Rigbers, K: Highly Efficient Inverter Architectures for Thre

Today, small scale photovoltaic generators are mainly connected to the grid via highly efficient single-phase inverters. The disadvantage of single-phase grid connection is the pulsation of the energy ?ow at twice the grid frequency. This requires a high DC-link capacitance, which is normally realized with electrolytic capacitors due to their high energy storage density. To achieve a long lifetime, a signi?cant, cost intensive oversizing of this type of capacitor is required. This high capacitance is not required for three-phase grid connection since here a constant power ?ow can be realized. The main disadvantages of conventional three-phase architectures are the requirement to boost the input voltage to achieve the required ratio between maximum and minimum input voltage at low losses and their increased complexity compared to the commercial single-phase inverters. In this thesis, two new concepts for highly efficient and low cost three-phase grid connection of photovoltaic generators are investigated. The proposed concepts have been compared to conventional hard- and soft-switched architectures for a 4 kW photovoltaic inverter for single-family homes. This comparison has been performed using an automatic optimization process including inductor design and switch selection employing a component database. The architectures have been optimized to have minimum losses for a given total inductor weight. The comparison shows that both concepts are promising solutions for photovoltaic inverters with high power density. The proposed Hecosi architecture can also operate at non-unity power factor and might also be advantageous for wind, fuel-cell and electric vehicle applications, where a low cost, highly efficient DC-to-AC conversion and a wide input voltage range is desired.