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Cheng Zhiping,Wang Kaifang,Li Zhongwen,Wu Haotian,Zhi Changyi,Zhang Jinbin 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.1
In this paper, distributed secondary control of AC microgrid (MG) is studied and the infuence of communication delay on its control performance is analyzed and verifed. Firstly, a secondary control strategy for the MG is designed to achieve frequency recovery and proportional active power dispatch. Secondly, the stability of the MG system is analyzed in the frequency domain and a rigorous formula is derived to calculate the delay margin for the stability of the distributed secondary control with communication delays. The theoretical calculation results of the stability margin are approximately consistent with the simulation results, with an error of only 1.27%. The efects of the algorithm gains, communication topology, and connection weights on the delay margin are discussed based on the derived formula. The results demonstrate that the algorithm gain is inversely proportional to the delay margin. Changes in the communication topology and connection weights lead to changes in the maximum eigenvalue of the adjacency matrix L, which in turn afects the delay margin. Moreover, the infuence of time-varying delays is considered. The system can tolerate greater time-varying delays than fxed delays. Simulation and experimental results validate the efectiveness and feasibility of the proposed method.
Recovery of Bisphenol A by pH-Triggered Magnetic Nanoparticles
Yongsheng Jia,Enze Li,Zhiping Du,Jianfeng Li,Fangqin Cheng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.5
Bisphenol A is not only one of the frequent contaminants of industrial wastewater, but also one of the main ingredients in polycarbonate and epoxy resins. This study synthesizes a pH-triggered Fe3O4@mSiO2@DPDES adsorbent for recycling Bisphenol A through adsorption–desorption process. Due to the strong π–π interaction between the phenyl groups in diphenyldiethoxysilane modified magnetic nanoparticles (MNPs) and Bisphenol A, absorbance reached 120.17 mg/g at pH 7, allowing the bisphenol A adsorbed to Fe3O4@mSiO2@DPDES to be trivially separated from aqueous solutions with a magnet. Desorption of the adsorbed bisphenol A in aqueous solution occurred at pH 2, allowing an impressive 95% recovery rate. The durability of the Fe3O4@mSiO2@DPDES adsorbent was tested by repeated separation of bisphenol A from an aqueous solution, with the recovery efficiency remaining greater than 85% after five cycles.
Li Zhongwen,Bai Ningning,Cheng Zhiping,Wang Yi,Si Jikai 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.2
With the increasing use of renewable energy sources connected to inverters in modern power systems, traditional units’ rotary inertia and frequency regulation capacity are becoming inadequate. Therefore, exploring various types of frequency regulation resources is essential. However, these resources come with diferent system models, capacities, and response speeds, posing a signifcant challenge to automatic generation control (AGC). To address this issue and enhance the frequency regulation performance of these resources, a novel distributed coordination AGC method is proposed. The proposed method allows each frequency regulation unit to utilize a separate load frequency control (LFC) controller to participate in frequency regulation based on the area control error information calculated by the dispatching center. To ensure the coordination between the heterogeneous frequency regulation resources, an adaptive chaotic gray wolf algorithm is proposed to tune the parameters of the LFC controller. Furthermore, to release the fast frequency regulation ability of high-speed frequency regulation units and better prepare for the next round of frequency regulation service, an event-triggered power dispatching strategy is proposed. Simulation results of a single-area power system with fve diferent frequency regulation units demonstrate the superior performance of the proposed AGC method.
Observation of multi-channel non-local transport in J-TEXT plasmas
Shi, Yuejiang,Chen, Zhongyong,Yang, Zhoujun,Shi, Peng,Zhao, Kaijun,Diamond, Patrick H.,Kwon, JaeMin,Yan, Wei,Zhou, Hao,Pan, Xiaoming,Cheng, Zhifeng,Chen, Zhiping,Yang, SeongMoo,Zhang, Chi,Li, Da,Dong, IOP 2018 Nuclear fusion. Fusion nucléaire. &n.Illiga Vol.58 No.4
<P>In cold pulse experiments in J-TEXT, not only are rapid electron temperature increases in the core observed, but also steep rises in the inner density are found. Moreover, some evidence of acceleration of the core toroidal rotation is also observed during the non-local transport process of electron temperature. These new findings of cold pulse experiments in J-TEXT suggest that turbulence spreading is a possible mechanism for the non-local transport dynamics.</P>