Flexible distribution network - Local flexibility and aggregation
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- Institutt for elkraftteknikk 
The increasing intermittent production from wind power and solar-PV creates a system that is more complex to plan, control and balance. At the same time, there is an increase in power consumption due to electric vehicles, heat pumps and other energy-intensive appliances. The volatile system indicates a need for flexibility. The flexibility could come from distributed generation (DG), local storage or flexible demand. However, the contribution from a single resource may be too small to make an impact or to participate in the markets. Aggregation is therefore in most cases necessary. The aggregated flexibility could then be used to provide services to the balance responsible party/supplier, the transmission system operator or the distribution system operator. One part of this MSc-thesis is dedicated to the aggregator role and its responsibilities and interactions with other power system participants. The other part is a simulation evaluating the potential for a demand response aggregator in the Norwegian markets compared to the German markets. The aggregator role could be taken care of by the BRP/supplier or a third party (independent) aggregator. One of the main problems for an aggregator is related to the interaction between a potential third party aggregator and the BRP/supplier. When the aggregator activates demand response in the balance area of the BRP, an imbalance will appear. Additionally, the energy sourced by the supplier will be diverted and sold by the aggregator. The financial adjustment solutions used in many European countries today, does not offer satisfactory results for all cases. In Norway, this is avoided by requiring that all aggregators must act as the BRP for their customers, which excludes third party aggregators. This could however inhibit the development of aggregators, as they would have to compete against existing participants in the supplier market. Standardized contracts between the third party aggregator and BRP/supplier should therefore be in place to simplify the relation. The system that is used for simulation in this thesis is an urban area in the city centre of Stavanger in Rogaland, Norway. The electric vehicles and water heaters were controlled in order to evaluate the potential to provide a range of flexibility services. Day-ahead, intraday, regulating power and primary reserves markets were assessed. The water heater model is based on consumption data from ElDek, a SINTEF project uncovering residential electricity usage. For the electric vehicle, vehicle-to-grid operation is taken into consideration with its accompanying battery degradation costs. The potential profit for individual players was evaluated in the current Norwegian markets, and was compared to the potential in the German markets. As one can expect, the incentives for a demand response aggregator in a Norwegian setting was found to be too low. Most likely, the necessary flexibility can be handled by price signals from the DSO and supplier, without the need for an aggregator of residential demand. This may however change with increased market integration and growth of renewable energy sources. The German market showed some potential for an aggregator, especially for electric vehicles. The reason is the high volatility in the markets, indicating a high need for flexibility. It is however expected that aggregators in Europe will continue to focus on large electricity consumers for time being.