Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width mo...Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width modulation (SPWM) inverters with low harmonyic content in theory.The THD value would be increased by switching time delay of power devices and control circuit. A new control coecuit with delay time compensation is presented in this paper. With this control scheme, the output of the inverter could be basically identified with the theory given.Test results of experimental circuit verify that the control circuit presented in this paper is feasible. The THD of the inverter output voltage could be reduced to a certain extent by this method.展开更多
The paper deals with analysis and synthesis of non-harmonic and non-linear sources and appliances, and their interaction with harmonic power supply network. Basic idea is based on knowledge of harmonic spectrum of the...The paper deals with analysis and synthesis of non-harmonic and non-linear sources and appliances, and their interaction with harmonic power supply network. Basic idea is based on knowledge of harmonic spectrum of the sources and/or appliances, respectively. Obviously, one need to know voltage harmonic components of voltage sources (renewable with inverters,...), and current harmonic components generated by non-linear appliances (rectifiers,...). Method of investigation lies on decomposition of real electric circuit into n-harmonic separated equivalent schemes for each harmonic component. Then transient analysis will be done for each scheme separately using "impedance harmonic matrices". The important fact is that each equivalent scheme is now linearized and therefore easily calculated. Finally, the effects of each investigated schemes arc summed into resulting quantities of real non-linear electric circuit.展开更多
A new type of compact terahertz (THz) radiation source using free electron laser (FEL) is discussed in this paper.The concept machine consists of an independently tunable cell thermionic RF gun (ITC-RF Gun),an acceler...A new type of compact terahertz (THz) radiation source using free electron laser (FEL) is discussed in this paper.The concept machine consists of an independently tunable cell thermionic RF gun (ITC-RF Gun),an accelerating structure with symmetry RF-incoupler and a coaxial load RF-outcoupler,an undulator combined with an optical resonance cavity of hole-coupling mode.Withoutα-magnet and other bunch compressors,the size of this machine is decreased.The conceptual design and numerical simulation are presented.展开更多
An active-RC low-pass filter of 5MHz cutoff frequency with a tuning architecture is proposed. It is implemented in 0. 18μm standard CMOS technology. The accuracy of the tuning system is improved to be within ( - 1.2...An active-RC low-pass filter of 5MHz cutoff frequency with a tuning architecture is proposed. It is implemented in 0. 18μm standard CMOS technology. The accuracy of the tuning system is improved to be within ( - 1.24%, + 2.16%) in measurement. The chip area of the tuning system is only a quarter of that of the main-filter. After tuning is completed, the tuning system will be turned off automatically to save power and to avoid interference. The in-band 3rd order harmonic input intercept point (IIP3) is larger than 16. ldBm, with 50Ω as the source impedance. The input referred noise is about 36μVrms The measured group delay variation of the filter between 3 and 5MHz is only 24ns,and the filter power consump- tion is 3.6roW. This filter with the tuning system is realized easily and can be used in many wireless low-IF receiver applications, such as global position systems (GPS), global system for mobile communications (GSM) and code division multiple access (CDMA) chips.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
The structure-property relationships in Ba0.4Sr0.6Ti1-ySiyO3 with y=0.00,0.01,0.02,0.05,0.10 and 0.20 ceramics have been studied by using X-ray diffraction,electron microscopy and dielectric spectroscopy.An increase o...The structure-property relationships in Ba0.4Sr0.6Ti1-ySiyO3 with y=0.00,0.01,0.02,0.05,0.10 and 0.20 ceramics have been studied by using X-ray diffraction,electron microscopy and dielectric spectroscopy.An increase of Si concentration is not favorable for the stability of the perovskite structure,which results in the formation of BaTiSiO5 secondary phase.The dielectric peaks of samples are suppressed,broadened and shifted to low temperature with increasing Si concentration.Permittivity and Q value are reduced gradually with increasing Si concentration,due to growing of second BaTiSiO5 phase.The tunability(T) still remains ~18.0% under 60 kV/cm biasing for the samples with y-0.10.The best combination of microwave dielectric properties are obtained for the composition of y=0.10:-=531,Q=391(at 1.610 GHz) and T=17.7%.展开更多
文摘Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width modulation (SPWM) inverters with low harmonyic content in theory.The THD value would be increased by switching time delay of power devices and control circuit. A new control coecuit with delay time compensation is presented in this paper. With this control scheme, the output of the inverter could be basically identified with the theory given.Test results of experimental circuit verify that the control circuit presented in this paper is feasible. The THD of the inverter output voltage could be reduced to a certain extent by this method.
文摘The paper deals with analysis and synthesis of non-harmonic and non-linear sources and appliances, and their interaction with harmonic power supply network. Basic idea is based on knowledge of harmonic spectrum of the sources and/or appliances, respectively. Obviously, one need to know voltage harmonic components of voltage sources (renewable with inverters,...), and current harmonic components generated by non-linear appliances (rectifiers,...). Method of investigation lies on decomposition of real electric circuit into n-harmonic separated equivalent schemes for each harmonic component. Then transient analysis will be done for each scheme separately using "impedance harmonic matrices". The important fact is that each equivalent scheme is now linearized and therefore easily calculated. Finally, the effects of each investigated schemes arc summed into resulting quantities of real non-linear electric circuit.
文摘A new type of compact terahertz (THz) radiation source using free electron laser (FEL) is discussed in this paper.The concept machine consists of an independently tunable cell thermionic RF gun (ITC-RF Gun),an accelerating structure with symmetry RF-incoupler and a coaxial load RF-outcoupler,an undulator combined with an optical resonance cavity of hole-coupling mode.Withoutα-magnet and other bunch compressors,the size of this machine is decreased.The conceptual design and numerical simulation are presented.
文摘An active-RC low-pass filter of 5MHz cutoff frequency with a tuning architecture is proposed. It is implemented in 0. 18μm standard CMOS technology. The accuracy of the tuning system is improved to be within ( - 1.24%, + 2.16%) in measurement. The chip area of the tuning system is only a quarter of that of the main-filter. After tuning is completed, the tuning system will be turned off automatically to save power and to avoid interference. The in-band 3rd order harmonic input intercept point (IIP3) is larger than 16. ldBm, with 50Ω as the source impedance. The input referred noise is about 36μVrms The measured group delay variation of the filter between 3 and 5MHz is only 24ns,and the filter power consump- tion is 3.6roW. This filter with the tuning system is realized easily and can be used in many wireless low-IF receiver applications, such as global position systems (GPS), global system for mobile communications (GSM) and code division multiple access (CDMA) chips.
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 Basic Research Program of China ("973" Project) (Grant No. 2009CB623302)
文摘The structure-property relationships in Ba0.4Sr0.6Ti1-ySiyO3 with y=0.00,0.01,0.02,0.05,0.10 and 0.20 ceramics have been studied by using X-ray diffraction,electron microscopy and dielectric spectroscopy.An increase of Si concentration is not favorable for the stability of the perovskite structure,which results in the formation of BaTiSiO5 secondary phase.The dielectric peaks of samples are suppressed,broadened and shifted to low temperature with increasing Si concentration.Permittivity and Q value are reduced gradually with increasing Si concentration,due to growing of second BaTiSiO5 phase.The tunability(T) still remains ~18.0% under 60 kV/cm biasing for the samples with y-0.10.The best combination of microwave dielectric properties are obtained for the composition of y=0.10:-=531,Q=391(at 1.610 GHz) and T=17.7%.