Research On Control Strategy Of Converters For DFIG-based Wind Power Generation

With the lack of general energy source and the worsening of power supplycircumstance problems increasingly，it is provided with very important meanings topartially solve energy lack by using renewable energy source such as wind energyas the one of the most important clear substituted energy source in the future. Incomparison with the general wind energy generation system，because of equippedtransducer of VSCF doubly fed wind energy generation system located at rotorloop，it possesses the characteristics of small cubage，light weight and low cost，which only deals with slip power in double direction. VSCF AC excitation doublyfed wind energy generation system and its control technology is studied in thispaper.Firstly, discuss the basic characteristics of the wind turbine. According to theworking principle and characteristics of doubly-fed induction generator, the staticthree-phase coordinates and synchronous rotating coordinates are given. Thenpropose the rotor side converter control strategy based on the stator voltage vectororientation method, achieving generator stator active power and reactive powerdecoupling control, which laid a foundation for following chapters.This paper has derived the transient mathematical model of DFIG, and analysisthe transient performance of the doubly-fed induction. The results indicate thatlarge amplitude voltage drop will result in over-current and over-voltage, and posea serious threat to the DFIG system. Finally, in order to improve the low voltageride through capability of the DFIG, the rotor side crowbar protection circuit hasbeen studied. The results proved that the rotor side crowbar protection circuit caneffectively inhibit the rotor current during the voltage drop, and protect theconverter of DFIG, then achieve the low voltage ride through requirements.Next, aiming of the15kW doubly-fed induction machine, the main circuit ofthe tested system is designed. The system of DSP28335and its peripheral circuitare designed. The program flow chart of DSP28335and the control program flowchat of the rotor-connected converter are given. At last, on the established laboratory test platform of the wind power generator system, the relevant theory istestified and the experiment wave forms are shown.