Modeling of Z-Source Network for Neutral Point Clamped Multilevel Inverter

Renewable energy sources such as wind, solar and fuel cell have a wide voltage change range due to the nature of the sources. Fuel cell stack voltage drops greatly with current and wind generator voltage varies with wind speed and control. Photovoltaic cell´s voltage varies with temperature and irradiation. The traditional voltage source inverter that has been the power conversion technology for these energy sources cannot cope with this wide voltage change nature and often requires additional voltage boost by additional DC-DC converter. The Z-source inverters can solve this problem. Multilevel Inverter (MLI) has been recognized as an attractive topology for high voltage DC-AC conversion. This paper presents design of Impedance (Z) Source network for Neutral Point Clamped (NPC) three level inverter. This inverter uses single impedance source network and less clamping diodes. The operating modes of Z-Source Inverter (ZSI) are Shoot through mode, Active and Open mode. The detailed design aspects in these modes are presented.