Current Electromagnetic Compatibility Problems of High-Power Industrial Electric Drives with Active Front-End Rectifiers Connected to a 6–35 kV Power Grid: A Comprehensive Overview

Abstract

Today, electric drive systems based on frequency converters with active front-end rectifiers (FC-AFEs) are widespread across industries. In the course of the upgrade of production facilities, such systems replace the conventional converters with thyristor- and diode-based rectifiers. FC-AFEs have the following advantages: the capacity to regenerate the power to the grid and the capacity to operate at the set power factor. The manufacturers of FC-AFEs also claim that their products have the best electromagnetic compatibility (EMC) with the power grid. The best EMC shall be achieved via a multilevel FC-AFE topology and specialized pulse-width modulation (PWM) algorithms for AFE rectifiers. However, the experience of operating mid-voltage high-power electric drives with an FC-AFE in 6–35 kV factory distribution grids with non-linear frequency response due to resonant phenomena refutes the claims of the FC-AFE manufacturers. Resonant phenomena in 6–35 kV grids are caused by the interaction of the inductance of grid components (transformers, reactors) and the capacitance of output cable lines. If the resonance frequency at a sufficient amplitude corresponds to the harmonic frequency of the current consumed by the FC-AFE, the distribution grid will feature high-frequency voltage distortions. This may lead to failures in voltage quality-sensitive electrical consumers. This problem recurred at various metallurgical companies. The purpose of this research is to make a comprehensive overview of the EMC problems during the operation of FC-AFEs at active production facilities, as well as the analysis of the technical solutions aimed at the improvement of the EMC of high-power FC-AFEs with the power grid.

Power Factor Modelling and Prediction at the Hot Rolling Mills’ Power Supply Using Machine Learning Algorithms

“…This emphasizes greater errors over MAE. RMSE is the square root of MSE, which provides a more interpretable measure of error, being displayed in Equation (14).…”

“…These high power consumers use a lot of electricity and can have an impact on power quality via reactive power, low power factor, and electric current harmonics [6][7][8]. The largest consumers of electric power in steel plants are EAF [5,9,10], but rolling mills also have significant power and produce harmonic currents [11,12], overcurrents that cause reactive power and low power factor [13,14] or flicker [12].…”

Control over Grid Reactive Power by Using a Powerful Regenerative Controlled-Speed Synchronous Motor Drive

“…At different m values, the converted power quality parameters change. The relevant studies in the area have shown that the higher the m value, the lower the THD of the converter output voltage [19][20][21][22][23]. In practice, the m value close to 1 (if we describe a range from 0 to 4/π) is chosen while providing a margin for maintaining stable AFE and VSI operation in dynamic modes (a voltage drop in the DC link during shock application of the electric drive load) [24][25][26][27].…”

Study of Behavior of Voltage and Current Spectra of Three-Level Neutral Point Clamped Converter at Selected Harmonic Elimination Programmed Pulse Pattern Pulse-Width Modulation

“…Some studies [29,30] consider searching for SHE PPWMs to bypass the resonance region of the grid impedance frequency response to improve the voltage quality at the connection point of industrial consumers to a common grid. However, the papers describe only experimental methods to estimate the impact of converters without preliminary calculation of the spectra of current induced by supply voltage distortions under the conditions of existing power grid modes.…”