Common Mode Voltage Elimination in Variable Speed Drives for Improved Electrical Safety

• Published in: IEEE transactions on industry applications Vol. 56; no. 4; pp. 4365 - 4374
• Main Authors: Mirzaeva, Galina, Carter, Douglas, Uddin, S M Muslem, Stepien, Peter
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-07-2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: AC motor drives; ac motor protection; back to back converter; Circuits; common mode voltage (CMV); Earth faults; Electric potential; Electrical grounding; Electrical safety; Electromagnetic interference; electromagnetic interference (EMI); Fault currents; Harmonic distortion; Industrial applications; Inverters; mining industry; mining industry safety; modulation; Power transformer insulation; Support vector machines; Switches; Topology; Underground mining; Variable speed drives; Voltage
• ISSN: 0093-9994; 1939-9367
• DOI: 10.1109/TIA.2020.2992585

Common-mode-voltage (CMV) is a well-known source of bearing currents and electromagnetic interference (EMI) in industrial applications. In industrial environments with impedance-earthed IT earthing system, such as underground mining, CMV is additionally associated with potentially undetectable fault currents, due to their diversion away from a protection circuit. This article proposes a variable speed drive (VSD) solution that generates practically zero CMV and removes alternative paths for the fault currents. The VSD topology utilized in this article is a standard two-level inverter with active front end. The article develops a control strategy such that it eliminates CMV, minimizes EMI, and optimizes harmonic distortion at the drive input and output. Experiments conducted in physically emulated industrial environment have confirmed that CMV and EMI are practically eliminated, and the earth fault protection is effective.