The applicability of active filters for reduction of voltage non-sinusoidality in the power supply system of a coal mine in Vietnam

The study is aimed at the provision of an underlying rationale for the use of active filters to reduce voltage non-sinusoidality in the power supply system of a coal mine in Vietnam. Power supply systems of coal mines and quarries are characterised by many voltage levels and various types of loads, with new electrical equipment working in parallel with outdated equipment. Coal mines and quarries are maintained under high power loads, with non-linear current-voltage characteristics introducing distortion into the electrical network. Therefore, power supply systems for industrial coal mining areas are determined by a quality of electric energy that is inconsistent with Vietnamese regulatory requirements. Additional economic damage is caused by low quality of electric energy. In order to improve the quality of electric energy, it is necessary to apply special technical means, such as active harmonic filters. The quality assessment of electric energy in the coal mine power supply system was carried out using the PQ-Box150 instrument for measuring electric energy quality indicators and mode parameters. An analysis of the measured quality indicators of electric energy is conducted, including the parameters of non-sinusoidal mode. For indicators characterising the distortion degree of the voltage curve shape, the results of the analysis indicate them to exceed the limit established in the regulatory documents of Vietnam. From the analysis of measured parameters in non-sinusoidal mode, the presence of a wide range of voltage and current interharmonics is also detected. According to the analysis of the reactive power mode at the fundamental frequency, the load power factor in one of the phases is established to be less than the minimum value given in the Vietnamese regulatory documents. In accordance with the measurement results of electric energy quality indicators and parameters of the non-sinusoidal mode of the load power factor and reactive power of the fundamental frequency, as well as characteristics of active harmonic filters, the application of an active harmonic filter was demonstrated to be appropriate for reducing voltage non-sinusoidality and increasing the load power factor in the power supply system of a coal mine.

quality of electrical energy, non-sinusoidal mode, harmonics, interharmonics, measurements, power supply system