NOVELTY - The system (100) has an electrical storage apparatus (3) in which direct-current power supplied to direct current bus (1) is stored. A first interruption unit (7) is provided between first electrical storage apparatus and direct current bus, and is provided to cut away storage apparatus from bus. A second interruption unit (8) is provided between direct current (DC) load and direct current bus. A control equipment (6) outputs first interruption signal (SD1) when state of first electrical storage apparatus is monitored and abnormality of first electrical storage apparatus is detected.    USE - Direct current power supply system for power converter device e.g. power conditioner for delivering and receiving direct-current power between electrical storage apparatus e.g. secondary battery such as lithium ion battery, lead acid battery and nickel-hydrogen battery used in vehicle e.g. electric vehicle, and direct current bus through electrical storage apparatus connection unit and interruption unit.    ADVANTAGE - The direct current power supply system maintains the quality of co-operative energy when an electrical storage apparatus is cut away from a direct current bus. The power consumption of the direct current apparatus 5 is reduced rapidly if the direct current apparatus is switched from an ON state to an OFF state. The introductory cost of the electrical storage apparatus is reduced by using the electrical storage apparatus mounted in EV9. Since the electrical storage apparatus function as mutual backup, the fluctuation of the voltage of the direct current bus is suppressed reliably. The expansion of abnormality of the electrical storage apparatus is prevented. The loss of current during power conversion is prevented.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a power converter device; and    (2) a method for controlling direct current power supply system.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the direct current power supply system. (Drawing includes non-English language text)    Direct current bus (1)    Electrical storage apparatus (3)    Control equipment (6)    First interruption unit (7)    Second interruption unit (8)    Direct current power supply system (100)    First interruption signal (SD1)