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The increased integration of Distributed Generation (DG) in electricity networks makes the provision of ancillary services imperative. In the last few years several national and international standards-guidelines have been published stating connection rules for generators, including requirements related to ancillary services. However, the requirements are not always harmonized and at some points present contradictions.This paper provides an overview of key requirements for the provision of ancillary services by distributed generation. A comparative analysis is performed, which identifies contradictions and requirements that are not thoroughly defined. Attention is drawn to potential problems due to specific "unclear" requirements, such as the Q(U) control at asymmetric conditions, which is analyzed through simulations. Furthermore, promising functionalities for future requirements are discussed.

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The integration of large amounts of generation into distribution networks faces some limitations. By deploying reactive power-based voltage control concepts (e.g., volt/var control with distributed generators), the voltage rise caused by generators can be partly mitigated. As a result, the network hosting capacity can be accordingly increased, and costly network reinforcement might be avoided or postponed. This works however only for voltage-constrained feeders (opposed to current-constrained feeders). Due to the low level of monitoring in low voltage networks, it is important to be able to classify feeders according to the expected constraint in order to avoid the overloading risk. The main purpose of this paper is to investigate to which extent it is possible to predict the hosting capacity constraint (voltage or current) of low voltage feeders on the basis of a large network data set. Two machine-learning techniques have been implemented and compared: clustering (unsupervised) and classification (supervised). The results show that the general performance of the classification or clustering algorithms might be considered as rather poor at a first glance, reflecting the diversity of real low voltage feeders. However, a detailed analysis shows that the benefit of the classification is significant.

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For demonstrating future smart grid concepts the MetaPV project, funded by the European Commission, is investigating the additional services of smart photovoltaic (PV) systems for grid support and hosting capacity extension. In this paper the concept of hosting capacity is introduced and illustrated to analyze the impact of expected PV development scenarios on the distribution network selected for the demonstration. Investigations showed that the hosting capacity is currently almost fully exhausted and that network reinforcement would be necessary in order to host the expected PV generation by 2020. Also, the concept of smart PV inverters, which are under development in the frame of the project, is introduced. Such inverters should support network operation through their active and reactive power control possibilities for standalone and supervisory operations and enable the enhancement of the hosting capacity. A short overview on the next steps towards demonstration is provided.Aktive Beteiligung von PV-Wechselrichtern zur Spannungsregelung -von einer Smart Grid-Vision zur ganzheitlichen Implementierung. Zur Demonstration zukü nftiger Smart-Grid-Konzepte werden im Rahmen des Forschungsprojektes MetaPV, das von der Europä ischenKommission gefö rdert wird, die zusä tzlichen Leistungen von Smart Photovoltaik(PV)-Anlagen zur Netzstü tzung und Erhö hung der Netzaufnahmekapazitä t untersucht. In dieser Verö ffentlichung wird der Begriff der Aufnahmekapazitä t vorgestellt und erlä utert. Die Auswirkungen der erwarteten PV-Entwicklungsszenarien auf Versorgungsnetze werden analysiert. Simulationstechnische Untersuchungen zeigten, dass die Aufnahmekapazitä t fast vollstä ndig ausgeschö pft wird und dass Netzausbau unabdingbar ist, um die erwartete PV-Entwicklung bis 2020 im Versorgungsnetz aufnehmen zu kö nnen. Ferner wird das Konzept von Smart PVWechselrichtern eingefü hrt, die im Rahmen des Projekts entwickelt werden. Solche Wechselrichter stü tzen durch die Regelung von Wirk-und Blindleistung das Netz in sowohl Standalone-als auch fernü berwachungsgeregeltem Betrieb (ü bergeordnete Regelung), wodurch die Netzaufnahmekapazitä t erhö ht und der Netzausbau vermieden wird. Eine kurze Ü bersicht ü ber die nä chsten Schritte zur Demonstration wird gezeigt.