Development of a Methodology for Evaluating the Operating Range of Line-Commutated Converter(LCC) HVDC Systems

This paper proposes a comprehensive methodology for assessing the secure operating region of LCC(Line-commutated Converter) HVDC installations that are increasingly being deployed in the Korean power system. We define and specify criteria for four factors that must be considered in both planning and operation: Short Circuit Ratio (SCR), Fundamental-Frequency Temporary Overvoltage (FFTOV), Unit Interaction Factor (UIF), and overall power-system reliability. Using an AC network model interconnected with a 3-GW HVDC link, we evaluate the admissible operating range for each criterion under contingencies, and then synthesize the individual results to derive a common secure operating region. The criterion thresholds are set to SCR ＞ 3, FFTOV ＜ 1.35 pu, UIF ＜ 0.1, and compliance with the national “Criteria for Maintaining Power System Reliability and Power Quality.” The proposed methodology provides practical guidance for both planning by supporting grid reinforcement decisions and operation by enabling the development of effective dispatch and operating strategies under diverse grid conditions.