The Simultaneous Use of Two Alternative Neutral Point Current Paths in a 3-Level ANPC Topology – Benefits and Challenges in High Power Applications

Abstract:
The use of 3-level topologies has been state of the art for years and is increasingly being used in the field of renewable energies, such as in wind, solar and energy storage applications. Mainly for high DC-link and output voltages (Vdc ≥1500V, Vac = 800...1140V) as well as power in the range of several 100kW to megawatts, each phase of the 3- level topology is constructed from three standard half-bridge modules, resulting in an Active Neutral Point Clamp (ANPC) inverter. In this paper, an introductory chapter analyses for which operating points and which applications the simultaneous use of the two alternative neutral current paths can be advantageous. Subsequently, two corresponding and known control strategies are presented, which are evaluated on the basis of an exemplary converter design for various standard half-bridge modules. Based on a simulation, one of these two control strategies is compared with a standard one for three different operating points.