Gumbel copula based multi interval ramp product for power system flexibility enhancement

Abstract

High renewable penetration in modern power systems increases uncertainty and variability of net load, causing frequent real time system imbalances. This necessitates increased generation flexibility to mitigate such imbalances. Regulation services and transfer tie lines enhance system flexibility, but limited availability of conventional generating units with lower operational time frame and the associated high investment reduces their applicability. This requires development of flexible ramp products (FRP) to maintain real time power balance. FRP design should consider both variability and uncertainty of net load, with accurate uncertainty modeling. Existing ramp product design uses approximate net load uncertainty, which reduces their effectiveness. Further, existing FRP design primarily focus on wind dominated systems. Rapidly increasing solar generation from utility level plants show higher variability than wind in very short time frames. Rapid coherent changes from such plants cause massive generation variation. Considering very short term uncertainty and variability of utility level solar plants, this paper proposes a novel multi-interval FRP design based on net load forecasts. Proposed FRP design considers both start and end time uncertainty of each time interval, compared to existing end time uncertainty based designs. To enhance the net load uncertainty estimation accuracy, proposed model uses Gumbel copula function based joint probability distribution (JPD) of load, solar and wind forecasting errors, because it covers all extreme forecasting errors due to max-stable property. Results show that proposed design effectively manages the variability and uncertainty of net load, offering significant cost savings.