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Reclosing Current Limiting for DC Line Faults in VSC-HVDC Systems

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Journal of Modern Power Systems and Clean Energy 2022年第4期10卷 1040-1049页

作者： Shunliang Wang Junjie Zhou Ji Shu Tianqi Liu Junpeng Ma College of Electrical Engineering Sichuan UniversityChengdu 610065China

The problem of reclosing current limiting in voltage source converter based high-voltage direct current(VSCHVDC)systems is becoming more and more serious.A soft reclosing scheme for DC permanent faults is presented in this paper.Because the converter voltages of stations at both terminals of the disconnected faulty line may be different,the choice of which terminal to reclose first will affect the reclosing overcurrent.A method for selecting the terminal to reclose first is investigated to achieve a minimum peak overcurrent during the reclosing process.In order to ensure that the hybrid DC circuit breaker(HDCCB)adapts to the needs of the reclosing process better,the traditional HDCCB is improved by adding a soft reclosing module(SRM).The energy dissipated in the arresters is significantly reduced when using the improved HDCCB.The improved HDCCB will be able to reclose multiple times safely and thus increase the possibility of successful reclosing.Moreover,the recovery time after the HDCCB is successfully reclosed is very short with the improved HDCCB and its control principles.Simulation results show that this proposed scheme is capable of limiting the reclosing overcurrent when the fault still exists.

关键词： Soft reclosing current limiting voltage source converter based high-voltage direct current(VSC-HVDC) DC fault

Fromα-keto acids to nitrile oxides enabled by copper nitrate:a facile access to fused isoxazolines

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Organic Chemistry Frontiers 2022年第3期9卷 676-681页

作者： Yuping Zhu Tianqi Liu Bingxin liu Houguang Shi Qitao Tan Bin Xu Department of Chemistry Affiliated Nantong Hospital of Shanghai University(The Sixth People’s Hospital of Nantong)Shanghai Engineering Research Center of Organ RepairInnovative Drug Research CenterSchool of MedicineShanghai UniversityShanghai 200444China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

α-Keto acids were unprecedentedly employed as novel precursors of nitrile oxides on treatment with copper nitrate,which reacted with maleimides via[3+2]dipolar cycloaddition leading to pharmacologically interesting fused isoxazolines.This approach offers a unique strategy and complementary method for the convenient generation of alkyl substituted nitrile oxides.

关键词： nitrate fused oxides

Oxidative cyclization of allyl compounds and isocyanide: A facile entry to polysubstituted 2-cyanopyrroles

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Chinese Chemical Letters 2024年第4期35卷 330-335页

作者： Yaping Zhang Wei Zhou Mingchun Gao Tianqi Liu Bingxin liu Chang-Hua Ding Bin Xu Department of Chemistry Affiliated Nantong Hospital of Shanghai University(The Sixth People's Hospital of Nantong)Shanghai Engineering Research Center of Organ RepairInnovative Drug Research CenterSchool of MedicineShanghai UniversityShanghai 200444China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

A facile Tf OH-catalyzed oxidative cyclization of allyl compounds and isocyanide has been developed with the assistance of DDQ, where isocyanide is used as the crucial "N" and "CN" sources. Highly functionalized 2-cyanopyrroles are constructed efficiently through a new formal [3 + 2] mode, demonstrating diverse reactivity and synthetic utility in organic chemistry. 2-Cyanopyrrole is converted into a nucleobase analogue of Remdesivir and 5H-pyrrolo[2,1-a]isoindole through a three-step or a two-step sequence, respectively. This protocol features broad substrate scope, operational simplicity and good functional group tolerance.

关键词： Isocyanide Cyanopyrrole Insertion Allyl compound Bronsted acid catalysis

Online Identification of Lithium-ion Battery Model Parameters with Initial Value Uncertainty and Measurement Noise

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Chinese Journal of Mechanical Engineering 2023年第1期36卷 305-314页

作者： Xinghao Du Jinhao Meng Kailong liu Yingmin Zhang Shunli Wang Jichang Peng Tianqi Liu College of Electrical Engineering Sichuan UniversityChengdu610044China School of Electrical Engineering Xi’an Jiaotong University710049Xi’anChina Warwick Manufacturing Group University of WarwickCoventryUK Southwest University of Science and Technology Mianyang621010China Nanjing Institute of Technology Nanjing211103China

Online parameter identification is essential for the accuracy of the battery equivalent circuit model(ECM).The traditional recursive least squares(RLS)method is easily biased with the noise disturbances from sensors,which degrades the modeling accuracy in practice.Meanwhile,the recursive total least squares(RTLS)method can deal with the noise interferences,but the parameter slowly converges to the reference with initial value uncertainty.To alleviate the above issues,this paper proposes a co-estimation framework utilizing the advantages of RLS and RTLS for a higher parameter identification performance of the battery ECM.RLS converges quickly by updating the parameters along the gradient of the cost function.RTLS is applied to attenuate the noise effect once the parameters have converged.Both simulation and experimental results prove that the proposed method has good accuracy,a fast convergence rate,and also robustness against noise corruption.

关键词： Li-ion battery Equivalent circuit model Recursive least squares Recursive total least squares

Graph Theory Based N-1 Transmission Contingency Selection and Its Application in Security-constrained Unit Commitment

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Journal of Modern Power Systems and Clean Energy 2021年第6期9卷 1458-1467页

作者： Lu Nan Yikui liu Lei Wu Tianqi Liu Chuan He College of Electrical Engineering Sichuan University the Department of Electrical and Computer Engineering Stevens Institute of Technology Department of Electrical and Computer Engineering Stevens Institute of Technology

Contingency analysis is an important building block in the stability and reliability analysis of power grid operations. However, due to the large number of transmission lines,in practice only a limited number of contingencies could be evaluated. This paper proposes a graph theory based N-1 contingency selection method to effectively identify the most critical contingencies, which can be used in security-constrained unit commitment(SCUC) problems to derive secure and economic operation decisions of the power grid. Specifically, the power flow transferring path identification algorithm and the vulnerability index are put forward to rank individual contingencies according to potential transmission line overloads. Effectiveness of the proposed N-1 contingency selection method is quantified by applying the corresponding SCUC solution to the full N-1 security evaluation, i. e., quantifying total post-contingency generation-load imbalance in all N-1 contingencies. Numerical results on several benchmark IEEE systems, including5-bus, 24-bus, and 118-bus systems, show effectiveness of the proposed method. Compared with existing contingency selection methods which usually resort to full power flow calculations,the proposed method relies on power gird topology to effectively identify critical contingencies for facilitating the optimal scheduling of SCUC problems.

关键词： Concentric relaxation contingency analysis graph theory security-constrained unit commitment(SCUC) shortest path vulnerability index

Day-ahead Risk-constrained Stochastic Scheduling of Multi-energy System

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Journal of Modern Power Systems and Clean Energy 2021年第4期9卷 720-733页

作者： Yue Yin Tianqi Liu Lei Wu Chuan He Yikui liu Department of Electrical Engineering Sichuan UniversityChengdu 610065China Department of Electrical and Computer Engineering Stevens Institute of TechnologyHobokenNJ 07030USA

As an increasing penetration of renewable energy sources can potentially impact voltage profile and compromise system security,the security continues to be the most critical concern in power system operations.A risk-constrained stochastic scheduling model is proposed to leverage the latent scheduling capacity of a multi-energy system to seek an economic operation solution while maintaining system operation risk level against uncertain renewable generation.Overvoltage risk constraints,as compared to the straightforward voltage boundary limits,are incorporated into the stochastic scheduling model to guarantee the operation security and economics.Linearized AC power flow model is applied to enable overvoltage risk assessment within the coordinated scheduling model.The proposed stochastic scheduling model is tackled via the improved progressive hedging approach with an enhanced relax-round-polish process,which overcomes the convergence issues of the traditional progressive hedging in handling nonconvex stochastic scheduling model with binary variables on both stages.Numerical simulation results of IEEE 30-bus system and IEEE 118-bus system illustrate the efficacy of the proposed model in ensuring voltage security and improving economic operation of systems.

关键词： AC power flow overvoltage risk constraint renewable energy multi-energy coordination

Adaptive Neural Control for Nonlinear MIMO Function Constraint Systems

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IEEE/CAA Journal of Automatica Sinica 2023年第3期10卷 816-818页

作者： tianqi Yu Yan-Jun liu Lei liu College of Science Liaoning University of TechnologyJinzhou 121001China IEEE

Dear Editor,In this letter,a novel adaptive control design problem for uncertain nonlinear multi-input-multi-output(MIMO)systems with time-varying full state constraints is proposed,where the considered systems consist of various subsystems,and the states of each subsystem are interconnected tightly.It is universally acknowledged that in the existing researches with state constraints,system constraint bounds are always constants or time-varying functions.

关键词： MIMO constraints Nonlinear

Operation-area-constrained Adaptive Primary Frequency Support Strategy for Electric Vehicle Clusters

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Journal of Modern Power Systems and Clean Energy 2023年第6期11卷 1982-1994页

作者： Tianqi Liu Pengyu Wang Qiao Peng Min Zhang Tengxin Wang Jinhao Meng College of Electrical Engineering Sichuan UniversityChengdu 610065China Electric Power Research Institute State Grid Shanxi Electric Power CompanyTaiyuan 030001China

Due to their fast response and strong short-term power throughput capacity, electric vehicles(EVs) are promising for providing primary frequency support to power grids. However, due to the complicated charging demands of drivers, it is challenging to efficiently utilize the regulation capacity of EV clusters for providing stable primary frequency support to the power grid. Accordingly, this paper proposes an adaptive primary frequency support strategy for EV clusters constrained by the charging-behavior-defined operation area. First, the forced charging boundary of the EV is determined according to the driver's charging behavior, and based on this, the operation area is defined. This ensures full utilization of the available frequency support capacity of the EV. An adaptive primary frequency support strategy of EV clusters is then proposed. The output power of EV is adaptively regulated according to the real-time distance from the EV operating point to the forced charging boundary. With the proposed strategy, when the EV approaches the forced charging boundary, its output power is gradually reduced to zero. Then, the rapid state-of-charge declines of EVs and sudden output power reductions in EV clusters caused by forced charging to meet the driver's charging demands can be effectively avoided. EV clusters can then provide sustainable frequency support to the power grid without violating the driver's charging demands. Simulation results validate the proposed operation-area-constrained adaptive primary frequency support strategy, which outperforms the average strategy in terms of stable output maintenance and the optimal utilization of regulation capacities of EV clusters.

关键词： Primary frequency control frequency support electric vehicle vehicle-to-grid(V2G) operation area charging behavior

Joint Limiting Control Strategy Based on Virtual Impedance Shaping for Suppressing DC Fault Current and Arm Current in MMC-HVDC Systems

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Journal of Modern Power Systems and Clean Energy 2023年第6期11卷 2003-2014页

作者： Qin Jiang Yan Tao Baohong Li Tianqi Liu Zhe Chen Frede Blaabjerg Peng Wang IEEE College of Electrical Engineering Sichuan UniversityChengdu 610065China Smart Grid Key Laboratory of Sichuan Province Chengdu610065China State Grid Jiangsu Electric Power Company Research Institute Nanjing 211103China Department of Energy Technology Aalborg UniversityAalborg 9920Denmark School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798Singapore

This paper proposes a joint limiting control strategy for suppressing DC fault current and arm current in modular multilevel converter-based high-voltage direct current(MMC-HVDC) systems, which includes two target-oriented current limiting controls. To limit the DC fault current in the early fault stage, an equivalent modular multilevel converter(MMC) impedance is obtained, and its high-frequency part is reshaped by introducing virtual impedance, which is realized by adjusting the inserted submodules adaptively. Following the analysis of MMC control characteristics, the arm current limiting strategy is investigated, with results showing that the inner-loop control has significant effects on arm current and that a simple low-pass filter can reduce the arm current in the fault period. Finally, by combining the virtual impedance shaping and innerloop control, the fault currents of DC lines and MMC arms can be suppressed simultaneously, which can not only alleviate the interrupting pressure of the DC circuit breaker, but also prevent the MMC from being blocked by the arm overcurrent. Theoretical analysis conclusions and the proposed strategy are verified offline by a digital time-domain simulation on Power Systems Computer Aided Design/Electromagnetic Transients including DC platform, and experiment on a real-time digital simulator platform.

关键词： Modular multilevel converter(MMC) highvoltage direct current(HVDC)transmission direct current fault fault current limitation arm current suppression virtual impedance direct current circuit breaker