This paper presents two approaches for system-level simulation of force-balance accelerometers. The derivation of the system-level model is elaborated and simulation results are obtained from the implementation of tho...This paper presents two approaches for system-level simulation of force-balance accelerometers. The derivation of the system-level model is elaborated and simulation results are obtained from the implementation of those strategies on the fabricated silicon force-balance MEMS accelerometer. The mathematical model presented is implemented in VHDL- AMS and SIMULINK TM,respectively. The simulation results from the two approaches are compared and show a slight difference. Using VHDL-AMS is flexible,reusable,and more accurate. But there is not a mature solver developed for the language and this approach takes more time, while the simulation model can be easily built and quickly evaluated using SIMULINK.展开更多
A discontinuity of magnetic circuits according to the end effect is generated in the permanent magnet linear synchronous motor （PMLSM）. Due to the unbalanced back electro-motive force （EMF） and impedance produced,...A discontinuity of magnetic circuits according to the end effect is generated in the permanent magnet linear synchronous motor （PMLSM）. Due to the unbalanced back electro-motive force （EMF） and impedance produced, unbalanced current is generated. The cireulatin8 current, which is caused by a decrease in the thrust, is generated by the unbalanced current. The optimal design of auxiliary-teeth at the end of the mover was carried out to solve the unbalance of phase by using design of experiment （DOE）, and compared with the basic model through finite element analysis （FEA）. As a result, the auxiliary-teeth model compensates for the decrease of thrust caused by the unbalanced phase. Also, this model is proven to reduce the detent force by the vibration and noise of the PMLSM and copper loss caused by the circulating current.展开更多
This paper summarizes the development of hydro-projects in China,blended with an international perspective.It expounds major technical progress toward ensuring the safe construction of high dams and river harnessing,a...This paper summarizes the development of hydro-projects in China,blended with an international perspective.It expounds major technical progress toward ensuring the safe construction of high dams and river harnessing,and covers the theorization of uneven non-equilibrium sediment transport,inter-basin water diversion,giant hydro-generator units,pumped storage power stations,underground caverns,ecological protection,and so on.展开更多
Part of the difficulty in engineering education is to achieve aggregate theoretical knowledge to practice what therefore discourages the student. Trying to alleviate this difficulty, practical problems are created to ...Part of the difficulty in engineering education is to achieve aggregate theoretical knowledge to practice what therefore discourages the student. Trying to alleviate this difficulty, practical problems are created to encourage students to apply their knowledge in different ways; these problems can be computational order, resolved by programs through simulation, or physical, with the realization of models, prototypes, benches or interactive platforms with visual practical approach. From this, it was proposed to students of the Federal University of Pardi--Campus Tucurui through the Electric Power Systems and Mechanics Research Group, in order to apply knowledge arising from multidisciplinary fields of engineering in the construction of a prototype with reused materials and low cost enabling studies and analysis of vibrations in unbalanced motors. This system features an open source prototyping embedded platform Arduino to read values from the sensors used： accelerometers and potentiometers coupled to the engine, aiming to collect values and vary the supply voltage. The results are read by Arduino and computationally processed to be printed on an LCD display. Therefore, the aim of this is to provide an accessible way using simple techniques a prototype linking the theoretical and practical knowledge as the system of the bench that performs vibration analysis in an unbalanced motor interactively, and encourage research and development technologies in the Amazon region.展开更多
The authors treated 26 cases of dysequillibrium due tocerebellum or brain stem infarction byelectro-acupuncture from Aug 2000 - April 2002. Theresults were quite satisfactory and reported as follows.
This paper proposes the control of a grid side converter under unbalance voltage conditions for wind turbine system. The control technique is designed to operate under unbalance voltage by independent control between ...This paper proposes the control of a grid side converter under unbalance voltage conditions for wind turbine system. The control technique is designed to operate under unbalance voltage by independent control between positive and negative components. The converter will regulate the DC link voltage at the specific value （650 V）. To verify an operation of the proposed control, the simulation is conducted by MATLAB/SIMULINK program. The experiments are conducted on a 5 kW system composed of wind turbine simulator, machine side converter and the propose grid side converter for operation under unbalance voltage. By comparing the simulation experimentation results, it can be shown that the proposed control can be continuously operating through an extremely sag voltage without damage. Moreover the proposed control can deliver power to the grid and regulate DC link voltage under unbalance voltage.展开更多
This paper presents a new transient model ofa standalone （isolated） self excited induction generator （SEIG）. This model is based on direct phase quantities and is suitable to study the performance of the generator...This paper presents a new transient model ofa standalone （isolated） self excited induction generator （SEIG）. This model is based on direct phase quantities and is suitable to study the performance of the generator under any balanced or unbalanced conditions. It includes a general load as well as general excitation capacitor model. The model has the advantage of connecting or disconnecting the neutral points of the generator electrical system with both excitation capacitors and load. Furthermore, a more accurate magnetization curve is used. Moreover, the simulation results have been verified experimentally.展开更多
This paper presents practical distribution system equipment models such as various distributed generators, voltage regulators, and loads for fast three phase unbalanced load flow calculation in distribution systems. T...This paper presents practical distribution system equipment models such as various distributed generators, voltage regulators, and loads for fast three phase unbalanced load flow calculation in distribution systems. The method can calculate voltage and current of distribution systems, in which distributed generators are introduced. The calculation time of the proposed method is about 40 times faster than that of the Newton-Raphson method. Moreover, an introduction effect evaluation tool for distributed generators using the proposed three phase unbalanced load flow calculation is presented. It provides various functions such as a power system network diagram creation function and a voltage profile chart display function. Therefore, the introduction effect evaluation of distributed generators in distribution systems can be evaluated quite easily.展开更多
The unbalanced voltages cause negative effects on the doubly fed induction generator （DFIG） sucn as torque pulsation,and increased stator current. Based on the symmetrical component theory, the torque pulsation is t...The unbalanced voltages cause negative effects on the doubly fed induction generator （DFIG） sucn as torque pulsation,and increased stator current. Based on the symmetrical component theory, the torque pulsation is the consequence of the interaction of stator and rotor currents of different sequences. This paper presents a control technique to reduce the effect of unbalanced voltages on the DFIG in wind energy conversion systems. The negative sequence stator voltage is derived from the unbalanced three phase stator voltages. The compensated rotor voltage in terms of the derived negative sequence stator voltage and slip which minimizes the negative stator and rotor currents is proposed. The results from the simulation of control system with steady state model and dynamic model of the DFIG show that additional control loop with compensated voltage can significantly reduce torque and reactive power pulsations.展开更多
This paper presents a multiple target implementation technique for a doubly fed induction generator （DFIG） under unbalanced and distorted grid voltage based on direct power control （DPC）. Based on the mathematical...This paper presents a multiple target implementation technique for a doubly fed induction generator （DFIG） under unbalanced and distorted grid voltage based on direct power control （DPC）. Based on the mathematical model of DFIG under unbalanced and distorted voltage, the proportional and integral （PI） regulator is adopted to regulate the DFIG average active and reactive powers, while the vector P1 （VPI） resonant regulator is used to achieve three alternative control targets： （1） balanced and sinusoidal stator current; （2） smooth instantaneous stator active and reactive powers; （3） smooth electromagnetic torque and instantaneous stator reactive power. The major advantage of the proposed control strategy over the conventional method is that neither negative and harmonic sequence decomposition of grid voltage nor complicated control reference calculation is required. The insensitivity of the proposed control strategy to DFIG parameter deviation is analyzed. Finally, the DFIG experimental system is developed to validate the availability of the proposed DPC strategy under unbalanced and distorted grid voltage,展开更多
Thermoelectric effect is the most efficient way to convert electric energy directly from the temperature gradient. Thermoelectric effect-based power generation, cooling and heating devices are solid-stated, environmen...Thermoelectric effect is the most efficient way to convert electric energy directly from the temperature gradient. Thermoelectric effect-based power generation, cooling and heating devices are solid-stated, environmentally friendly, reliable, long-lived, easily maintainable, and easy to achieve miniaturization and integration. So they have unparalleled advantages in the aerospace, vehicle industry, waste heat recovery, electronic cooling, etc. This paper reviews the progress in thermodynamic analyses and optimizations for single- and multiple-element, single- and multiple-stage, and combined thermoelectric generators, thermoelectric refrigerators and thermoelectric heat pumps, especially in the aspects of non-equilibrium thermodynamics and finite time thermodynamics. It also discusses the developing trends of thermoelectric devices, such as the heat sources of thermoelectric generators, multi-stage thermoelectric devices, combined thermoelectric devices, and heat transfer enhancement of thermoelectric devices.展开更多
文摘This paper presents two approaches for system-level simulation of force-balance accelerometers. The derivation of the system-level model is elaborated and simulation results are obtained from the implementation of those strategies on the fabricated silicon force-balance MEMS accelerometer. The mathematical model presented is implemented in VHDL- AMS and SIMULINK TM,respectively. The simulation results from the two approaches are compared and show a slight difference. Using VHDL-AMS is flexible,reusable,and more accurate. But there is not a mature solver developed for the language and this approach takes more time, while the simulation model can be easily built and quickly evaluated using SIMULINK.
基金supported by the Second Stage of Brain Korea 21 Projects and Changwon National University in 2009-2010
文摘A discontinuity of magnetic circuits according to the end effect is generated in the permanent magnet linear synchronous motor （PMLSM）. Due to the unbalanced back electro-motive force （EMF） and impedance produced, unbalanced current is generated. The cireulatin8 current, which is caused by a decrease in the thrust, is generated by the unbalanced current. The optimal design of auxiliary-teeth at the end of the mover was carried out to solve the unbalance of phase by using design of experiment （DOE）, and compared with the basic model through finite element analysis （FEA）. As a result, the auxiliary-teeth model compensates for the decrease of thrust caused by the unbalanced phase. Also, this model is proven to reduce the detent force by the vibration and noise of the PMLSM and copper loss caused by the circulating current.
文摘This paper summarizes the development of hydro-projects in China,blended with an international perspective.It expounds major technical progress toward ensuring the safe construction of high dams and river harnessing,and covers the theorization of uneven non-equilibrium sediment transport,inter-basin water diversion,giant hydro-generator units,pumped storage power stations,underground caverns,ecological protection,and so on.
文摘Part of the difficulty in engineering education is to achieve aggregate theoretical knowledge to practice what therefore discourages the student. Trying to alleviate this difficulty, practical problems are created to encourage students to apply their knowledge in different ways; these problems can be computational order, resolved by programs through simulation, or physical, with the realization of models, prototypes, benches or interactive platforms with visual practical approach. From this, it was proposed to students of the Federal University of Pardi--Campus Tucurui through the Electric Power Systems and Mechanics Research Group, in order to apply knowledge arising from multidisciplinary fields of engineering in the construction of a prototype with reused materials and low cost enabling studies and analysis of vibrations in unbalanced motors. This system features an open source prototyping embedded platform Arduino to read values from the sensors used： accelerometers and potentiometers coupled to the engine, aiming to collect values and vary the supply voltage. The results are read by Arduino and computationally processed to be printed on an LCD display. Therefore, the aim of this is to provide an accessible way using simple techniques a prototype linking the theoretical and practical knowledge as the system of the bench that performs vibration analysis in an unbalanced motor interactively, and encourage research and development technologies in the Amazon region.
文摘The authors treated 26 cases of dysequillibrium due tocerebellum or brain stem infarction byelectro-acupuncture from Aug 2000 - April 2002. Theresults were quite satisfactory and reported as follows.
文摘This paper proposes the control of a grid side converter under unbalance voltage conditions for wind turbine system. The control technique is designed to operate under unbalance voltage by independent control between positive and negative components. The converter will regulate the DC link voltage at the specific value （650 V）. To verify an operation of the proposed control, the simulation is conducted by MATLAB/SIMULINK program. The experiments are conducted on a 5 kW system composed of wind turbine simulator, machine side converter and the propose grid side converter for operation under unbalance voltage. By comparing the simulation experimentation results, it can be shown that the proposed control can be continuously operating through an extremely sag voltage without damage. Moreover the proposed control can deliver power to the grid and regulate DC link voltage under unbalance voltage.
文摘This paper presents a new transient model ofa standalone （isolated） self excited induction generator （SEIG）. This model is based on direct phase quantities and is suitable to study the performance of the generator under any balanced or unbalanced conditions. It includes a general load as well as general excitation capacitor model. The model has the advantage of connecting or disconnecting the neutral points of the generator electrical system with both excitation capacitors and load. Furthermore, a more accurate magnetization curve is used. Moreover, the simulation results have been verified experimentally.
文摘This paper presents practical distribution system equipment models such as various distributed generators, voltage regulators, and loads for fast three phase unbalanced load flow calculation in distribution systems. The method can calculate voltage and current of distribution systems, in which distributed generators are introduced. The calculation time of the proposed method is about 40 times faster than that of the Newton-Raphson method. Moreover, an introduction effect evaluation tool for distributed generators using the proposed three phase unbalanced load flow calculation is presented. It provides various functions such as a power system network diagram creation function and a voltage profile chart display function. Therefore, the introduction effect evaluation of distributed generators in distribution systems can be evaluated quite easily.
文摘The unbalanced voltages cause negative effects on the doubly fed induction generator （DFIG） sucn as torque pulsation,and increased stator current. Based on the symmetrical component theory, the torque pulsation is the consequence of the interaction of stator and rotor currents of different sequences. This paper presents a control technique to reduce the effect of unbalanced voltages on the DFIG in wind energy conversion systems. The negative sequence stator voltage is derived from the unbalanced three phase stator voltages. The compensated rotor voltage in terms of the derived negative sequence stator voltage and slip which minimizes the negative stator and rotor currents is proposed. The results from the simulation of control system with steady state model and dynamic model of the DFIG show that additional control loop with compensated voltage can significantly reduce torque and reactive power pulsations.
基金Project supported by the National High-Tech R&D Program(863)of China(No.2011AA050204)the National Natural Science Foundation of China(No.51277159)
文摘This paper presents a multiple target implementation technique for a doubly fed induction generator （DFIG） under unbalanced and distorted grid voltage based on direct power control （DPC）. Based on the mathematical model of DFIG under unbalanced and distorted voltage, the proportional and integral （PI） regulator is adopted to regulate the DFIG average active and reactive powers, while the vector P1 （VPI） resonant regulator is used to achieve three alternative control targets： （1） balanced and sinusoidal stator current; （2） smooth instantaneous stator active and reactive powers; （3） smooth electromagnetic torque and instantaneous stator reactive power. The major advantage of the proposed control strategy over the conventional method is that neither negative and harmonic sequence decomposition of grid voltage nor complicated control reference calculation is required. The insensitivity of the proposed control strategy to DFIG parameter deviation is analyzed. Finally, the DFIG experimental system is developed to validate the availability of the proposed DPC strategy under unbalanced and distorted grid voltage,
基金supported by the National Natural Science Foundation of China(Grant Nos.11305266&51576207)the National Basic Research Program of China("973"Project)(Grant No.2012CB720405)
文摘Thermoelectric effect is the most efficient way to convert electric energy directly from the temperature gradient. Thermoelectric effect-based power generation, cooling and heating devices are solid-stated, environmentally friendly, reliable, long-lived, easily maintainable, and easy to achieve miniaturization and integration. So they have unparalleled advantages in the aerospace, vehicle industry, waste heat recovery, electronic cooling, etc. This paper reviews the progress in thermodynamic analyses and optimizations for single- and multiple-element, single- and multiple-stage, and combined thermoelectric generators, thermoelectric refrigerators and thermoelectric heat pumps, especially in the aspects of non-equilibrium thermodynamics and finite time thermodynamics. It also discusses the developing trends of thermoelectric devices, such as the heat sources of thermoelectric generators, multi-stage thermoelectric devices, combined thermoelectric devices, and heat transfer enhancement of thermoelectric devices.
