Control Strategy Of Double-fed Wind Generator

With the energy crisis and environmental deteriorating, solar, wind, hydro and other renewable energy development are desperately needed. Wind energy as the most promising green energy, has become a hot national study. This paper deals with the control of the AC-excited power supply for the VSCF wind energy generation system with DFIG.According to the VSCF Wind Power Generation System of AC-excitation power supply requirements, analysis and compare five conversion circuit. The conclusion is that under the present conditions of power electronics technology, two-level voltage dual PWM converter as an AC-excitation power is the most competitive one.Analysis of the converter that located in the dual PWM converter power grid side. In the traditional voltage and current double closed-loop control mode, when the load is mutated,the control scheme of only d-axis current participation will make dynamic response limited, it proposes to make q-axis current also participate in the control.We call it iq≠0 of variable structure control scheme. Simulation results show that when the load mutates, using the above control scheme, the DC bus voltage fluctuation amplitude decrease about 40%, the ability of anti-system load disturbance is improved.In the study of the rotor side PWM converter, if the grid voltage is considered constant both in magnitude and frequency, the rotor current controller for the grid-voltage oriented vector control is studied. The principle and the realization scheme of the maximum wind energy tracking operation are investigated deeply. A grid-voltage oriented vector controller of DFIG is designed, which can make the system capture the maximum wind energy.On the platform of matlab/simulink simulation, we build the ac-excitation power module,which composed of the network-side and rotor-side PWM converter. The simulation results show that the proposed control scheme is feasible,it can meet the operational requirements of the DFIG, at the same time when grid voltage is constant, the system can keep good steady and dynamic performance.