A Hybrid System of Li-Ion Capacitors and Flow Battery for Dynamic Wind Energy Support

Wind farm output power fluctuations create adverse effects on the voltage, frequency, and transient stability of the utility grid. Short-term wind farm power variations with high ramp rates can cause voltage instabilities, particularly if the farm is located in weak-grid areas. The integration of wind energy with energy storage devices to support the short-term shortcomings of wind energy is discussed in this paper. A turbine level hybrid configuration of an energy storage system is used to limit the power ramp rates and apply power smoothing. The proposed energy storage devices are the zinc bromide flow battery and lithium-ion capacitors. The actual models for the battery and capacitors used in this study are derived from laboratory tests. The wind farm power is also modeled using measured wind speed data. A new concept has been introduced to evaluate the effectiveness of energy storage system for wind energy support. The analysis shows that significant improvements can be made to shape the output power of the farm using energy storage systems.