Transient stability analysis and optimal coordinated control of multi-terminal VSC-HVDC based offshore wind farms

This paper presents control strategies with specific control targets designed for generator- and grid-side voltage-sourced converters (VSCs) of wind turbines with permanent magnetic synchronous generator (WT-PMSGs) as well as those for rectifier- and inverter-side VSCs of multi-terminal VSC HVDC (MTDC) transmission system. With the proposed coordination control of VSCs in the WT-PMSGs and VSC HVDC system, the dynamic stability of the whole offshore wind energy system can be maintained under large disturbances. Then the particle swarm optimisation (PSO) method is proposed for tuning controller parameters of VSCs to improve the dynamic performances of the whole energy system. Finally, case studies for transient stability analysis are carried out to validate the proposed coordinated control strategy and parameters tuning by PSO method. In the testing system, two offshore wind farms and one AC power grid are interconnected as the meshed structure via the 3-terminal VSC-HVDC transmission system. The digital simulations are carried out with Matlab/Simulink.