Adaptive VSG Control Strategy of Sending End for Large-Scale Renewable Energy Connected to Weakly-Synchronized Support VSC-HVDC System

Renewable energy collection and output through voltage source converter based high voltage direct current (VSC-HVDC) technology is an effective way to promote renewable energy consumption. However, the continuous increase in the penetration rate of renewable energy has led to a continuous decline in the strength of the power grid, and the traditional grid-following (GFL) converter technology can no longer meet the needs of stable system operation. In order to improve the adaptability of the weak grid of the system and meet the application scenarios of large-scale renewable energy connected to weakly-synchronized support VSC-HVDC system, this paper proposes to adopt VSG control strategy in the converter station of the sending end of the VSC-HVDC system. Firstly, a small signal mathematical model of rectifier-side control is established, and the influence of virtual impedance on system stability is studied by the root locus method. Secondly, an improved virtual synchronous generator (VSG) control algorithm for constructing virtual reactance adaptive adjustment items using electrical quantities such as alternating voltage (AC) change rate and voltage difference is proposed, which can improve the equivalent short-circuit ratio of the AC system at the sending end while ensuring that the equivalent impedance of the system is inductive, so as to improve the overall performance of the system. Finally, the effectiveness of the proposed control strategy is verified by PSCAD/EMTDC electromagnetic transient simulation.