Novel modulated equivalent model of point-to-point LCC-based high voltage AC/DC/AC system for geomagnetic storm-induced unbalanced harmonic studies

•This work represents the first systematic study of harmonic disturbances for AC/DC interconnected system under GMD.•A novel complete equivalent time-variant model is proposed for wide ranges of harmonics.•The impact of the commutation overlap angle has been studied thoroughly.•The toolbox facilitates rapid and timely high-fidelity mitigation planning in the future event of GMD.