Effect of grid expansion on interregional power dispatch towards carbon neutrality based on market equilibrium model

China has introduced a national interconnected power market to achieve carbon neutrality. It can effectively enhance the variable renewable energy integration by promoting power sharing mechanism. However, grid expansion to transmit more power from resource-rich regions increases the difficulty of maintaining a stable power supply. In this study, we employed a high-resolution power market equilibrium model to explore the interaction between grid expansion and interregional power dispatch to examine the impacts of grid expansion on the transmission volume, power supply, and price changes. We get several important insights from this study. First, a positive correlation exists between the transmission capacity and interregional power dispatch. Enhanced transmission line expansion increases interregional power transactions by approximately 90 %. Second, grid extension enables a broader power supply source. It has a prominent role in maintaining the power supply and enhancing renewable power absorption, especially in the case of power shortages. Third, the grid extension and interregional power transactions narrow the price gap among provinces. The economically developed provinces have experienced power price reductions of up to around 6 %, whereas local prices increase by up to around 4 % in resource-rich provinces. These results can give references for the power market design and transmission line planning, which provide valuable implications for policymakers.