Research On Control Strategy Of Doubly-fed Induction Generation System In Micro Grid

With the increasing contradiction between the environment and the traditional power grid,power production form is moving into the new energy,such as wind power,solar photovoltaic power generation has received support from the state,but these distributed power are uncontrolled,their mass access and can bring impact to power grid,the micro grid can integrate distributed energy and has the similar function of to power grid,the micro grid can be used as a backup power supply of power grid.The micro grid is integrated with micro power,load,energy storage system and control system.Controlling these distributed power is prerequisite for the stable operation of micro grid.The core of this paper is the control strategy of doubly-fed induction generation(DFIG).DFIG is one of the mainstream models,in this paper,under grid-connecte?isolated island,and the condition of unbalanced voltage control strategy of DFIG are studied.When the micro grid connects the grid,DFIG outputs the maximum power;when Island,the DFIG limits power by the pitch.DFIG is one of the mainstream models,in this paper,under grid-connecte?isolated island,and the condition of unbalanced voltage control strategy of DFIG are studied.When the micro grid connects the grid,DFIG outputs the maximum power;when Island,DFIG adopts the pitch angle limit power.Because of the micro grid contains a lot of power electronic devices,it is more likely to happen asymmetric or harmonic problems,in order to make the DFIG can adapt to various working condition of the micro grid,this paper also studies the control strategy of DFIG when asymmetric fault occurs.When micro grid occurs asymmetric fault,,in order to achieve the effective control of DFIG,according to the mathematical model of doubly-fed DFIG,with the improved vector control,asymmetric fault would produce negative sequence component,the negative sequence component in forward synchronous coordinates of double frequency component,join the resonant controller in the control loop used to filter out the influence of the double frequency component.Simulation shows that when the micro grid occurs asymmetric fault,the PIR control can restrain harmonic component,make the DFIG power output and the DC bus voltage are stable.Finally,this paper established a micro grid,which contains 20 kw DFIG 20 kw pv and 30 kw battery,and 20 kw doubly-fed wind power system as the main research object,under the environment of PSCAD_EMTDC simulation to check the feasibility and validity of the control strategy of DFIG.