This paper proposes the lifetime extension of DC-link capacitors in three-level inverters based on the neutral-point (NP) current. High-capacity inverters require large-size capacitors to maintain robust DC-link voltage. The proposed method suppresses the ripple current of the DC-link capacitors by replacing the switching states, which are optimized for two specific modulation index regions in the linear modulation range. The reliability of the DC-link capacitors is analyzed using a capacitor lifetime model. The validation of the proposed method is supported by simulation and experimental results across various conditions.
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT), the Korea Institute of Energy Technology Evaluation and Planning (KETEP), and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. RS-2024-00333208, No. 20225500000110).
