An electric power conversion system comprising: first electric power converting means for converting first direct current power obtained from a DC contact line into alternating current power; an alternating current load which is connected to an alternating current side of the first electric power converting means; second electric power converting means for converting the first direct current power into second direct current power whose voltage level differs from a voltage level of the first direct current power; a first capacitor which is connected in common at a side where the first electric power converting means and the second electric power converting means receive the first direct current power; electric storage means for storing the second direct current power converted by the second electric power converting means; a first reactor which is provided between the second electric power converting means and the electric storage means; and being characterised by further comprising: a second capacitor which is connected in parallel to the electric storage means, wherein the first electric power converting means, the second electric power converting means and the first capacitor are collectively and integrally configured within the same unit so as to reduce wiring inductance between the first electric power converting means and the second electric power converting means, wherein a breaker is provided between the first reactor and the electric storage means, and a series circuit of the electric storage means and the breaker is connected in parallel to the second capacitor, a first resistor is connected in parallel to the second capacitor, and the electric power conversion system is adapted to perform an electric discharge of the first capacitor by opening the breaker turning on a switching element at an upper arm side in the second electric power converting means, and using a path which passes through the second power converting means and the first resistor as a discharge circuit for the first capacitor. first electric power converting means for converting first direct current power obtained from a DC contact line into alternating current power; an alternating current load which is connected to an alternating current side of the first electric power converting means; second electric power converting means for converting the first direct current power into second direct current power whose voltage level differs from a voltage level of the first direct current power; a first capacitor which is connected in common at a side where the first electric power converting means and the second electric power converting means receive the first direct current power; electric storage means for storing the second direct current power converted by the second electric power converting means; a first reactor which is provided between the second electric power converting means and the electric storage means; and being characterised by further comprising: a second capacitor which is connected in parallel to the electric storage means, wherein the first electric power converting means, the second electric power converting means and the first capacitor are collectively and integrally configured within the same unit so as to reduce wiring inductance between the first electric power converting means and the second electric power converting means, wherein a breaker is provided between the first reactor and the electric storage means, and a series circuit of the electric storage means and the breaker is connected in parallel to the second capacitor, a first resistor is connected in parallel to the second capacitor, and the electric power conversion system is adapted to perform an electric discharge of the first capacitor by opening the breaker turning on a switching element at an upper arm side in the second electric power converting means, and using a path which passes through the second power converting means and the first resistor as a discharge circuit for the first capacitor.