A Study On Modeling And Simulation Of VSCF Wind Power System

Variable-speed constant-frequency (VSCF) wind power generation, because of its high efficient porformance,gets more and more attention. This thesis, beginning at analysis of the operating mechanism, is devoted to detailed study on the technology of VSCF wind power generation. Double-fed VSCF generating is selected after a comparison among the fixed blade pitch scheme, the adjustable blade pitch scheme and the VSCF scheme, because it can capture the maximum wind energy by adjusting the blade pitch when the wind velocity is low and it can also ensure constant-frequency output, control stator active and reactive power respective by regulating the current input into rotor windings when the wind velocity is high. As a part of a wind power system, the adjustable blade pitch wind turbine is the wind energy conversion facility, whose matching with wind energy of the wind farm has great influence upon the operating of the system. Based on the statistic theory of wind energy, this thesis makes an elementary study on how to choose facilities of the wind energy conversion system and builds up mathematical models of wind velocities and the wind energy conversion system. The double-fed generator, who is superior to a general AC one in many aspects, and it is the hard core of the wind power system. After the analysis the essential operating characteristics, this thesis makes a study on the steady equivalent circuit and the power flow. Five-order-state equations in the M-T-0 reference frame are deducted in details and the stator flux-oriented vector control system is built to decouple the stator active and reactive power regulating and make controlling of the motor more simple. Inverter is the key equipment to make the double-fed motor VSCF operating, so the 6-pulsed AC-AC inverter, cycloconverter, is selected as the exciting power supply. Through processing the interface between the inverter and the generator, this thesis builds up the mathematical model of the inverter by analyzing its main configuration of the circuit, the method of cosine crossing and the producing of trigger pulses. In the end, the simulation models of all compositions of the wind power system are built up with the software Matlab6.5/Simulink5.0 and simulation experiments are done, whose results show that the models are proper and the VSCF wind power system has nice operating performances.