Optimal Power Flow of DC-Grid Based on Improved PSO Algorithm

Xianzheng Liu,Xingcheng Wang,Jialiang Wen 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.4

Voltage sourced converter (VSC) based direct-current (DC) grid has the ability to control power flow flexibly and securely, thus it has become one of the most valid approaches in aspect of large-scale renewable power generation, oceanic island power supply and new urban grid construction. To solve the optimal power flow (OPF) problem in DC grid, an adaptive particle swarm optimization (PSO) algorithm based on fuzzy control theory is proposed in this paper, and the optimal operation considering both power loss and voltage quality is realized. Firstly, the fuzzy membership curve is used to transform two objectives into one, the fitness value of latest step is introduced as input of fuzzy controller to adjust the controlling parameters of PSO dynamically. The proposed strategy was applied in solving the power flow issue in six terminals DC grid model, and corresponding results are presented to verify the effectiveness and feasibility of proposed algorithm.

Research on the Influence Factors of Thermal Cracking in Mass Concrete by Model Experiments

Xianzheng Yu,Jianyun Chen,Qiang Xu,Zhi Zhou 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8

Thermal cracking has significant impact on the safety and durability of mass concrete. This paper aims to find the reason forcracking of a prototype bridge structure and consider which influencing factors are the most important. For this model experimentson mass concrete in bridge structures were designed and conducted and thermally cracking was induced. Fiber bragg grating sensorswere used to monitor the temperature and strain within concrete in real time, as well as the strain around the embedded cooling pipes. Thermal properties of concrete were deduced from these monitoring data and then used in the numerical analyses to verity thecalculation accuracy. In the context of engineering practice, the primary influencing factors on the cracking of mass concrete wereinvestigated by numerical analyses. The optimized temperature control methods were proposed to prevent the occurrence of thermalcracking of mass concrete.

Optimal Power Flow of DC-Grid Based on Improved PSO Algorithm

Liu, Xianzheng,Wang, Xingcheng,Wen, Jialiang The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.8 No.1

Voltage sourced converter (VSC) based direct-current (DC) grid has the ability to control power flow flexibly and securely, thus it has become one of the most valid approaches in aspect of large-scale renewable power generation, oceanic island power supply and new urban grid construction. To solve the optimal power flow (OPF) problem in DC grid, an adaptive particle swarm optimization (PSO) algorithm based on fuzzy control theory is proposed in this paper, and the optimal operation considering both power loss and voltage quality is realized. Firstly, the fuzzy membership curve is used to transform two objectives into one, the fitness value of latest step is introduced as input of fuzzy controller to adjust the controlling parameters of PSO dynamically. The proposed strategy was applied in solving the power flow issue in six terminals DC grid model, and corresponding results are presented to verify the effectiveness and feasibility of proposed algorithm.

Improved Elman Neural Network Short‑Term Residents Load Forecasting Considering Human Comfort Index

Yunjun Yu,Xianzheng Wang,Roland Bründlinger 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.6

The massive access of distributed power in distribution network increases the complexity of user’s power consumption mode. It puts higher requirements on the accuracy and stability of load forecasting. The forward neural network has limitation in dynamic performance, and the prediction accuracy needs to be improved. This paper considers the infuence of daily feature correlation factors on residential load. Then a method for improved Elman neural network short-term residential load forecasting considering human comfort index is designed. Using the human comfort index overcomes the shortcomings of low accuracy in load prediction when meteorological factor as a direct input. The Elman neural network’s incentive function is improved. The softmax function serves as an incentive function for hidden layer. Short-term load forecasting model was established for the load of Nanchang, Jiangxi, China. In order to reduce the impact of residents’ load characteristics, the samples of load are divided into weekend load, seasonal load and typical weather type load. Experiments show that the improved Elman neural network has higher prediction accuracy under three load types, compared with Elman neural network and RBF neural network.

Origin of dolomitization in the Lower Cretaceous Bayanhua Group dolomitized rocks, Bayindulan Sag, Erlian Basin

Fugui He,Xianzhi Gao,Xianzheng Zhao,Huilai Wang,Dexiang Yang,Quan Wang 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.4

The Bayindulan Sag situated in Erlian Basin, northeast China, is characterized by pervasive dolomitization in Upper A4 Member to Lower T1 Member of Bayanhua Group. These stratum in the Lower Cretaceous Bayanhua Group were deposited in a lacustrine environments. The main objective of this study is to identify the origin of dolomitization and distribution model of dolomitized rocks. Based on petrographic examination, mud-crystal dolomites (<0.03 mm), silt-crystal dolomites (0.03–0.1 mm) and fine-crystal dolomites (0.1– 0.25 mm) have been observed, and the former two types were predominant. Meanwhile, only one type of dolomite have been defined: replacive dolomite. A variety of dolomite textures have also been observed, the major ones of them are scattered, blocky, joined and annular textures. These dolomites have strongly depleted oxygen isotopic values from –17.48‰ to –6.96‰ with the average of –10.48‰ (PDB), carbon isotopic values from 0.24‰ to 8.37‰ with the average of 5.39‰ (PDB). The obvious depletion of oxygen isotopic was presented as a result of the increase in temperature with progressive burial, and the high carbon isotopic content of dolomites maybe result from the involvement of CO2 in the dolomitization process. These CO2 were generated by bio-methanation which commonly took place in moderately deep burial environments. The Sr values from 62.4 ppm to 262 ppm as well as the Sr/Ba ratios from 0.24 to 0.76 in Tengyi Formation mudstones indicate the freshwater lacustrine sedimentary environments. Taking the petrographic and geochemical data into consideration, the conclusion that the dolomites have formed in a freshwater environments during deep burial depths at temperatures of at least 60 °C can be drawn. Petrographic observations and mineralogy analyses indicate that dolomitization is closely associated with tuffaceous materials, the Mg needed for the dolomitization is provided by dissolution of tuffaceous materials and dolomitization is most probably driven by tuffaceous materials alteration at elevated temperatures.

Enhancement of mechanical and durability properties of preplaced lightweight aggregate concrete

Bo Peng,Jiantao Wang,Xianzheng Dong,Feihua Yang,Chuming Sheng,Yunpeng Liu Techno-Press 2023 Advances in concrete construction Vol.15 No.6

In this study, the effect of two types of aggregates (fly ash aggregate and shale aggregate) on the density, strength, and durability of preplaced lightweight aggregate concrete (PLWAC) was studied. The results showed that the 7 - 28 days strength of concrete prepared with fly ash aggregates (high water absorption rate) significantly increased, which could attribute to the long-term water release of fly ash aggregates by the refined pore structure. In contrast, the strength increase of concrete prepared with shale aggregates (low water absorption rate) is not apparent. Although PLWAC prepared with fly ash aggregates has a lower density and higher strength (56.8 MPa @ 1600 kg/m³), the chloride diffusion coefficient is relatively high, which could attribute to the diffusion paths established by connected porous aggregates and the negative over-curing effect. Compared to the control group, the partial replacement of fly ash aggregates (30%) with asphalt emulsion (20% solid content) coated aggregates can reduce the chloride diffusion coefficient of concrete by 53.6% while increasing the peak load obtained in a three-point bending test by 107.3%, fracture energy by 30.3% and characteristic length by 103.5%. The improvement in concrete performance could be attributed to the reduction in the water absorption rate of aggregates and increased energy absorption by polymer during crack propagation.

The Silurian−Devonian granitoids in the East Kunlun orogenic belt, northern Qinghai-Tibetan plateau, China: origin and tectonic implications

Namkha Norbu,Yuegao Liu,Jinchao Li,Qunzi Jia,Wei Wang,Xiaobing Song,Yazhi Li,Huilei Kong,Yijie Gao,Xianzheng Guo,Xuegang Yao 한국지질과학협의회 2021 Geosciences Journal Vol.25 No.6

The East Kunlun orogenic belt (EKOB) is located in the northeastern part of the Qinghai-Tibetan Plateau, China. Voluminous Silurian–Devonian granitoids were formed during the Proto-Tethys Ocean subduction and collision process. In this study, zircon U-Pb age dating, in-situ Hf isotope analyses, and whole rock major and trace element analyses have been carried out on granitoids from the central to eastern EKOB. The formation ages of granodiorite in the Bairiqili area, the granodiorite in the Wulonggou area are 410 ± 2 Ma and 396 ± 1 Ma, respectively, and the granodiorites show I-type features. The Wulonggou syenogranite with a formation age of 398 ± 2 Ma has a high differentiation index (D.I. = 89.59–92.43), and may belong to the high fractionated I-type granite. The Lalangmai tonalite with a formation age of 423 ± 2 Ma has high Sr (339–590 μg/g), εHf(t) (1.5–7.3), and low Y (3.45–6.33 μg/g), which are similar to modern adakites. The Lalangmai tonalite is the latest adakite record during the Proto-Tethys evolution in EKOB. Combined with previous studies, it is concluded that the granitoids from Cambrian to Devonian divided into four episodes. The first episode (515–436 Ma) mainly consists of I-type island arc granites and adakite, which are formed in a subduction environment. The second episode (436–427 Ma) is characterized by the S-type granites related to the collision. The third episode (427–420 Ma) is the transition period between the collision and the post-collision environment. In the fourth episodes (420–385 Ma), granitoids were formed in post-collision extensional environment, which is characterized by I-type and A-type granites. The upwelling of asthenosphere material is likely caused by the collapse of the orogenic belt. After 420 Ma, I-type and A-type granites formed at different depths but in the same environment.