Studies On The Low Voltage Ride Through Of Variable Speed Wind Power Generator

With the increasing share of the wind power in the power system, the impact of its integration is becoming more and more widespread. And variable speed wind turbines comprised of power converters are getting more and more popular due to their advantages. Short circuit fault results in over-current of the wind turbine, which impacts the power electronic devices and the system operation. So it is necessary for wind turbines to be capable of low voltage ride through (LVRT). The LVRT issues of wind turbines are studied in this paper, and the main content is following:(1) The paper derives the dynamic model and steady-state models of the doubly fed induction generator (DFIG) and the directly-driven permanent magnet synchronous generator (D-PMSG) expressed in the reference frame rotating in synchronous speed; the aerodynamic model, shaft system model and pitch control model of the wind turbines model are presented; finally the overall model configuration of DFIG and D-PMSG based variable speed wind turbine models are presented.(2) The control models of DFIG and D-PMSG are studied; the decoupled control principle of rotor side converter of DFIG and grid side converter of D-PMSG are derived; the two converter controllers, wind turbine control system, DFIG and D-PMSG overall control system models are presented.(3) The impact of LVRT ability to DFIG operation and grid operation is analyzed. The LVRT control principle, control model and control strategy of DFIG and D-PMSG are investigated.(4) The action time of the rotor crowbar and the dc-link capacitance capacity of DFIG are studied. The LVRT ability of D-PMSG is presented and the voltage supporting characteristics of reactive current and reactive power of the generator during the low voltage fault are studied.(5) The large scale wind farms model is established in a real power system. The impact of wind turbine LVRT to large wind farm integrated is studied.