Design And Realization Of Rotor Side Converter For Doubly - Fed Wind Turbine

Along with the increasing of haze weather, more and more people focus on the environment, resources and sustainable development. The study and development of new energy such as wind, solar and ocean wave energy have been supported by the national policy.At present, the doubly fed induction generator(DFIG) has been widely used in various kinds of wind farms due to its effective wind energy utilization, excellent LVRT ability, stable grid-connected performance. The power converters of doubly-fed wind turbines mainly use the back-to-back structure, the main function of its rotor side converter(RSC) is to realize a variety of control objectives such as variable speed constant frequency(VSCF) control, the decoupling control of active and reactive power of the stator, maximum power point tracking(MPPT) and so on by means of via effective excitation control of the rotor.The RSC of doubly-fed wind turbines was studied and designed in this paper, and an experimental platform was set up to verify the stator-voltage-oriented vector control strategy of RSC at different wind speed. The main contents include:Firstly, the present developing situation of RSC of doubly-fed wind turbines was studied, the back-to-back converter system of doubly-fed wind turbines with RSC as control core was described, the existing control strategies of RSC were analyzed.Secondly, the conventional mathematical model of DFIG and its RSC was established as well as their mathematical model under the dq synchronous rotating coordinates. The stator-voltage-oriented vector control strategy of RSC was analyzed and derived in details. This control strategy observes directly voltage more accurate than observing flux linkage, so the control system is more stable and affected less by dynamic disturbance of DFIG.Then, the RSC of doubly-fed wind turbines was designed. The design of its hardware included the design and device selection of power circuit and secondary circuits. The design of its software included the angle setting, smooth start of doubly-fed wind turbine, VSCF control and the switching control between sub-synchronous, synchronous, super-synchronous state.Finally, the simulation experiment platform of doubly-fed wind power generation including those of RSC and the controller of wind turbine was designed and built. Then a series of RSC excitation control tests at different wind speed was finished respectively. The experimental results were analyzed and show that the control of RSC is stable with fast respond at different wind speed, the system can start smoothly, can also operate and switch stably at/between the sub-synchronous, synchronous, super-synchronous state, as well as realize VSCF and MPPT control, and the expected goals have been achieved.