Focusing on the complex market environment of Guangdong Province, this research pioneers a model for assimilating external power sources into the intra-provincial power market, a critical move to support the region’s high demand for electricity driven by robust economic activities. Our study innovatively tackles the province’s fluctuating power supply and demand by employing a novel power supply equivalence and co-modulation technique, enhancing system modeling efficiency and computational effectiveness. Comparative evaluations demonstrate that our approach significantly reduces the power market’s purchase costs by 15% while safeguarding power supply stability and security. The proposed model presents a breakthrough in optimizing Guangdong’s power market’s economic and reliability aspects, offering a promising pathway for future market clearing practices.