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A three-phase multilevel modular H-bridge converter structure can be used to drive high power AC motors and has several advantages, if compared with the other most used multilevel converter structures. Often known as a cascaded multilevel inverter, this simple but effective technical solution is being used by several manufacturers. However, even if a three-phase AC motor is driven, each H-bridge converter is single-phase and the DC-link capacitance must be very large to reduce the DC-link voltage ripple. This paper shows how to reduce such capacitance and/or voltage ripple by using a new devised PWM strategy, performing also nonconventional filtering actions on the DC-link. The main analysis has been based on the structure with simple C filter in the DC-link, but the developed method can be applied also to classical L-C DC-link filtering systems, thus permitting the avoidance of resonant conditions, extremely critical in these applications. All the analytical computations and the most significant analyses and results are reported.
Industrial Electronics, 2002. ISIE 2002. Proceedings of the 2002 IEEE International Symposium on (Volume:3 )
Date of Conference: 2002