Sensorless Active Damping Control for Three-Phase LCL Grid-Tied Converters With State-Estimation of Grid Voltage and Capacitor Current

LCL filters have been widely used between grids and inverters due to their excellent filtering performance and low cost. However, in order to ensure the stability of the system, the traditional damping control scheme usually requires a large number of sensors which makes extra cost. In order to solve this malpractice, a model reference based active damping control strategy is proposed for a three-phase LCL-type grid-tied inverter, which is able to stabilize the system, and accurately control the active and reactive power with only the inverter-side current sensor. Instantaneous power theory is used to estimate the capacitor current and the grid voltage. Simulation results verify the feasibility of this scheme.