Under middle-low wind speeds condition, which is in the middle and lower sections of MPPT wind speed field, efficiency of wind power system is very low. This restricts the utility of this type of wind energy resource. Based on the relationship between DFIG wind power system efficiency and DFIG rotor rotation speed, a new MPPT with dynamic matching method was introduced to enhance the power conversion efficiency, which includes a certain turbine kinetic energy accumulation and release cycle. This method transfers turbine kinetic energy from lower rotation speed to higher rotation speed to convert mechanical energy into electrical energy by generator, which has higher efficiency. Base on theoretical analysis and simulation, the new dynamic MPPT method is proven to exhibit totally higher electrical efficiency than conventional MPPT.
Keywords DFIG wind power system, Middle-low wind speed, Dynamic maximum power point tracking, Dynamic matching method, Efficiency enhancement