The Model Of Distributed Generation And The Research Of Control Strategy For VSCF Wind Power System

With the global energy supply, environmental pollution, as well as thedrawbacks of centralized power generation, long distance transmission andinterconnection of large scale power system appears day by day. There is anincreasing number of countries show interest and use of distributed generation. Runof the large grid systems and distributed generation systems have been manyelectricity experts and scholars think that is the main way to reduce energyconsumption and improve power system reliability and flexibility, a variety ofdistributed power in the modern power system to get a wide range of applications.Firstly, this paper analyzes three distributed generation characteristics and itsadvantages and disadvantages, while three distributed generation analyzed modeling.Three distributed generation models, photovoltaic cell model, simplified protonexchange membrane fuel cell model and wind power system model, are built withsimulation software. Three distributed generation related characteristic curve areobtained by simulation.Secondly, the Variable Speed Constant Frequency (VSCF) wind energygeneration system with doubly-fed induction generator (DFIG) is investigated. Thewind turbine is capable of capturing the maximum wind power below the rated windspeed and variable pitch control above the rated wind speed. According to theequivalent circuit of DFIG, the research on the rotor side converter based on statorflux-oriented control technique to achieve the stator output active power andreactive power decoupling control, while the grid converter based on grid voltageoriented vector control technique in to ensure that under the conditions of thenetwork side power factor unchanged, the DC bus voltage constant. Simulationresults verify the correctness and validity of the above control strategy.Then, the two processes of the grid voltage drop on the DFIG is analyzed.During the voltage drop there are severe electromagnetic transition of internaldoubly-fed generator, including that wind turbine output active power reduce andreactive power increases, the absolute value of the electromagnetic torque reduces,the generator rotor speed increases, the stator and rotor currents will increase. Theelectromagnetic torque and DC capacitor voltage will be a strong oscillation occursin the grid voltage drop and return moment. In three different voltage drop cases obtain dynamic response curve of doubly-fed wind power generation system,including that active power, reactive power, the generator rotor speed and so on.Finally, a small power system model with DFIG is built. Doubly-fed generatoroperating characteristics are analyzed respectively when there are single-phase shortcircuit and three-phase short circuit fault by simulation. It can be seen from theresults compared to single-phase short-circuit fault, three-phase short circuit faultwould have a major influence on wind power system.