Cost-optimal operation strategy for integrating large scale of renewable energy in China's power system: From a multi-regional perspective

High renewable energy penetration is an effective way to decarbonize the power system. However, many studies focus on the economics of integrating renewables at the generation-side rather than system-wide. This paper aims to explore the cost-optimal operation strategies of a renewable-dominant power system. Considering both cost reduction potential of energy storage technology and regional investment cost variance of ultra-high voltage direct current grids, an hourly-resolution, multi-region model with total system costs minimized is proposed. Moreover, energy storage-based, ultra-high voltage direct current-based, and mixed scenarios are taken into consideration to investigate the economics of high renewables penetration. The results show that energy storage technology can achieve maximum penetration of renewable energy at 85.8% while the total system cost is 11.8% higher than that of ultra-high voltage direct current transmission technology. Although ultra-high voltage direct current grid is the most economical option to integrate renewables, the penetration is 13 percentage points lower than that of energy storage technology. The combination of energy storage technology and ultra-high voltage direct current grid can achieve 74.2% renewable energy penetration, saving 9.4% of total system costs compared to that of energy storage technology only. The cost-optimal option for East and South China is to promote both energy storage and ultra-high voltage direct current technologies. Energy storage technology is preferred among North, Northwest and Northeast China, while ultra-high voltage direct current grid is the optimal option for Center China.