Impact Analysis of Transmission Congestion on Power System Flexibility in Korea

This study proposes a method to evaluate the impact of transmission congestion on the flexibility of a power system, based on the ramping capability shortage expectation (RSE). Here, flexibility refers to the ability to retain a power balance in response to changes in the net load. The flexibility issue arises due to the extensive integration of renewable energy resources; specifically, the higher the degree of integration, and the greater the variability and uncertainty in the power system. Flexibility is further limited by the net transfer capacity (NTC) of transmission lines. Here, we propose a method capable of capturing the extent to which transmission congestion affects the power system, to identify transmission reinforcement options for improved flexibility. In Korea, transmission congestion occurs frequently in regions to the north and southeast. A case study for a Korean power system in 2030 was conducted. Simulation results showed that the impact of transmission reinforcement in flexibility tends to be proportional to the NTC and is greater when the penetration level is low.