Systematic Derivation of a Family of Output-Impedance Shaping Methods for Power Converters—A Case Study Using Fuel Cell-Battery-Powered Single-Phase Inverter System

For power converters used in renewable energy systems, output-impedance design has become an important design consideration for minimizing the impacts of low-frequency harmonic current on the lifetime of ripple-sensitive energy sources such as fuel cells and photovoltaic cells. In the literature, various methods are proposed to tackle this design issue but they are frequently treated in isolation from each other and specific to the systems being discussed. In this paper, a systematic derivation of four basic modes of output-impedance shaping method is presented. These basic modes can be directly inferred from the Mason's gain formula and other methods are in essence derivatives or combinations of these basic modes. By using a fuel-cell-battery-powered single-phase inverter as an implementation example, their characteristics are discussed thoroughly and their performances in shaping converter's output impedance are evaluated experimentally.