In the framework of liberalized electricity markets, distributed generation and controllable demand have the opportunity to participate in the real-time operation of transmission and distribution networks. This may be done by using the virtual power plant (VPP) concept, which consists of aggregating the capacity of many distributed energy resources (DER) in order to make them more accessible and manageable across energy markets. This paper provides an optimization algorithm to manage a VPP composed of a large number of customers with thermostatically controlled appliances. The algorithm, based on a direct load control (DLC), determines the optimal control schedules that an aggregator should apply to the controllable devices of the VPP in order to optimize load reduction over a specified control period. The results define the load reduction bid that the aggregator can present in the electricity market, thus helping to minimize network congestion and deviations between generation and demand. The proposed model, which is valid for both transmission and distribution networks, is tested on a real power system to demonstrate its applicability.

No abstract

No abstract

SUMMARYIn the framework of deregulated electricity markets, distributed generation and load management are emerging as new technologies. In this context, the microgrid concept adds value to distributed energy resources (DER) by aggregating them into autonomous grids that provide high levels of efficiency, security and controllability. In order to achieve its functions, a microgrid requires a control system in charge of operating the elements in it in an optimal way while the required quality parameters are fulfilled.This paper describes the general architecture of a microgrid energy management system (EMS) based on multi-agent system (MAS) technologies. MAS technologies are considered to be very well suited to systems that require plug and play capabilities, robustness, heterogeneous device integration, high scalability and extensibility. All of which are essential characteristics of a microgrid EMS. This paper also describes the implementation of a secondary control system based on the microgrid EMS architecture developed. This system is in charge of maintaining microgrid frequency and power exchange with the main grid close to predefined values. This is achieved in a way in which generation and consumption resources are optimally dispatched and able to operate in both grid connected and islanded modes. Finally, the control system developed is tested in an actual microgrid in order to assess its performance and demonstrate its applicability.