Development and study of improved PWM algorithms of active rectifiers to achieve power quality in intra-factory electrical networks 6–35 kV

Currently, application of frequency converters with active front end rectifiers (FC-AFE) has become a standard solution for powerful adjustable AC drives with frequent dynamic modes. The advantages of these converters include the possibility of recuperation of braking energy to the supply network, as well as the best electromagnetic compatibility of electromagnetic capability (EMC) with the supply network as stated by the manufacturers of converter technology. This statement is only partly true, since FC-AFE manufacturers do not consider possible resonant phenomena in the 6–35 kV intra-factory distribution network caused by the interaction of reactive elements of the power supply system. When significant harmonics of the FC-AFE current are superimposed on the resonant region, dangerous voltage distortions of 6–35 kV may occur. Traditional methods of providing electromagnetic capability of FC-AFE in this case may not have the desired effect. Therefore, it is relevant to develop alternative technical solutions to ensure an acceptable level of electromagnetic capability of FC-AFE. One such solution is the use of advanced PWM algorithms in the FC-AFE adapting to resonant phenomena in the 6–35 kV intra-factory network. The materials for the study are the oscillograms of the currents and voltages at the input of the FC-AFE obtained experimentally and using mathematical modeling. Experimental data have been obtained on operating equipment with FC-AFE and on a special laboratory setup. When developing improved PWM algorithm of AFE, a well-known mathematical apparatus is used. It describes the dependence of individual harmonics on the number of switching and switching angles. The results obtained show the effectiveness of improved PWM algorithms in terms of reducing the effect of FC-AFE on the supply network and improving the quality of electricity in intra-factory networks of 6–35 kV. The results of the study are implemented at a number of metallurgical enterprises, thanks to which it is possible to reduce voltage distortions of 6–35 kV and increase the stability of the operation of sensitive electrical receivers. The developed improved PWM algorithm of FC-AFE can significantly improve the quality of electricity in the in-house electrical networks of 6–35 kV without additional capital costs and installation of additional equipment. Based on the results obtained, it is recommended to use the developed PWM algorithms on the operating equipment with FC-AFE of industrial enterprises.