Mechanism Analysis Of Cascading Trip-off Of The MW Class Doubly Fed Wind Turbine

With the needs of the traditional fossil energy shortage and transformation of the mode of economic development, the development of renewable energy use has been widespread concern all over the world. Wind power technology is a kind of the most mature renewable energy application technology, by the extensive attention of all countries in the world and promote, in the power system installed capacity proportion of machine in the expanding. But due to lack of low voltage ride through capability, the reactive power control is not in place, inside the equipment defects and wind farm operation and management etc. there are many problems resulting in wind turbine off grid accidents occur from time to time.With the wind power in Yunnan as the background, introduced in recent years, several chain off network accident case, analysis of the direct cause of tripping, and a wind farm in case of a detailed analysis of the result does not meet the low voltage ride through specific process set off network requirements, put forward the corresponding wind turbine off the chain accident measures. The doubly fed wind turbine current as the research object, established the dynamics model of air turbine wind speed model, transmission model, generator model and inverter model. And according to the flux conservation principle, the terminal voltage sags under three-phase short-circuit mechanism of doubly fed generator electromagnetic transient process the characteristics and its relationship with DFIG, a transient model of doubly fed wind turbine generator set. The analysis found that during the period of three-phase short-circuit fault transient current in the rotor. There exist the steady state component, the transient DC component and the transient component, and the transient DC part is the main reason that leads to the phenomenon of over voltage and over current in the rotor winding.The three-phase short-circuit occurs in the power grid, voltage fall sharply doubly fed wind turbine applied crowbar circuit of low voltage through performance were studied, is doubly fed wind turbine crowbar circuit inputs in the calculation model, grid voltage sag 80% of the transient characteristics are analyzed, and the on grid voltage sag 80% of low voltage ride through the simulation, verifies the importance function of low voltage ride through (LVRT).