Iterative techniques for the solution of complex DC-rail-traction systems including regenerative braking

The solution of simultaneous algebraic equations describing a DC-traction power system is based on an iterative technique because of their nonlinearity. Two iterative methods specified for DC-load-flow problems are described and their mathematical and geometrical explanations are presented. The methods have been tested for DC-fed traction power systems and comparisons made of the computational time and iteration count. The DC-traction software which has been developed enables the situation with trains operating in regenerative-braking mode to be simulated. A condition in which convergence problems are to be expected occurs when there is a surplus of power produced during regenerative braking. In this case two different modelling approaches to represent regenerative trains in the simulation are investigated. A representative DC-fed-traction power system with train regenerative braking was simulated and the preferred method is selected by analysing the simulation results obtained and the computation times expended