Technological assessment of DC-DC multiple-input converters as an interface for renewable energy applications

This paper explores important characteristics of multiple-input converters (MIC) serving as a power electronic interface for renewable energy applications. Advantages of MICs are explained through an example with a photovoltaic (PV) system. Feasible MIC topologies for renewable energy applications are discussed and classified into four different MIC families. According to their different configurations, each MIC family is suggested for certain renewable energy applications. Furthermore, possible operating issues of MICs, such as relatively low efficiency, are also discussed. Design considerations for extending MIC´s voltage step-up ratio and achieving maximum power point tracking on all PV sources through are commented. Issues in modeling and control are also discussed, showing that it is important when evaluating closed-loop stability to consider nonlinear and time-varying characteristics of both renewable energy sources and the MIC. Design and synthesis of a multivariable controller that achieves quadratically stabilization and satisfies the H_∞ and pole-placement constraints for MICs is reviewed, too.