Practical aspects and results - Providing secondary frequency regulation from a single Type 4 wind turbine and a battery storage system

Wind turbines and battery storage systems are both capable of providing several ancillary services to the grid. Despite several demonstration projects in existence, empirical data examining the real-world performance of such systems in providing ancillary services is limited. This work analyses empirical data to demonstrate how a commercial wind turbine plus battery storage system can be used to provide secondary frequency regulation. The system used consists of one 800 kW, IEC Type-4 wind turbine (full converter) and a 744 kWh lithium-ion battery storage system. We use historical AGC signals with a 2 s update interval in accordance with real-world conditions. The wind turbine is not curtailed and no wind forecast is used. We examine the performance of the battery separate from the combined system and in both cases the battery is the primary provider of AGC action and error correction. When operating with the wind turbine, the battery corrects for error between the estimated and measured wind turbine power in addition to the AGC bias value. We use performance scoring methods from the National Research Council, Canada and the Pennsylvania-Jersey-Maryland (PJM) system operator. We report PJM performance scores of 94% for the battery alone and 72% with the combined system. Using 2017 PJM market price data, we estimate an additional regulation market income of 12% over providing energy alone with the regulation bid magnitude tested.