The Research Of Three-level Converter For DFIG Wind Turbines

Wind power is an inexhaustible clean and renewable energy. Because wind powergeneration has become the most large-scale development and commercial prospects fordevelopment in the new energy power generation technology, Wind power has become theworld’s fastest growing renewable energy source. For the parallel operation of wind powercan get compensation and support from the state grid, so it has become the mainstream inthe wind. Doubly fed wind power generator has the characters of variable speed, decoupledcontrol of active and reactive power, reduced mechanical stress and noise, improved powerquality, small slip power (about30%of the rated value) etc. And it has now become theVSCF wind power generation model the most widely used model in industry application.As the core of energy conversion, the converter is widely used in industry and allaspects of life. Among them, the voltage type of back-to-back converter can realize activeand reactive power controlling, and can also realize two-way flowing of energy, smallharmonic, DC voltage controlled, For that, it is taken account in clean energy, energysaving and emission reduction, and has been widely concerned.This paper has firstly analyzed the mathematical model of the doubly-fed motor andpower flow. And then analyzd the mathematical model of three-level converter and thecontrol strategy of inhibiting neutral voltage unbalance. On the existed experimentalconditions of choosing the3.7KW doubly-fed induction generator for the experimentalplatform, using an asynchronous motor to simulate doubly-fed generator and a frequencyconverter to driver the asynchronous motor, we did two-level converter experiments ofno-load grid-connection, verifying the feasibility. And a simulation model was establishedfor simulation.