## Inverter Efficiency Curve

The efficiency curve of an inverter corresponds to a family of curves with varying DC link voltages. In the present version of the model, it is possible to define a single curve only, which is generally selected considering the rated DC link voltage. It can be defined through property Eff Curve of each DER, for which a XY Curve object that characterizes the variation of the inverter efficiency as a function of Pdc, the DC power in per unit of its kVA rating, must be assigned. For PVSystems, Pdc varies with Pmpp and ambient conditions, so the calculation of the efficiency is straight forward, whereas for Storage, as active the power is defined first at the interface with the grid, the calculation is backwards, i.e, an efficiency and a DC power that leads to the given AC power are calculated simultaneously. Refer to [2] and [3] for detailed information. An example of how to define a XYCurve object is shown below. If Pdc goes beyond the highest or lowest value of xarray, OpenDSS calculates the corresponding efficiency by assuming the same slope of the two nearest points defined.

New XYCurve.Ef f npts=4 xarray =[ .1 . 2 . 4 1 . 0 ] yarray =[ .86 . 9 . 9 3 . 9 7 ]