Research On Full-order Sliding Mode Control Method Of LCL Filtered Grid- Connected Inverter

With the rapid development of society,energy is increasingly depleted and environmental problems are becoming increasingly severe.The development and utilization of renewable energy has become an inevitable choice for countries in the world.Due to its environmentally friendly nature,wind energy has evolved into one of the fastest growing renewable energy sources.In order to deliver higher power quality to users,grid-connected inverters are necessary connection devices for wind power generation systems and traditional power grids,and their research in related fields is very valuable.This paper takes the LCL filter and grid-connected inverter system as the research object,designs a brand-new full-scale sliding mode control strategy,overcomes the uncertainty in the system,and realizes the stable operation of the inverter system.The paper first studies the full-order sliding mode control algorithm for input uncertain systems.For conventional controllers,only the uncertainty that satisfies the matching conditions can be eliminated,but the problem that mismatch uncertainties are difficult to overcome.In this paper,the virtual control method is used to establish the reference of the state of the system.Then the full-order sliding mode control algorithm is designed to eliminate the influence of the uncertainty and the system state converges to the area near the equilibrium point within a limited time.The validity of the algorithm is verified by simulation,which lays the foundation for the subsequent research in this paper.Then,the switching average model of the LCL grid-connected inverter controlled in the three-phase stationary coordinate system is deduced.Taking into account the changes in the inductance,capacitance and capacitance of the grid-connected inverter,a mathematical model for the LCL grid-connected inverter in the ?-? coordinate system is established.The controller simulation results show that the designed controller has higher control accuracy and faster response than the PI controller.In order to further verify the applicability of the method,the mathematical model of the LCL grid-connected inverter in the d-q coordinate system is established.The fullorder sliding mode algorithm was applied to the LCL grid-connected inverter system.By designing the full-order sliding surface,the grid-connected current converged within a limited time and reached the equilibrium point.The controller simulation results show that the designed controller has higher control accuracy and faster response than the PI controller.Finally,this paper analyzes several possible uncertainties in the power grid.The simulations verify that when When there are uncertainties in the grid,the proposed fullorder sliding mode control strategy can achieve stable DC bus voltage and meet grid connection requirements.Compared with PI controllers,the system is robust to both external disturbances and parameter perturbations.In particular,the full-order sliding mode control strategy shows better performance for parametric perturbations that do not satisfy the matching conditions.