PURPOSE: To prevent generation of resonance phenomena of a power converter through addition of the minimum hardware at the time of a sudden change of load and trolley voltage by connecting a parallel resistor for selectively shunting a frequency component at the time of generation of said resonance phenomena in parallel with a DC reactor.

CONSTITUTION: A trolley voltage is supplied from a pantograph 1 to an inverter circuit 5 via a limiting resistor 2 and a DC filter reactor 3. Also, a DC filter capacitor 4 is connected in parallel with the DC input end of said inverter circuit 5. Further, a load 7 such as air conditioner is connected in parallel with the three-phase AC output of said inverter circuit 5, and a resistor 6 is connected in parallel with said reactor 3. In this manner, most of a steady-state input current not related to resonance passes through said reactor, and a voltage expressed by Lid/dt is generated at both ends of the reactor relative to a resonance current component and a current by said voltage contributes to damping so that the gain in the vicinity of resonance frequency lowers sharply.