Tuning of control loops for grid-connected Modular Multilevel Converters under a simplified port representation for large system studies

Abstract

One of the present barriers to the widespread use of Modular Multilevel Converters (MMC) is the complexity of its control with respect to its predecessors. This paper presents a simple procedure to tune the current and energy control loops of the MMC, based on standard PI controllers and resembles control tuning approaches commonly used for 2-Level Voltage Source Converters (2L-VSC). The control design is based on a recently proposed simplified model of the MMC which is able to accurately represent the interface variables dynamics on the ac- and dc-side, which are considered as the main variables of concern from a macroscopic point of view. Furthermore, the tuning methodology guarantees the stable behaviour and correct tracking of the states. The paper presents simulation results of a typical case under the proposed tuning procedure.