Power Quality Analysis of HP Electric Drive based on 3L NPC AFE Rectifiers with SHE Modulation Method

Abstract

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.