| At present, wind power generation technology is one of the important parts of new energy power generation technologies, which will have the vital significance to promote the construction of smart grid and micro grid in the future. Therefore, the merits of wind power generation technology are directly related to the future grid whether can be reliable, safe, economic and efficient operation, and achieves the goal of environmental friendly. In this paper, the doubly-fed wind power generation system was the research object, and its mathematical model was instituted. The back-to-back voltage source converters were adopted in system, which were divided into the rotor side converter(RSC) and grid side converter(GSC), and different control strategies were established on the basis of different control objectives.Firstly, the control strategies were in allusion to RSC. When grid voltage stability, the vector control strategy based on power given and stator voltage oriented was adopted, in this way the active power and reactive power decoupling control and maximum power point tracking could be implemented effectively. The grid voltage fell slightly, considering the component of voltage fluctuations, the improved control strategy taking the grid voltage fluctuation in account was presented, which could implement the purpose of reactive power voltage regulator. On the basis of the control strategy, the electromagnetic calorimeters were analyzed that double frequency AC component exist in DFIG. The generalized integrator was adopted to improve the traditional PLL.The frequency and phase angle could achieve accurate detection by improvement PLL. Double frequency component could not be restrained with traditional PI controller. Thus, based on proportional- integral-resonant controller was put forward to improve the control strategy. The double frequency components were eliminated effectively, which implemented the DFIG of network fault ride through.Secondly, the control strategies are in allusion to the GSC. The vector control strategy based on grid voltage oriented was applied, and the control system was set up with double closed loop of voltage outer loop and current inner loop. In this way, DC bus voltage could be stabled and unit power operation realized. For harmonic problems, a LCL filter was introduced. Its inductance, capacitor, resonant frequency and damping resistance parameters were determined in this paper. Compared with L filter, better harmonic suppression was shown on LCL filter and the volume of inductance was even smaller.Finally, in view of the resonance problem of LCL filter, the active damping control was adopted by introducing filtering capacitor current. The improved active damping control strategy based on LCL filter circuit by introducing the capacitive current. The control effect was best by selecting modulation parameter 65ck(28),and damping resistance was saved,energy loss reduced, the stability of system improved. The grid-connected current was analyzed that its harmonic distortion rate less than 5% with the Fast Fourier Transform Algorithm by simulation, which meet the requirements of synchronization. |
