Análise da propagação de harmônicas de alta frequência em circuitos secundários de distribuição de energia elétrica

Abstract

Understanding how the power grid has been changing in recent years is essential to predict problems and avoid damage to equipment, both at the utility and consumers. In this context, this dissertation investigates a recent topic in the electricity sector, which involves the appearance of harmonics in the range of 2 to 150 kHz emitted by equipment such as photovoltaic panel inverters, electric vehicle chargers and other equipment controlled by power electronics present in low voltage secondary circuits. High frequency emissions, also known as supra harmonics, can affect the power quality of distribution systems. Research shows that supra harmonics can cause interference in communication devices and equipment connected to the grid. The investigation and analysis of how high frequency currents propagate in distribution secondary circuits is important for diagnosing and mitigating any disturbances that may be caused by them. The focus of this dissertation is to analyze how the supra harmonic current injections are reflected in the voltage and how they propagate in different points of a secondary distribution system. For this, simulations were performed using MATLAB Simulink® software, where a secondary distribution circuit was modeled including its lines in PI model and sources emitting supra harmonic currents. The analyses were made by allocating these sources in different bars of the system. The results showed that voltage harmonic distortion levels depend on the frequency and grid impedance. The results also explored the potential scenarios of this type of grid, showing the consideration of six distributed generation systems connected to the network and injecting supra harmonic currents of different frequencies. In summary, the values of the voltage distortion rate were small and did not exceed 0.6%. It was found that the supra-harmonic emissions caused by the high frequency currents do not propagate through the network due to the low impedance path of the intrinsic capacitances of the electrical conductors and through the capacitive element contained in the structures of the electromagnetic compatibility (EMC) filters present in the equipment emitting the high frequency currents.