Neutral-point current modeling and control for neutral-point clamped three-level converter drive with small DC-link capacitor
Document typeConference report
PublisherIEEE Press. Institute of Electrical and Electronics Engineers
Rights accessRestricted access - publisher's policy
A Neutral-Point-Clamped (NPC) three-level inverter with small DC-link capacitors is presented in this paper. This inverter requires zero average neutral-point current for stable neutral-point potential. A simple carrier based modulation strategy is proposed for achieving zero average neutral-point current. A new simplified model of the neutral-point voltage dynamics is derived for the proposed modulation strategy. This model shows that the neutral-point current is proportional to the power drawn from the converter and it enables the use of well established classical control theory for neutral-point voltage controller design. A PI controller is used for neutral-point voltage balance. The implementation of the proposed modulation strategy and controller is simple. It does not require any information about the output phase currents. The controller is implemented in a 7.5 kW induction machine based drive with only 14 μF DC-link capacitors. A fast and stable performance of the neutral-point voltage controller is achieved and verified by experiments.
CitationMaheshwari, R.; Munk-Nielsen, S.; Busquets-Monge, S. Neutral-point current modeling and control for neutral-point clamped three-level converter drive with small DC-link capacitor. A: IEEE Energy Conversion Congress and Exposition. "3rd Annual IEEE Energy Conversion Congress & Exposition". Phoenix, AR: IEEE Press. Institute of Electrical and Electronics Engineers, 2011, p. 2087-2094.