Averaged-value Modeling and Modelability Analysis for an Operational Megawatt-scale Medium-Voltage Modular Multilevel Converter

This paper presents a new modeling method for deriving an averaged-value model (AVM) of an operational megawatt-scale medium-voltage modular multilevel converter (MMC) without knowledge of the internal topology or controls. The model control parameters are derived from the dc terminal impedance measurements and step transient responses. The model is validated first by controller-hardware-in-the-Ioop (CHIL) simulation and subsequently by power hardware testing. Thousands of repeated current step responses are automatically implemented in the test bed to generate sufficient data for model validation. These tests also revealed a specific phenomenon associated with current rise time inconsistency. Therefore, the modelability of power electronics converters is first explored in this paper, and a preliminary analysis is provided.