Clip at the AC nameplate

Method

The array always operates at its maximum-power point. The AC output is read on the efficiency law at the array's maximum power and cut at the AC limit; the part above the limit is lost to the power limit. The AC limit is the nameplate, times the power factor when the nameplate is apparent power. No current-voltage curve is used. There is no MPPT window, no DC current limit, no temperature schedule of the nameplate and no start threshold besides the efficiency law's own. With a grid power limitation switched on, the cut is the lower of the nameplate and the inverter ceiling the limitation sets.

The math

1. AC limit
2. AC output and lost power

$$P_{lim} = \min\big(\text{PF}\,P_{nom,inv},\ P_{lim,grid}\big) \tag{1}$$ $$P_{ac} = \min\big(P_{out}(P_{mpp}),\ P_{lim}\big),\qquad \Delta P = \max\big(0,\ P_{out}(P_{mpp}) - P_{lim}\big) \tag{2}$$

where

Symbol	Meaning	Unit
$P_{lim}$	the AC limit of one inverter	W
$\text{PF}$	the power factor when the inverter nameplate is apparent power (Losses tab), else 1	—
$P_{nom,inv}$	the inverter's AC nameplate	W
$P_{lim,grid}$	the ceiling of one inverter that the Grid power limitation step sets; no bound when the limitation is off or 0 kW	W
$P_{ac}$	the AC output	W
$P_{out}(P)$	the AC output the efficiency law gives for the DC input $P$	W
$P_{mpp}$	the array power at its maximum-power point after the DC losses	W
$\Delta P$	the AC power lost to the power limit	W

References

1. King, Gonzalez, Galbraith & Boyson 2007, Performance Model for Grid-Connected Photovoltaic Inverters, Sandia report SAND2007-5036
2. NREL SAM Simulation Core (SSC) source code, release 2026.7.3, github.com/NatLabRockies/ssc: shared/lib_sandia.cpp, sandia_inverter_t::acpower(); ssc/cmod_pvwattsv8.cpp, the inverter parameters and the clipping

API

inverter.operating_point = ac_clip

Symbols follow the symbol registry.