A hybrid controlling method for stability controllers is needed in the interconnected renewable power systems due to the working conditions being diverse from low to high levels of Renewable Energy Sources (RES). Power System Stabilizer and Virtual Inertia (PSS-VI) are viable to provide a wider enhancement effect in the stability. This paper proposes a new approach to enhance the stability of interconnected renewable power systems by hybrid controlling parameters of PSS-VI. A robust optimizer based on Harris Hawk Optimizer (HHO) was established. Interconnected renewable power systems are modeled based on multi-area power systems with different energy resources, including conventional generators, Solar Power Generation (SPG), and Wind Power Generation (WPG). Besides that, the Battery Storage System (BSS) is also dispatched to realize the virtual inertia emulation. The optimal parameters by HHO are compared with the other recent novel algorithms. The optimal controlling parameters of PSS-VI by HHO in interconnected renewable power systems performed in low to high RES conditions. HHO can offer the best fitness value in faster iterations than the compared algorithms. The results of hybrid controlling parameters by HHO can significantly suppress the Rate of Change of Frequency (RoCoF) by 5.99% and 4.89% in low-RES and high-RES conditions, respectively. Moreover, the hybrid controlling parameters for PSS-VI offer smoother response and transition in frequency and interarea power exchange responses.INDEX TERMS harris hawk optimizer, interconnected power system, power system stabilizer, renewable