Award type：Honored in official journal of a scientific society, scientific journal 

Award type：Honored in official journal of a scientific society, scientific journal 

Award type：Honored in official journal of a scientific society, scientific journal 

Award type：Honored in official journal of a scientific society, scientific journal 

Award type：Honored in official journal of a scientific society, scientific journal 

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

In multi-terminal DC (MTDC) systems, converter outages require immediate active power reallocation among healthy converters to maintain the stability of interconnected AC grids. While previous studies mainly focused on control strategies for DC power flow, the economic implications for AC systems including operational costs and frequency stability impacts remain insufficiently addressed. This study proposes an optimization framework to simultaneously minimize the total adjustment cost and frequency deviation by determining optimal active power reallocation among converter stations. The proposed model incorporates multiple types of balancing reserves characterized by distinct cost structures and activation conditions. A four-terminal bipolar VSC-MTDC system is simulated during a converter trip scenario, and the impact of active power reallocation is evaluated in terms of system stability and adjustment cost. By varying the cost-weighting factor, a Pareto front is obtained with three representative operating points: cost-minimization, compromise, and frequency-minimization cases, yielding total adjustment costs of 5.524-5.973 million JPY and cumulative frequency deviations across all interconnected AC systems of 10.125-10.884 Hz. Compared with a baseline scenario without optimization, the proposed framework achieves 20.7-26.7% cost reduction and 26.1-31.3% frequency improvement. The results show that the system operator can select the operation point of the MTDC system based on the specific priorities and system conditions.

DOI： 10.1109/ACCESS.2026.3673411

Open Access

Web of Science

Scopus

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Plasma Physics and Technology  

Direct current (DC) facilities are increasing with the spread of renewable energy such as photovoltaic power generation. DC series arc may occur in poor contact or disconnecting in the facilities and cause fire incidents. This paper presents DC series arc generation experiments in air considering actual failure conditions, and Wavelet transformation analysis of the measured current waveform. Using the obtained results, a method of detection of arc generation in low-voltage DC facilities is proposed.

DOI： 10.14311/ppt.2025.1.34

Open Access

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Asia Pacific Power and Energy Engineering Conference Appeec  

This paper investigates optimal power redistribution in a bipolar voltage source converter based multi-terminal DC (VSC-MTDC) system under a converter trip. A mathematical optimization framework is developed to minimize both operational costs and frequency deviations in the interconnected AC grids. The model incorporates multiple types of balancing resources, including contract-based reserves, market-based reserves, and local converter adjustments, each with distinct cost and capacity limits. Converter trip events are modeled using redistribution coefficients ωter,im, and power assurance coefficients ωass,i , enabling flexible allocation of surplus or deficit power among remaining converter stations. All monetary values in this study are expressed in JPY. Simulation results demonstrate that, for representative operating points, the total adjustment cost can be reduced from 21.166 million JPY at a frequency-minimization case to 18.438 million JPY at a cost-minimization case, while maintaining AC frequency deviations. Specifically, the frequency-minimization case reduces the maximum frequency deviation from 14.9545 Hz to 8.9500 Hz. These results indicate that the method provides a reliable and economically efficient approach for MTDC system.

DOI： 10.1109/APPEEC66370.2025.11382071

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

In a bipolar voltage source converter-based multi-terminal DC (VSC-MTDC) system, the power flow of the positive and negative pole networks can be controlled independently. This advantage allows bipolar systems to maintain operation with only the healthy pole even in the event of DC faults. However, existing power flow control methods for bipolar systems do not include the optimal mode-switching of each converter’s operation and may not be sufficiently reliable during fault conditions. Thus, this paper proposes a new control scheme considering coordination between the poles and flexibility in power shifting. The proposed method consists of two steps: (a) a mode-switching method of converters to maintain DC voltage stability during converter trips and (b) an active power dispatch control method to enable power shifting from the faulty pole to the healthy pole, mitigating the risk of power surplus and ensuring a robust response to AC grid stability issues. The power assurance coefficient ω ^m<inf>ass,i</inf> is defined as critical factor for determining the interpolar power dispatch. The simulation results show that an average transmission power outage of approximately 220 MW can be prevented during a single-pole trip while maintaining the operation within the rated VSC capacity when ω ^m<inf>ass,i</inf> is set to 0.5. This highlights the effectiveness of the proposed method in maintaining the system reliability and stability. Overall, the proposed method enhances the transmission capability by maintaining the operation within the rated capacity, enabling interpolar power shifting, and mitigating the AC grid instability during fault conditions regardless of the bipolar configuration.

DOI： 10.1109/ACCESS.2025.3542740

Open Access

Web of Science

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Proceedings of the 2024 International Conference on Sustainable Energy Energy Transition and Net Zero Climate Future Icue 2024  

Due to the advantage of the system operation reliability and flexibility, the bipolar multi-terminal high voltage dc (MTDC) transmission has attracted worldwide attention for the integration of offshore windfarms. However, majority of existing operation methods and dc power flow algorithms are designed to control the monopolar MTDC system. It is difficult to implement the conventional control method for the monopolar system into the bipolar system due to the difference in the characteristics of dc power flow control scheme between the two configurations. Therefore, this paper proposes an operation method of the bipolar MTDC system composed of the dc power flow control scheme and mode-switching method. As a simulation result, the proposed method can realize the power sharing between each VSC and reduce the impact of the active power fluctuation on the AC grid connected to the system even when the single-pole trip occurs in the bipolar MTDC system.

DOI： 10.1109/ICUE63019.2024.10795532

Scopus