Observer-based Voltage Sensorless Control Scheme for an LCL-filtered Grid-connected Inverter

To synchronize the distributed generation (DG) unit with the grid, the voltage sensors are generally employed to obtain the grid phase angle. This paper presents an observer-based voltage sensorless control scheme for a three-phase inverter connected to the grid through an LCL filter. The proposed control scheme consists of an augmented state observer and a feedback controller. The augmented state observer is used to estimate the grid voltages and states of the inverter system, which are then employed to determine the grid voltage angle and to construct the feedback controller. As a result of using the observer, only the grid current sensors are required to accomplish the control scheme. The simulation results are given to prove the validity of the proposed control scheme.