Vector And Decoupled Control Development For Doublely-Fed Machines

In this pap er, rotor f ield-orientiated vector control algorithm for Brushless Doubly-Fed Machines (BDFM) is presente d. Meanwhile, the control algorithm is tested in Simulink, which is a simulation kit in Matlab.Firstly, considering the well-know n"cro ss coupling"theory , the structure of BDFM is investigated, and the coordination between the number of stator slots and rotor bars is developed. At the same time, the basic equations of BDFM are developed. Considering the electrom agnetic couple re lationship between power windings and rotor's power subsystem, and between control windings and rotor's control subsystem, the BDFM's voltage equations, electrom agnetic torque equations and m echanic equations are derived.Secondly, free-axis (d-q) m odel of cag e-rotor BDFM is derived from basic equations, and the axis is layed on r otor to simplify it. Based on the rotor-axis model, the operation characteristics and th e efficiency of BDFM can be easily analys ed in asynchronous m ode, synchronous mode a nd doubly-fed mode respectively . By comparision, it is found that BDFM can win a higher efficiency when it works as a generator in super -synchronous mode, and th e efficiency degrades gradually under asynchronous m ode,super-synchronous generator m ode,and synchronous m ode, while the efficiency will be lowest when BDFM work under sub-synchronous braking mode.Finaly, rotor field-orien tiated vector control algor ithm is inves tigated. The investigation is started with devel oping BDFM double-synchronous-axis m odel, which is followed by the deriving of vector control equations. It is proved by t he simulation result that the vector control algorithm can well im prove the performance of BDFM.In respect of the contents discussed above, the BDFM mode l and the vector control algorithm is evaluated too.