Solar Lattice

FailureMode

Inverter clipping

ID
fm:inverter-clipping
IRI
https://solarlattice.org/kb/fm/inverter-clipping
Status
active
Also known as
Clipping

Inverter clipping happens when the array's DC power is more than the inverter's rated AC output, so the inverter limits production to its own maximum. It is not always a fault, because some systems are designed to clip so they produce more in the morning and evening. In monitoring data, output is held flat at the inverter's power ceiling, and most of the lost energy falls on the sunnier days. Performance monitoring tools can estimate the clipped energy by working out the DC size and AC capacity and finding the periods when the AC limit caps output. Do not mix it up with voltage flooring, which is an MPPT limit caused by the DC voltage window. To tell them apart, check DC voltage, AC voltage and reactive power against the Vmp from the IV curve. Also check tracker stow logs and wind data against production so that stow dips are not counted as clipping.

<!-- review notes

Claims

affects

c1 drafted · lead Inverter

caused_by

c2 drafted · lead High DC/AC ratio

Happens when the array's DC power is larger than the inverter's rated AC output. Designers sometimes oversize the array on purpose to get more energy in the morning and evening.

presents_as

c3 drafted · lead Flat capped output

The inverter holds output at its maximum rating, which acts as a power ceiling. Most of the lost energy falls on the sunnier days.

review note: support check: partial - Passages say the inverter limits output to its maximum (a power ceiling) and that losses fall mainly on sunnier days, but never describe a flat capped output signature explicitly.

detected_by

c4 drafted · lead Performance monitoring

Monitoring algorithms work out the DC size and AC capacity, then calculate the clipped energy wherever the AC limit caps the expected output.

distinguished_from

c5 drafted · lead Inverter Voltage Floor Losses — told apart by IV curve tracing

Clipping is a power ceiling. Voltage flooring is an MPPT limit set by the DC voltage window: the operating voltage stays above the Vmp from the IV curve, and the power stays below the Pmp from the IV curve.

c6 drafted · lead Tracker Wind Stow Production Losses — told apart by Tracker command log review

Line up the timestamps of tracker stow commands and wind data with SCADA production, irradiance and inverter status. Stow dips follow wind events. Clipping follows the inverter's AC limit.

review note: support check: partial - Passages say to align stow commands, wind data with SCADA production, irradiance and inverter status to separate stow loss from clipping, and stow follows wind; but the claim that clipping follows the AC limit is not stated in that passage, and the method is log review rather than a named differentiator.

Referenced by

Data