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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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Experimental investigation and analysis for gearbox fault

Experimental investigation and analysis for gearbox fault

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2010 2nd World Non-Grid-Connected Wind power and Energy Conference, WNWEC 2010

作者： Li, Shaohua Jiang, Dongxiang Zhao, Minghao State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781424489213

As an important component of a wind turbine drive chain, the high failure rate of the gearbox can have a serious impact on the operation of wind turbine units. The fault diagnosis of the gearbox is therefore important for the safety of wind turbine units. In this paper, a gearbox experiment rig was built, experiments on the gear surface spalling fault were held on the rig under laboratory conditions, the shaft vibration displacement signals were collected, related vibration signals were analyzed by time domain, amplitude domain, frequency domain and wavelet analysis, and the results of different analysis methods were compared. The results show that the waveform of normal and fault signals are similar, the amplitude of the signals will change while the fault happens, and the wavelet analysis is more effective than frequency domain analysis on gearbox fault features extraction. © 2010 IEEE.

关键词： Frequency domain analysis

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Design, simulation and analysis of the low stray inductance bus bar for voltage source inverters

Design, simulation and analysis of the low stray inductance ...

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2011 International Conference on Electrical Machines and systems, ICEMS 2011

作者： Yuan, Liqiang Yu, Hualong Wang, Xuesong Zhao, Zhengming State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781457710445

Hard-switching technique under the high voltage and high current is one of main trends of high power inverters. Under this switching mode, the stray parameters of the commutating loops, especially the stray inductance of the DC bus bar, have significant influence on the switching process, electromagnetic interference and component stress of the semiconductor switches. It becomes one of the key points for the safe operation of inverters. Based on an actual 55kW inverter, the design, simulation and analysis for its bus bar is described in this paper. The bus bar model is built with the method of Partial Element Equivalent Circuit (PEEC), and the stray parameters are extracted from PEEC model and applied in the circuit simulation. Compared with the experimental results, the modeling validity is proved, and the simplified modeling process and design principles for complex physical bus bar are presented. © 2011 IEEE.

关键词： Circuit simulation

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Electromagnetic and Mechanical Transmission Role of Poles in vibration of PMDC motor

Electromagnetic and Mechanical Transmission Role of Poles in...

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2022 International Conference on Electrical Machines, ICEM 2022

作者： Wang, S.M. Gu, Z.Q. Hong, J.F. Yang, Z.L. Tsinghua University State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Beijing100084 China

ISBN: (数字)9781665414326

ISBN: (纸本)9781665414326

In this paper, the pivot role of permanent-magnet pole in the electromagnetic and mechanical transfer process of the vibration in PMDC motor is clarified, and the transfer function is established to describe the transfer process of electromagnetic force from the bottom of the magnetic pole to the stator yoke. The expression of radial electromagnetic force in air-gap is analytically calculated, the characteristics of harmonic components are obtained, and the reason why high order force density produces low order concentrated force and bending moment is explained. Based on the characteristics of harmonics, the relationship between the polar arc coefficient and concentrated force or bending moment is explained. Finally, the key role of magnetic poles in the vibration transmission of PMDC motor is summarized. © 2022 IEEE.

关键词： Bending moments

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A predictive DC voltage control scheme for back-to-back converters based on energy balance modeling

A predictive DC voltage control scheme for back-to-back conv...

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2011 International Conference on Electrical Machines and systems, ICEMS 2011

作者： Yin, Lu Zhao, Zhengming Lu, Ting He, Fanbo Yuan, Liqiang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781457710445

This paper presents a predictive control scheme of DC-link voltage for back-to-back converters based on energy balance modeling. Since the variation of DC-link voltage is affected by the energy mismatch between rectifier and inverter, the energy distribution in a rectifier-inverter is analyzed. Moreover, in order to calculate the input and output energy in one control period accurately, the grid current is regulated by predictive control and the instantaneous active power consumed by the induction motor is estimated. Then, an equation based on energy balance in one control period is established, and the DC-link voltage can be controlled by solving it. Finally, simulation results show that with the proposed control scheme, the back-to-back converter exhibits both good dynamic and steady-state performances. © 2011 IEEE.

关键词： Energy balance

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control of parallel grid-connected photovoltaic inverters with common dc bus

Control of parallel grid-connected photovoltaic inverters wi...

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2nd IET Renewable power generation Conference, RPG 2013

作者： He, F. Zhao, Z. Yuan, L. Lu, T. State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781849197588

This paper proposes a hierarchical control scheme for parallel grid-connected PV inverters with a common dc bus. Droop control and group coordination are implemented to achieve equal power sharing between inverters as well as zero steady-state error for dc voltage regulation. The implementation is specifically designed for distributed control to promote modularization and system reliability. Experimental results have verified that the proposed scheme is effective.

关键词： Electric power transmission networks

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Machine condition classification using deterioration feature extraction and anomaly determination

Machine condition classification using deterioration feature...

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作者： Jiang, Dongxiang Liu, Chao State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing 100084 China

Condition classification has been widely used for assessing equipment status for machine condition monitoring and diagnostics. An engine was fitted with one temperature and two pressure sensors to study the machine conditions in prognostics with an added abnormal state, in addition to the conventional normal and failure states. This work enables a better classification capability in order to predict deterioration in the engine. Information related to three deterioration processes was collected, and preprocessed using singular point elimination, deviation value acquisition, and data normalization. Wavelet transforms were used to extract deterioration features with different mother wavelets. The mother wavelets were selected using t tests to optimize the wavelet selection. The deterioration was related to the amount of anomaly, with the abnormal states defined to distinguish the functional from the failure states. A Learning Vector Quantization (LVQ) neural network was used to classify the machine conditions, including normal, abnormal, and failure states. The results showed that the deterioration features defined using the Daubechies wavelet (db8) most strongly correlated with the original signal, so that the classification accuracy based on the deterioration features was greatly improved. The LVQ classification system had good accuracy for machine condition classification, and was adaptable to various engine conditions. © 2010 IEEE.

关键词： Deterioration

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Accelerating exploitation and integration of global renewable energy

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Innovation 2025年

作者： Wang, Jianxiao Chen, Xinjiang Zhuang, Minghao Li, Yan Ruan, Ziwen Wang, Yuhan Zhang, Ning Song, Jie He, Kebin Lu, Xi National Engineering Laboratory for Big Data Analysis and Applications Peking University Beijing100871 China Department of Industrial Engineering and Management College of Engineering Peking University Beijing100871 China Peking University Ordos Research Institute of Energy Ordos017000 China State Key Laboratory of Nutrient Use and Management College of Resources and Environmental Sciences China Agricultural University Beijing100193 China College of Environmental Science and Engineering Tongji University Shanghai200092 China School of Environment State Key Joint Laboratory of Environment Simulation and Pollution Control Tsinghua University Beijing100084 China State Key Lab of Power Systems Department of Electrical Engineering Tsinghua University Beijing100084 China Institute for Carbon Neutrality Tsinghua University Beijing100084 China

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A systematic and qualitative assessment method and software design for energy efficiency of typical electric machine systems with pumps and fans

A systematic and qualitative assessment method and software ...

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11th International Conference on Electrical Machines and systems, ICEMS 2008

作者： Yi, Lei Zhengming, Zhao Jing, Xue State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9787506292214

Three-phase induction motors as well as power converters are intrinsically efficient machines and devices. However, due to the common misapplication of them with loads like pumps and fans, these electric machine systems are considered a great potential of energy conservation in industries. As to assessing methods of energy conservation, neither the study of induction machine efficiency nor the analysis of pumps and fans performance is new. However, the systematic and qualitative analysis and assessment of the energy efficiency of induction machines, loads and control devices acting as a whole system are still complicated yet indispensable for electric machine system energy conservation program in China. In this paper, a systematic and qualitative assessment method for energy application efficiency of electric machine system is raised. Based on this method, an assessing computer program is designed to provide referencing information for making investment decisions regarding energy efficiency measures at manufacturing plants. An expert system is also designed to choose equipments that match each other.

关键词： Investments

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Series-connected HV-IGBTs using active voltage control with status feedback circuit

Series-connected HV-IGBTs using active voltage control with ...

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作者： Ji, Shiqi Lu, Ting Zhao, Zhengming Yu, Hualong Yuan, Liqiang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China

ISBN: (纸本)9781479956982

The transient voltage unbalance is the major problem that limits the application of series-connected IGBTs in high voltage and high power converters. The asynchronous gate delay which causes that series-connected IGBTs do not turn-on and turn-off at the same time results in the most serious unbalanced voltage sharing. The active voltage control technique is proposed in this paper to solve the asynchronous gate delay problem. By sampling the feedback signal caused by unbalanced voltage, the microcontroller generates a time delay for gate driver to compensate the asynchronous gate delay. The most vital part of active voltage control is the status feedback circuit which is also given in detail in this paper. The function of the status feedback circuit and the effect of active voltage control are verified in a two series-connected HV-IGBTs platform in rated operation (5kV bus voltage and 600A load current). © 2014 IEEE.

关键词： Insulated gate bipolar transistors (IGBT)

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