Research On Doubly-fed Through The Wind Power System Fault Fan

As a result of dual constraints of fossil energy depletion and environmental protection, wind power industry has a rapid development. The doubly-fed induction generator (DFIG) is one of the control technology of the main models of wind generation presented by doubly-fed induction generator (DFIG) has become a hot issue. Due to the low energy density of wind, the doubly-fed wind power generation and conventional power generation are different in mechanism and power electronic devices between DFIG and the grid is necessary for energy transmission. While the flow capacity of the power electronic devices is limited, the transient characteristics of short-circuit current will be complex under grid fault and the fault ride-through (FRT) ability is poor. In recent years, for the frequent large-scale wind turbines off grid occurrence, new wind power grid guidelines explicitly require that wind turbines must be capable of FRT ability. Therefore, it is of great importance to improve the LVRT capability of DFIG. Moreover, the FRT capacity and electromagnetic transient characteristics of DFIG are closely related. Thus, further study is conducted on the research of FRT capability in this dissertation on the basis of the variation law of the electromagnetic transient characteristics.Firstly, stable operational model of DFIG is built on the PSCAD simulation platform. A reasonable filter and control parameters is designed to satisfy the requirements of its access to the grid and the control strategies of Maximal Power Point Tracking (MPPT) and no-load cutting-in is further achieved. Secondly, based on the space vector model of FGIG based derivation of symmetrical fault, the stator and rotor flux and current analytical expression under symmetrical three-phase fault is derived. Analysis of the transient current mechanism of action is conducted and the correctness of the analytical results is verified by simulation. Thirdly, for the Low Voltage Ride-through (LVRT) of DFIG under symmetrical three-phase fault, a rotor Crowbar adaptive control method which based on voltage dip degree is proposed. Finanlly, for the High Voltage Ride-through (HVRT) cascading fault problem derived from the LVRT process is analyzed. The simulation results on the PSCAD platform confirmed the effectiveness of the proposed control strategies.