Soft-switching three-phase PWM inverter architecture utilizing coupling switches between input and output stage

Power converters for renewable energy systems are expected to have a high lifetime, low costs and a very high efficiency over a wide input power and voltage range (e.g. for photovoltaic and fuel cells). Although very high efficiencies can be achieved with hard-switched power converters operating with state of the art semiconductors, hard-switching results in several disadvantages such as conducted emissions. In addition, the switching frequency is limited to maintain a high efficiency, although a low switching frequency results in a higher required energy storage. In this paper, a three-phase PWM inverter architecture for photovoltaic or fuel cell inverter is presented, which has a wide input voltage range and achieves zero voltage switching (ZVS) for all inverter switches at all operation points. This has been obtained by introducing coupling switches between input and output stage, which also reduce conduction losses. It is shown that, auxiliary passive components are not required.