Smooth and Non-smooth Bifurcations in Multi-structure Multi-operating-mode Systems: Case Study of a Power Conversion System with Two Energy Sources

Renewable power generation systems are gaining popularity and have developed quickly in recent years. However, due to the intermittent features of the renewable energy sources, conversion systems involving more than one energy sources are usually designed with multiple structures and multiple operating modes. The dynamic behavior is thus quite complex, and the design for stable operation of such systems requires consideration of the stability conditions for all possible structures and operation modes. This paper describes such conversion systems, and uses a standalone photovoltaic-battery hybrid power system as an example for illustrating the possible complex behavior. We reveal smooth and non-smooth bifurcation phenomena in this system. Under certain conditions, when the system switches its operation mode, a non-smooth bifurcation has been observed and verified with full-circuit simulations. Moreover, a detailed analysis based on an averaged model is performed to identify the two types of bifurcation.