PV- and Battery-Ratio for very large Modular PV Parks with DC Coupled Battery Converters

Dropping storage and PV panel prices are benefiting large PV projects in the megawatt range with integrated battery storage systems (BSS). This paper introduces a modular design approach such for large PV-battery parks. With this approach a dispatchable generation for arbitrary load-profiles for volatile PV power by means of batteries is achieved. The park is comprised of multiple central inverters, which can have differently sized DC coupled storage systems. The focus of this paper lies on the trade-off between the oversizing of the PV array and the dimensioning of the storage system, so that the delivered energy at the point of common coupling (PCC) of every central inverter has less to no volatilities. A tool, which uses PV UI curves of one year for four different locations to find a ratio between the installed PV panel power and the battery capacity for every desired power duration, has been developed. A distinction between limited and unlimited charging power is made and the dependency of the nominal capacity of both parameters to the equivalent full load hours is evaluated. In addition, the influence of the sizing of the PV array and the battery on the dc-link voltage and filter selection is investigated.