Multi-Objective Control of Direct-Driven Wind Power Generation System with Frequency Separation

Variable-speed wind power generation system usually adopts maximum power point tracking(MPPT)below the rated wind speed or constant power control above the rated wind speed.However,single objective control has large dynamic loads on transmission systems.This paper presents a multi-objective control scheme for wind turbine in low wind speed,which achieves not only high power capture efficiency but also low fatigue load on mechanical parts.Input wind speed is separated into two components:a slowly varying seasonal component and a rapidly varying turbulent component.Correspondingly,the machine-side converter controller is divided into low frequency loop and high frequency loops.The low frequency loop implements MPPT control,the high frequency loop reduces the fluctuations of torque,and both loops together suppress the variations of output power.Simulation was conducted in Matlab/Simulink and FAST code was used to further verify the correctness of the multi-objective control strategy.