*2.4. Array Control through DC/DC Boost Converter*

The array controller, as displayed in Figure 5, provides primary frequency support through fixed droop and virtual inertia control. It also tracks the required set-point for the array and implements the commands from plant control. It accomplishes these tasks by controlling the DC/DC boost controller to which the array is connected, as can be seen later in Figure 6.

**Figure 5.** Array control with fixed droop, secondary control, virtual inertia control and curtailment control.

**Figure 6.** Array control through DC/DC boost converter and inverter control.

The signal Δ*P\_PV*, from plant control, as shown in Figure 3, is shared among the arrays by the ratio of reserve power from each array to the total amount of reserve of the entire plant. Certain arrays of the plant may be completely or partially shaded and, hence, their temperatures will also be different, as will their power output and reserve levels. Thus, the set-point from plant control is divided among the arrays in proportion to their reserves such that the array with largest amount of reserves participates more. This generates the signal Δ*Psec*, as shown in Figure 5, using

$$
\Delta P\_{\rm scc} = \frac{\Delta P\_{\rm -} P V \, R\_n}{\sum\_{n=1}^{N} R\_n} = \frac{\Delta P\_{\rm -} P V (1 - K c\_n) N N \\_P\_n (G\_n, T\_n)}{\sum\_{n=1}^{N} (1 - K c\_n) N N \\_P\_n (G\_n, T\_n)},\tag{10}
$$

where *Rn* is the reserve of array *n*. The array control also consists of the conventional droop control to produce Δ*Pprim*. The inertia control is formulated as the rate of change of frequency (ROCOF)-based controller, as given below, to produce Δ*Pin*.

$$
\Delta P\_{\rm in} = -2H\_{\rm syn} \frac{df}{dt}\_{\prime} \tag{11}
$$

where *Hsyn* is the synthetic inertia coefficient, and *f* is system frequency. Adding inertia, droop, and plant control to the desired steady-state curtailed output *PPV* produces the real operating point *P\**, where *P\** is limited by the MPP and 0.

This real operating point *P\**, along with the average irradiance over *n*-th array *Gn* and array temperature *Tn*, is used as input to NN\_V, to produce *Vdc'* as the output of NN\_V. This DC voltage is further corrected with the help of an integrator to remove NN error and produce *Vdc"*, which is tracked by the DC/DC boost converter. For this paper, each array is assumed to be curtailed to 10% below its MPP unless purposely curtailed further. The terminal voltage of the PV array is controlled using DC/DC boost converters, as illustrated in Figure 6. The neural networks used for array control are described in the next subsection.
