A General [P Q]-[ω V] Model of Hybrid GFM/GFL Multi-VSC Systems: Power Oscillation Analysis and Suppression Method

Abstract

Power, voltage, and frequency oscillation or instability of a multivoltage source converters (VSCs) system will threaten its stable operation. From a power system point of view, the four variables [ P Q ]-[ ω V ] are the key characteristic indicators that are paid attention to, which are usually used to describe the nodal dynamic characteristics, instead of the traditional impedance model. With that in mind, this article establishes a general [ P Q ] - [ ω V ] model of a hybrid GFM/GFL multi-VSC system for power oscillation analysis, where the system structure is not limited to a special star topology. The general [ P Q ] - [ ω V ] models of VSCs under typical grid-forming and grid-following control schemes are comprehensively built. As a result, it could serve as a standard model that provides a convenient and universal tool for both the low and medium frequency (a few tenths to tens Hz) power oscillation analysis and stability analysis. Moreover, the proposed model can locate the weak nodes with severe power oscillations and evaluate the effect of the oscillation suppression methods. To suppress the system medium frequency oscillation, a washout-filter coupling feedback control method is proposed with more control freedom and improved dynamic performance. Finally, the control-hardware-in-loop experiment results verify the theoretical analysis.