AN OPTIMUM MODULATION STRATEGY FOR A NOVEL NOTCH COMMUTATED 3-PHI PWMINVERTER

The recent introduction of soft switching features in medium power sta tic converters promises improved semiconductor utilization and higher switching frequencies. In this paper a dc-side commutated zero voltage switching (ZVS) PWM 3-PHI VSI topology is discussed. This topology co nsists of a typical six-switch bridge with the addition of a simple dc bus commutating subcircuit which can provide, on demand, the necessar y soft switching zero-volts interval across the inverter dc bus. The o bjective of this paper is to identify a specific PWM technique which, in combination with the proposed ZVS scheme, can provide optimum overa ll converter switching performance. Moreover, the combination of the i nverter topology and the modulation strategy proposed here yields a so ft switching environment at the lowest possible switching frequency. R eduction in switching losses is further enhanced by increasing the eff ective and reducing the actual switching frequency. Finally, this pape r includes a detailed analysis and design procedure for the proposed n otch commutated inverter topology. Simulation and experimental results are also presented to verify kev predicted results.