Fabian Stamer, Firat Yüce, Matthias Singer, Marc Hiller

44rd Annual Conference of the IEEE Industrial Electronics Society (IECON)

With the increasing relevance of regenerative power generation and more power electronic converters connected to the grid, the requirements on grid current quality increase. Since a 3-level power converter has a higher quality output waveform compared to a 2-level converter, it is a popular power converter topology for wind power and photo voltaic systems. However, the 3-level power converter has a split dc-link. The main challenge is to balance the two capacitor voltages. In this paper different methods to solve the balancing problem of the neutral-point potential of three-level T-Type neutral-point-clamped (TNPC) voltage source converters (VSC) are investigated. The converter is
used as an active front end (AFE) converter, which is composed of single phase cells with distributed dc-link capacitors. Based on a simulation model of a TNPC, the different balancing methods are analyzed and compared. Furthermore, a new balancing strategy is proposed. In order to verify the investigated balancing methods, a three phase converter with newly designed intelligent single phase printed circuit board (PCB) cells has been developed, built and assembled.