Worst Expected Ramp Rates from Cloud Speed Measurements
Guang Chao Wang1, Juan Bosch2, Ben Kurtz1, Inigo de la Parrra3, Elynn Wu1, Jan Kleissl1
1Center for Renewable Resources and Integration, University of California San Diego, La Jolla, CA, United States
/2Department of Electrical and Thermal Engineering, University of Huelva, Huelva, Spain
/3Institute of Smart Cities, Department of Electrical, Electronics, and Communications Engineering, Public University of Navarre, Pamplona, Spain

Large PV power ramp rates are of concern and sometimes even restricted by grid operators. Battery energy storage systems (BESS) can smooth the power output and maintain ramp rates with permissible limits. To enable PV plant and BESS design and planning, a method to estimate the largest expected ramps for a given location is proposed. Because clouds are the dominant source of PV power output variability, an analytical relation between the worst expected ramp rates, cloud motion vectors, and the geometrical layout of the PV plant is developed. The ability of the proposed method to bracket actual ramp rates is assessed under different meteorological conditions. The method delivers a 96% compliance rate as evaluated within 1-min time windows.