Control for a single-phase inverter using a grid current observer

Presented in this paper is grid current observer-based compensation control for a single-phase grid-connected inverter that is connected to a weak grid. Traditional single-loop PI current control performance suffers in the presence of the grid voltage distortion and grid impedance uncertainty. To compensate for disturbances from the grid side, two different compensation control structures are proposed. One is a feed forward method, which uses estimated grid current as a feed forward signal. The other one is a modified disturbance observer method, which compensates for the estimated disturbance. Disturbance rejection ability can be improved by adopting disturbance compensation. Simulation and experiments have been carried out on a 1 kW single-phase grid-connected inverter and show that the proposed controller can achieve low total harmonic distortion (THD) and robustness to grid impedance variation.