G. R. Štrbac^a,*, O. Bošák^b, D. Štrbac^c, R. Vigi^a, M. Kubliha^b, S. Minárik^b

Chalcogenide Letters, Vol.22, No.5, pp. 481-491, 2025, DOI:10.15251/CL.2025.225.481

Abstract The temperature dependence of direct current (DC) conductivity, silver content, and the presence of crystalline phases in amorphous and annealed chalcogenides from the Ag_x(As₂(Te_0.5Se_0.5)₃)_100-x system was investigated. Amorphous samples exhibited semiconducting behavior, with conductivity increase as the silver content raised. This increase was primarily attributed to electron transitions into delocalized states from states localized near the Fermi level. Percolation behavior in conductivity was observed in the samples containing 7 at.% or more silver. For annealed samples with silver content below 9 at.%, temperature-independent DC conductivity was identified, accompanied by a decrease in conductivity as the silver More >

Qiji Dai¹, Jikai Li^2,*, Bohui Ning¹, Yutao Xu¹, Chang Liu², Xuan Zhang¹

Energy Engineering, Vol.122, No.10, pp. 4061-4080, 2025, DOI:10.32604/ee.2025.067304 - 30 September 2025

Abstract Aiming at the challenge of complex load balancing coordination for a three-phase four-leg (3P4L) based multi-ended low voltage flexible DC distribution system (M-LVDC) considering unbalanced power compensation, this paper proposes a phase-split power decoupling unbalanced compensation strategy based load balancing strategy for 3P4L based M-LVDC. Firstly, the topology and operation principle of the 3P4L-based M-LVDC system is introduced, and quasi-proportional resonant (QPR) based phase-split power current control for the 3P4L converter is proposed. Secondly, a load-balancing control strategy considering unbalanced compensation for 3P4L-based M-LVDC is presented, in which the control diagrams for each 3P4L-based converter… More >

Weibing Xu¹, Bo Yao^2,*, Xiangjun Quan³, Xunyou Zhang¹, Ning Zou², Shuo Liu², Jia Wang⁴, Jiansuo Zhang⁴

Energy Engineering, Vol.122, No.10, pp. 4225-4243, 2025, DOI:10.32604/ee.2025.066738 - 30 September 2025

Abstract The integration of large-scale new energy and high-capacity DC transmission leads to a reduction in system inertia. Grid-forming renewable energy sources (GF-RES) has a significant improvement effect on system inertia. Commutation failure faults may cause a short-term reactive power surplus at the sending end and trigger transient overvoltage, threatening the safe and stable operation of the power grid. However, there is a lack of research on the calculation method of transient overvoltage caused by commutation failure in high-voltage DC transmission systems with grid-forming renewable energy sources integration. Based on the existing equivalent model of high-voltage… More >

Danijel Pavković^*, Pietro Kristović, Mihael Cipek, Dragutin Lisjak

Energy Engineering, Vol.122, No.5, pp. 1669-1696, 2025, DOI:10.32604/ee.2025.061916 - 25 April 2025

Abstract In deep drilling applications, such as those for geothermal energy, there are many challenges, such as those related to efficient operation of the drilling fluid (mud) pumping system. Legacy drilling rigs often use paired, parallel-connected independent-excitation direct-current (DC) motors for mud pumps, that are supplied by a single power converter. This configuration results in electrical power imbalance, thus reducing its efficiency. This paper investigates this power imbalance issue in such legacy DC mud pump drive systems and offers an innovative solution in the form of a closed-loop control system for electrical load balancing. The paper… More > Graphic Abstract

Ziwen Cai^1,2, Yun Zhao^1,2, Zongyi Wang^1,2, Tonghe Wang^3,*, Yunfeng Li^1,2, Hao Wang³

Energy Engineering, Vol.122, No.4, pp. 1221-1248, 2025, DOI:10.32604/ee.2025.061452 - 31 March 2025

Abstract With the severe challenges brought by global climate change, exploring and developing clean and renewable energy systems to upgrade the energy structure has become an inevitable trend in related research. The comprehensive park systems integrated with photovoltaic, energy storage, direct current, and flexible loads (PEDF) is able to play an important role in promoting energy transformation and achieving sustainable development. In order to fully understand the advantages of PEDF parks in energy conservation and carbon reduction, this paper summarizes existing studies and prospects future research directions on the low-carbon operation of the PEDF park. This… More >

Shuo Zhang^1,2, Guibin Zou^1,*

Energy Engineering, Vol.122, No.1, pp. 85-99, 2025, DOI:10.32604/ee.2024.057452 - 27 December 2024

Abstract The multi-terminal direct current (DC) grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy. Both the DC circuit breaker (DCCB) and the current flow controller (CFC) are demanded to ensure the multiterminal DC grid to operates reliably and flexibly. However, since the CFC and the DCCB are all based on fully controlled semiconductor switches (e.g., insulated gate bipolar transistor, integrated gate commutated thyristor, etc.), their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses. To solve these problems, integrated equipment with… More >

Weidong Chen^1,2,*, Yun Zhao³, Xiaorui Wu^1,2, Ziwen Cai³, Min Guo^1,2, Yuxin Lu³

Energy Engineering, Vol.121, No.10, pp. 3075-3093, 2024, DOI:10.32604/ee.2024.051404 - 11 September 2024

Abstract The integration of photovoltaic, energy storage, direct current, and flexible load (PEDF) technologies in building power systems is an important means to address the energy crisis and promote the development of green buildings. The friendly interaction between the PEDF systems and the power grid can promote the utilization of renewable energy and enhance the stability of the power grid. For this purpose, this work introduces a framework of multiple incentive mechanisms for a PEDF park, a building energy system that implements PEDF technologies. The incentive mechanisms proposed in this paper include both economic and noneconomic… More >

Shan Liu¹, Chengbin Chi¹, Fengze Han², Yanan Wu¹, Lin Zhu¹, Tuo Wang^2,*

Energy Engineering, Vol.121, No.8, pp. 2257-2273, 2024, DOI:10.32604/ee.2024.049861 - 19 July 2024

Abstract Voltage source converter based high voltage direct current (VSC-HVDC) can participate in voltage regulation by flexible control to help maintain the voltage stability of the power grid. In order to quantitatively evaluate its influence on the voltage interaction between VSC-HVDC and line commutated converter based high voltage direct current (LCC-HVDC), this paper proposes a hybrid multi-infeed interaction factor (HMIIF) calculation method considering the voltage regulation control characteristics of VSC-HVDC. Firstly, for a hybrid multi-infeed high voltage direct current system, an additional equivalent operating admittance matrix is constructed to characterize HVDC equipment characteristics under small disturbance.… More >

Yinkong Wei^1,2, Mucong Wu^1,2,*, Wei Wei³, Paulo R. F. Rocha⁴, Ziyi Cheng^1,2, Weifang Yao⁵

Computer Systems Science and Engineering, Vol.48, No.3, pp. 723-738, 2024, DOI:10.32604/csse.2023.036062 - 20 May 2024

Abstract Ultra-high voltage (UHV) transmission lines are an important part of China’s power grid and are often surrounded by a complex electromagnetic environment. The ground total electric field is considered a main electromagnetic environment indicator of UHV transmission lines and is currently employed for reliable long-term operation of the power grid. Yet, the accurate prediction of the ground total electric field remains a technical challenge. In this work, we collected the total electric field data from the Ningdong-Zhejiang ±800 kV UHVDC transmission project, as of the Ling Shao line, and perform an outlier analysis of the More >

Siwei Han^1,*, Xianglong Li², Wei Zhao¹, Linyu Wang¹, Anqi Liang², Shuang Zeng²

Energy Engineering, Vol.120, No.6, pp. 1421-1444, 2023, DOI:10.32604/ee.2023.027094 - 03 April 2023

Abstract Photovoltaics, energy storage, direct current and flexibility (PEDF) are important pillars of achievement on the path to manufacturing nearly zero energy buildings (NZEBs). HVAC systems, which are an important part of public buildings, play a key role in adapting to PDEF systems. This research studied the basic principles and operational control strategies of a DC inverter heat pump using a DC distribution network with the aim of contributing to the development and application of small DC distribution systems. Along with the characteristics of a DC distribution network and different operating conditions, a DC inverter heat… More >