An Iterative Current Harmonic Suppression Algorithm for Single-Phase Distorted Grid Applications

The distorted grid voltage in the distribution system induces lower order harmonics in the current sourced from the Single-phase Grid-connected Inverter (SGI). Non-idealities of the SGI also contribute to the current distortion. This paper presents a novel iterative algorithm for the SGI which suppresses current harmonics due to both the grid-side and inverter-side distortions. The mathematical basis of the method is derived in this paper. The iterative algorithm is developed ensuring a computationally light implementation in modern digital microcontrollers. The proposed algorithm is verified in simulation under practical grid conditions like in a Low Voltage Distribution System (LVDS). Further experimental verifications were performed on a 1.1 kW laboratory prototype of an SGI with inverter-side distortion connected to distorted grid. Different lower order harmonics were separately suppressed under predefined thresholds. The measured total harmonic distortion in the current was improved from 22.24 % to 2.73 % at rated power.