Maintaining a balance between consumption and generation of reactive energy has been the topic of numerous scientific papers since the beginning of the commercial use of AC Power Systems. The challenge is to find the right balance between the minimum reactive power flow to maximize the capacity of the power system transmitting operating energy, and sufficient quantity of reactive power to maintain the desired voltage profile. The introductory parts of this doctoral thesis provide the foundations of reactive energy theory and power factor. The ways and methods of compensation of reactive energy have not changed significantly since the introduction of the first parallel capacitor batteries for use in power systems. Although this compensation method is economically acceptable and relatively reliable, it does not quite meet the needs of modern electrical systems. Most systems today are compensated by the sources that do not provide a flexible amount of reactive power. The constant quantities of reactive power rarely act in an adequate way in terms of compensation, i.e. minimizing the flow of energy. In recent years, new technologies that address some of the shortcomings of reactive power compensation based on capacitor batteries, have emerged. Such systems could also be used to produce reactive energy with fewer undesired transients and independent of voltage. New compensation capabilities have developed with the arrival of controlled switches and new, increased capabilities of semiconductor power electronics components, [2]. Some of the new reactive power compensation technologies are static synchronous generator (SSG), static var compensator (SVC), thyristor controlled chokes and capacitors (TCR, TSR, TSC), static var system (SVS), active filters (AF) and the unique power quality device (UPQC), [3]. Thus, Chapter 7 provides a simulation of the operation of a nonlinear consumer with an active power filter in the MATLAB SIMULINK software package. Furthermore, an analysis of the results of the dynamic reactive power compensation simulation is presented. A complete analysis of consumption according to the billing data for consumed electricity was also carried out. It was followed by determining the most suitable location and size of the compensation devices in terms of reducing losses and improving voltage conditions. For this purpose, a modified genetic algorithm with particle swarm optimization has been proposed for the purpose of finding the most appropriate location for the installation of dynamic compensation devices. The algorithm that was developed accordingly, was used to create a graphical interface of a program for calculating the power flows of an asymmetric load, spatially and temporally distributed in the electrical traction subsystem, which in addition provides an estimate of the optimal location for the placement of dynamic compensation devices. This was followed by the economic analysis using current net values of project implementation and installation over its lifetime. A complete analysis of the measurement results on the actually realized dynamic compensation device, as well as of the simulation models and the developed graphical interface was also performed. A definite benefit was stated, both technically and economically from the installation of dynamic compensation devices in electric traction networks. Furthermore, a developed computer program with a graphical interface can greatly reduce the problem of finding the optimal installation location, especially in networks with many nodes. Finally, the conclusion confirming the significant economic savings in the fees for the over taken electricity, following the installation of the dynamic reactive power compensation device, was provided.