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IEEE Conference and Expo Transportation Electrification Asia-Pacific (ITEC Asia-Pacific)

作者： Xudong Wang Zhengming Zhao Guanhua Chen Fanbo He State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing P. R. China

A broadband RF energy harvesting system over a frequency range of 900MHz-3GHz has been designed and tested. Some detailed issues of RF design have been studied and tested to improve the efficiency of the rectifier. Test results show that as low as -20dBm RF power can be harvested by this system. The series and parallel connections of two RF energy harvesting systems have also been studied, compared with the single system.

关键词： Radio frequency Broadband antennas Rectifiers Energy harvesting Broadband communication Antenna measurements

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Research on HVIGBT transient mixture model and parameter extraction method

Research on HVIGBT transient mixture model and parameter ext...

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IEEE Conference and Expo Transportation Electrification Asia-Pacific (ITEC Asia-Pacific)

作者： Gaohui Feng Zhengming Zhao Liqiang Yuan Shiqi Ji Jincheng Zhao Mechanical Engineering College Shijiazhuang China State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

This paper presents a kind of HVIGBT transient mixture model and corresponding parameter extraction method. The HVIGBT model can divide into MOSFET and BJT two parts. The two models are formed respectively according to HVIGBT work principle, in addition, the carrier transport equations have been simplified for avoiding Kirk effect in BJT model. The transient model is realized in PSIM software in the paper. Extraction methods, which include estimation by empirical values, calculation by testing waveforms and comparison with same type models, are adopted in extracting model parameters. Through comparing testing and simulation waveforms, the model's simulation accuracy is proved.

关键词： Mathematical model Testing Semiconductor device modeling Transient analysis Insulated gate bipolar transistors Integrated circuit modeling Capacitance

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Probabilistic substation fault diagnosis considering instrumentation channels and heterogeneous information: A unified Bayesian network model

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Qinghua Daxue Xuebao/Journal of Tsinghua University 2014年第10期54卷 1384-1390页

作者： Mu, Jianan Sun, Hongbin Wu, Wenchuan Guo, Qinglai Zhang, Boming State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing100084 China

Fault diagnosis plays an important role in improving power network troubleshooting capability. Conducting local fault diagnosis in substations can make full and quick use of abundant local information. A substation fault diagnosis method was presented based on Bayesian network to adapt to a wealth of information and distributed autonomy under smart grid environment. The method is effective in dealing with uncertainties induced by malfunctions of protection relays and circuit breakers as well as instrumentation channel errors. Heterogeneous information available in substations, such as sequence of events (SOEs), wave records and blocking signals, was also integrated into the method, with the junction tree algorithm used to conduct probabilistic reasoning. The results show that breaker SOEs can be better utilized when considering instrumentation channels. Furthermore, introduction of wave records and blocking signals can significantly improve diagnosis accuracies. ©, 2014, Press of Tsinghua University. All right reserved.

关键词： Bayesian networks

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An adaptive wind power smoothing method with energy storage system

An adaptive wind power smoothing method with energy storage ...

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IEEE General Meeting power& Energy Society

作者： Hanchen Xu Can Wang Chao Lu Zhigang Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China Electric Power Research Institute of China Southern Power Grid Guangzhou China

The random and intermittent nature of wind power (WP) makes the integration of large-scale wind farms into power system problematic. The energy storage system (ESS) is an effective means to smooth the WP. This paper presents a novel Kalman filter (KF) based adaptive wind power smoothing method to determine the power output of an ESS. ESS capacity can be significantly reduced by adjusting the parameters of KF adaptively according to the WP fluctuation. Meanwhile, a fuzzy logic controller is introduced to manage the remained energy level (REL) of the ESS. By considering the current WP fluctuation, the REL and the power output of the ESS together in the controller, the REL can be successfully managed to a reasonable range without deteriorating the WP fluctuation. A test case based on data from an actual wind farm validated the effectiveness of the proposed method.

关键词： Fluctuations Wind power generation Energy storage Wind farms Kalman filters Fuzzy logic Smoothing methods

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Virtual flux based direct power control for three-level PWM rectifier 17

Virtual flux based direct power control for three-level PWM ...

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2014 17th International Conference on Electrical Machines and systems, ICEMS 2014

作者： Yingchao, Zhang Liping, Jin Yongchang, Zhang Ting, Lu Zhengming, Zhao Key Lab. of Special Power Supply of PLA Chongqing Communication Institute China North China University of Technology Power Electronics and Motor Drive Engineering Research Center China State Key Lab. of Control and Simulation of Power System and Generation Equipments Tsinghua University China

ISBN: (纸本)9781479951611

This paper presents a new control strategy for three-level neutral point clamped (NPC) pulse width modulated (PWM) rectifier without power source voltage sensors. The relationship between instantaneous power and voltage vectors is derived mathematically. Virtual flux is estimated and used to calculate the phase of the power source voltage and instantaneous power. On these bases, a direct power control (DPC) scheme for three-level PWM rectifier is presented. An optimal switching table is established, vector switching scheme and balance strategy for the neutral point potential are discussed. Variable switching frequency and dynamic process of the startup are also analyzed. Experimental results have verified the theoretical approach and the three-level PWM rectifier with proposed DPC based on virtual flux exhibits several advantages, such as simple algorithm, low costs and excellent dynamic performance. © 2014 IEEE.

关键词： Electric rectifiers

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Phase-Shift control of Isolated Bidirectional DC-DC Converters for Unidirectional power Flow

Phase-Shift Control of Isolated Bidirectional DC-DC Converte...

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IEEE Energy Conversion Congress and Exposition

作者： Junjie Ge Zhengming Zhao Junchao Ma Fanbo He Liqiang Yuan Ting Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University 100084 Beijing P. R. China

ISBN: (纸本)9781479957774

In the conventional phase-shift control of isolated bidirectional DC-DC converters, the phenomenon of power backflow is quite obvious. General improved phase-shift control methods can reduce the power backflow of the input. However, they do not take the power backflow of the output into consideration. In this paper, a novel phase-shift control of isolated bidirectional DC-DC converters for unidirectional power flow is proposed. It can eliminate the power backflows of both the input and the output at the same time. Furthermore, the converters in the proposed phase-shift control can achieve the zero-current switching in the whole power rang. Experimental results from a prototype verify the feasibility and validity of the proposed control method, and show superior performance.

关键词： DC-DC power converters Voltage control Load flow control systems Educational institutions Prototypes

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Application of the complex algorithm in PMU-only state estimaiton

Application of the complex algorithm in PMU-only state estim...

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International Conference on power system Technology (powerCON)

作者： Yunfeng Cheng Chao Lu Kun Men Liang Tu the State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghual University Beijinz P.R. China the Academy of China Southern Power Grid Guangzhou P.R. China

China's electrical grid has installed more than 2500 sets of phasor measurement unit (PMU), covering almost all the 500 kV and above and part of the 220 kV substations, which in sure observable of the ultra-high voltage power network and provide mass data for system analysis. However, PMU measurements may contain bad data and the precision of measurements especially phase need to be further improved. state estimation is an effective method to deal with data contaminated by noise and bias. Therefore, it's of great significance to study the PMU-only state estimation (POSE) problem. The real number equations based on the rectangular coordinate system and weighted least squares (WLS)algorithm are the general method to solve the POSE problem at present, which need to convert phasors into their real and imaginary parts, thus enlarging the size of the coefficient matrix which decreases the computational efficiency. In this paper, complex number equations for the POSE problem are established and the complex number weighted least squares (CWLS) estimation model is built to solve the equation directly in the complex domain which needs no phasor converting. The error characteristics of PMU measurements in the complex domain are analyzed in depth which give a guidance of choosing weights and illustrate the robustness of the CWLS to phase. Test results demonstrate the contrast analysis between the CWLS and the WLS from the perspectives of estimation time, estimation accuracy and adaptability to different error levels, which shows that the performances of the CWL Sare better than the WLS. The robustness of the CWLS to phase is also showed in the tests.

关键词： Phasor measurement units Measurement errors Measurement uncertainty Phase measurement Current measurement Voltage measurement Equations

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Development of a frequency dependent network equivalent based RTDS-TSA hybrid transient simulation platform with heterogeneous architecture

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Dianli Xitong Zidonghua/Automation of Electric power systems 2014年第16期38卷 88-93页

作者： Hu, Yizhong Wu, Wenchuan Zhang, Boming Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China

For the simulation of large-scale AC/DC hybrid systems, both the precision of the DC parts and the efficiency of the whole system should be considered. Thus a real-time hybrid transient simulation platform is proposed by combining the real-time digital simulator (RTDS) and a transient stability analysis (TSA) program. A latest GTFPGA card is used to realize the high speed digital communication between RTDS and the computer deploying TSA program. Moreover, the frequency dependent network equivalent (FDNE) is implemented in this simulation platform to improve the accuracy of simulation results. By simulating a modified New England 39-bus test system incorporating high-voltage direct current (HVDC) components, the validity of the proposed simulation platform is verified.

关键词： Transient analysis

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A look-ahead generation dispatch method considering discrete generation regulation constraints with large-scale wind power integration

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Dianli Xitong Zidonghua/Automation of Electric power systems 2014年第10期38卷 36-42页

作者： Li, Zhigang Wu, Wenchuan Zhang, Boming Sun, Hongbin Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China

Look-ahead generation dispatch is a critical measurement to accommodate large-scale integration of wind power generation. In real application, the model for conventional generators should involve generation regulation constraints including regulation frequency constraints and discrete output constraints. Look-ahead generation dispatch with regulation constraints is a large-scale nonlinear mixed-integer programming problem, and it could be hardly solved strictly within acceptable time. An efficient three-stage method for solving this problem is developed, together with a forward-backward-pass dynamic programming approach for handling generation regulation constraints. Numerical tests are taken on IEEE 31-bus systems and a large-scale 264-bus power system to verify the high efficiency and practicability of the proposed method.

关键词： Wind power

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Real-time charging optimization method considering vehicle charging prediction

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Dianli Xitong Zidonghua/Automation of Electric power systems 2014年第9期38卷 61-68页

作者： Li, Zhengshuo Guo, Qinglai Sun, Hongbin Xin, Shujun Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China

With large-scale electric vehicles (EVs) integrated into the power system, how to optimize EV charging power in real time to avoid incremental peak load and achieve valley-filling will be important. The regular real-time charging optimization as well as the vehicle charging prediction method is reviewed at first. Since vehicle charging (especially vehicle fleet charging) is predictable, a new real-time charging optimization model is proposed on the basis of the regular method with the consideration of the prediction model of incoming EVs. The new model is solved with receding horizon optimization, obtaining the current optimized charging power of plugged EVs. Through case study with various prediction accuracies, it can be seen that the proposed method always approaches the optimal solution to valley-filling. Moreover, compared with regular method, the proposed method would make a greater improvement of optimization result in the case of more diverse EV plug-in time. ©2014 state Grid Electric power Research Institute Press.

关键词： Forecasting

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