Application Research Of Linear Active Disturbance Rejection Controller In LCL Grid-Connected Inverter System

With the energy shortage and environmental pollution getting worse,solar-based renewable energy power generation technology has matured,providing a new way to solve energy and environmental problems.As an interface between distributed power supply and common power grid,grid-connected inverters have received more and more attention.L-type filter have problems such as high hardware cost,excessive volume and weight,and slow current dynamic response.In order to improve the response speed and reduce the cost of the system,LCL filter is used to replace the traditional L-type filter.However,LCL filters have inherent resonance and coupling problems.Additional resonance suppression and decoupling algorithms are needed to improve the system performance,which makes the controller more difficult to design.Linear Active Disturbance Rejection Control(LADRC)can not only make the stable operation of the system,but also realize the LCL filter resonance suppression and current loop(9 component decoupling.The algorithm is simple and does not require additional hardware cost.It improves the system performance and simplifies the controller design,which has important research value.According to the mathematical model of LCL grid-connected inverter in two-phase rotating dq coordinate system,a fourth-order LADRC is designed and the corresponding equivalent transfer function is given.The traditional bandwidth parameter tuning method reduces the degree of freedom of controller parameter selection and limits the control effect of high-order systems.Therefore,this paper proposes a new parameter tuning method,based on the traditional parameter parameter tuning method,a set of optimal parameters are selected under the condition of ensuring the stability of the system,take the controller parameters set by this method into the system,obtained the specific equivalent transfer function of the system,the parameter robustness and disturbance rejection performance of the LADRC are analyzed.In addition,in order to solve the problem of excessive harmonic current and the spike pulse of current on the grid-side when the LADRC enters,using low-pass filter based on backward differential and main coupling variables feedforward decoupling are adopted to suppress and solve the problem respectively.In order to verify the control performance of LADRC in the actual LCL grid-connected inverter system,an experimental platform with DSP + CPLD as the control core is designed and the corresponding experiments are carried out.The experimental results show that the gridside current of the LCL grid-connected inverters with linear ADRC controller has good steadystate and dynamic performance,achieved completely decoupling of the current loop,and has strong robustness to the parameter variation of the filter.