The Research Of LCL-filter On Grid-side Of High-power Direct-drive Wind Power System

In recent years, along with the coal, oil, natural gas and other conventional energy depletion and environmental deterioration, countries are active in the development of the application of sustainable development to replace the sources of energy, wind energy with its rich, wide distribution, clean and can mitigate the greenhouse effect etc., as a kind of new green energy has great potential. Direct driven permanent magnet wind power generator rotor and the wind turbine is coupled directly, eliminating the gear box, improving the unit’s performance, improve the unit stability, in recent years it has gained extensive attention. In high-power wind power generation system, required the network side parallel LCL filter converter to filter harmonic currents to improve the quality of grid-connected electric energy. Study on large power converter LCL filter circuit to carry out research work.Firstly, according to the LCL filtering theory, from the resonant frequency, the total inductance restrictions of LCL filter component parameters were studied, put forward a complete set of LCL filter parameter design method. According to the capacity of the200kVA system, calculate a set of specific parameters used in simulation.Then, according to the Z plane system transfer function zero and pole distribution, analysis of LCL filter parameters on system performance.Secondly, established a LCL filter in the coordinates of the mathematical model, the synchronous rotating coordinate system, based on d axis voltage oriented, with LCL filter PWM grid-connected inverter voltage loop, current loop of the double closed loop control system was designed, and with Matlab/Simulink simulation to the system, comparative analysis of various parameters after the change of system performance changes.Finally, according to the LCL filter resonance phenomenon, analyses several typical active damping method. Using virtual resistance method, the control algorithm is modified to avoid resonance, while improving the system efficiency.