This master thesis deals with different topolgies for three phase power factor improvement based on three phase bridge rectifier. The introductory part of the master thesis provides theoretical considerations that include a detailed definition of power factor and the effect of harmonic distortion on the quality of the electrical network. The electrical network quality was tested on the currently active agency standards that fall under EN 61000–3–2 and IEEE STD 519 norms. The focus of the paper is to examine topologies for improving power factors. Topologies are divided into passive, hybrid and active. All of the systems are simulated using PLECS program software. After introductory considerations, passive topologies for improving the power factor are investigated. Passive algorithms implies the use of passive components. Analysis of obtained results shows that the passive topologies are insufficient to meet the legal norms. Hybrid topologies use a transistor to achieve control of the output voltage level, and partially control the input current. One, two, and three transistor hybrid topologies are developed, comparing the amplitude of the harmonic components with the EN 61000–3–2 and IEEE STD 519 legal norms. The simulation showed that the topology using three transitors is closest meeting the legal norms, while the topologies with one and two transistors largely deviate from the defined legal norms. Finally, an active system has been developed by the means of six transistors that allows the sinusoidal input current and the controlled output voltage level. The six-transistor system exhibited a 4% harmonic distortion factor with a power factor above 99%. Three phase power factor improvement, total harmonic