Control of HVDC-Light Transmission for Offshore Wind Farms Based on Input-Output Feedback Linearization and PSO

HVDC-Light has the advantages of flexible operating ways and reliability, especially in the transmission problem of offshore wind power. But it needs many PI controllers in the two converters (wind farm side, grid side). So there are many parameters need to be set which is difficult. This paper adopted the control mode that the outside loop controlled the voltage and the inside loop controlled the current. The inside loop made use of input-output feedback linearization method to make the nonlinear coupled converter mathematical model be linearization and decoupled. And it can substitute pole placement for PI parameters setting. Namely that it changed the problem of adjusting PI parameters to the one of pole placement. The control objective is to track the given values of active and reactive current from outside loops. The outside loop PI parameters are optimized with cooperation random particle swarm optimization(CRPSO) algorithm. Simulation results of Matlab/Simulink were compared with the conventional PI controller which show that the control method of this paper is effective. Key-Words: VSC-HVDC; Nonlinear control; Feedback linearization; Wind farm; PSO