A Robust Controller Design for Mitigating Control Loop Interactions in Multi-VSC Systems Built by Multiple Vendors

Control loop interactions among voltage-sourced converters (VSCs) sharing the same alternating current (AC) system and the disruptive impacts of these interactions on the stability of multi-VSC systems have been widely studied in the literature. This paper proposes a controller design method for mitigating the negative impact of these interactions on the stability of multi-VSC systems. The proposed controller design approach incorporates the external interactions as uncertainties into the system model and obtains the outer controllers of individual converters using $H_{\infty}$ controller synthesis. The controllers are designed based on the model of individual VSCs rather than the exact model of the interconnected multi-VSC system, and thus they require only the exact model of individual VSCs and a reduced-order model of coupling dynamics. This modeling requirement ensures design confidentiality in multi-VSC systems built with multiple manufacturers due to the individual design of converter controllers, which does not require the exact model of adjacent converters. The performance of the proposed robust controller is evaluated using time-domain simulations and eigenvalue analysis in MATLAB/SIMULINK.