Parabolic voltage blend

Method

The AC output is read on each of the three measured curves at the timestep's DC input, and a parabola through the three values is evaluated at the DC voltage. Each curve is read by linear interpolation in the DC input, from zero output at the power threshold, and extended along its last segment above its last point. Outside the measured voltages the nearest curve applies, so the parabola is never extended beyond them. With two curves the blend is linear. With one curve, that curve applies at every voltage; with none, the maximum efficiency applies above the threshold.

The math

$$P_{out}(U) = \sum_{k=1}^{3} P_{out,k} \prod_{j \ne k} \frac{U - U_j}{U_k - U_j} \tag{1}$$

where

Symbol	Meaning	Unit
$P_{out}(U)$	the AC output at DC voltage $U$	W
$P_{out,k}$	the AC output read on the curve measured at voltage $U_k$	W
$U_k, U_j$	the three measured voltages	V

API

inverter.efficiency_interpolation = parabolic_voltage_blend

Symbols follow the symbol registry.