Research On Wind Power Grid For Low Voltage Ride Through Technology

With the background of highly rise demand of energy, gradual exhaustion and hugewaste of traditional energy, the wind as an emerging green energy has aroused widepublic concern. With the booming of the wind power generator technology, the windpower generation capacity is rapidly increasing, its influence on grid is becoming moreand more remarkable. The low voltage ride through(LVRT) technology is one of themost important technologies.At first, this passage introduces the current research conditions of wind power andLVRT, and some usual LVRT technologies. Then discussed the VSCF doubly fedinduction generator (DFIG) working principle, established mathematical model ofthree-phase stationary coordinate system and the two-phase rotating coordinate system.Analyzed dual PWM converter, and studied the network side and rotor-side convertermathematical models and control strategies.Then for the voltage drop caused by grid failure, summarized the network faulttypes. Put forward to improve the control strategy for slight voltage drop failure; to additionprotection circuit to protect wind turbines for severe voltage dip fault. TheMatlab/Simulink simulation models are established for crowbar circuit and seriesdynamic braking resistor (SDBR), and proposed the switching control strategy of theprotect circuits. According to different standards abroad and China’s actual situation,introduced the low-voltage ride through technical requirements of China.Finally, based on Matlab/Simulink simulation platform to build doubly-fedinduction generator (DFIG) wind power generation system simulation models, inserious voltage drop case, contrast with without any protection circuitry, and thecrowbar circuit protection as well as joint series dynamic braking resistor (SDBR).Experimental results show that this scheme can be a good limit rotor side current, DCvoltage, to protect the wind turbine and keep them up with grid, and achieved thetechnical requirements of the low voltage ride through.