Hybrid as well as electric propulsion are more environmentally friendly solutions compared to conventional propulsion, and given the limited oil reserves, they are becoming more popular. Therefore, the hybrid propulsion is considered in this paper, more specifically the components of power electronics for a hybrid forest tractor with emphasis on the integration of high voltage and low voltage power system. The paper gives an overview of power electronics for hybrid vehicles and presents a selection of all components required for hybridization of the considered vehicle. A cost analysis was conducted to determine the profitability of such an investment. Furthermore, as a solution for the integration of high-voltage and low-voltage power systems, the parallel operation of several buck DC converters is presented. A hierarchical control system of converter operation is also proposed, which includes primary, secondary and tertiary regulation. The operation of such a system was examined through the simulation and experimentally. The paper is conceived in several chapters. The introduction briefly describes the issues of work. The second chapter provides an overview of the characteristics of a forest tractor. The third chapter provides an overview of the power electronics used for hybrid vehicles and the components selected for the considered tractor. The fourth chapter deals with cost analysis, and the fifth with a solution for the integration of high-voltage and low-voltage energy systems. Chapter six describes the computer model of the converter. The seventh chapter presents a solution for regulating the parallel operation of the inverter, and the eighth chapter contains experimental results. At the end, a review of the thesis is given.