VSC-HVDC System Control for Grid-connection of DIFG Wind Farms

The voltage control of wind farm is very important when the wind farm is connected to the power system using voltage source converter-high voltage direct current(VSC-HVDC) transmission.The performance of the wind farm voltage control will affect the wind farm operating status and power quality of the receiving end,as the traditional voltage amplitude-phase control scheme of wind farm is an indirect current control style,the dynamic response of the AC side current is slow and vulnerable to the systems parameters,this will deteriorate the voltage control of wind farm.Thus,it is necessary to find a robust control scheme to ensure that the entire system is operating effectively.In this paper,a VSC-HVDC system for the grid-connection of doubly-fed induction generator(DFIG) wind farms was used and by the dynamic model of the whole system was analyzed.A new wind farm voltage vector control structure for the wind farm side voltage source converter(WFVSC) was designed based on the steady-state equation.With the introduction of cross-product terms of a inner current loop,the control was decoupled and it could effectively overcome the adverse effects caused by wind farm parameter changes;On the grid side voltage source converter(GSVSC),the input-output linearization was designed to control the DC voltage.Finally,the power fluctuations of wind farms,the local load fluctuations of the wind farms,and the resistance parameters changing at the the wind farm side were simulated and the results show that the proposed control models are correct and valid.