Microgrid systems show great promise for integrating large numbers of distributed energy resource (DER) systems into future power networks. This paper provides a brief overview of current microgrid technologies and issues associated with their implementation. The case is made for a real-time power management and control system that attempts to optimize microgrid systems based on multiple objectives, such as power demands, fuel consumption, environmental emissions, costs, dispatchable loads, etc. A multi-agent based control architecture that can ensure robust, stable, and optimal microgrid operation is also addressed. In addition to the discussion of power management and control topics, a qualitative classification tool has been proposed for assisting system planners in assessing the impact of microgrid systems on broader grid operations.

A review of challenges to real-time power management of microgrids

Marginal-cost-based dynamic pricing of electricity services, including real power, reactive power, and reserves, may provide unprecedented efficiencies and system synergies that are pivotal to the sustainability of massive renewable generation integration. Extension of wholesale high-voltage power markets to allow distribution network connected prosumers to participate, albeit desirable, has stalled on high transaction costs and the lack of a tractable market clearing framework. This paper presents a distributed, massively parallel architecture that enables tractable transmission and distribution locational marginal price (TD electric vehicle (EV) battery charging and storage; heating, ventilating, and air conditioning (HVAC) and combined heat & power (CHP) microgenerators; computing; volt/var control devices; grid-friendly appliances; smart transformers; and more. The proposed iterative distributed architecture can discover T&DLMPs while capturing the full complexity of each participating DER’s intertemporal preferences and physical system dynamics.

Co-Optimization of Power and Reserves in Dynamic T&D Power Markets With Nondispatchable Renewable Generation and Distributed Energy Resources

This paper considers the effects of various voltage control solutions on facilitating an increase in allowable levels of distributed generation installation before voltage violations occur. In particular, the voltage control solution that is focused on is the implementation of ‘soft’ normally-open points (SNOPs), a term which refers to power electronic devices installed in place of a normally-open point in a medium-voltage distribution network which allows for control of real and reactive power flows between each end point of its installation sites. While other benefits of SNOP installation are discussed, the intent of this paper is to determine whether SNOPs are a viable alternative to other voltage control strategies for this particular application. As such, the SNOPs ability to affect the voltage profile along feeders within a distribution system is focused on with other voltage control options used for comparative purposes. Results from studies on multiple network models with varying topologies are presented and a case study which considers economic benefits of increasing feasible DG penetration is also given.

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Increasing distributed generation penetration using soft normally-open points

Islanding protection of active distribution networks with renewable distributed generators: A comprehensive survey

This paper presents a microgrid paradigm with both DC and AC links, which may provide an effective way to integrate a heterogeneous set of small-size distributed energy resources into the existing electric power infrastructure The collection of aggregated energy resource units at each level represents those distributed resources to the upper level as a single self-regulated entity (as a DC or AC, generator or load) At the top level, the collection of all distributed energy resources in the microgrid appears to the utility grid as indistinguishable from many other currently legitimate customer sites Maintaining this profile relies on the flexibility of advanced power electronics that control the interfaces among distributed energy units, DC links, AC links, and the surrounding power system This paper also discusses some major issues pertinent to behavioral functions and technical requirements of the power electronics interfaces and controls A decoupled control framework is developed for the hybrid microgrid and the performances are evaluated

Hybrid DC- and AC-Linked Microgrids: Towards Integration of Distributed Energy Resources

Until now, distribution networks are regarded as a passive termination of the transmission network, with a radial structure, unidirectional power flows, and a simple and efficient protection scheme. In presence of a large amount of distributed generation (DG), distribution networks will gradually, but ineluctably, change towards a new kind of active networks. The most revolutionary change, needed to efficiently allocate so much DG, could be represented by the adoption of a meshed network architecture. For this reason, in the paper new possible arrangements for distribution networks have been deeply investigated and compared with the radial scheme. Steady state and dynamic simulations have been performed, considering a portion of the real Italian distribution network, and voltage profile, power losses, short circuit currents and grid reliability have been analyzed.

V. Allegranza

Papers

Meshed vs. radial MV distribution network in presence of large amount of DG