The monograph is dedicated to the creation of scientific foundations for the selection of optimal parameters and operating modes of the reactive power compensation system on AC electric locomotives. The factors that have the greatest impact on the quality of the traction power supply on the side of the alternating current electric rolling stock are analyzed. It is shown that the nature of operation of electric rolling stock leads to non-determinism and non- ergodicity of the voltage change process in the catenary. Mathematical and software-oriented models of operation of an AC traction electric locomotive have been created, the distinctive features of which are the possibility of taking into account the modes of operation of the electric locomotive. A control system for the active part of the hybrid reactive power compensator has been developed, which is based on an algorithm for determining the spectral components of the traction current based on the Levinson-Darbin linear prediction method. This makes it possible to take into account the random nature of the voltage change on the current receivers of the electric locomotive and to adapt the work of the compensator to the voltage parameters of the catenary network.