Smooth and nonsmooth bifurcations in multi-structure multi-operating-mode hybrid power systems

Hybrid renewable power generation systems have been developed rapidly in recent years. Due to the inherent fluctuation of availability of energy from renewable sources, systems that are designed to capture energy from such sources and deliver it in loads have to cope with the difficult challenges of maintaining stability under all possible operating conditions. As a result, the structures and operating modes of such hybrid systems are inherently time-varying. Due to their multiple structures and operating-modes, hybrid systems have rather complex dynamic behavior and the design for stable operation requires thorough consideration of the effects of variation in parameters on the operating modes and corresponding stability statuses. This paper presents a formal system description for such systems and a general procedure for analyzing the change of dynamical behavior under parameter variations (i.e. bifurcation) of this kind of systems. A hybrid power system consisting of dual-input buck converters is taken as an example for illustrating the possible complex behavior. We reveal smooth and nonsmooth bifurcation phenomena in this system. Under certain conditions, nonsmooth bifurcations have been observed and verified with full-circuit simulations. Moreover, a detailed analysis based on an averaged model is performed to identify two specific types of bifurcation and evaluate the stability boundaries of the system.