Research On Repetitive Control And Its Verification To Single-phase Bridge Inverters

Repetitive control,as an advanced control technique,can be used to track periodic signals and reject periodic disturbances.It has the advantages of simple control structure and ease of application.Therefore,it is widely used to track period signals.Repetitive control is often used in disk drives,uninterruptible power supplies(UPS),grid-connected inverters,and active power filtering(APF),and so on.Repetitive control is widely used in inverters.Therefore,it is of great significance to research and improve the performances of the existing repetitive control.Great contributions have been achieved in the aspects of repetitive control,however,the following terms can be improved:(1).Better control performances can be obtained by improving the existing phase lead repetitive control;(2).How to improve the performances of high-order repetitive controlled system.In this paper,the new phase lead method for repetitive control system is introduced;how to improve the performance of second-order repetitive control system is also studied.The specific research contents are as follows:Firstly,the following contexts are introduced in this paper: the theory of repetitive control and high-order repetitive control;a method of degrading the order of infinite-order repetitive control;the common control structure of repetitive control system;the stability analysis of repetitive control system;the importance of phase compensation in repetitive control system;the reason of the poor steady-state performance of repetitive control caused by signal period variation is analyzed;the frequency-adaptive repetitive control in the literatures reported up to now is also introduced.Secondly,phase compensation methods in repetitive control system are given,the advantages and disadvantages are explained.An approximate phase compensation method for repetitive control is proposed,the compensator is consisted of a linear combination of two different linear phase lead filter.It can better fit the inverse curve of the plant model compared with the linear phase compensator.Hence,the approximate phase compensator can not only enhance the repetitive control system stability,but also can improve system steady-state and transient performances.The stability condition of the approximate phase cancellation repetitive control system is analyzed in detail.The gain of repetitive control and the parameters of the approximate phase lead compensator are solved by optimization method.In this paper,the approximate phase compensation repetitive control is applied to a pulse-width modulation(PWM)constant-voltage constant-frequency(CVCF)inverter.How to design repetitive control system is given.Simulation and experimental results not only illustrate the effectiveness of the proposed phase compensation method,but also show the superiority compared with the linear phase lead method.Thirdly,phase compensation methods in higher order repetitive control(HORC)system are researched,and the deficiency of the present commonly used phase compensation method is analyzed.Compared with phase compensation repetitive control,more parameters are designed in HORC system.Trial-and-error method that is often used in repetitive control system is not suitable for HORC system.Then,an approximate phase compensation second-order repetitive control is presented in this paper.The compensator is consisted of two different linear phase lead compensator.System stability of the approximate phase compensation second-order repetitive control is analyzed and studied in detail.Optimization method is applied to solve parameters.Simulations and experiments of the approximate phase compensation second-order repetitive control for a PWM CVCF inverter are done.The results show that the approximate phase compensation second-order repetitive control can improve system stability,transient and steady-state performances compared with linear phase lead second-order repetitive control.A linear phase lead second-order repetitive control is applied to a grid-connected inverter to improve the power quality of inverter output current due to its characteristic of rejecting intermediate frequency disturbances in this paper.Parameters of the linear phase lead second-order repetitive control system are obtained by optimization design method,simulations and experiments illustrate the effectiveness of the method and the superiority compared with conventional repetitive control.Finally,the relationship between second-order repetitive control and proportional-integral/inertial,multi-resonant multi-quasi-resonant control is firstly introduced.The weight range of second-order repetitive control is then unveiled under frequency variation.A compound control method that is consisted of a second-order repetitive control and positive proportional controller is introduced to enhance system transient and steady-state performances.Simulations and experiments in a single grid-connected PWM inverter are done.The results show the effectiveness and superiority of the proposed method.