Count as an MPPT minimum loss — MPPT minimum loss row

Method

The power lost at the MPPT minimum is counted in the voltage-threshold row, Inverter Loss due to voltage threshold. Two cases stay in the power-limit row, Inverter Loss over nominal inv. power, because the AC limit decides them (1). The first is a floor point that still exceeds the AC limit, where the voltage is raised from the floor. The second arises with the MPPT minimum option Hold the MPPT minimum, fitted voltage trim: an array whose open-circuit voltage less the cable drop is below the floor while its maximum power would exceed the AC limit at the floor voltage. The rest of the loss goes to the voltage-threshold row (2).

The math

Power-limit row
Voltage-threshold row

L_P = \begin{cases} \Delta P & P_{out}(P_{op},\ V_{min}) > (1 + k_{ol})\,P_{lim} \\ \Delta P & U_{oc} - R_w\,I_{mpp} < V_{min} \text{ and } P_{out}(P_{mpp},\ V_{min}) > P_{lim}\text{, fitted-trim floor only} \\ 0 & \text{otherwise} \end{cases} \tag{1}

L_V = \Delta P - L_P \tag{2}

where

Symbol	Meaning	Unit
$L_P$	the loss counted in the power-limit row	W
$\Delta P$	the power lost at the MPPT minimum, after the AC-limit rule has raised the voltage when it applies	W
$P_{out}(P, U)$	the AC output of the efficiency curves at DC power $P$ and voltage $U$	W
$P_{op}$	the array power at the floor	W
$V_{min}$	the minimum MPP voltage, the bottom of the inverter's MPPT window	V
$k_{ol}$	the overload tolerance on the AC limit, 0.2 %	—
$P_{lim}$	the AC limit of one inverter at the timestep: its nameplate, derated with the ambient temperature and lowered by a grid power limitation	W
$U_{oc}$	the array's open-circuit voltage at the modules	V
$R_w$	the resistance of the DC cables between the modules and the inverter	Ω
$I_{mpp}$	the array's maximum-power current of the timestep	A
$P_{mpp}$	the array power at its maximum-power point after the DC losses	W
$L_V$	the loss counted in the voltage-threshold row	W

References

PVsyst 8 help, Inverter model and operating limits

API

inverter.vmin_loss_bucket = vmin

Symbols follow the symbol registry.