Analytical Voltage Optimization Method for DC Railway Networks with Wayside Energy Storage System

This study addresses a 1.8kV bilateral feeding system for DC railway applications, composed of multi-pulse diode rectifiers at both ends and a storage unit with a DC/DC converter located at an intermediate station. The storage system introduces an additional degree of freedom to control power flows by applying a specific voltage at a strategic point between the passive rectifiers. This paper formulates a voltage compensation problem aimed at reinforcing the network while minimizing conduction losses along the catenary. Due to the nonlinear nature of the power balance equations, a closed-form analytical solution is not directly obtained. To overcome this, the paper proposes an approximation method for the pantograph voltage to enable an analytical formulation of the optimization problem. A comparison between the proposed analytical approach and a numerical iterative optimization method is presented and discussed.