Accurate Capacitor Voltage Ripple Estimation and Current Control Considerations for Grid-Connected Modular Multilevel Converters
Year: 2013
Type: article
Abstract: In this paper, the analytical solution for the submodule voltage ripple equations of a modular multilevel converter (MMC) is derived, based on the knowledge of the external voltage/current magnitudes, and enhancing a concept previously presented in the literature. In order to achieve high accuracy, all passive elements of the converter, common-mode voltage injection as well as intentionally imposed circulating current harmonics are taken into consideration. The natural charge level mechanism of the capacitor voltages is also explained. As application examples, the three- as well as the two-phase grid-connected MMC cases are chosen. The control of line and circulating currents is also discussed and two respective independent feedback loops are formed. The concept of fictive-axis emulation is tailored for the two-phase MMC case, in order to achieve vector control of the line current and therefore straightforward desired injection of active and reactive power. Finally, the development of a reduced-scale laboratory prototype is presented and a full set of experimental results are provided, verifying the aforementioned concepts.
Institution: École Polytechnique Fédérale de Lausanne
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2056484235