Research On The Speed Identification Of Brushless Doubly-Fed Stand-Alone Generating System Based On Control Winding Current Oriented

Variable speed constant frequency(VSCF)is the technology that maintaining a constant voltage frequency with variable rotor speed,which has become a hotspot in new energy power generation field.The VSCF stand-alone generator system based on doubly-fed machine has been widely used in ship shaft generator system,minitype aerogenerator and hydropower system for its advantage of smaller,lighter,cheaper.However,the brush and slip ring in traditional doubly-fed system are so easy to be weared that the system's reliability is decreased and cost is increased.Brushless doubly-fed induction generator(BDFIG)can avoid this problem.BDFIG has two sets of stator windings and one set of rotor winding.There is no coupling between two stator windings but they are both coupled with the rotor winding.Thus,it is feasible to control one stator winding so that to influence the other stator winding indirectly.BDFIG retain the advantages of doubly-fed system but also enhance reliability,lower the cost,which has broad prospects.The speed of rotor is the necessary information for VSCF.However,the speed encoder in the system brings mechanical burden and then partly weakens the benefits introduced by the brushless structure.Thus,doing research about speed identification of brushless doubly-fed stand-alone system means a great deal to enhance system reliability and saving cost.Following research has been done in this paper about speed identification of brushless doubly-fed stand-alone system:(1)Carried out the analysis about the principle of VSCF in doubly-fed system.Mathematical model of three-phase is shown according to the rotor structure of BDFM.Unified reference frame dq model is introduced for more convenient control.Vector control scheme of control winding(CW)current oriented is analyzed by discussing the feature of stand-alone generator system.(2)Carried out the design the speed estimation system based on model reference adaptive system(MRAS).The principle of MRAS is discussed,and furthermore,a new MRAS of speed estimation is designed for covering the shortage of traditional MRAS.According to the feature of CW current oriented system,q-axis component of CW current is selected to be the model in the new MRAS,which specifies the identification process.(3)Carried out the sensitivity analysis of parameters and performance optimization of above identification system.Aiming at the problem of identification error caused by parameter drift,the study about parameter sensitivity is carried on,and the deviation tendency of identification result caused by parameter deviation is discussed,which make sense of guide the estimation of parameters to minimize the identification error.On the basis,the frequency closed loop is designed to correct the identification error that is hard to eliminate under the promise of not influencing the rapidity of identification system.In order to validate the effectiveness of above analysis and design,the simulation model and experiment platform are built in Matlab/Simulink and laboratory respectively.Both the simulation and experimental results prove the effectiveness of above design.