Analysis on damping characteristics of multi-terminal VSC-HVDC system connected to wind farm

Abstract

In order to study the influence of wind power grid connection on the small-signal stability of the multi-terminal VSC-HVDC system, based on the complete doubly-fed wind turbine model, damping characteristics of the multi-terminal VSC-HVDC system are qualitatively analyzed. Analyzed the influence of the doubly-fed induction generator (DFIG)-based wind turbine (WT) connection on the damping characteristics and stability of the multi-terminal VSC-HVDC system from multiple perspectives including the access point of the WT, the WT’s capacity and transmission distance. The methods of the eigenvalue analysis and time-domain simulation analysis are adopted in this paper. Firstly, a complete three-terminal VSC-HVDC system model is built in PSCAD, and the systems after the WT connected to the grid are analyzed and compared. Then, based on the total least squares-estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT) algorithm, some information of the system can be obtained such as eigenvalue, frequency, damping ratio and so on. The research results show that when the WT is connected to the inverter side, the damping ratio tends to be greater than connected to the rectifier side. In addition, within a certain range, as the capacity and transmission distance of the WT increase, the damping ratio also tends to increase. In this way, it provides a technical reference for the planning of wind farm access to multi-terminal VSC-HVDC system