Research On Improved Linear Active Disturbance Rejection Control Based On LCL Type Grid-Connected Inverter

With the continuous promotion of "double carbon" target,renewable energy will gradually replace traditional fossil energy to occupy the dominant position in the energy field,distributed power generation system is the ideal way to make full use of renewable energy,but the distributed power supply cannot be directly connected to the grid and needs to meet the corresponding power quality requirements.The LCL-type gridconnected inverter studied in this paper plays a crucial role as an intermediate link between the distributed power supply and the grid,and its output is directly related to the power quality of the grid current.In order to reduce the harmonic content of the network-side current,the space vector pulse width modulation(SVPWM)method is used and improved.The traditional space vector pulse width modulation technique is a seven-segment type,and later researchers developed a five-segment type,and this paper improves on the path of the five-segment type.Improved five-segment type has a better three-phase symmetry compared to the traditional five-segment type,while each sector change is fixed one switch work,compared to more uniform heat dissipation.Compared with the sevensegment type,the number of switches operated per cycle is less and the life span is longer,which is more conducive to engineering applications.In this paper,firstly,the LCL grid-connected inverter is modeled and analyzed,and the mathematical model is obtained under two identical step rotation coordinate systems.From the model,the system is a nonlinear,strongly coupled system,and the application of traditional PI control cannot handle its coupling quantity,in view of this situation,the linear active disturbance rejection control(LADRC)is introduced.The LADRC does not rely too much on the mathematical model and has a strong immunity to harmonic resonance and coupling at the same time.The third-order linear self-turbulence controller is designed for LCL-type grid-connected inverter,and the steady-state,dynamic and immunity performance are analyzed.Finally,to address the above-mentioned problems of traditional LADRC,the text proposes a control method of reduced-order LADRC,using the inverter-side current as the output to achieve the reduced-order processing of the controller,which simplifies the controller structure and makes it easier to adjust the parameters at the same time.Through simulation,it is verified that there is a significant improvement relative to the traditional linear self-immunity while meeting the output current harmonic quality requirements.