Research On Vector Control Strategy Of Brushless Doubly-fed Induction Generator For Stand-alone Generation System

The Brushless Doubly-Fed Machine(BDFM)is a new type of AC induction machine,it operates in different modes.The rotor of BDFM has some advantages for its simple structure because it avoids the use of brush and slip ring,so it is more reliable than conventional Doubly-Fed Machine(DFM).The structure and control performance of BDFM is similar to that of DFM which has wound-rotor,it will have a good prospect in the adjustable speed and power generation systems since it is able to control power factor with a small capacity converter.In this paper,control strategy of wound-rotor BDFM in generation mode,which called Brushless Doubly-Fed Induction Generator(BDFIG),is researched,based on the winding design of the stator and rotor,the operation principle of the motor is described briefly,the dynamic mathematical model and the equivalent circuit are deduced to obtain the active and reactive power flow direction and distribution relation.BDFIG is suitable for stand-alone generation systems.Achieving optimum dynamic response performance is more complex than for DFM.it has no reference of frequency from electric network,although the voltage of the power winding is build,the magnetic flux angle could be changed because of load variations.The present paper develops a novel vector control scheme based on the synchronization reference frame of magnetic flux angle in power winding,initial generator operation state is build first,and then power winding field angle can be observed.Considering obtained power winding field angle causes accumulative error of output frequency in dynamic behaviors,angular frequency closed-loop is build.Experimental results show a good dynamic response and steady state performance at different operating mode of generator system,and the generator output keeps a constant voltage and frequency..The research of BDFIG working in stand-alone power generation system has strong practical significance,the work in this paper has played a certain role in promoting the practical use of stand-alone power generation systems.