Inverter clipping
AC power held flat at the inverter rating while DC is available.
Inverter clipping is when DC array power exceeds the inverter’s AC rating and the inverter caps output at its limit, discarding the surplus. Some clipping is designed-in (high DC/AC ratio); excess or unexpected clipping signals an oversized array, a derated inverter, or a thermal limit, and is lost energy you can quantify.
Symptoms
- AC power flatlines at the nameplate limit during peak irradiance.
- A characteristic flat-topped "mesa" shape on the midday power curve.
- Clipping appears earlier in the day or at lower irradiance than expected.
SCADA signatures
- Pac pinned at the rated value while Pdc (or string currents) keep rising.
- Clipping hours accumulate beyond the design DC/AC ratio expectation.
- Unexpected clipping correlated with high heat-sink temperature = thermal derate, not design.
Root cause
Designed clipping comes from a deliberately high DC/AC ratio that boosts morning/evening capture. Problematic clipping comes from thermal derating (cooling fault), a misconfigured power limit, or an array expansion the inverter was never sized for.
Financial impact
Modelled clipping is an economic choice; unexpected clipping is pure loss. A thermal-derate that clips an extra 60 kW for three midday hours across a summer can quietly erase tens of MWh — invisible unless you separate expected from anomalous clipping.
How NuraVolt detects it
NuraVolt compares observed clipping against the plant’s designed DC/AC ratio and a clear-sky expected-power envelope, then attributes the surplus loss. When clipping correlates with rising heat-sink temperature it is reclassified as a cooling/derate fault rather than benign design clipping.
Frequently asked questions
See also
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