Operational characteristics of a filtering rectifier transformer for industrial power systems

Abstract

Many conventional methods focus on reducing the harmful impact of the poor power quality in industrial rectifier systems, but they focus more on the harmonic problems of the utility grid than they do on that of the rectifier transformer; hence, the rectifier transformer would still be adversely affected by harmonic pollution. In order to solve the problem, a filtering rectifier transformer is proposed that adopts a harmonic current drainage system that incorporates tertiary winding and tuned harmonic filters. The impedance of the tertiary winding is specially designed and the tuned harmonic filters work together to restrain the harmonic current and give a good performance in the reactive power compensation close to the harmonic source. By deducing the current relationships between the windings of the filtering rectifier transformer, the principles of the harmonic suppression and reactive compensation are elaborated. The theoretical analysis shows that if the harmonic current drainage system is out of service, the characteristics of the operation parameters of the filtering rectifier transformer are the same as those of the conventional one. While it is in service, the filtering rectifier transformer could improve the total harmonic distortion of the grid side current, decrease the grid side current, reduce the grid side power, and enhance the grid side power factor. A prototype filtering rectifier transformer was built and installed in an aluminum smelting plant. Both the simulation and the field measurement results verify the correctness of the theoretical analysis. The mathematical relationships deduced in the paper will contribute to further study of the filtering rectifier transformer on the vibration and temperature rise suppression of the windings. The project has demonstrated that the proposed filtering rectifier transformer has promising prospects in various industrial power applications.