Active contribution of PV inverters to voltage control – from a smart grid vision to full-scale implementation

Abstract

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.

Wide-Scale Adoption of Photovoltaic Energy: Grid Code Modifications Are Explored in the Distribution Grid

“…For example, all PV systems in germany connected to either low-or medium-voltage grids are required to be able to provide reactive power [14], but at the same time, the minimum PF should be satisfied. With this PF constraint, several reactive power control approaches are available for highly integrated PV systems, such as fixed , cos { fixed , Q and Q Û h droop function methods [14], [19], [62]. in the future, similar requirements are expected to grow and be imposed on low-voltage PV systems to host more PV capacity since they are able to participate in the reactive power management [63], [64].…”

Energy storage options for voltage support in low-voltage grids with high penetration of photovoltaic

“…The most remote node in the feeder, presents the highest sensitivity value, thus it is the most critical location for active power injection in relation to voltage variation. The effectiveness of such methods has been proven and different performances in relation to grid losses and components loading are observable [10]. One of the limitations is that many existing PV installations are not capable of reactive power consumption.…”

“…Local methods based on reactive power for voltage control have been the most used so far, as they are implemented on each PV inverter that can work independently [10]- [11].…”

Suggested grid code modifications to ensure wide-scale adoption of photovoltaic energy in distributed power generation systems

“…For example, all PV systems in Germany connected to either low-or medium-voltage grids are required to be able to provide reactive power [11], but at the same time the minimum power factor should be satisfied. With this power factor constraint, several reactive power control approaches are available for highly integrated PV systems, such as fixed cosφ, fixed Q and Q (U) droop function methods [11], [15], [46]. In the future, similar requirements are expected to be imposed on low voltage PV applications in order to host more PV capacity in the line.…”