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Measurement-based solution for low frequency oscillation analysis

Journal of Modern power systems and Clean Energy 2016年第3期4卷 406-413页

作者： Chen SHEN Zhi AN Xianzhong DAI Wei WEI Lijie DING Department of Electrical Engineering Tsinghua UniversityBeijingChina State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua UniversityBeijingChina Electric Power Research Institute of Sichuan Electric Power Company ChengduChina

This paper presents a measurement-based solution for low frequency oscillation(LFO) analysis in both real time monitoring and off-line case study. An online LFO property discrimination method is developed first,which alternately uses empirical mode decomposition(EMD)/Hilbert transform(HT) and square calculation to process the measurement data. The method magnifies the variation trend of oscillating variables to accurately discriminate the property of the oscillation. Subsequently, an oscillation source locating method for the forced oscillation(FO) and a strongly correlated generator identification method for the weak damping oscillation(WDO) are proposed. Finally, numerical study results on a test system of the isolated Changdu grid in Tibet validate the proposed methods.

关键词： Low frequency oscillation Oscillation property discrimination Oscillation source location Strongly correlated generator identification

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Steady-state security analysis of power system based on the operational reliability theory 3

Steady-state security analysis of power system based on the ...

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3rd International Conference on Reliability of Electrical Products and Electrical Contacts, ICREPEC 2009

作者： Zou, Xin Cheng, Lin Sun, Yuanzhang Department of Electrical Engineering State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China

ISBN: (纸本)9789889968489

Conventional steady-state security analysis have to compute the faults belonging to the predefined faults set in turn with out considering the small probability of the occurrence of some faults under certain circumstances. Although its results reflect the violation of the components precisely, they can not figure out how the violation affects the security of the system. The steady-state security analysis based on the operational reliability theory applies the state-depended models of the components in order to find the faults which would happen with high probability. As a result, only these faults should be calculated to decrease the computation time considerably. Further more, the reliability indices indicate the probability of the violation of the component as well as the influence of the violation on the system security, so that the security of the system can be evaluated comprehensively. IEEE RTS-79 test system is adopted in this paper to illustrate the differences between the conventional and the new steady-state security analysis methods. By contrast, it can be concluded that steady-state security analysis based on the operational reliability theory can calculate the influence of the variation of the component failure probability on the system security more specifically, which making the evaluation results more close to the practical operating system Copyright © 2009 by International Academic Publishers Ltd.

关键词： Reliability theory

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Evaluation of cascading failure in power system based on the operational reliability theory

Evaluation of cascading failure in power system based on the...

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2010 IEEE 11th International Conference on Probabilistic Methods Applied to power systems, PMAPS 2010

作者： Zou, Xin Cheng, Lin Sun, Yuanzhang Department of Electrical Engineering State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China

ISBN: (纸本)9781424457236

According to the characteristics of the cascading failures in power grid, a lot of assessment methods based on the probability theory have been proposed in recent years. However, most of them ignore the influence of the changing operating conditions on the power system planning and operation. This paper assesses the risk of the cascading failure in the power system based on the operational reliability theory which considering the variation of operating states and environment of the power system. The operational reliability of the power system is calculated based on Markov Process which describes the transient probability of states. The key conception of this theory is that the failure rate and the probability of components are changing along with the life of the equipment, the operating states and the environment conditions. A new evaluation procedure is brought up to calculate the operational reliability indices which can provide the specific information of the cascading failure. The evaluating results of the test system confirm that this approach is applicable to analyze the cascading failures in real power system. ©2010 IEEE.

关键词： Reliability theory

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A usage-based transmission cost allocation scheme considering impacts of DERs

A usage-based transmission cost allocation scheme considerin...

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2016 Tsinghua University-IET Electrical Engineering Academic Forum

作者： Wang, J.X. Zhong, H.W. Xia, Q. State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781785614170

With the rapid development of distributed energy resources (DERs), it is of vital importance to develop a well-designed transmission cost allocation scheme to reflect the contributions of DERs to the power system. In this paper, a usage-based transmission cost allocation scheme is proposed considering the capability of DERs. Based on the different intentions of transmission capacity, the transmission costs can be classified into four fractions: operating, contingency, planning and invalid transmission costs. On operating conditions, the transmission costs are identified and allocated according to the actual usage of consumers at each node. On contingency conditions, the transmission cost allocation will be influenced by the behaviors of DERs since DERs can provide emergent power support to help alleviate transmission congestion. On planning conditions, the transmission costs are useful in the future. The residual costs, i.e., the invalid transmission costs, should not allocated by consumers because this fraction is caused by the over investment of transmission owners. The case studies based on the IEEE 30-bus system validates the effectiveness of the proposed scheme and model. © 2016, Institution of Engineering and Technology. All rights reserved.

关键词： Investments

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Research of algorithm and analysis of performance for DC surge impedance relay

Research of algorithm and analysis of performance for DC sur...

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12th IET International Conference on Developments in power System Protection, DPSP 2014

作者： Lei, Aoyu Dong, Xinzhou State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 10084 China

Surge Impedance Relay(SIR) is applied to DC system. Characteristics of SIR in DC line are analysed. A DC SIR algorithm implementing wavelet transform applied to HVDC line protection is proposed. The feasibility of DC ... 详细信息

ISBN: (纸本)9781849198349

关键词： Wavelet transforms

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Cascaded battery energy storage system based on dual active bridges and a common dc bus

Cascaded battery energy storage system based on dual active ...

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2010 9th International power and Energy Conference, IPEC 2010

作者： Jin, Yiding Song, Qiang Liu, Wenhua Sun, Weixin State Key Lab. of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China

ISBN: (纸本)9781424473991

Along with the increasing system capacity, large-scaled energy storage systems are supposed to be connected into 10kV or higher networks. Urban network has strict criterions on power quality of the power electronic devices connected. Moreover, the occupancy and noise of industrial frequency transformers also become restraints to the promotion of urban network energy storage. For that reason, this paper proposes a battery energy storage system based on cascaded dc-ac converter, dual active bridges, and a common dc bus. High frequency transformers are used to replace the industrial frequency transformer for insulation, and battery groups are connected to the common dc bus with respective dc-dc interfaces. This multilevel converter system is easy to modularize, easy to extend, and allows different kinds of batteries to work together. The main circuit and proper control system are designed, with the soft-switching condition and current control issues of the dual active bridge analyzed in detail. The simulation results from EMTDC model verify the operation principles and corresponding control strategies. ©2010 IEEE.

关键词： Electric inverters

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A fast transient simulation model of DFIG based on the piecewise averaging method

A fast transient simulation model of DFIG based on the piece...

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2nd IET Renewable power generation Conference, RPG 2013

作者： Feng, G. Xu, Y. Chen, Y. Gao, H. Chen, L. State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781849197588

Due to the power electronic devices in doubly fed induction generators (DFIG), it is very time consuming to simulate the electromagnetic transients of DFIG using its detailed model. Thus it is necessary to have appropriately simplified model of DFIG that maintains desirable accuracy. In this paper, the piecewise averaged model of PWM converters is introduced and applied to the modelling of DFIG. The proposed model divides the simulation time interval into switching periods and recalculates the averaged state equations of PWM converters in each switching cycle. In addition, a predictorcorrector based EMTP algorithm is designed to iteratively solve the model. Instead of treating switching events at the time points when they happen, the new algorithm solves all the switching instants in a switching cycle at the same time, which avoids frequency modification of the system conductance matrix and speeds up EMT simulations of DFIG. simulation results of a single-machine infinity bus system with a DFIG show that the proposed model and algorithm can achieve satisfactory accuracy and efficiency.

关键词： Equations of state

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Comparison of boost and LLC converter and active clamp isolated full-bridge boost converter for photovoltaic DC system

Comparison of boost and LLC converter and active clamp isola...

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作者： Liu, Jiye Zheng, Zedong Wang, Kui Li, Yong Dong State Key Laboratory of Control Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China

DC collection network offers an attractive alternative to AC network for photovoltaic, as it avoids the charging current issues and reduces the size and weight. Variable voltage gain DC/DC converters play an important role in DC collection network. Two topologies suitable for photovoltaic DC collection are studied. Boost and LLC converter and active clamp isolated full-bridge boost converter are two converters with high and variable voltage conversion ratio suitable for the photovoltaic system. This work investigates the two converters comprehensively. The topologies are analysed so as to summarise and compare the characteristic of the converters. Soft switching condition is compared to help extend the zero voltage switching range. Voltage and current stress of the two converters are calculated. Loss comparison is made with the theoretical analysis. Advantages and disadvantages are summarised to get a deep insight into their application field. © 2019 Institution of Engineering and *** right reserved.

关键词： Topology

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Effects of temperature on creepage discharge characteristics in oil-impregnated pressboard insulation under combined AC–DC voltage

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Plasma Science and Technology 2019年第5期21卷 14-22页

作者： Fubao JIN Yuanxiang ZHOU Bin LIANG Zhongliu ZHOU Ling ZHANG Key Laboratory of Plateau Ecology and Agriculture College of Agriculture and Animal HusbandrySchool of Water Resources and Electric PowerQinghai UniversityXining 800016People's Republic of China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical EngineeringTsinghua UniversityBeijing 100084People's Republic of China

Due to the complexity of the valve side winding voltage of the converter transformer, the insulation characteristics of the oil-impregnated pressboard(OIP) of the converter transformer are different from those of the traditional AC transformer. The study on effect of temperature on the creeping discharge characteristics of OIP under combined AC–DC voltage is seriously inadequate. Therefore, this paper investigates the characteristics of OIP creepage discharge under combined AC–DC voltage and discusses the influence of temperature on creepage discharge characteristics under different temperatures from 70 °C to 110 °C. The experimental results show that the partial discharge inception voltage and flashover voltage decrease with increasing temperature. The times of low amplitude discharge(LAD) decrease and amplitude of LAD increases. Simultaneously, the times of high amplitude discharge(HAD) gradually increase at each stage of creepage discharge with higher temperature. The analysis indicates that the charge carriers easily accumulate and quickly migrate directional movement along the electric field ahead of discharging. The residual charge carriers are more easily dissipated after *** ‘hump’ region of LAD moves to the direction of higher discharge magnitude. The interval time between two continuous discharges is shortened obviously. The concentration of HAD accelerates the development of OIP insulation creepage discharge. The temperature had an accelerating effect on the development of discharge in the OIP under applying voltage.

关键词： oil-impregnated pressboard insulation combined AC-DC voltage inception voltage creepage discharge temperature flashover voltage

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H∞ analysis method for the small signal stability of power system

H∞ analysis method for the small signal stability of power ...

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26th Chinese control Conference, CCC 2007

作者： Mei, Shengwei Che, Wenyan State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)7900719229

This work is concerned with the small signal stability problem in multi-machine systems. By means of H∞ theory, firstly the math model with disturbances is constructed;and secondly, the excitation control law for each generator is designed based on solving Riccati Equation. Finally, simulations performed on 4-machine system shows that the proposed H ∞ method has more advantages over LQR method in both damping ratio and H∞ norm of the corresponding closed-loop system and so can enhance the small signal stability of power system greatly.

关键词： Electric power systems

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