NOVELTY - The method involves providing a photovoltaic device (32) i.e. photovoltaic cell, with variable direct current (DC) voltage and DC current outputs. A DC power supply (38) is connected in a parallel/series combination with the device. A DC load (40) is connected to a combination of the power supply and photovoltaic device such that the load is powered by the combination. A characteristic of the power supply is adjusted such that the voltage and current outputs of the photovoltaic device match voltage output and current output levels corresponding to predetermined desired power point.    USE - Method for controlling a photovoltaic system for a building. Uses include but are not limited to a heating, ventilation, air conditioning (HVAC) applications, lighting applications, refrigeration applications, data center applications, electric vehicle (EV) charging applications, ventilation system applications e.g. ceiling fan and motor.    ADVANTAGE - The method enables the photovoltaic device current and voltage monitored by the DC power supply to limit number of separate devices in the photovoltaic system. The method enables the photovoltaic device to operate at or near a most efficient power point or other desired power point on an I-V curve, so that an inverter and a DC optimizer can be eliminated or reduced in size/complexity for photovoltaic installations. The method enables controllable and variable string inverters to be used on individual parallel photovoltaic module strings without a central inverter on a photovoltaic array, so that string inverters can keep each string operating at or close to maximum power point (MPP), while optimizing intermediate DC bus voltage to the condition of the DC loads to minimize electrical losses.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit block diagram of a DC micro-grid of a photovoltaic system.    DC micro-grid (30)    Photovoltaic device (32)    Controllable inverter (34)    Electrical grid (36)    DC power supply (38)    DC load (40)