چكيده به لاتين
AC systems are widely used to feed interurban railways. AC railways are a type of high-power electric loads fed by three phase power source grids. These loads are of high importance and their electrical energy must not be cut off. Electric trains are one of the worst kinds of electrical loads and have several power quality problems that have an undesirable effect on power systems. One of the most important characteristics of AC traction load is the fact that it is single-phase, which results in the injection of negative sequence current into the grid. Other major problems include the harmonic currents and reactive power. To compensate them, it is necessary to use different devices and equipment at traction substations. On the other, problems related to overhead catanery systems in traditional traction power supply systems, that make trains slow, are the mechanical limitations. In this thesis, firstly, the characteristics and problems of traction loads are addressed. In the following, various compensation methods used to solve the problems of electric railway power quality in the past years, as well as the co-phase power supply system and the reason for its use in the electric railway network are explained. Then, the investigation of the co-phase traction power supply system with series hybrid converter (SHC) and shunt active converter (SAC) in MATLAB / SIMULINK software and its simulation will be examined and its performance in two types of load with high power factor and low power factor is investigated. Also, in order to improve its performance in compensating the negative sequence current, a combination of it with static var compensator is presented. Finally, the advantages and disadvantages of this approach will be fully explained in comparison with the conventional co-phase traction power supply system with RPC compensator.
Keywords: Traditional traction power supply systems, Co-phase traction power supply system, SHC and SAC, Power quality, Negative sequence current, Reactive power, Harmonics
