The increasing interest in integrating intermittent renewable energy sources into microgrids presents major challenges from the viewpoints of reliable operation and control. In this paper, the major issues and challenges in microgrid control are discussed, and a review of state-of-the-art control strategies and trends is presented; a general overview of the main control principles (e.g., droop control, model predictive control, multi-agent systems) is also included. The paper classifies microgrid control strategies into three levels: primary, secondary, and tertiary, where primary and secondary levels are associated with the operation of the microgrid itself, and tertiary level pertains to the coordinated operation of the microgrid and the host grid. Each control level is discussed in detail in view of the relevant existing technical literature.

Trends in Microgrid Control

Microgrids are now emerging from lab benches and pilot demonstration sites into commercial markets, driven by technological improvements, falling costs, a proven track record, and growing recognition of their benefits. They are being used to improve reliability and resilience of electrical grids, to manage the addition of distributed clean energy resources like wind and solar photovoltaic (PV) generation to reduce fossil fuel emissions, and to provide electricity in areas not served by centralized electrical infrastructure. This review article (1) explains what a microgrid is, and (2) provides a multi-disciplinary portrait of today's microgrid drivers, real-world applications, challenges, and future prospects.

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Microgrids: A review of technologies, key drivers, and outstanding issues

The significant benefits associated with microgrids have led to vast efforts to expand their penetration in electric power systems. Although their deployment is rapidly growing, there are still many challenges to efficiently design, control, and operate microgrids when connected to the grid, and also when in islanded mode, where extensive research activities are underway to tackle these issues. It is necessary to have an across-the-board view of the microgrid integration in power systems. This paper presents a review of issues concerning microgrids and provides an account of research in areas related to microgrids, including distributed generation, microgrid value propositions, applications of power electronics, economic issues, microgrid operation and control, microgrid clusters, and protection and communications issues.

State of the Art in Research on Microgrids: A Review

A novel energy management system (EMS) based on a rolling horizon (RH) strategy for a renewable-based microgrid is proposed. For each decision step, a mixed integer optimization problem based on forecasting models is solved. The EMS provides online set points for each generation unit and signals for consumers based on a demand-side management (DSM) mechanism. The proposed EMS is implemented for a microgrid composed of photovoltaic panels, two wind turbines, a diesel generator and an energy storage system. A coherent forecast information scheme and an economic comparison framework between the RH and the standard unit commitment (UC) are proposed. Solar and wind energy forecasting are based on phenomenological models with updated data. A neural network for two-day-ahead electric consumption forecasting is also designed. The system is tested using real data sets from an existent microgrid in Chile (ESUSCON). The results based on different operation conditions show the economic sense of the proposal. A full practical implementation of the system for ESUSCON is envisioned.

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A Microgrid Energy Management System Based on the Rolling Horizon Strategy

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.

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Microgrids: experiences, barriers and success factors

A novel SCADA approach for a renewable based microgrid is proposed. The optimization scheme provides online set points for each generation unit, operation modes for a water supply system, and signals for consumers based on a demand side management mechanism. Additionally, different services are developed for supervising, maintenance, and repair procedures. The participation of the community is ensured through appropriate communication and information exchange procedures. The whole scheme configures a Social SCADA solution. Three specific services are described in detail (battery bank maintenance, photovoltaic system efficiency monitoring, and system restoration). The concept is applied to a smart microgrid composed of photovoltaic panels, a wind turbine, a diesel generator, a battery bank, and a water supply system. The energy management system of the SCADA minimizes the operational costs while supplying the water and electric load demands. The system is implemented and tested using a real data set from a reference location and with an evaluation by the community. Results show the economic sense of the energy management system and the impact of community participation.

A social SCADA approach for a renewable based microgrid — The Huatacondo project

A critical aspect concerning an effective development of isolated microgrids is economical sustainability Most of the efforts are related to social responsibility of local productive companies that look for avoiding long term commitments with the community This work proposes a composed solution that combines a social SCADA approach with a Demand Response program Thus, minimum maintenance costs and a better community involvement for both energy consumption and cost covering can be achieved A social SCADA solution guarantees the participation of the community through an appropriate communication and information exchange procedure, allowing them to execute tasks associated to supervision and maintenance of the micro grid, and equipment repairing On the other hand there is a demand response program that relies on a forecast of renewable energy availability as a function of weather predictions (ie solar radiation, wind speed) In this context, this forecast is sent to people so they are able to react and adapt their consumption, allowing a better use of the renewable resources and decreasing operational costs (fuel consumption) The demand response program interface consists of a 24 hour clock that assigns a specific color, describing the energy availability, for each hour This approach is applied to a smart micro grid composed of photovoltaic panels, a wind turbine, a diesel generator, a battery bank, and a water supply system Results show the effects of community participation through both operational and sustainability indicators, and the economic impact of community participation

D. Ortiz

Papers

A social SCADA approach for a renewable based microgrid — The Huatacondo project

Social SCADA and Demand Response for sustainable isolated microgrids