On The Advanced Control For Power Electronic Systems And Its Applications

Encouraged by rapid technological achievements in smart grids and renewable en-ergy systems,power electronic converters have been involved in various electric appli-cations,ranging from generation,storage,transmission to consumption.The accurate regulation of output voltage is of significant importance in obtaining satisfying perfor-mance for the connected industrial loads or devices.It is a challenging task to achieve the accurate voltage regulation owning to the fact that the converters are essentially nonlinear systems with couplings between control inputs and states.Apart from these,it is well known that the control performance of converter system is always severely affected by sources of parameter uncertainties and external disturbances,e.g.circuit parameter perturbations,load resistance variations,input voltage fluctuations.When considering conventional linear controllers,limited control precision cannot satisfy the higher and higher requirements,especially under large external disturbances and model uncertainties.It is imperative to develop a reliable controller which can keep a nice balance between static and dynamic performance.This dissertation focuses on the output voltage regulation problem of typical power electronic converters,including DC-DC converters and DC-AC inverters.Taking the mismatched disturbances into consideration,composite control schemes are proposed to remove the effects,which are developed by combining the advanced nonlinear ap-proaches with disturbance observers.Both simulations and experimental results are illustrated to show the feasibility of the proposed composite methods.The main results and contributions are concluded as below:1.Robust backstepping control of DC-DC buck converter systems in the presence of time-varying disturbances.Based on the nominal model of DC-DC converter,the accurate output voltage regulation problem is investigated by considering the input volt-age fluctuations and load variations.In this chapter,generalized-proportional-integral observers(GPI observers)are firstly constructed to estimate the lumped time-varying disturbances.By introducing the disturbance estimations into the design process,a composite GPI observer-based robust control scheme is developed.As compared with the conventional backstepping control,the proposed algorithm performs a promising dis-turbance rejection ability.Rigorous stability can be guaranteed.Experimental results in the presence of time-varying disturbances are illustrated to show the feasibility of the proposed composite method.2.Finite-time current sensorless control of DC-DC converter systems with multiple time-varying disturbances.Only the asymptotical convergence of the voltage track-ing error can be obtained with the above mentioned backstepping approach.In this chapter,a recursive design based universal finite-time observer(UFTO)is applied to simultaneously reconstruct the current information and lumped disturbances.Then,a non-singular sliding mode control based current sensorless finite-time control strategy is developed for the converter system to improve the transmit behaviours,control ac-curacy and fault tolerance ability in the presence of various time-varying disturbances.A rigorous analysis on robustness stability has been provided for the proposed method.Experimental results are explored to comprehensively illustrate the effectiveness of the proposed strategy.3.Discrete-time fast terminal sliding mode control design for DC-DC buck convert-ers with mismatched disturbances.A novel digital fast terminal sliding mode control(FTSMC)approach is investigated for DC-DC buck converters with mismatched distur-bances.The approximated discrete-time model of the converters is firstly obtained and analyzed based the Euler’s discretization method.Then,by adopting the delayed estima-tion technique,it is easy to obtain the accurate estimations of the lumped disturbances.Integrating disturbance compensations into the modified digital fast terminal sliding mode surface,the proposed controller is finally constructed on the basis of equivalent control method.Performance analysis is presented.Both simulation and experimental comparisons are made for the proposed digital FTSMC approach to validate the effec-tiveness of the presented controller.The proposed FTSMC approach is characterized by higher voltage tracking accuracy and better dynamic properties.4.Robust voltage regulation of DC-AC inverters with load variations via a harmon-ic disturbance observer based control(HDOBC)approach.In this chapter,a HDOBC approach is proposed for the robust voltage regulation design of a DC-AC inverter sys-tem.In distributed generation systems,wide range of load variations and effects of nonlinear loads result in significant degradations of control performance.Moreover,the loads,as the mismatched disturbances,impose adverse influences on the inverter system via a channel different from the control input.Toward that end,a harmonic disturbance observer is proposed to estimate the periodic load disturbances.By constructing new disturbance compensation gains,the effects of the mismatched periodic disturbances are removed from the output voltage channel.Rigorous stability analysis for the closed-loop system is presented.Experimental results are explored to illustrate the feasibility and capacity of the proposed control scheme.5.Current sensorless sliding mode control for DC-AC inverters with load variations via a universal state and disturbance observer(USDO)approach.In distributed gener-ation and electric vehicle systems,wide range of load variations and effects of nonlinear loads result in degradations of control performance.Load variations are coupled with output voltage.Meanwhile,the cost increases significantly due to the requirement of wide-band current sensors.To solve this problem,a USDO is developed to reconstruct the inductor current in the presence of load disturbances.By integrating the estimations of load disturbances and inductor current into the sliding surface,a current sensorless sliding mode controller is proposed.It is shown that the proposed controller can guar-antee a rigorous stability of closed-loop system.Furthermore,considering higher-order harmonics,the baseline USDO can be extended so as to reject these harmonics.Exper-imental results are illustrated to verify the effectiveness of the proposed scheme.