Modeling and Multi-Working Condition Simulation Research on AC/DC Grid-Connected System of Direct-Drive PMSWG

Aiming at the stability and fault ride-through challenges faced by large-scale wind power grid connection, this paper takes the direct-drive permanent magnet synchronous wind generator (PMSWG) as the research object to conduct research on the modeling and control strategies of AC-DC grid-connected systems. Firstly, the mathematical models of the wind turbine, PMSWG and grid-connected converter are established,and an AC-DC grid-connected topology based on a double-PWM converter is proposed. Secondly, a double-closed-loop control strategy of "DC voltage outer loop-grid-connected current inner loop" is designed to achieve active/reactive power decoupling control and grid connection with a unity power factor. Finally, a low-voltage ride-through scheme based on a DC-side unloading circuit is proposed to improve the system's fault ride-through ability. Through MATLAB/Simulink simulation, it is verified that the proposed model and control strategy can achieve maximum wind energy tracking under various working conditions such as basic wind, gust, and random wind. The harmonic content of the grid-connected current is less than 1%, and the system can still maintain grid-connected operation when the grid voltage drops by 20%, providing technical support for large-scale wind power integration.