Photovoltaic inverter saturation

Inverter saturation, commonly referred to as “clipping”, occurs when the DC power from the PV array exceeds the maximum input level for the inverter. In response to this condition, the inverter typically adjusts DC voltage to reduce the DC power. This is done by increasing voltage above the MPP voltage, thus reducing DC current.

PV system modeling is primarily done on hourly timescales and so cannot capture subhourly effects, including inverter saturation. Inverter saturation occurs when the potential dc power, P dc, produced by the collectors is greater than the inverter capacity, and some of the PV power is lost or “clipped.”

A: On days of Solar Saturation the network voltage is a direct result of the inverters trying to put power back into the grid; adjusting the voltage at the supply transformer will have no effect as the voltage in the area is dictated by the inverters competing against each other.

Therefore, the four PV inverters are also operating in the same current-saturation state in this case. The grid strength of the main grid is defined by the short-circuit ratio (SCR) such that: S C R = | u t h / z t h |. Then, different main grid strengths can be tested by modifying the Thévenin equivalent impedance, z t h.

In response to this condition, the inverter typically adjusts DC voltage to reduce the DC power. This is done by increasing voltage above the MPP voltage, thus reducing DC current. Most, but not all inverters self-limit.

A: In South Australia the upper limit of the inverter is allowed to be set at 258volts, which on rare occasions during Solar Saturation, has the ability to raise the grid voltage outside of Australian standards. Q: Can SA Power Networks turn down the voltage so my inverter won't cut out?