Repetitive Control Research Of Photovoltaic Grid-connected Inverter

As one of the most advocated green energy, photovoltaic generation industry hasencountered both its opportunities and challenges though traditional energy isdepleting. Repetitive control, which is based on internal model principle, byintroducing a periodic external excitation signal generation model in the closed-loopof control process, is capable of tracking and suppressing periodic signal with zerosteady-state error. In theoretical analysis, the traditional control strategies ofgrid-connected photovoltaic inverter system perform unsatisfied, whereas a controlstrategy of grid-connected photovoltaic inverter system based on repetitive controlleris proposed and introduced.Firstly, with an analysis of several grid-connected photovoltaic inverter systemtopologies, repetitive controller structures of grid-connected photovoltaic inverter,such as double-loop control, output feedback and state observer are established,followed by their physical model. In this process, a mathematical phenomenon thatperiodic signals could not be tracked perfectly was discovered from the perspective ofcoordinate transformation, also the significance and independence of thegrid-connected inverter in photovoltaic system are emphasized.Then with a concern of the physical model of double-loop grid-connectedphotovoltaic inverter repetitive controller, from aspect of frequency domain, theopen/closed loop transfer functions are derived. Additionally, with a help of H model, the undetermined parameters could be possibly worked out by toolbox hinfsynin matlab, based on which, a further matlab numerical simulation model was built andconsequently, the feasibility of proposed method was validated.Moreover, a new reconstructed state space function was obtained through a seriesof theoretical deduction towards grid-connected photovoltaic inverter repetitivecontroller based on state observer. The reconstructed state space was transformed intodiscrete two-dimensional model. Then the Lyapunov function was given out, whoseconservation was proved concomitantly. After all the approaches above, a matlabmathematical simulation model accordingly was built. More remarkably, aphotovoltaic solar grid-connected experimental platform based on microprocessorConcerto was established, with the application of which, the practicality of themethod was verified.Whereas in the case of grid-connected photovoltaic inverter repetitive controllerbased on output feedback, of which, a kind of multi-objectiveH2/H robust stability conditions were theoretically derived, while in this process, a differentperspective featured with linear matrix inequality (LMI) was applied. Yet in theprocess of numerical solution, several matlab toolboxes were utilized in order tosimplify the calculation procedure. Finally, the simulation result showed that theproposed repetitive control method has an excellent performance of good stability,low harmonics distortion and fast convergence.In this paper, different means of theoretical analysis and strategies are introducedfor several grid-connected photovoltaic inverter repetitive controller topologies, suchas the frequency domain analysis, open/closed loop transfer function, linear matrixinequalities (LMI), which are combined with Lyapunov methods, and robust controltheory in the modern control field. Finally, by a number of numerical simulation andphysical experiments the feasibility of the design methods was verified, whichproviding certain design ideas and meaningful reference value in the applicationdomain of repetitive controller.