Graphoanalytic determination of symmetry parameters and total compensation of reactive power for a three-phase power supply system

Abstract

Problem. The simulation of currents and voltages in electric three-phase power supply systems is an important means of improving the quality of electrical supply. It is precisely the alignment of the values of currents in the phases of electricity supply lines, thus, the power supplies are loaded evenly. In addition to the symmetry to reduce losses in the transmission of electrical energy, it is necessary to provide transmission from the source to the loading of only active power. Therefore, it is necessary to determine the parameters of symmetric-compensating devices, which, given the fact that active-reactive line resistance is taken into account, is a rather complicated task. Numerical optimization algorithms are used to solve this problem, the disadvantage of which is the possibility of not receiving a solution due to unsuccessful selection of initial approximation of parameters and (or) excessive number of computational operations. To solve such problems, symmetro-compensating devices are used. The need to take into account the influence of active-reactive resistance of transmission lines with accurate calculation of the parameters of symmetro-compensating devices requires the use of computer models and numerical optimization methods and subroutines. Goal. Development of the method of determining the parameters of the symmetrical device for three-phase power supply systems, based on the analysis of the existing operating mode of the system with subsequent graph-analytical determination of the parameters of the symmetry and full compensation of reactive power. Methodology. The complex methods of analysis of linear electric circuits are used. To determine the requirements of symmetry and compensation, the method of symmetric components is used. To determine the parameters of the compensating device, methods of analytic geometry are used, as well as matrix methods for solving systems of linear algebraic equations. Results. The proposed method allows graphoanalytic way to obtain a numerical solution to the problem of symmetry of currents in the line and compensation of reactive power in a three-phase power supply system with asymmetric load. It has been established that the parameters of the symmetric device, determined from the data of the initial analysis of the mode of operation of the power supply system with an asymmetric load, do not always provide a sufficient effect of symmetry and compensation. To improve the efficiency of the symmetry and compensation parameters of the simulating device should be specified according to the primary compensation. Originality. It is proposed to make an initial assessment of the mode of operation of the power supply system. Based on the initial assessment, the primary requirements for the parameters of symmetry and compensation are determined. Approximate values of the parameters of the symmetry and compensation are determined by processing the initial requirements by methods of analytical geometry. The effect of primary symmetry and primary compensation was estimated, and the primary requirements were clarified. After the correction, the full effect of the symmetry of currents and the compensation of reactive power in the lines of the power supply system have been achieved. Practical value. The proposed method allows to calculate the parameters of the symmetric compensation devices with high accuracy taking into account the resistance of lines in power supply systems with a wide range of changes in asymmetry and reactivity of loads, which ensures reduction of losses due to excessive asymmetry and reactivity of consumers.

Key words: three-phase system; asymmetry; symmetrical device; reactive power compensation.