The Controlling For Double-fed Wind Generator Ideal Voltage And The Small Network Voltage Dip

It is a hot focus of attention of the world energy industry for improving the energy structure, utilization of renewable energy, reducing environmental pollution and improving power quality. The wind power as a renewable energy technology is developing fast in the latest decades. In the variable-speed wind-energy conversion systems(WECS), especially the double-fed generator-based on WECS is paid more attention for its exclusive advantages. The primary research of this paper is about the controlling of double-fed wind generator under the ideal voltage and the small network voltage dip.Firstly, the mathematical model of the double-fed induction generator (DFIG) is built in different reference frames. The vector function of stator magnetic flux and stator voltage are deduced based on analyzing the mathematical model in a rotating reference frame. As a result, the chart of the whole system and the simulated model are constructed. The simulation results prove the effectiveness and reliability of the controlling strategy.By analyzing the topology and characteristics of the three-phase voltage source inverter and the deducing process of mathematical model in the three-phase stationary coordinate system, the simulation model based on switching function is constructed. The characteristic equation of DFIG is established as a result of building mathematical model of every part of DFIG system. Then the matrix eigenvalues are figured out ,besides, the maximum eiganvalue of the real part is trated as the fitness function, and the system PI parameter is optimized according to Particle Swarm Optimization algorithm. Under the condition of a sudden change of wind, the optimization of PI parameters shows that the PI control rules with PSO algorithm can effectively improve the dynamic properties of the system transitional process compared with the previous parameters design of PI regulation.Based on the analysis of conventional control strategy of stator voltage and grid-side converter for a DFIG system, an improved control strategy of stator voltage-oriented and grid-side converter are presented when the DFIG system is operating under the small network voltage dip. The Simulated models of the DFIG system operating in the different control schemes are built and simulated, and the results indicate that the improved strategy can effectively suppress the over-current of rotor side and over-voltage of DC-link under the condition of the small network voltage dip, therefore, improve the uninterrupted operational capabilities of DFIG system against the electrical network fault.