Research On Fault Operating Characteristic Of Double-fed Wind Turbine And Relay Protection

Power grid’s stable operation is heavily influenced by wind farm’s large scale integration. Wind speed’s randomness and volatility makes the wind turbine’s output power unstable. What’s more, double-fed generator’s fault operation characteristic brings great challenges to wind farm’s stable operation. Research has been done to the relay protection of wind farm’s collector line to improve the stable operation of the wind farm and reduce the probability of wind farm’s off-grid accident. The research mainly included:1. The structure and operating principle of double-fed wind power generator is introduced. The mathematical model of doubly-fed induction generator (DFIG) at different coordinate system is discussed. On the basis of the mathematical model, a single DFIG grid model has been established with PSCAD tool and the operation characteristics under different wind speed has been done. The simulation result reveals the accuracy of the mode for the wind generator’s active and reactive power decoupling control can be accomplished by this model. DFIG’s operation characteristic under different fault condition was achieved with this model. According to the simulation result, the DFIG provides continuous currents when fault occurs and which has impact on power grid protection’s rapidity and selectivity.2. Aim at the shortages of wind farm’s electric circuit relay protection method, a novel protection strategy has been proposed and the action criteria has been detailed researched. The core concept is to combine wind turbine’s low voltage ride through ability and the adaptive inverse time low voltage protection.3. Experiments have been done to DFIG under different fault situation respectively with the proposed method and wind farm’s practical operation data on PSCAD’s established simulation model. The result shows that the adaptive inverse time direction of low voltage protection strategy matched with the fan of LVRT, can be implemented to all kinds of fault cases. It can realize the rapidity and selectivity demands under different fault conditions. The wind farm’s stable operation is significantly improved.