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In this paper, a switching strategy for multiple-input converters (MICs) is presented and analyzed. MICs have been identified to provide a cost-effective approach for energy harvesting in hybrid systems, and for power distribution in micro- and nanogrids. The basic principle of the proposed switching strategy is that the effective duty ratio of each switch is an integer multiple of a common duty ratio (CDR), the CDR being the duty ratio of a common switching function that is generated at a higher frequency by frequency division. The proposed strategy enables switching functions for MICs that have a greater number of input legs to be generated with relative ease. Another benefit of this scheme is that it allows an MIC's output voltage to be regulated by employing the CDR as the only control variable, irrespective of the number of input legs present. Essentially, the strategy transforms an MIC into an equivalent single-input single-output system for analysis, which simplifies controller design and implementation. Without loss of generality, this technique is demonstrated by analyzing a multiple-input buck-boost converter. A PI controller is shown to regulate the MIC's operating point. The analysis is verified by simulations and experiments.
Date of Publication: Nov. 2012