In order to avoid the need for AC Neutral.I am still uncertain as to why the TS is needing to substitute for solar power into a solar charge controller to charge a battery.
Definitely a misunderstanding of the purpose of the Neutral.
The entire use of a solar charger powered from a DC power supply is a complicated way of achieving what a ordinary battery charger does more effectively. All AC devices require connection across an AC supply - one being 'neutral' is irrelevant.