A virtual power plant assists in the integration of distributed energy resources in the power system. With a rising share of distributed generation, an active management of distributed energy resources is indispensable in order to ensure operation of the electricity network towards the future. In this paper, the virtual power plant concept is analyzed. Three essential components that characterize a virtual power plant are distinguished, followed by a comprehensive overview of the services they can deliver in today's liberalized markets in Europe. It is found that a combination of technical, economic and regulatory barriers still hamper a widespread implementation of the concept. In addition, specific regulatory barriers are identified that hinder a virtual power plant in providing certain services. Hence, it is advised that primarily product and service definitions, as well as market mechanisms, are reviewed.

The European Union strives towards an integrated European electricity market. Achieving this objective while preserving a zonal pricing approach in combination with market coupling, requires an efficient cross-border transmission capacity calculation and allocation mechanism. In this context, a new flowbased algorithm is developed in the CWE region for the dayahead time frame. The idea is to accurately take into account the impact each trade has on the grid by translating cross-border contractual exchanges into physical flows. This paper compares this flow-based approach to the conventional ATC mechanism for the four steps that can be distinguished in the daily cross-border coordination process. To this end, market reports concerning the operation of the flow-based method are studied. While flow-based market coupling is beneficial to ATC from a theoretical point of view, operational challenges before, during and after market coupling are identified. These have to be considered as well in assessing the overall improvement of flow-based compared to ATC.

As German TSOs are faced with the threat of northsouth transmission line overloading, the option of a national bidding zone reconfiguration in the form of a separate northern and southern bidding zone is investigated. By imposing a limit on north-south transactions during market clearing, less redispatch actions are necessary afterwards, as such resulting in more efficient congestion management. However, through market coupling, a national bidding zone reconfiguration also has an impact on neighbouring electricity markets. This paper analyzes the altered interactions between electricity markets caused by the introduction of two German prices zones by means of a costminimizing dispatch model. Besides modifying the market outcome within Germany, this market design change also impacts consumers and producers in other European countries. Therefore, a national bidding zone reconfiguration should always be analyzed in a European wide context.