A New H8 Inverter Topology With Low Common Mode Voltage and Phase Current THD for 3-φ Induction Motor Drive Applications

Common mode voltage (CMV) reduction in a traditional H6 (six switch) 3-φ inverter usually demands additional power semiconductors to avoid poor harmonic performance. However, apart from tending to the CMV related issues, these extra switches do not add any other capability to the inverter. To address this limitation, in this article, a novel H8 inverter configuration is proposed which not only reduces the CMV by 66.6%, the phase current total harmonic distortion (THD) is also improved. The proposed H8 inverter employs two additional power semiconductor devices along with the conventional H6 inverter in a manner that it can generate 15 space vectors (SV). By considering the CMV attribute of each SV, a unique sector configuration is proposed where the SV diagram is divided into 18 asymmetrical sectors and three distinct SV sequences are identified. A special pulsewidth modulation scheme is devised to operate the proposed topology to achieve reduced CMV and improved harmonic performance. A comparison study reveals that the proposed topology offers better phase current THD, low CMV, low losses, and low semiconductor requirement. Simulation and experimental results are included to justify the various claims.