Output feedback tracking control of LCL-type inverter system based on state and disturbance observers method

A single-phase LCL-type inverter has been widely used in industrial grid connection applications. This paper studies the output tracking control problem for this type of inverter system with unknown state variables and external disturbance. Firstly, the system’s mathematical model is established by using Kirchhoff’s voltage/current law. And the model is transformed into a Brunovsky state space form by choosing appropriate state variables. Based on the characteristics of the state space equations, a Levant differentiator state observer is designed to estimate the unknown state variables within finite time. Next, a high gain disturbance observer is constructed to estimate the unknown external disturbance. Subsequently, an output feedback robust tracking controller is designed using the sliding mode control technique, the estimated values of the state variables and disturbance. The presented controller can eliminate the influence of disturbance and enables the inverter system to quickly track the desired trajectory. The numerical simulation experimental results verify the effectiveness and superiority of our developed method.