Research On The Control Strategy For Grid-side Converter Of Doubly Fed Induction Wind Power Generators During Grid Swells

On account of the shortage of conventional energy and the accompanyingenvironmental pollution, a clean, efficient and diversified wind power generationtechnology has become a focus of discussion in recent years. While the low voltageride through technology of wind power generation technology in the (LVRT) hasdeveloped very well, the research of high voltage ride-through technology (HVRT)has not caused much attention. Grid voltage swell failure and grid voltage dipfailure are the two typical ones in grid failure, of which the first do more harm tothe converter. Therefore, it is urgent to do some research on the influence of gridvoltage swell to the converter and the relevant control strategy of high voltage ridethrough. Based on the research of DFIG, some research has been done about thecontrol strategy of the converter of the grid under the grid voltage swell. From thetheoretical analysis to the simulation, and to the experimental verification, thispaper is a thorough analysis and research carried on step by step.In order to get a better analysis of the impact of grid voltage swell on theDFIG grid-side converter, a complex state variable under the grid voltage swell isestablished first. With a small signal analysis of the DFIG grid-side converter underthe circumstances of grid voltage swell, it comes to that the grid voltage swellaffects the dynamic characteristics of grid side converter in terms of theoreticalanalysis and simulation. It provides the theoretical foundation for putting forwardthe control strategy of DFIG grid-side converter under the grid voltage well.For the impact of the grid voltage swell on the converter of the DFIGgrid-side, several feasible control strategies have been put forward successively,such as Dynamic over-modulation、increase the DC side voltage given、increase theperceptual wattless power and so on, whose validity and feasibility are verified bysimulation.Based on the theoretical analysis and simulation research, a11KW DFIGexperimental platform of high voltage ride-through DFIG system has been built.The experimental research for the proposed control strategy is carried on theexperimental platform and the wave shape is analyzed, whose results accord withthe one under theoretical analysis and the simulation. Through detailed theoretical analysis, this paper proposes the relevant controlstrategies whose validity and feasibility are verified by the simulation andexperiment. This research will explore new ideas and new methods to the relevantstudies and tests of high voltage ride-through technology of the DFIG system.