Decentralized Impedance Specifications for Grid-Connected Converters in AC Grids

To analyze the small-signal stability of systems with numerous Power Electronics Converters (PECs) connected to the same grid, the impedance-based method is widely applied. Due to the complexity of the grid, the possibility to provide independent impedance specifications to each PEC, referred to as decentralized specifications, has many advantages, especially when PECs are originating from multiple vendors. Decentralized specifications provide the possibility of individually designing the PEC connected to the grid while maintaining the system’s small-signal stability. This paper firstly summarizes the already established decentralized specifications for DC distribution grids where the small-signal impedances are modeled as SISO transfer functions. Secondly, it outlines the problems of extending the specifications for AC grids, where impedances are usually modeled as MIMO transfer functions. Finally, this article proposes the solution for providing such specifications based on estimating the position of eigenvalues with the Gershgorin theorem.