Process for controlling a desalination plant comprising at least: - a line for feeding seawater to at least one filtration unit equipped with reverse osmosis tangential flow filtration membranes (12, 12a, 12b), said feed line being successively equipped, starting from its inlet, with a low-pressure first pump and a high-pressure second pump, the flow rate of which is proportional to the speed of rotation, - a permeate discharge line for discharging permeate from the membranes to a fresh water treatment and storage unit (15, 16), - a concentrate discharge line, - a loop branched off the feed line upstream and downstream of the high-pressure pump, the loop passing through an energy recovery unit equipped with a pressure exchanger and a pump referred to as a booster pump, said loop also being connected to the concentrate discharge line, said discharge line passing through the pressure exchanger, - current supply means for supplying current derived from a renewable energy source and subsequently supplying variable powers to the low-pressure, high-pressure and booster pumps, the supply means comprising a photovoltaic generator supplying each of the low-pressure, booster and high-pressure pumps by means of a respectively first, second and third variable frequency power converter, said power converters being controlled according to an MPPT (maximum power point tracking) protocol. characterized in that the control process comprises at least one operating mode in which: - the flow rate Q 25 in the concentrate discharge line is maintained, while it passes into the energy recovery unit, at a value substantially equal (the difference between the flow rates not exceeding 5%) to that of the flow rate Q 13 of the booster pump, which is itself maintained above a threshold Q 13min, corresponding to the minimum flow rate Q 12min required for the operation of the filtration units, - the pressure at the outlet of the booster pump is maintained at a value equal to that of the pressure at the outlet of the high-pressure pump, - the flow rate Q 7 of the high-pressure pump is a function of the frequency and of the power of the current supplied by the supply means, so that the flow rate Q 24 of permeate at the outlet of the at least one filtration unit (12, 12a, 12b) is substantially equal (the difference between the flow rates not exceeding 5%) to the flow rate Q 7 of the high-pressure pump. - a line for feeding seawater to at least one filtration unit equipped with reverse osmosis tangential flow filtration membranes (12, 12a, 12b), said feed line being successively equipped, starting from its inlet, with a low-pressure first pump and a high-pressure second pump, the flow rate of which is proportional to the speed of rotation, - a permeate discharge line for discharging permeate from the membranes to a fresh water treatment and storage unit (15, 16), - a concentrate discharge line, - a loop branched off the feed line upstream and downstream of the high-pressure pump, the loop passing through an energy recovery unit equipped with a pressure exchanger and a pump referred to as a booster pump, said loop also being connected to the concentrate discharge line, said discharge line passing through the pressure exchanger, - current supply means for supplying current derived from a renewable energy source and subsequently supplying variable powers to the low-pressure, high-pressure and booster pumps, the supply means comprising a photovoltaic generator supplying each of the low-pressure, booster and high-pressure pumps by means of a respectively first, second and third variable frequency power converter, said power converters being controlled according to an MPPT (maximum power point tracking) protocol. - the flow rate Q 25 in the concentrate discharge line is maintained, while it passes into the energy recovery unit, at a value substantially equal (the difference between the flow rates not exceeding 5%) to that of the flow rate Q 13 of the booster pump, which is itself maintained above a threshold Q 13min, corresponding to the minimum flow rate Q 12min required for the operation of the filtration units, - the pressure at the outlet of the booster pump is maintained at a value equal to that of the pressure at the outlet of the high-pressure pump, - the flow rate Q 7 of the high-pressure pump is a function of the frequency and of the power of the current supplied by the supply means,