Impedance Modeling and Resonance Suppression Method for Current Source VSG Under Weak Grid Conditions

Bin Zhu-Zuo,Min Sun-Shu,Yuan Liu-Yi,Ping Huang-Shao 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.4

A large proportion of renewable energy is integrated into power system, resulting in the gradual electrifi cation of the power system and appearing the characteristics of a weak power grid. Under weak grid, current source virtual synchronous generator (VSG) is prone to resonance. To ensure stable and uninterrupted operation of renewable energy through power electronic devices connected to grid, this paper proposes a composite control method based on grid voltage feedforward (GVF) and q-axis impedance reshaping (QAIR) for current source VSG converter resonance suppression. Firstly, sequence impedance modeling (SIM) and stability analysis are conducted on current source VSG converter. Under weak grid, the negative resistance eff ect caused by phase-locked loop (PLL) in the low frequency range makes system unstable in grid connection. To eliminate the negative resistance instability caused by PLL, a current source VSG GVF control resonance suppression method is established. SIM of this method and stability analysis are conducted. Secondly, a QAIR resonance suppression method for current source VSG converter is established. SIM of the method is conducted and stability analyzed. On the basis of above two methods, a composite resonance suppression method based on GVF and QAIR is established, and SIM and stability analysis are conducted. Simulation and experimental tests are conducted on the stability of GVF, QAIR, and GVF + QAIR composite resonance suppression current type VSG systems. The test results showed that the method based on GVF + QAIR resonance suppression is more eff ective, compared to GVF/QAIR resonance suppression method. Under weak grid, it has better ability to eliminate negative resistance eff ects and harmonic suppression caused by PLL, further improving grid-connected stability.

A Simplified Method to Predict Damage of Axially-Loaded Circular RC Columns Under Lateral Impact Loading

Bin Liu,Wei Fan,Xu Huang,Xudong Shao,Lijing Kang 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.4

Detailed finite element (FE) models are often employed to predict the impact responses of reinforced concrete (RC) columns. However, they always require substantial investments of time and effort in modeling and analysis so that they are not widely used in practice, particularly in preliminary designs. Moreover, although some simplified models have been established for beams and slabs under impact loading, few attempts have been made on modeling RC columns. For these reasons, this paper proposes a simplified modeling method to accurately capture the impact-induced response and damage of circular RC columns. In the proposed method, a two-degree-of-freedom (DOF) system was used to describe the interaction between the impactor and the impacted column. The formulas, and procedure to estimate the force-deformation relationship with strain-rate effects were presented according to the section-based analysis. The influence of the unloading stiffness on the residual deformation was addressed, and the method to determine the unloading stiffness of circular columns was proposed. Furthermore, a fiber-based beam-column element modeling method was developed to estimate the force-deformation relationship of the columns with strain-rate effects. The proposed simplified method was demonstrated by the drop-hammer impact tests to be capable of predicting the impact response of RC columns well. Its accuracy in the residual deformation is superior to that of the detailed FE simulation. Parametric studies were performed to investigate the damage characteristics of axially-loaded circular RC columns under various impact scenarios.

Cloning, Expression, and Characterization of a New Phytase from the Phytopathogenic Bacterium Pectobacterium wasabiae DSMZ 18074

( Shao Na ),( Huo Qing Huang ),( Kun Meng ),( Hui Ying Luo ),( Ya Ru Wang ),( Pei Long Yang ),( Bin Yao ) 한국미생물 · 생명공학회 2008 Journal of microbiology and biotechnology Vol.18 No.7

Intensity-Modulated Radiotherapy versus Three-Dimensional Conformal Radiotherapy in Definitive Chemoradiotherapy for Cervical Esophageal Squamous Cell Carcinoma: Comparison of Survival Outcomes and Toxicities

Nai-Bin Chen,Bo Qiu,Jun Zhang,Meng-Yun Qiang,Yu-Jia Zhu,Bin Wang,Jin-Yu Guo,Ling-Zhi Cai,Shao-Min Huang,Meng-Zhong Liu,Qun Li,Yong-Hong Hu,Qi-Wen Li,Hui Liu 대한암학회 2020 Cancer Research and Treatment Vol.52 No.1

Purpose The purpose of this study was to compare the survival and toxicities in cervical esophageal squamous cell carcinoma (CESCC) treated by concurrent chemoradiothrapy with either three-dimensional conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) techniques. Materials and Methods A total of 112 consecutive CESCC patients were retrospectively reviewed. 3D-CRT and IMRT groups had been analyzed by propensity score matching method, with sex, age, Karnofsky performance status, induction chemotherapy, and tumor stage well matched. The Kaplan- Meier method and Cox proportional hazards model were used for overall survival (OS) and progression-free survival (PFS). Toxicities were compared between two groups by Fisher exact test. Results With a median follow-up time of 34.9 months, the 3-year OS (p=0.927) and PFS (p=0.859) rate was 49.6% and 45.8% in 3D-CRT group, compared with 54.4% and 42.8% in IMRT group. The rates of grade ! 3 esophagitis, grade ! 2 pneumonitis, esophageal stricture, and hemorrhage were comparable between two groups, while the rate of tracheostomy dependence was much higher in IMRT group than 3D-CRT group (14.3% vs.1.8%, p=0.032). Radiotherapy technique (hazard ratio [HR], 0.09; 95% confidence interval [CI], 0.01 to 0.79) and pretreatment hoarseness (HR, 0.12; 95% CI 0.02 to 0.70) were independently prognostic of tracheostomy dependence. Conclusion No survival benefits had been observed while comparing IMRT versus 3D-CRT in CESCC patients. IMRT with fraction dose escalation and pretreatment hoarseness were considered to be associated with a higher risk for tracheostomy dependence. Radiation dose escalation beyond 60 Gy should be taken into account carefully when using IMRT with hypofractionated regimen.

Research on Control Strategy of Hybrid Energy Storage System with Optical Storage Microgrid

Zhu Zuo-Bin,Sun Shu-Min,Ding Yue-Ming,Huang Shao-Ping 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4

With the aim of improving the robustness of the hybrid energy storage system(HESS) and avoiding overcharging and reasonably managing state of charge (SOC), this paper proposed a HESS control strategy employing integral backstepping (IBS) method based on SOC. Firstly, on the basis of the hybrid energy storage control strategy of conventional filtering technology (FT), the current inner loop PI controller was changed into an controller employing IBS method to improve the robustness shown by the energy storage system (ESS) against system parameter perturbation or external disturbance. The current controller of the HESS employing inner loop integral backstepping method was designed and the Lyapunov stability was proven. Secondly, to avoid overcharging and over-discharging of the HESS and to reasonably manage SOC, an energy management strategy based on SOC was proposed to generate the current reference value of the inner loop controller employing integral backstepping method, and the energy management strategy based on SOC was designed as well. Finally, the simulation model of the HESS employing integrated backstepping method based on SOC was established, and the feasibility of this method was verified through simulation. It was shown by the results obtained from the simulation that the HESS control strategy employing integrated backstepping method based on SOC had greater anti-interference ability and improved the robustness of the system, in comparison with the control strategy of FT (PI) and FT (IBS) hybrid energy storage. In the meanwhile, the upper and lower limits of SOC of the ESS are supposed to be managed to avoid overcharging and over-discharging and to extend the life of the ESS.

Novel Low-Temperature-Active Phytase from Erwinia carotovora var. carotovota ACCC 10276

Huo Qing Huang,Hui Ying Luo,Ya Ru Wang,Da Wei Fu,Na Shao,Pei Long Yang,Kun Meng,Bin Yao 한국미생물 · 생명공학회 2009 Journal of microbiology and biotechnology Vol.19 No.10

A Formal Verification Method of Obligation Policy in Multi-agent System

Zhang Tao,Xie Hong,Huang Shao-bin 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.11

In Multi-Agent System, obligations are actions that agents are required to take or some states of affairs which should be maintained, formal modeling and verifying obligation policy which is high-level requirements specifications or communication protocol for constraining agent interaction can enhance the correctness of the system design. In this paper, we present a formal framework for modeling obligation policy, the framework is formalized using concepts of social commitments, it allows reasoning about change in the states of obligations and provides Kripke operational semantics which can help to convert framework of obligation policy to the input model of model checker MCMAS, at the same time ,the properties of framework depending on policy conflicts are represented with CTL, and the violations of properties is detected by using MCMAS which can provide the counterexample and trace it back to the errors in interaction policy. Finally, we present an implementation and report on experimental results of verifying obligation policy using MCMAS model checker.

Study on the Magnetic Rate Sensitivity and Shear Properties of Magnetorheological Shear Thickening Fluid

Guo-Jun Yu,Shao-Jie Zhu,Cheng-Bin Du,Ling-Yun Wang,Jun-Chi Huang 한국자기학회 2023 Journal of Magnetics Vol.28 No.3

This paper studies magnetic field control and velocity-activated magnetorheological shear thickening fluid (MR-STF). High-concentration STF is composed of nano-sized silica particles suspended in a solvent polyethylene glycol (PEG), and then micron-sized carbonyl iron particles of different mass fractions are added to the STF to manufacture different MR-STF. The rheometer is used to study the viscoelasticity of all four samples. The correlation between dynamic behavior and shear rate, angular frequency, and external magnetic field is studied and discussed. In the lower angular frequency range, the loss modulus is slightly larger than the storage modulus, and MR-STF behaves as a viscoelastic state. After the critical angular frequency, the storage modulus decreases sharply, well below the loss modulus. MR-STF appears in a viscous state and a liquid state. With the start of external field excitation, MR-STF is more inclined to MRF. Finally, the apparent viscosity and shear rate of MR-STF are fitted. The results show that with the increase of magnetic induction strength, the plastic viscosity coefficient of MR fluid increases, the flow characteristic index decreases, and the shear thinning effect becomes more significant.

Fulvifomes nonggangensis and F. tubogeneratus (Hymenochaetales, Basidiomycota): Two New Species from Southern China Based on Morphological and Molecular Evidences

( Hai-Fu Zheng ),( Fu-chang Huang ),( Bin Liu ),( Yuan-Yuan Shao ),( Pei-sheng Qin ) 한국균학회 2021 Mycobiology Vol.49 No.3

Two new species of Fulvifomes are described from specimens collected in rainforests of Nonggang Nature Reserve of southern China, based on morphological characteristics and molecular phylogenetic analysis of the internal transcribed spacer (ITS) and nuclear large subunit ribosomal DNA (nLSU) sequences. Fulvifomes nonggangensis sp. nov. is characterized by perennial, sessile and solitary basidiocarps, applanate pileus, small cystidioles of 9.9-15.4×2.9-3.5 lm, large pores of 5-6 per mm, a dimitic hyphal system, and broadly ellipsoid basidiospores of 4.3-5.3×3.3-4.2 lm. F. tubogeneratus sp. nov. is characterized by perennial, sessile, and imbricate basidiocarps, a duplex context, small pores of 7-8 per mm, a dimitic hyphal system, and ovoid to subglobose basidiospores of 5.72×5.00 lm.

Analysis on Clinical Characteristics and Influencing Factors of Patients with Locoregionally Advanced Nasopharyngeal Carcinoma

Zheng, Wei,Xu, Yuan-Ji,Qiu, Su-Fang,Zong, Jing-Feng,Huang, Ling-Ling,Huang, Chao-Bin,Lin, Shao-Jun,Pan, Jian-Ji Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.10

Background: To explore the independent prognostic factors for the recurrence/metastasis of patients with locoregionally advanced nasopharyngeal carcinoma (LANPC). Materials and Methods: A total of 604 patients initially diagnosed as LANPC by pathohistology in Fujian Provincial Cancer Hospital were selected to analyze the relationship between the clinical pathological patterns, therapeutic protocols and clinical stages with the recurrence/metastasis of LANPC. Results: The 1-, 3- and 5-year locoregionally recurrent rates of LANPC patients were 2.0%, 9.5% and 12.9% respectively, with average recurrent period being 78 months. Univariate analysis results indicated that clinical stages had certain influence on the recurrent period of LANPC patients. However, COX regression models showed that ages, genders and clinical stages were not the independent prognostic factors influencing the recurrence. The 1-, 3- and 5-year metastatic rates of LANPC patients were 6.6%, 17.5% and 18.8% respectively, with average metastatic period of 73 months. Univariate analysis results demonstrated that ages, N stages, clinical stages, locations of lymph node, retropharyngeal lymph node and extracapsular invasion of lymph node had certain influence on the metastatic period of LANPC patients. Additionally, further COX regression analysis results suggested that T stages, reduction protocols and extracapsular invasion of lymph node were the independent prognostic factors influencing the metastasis of patients with LANPC, in which T stages and extracapsular invasion of lymph node were the pestilent factors while reduction protocols the protective factor. Conclusions: Induction chemotherapy is beneficial to LANPC patients with initial treatment, and the metastatic rate decreases greatly after the application of reduction chemotherapy.