Research On The Operation And Control For Hybrid Wind Farms With DFIG And PMSG Under Harmonical Grid Voltage Condition

With the large-scale exploitation of the wind energy and the deeper researches on the wind power generation technologies,the reasonable configuration of hybrid wind farms according to the respective advantages of the different type wind turbines has been one of the mainstreams to expand the existing wind farm and develop the new installed wind farm with high capacity.Especially,a hybrid wind farm with doubly-fed induction generator(DFIG)and permanent magnet synchronous generator(PMSG)gets more attention.Most of the wind energy in China is distributed in the three-northern regions and the southeastern coastal islands,and the integration points of the wind farms are usually the located at the end of the network where is relatively weak in the power system.Meanwhile,a large number of the power electronics and the non-linearity loads would inevitably introduce the harmonics pollution.By considering the operation characteristics and the control capabilities of the different type wind turbines,the safe stability of a hybrid wind farm and the grid power quality at the point of the common coupling can both be improved by using a coordinated control between the different type wind turbines.In order to improve the adaptability of a hybrid wind farm with DFIG-and PMSG-based wind farm to the harmonic grid voltage condition,the operation performance and control strategy of the whole hybrid wind farms during the grid voltage distortion are investigated in this paper.(1)Based on the analysis about the mathematical and control models of the DFIG and PMSG systems under harmonic grid voltage conditions,two optimized control targets for the grid side converter(GSC)of the DFIG system are presented and the simplified model of a hybrid wind farm with DFIG and PMSG is established.The correctness of established model is validated and the operation characteristics of the hybrid wind farms with DFIG and PMSG during grid voltage distortion are analyzed by simulations.(2)The maximum output capability of the harmonic current of GSC and rotor-side converter(RSC)in the DFIG-based wind farm is analyzed in detail.Combining with the harmonic currents of the different control targets required by GSC and RSC under harmonic grid voltage conditions,the controllable operation areas of the DFIG-based wind farm is determined.Meanwhile,a multi-target coordinated control strategy of the DFIG-based wind farm during grid voltage distortion is further proposed and the simulation results under all operation conditions verify the effectiveness of the proposed control method.(3)The maximum output capability of the harmonic current of GSC in the PMSG-based wind farm is analyzed in detail.Combining with the harmonic currents of the conventional control targets required by GSC under harmonic grid voltage conditions,the controllable operation areas of the PMSG-based wind farm is determined.Meanwhile,a multi-target coordinated control strategy of the PMSG-based wind farm during grid voltage distortion is further proposed and the simulation results under all operation conditions are used to verify the effectiveness of the proposed scheme.(4)Based on the analysis about the control method of the PMSG-based wind farm to suppress the harmonic grid voltage at the point of the common coupling,a coordinated control of the hybrid wind farms with DFIG and PMSG under harmonic grid voltage condition is further proposed.The simulation results of a hybrid wind farm with DFIG and PMSG under all operation conditions demonstrate that the proposed coordinated control can effectively improve the power quality of the hybrid wind farms and the safe stability of the network.The research work of this paper provides the theoretical foundation for improving the stability and reliability of the grid-connected hybrid wind farm under harmonic grid voltage condition,which is helpful to the economic construction and development of large-scale wind farm.