Optimal operation of hybrid power plants: a case study of an operation park in Sweden

Hybrid power parks (HPPs) that combined renewable power sources and storage can improve generation flexibility compared to single-resource parks, making HPPs able to participate in different electricity markets, e.g., regulating markets. Despite the foreseen advantages with HPPs, a challenging aspect relate to coordination of the included assets due to the stochastic nature of wind production, solar production and electricity prices. In this work, we utilize an energy management system (EMS) that optimally coordinate the power output from the included generation units with the objective to maximize the profit. More specifically, the EMS is multi-time scale rolling optimization framework including spot market optimization and balancing market optimization, where bids in the spot market and balancing market are updated sequentially. Besides, a detailed battery degradation model is included to quantify the non-linear degradation cost of battery storage system. The EMS is implemented using data from an operational 3.7 MW co-located wind and solar park on the west coast of Sweden. Results show that a battery with a size of up to 2 MWh will increase the unit profit when trading in the day-ahead and regulating market compared to having no battery. Higher energy capacity will result in degradation costs that are too high compared to the additional incomes. Oversizing the park, i.e., installing more capacity than stipulated in the connection agreement with the system operator, impacts the amount traded electricity in the regulating market. At the same time, curtailment losses are increased in a non-linear manner while the unit profit is not much impacted by the different grid connection capacities. When adding the opportunity for the park to trade in the regulating market, as compared to solely the day-ahead market, profits are increased by 3.9%.