A power supply system that supplies electric power to a load comprising: a first power storage device; a second power storage device; a power line for transmitting electric power input and output to and from said load; a converter for executing bidirectional DC voltage conversion between said first power storage device and said power line; a switch connected between said second power storage device and said power line; and a control device that controls ON/OFF of said switch and said converter, when said switch is OFF, said control device performing voltage control of said converter so that a voltage value of said power line becomes a voltage command value, wherein said control device includes: a switching unit that switches ON and OFF of said switch in accordance with an operating state of said load; a voltage control unit that performs voltage control of said converter in accordance with an output of a voltage feedback control element including at least an integral element that integrates a deviation of the voltage value of said power line from said voltage command value; characterized by when said switch is ON, said control device performing current control of said converter so that a current value of said power storage device becomes a current command value, and said control device further comprising a current control unit that performs current control of said converter in accordance with an output of a current feedback control element including at least an integral element that integrates a deviation of the current value of said first power storage device from said current command value, and in that when switching said switch from ON to OFF, said voltage control unit takes over from said current control unit the output of the integral element in said current feedback control element, as an initial value of the integral element in said voltage feedback control element. a first power storage device; a second power storage device; a power line for transmitting electric power input and output to and from said load; a converter for executing bidirectional DC voltage conversion between said first power storage device and said power line; a switch connected between said second power storage device and said power line; and a control device that controls ON/OFF of said switch and said converter, when said switch is OFF, said control device performing voltage control of said converter so that a voltage value of said power line becomes a voltage command value, wherein a switching unit that switches ON and OFF of said switch in accordance with an operating state of said load; a voltage control unit that performs voltage control of said converter in accordance with an output of a voltage feedback control element including at least an integral element that integrates a deviation of the voltage value of said power line from said voltage command value; characterized by when said switch is ON, said control device performing current control of said converter so that a current value of said power storage device becomes a current command value, and said control device further comprising a current control unit that performs current control of said converter in accordance with an output of a current feedback control element including at least an integral element that integrates a deviation of the current value of said first power storage device from said current command value, and in that when switching said switch from ON to OFF, said voltage control unit takes over from said current control unit the output of the integral element in said current feedback control element, as an initial value of the integral element in said voltage feedback control element.