Abstract: A method and system for controlling an alternator in a power supply system for a vehicle utilizing a digital current control or compensation algorithm. The alternator has field windings and provides an output current as a function of field voltage across the field windings. The alternator is controlled by a microprocessor-based voltage regulator programmed with the algorithm in response to a reference control signal and a load demand signal based on the current demand of the electric load. Desired responses of the alternator to corresponding current demands are defined by a data matrix of system operating coefficients. A set of the coefficients is selected based on the load demand signal and the set is used with the algorithm to calculate a desired field voltage so that the output current is responsive to variations in system load demand.