Inverter Over-power

It may be that the inverter is unable to reduce the DC power in order to observe the AC power limit. Normally the inverter would increase the input voltage above the MPP, which would result in a reduced current and reduced DC power entering the inverter. However, the maximum DC voltage, or the minimum DC current may prevent this.

In some scenarios the inverter is forced to shut down as there is no operating state that observes all the constraints. This is termed an over-power shutdown and SolarFarmer calculates losses from such events.

The calculation is complicated in the multi-input inverter case as there are many ways in which the inverter might try to find a workable operating condition. It may be that it switches one input off but continues to operate the others.

The SolarFarmer calculation proceeds by finding the minimum power operating point for each inverter input as well as the maximum power point. It then assumes that each input can provide any power in the range defined by the minimum and maximum power points. It combines these ranges across the multiple inputs, and applies the inverter efficiency model to convert them to AC power ranges.

It then looks to see if there is an operating range that covers the inverter AC maximum limit \(P_{\text{inv,max}}(T_{\text{a}}(t))\).

If there is, then the inverter outputs \(P_{\text{inv,max}}(T_{\text{a}}(t))\), otherwise the output is taken as the top of the highest range that is below \(P_{\text{inv,max}}(T_{\text{a}}(t))\).