SIMULATION AND ANALYSIS OF THE INFLUENCE OF THYRISTOR CONDUCTION TIME IN THREE-PHASE CONTROLLED RECTIFIERS ON HARMONIC DISTORTIONS IN THE POWER SUPPLY NETWORK

Background. Modern technologies related to power electronics and microprocessors create new challenges for ensuring high-quality electrical energy. The use of single-phase and three-phase rectifiers for supplying loads often leads to current waveform distortion, which negatively affects equipment performance and reduces the operational characteristics of energy systems. The main issue is harmonic distortion caused by load nonlinearity, which can degrade the quality of electrical energy and affect the performance of transformers and cable lines. Objective. The aim of the study is to analyze the changes in power quality indicators when the control angle of thyristors in a three-phase asymmetrical controlled bridge rectifier is modified. The study is conducted through analytical calculations and computer simulation. Methods. The research was carried out based on a simulation model of a three-phase asymmetric bridge rectifier. MATLAB® and Simulink® environments were used for simulating three cases: without a filter, with a filter but without considering the internal resistance of the transformer, and with a filter, taking into account the transformer's internal resistance. The simulation included an analysis of parameter changes at different thyristor control angles. Results. It was found that increasing the control angle leads to an increase in the harmonic distortion coefficient in the network, which may exceed the permissible limits defined by IEEE 519-2022 and DSTU EN 50160:2023 standards. The study also explored the impact of LC filters on power quality, particularly their negative effect in the form of a reduced power factor. Conclusions. The change in the thyristor control angle affects the quality of electrical energy by increasing harmonic distortion and reducing the power factor. The obtained results emphasize the need for careful selection of rectifier control parameters and harmonic filtering to ensure compliance with regulatory requirements. An important recommendation is to consider the internal resistances of transformers when designing such circuits, as they influence the level of current and voltage distortion in the electrical network.