Research On An Intelligent Off-Grid Inverter Control Strategy

With the development of national economy,the status of micro-grid becomes more and more important.According to different application conditions,micro-grid can be divided into two working modes:off-grid and grid-connected.Inverter is an important link between micro-grid and active load or passive load,which plays a vital role in system output performance and stability.This subject mainly analyzes and studies one of the application conditions of the inverter(off-grid working mode),analyzes and compares common control strategies,and designs intelligent control strategies.In order to control the off-grid inverter accurately,firstly,the mathematical modeling of the off-grid inverter is analyzed and deduced in detail in several commonly used coordinate systems(ABC coordinate system,α-β coordinate system and d-q coordinate system),and the more commonly used SVPWM modulation method is studied.Then the basic theory of repetitive control is introduced.At the same time,the repetitive controller is designed in detail from several aspects such as the repetitive control delay link,the repetitive control compensation link,the final repetitive control stability and the factors that affect the system stability.But when the model mismatch difference is relatively large,the repetitive controller cannot adjust its related parameters in real time,which reduces its final control effect.Based on the above-mentioned repetitive control problems and the advantages of the immune algorithm,the immune algorithm is added to the designed repetitive controller to realize the real-time control of the repetitive controller.Next,the regulation mechanism of the immune system is analyzed in detail,the realization process of the immune algorithm is designed,and the immune algorithm is combined with the repetitive control to design an intelligent controller that can be applied to the off-grid inverter.Finally,PSIM(simulation application package software in the field of power electronics and motor control)and an off-grid inverter with TMS320F28335 as the control chip are used to verify several control strategies of off-grid inverters.Mainly compare and verify its steady-state performance and dynamic performance under different working conditions.The simulation and experimental results show that,compared with the traditional PI controller,the repetitive control inverter has a better control effect under linear load and non-linear load.And compared with repetitive control inverters,intelligent control has better dynamic and steady-state performance under linear and non-linear loads.