Managing connection queues in distribution networks with flexible connection agreements

In this paper, we evaluate flexible connection agreements and alternative curtailment rules to manage connection queues in distribution networks. We consider fairness, which we approximate by the equal or unequal treatment of the generators who are curtailed, and efficiency, which we approximate by the number of renewable generators we can connect to the distribution network, and the total volume of renewable energy they can generate after connection. The numerical simulation starts from an urban synthetic network topology developed by the Joint Research Centre (JRC) on the basis of real data coming from European DSOs. To assess whether a renewable generator can be connected to the distribution network, we apply an Optimal AC Power Flow. We demonstrate how variations in terms of grid observability and maximum curtailment capacity of flexible connection agreements can be used to arrive at an outcome that is in between the extremes of Technical Best (the benchmark for efficiency with no consideration of fairness) and ProRata (the benchmark for fairness without consideration of efficiency). Furthermore, we find that introducing a maximum capacity constraint comes at the cost of rejecting connection requests of generators. This amount is higher when flexible capacity is negotiated individually rather than fixed, as the negotiated approach tends to allocate network capacity to early-assessed generators entering (almost) firm connection agreements, leaving little network capacity available for generators at later stages of the connection queue. Finally, we illustrate that when constraining flexible capacity, the connected generators can also benefit from reduced variability and unpredictability of curtailment when more generators connect to the grid. This work aims at providing support for DSOs and regulators to understand the implications of different curtailment rules on generators connection, curtailment and fairness.