Night Time Tare Loss

When the inverter is unable to operate (at night i.e. when \(G_{\text{h}}=0\), or during the day when no operating point within the inverter's envelope is available), the inverter will be shut down and its control systems will consume a normally small and constant amount of power known as the Night-Time Tare Loss, supplied by the user in Watts sourced from the inverter specification (\(P_{\text{inv,tare}}\)). As the array will not be generating at these times, the consumed power is supplied by the grid to which the plant is connected. Hence at time \(t_{\text{nop}}\) when the inverter is unable to operate:

$$P_{\text{inv}}(t_{\text{nop}}) = {- P}_{inv,tare}$$

In order to evaluate the Inverter Tare Loss Effect over any period, the amount of power consumed by the inverter when shut down is compared to the amount of power exported by the inverter at other times:

$$\Delta_{\text{tare}} = - \left( \frac{\sum_{i = 1}^{N_{\text{inverters}}}{\sum_{t}^{}{P_{\text{inv}}\left( t_{\text{nop}} \right)}}}{\sum_{i = 1}^{N_{\text{inverters}}}{\sum_{t}^{}{P_{\text{inv}}\left( t_{\text{operating}} \right)}}} \right) \bullet 100%$$

As the power consumed by the inverter is supplied from the grid, additional power will be consumed by the transformer(s) and AC collectors in supplying this power to the inverter. This additional power consumption is not included in the Tare Effect calculation, but instead in the AC Collector and Transformer calculations.

The final time series of inverter output power \(P_{\text{inv}}(t)\) is created by splicing \(P_{\text{inv}}(t_{\text{operating}})\) at times when the inverter can operate with \(P_{\text{inv}}(t_{\text{nop}})\) when it is not.