Control of grid-connected inverter to inject sinusoidal current to grid under non-ideal conditions

In this paper a new control method is introduced for grid-connected inverter (GCI) to inject sinusoidal current to grid in presence of nonlinear load and distorted grid voltage conditions. The proposed control method consists of two parts: current reference generation and current controller. To generate current reference, a new algorithm, based on Recursive Discrete Fourier Transform, is proposed. This algorithm compared to the common techniques enjoys from lower computational burden, faster response and more accuracy. In order to track reference current, a current controller is used which is implemented in the stationary reference frame and it compensates current harmonics with only one control variable in a single loop. Simulation results indicate that proposed control method compensates current harmonics and injects sinusoidal current to the grid under all non-ideal grid voltage conditions and nonlinear load.