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This paper proposes a voltage support scheme for traction networks, which compensates for the voltage drop along the catenary line to which locomotives are connected. The proposed method is based on the injection of capacitive reactive power through the current controlled active line-side converter of locomotives. Comparing the catenary voltage with its reference value, the error is fed to a gain-scheduled PI-controller. The controller generates the q-axis reference value of the converter current, which is responsible for reactive power injection. The gain scheduling is carried out through identifying the parameters of the catenary line. The catenary parameters identification is performed by harmonic current injection and analyzing its impact on the catenary voltage. The performance of the proposed control strategy is evaluated in MATLAB/PLECS environment for a traction network consisting of one locomotive and two substations and moreover, for a two-locomotive three-substation traction network.