Continuous Discontinuous Pulse Width Modulation Index With Variable Power Factor

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Generalized Discontinuous PWM for Three-Level T-NPC Inverters Operating at Low
Modulation Index with Variable Power Factor
Subhadeep Bhattacharya, Student Member, IEEE, Diego Mascarella, Member, IEEE, Geza Joos, Fellow, IEEE, and Jianhong Xu, Member, IEEE
Abstract— Conventional three-level discontinuous pulse-width modulation (DPWM) techniques are typically employed in variable frequency drive applications to reduce inverter switching losses and provide maximum benefit for load power factor angles in the range from 30° lagging to 30° leading. This paper proposes a series of DPWM templates for lower power factors and a generalized DPWM strategy for three-level T-NPC inverters operating with modulation indices lower than 0.5. With a change in the power factor, the proposed strategy adapts the inverter pulse sequence by combining different portions of the proposed DPWM templates within one fundamental cycle and ensures minimum switching instances during transitions. Consequently, the strategy perfectly aligns the no-switching durations of the inverter pulse-patterns with the respective load-current peaks, achieving a 50% switching loss reduction for all operating power factor angles (90° lagging to 90° leading) at modulation indices lower than 0.5. The paper provides an analytical evaluation of the proposed strategy on the three-level T-NPC inverter switching losses. The simulation and experimental results demonstrate the effectiveness of the proposed three-level generalized

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