OPF for an HVDC feeder solution for railway power supply systems

Abstract

With increasing railway traffic, the demand for electrical power increases. However, railway power systems are often weak causing high transmission losses and large voltage drops. One possible method for strengthening the railway power supply system is to implement a High Voltage Direct Current (HVDC) feeder in parallel to the Overhead Contact Line (OCL). The HVDC feeder is connected to the OCL by converters. This paper describes different properties and characteristics of such an HVDC feeder solution. An AC/DC unified Optimal Power Flow (OPF) model and unit commitment is used to obtain proper control of the converters. The non-linear load flow and converter loss equations, and the binary variables for the unit commitment, lead to an optimization problem of Mixed Integer Non- Linear Programming (MINLP) type. The optimization problem is formulated in the software GAMS, and is solved by the solver BONMIN. In each case, the objective has been to minimize the total active power losses. © 2014 WIT Press.