The joining of Latvia to the energy market determines the need to change the power system management principles. The efforts to achieve as high an effectiveness level as possible lead to the creation of a corresponding software complex. To achieve this goal, it is necessary to solve many labour-intensive problems and tasks. On an ideal electricity market, all of its participants buy and sell electricity at a unified equilibrium price. The price formation is influenced by many factors and restrictions (technical, legal as well as environmental ones). The restrictions can be at least partially changed. If restrictions of various kinds are observed, including the wish to support the use of renewable energy resources, a unified equilibrium price for all the market participants cannot be determined in many cases. Compliance with the restrictions may require considerable means. Support in the form of increased electricity purchase prices leads to deviations of the regime management of renewable energy resources from the optimal operating regimes on the market that is free from supports and restrictions. Questions arise as to how substantiated the support prices and the restrictions are. Therefore, to understand the operation of the electricity market, additional attention has to be paid to the market restrictions and the price formation mechanism. In order to be able to judge about the influence of the restrictions, it is necessary to solve a complicated power system regimes optimisation task. The goal of the thesis is to contribute to economically efficient operation and development of the power system. To reach this goal, the thesis addresses the following main tasks: 1. Review of the development of electricity markets and the operation principles of the largest deregulated electricity markets. 2. Investigation of the electricity price determination principles at the conditions of a competitive market. 3. Synthesis of a stochastic algorithm of power plant regime and supply price optimisation. The objective function of the task has been transformed and the optimisation task has been decomposed, which made it possible to use a combination of linear and nonlinear programming, ensuring an acceptable calculation time. 4. Development of an algorithm for calculating electricity node prices in a steadystate regime, considering the inhomogeneity of the network and the reactive power flows; approbation of the algorithm by way of experimental calculations. 5. Substantiation of a method and algorithm for analysing the influence of the transmission limitations of the power system and the technical and legal restrictions of power plants on the regimes and the electricity prices. 6. Definition of the deficiencies of the adopted support schemes for renewable energy resources; ways to eliminate these are proposed. 7. A method and an algorithm have been proposed and tested for simplifying the solution of the price calculation tasks for non-linear nodes. The present doctoral thesis has been written in Latvian. It consists of an introduction, five chapters, conclusions, recommendations, and a bibliography. The thesis contains 82 figures, 18 tables, 162 pages all in all. The thesis has 5 annexes. The bibliography consists of 151 sources. Results of the thesis were reflected in 32 publications in international journals and were partially used in the synthesis of the operation control software.for Latvenergo power plants.