| Since several accidents which caused large scale wind turbines get off the grid occurred in 2011, LVRT technology has become a major research focus. While with further research, it was found that low voltage failure often cause high voltage failure which will bring a new large-scale wind turbines off-grid accident. Therefore, the new wind turbines should not only meet the current specification of low voltage ride through but also need to have high voltage ride through capability. The paper mainly study for wind power high/low voltage ride through technology, carry out the following tasks:First, study the VSCF wind turbines separately,which include permanent magnet direct drive wind turbine(PMSG) and doubly-fed induction wind turbines(DFIG), etc., and analyze its mathematical model.Then studied the causes of low voltage fault and high voltage fault, analysis the breakdown characteristics of PMSG and DFIG under voltage fault, take a analysis of the existing low/high voltage ride through strategies,and proposed the voltage ride through strategy which based on the super-capacitor.To build PMSG model in the Matlab/Simulink software, the permanent magnet direct drive wind turbine model is divided into blocks, including wind parts, generator parts, machine side converter(MSC), the grid-side converter(GSC) and DC bus section. Optimizing the MSC and GSC control strategies,which can help the grid voltage recovery during the voltage fault.At last,simulated the low/high voltage fault, observing the PMSG states with the comprehensive voltage ride through strategy, the simulation results show that the comprehensive voltage ride through strategy can be maintained at a low voltage and high voltage fault. The strategy can stabilizing the DC bus voltage, issued capacitive or inductive reactive power to help the grid voltage recovery.Achieve the purpose of low / high voltage ride through. |
