When calculating the Vd, for the purposes of the system, nominal system voltage is used per the formula cited from the NEC, article 690 (per solar
section,moderating calls, etc.). The higher voltages would not be used as they are generally open circuit voltages and relative to the panel and cell type, mono-crystalline, polycrystalline, cigs or amorphous. As the charging
occurs from a potential of higher voltage to the lower nominal system voltage, it is a static picture of a dynamic situation that constantly adjusts itself, hence the value of MPPT
I. Tracking on both sides of the system.. If one was able to bring the voltage in at a higher level because of the capability of the charge controller to take a higher series voltage from the panels
to the controller and then reduce it to an input voltage considerably lower for nominal system voltage, that would be preferable but, again, the prospect of shading would lead to a potential loss of the entire array in some cases, depending on what cells might vibe shaded. Thus, it would seem to be optimal to maintain charging
closer to the nominal system voltage level, run the panels
to a centrally located buss bar, from there to a controller located the minimal distance necessary to the battery
bank and call it good. Strategic minimization of distance, consequently wire sizing and expense are reflected in the choices and location of the balance of system components. Energy efficiency = cost efficiency.