Grid integration of big photovoltaic farms with energy storage support

Abstract

This report deals with two types of network code requirements that apply to big photovoltaic installations and cannot be met with the use of inverters but require energy storage. The first of these requirements is frequency response. It prescribes how much the active power output of a photovoltaic installation should change when system frequency deviates from the nominal frequency in order to support the grid. The second requirement is the maximum ramping rate which determines by how fast the active power output of a photovoltaic installation may vary due to changing cloud cover or other factors. The report classifies the network codes into three grades of severity. Two methods to size the required storage capacity for different grades of severity are explained with corresponding examples. The report concludes that improved storage sizing methods should be developed as there is clear potential for significant reductions in required storage capacity.