JIITA, vol.9 no.2, p.1090-1097, DOI: 10.22664/ISITA.2025.9.2.1090
Nam-Gi Park, Jae-In Lee, Seok-Ju Lee, Minh-Chau Dinh
Abstract. In medium voltage direct current (MVDC) distribution networks, distribution lines are relatively short and are often modeled using lumped parameter representations for computational efficiency. However, these models fail to accurately capture traveling wave phenomena, leading to inaccuracies in fault analysis and protective relay coordination. While distributed parameter models provide improved accuracy, they require substantial computational resources. Therefore, an efficient frequency-dependent DC line model is essential to balance accuracy and computational efficiency. This paper presents the design of a frequency-dependent DC line model for transient simulations of MVDC distribution networks. The study considers the ±18.7 kV MVDC distribution network connected to a 22.9 kV AC distribution network, modeled using PSCAD/EMTDC. The frequency-dependent DC line model is developed by analyzing the frequency response of the distributed parameter model and approximating its impedance using rational function approximation. The resulting impedance characteristics are fitted to an RL network, which is then implemented in RTDS for real-time simulation. To validate the model, transient simulations were conducted to compare the frequency-dependent DC line model with the distributed parameter line model. The results demonstrate that the proposed model accurately replicates fault current characteristics and voltage behavior, ensuring its effectiveness in transient analysis. These findings provide a fundamental basis for the transient simulation of MVDC distribution networks, contributing to improved fault analysis and system protection strategies.
Keywords; MVDC; distribution networks; frequency-response