Wide-band modeling of modular multilevel converters using extended-frequency dynamic phasors

This paper presents a model for a Modular Multilevel Converter (MMC) using extended-frequency dynamic phasors. The model is based upon a series of harmonic-frequency representations that are obtained for the fundamental and dominant harmonic components. Depending on the requirements of the study to be conducted and the desired level of model accuracy, a low-order model (i.e., average-value) or an arbitrarily wide-band model may be constructed. The paper describes the principles of modeling using extended-frequency dynamic phasors, and applies them to an MMC connected to a power system represented using a Thevenin equivalent. The model contains details of the MMC's control system including its high-level control circuitry, as well as voltage balancing and synchronization components. The developed model is then validated by comparing it against a fully-detailed electromagnetic transient (EMT) simulation model developed in PSCAD/EMTDC simulator. Comparisons are made to establish the accuracy of the model (both its low-order and wide-band variants) and to assess the computational advantages it offers compared to conventional EMT models. (C) 2016 Sharif University of Technology. All rights reserved.