Improvement of transient response of a grid-connected inverter applying estimated disturbance rejection

This paper presents disturbance rejection control algorithm at stationary reference frame for a grid connected inverter (GCI) to reduce peak current during transient when grid fault occurs. The proposed control algorithm includes feedforward control, a grid current observer for grid voltage disturbance estimation. Also sinusoidal current vectors (α, β vectors at stationary reference frame) are controlled instead of a current vector at a synchronous reference frame. By doing this, phase estimation algorithm for grid voltage such as phase locked loop (PLL) and reference transformation can be avoided and an entire control system can be simplified. However, phase delay and steady state error are occurred by controlling sinusoidal signals. The drawbacks can be also compensated by applying the proposed algorithm. The proposed algorithm is verified via simulation and experiment.