AC Collectors

AC power transmission between the inverters and transformer(s) (either the first level transformers if present, or the transmission step-up transformer directly) will incur power losses. After the first step-up transformer, AC collection effects are neglected as insignificant.

The user will input a power loss factor for the inverter-to-transformer wiring for each inverter, representing the ohmic power loss in % when the load on the wire is equal to the inverter maximum AC output power (here denoted \(P_{\text{inv,ACmax}}\)). This loss factor may be specific to each array if the inverter-transformer connections are dissimilar to one another, and we denote it \(L_{\text{r,inverter}}\).

So if the power available at the transformer inputs when the load is equal to the maximum AC output power of the inverter is \(P_{\text{inv,ohmic,ACmax}}\) then

$$P_{inv,ohmic,ACMax} = P_{inv,ACmax} \bullet (1 - L_{r,inverter})$$

The ohmic power loss incurred will vary with the square of the load, meaning that at time t the array power available at the inputs of the transformer from each inverter after ohmic AC wiring losses is given by:

$$P_{inv,trans}(t) = P_{\text{inv}}(t) - \frac{P_{\text{inv}}^{2}(t)}{P_{inv,ACmax}}*L_{r,inverter}$$

The AC Collector effect is calculated across all such connectors in the PV plant:

$$\Delta_{\text{ACcoll}} = \left( \frac{\sum_{i = 1}^{N_{\text{inverters}}}{\sum_{t}^{}{P_{inv,trans}(t)}}}{\sum_{i = 1}^{N_{\text{inverters}}}{\sum_{t}^{}{P_{\text{inv}}(t)}}} - 1 \right) \bullet 100%$$

For annually-representative AC Collection Effect values, remember to de-season.