Article by Steffen Fattler, Simon Pichlmaier, Thomas Estermann and Adrian Ostermann in ET, edition 11/2017
The steadily growing generation from volatile renewable energy sources and the simultaneous delayed expansion of the grid are increasing the challenges in the operation of the electricity grid across all voltage levels. In order to eliminate network congestion, grid operators have access to feed-in management as a network security measure. Since 2009, there has been a significant increase in the amount of outage work due to feed-in management as reported by BNetzA. This is accompanied by increasing compensation payments and thus rising network charges for consumers. This article describes a research into the causes of feed-in management usage in 2016 in order to create a basis for a cause-related and targeted discussion of the topic of grid congestion and their elimination. The contribution was produced as part of the joint project C/sells, which is funded by the "Schaufenster intelligente Energie – Digitale Agenda für die Energiewende" (SINTEG) funding programme of the Federal Ministry of Economics and Energy (BMWi) (funding code: 03SIN121).
Root cause analysis
For the year 2016, the utilization-related feed-in management measures of four distribution system operators (DSO) Avacon, Bayernwerk, E. DIS and Schleswig-Holstein Netz were evaluated. The distribution of outage work shows that in regions with a large number of installed wind turbines large amounts of energy are throttled. In the case of photovoltaic systems, however, this correlation is not noticeable. In addition, if one considers causes or rather requesters of the feed-in management measures published by the DSOs and their shares of outage work, it becomes clear that large parts of the energy has to be curtailed due to transmission grid congestions. Figure 1 shows the comparison of the transmission grid operator (TSO) related feed-in time series, divided into PV and wind, with the time series of the regulated energy due to feed-in management and the resulting Spearman’s rank correlation coefficients for the DSOs Schleswig-Holstein Netz and E. DIS. A distinction was made between measures requested by the TSO and those requested by the DSO. The investigations show that there is a connection between feed-in management measures and grid congestion in the transmission grid with high feed-in by wind turbines, which is particularly evident in the grid area of Schleswig-Holstein.
Figure: Correlations between the relative, regulated energy of the DSO and the relative photovoltaic or wind feed-in power of the respective TSO.