چكيده به لاتين
In this thesis, an asymmetric balancing transformer for traction substation system and a half-bridge power quality conditioner are used to compensate for the unbalance caused by the single-phase load of the electric railway on its feed grid. Asymmetric balancing transformer is capable of compensating part of current unbalance. But to maintain all power quality standards within the standard range, other compensating solutions must be used. One solution is to use railway power quality conditioners. These compensators consist of one or more power electronic converters that can be used with different configurations and different number of switches. Therefore, in this thesis, in order to reduce the number of these switches, the half-bridge configuration of these compensators is used. These compensators consist of two single-phase back-to-back converters connected by two dc link capacitors. These compensators are capable of simultaneously resolving power quality problems. But despite the positive features, these compensators face some challenges. One of the most important of these is the high VA-capacity of the compensator, which results in the use of high-rating power electronic switches in their structure. Therefore, to reduce the VA-capacity of these converters in the worst load situation (where one section is in nominal load and the other section has not any load) a partial compensating method is used in the generating unit of the compensating reference currents. Also, one of the challenges of applying railway power quality conditioners is the problem of using a suitable controller to quick tracking the reference currents of its converters. Most current controllers used in previous research have weaknesses such as variable switching frequency or slow dynamics. Therefore, in this thesis, in the control unit of the compensating reference currents and the production of switching pulses, a Dead-Beat current controller is used, in which the switching frequency is constant and injects fewer harmonics and also has fast dynamics. The simulation results, confirm the performance of the proposed structure, partial compensation method and current controller.
