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International Conference on Electrical Machines and systems (ICEMS)

作者： Chao Liu Zhengming Zhao Ting Lu Liqiang Yuan Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

Grid-connected LCL filter of voltage source PWM rectifier (VSR) can not only reduce the values of inductance, improve the system dynamic response, but also reduce the cost. However, LCL filter brings stability problem if no damping method is adopted. In order to guarantee the stability and high power factor of VSR at the same time, active damping control method rather than reactive damping method is required. Nowadays, the study on LCL filter is just for two-level VSR. In this paper, parameter design and damping method are being placed in three-level VSR for widely use. For a three-level PWM rectifier, a new parameter design method as well as active damping method is proposed and verified by Matlab-Simulink simulation and experiment.

关键词： Rectifiers Damping power harmonic filters Pulse width modulation Inductors Resistors Voltage control

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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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International Conference on Electrical Machines and systems (ICEMS)

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

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.

关键词： Voltage control Induction motors Rectifiers Capacitors Vectors Pulse width modulation Inverters

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Optimal design of the back-to-back IGBT-based converter with the concept of systematic safe operating area

Optimal design of the back-to-back IGBT-based converter with...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Gaoyu Zou Zhengming Zhao Liqiang Yuan Xuesong Wang Ting Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

The key parameters of SOA (safe operating area) of semiconductor devices are hard to be measured when converter is operating, which is not helpful to protect converter at any time. On the other hand, surplus estimating method is widely used to design the main circuit. In order to guarantee the whole system works safely and improve utilization rate of devices, the concept of SSOA (systematic safe operating area) is presented. By determining the relationship of key parameters between devices and converter, the expression of SSOA is described quantitatively. Then it is implemented as a basic rule to design a back-to-back converter based on IGBT for 55kW induction motor optimally. Rated value of DC-link voltage and grid filter of the system is obtained reasonably as well.

关键词： Inductance Insulated gate bipolar transistors Rectifiers power harmonic filters Semiconductor optical amplifiers Induction motors

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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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International Conference on Electrical Machines and systems (ICEMS)

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

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 55 kW 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.

关键词： Integrated circuit modeling Equivalent circuits Inductance Inverters Capacitance Conductors Analytical models

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Effects of nonlinear gradient index on radiative heat transfer in a one-dimensional medium by the DRESOR method

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Journal of Physics: Conference Series 2012年第1期369卷

作者： Z C Wang Q Cheng G H Wang Z F Huang H C Zhou State Key Laboratory of Coal Combustion Huazhong University of Science and Technology Wuhan 430074 Hubei People's Republic of China State Key Laboratory of Control & Simulation of Power System & Generation Equipment Department of Thermal Engineering Tsinghua University Beijing 10084 P. R. China To whom any correspondence should be addressed

The DRESOR (Distribution of Ratios of Energy Scattered by the medium Or Reflected by the boundary surface) method is applied for radiative heat transfer in a one-dimensional medium with a nonlinear gradient index and gray boundary surfaces. In this proposed method, the DRESOR values calculated by the Monte Carlo method express quantitatively the impact of scattering on radiative transfer and the radiative intensity with high directional resolution of high precision can be easily obtained. With given media characteristics and boundary conditions, the temperature and radiative flux distributions inside the medium are calculated under the condition of radiative equilibrium. It is shown, in the cases studied, that the DRESOR method has a good accuracy. The temperature distributions have a node with different kinds of sine changed gradient index distributions under the same boundary emissivity. The impact of the gradient index on the radiative heat transfer is considerable, and the same as that of the ratios of its amplitude and average index. Besides, the effects of optical thickness, boundary emissivity and scattering phase function on radiative transfer also should be paid adequate attention.

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Modeling and analysis of MW-level grid-connected PV plant

Modeling and analysis of MW-level grid-connected PV plant

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Annual Conference of Industrial Electronics Society

作者： Yi Lei Zhengming Zhao Wei Xu Jianguo Zhu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China School of Electrical Mechanical and Mechatronic Systems University of Technology Sydney Australia

This paper focuses on the modeling and analysis of the basic composition, characteristic and the interactions with grid for megawatt (MW)-level large scale grid-connected photovoltaic (PV) plants. For a MW-level PV plant, numbers of inverters with relatively smaller capacity are employed to operated in parallel. When the irradiance on the large area of PV array is not equal, the output power verses the voltage of the PV array will have several peak values and affect the maximal power tracking. LCL filters are adopted for filtering the harmonics generated by inverters, but due to its inherent resonance character, additional damping strategy is required. The power quantity of harmonics and voltage fluctuation may occur when one MW-level PV plant is connected to grid. For these characteristics, with the modeling and simulation of a real MW-level PV plant, this paper proposed and verified a novel method toward MPPT of large area PV arrays. The parallel running of inverters and grid voltage fluctuation are also simulated. Finally, the interaction with the grid voltage fluctuation is explored in detail.

关键词： Inverters Arrays Photovoltaic systems Fluctuations Voltage fluctuations

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An Improved Virtual Resistance Damping Method for Grid-Connected Inverters with LCL Filters

An Improved Virtual Resistance Damping Method for Grid-Conne...

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2011 IEEE Energy Conversion Congress and Exposition (ECCE 2011)

作者： Yi Lei Zhengming Zhao Fanbo He Sizhao Lu Lu Yin 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)9781457705427;9781457705410

In renewable energy generations, LCL filters are commonly used to connect in series with the output ports of the converter to smooth the currents flowing into the grid due to their enhanced attenuation ability and smaller inductance compared to single L filters. However, the inherent resonance of an LCL filter makes the control of such a system challenging, and different passive and active damping strategies have been developed till now. This paper aims to the damping problems of LCL filters and proposes a new approach to realize active damping. Based on traditional virtual resistance damping strategy, the new algorithm employs a lead compensation block in the capacitor current feedback loop so as to alleviate the impact of control delay. It is easy to be transformed from conventional virtual resistance damping method since just an additional digital filter is needed. Theoretical analyses for the essence equivalent relationship between passive damping and virtual resistance damping, as well as the impact investigation of control delay are made in details. The results show that the traditional virtual resistance active damping method is equivalent to passive damping of connecting damping resistance in parallel with the capacitor in the control block diagram, while the proposed virtual resistance active damping method is equivalent to passive damping of connecting damping resistance in series with the capacitor in the control block diagram. Both simulation and experimental results have verified the feasibility.

关键词： absorption of shock BLOCK DIAGRAM Capacitors Filters Virtual Equivalent damping force control block

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Study on the loss reduction of high-efficient high-voltage series induction motors

Study on the loss reduction of high-efficient high-voltage s...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Bai Lingyun Zhao Zhengming Lei Yi Wang Shuping State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China Anhui Electrical Research Institute Hefei China

On the basis of analyzing the composition of losses in high-efficient high-voltage asynchronous motors, the approaches of increasing the efficiency of the motors is investigated in this paper. The approaches concern with the improvement of material, winding, fan, magnetic groove and so on. By taking the economy and efficiency into account synthetically, the design of the YKK series induction motors is carried on, and it is realized by software simulation.

关键词： Magnetic flux Windings Induction motors Rotors Perpendicular magnetic anisotropy Copper

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Effect of Different Arresters on Switching Overvoltages in UHV Transmission Lines

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Tsinghua Science and Technology 2010年第3期15卷 325-328页

作者：杨鹏程陈水明何金良 State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua University

The amplitude of switching overvoltages is a key factor for designing the insulation of UHV equipment. The effect of different arresters needs to be studied, since installing arresters is an important way to suppress switching overvoltages in UHV transmission lines. Switching overvoltages on the 1000 kV Huainan-Huxi double-circuit transmission line were simulated for different operating modes and different arrester designs using the electromagnetic transient program PSCAD/EMTDC. With parallel resistors, the switching overvoltages are less than 1.70 p.u. （1.0 p.u.=1100×√ 2 /√3 kV）. If the arrestors are better, the switching overvoltages can be reduced even lower to 1.55 p.u. Without parallel resistors, the arresters can reduce three-phase energizing overvoltages to 1.70 p.u, while the single-phase reclosing overvoltages still exceed the limit. The results show that the parallel resistors cannot be eliminated if the arresters are only installed at each end of the transmission line. Also, better quality arresters significantly lower the switching overvoltages.

关键词： UHV double-circuit transmission line switching overvoltages arresters

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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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