| The wind energy has obvious distribution in dimensional-domain and stochastic variation in time-domain which will lead to power oscillation,generation efficiency reduction,and even units shutdown.A perturbation compensation based sliding-mode control(PCSMC)for the current permanent magnetic synchronous generator(PMSG)under complicated and uncertain conditions is developed in this work to realize robust variable speed and variable pitch control.And the key points of this work can be summarized as follows:(1)The non-linearities,strong coupling,and multi-variables of PMSG mathematical models are established based on the fundamental theory and structure of wind power generation system,the variable speed control mechanism,and the power control principle.Then,the above models are transformed into two-phase rotation coordinate system by coordinate alternation to intuitively describe the dynamic characteristics.And the corresponding MATLAB/Simulink simulation models are also built which provide a powerful tool to evaluate the performance of the proposed method.(2)A PCSMC is presented based on perturbation observer and sliding-mode control(SMC).Firstly,the system non-linearities,uncertain parameters,unmodelled dynamics,and external time-varying disturbances are online estimated by state and perturbation observer(SPO)in real-time.Then,the modified SMC is adopted to fully compensate the above estimated perturbations online for global control consistency.Further,PCSMC has the prominent advantages of strong robustness,which does not require an accurate model.Compared with the traditional SMC,the upper bound of perturbation considering the maximum accessibility is replaced by its real-time estimate.And the saturated function sat(·)is used to replace the normal symbol function sgn(·)to weaken system chattering.(3)The designed PCSMC is applied to achieve robust variable speed control for PMSG under the lower rate wind speed,which aims to capture high-quality maximum power point and increase the energy conversion efficiency.Above all,the state space equation is acquired according to the PMSG mathematical models represented in(1).Based on the theory of PCSMC described in(2),the non-linearities and complicated uncertainties are aggregated into the new perturbations for mechanical rotation speed ωm and d-axis current id,respectively.Lastly,the third order and second order SPOs are utilized to estimate new perturbations,respectively,which are fully compensated by modified SMC.The proposed method is insensitive to the precise system model and parameter uncertainties,while only the state of ωm and id is needed.Besides,MATLAB/Simulink simulation results under step wind speed,low-frequency random wind speed,high-frequency random wind speed,and parameter uncertainties prove the effectiveness and strengths of PCSMC.And a hardware-in-the-loop(HIL)emulation based on dSpace platform is completed to sustain its hardware availability.(4)The designed PCSMC is applied to come true robust variable pitch control for PMSG under the above rate wind speed,which aims to keep output power at its rated value,reduce the system load,as well as guarantee units safety.First of all,the state space equation is structured based on the PMSG mathematical model depicted in(1).Then,the non-linearities and complicated uncertainties are aggregated into the new perturbations for mechanical rotation speed ωm and d-q axis current id,q according to the theory of PCSMC described in(2),respectively.Moreover,the third order and second order SPOs are employed to estimate the new perturbations,respectively,which are fully compensated by modified SMC.The presented strategy is insensitive to the rigid system model and parameter uncertainties,while only the measurement of ωm and id,q is required.Furthermore,MATLAB/Simulink simulation outcomes obtained in ramp wind speed,random wind speed,and flux variation demonstrate the validity and superiorities of PCSMC.And a HIL test based on dSpace platform is undertaken to reveal its implementation feasibility. |
PDF Full Text Request