LVRT Control Reseacher On Permanent Magnet Direct-drive Wind Power System

With the advent of the new century, human beings into a new era, but human have toface energy shortage, such as coal, oil, natural gas and so on. Under human overexploitation, non renewable resources have left. Therefore, green clean energy has been thesubject of the world’s energy development. Under the situation with the theme, windenergy become a world concern, but there many problems in the wind power needs to besolved, especially under the grid fault, the wind can still continue to stay connected to thegrid, to implement low voltage ride through, to become the world’s wind energy to solvethe problem.In this paper, the object of study for permanent magnet direct drive wind powersystem low voltage ride through, key is to realize low voltage ride through, then naturecannot leave the control of the inverter machine side and network side. So this topicincludes the following contents:This paper analyzes the main circuit of double PWM converter topology principle andmathematical model in the three phase static coordinate system and rotating coordinatemathematical model; analysis of the mathematical model of permanent magnet direct drivewind power generator.Traditional double PWM converter machine side network side control strategyanalysis and synthesis; the crowbar circuit comparing three kinds of control; take duringcurrent transformer low voltage side through reactive power control strategy for reactivepower grid injection to help the gird voltage rise; on the original control strategy toimprove and get the machine side and network side converter coordinated control strategy;a fault occurred in most of asymmetric fault, thus improve the instantaneous symmetricalcomponent method is used to solve the problem of asymmetric fault, to make sure that thesystem can achieve low voltage ride through of the wind.Through constructing the permanent magnet direct drive wind power system lowvoltage ride through model. Firstly, validation is made of middle voltage fluctuation afterPI regulating control method is effective. Secondly, active crowbar circuit method in power grid failure also has good low voltage rid through ability. Finally, validationasymmetric fault in power gird, with the improved instantaneous symmetrical componentpower grid, the influence of permanent magnet direct drive wind power system low voltageride through.