.8 Nomenclature -- 1.9 References -- Chapter 2 Summary of Measurement and Modeling Methodologies -- 2.1 Numerical Heat Transfer - Measurement -- 2.2 Numerical Heat Transfer - Physical Modeling -- 2.3 Electromechanical Dynamics - Measurement -- 2.3.1 Field Measurements -- 2.3.2 Raw Data -- 2.3.3 Post Processing: RMS Values -- 2.3.4 Post Processing: Frequency and Power Factor -- 2.3.5 Post Processing: Impedance, Real Power, and Reactive Power -- 2.4 Electromechanical Dynamics - Modeling -- 2.4.1 Model Structure -- 2.4.2 Equivalent Circuit Simulation Process -- 2.4.3 Solution of Nonlinear Ordinary Differential Equations (ODEs) -- 2.5 References -- Chapter 3 Generalized Heat Flow Model of a Forced Air Electric Thermal Storage Heater Core -- 3.1 Abstract -- 3.2 Introduction -- 3.3 Model -- 3.3.1 Definitions -- 3.3.2 Structure -- 3.3.3 Governing Equations -- 3.3.4 Boundary Conditions -- 3.3.5 Material Properties -- 3.4 Analysis -- 3.4.1 Solution Linearization and Air Velocity Profile -- 3.4.2 Thermal Gradients -- 3.4.3 Parameter Sweep -- 3.5 Results and Discussion -- 3.5.1 One-parameter Model -- 3.5.2 Two-parameter Model -- 3.5.3 Core Energy Balance -- 3.5.4 Stove Modelling -- 3.6 Conclusions -- 3.7 Acknowledgements -- 3.8 Funding -- 3.9 Nomenclature -- 3.10 References -- Chapter 4 Development of a Full-Scale-Lab-Validated Dynamic Simulink© Model for a Stand-Alone -- Wind-Powered Microgrid -- 4.1 Abstract -- 4.2 Introduction -- 4.3 Mathematical Model -- 4.3.1 Diesel Engine/Governor Model -- 4.3.2 Synchronous Generator Model -- 4.3.3 Excitation System Model -- 4.3.4 Induction Generator Model -- 4.4 Data Collection -- 4.5 Results -- 4.5.1 Data Processing -- 4.5.2 Diesel Only (DO) Mode - Laboratory Results -- 4.5.3 Diesel Only (DO) Mode - Simulation Results -- 4.5.4 Wind-Diesel (WD) Mode -- 4.6 Conclusions -- 4.7 Future Work -- 4.8 Acknowledgements -- 4.9 References -- Chapter 5 Frequency Regulation by Distributed Secondary Loads on Islanded Wind-Powered Microgrids -- 5.1 Abstract -- 5.2 Introduction -- 5.3 Mathematical Model -- 5.3.1 Wind-Diesel Hybrid System -- 5.3.2 Individual ETS Units Response -- 5.3.3 Aggregate DSL Response -- 5.4 Analysis -- 5.4.1 Invariant Model Inputs (Machine Parameters) -- 5.4.2 Variable Model Inputs -- 5.4.3 Model Outputs -- 5.5 Results and Discussion -- 5.5.1 Synchronized Switching -- 5.5.2 Staggered Switching -- 5.5.3 Additional Observations and Discussion -- 5.6 Conclusion and Future Work -- 5.7 References -- Chapter 6 Modelling Integration Strategies for Autonomous Distributed Secondary Loads on High Penetration Wind-Diesel Microgrids -- 6.1 Abstract -- 6.2 Introduction -- 6.3 Model -- 6.3.1 System Requirements -- 6.3.2 System Components -- 6.3.3 Control Strategy -- 6.4 Results and Discussion -- 6.4.1 Ramp Simulation -- 6.4.2 Representative Simulation -- 6.4.3 Design Considerations -- 6.5 Conclusions -- 6.6 Acknowledgements -- 6.7 References -- Chapter 7 Results and Observations -- 7.1 Result and Observations of Chapter 3 -- 7.2 Results and Observations of Chapter 4 -- 7.3 Results and Observations of Chapter 5 -- 7.4 Results and Observations of Chapter 6 -- Chapter 8 Conclusions -- 8.1 Conclusions for Generalized Heat Flow Model of a Forced Air Electric Thermal Storage Heater Core -- 8.2 Conclusions for Development of a Full-Scale-Lab-Validated Dynamic Simulink© Model for a Stand-Alone Wind-Powered Microgrid -- 8.3 Conclusions for Frequency Regulation by Distributed Secondary Loads (DSLs) on Islanded Wind-Powered Microgrids -- 8.4 Conclusions for Modeling Integration Strategies for Autonomous Distributed Secondary Loads on High Penetration Wind-Diesel Microgrids -- 8.5 Suggestions for Future Research -- 8.6 Overall Conclusions -- 8.7 Acknowledgements

Sistemas de gestión de energía para microrredes: evolución y desafíos en el marco de la transición energética

Context: Microgrids have been gaining space and credibility in terms of research and real applications. Technological maturity and new regulations have allowed these types of systems to position themselves as a real alternative to increase the coverage of the energy service and improve its quality. One of the biggest challenges of microgrids is the management of resources and their synchronization with conventional grids. In order to overcome the inconvenience of synchronizing and managing the components of a microgrid, research on management systems has been conducted, which usually consist of a set of modules and control strategies that manage the available resources. However, these studies have not reached unanimity on the best method to perform these tasks, which is why it is necessary to perform a systematic collection of information and clearly define the state of research in energy systems management for this type of network. Method: Based on the above, a systematic mapping was carried out in this article, wherein a significant number of papers that have contributed to this area were compiled. Taxonomies were generated based on the nature of the variables collected. These variables correspond to the data or information that enters and/or leaves the microgrid management system, such as meteorological variables, power, priority loads, intelligent loads, economic, operating states, and binary outputs. Conclusions: It was observed that, despite the advances in studying different techniques and strategies microgird control and management, other factors that may affect performance have not been covered in a relevant way, such as the nature of variables and microgrid topology, among others.     Contexto: Las microrredes eléctricas han venido ganando espacio y credibilidad a nivel de investigación y aplicaciones reales. La madurez tecnológica y las nuevas regulaciones han permitido que este tipo de sistemas se posicionen como una alternativa real para aumentar la cobertura del servicio de energía y mejorar su calidad. Uno de los mayores retos de las microrredes es la gestión de los recursos y su sincronización con la red convencional. Con el fin de superar el inconveniente de sincronizar y gestionar los componentes de la microrred, se ha investigado sobre sistemas de gestión, los cuales normalmente consisten en un conjunto de módulos y estrategias de control que administran los recursos disponibles. Sin embargo, estas investigaciones no han llegado a una unanimidad sobre el mejor método para realizar estas tareas, por lo cual se hace necesario realizar una recopilación sistemática de información y definir claramente el estado de la investigación en gestión de sistemas de energía para este tipo de redes. Método: Con base en lo anterior, en este artículo se realizó un mapeo sistemático, donde se recopiló un importante número de artículos que han aportado a este campo. Se generaron taxonomías basadas en la naturaleza de las variables que se recopilaron. Dichas variables corresponden a los datos o información que entran y/o salen del sistema de gestión de la microrred, tales como variables meteorológicas, potencia, cargas prioritarias, cargas inteligentes, económicas, estados de operación y salidas binarias. Conclusiones: Se observa que, a pesar de los avances en el estudio de las diferentes técnicas y estrategias de control y gestión de microrredes, no se han cubierto de forma relevante otros factores que pueden afectar al rendimiento, como la naturaleza de las variables y la topología de la microrred, entre otros

Using an intelligent method for microgrid generation and operation planning while considering load uncertainty

The integration of distributed generation (DG), energy storage systems (ESS), and controllable loads near the place of consumption has led to the creation of microgrids. However, the uncertain nature of renewable energy sources (wind and photovoltaic), market prices, and loads have caused issues with guaranteeing power quality and balancing generation and consumption. To solve these issues, microgrids should be managed with an energy management system (EMS), which facilitates the minimization of operating (performance) costs, the emission of pollutants, and peak loads while meeting technical constraints. To this effect, this research attempts to adjust parameters by defining indicators related to the best possible conditions of the microgrid. Generation planning, the storage of generated power, and exchange with the main grid are carried out by defining a dual-purpose objective function, which includes reducing the operating cost of power generation, as well as the pollution caused by it in the microgrid, by means of the SALP optimization algorithm. Moreover, in order to make the process more realistic and practical for microgrid planning, some parameters are considered as indefinite values, as they do not have exact values in their natural state. The results show the effect of using the introduced intelligent optimization method on reducing the objective function value (cost and pollution)

Power Management of A Microgrid with A Distributed Energy Storage in Grid Connected and Islanded Modes

Control and operation of a microgrid can be operated at grid connected or islanded modes. In this paper, the microgrid consists of a Diesel, PV modules with a distributed energy storage system, loads, and inverter. The purpose of power management is to control the stability of the system to cope with changes in load and interconnection with other networks. The stability of the microgrid is also obtained by setting the load connected to the system. Power management is also controls the operation of each plant based on the condition of the energy sources used as a source of generation. In islanded mode, the main goal of power management is to stabilize the system, in terms of frequency and voltage. In grid connected mode, typical objectives are to minimize the price of energy import at the point of common coupling (PCC)