Multi resonant Component-Based Grid-Voltage-Weighted Feedforward Scheme for Grid-Connected Inverter to Suppress the Injected Grid Current Harmonics Under Weak Grid

Abstract

The grid voltage full feedforward scheme is an effective method to improve the injected grid current quality of the grid-connected inverter. However, due to the digital control delay, the suppression of the injected grid current harmonics is weakened, and the inverter output impedance has an additional negative phase shift, which deteriorates the system stability under weak grid. In this article, a multi resonant component-based grid-voltage-weighted feedforward scheme is proposed, which introduces a series of quasi-resonant components into the grid voltage full feedforward path so that only the background harmonics in the grid voltage are fed forward. By properly designing the quasi-resonant components, the phase lag due to the digital control delay is compensated and the feedforward weights at different harmonic frequencies are introduced in the grid voltage feedforward path. Thus, the suppression of the injected grid current harmonics and the system stability is improved. The experimental results from a 6-kVA prototype are provided to verify the effectiveness of the proposed grid-voltage-weighted feedforward scheme.