Virtual Flux Based Direct Power Control Of Doubly Fed Induction Generator With Constant Switching Frequency

The knowledge about wind energy generation and the principle of doubly-fed induction generator (DFIG) is introduced to point out that DFIG could produce power with constant frequency under variable wind speed. It also could manage the output of active and reactive power to increase the efficiency of the machine.The control technologies of doubly-fed induction generator (DFIG) applied to wind power generation is under study during system balances. Conventional d-q axis current control using voltage source converters for both the grid side and the rotor side of the DFIG are analyzed and simulated. DFIG operation is investigated under balanced system. A conventional d-axis and q-axis control applied to voltage source converter(VSC) needs complicated coordinate transformation and its performance depends highly on accurate machine parameters.Multiple advanced control methods are explored and compared for balance operations. An innovative control called direct power control(DPC) is also investigated. This control achieves real and reactive power stability with simple active and reactive power control variables replacing the current control loops in the conventional case. A modified DPC algorithm integrated with virtual flux is proposed to eliminate the affection from the system disturbances. The simulation of the complete system is carried out in Matlab Simulink using PLECS blockset. The results verify that it can greatly improve the dynamic performances of the system.