Study On Active Power Control For DFIG Based On Equilibrium Manifold Expansion Model

The primary frequency contribution of synchronous units raises with the intense increasing of the wind power penetration,leading to a frequent start-up and shut-down of synchronous units,which will shorten its mechanical life.Therefore,it's necessary for wind turbines to participate in active power regulation of the power grid.Since the nonlinear characteristics in active power control of wind turbine limits the use of classical linear control theory,a benchmark model is needed for utilizing modern control theory.Introducing the theory of equilibrium manifold expansion(EME)model into the study of active power control in wind turbine,this disseratation research on the active power control of DFIG by identificating the EME model of DFIG,designing active power controller,ascertaining the strategy of DFIG participating in primary frequency regulation.Firstly,this disseratation identifictes the EME model of DFIG in active power control by analysing the structure of EME model of classic noliner systems and the charastericstics of DFIG in active power control.The accuracy of DFIG EME model is implied by simulation results.The impact to EME model identificting deviation of different dispatching variable choices and different mapping designs are also studied.Secondly,a classic feedback linearization controller form basing on EME model is gived according to the analysis of feedback lenearization theory.The lineariztion result and control result of designed feedback linearization controller of DFIG basing on EME model and designed PID controller are proved by simulation results.Finally,the designed active power controller is employed in DFIG participating in primary frequency regulation of power grid.Meanwhile,to take the advantage of DFIG in rapid respond to rotor control,a primary regulating strategy of DFIG by distinguishing power fluctuating frequency is presented.DFIG is expected to participate in primary frequency regulation as a substitute for thermal unit in fast varying component of frequency fluctuating.Simulink model of a micro power grid with twenty percent wind power penetration is established to verify the advantages of supposed strategy.