Research On Fuzzy-Repetitive Control And Fault Detection Method For Microgrid Inverter

As the scale of clean renewable energy generation such as photovoltaics,wind energy and tidal energy continues to increase,new energy distributed generation(DG)technology is becoming more and more important.As an important carrier carrying distributed power generation technology,microgrid is an important part of distributed power generation technology in the future.As an important part of the microgrid grid-connected and island operation mode,the voltage source inverter affects the stability and power quality of the microgrid system operation directly,so it is very important for the research of the microgrid inverter.Aiming at the high nonlinearity,modeling and control difficulties of voltage source inverters,we propose a fuzzy system modeling control and analysis method,and propose a fuzzy-repetitive control and event-triggered fault detection design method.We got good results.The main work of the thesis is as follows:Firstly,the state space model of the microgrid voltage source inverter is studied and constructed.The voltage source inverter is mainly divided into four parts:a voltage source controller,a current source controller,a power controller,and an LC filter.Based on the establishment of its small-signal state space model,the mathematical model of the whole inverter is constructed.The nonlinear state space model of the multi-stage parallel inverter of the whole microgrid system is further established.Lay the model foundation for follow-up research.Secondly,a fuzzy observer-based fuzzy-repetitive control method is proposed to realize the static signal tracking of the periodic signal of the inverter system.Aiming at the nonlinear characteristics of the microgrid inverter mathematical model,the T-S fuzzy rule is introduced to establish the inverter T-S fuzzy model.At the same time,considering the state of the model system is not completely measurable,a fuzzy observer-based repetitive controller is designed.Using the fuzzy Lyapunov functional,the stability conditions of nonlinear systems based on linear matrix inequalities are obtained.A new equation lemma of the fuzzy membership function derivative is proposed.By introducing the relaxation matrix condition and the augmented fuzzy matrix technique,the conservativeness of the system results is reduced and the feasible solution space of the linear matrix inequality condition is increased.In addition,by using the fuzzy Lyapunov functional method with separate parameters,the separation design between fuzzy periodic controller and fuzzy observer is realized,which improves the design flexibility.The fuzzy-repetitive control method is applied to the mathematical model of the microgrid inverter,and the simulation is carried out by MATLAB software.The results prove the effectiveness of the method and improve the output waveform of the inverter.Finally,aiming at the fault detection problem of the inverter system in the network environment,an event-triggered fault detection method is proposed to improve the accuracy of fault detection.First,a fuzzy fault detection filter for asynchronous antecedent variables is established to generate residual signals.Secondly,considering the limited network communication resources,the event trigger mechanism is introduced,and a fault detection system containing sensor faults,process faults and external disturbances is further obtained.Thirdly,the fuzzy Lyapunov functional method and some LMI techniques are used to relax the stability conditions of the fuzzy fault detection system,reduce the conservativeness of the system,obtain better fault detection performance,and finally realize the fault detection filter gain matrix.Collaborative design of the event-triggered weighting matrix.The simulation experiment in MATLAB environment verifies that the proposed fault detection method can not only detect the faults in time,but also effectively improve the utilization of communication resources.