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This paper presents power quality analysis of high power (HP) electric drive based on three level neutral point clamped active front end (3L NPC AFE) rectifiers with selective harmonic elimination (SHE) modulation method. As an object of the study has been chosen a power circuit of main electric drive of rolling stand plate mill 5000 JSC "MMK". The main drive is a system in which each 12 MW motor is connected to the grid via 18-pulse connection circuit based on three 3L NPC AFE rectifiers and transformers connected in parallel. The rectifiers operate on the basis of SHE modulation method with elimination: 5, 7, 11 and 13; 5, 7, 17 and 19; 17, 19, 35 and 37 harmonics. The research results has been obtained on the primary and secondary side of the transformers by mathematical modeling and calculated voltage and current harmonic spectrums and total harmonic distortion (THD) at consumption of the rated current. A mathematical model was developed in Matlab/Simulink program. It was determined that SHE modulation method with elimination of 5, 7, 17 and 19 harmonics is the most appropriate for the considered object. [ABSTRACT FROM AUTHOR]

The research of electromagnetic parameters of single-layer three-phase and six-phase chain windings was accomplished. It was determined that the instantaneous space distributions of rotating magnetomotive force in the three- phase chain winding are asymmetrical in respect of coordinate axes and symmetrical in respect of the origin of these axes. Instantaneous space distributions of rotating magnetomotive force generated by six-phase chain winding, contrary to the three-phase windings, are symmetrical in respect of coordinate axes. After accomplishing harmonic analysis of spatial rotating magnetomotive forces, it was obtained, that odd and even harmonics exist in the harmonic magnetomotive force spectrum generated by three-phase winding, and only odd harmonics in the spectrum generated by six-phase winding. The electromagnetic efficiency factors were calculated for both types of windings, and it was determined that for six-phase winding this factor is 23,7 % higher compared to three-phase winding. Furthermore, it was estimated, that the conditional amplitude of fundamental magnetomotive force harmonic in the analyzed six-phase winding is 2,13 times larger compared to the same amplitude value in the analogous three-phase winding. [ABSTRACT FROM AUTHOR]