Patent ID: 7977812

Claim:
An electric power system for a vehicle performing a regenerative electric power generation using a regenerative brake during a vehicle speed reduction, and performing a regenerative electric power discharging after the vehicle speed reduction, the electric power system comprising: an alternator equipped with a rectifier and a regulator having a field current control switch, which is driven to generate an electric power by a rotary power supplied from an internal combustion engine of a vehicle, and an output voltage of which is converged to an adjusting voltage by a feedback control of a field current duty cycle as a duty ratio of the field current control switch; a first storage device, to be charged with the electric power generated by the alternator, and which discharges the electric power to electrical loads, wherein the first storage device is directly connected to the alternator and the electrical loads; a second storage device, to be charged with a regenerative electric power which is generated by the alternator during a vehicle speed reduction or a vehicle braking, and which discharges the stored regenerative electric power after completion of the vehicle speed reduction; an electric power converter for a bi-directional electric power transmission which transmits the electric power between the first storage device and the second storage device which are electrically connected through the electric power converter; and a control device which controls operation of the alternator and the electric power converter so that the second storage device is charged with the regenerative electric power generated by the alternator using the regenerative brake during the vehicle speed reduction, and the second battery discharges the stored regenerative electric power to the electrical loads through the electric power converter after completion of the vehicle speed reduction, wherein during the regenerative electric power generation, the control device instructs the electric power converter to transmit a residual generated electric power in a forward electric power transmission from the alternator to the second storage device while a terminal voltage of the first storage device is maintained within a specified voltage range, in which the residual generated electric power is obtained by subtracting an electric power to be consumed by the electrical loads and an electric power with which the first storage device is charged from a maximum generated electric power of the alternator, and during the regenerative electric power discharging, the control device instructs the electric power converter to transmit the electric power in a backward electric power transmission from the second storage device to the first storage device so that the electric power generated by the alternator is not more than a specified value while the terminal voltage of the first storage device is maintained within a specified voltage.