Research On Photovoltaic Inverter With Fuzzy-Repetitive Control

With the development of the global economy,the harsh ecological environment caused by the increasingly consumed traditional fossil energy sources poses a severe challenge to the world.The existing energy structure is bound to undergo major changes in search of a clean,efficient and sustainable low-carbon Energy which has become an urgent problem today and an inevitable choice for the sustainable development of society.Large of solar energy has aroused widespread concern of experts and scholars,photovoltaic power generation has also been vigorously promoted.Inverter is the core component of photovoltaic system,therefore,how to propose an effective control method to improve the stability of the inverter and then improve the quality of the output waveform of the inverter is an important research issue nowadays.In this thesis,the mathematical models of single-phase and three-phase photovoltaic inverters are built,and the main factors that affect the photovoltaic inverters are deeply analyzed.According to the shortcomings of existing compensation measures,it is pointed out that it is the whole research foundation to realize the system output waveform tracking control through a reasonable control method.For the first time,this thesis proposes to use the output signal of state observer instead of output signal of the system to track the periodic reference input,and to design the repetitive controller based on continuous-discrete two-dimensional hybrid model and singular value decomposition technique.By means of Lyapunov functional analysis,a set of sufficient conditions for the stability of the system are obtained,then it is generalized to the design of repetitive controllers with uncertainties.Numerical examples show the effectiveness of the proposed method and are applied to the photovoltaic inverter model.Aiming at the existence of inaccurate parameters and disturbances in PV inverters,this thesis firstly introduces T-S fuzzy model into the uncertain nonlinear system which based on state observer and improved iterative control method to eliminate the periodic disturbance in the inverter system and track the reference input signal of the system without static error.By using Lyapunov function,the stability condition of the nonlinear system based on linear matrix inequality is obtained.The numerical example shows that the performance of the system under this method is better than that of the single repetitive control method.The fuzzy-repetitive control method is applied to the mathematical model of the photovoltaic inverter and simulated by MATLAB software.The research proves that the fuzzy-repeated compound control method improves the stability of the system and improves the output waveform of the inverter.