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International Conference on electrical Machines and systems (ICEMS)

作者： Xinyu Yang Daqiang Bi Zhengping Wu Xiaochun Mou Electrical Engineering and Renewable Energy School Three Gorges University Yichang China State Key Laboratory of Power System Department of Electrical Engineering Tsinghua University Beijing China State Grid Electric Power Research Institute Nanjing China

Due to the large power fluctuation in the mode conversion of Mircogrid, the single energy storage is hard to support the balance of power quickly and stably, which makes the mode conversion not stable and influences the quality of power supply. To improve the performance of microgrid conversion, a new control strategy is presented in this paper. In hybrid structure of vanadium redox battery (VRB) and supercapacitor, the supercapacitor adopts vf control to follow up the network voltage and frequency while microgrid turns into the islanded mode, making sure the voltage and frequency of microgrid and the network synchronization. VRB adopts vf/PQ control to ensure power balance of microgrid operation. This control strategy can improve the conversion rate of microgrid and ensure the stability of microgrid system. The simulation results show that the hybrid energy storage can achieve the excellent performance.

关键词： Supercapacitors Voltage control Batteries Fluctuations power system stability Hybrid power systems

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control strategy of grid-connected photovoltaic system with energy storage

Control strategy of grid-connected photovoltaic system with ...

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International Conference on electrical Machines and systems (ICEMS)

作者： Daqiang Bi Sigeng Wang Baoming Ge Xinyu Yang State Key Laboratory of Power System Department of Electrical Engineering Tsinghua University China School of Electrical Engineering Beijing Jiaotong University BJTU China School of Electrical Engineering and Renewable Energy Three Gorges University China

With the increasing of grid-connected capacity of photovoltaic(PV) power generation, the influence of its power fluctuation on the grid becomes more and more serious. To improve the interface characteristics of large-scale PV system, a control strategy of Virtual Synchronous Generator is introduced to the energy storage-based grid-connected PV system. The proposed control strategy achieves a novel and friendly interface like a traditional synchronous generator, which is contributed to the PV system accepted by the grid. The simulation model is built and the simulation results verify the proposed control system.

关键词： Synchronous generators power system stability Load modeling Voltage control Fluctuations Batteries

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Design of Global power systems Stabilizer to Damp Interarea Oscillations Based on Wide-Area Collocated control Technique

Design of Global Power Systems Stabilizer to Damp Interarea ...

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IEEE power and Energy Society General Meeting

作者： Jing Ma Tong Wang Zengping Wang Jie Wu James S. Thorp School of Electrical and Electronic Engineering North China Electric Power University and also with the Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University State Nuclear Electric Power Planning Design and Research Institute Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University

ISBN: (纸本)9781457710001

This paper develops a systematic procedure of designing global power system stabilizers (GPSSs) based on collocated control to enhance the damping during interarea oscillations. The availability of remote signals from phasor measurement units (PMUs) enables the wide-area control in large scale systems. The closed loop eigenvalues are excluded from a region of the complex plane by the collocated control algorithm guaranteeing that low frequency modes must be damped. The optimum locations for GPSSs were selected using controllability. The damping performance of a 16-machine, 68-bus study system reinforced with GPSSs is examined in the frequency and time domains. The simulation results show that the control scheme is able to damp out interarea oscillations following possible disturbances.

关键词： PMUs Interarea oscillations Collocated control Global power system stabilizers Phasor measurement units absorption of shock dinitrophenyl-aminopropyl-methylamine Oscillations control technology Complex Plane power system stability Computer algorithms

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Study on aging characteristics of mineral oil/natural ester mixtures-paper insulation

Study on aging characteristics of mineral oil/natural ester ...

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International Conference on Conduction and Breakdown in Dielectric Liquids

作者： Ruijin Liao Jian Hao Lijun Yang Stanislaw Grzybowski The State Key Laboratory of Power Transmission Equipment & System Security and New Technology Chongqing University Chongqing China High Voltage Laboratory Department of Electrical and Computer Engineering Mississippi State University MS USA

Transformer is one of the most critical equipment insuring the safe operation of power grids. The aging of insulation materials (mainly parts are the insulation oil and transformer paper) decide the operational life of the transformer. This paper is aimed at improving the anti-aging properties of power transformer via using new mineral oil/natural ester mixtures. The aging characteristics of mixed insulating oil-paper insulation and mineral oil-paper insulation were provided through 264 days' accelerated thermal aging at 110°C. The color of the oil, oil acidity, degree of polymerization (DP) of the paper and the thermal stability behavior of oil-paper insulation with different aging status were compared. Results show that the mixed insulating oil can not only restrain the oil oxidation itself, but also can restrain the aging rate of the paper immersed in the mixed insulating oil. The thermal stability of oil-paper insulation could be also improved by using the mixed insulating oil.

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A new algorithm to identify magnetizing inrush of converter transformers in HVDC transmission project

A new algorithm to identify magnetizing inrush of converter ...

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International Conference on electrical Machines and systems (ICEMS)

作者： Da-qiang Bi Cun-liang Feng Zhen-hua Zhang Bao-ming Ge Xin He State Key Laboratory of Power System Department of Electrical Engineering Tsinghua University China School of Electrical Engineering Beijing Jiaotong University BJTU China Xuji Hitachi Electrical Appliances Corporation Limited China Department of Electric Engineering Northeast Dianli University China

This paper proposes an algorithm to detect the magnetizing inrush of two double-winding converter transformers in bipolar high voltage direct current (HVDC) transmission project by analyzing the waveform characteristics of the resultant current in the grid side. Delivery test of transformer may remain the different polarity of remanent flux in each converter transformer, which causes the inrush directions different when the two double-winding converter transformers are energized at the first time. So that the resultant current at the grid side is close to sinusoid and this leads to the mal-operation of differential protection. In this paper, the generalized nonsaturation zone of inrush current is proposed and the virtual current in the generalized nonsaturation zone is calculated by subtracting the DC offset in the inrush. A normal sinusoidal waveform is structured according to the virtual current, and the waveform coefficient between the structured current and actual current is calculated. The waveform coefficients are used to distinguish magnetizing inrush from fault current. The extreme cases simulated by RTDS (Real Time Digital Simulator) and the field data in China are analyzed and tested. The test results indicate that the proposed algorithm successfully detects magnetizing inrush during the transformers energized at the first time and other times. It is ensured that the differential protection is reliably blocked during inrush and quickly enabled during the short-circuit fault and even a small turn-to-turn fault.

关键词： Surges Surge protection Fault currents Circuit faults Magnetic flux HVDC transmission Harmonic analysis

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Transient interaction of HVAC and HVDC in converter station in HVDC, II: Equivalence circuit in AC side and steady-state debugging

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Gaodianya Jishu/High Voltage engineering 2011年第3期37卷 537-547页

作者： Chen, Shui-Ming Huang, Lu-Lu Xie, Hai-Bin Yu, Zhan-Qing State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China

The interaction of nanoseconds, microseconds, milliseconds electromagnetic transients due to AC-DC system operation and fault, the DC converter valve movement, the load generated by changes in the interaction of AC-DC interconnected system electromagnetic transient, can pose a hazard on AC and DC power systems, in particular, lead to the commutation of DC system failures and artesian such serious incidents. Combining theoretical analysis with test, we can establish the analysis method of electromagnetic transient of the full-wave process of the UHV system based on AC-DC interconnected system, control systems, and underground grounding system, and focus on the equivalence circuit of AC side network with the Ward method of equivalency under many operation modes and steady-state debugging for the analysis of AC-DC interconnected system, so as to lay the foundation for the interaction of electromagnetic transient.

关键词： Timing circuits

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A DC-link Voltage control Scheme for Single-phase Grid-connected PV Inverters

A DC-link Voltage Control Scheme for Single-phase Grid-conne...

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2011 IEEE Energy Conversion Congress and Exposition (ECCE 2011)

作者： Fanbo He Zhengming Zhao Liqiang Yuan Sizhao Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781457705427;9781457705410

A fast DC-link voltage controller is desirable to reduce the DC-link capacitor for PV inverters. This paper proposes a method for single-phase grid-connected PV inverters to remove the ripple component from the DC-link voltage signal and a scheme to regulate the DC-link voltage based on energy-balance analysis. The proposed scheme provides excellent dynamic performance as well as a function to prevent DC-link overvoltage by limiting the input power, which is verified by both simulation and experiments.

关键词： DC link Polydnaviridae dc-link capacitor Inventors Voltage regulators dynamic characteristics DC link voltage Scheme Voltage regulation link voltage

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Voltage Fluctuation Suppression Method of Floating Capacitors in a New Modular Multilevel Converter

Voltage Fluctuation Suppression Method of Floating Capacitor...

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2011 IEEE Energy Conversion Congress and Exposition (ECCE 2011)

作者： Kui Wang Yongdong Li Zedong Zheng Lie Xu State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781457705427

Modular multilevel converter (MMC) is a newly emerging multilevel topology for high power applications in recent years. The voltage fluctuation problem of a new MMC topology is studied in this paper. In order to suppress the voltage fluctuation of the floating capacitors, a control method is proposed by injecting high frequency zero-sequence voltage and phase-to-phase circulating currents. It can be used to drive an induction motor with pump/blower-like load at low speed and improve the performance significantly. A low power three-phase five-level prototype is built up to validate this method.

关键词： Bridge circuits Fluctuations Capacitors Voltage fluctuations Voltage control Frequency modulation Time frequency analysis

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Transient interaction of HVAC and HVDC in converter station in HVDC, IV: Effects of DC sides on AC sides

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Gaodianya Jishu/High Voltage engineering 2011年第7期37卷 1590-1597页

作者： Chen, Shui-Ming Yu, Zhan-Qing Huang, Lu-Lu Xie, Hai-Bin State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China

China AC-DC power systems are interconnected to form a huge power grid. The nanoseconds, microseconds, milliseconds electromagnetic transient were generated due to AC-DC system operation and fault, the DC converter valve movement, the load generated by changes in the interaction of AC-DC interconnected system electromagnetic transient, which can pose a hazard on AC and DC power systems, in particular, can lead to the commutation of DC system failures and atresia such serious incidents. Based on the broadband characteristics model which can accurately reflect the existing AC-DC interconnected system electromagnetic transient characteristics of the key components, we applied the PSCAD/EMTDC platform to establish a computational model, and revealed DC side electromagnetic transient interaction on AC side. The results show that the DC system has little effect on AC system electromagnetic transient, In various types of failures, the overvoltage produced at side of 750 kV, 330 kV lines and bus are in the allowable range.

关键词： HVDC power transmission

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Transient interaction of HVAC and HVDC in converterer station in HVDC, I: Electromagnetic transient model of equipments in DC side

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Gaodianya Jishu/High Voltage engineering 2011年第2期37卷 395-403页

作者： Chen, Shui-Ming Yu, Zhan-Qing Xie, Hai-Bin Huang, Lu-Lu State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China

Huge interconnected power grids are formed in AC and DC power systems in China. The nanoseconds, microseconds, milliseconds electromagnetic transient due to AC and DC system operation and fault, the DC converter valve movement, the load generated by changes interact in the AC and DC interconnected system, impairing AC and DC power systems, especially leading to the commutation of DC system failures and atresia such serious incidents. Consequently, a theoretical analysis was combined with a test method to establish an over ground network, considering DC electrical networks, control systems and underground grounding system of the full-wave process of the UHV system, Finally, converter transformer was modeled with UMEC model, and transmission line was modeled with J-Marti frequency dependent model;moreover, valve was modeled with transistor, RLC circuit, and other units including DC controller, and DC filter and AC filter were modeled with RLC circuit. The broadband characteristics of electromagnetic transient models of key units in DC sides for the analysis of AC and DC interconnected system were also analyzed.

关键词： controllers

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