The existing liability division methods for harmonic pollution are either inexplicit or incomplete in physical meaning. To compensate these defects, two new methods are proposed based on line-transferred power compone...The existing liability division methods for harmonic pollution are either inexplicit or incomplete in physical meaning. To compensate these defects, two new methods are proposed based on line-transferred power components in this paper. At first, all harmonic sources are represented by ideal equivalent current source, line current components and bus voltage components of a source are determined by stimulation of this source with all other sources disabled. Then, the line-trans- ferred power component owing to a source under all sources action together is determined by the theory of line-transferred power components, and called source’s line-transferred power component. At last, the liability of a source for line-end harmonic pollution is divided by two methods: the ration of the source’s line-transferred active power component to the total line-transferred power, and the ration of projection of the source’s line-transferred complex power component to absolute value of the total line-transferred complex power. These two methods are taken into account not only harmonic voltage but also harmonic current in the liability division. Simulation results show that the proposed liability division method based on active power component is the most effective and ideal one.展开更多
This multilevel inverter methodology is the center of focus among researchers in recent era.It has been focused due to its advantages over existing topologies,drawbacks and improvement of power quality,Multi-level inv...This multilevel inverter methodology is the center of focus among researchers in recent era.It has been focused due to its advantages over existing topologies,drawbacks and improvement of power quality,Multi-level inverter has the ability to generate nearly sinusoidal waves.This sinusoidal wave can be further improved by increasing the level of output voltage or with the help of filter design,and this manuscript presents single-phase Multi cell Multi-Level Inverter(MLI).It has been considered for reducing component count to get a higher number of output voltage levels and lower Total harmonics distortion profile.It comprises with four symmetric DC input voltage and 10 IGBT switches to produces stepped output of 9 level,and when deploy asymmetric Dc voltage source the same circuit will produce 31 level output with some changes in firing scheme,moreover this circuit is the family of cascaded hybrid bridge inverter so this circuit covered advantage of CHB MLI,This circuit uses lower no.of switch as compared to existing conventional MLIs such as FC-MLI,CHB-MLI,NPC-MLI,This paper also provides one of most pertinent controls and modulation mechanisms for a MLI using a hybrid reference/carrier-oriented sinusoidal PWM mechanism.At last,simulated outcomes are to validate the performance of both architectures in MLI structure as well as verify the concept.展开更多
In recent years, the increasing application of nonlinear and unbalanced electronic equipment and large single phase loads have made voltage imbalance a serious problem in power distribution systems. A novel approach h...In recent years, the increasing application of nonlinear and unbalanced electronic equipment and large single phase loads have made voltage imbalance a serious problem in power distribution systems. A novel approach has been proposed to eliminate voltage imbalance and disturbances. The main strategy of this scheme is based on series active filter. By improving control circuit toward existing schemes and proposing a new strategy to control the voltage amplitude, simultaneous elimination of voltage imbalance, faults, voltage harmonics and also compensation of voltage drop in transmission lines become possible. Eventually, the voltage on the load side is a perfectly balanced three phase voltage with specific proper amplitude. The proposed scheme has been simulated in a test network and the results show high capability of this scheme for the complete elimination of imbalance without phase shift.展开更多
Multilevel inverters have gained much attention for its operation involving applications ranging values of high power rating. This paper proposes a switching topology for asymmetric multilevel inverter utilizing less ...Multilevel inverters have gained much attention for its operation involving applications ranging values of high power rating. This paper proposes a switching topology for asymmetric multilevel inverter utilizing less number of power electronics components. When the number of the output level increases, it requires more switching states and eventually the number of switching components. The increased number of switches results in higher switching losses which may lead to power loss, and reduction of efficiency of the overall conversion system. The salient feature of this proposed topology is that the module can be used as a sub multiple level structure and can be extended for any number of level with minimal increase in the switching components.展开更多
工频同步相量是支撑电力系统分析、保护和稳定控制的基本信息,不同场景对其估计精度与速度要求日益严格。短路故障初期,工频分量、衰减直流分量(decaying DC component,DDC)以及谐波之间频域混叠,导致工频相量准确估计面临严峻挑战。针...工频同步相量是支撑电力系统分析、保护和稳定控制的基本信息,不同场景对其估计精度与速度要求日益严格。短路故障初期,工频分量、衰减直流分量(decaying DC component,DDC)以及谐波之间频域混叠,导致工频相量准确估计面临严峻挑战。针对多种干扰影响相量测量精度问题,提出一种基于改进离散傅里叶变换的强鲁棒性相量估计算法。首先,对DDC误差原理进行分析,利用多个1/4波离散傅里叶变换(discrete Fourier transform,DFT)计算频域误差,同时引入放大乘子以提升算法鲁棒性;然后,在改进DFT基础上提出算法计算量精简方法,将算法计算效率提升近一倍;最后,构建二次谐波陷波滤波器配合所提算法,弥补了二次谐波难以滤除的缺陷。算例测试表明,所提算法不受DDC参数与采样频率限制,并在多种干扰下表现出良好的抗干扰能力,同时有效缩短了相量估计的暂态时间。展开更多
The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insi...The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insight into the energy band structure and the electron dynamics.Here,we report the harmonics up to the 10th order generated from monolayer MoS2in experiment.The perpendicular components of even harmonics display unreported enhanced yield at a finite ellipticity,which is sensitive to the crystal orientations.The abnormal ellipticity dependence indicates a novel mechanism that the Berry curvature distributed in a two-dimensional structure manipulates the subcycle electron dynamics during harmonics generation.So far,the research of the BC is limited to the theoretical configuration or one-dimensional experimental measurement,lacking a comprehensive characterization of the BC in the whole Brillouin zone.Our experiment provides a potential experimental scheme to characterize the complex BC structure in two-or three-dimensional materials and a new way to control the subcycle electron dynamics based on the Berry curvature field.展开更多
文摘The existing liability division methods for harmonic pollution are either inexplicit or incomplete in physical meaning. To compensate these defects, two new methods are proposed based on line-transferred power components in this paper. At first, all harmonic sources are represented by ideal equivalent current source, line current components and bus voltage components of a source are determined by stimulation of this source with all other sources disabled. Then, the line-trans- ferred power component owing to a source under all sources action together is determined by the theory of line-transferred power components, and called source’s line-transferred power component. At last, the liability of a source for line-end harmonic pollution is divided by two methods: the ration of the source’s line-transferred active power component to the total line-transferred power, and the ration of projection of the source’s line-transferred complex power component to absolute value of the total line-transferred complex power. These two methods are taken into account not only harmonic voltage but also harmonic current in the liability division. Simulation results show that the proposed liability division method based on active power component is the most effective and ideal one.
文摘This multilevel inverter methodology is the center of focus among researchers in recent era.It has been focused due to its advantages over existing topologies,drawbacks and improvement of power quality,Multi-level inverter has the ability to generate nearly sinusoidal waves.This sinusoidal wave can be further improved by increasing the level of output voltage or with the help of filter design,and this manuscript presents single-phase Multi cell Multi-Level Inverter(MLI).It has been considered for reducing component count to get a higher number of output voltage levels and lower Total harmonics distortion profile.It comprises with four symmetric DC input voltage and 10 IGBT switches to produces stepped output of 9 level,and when deploy asymmetric Dc voltage source the same circuit will produce 31 level output with some changes in firing scheme,moreover this circuit is the family of cascaded hybrid bridge inverter so this circuit covered advantage of CHB MLI,This circuit uses lower no.of switch as compared to existing conventional MLIs such as FC-MLI,CHB-MLI,NPC-MLI,This paper also provides one of most pertinent controls and modulation mechanisms for a MLI using a hybrid reference/carrier-oriented sinusoidal PWM mechanism.At last,simulated outcomes are to validate the performance of both architectures in MLI structure as well as verify the concept.
文摘In recent years, the increasing application of nonlinear and unbalanced electronic equipment and large single phase loads have made voltage imbalance a serious problem in power distribution systems. A novel approach has been proposed to eliminate voltage imbalance and disturbances. The main strategy of this scheme is based on series active filter. By improving control circuit toward existing schemes and proposing a new strategy to control the voltage amplitude, simultaneous elimination of voltage imbalance, faults, voltage harmonics and also compensation of voltage drop in transmission lines become possible. Eventually, the voltage on the load side is a perfectly balanced three phase voltage with specific proper amplitude. The proposed scheme has been simulated in a test network and the results show high capability of this scheme for the complete elimination of imbalance without phase shift.
文摘Multilevel inverters have gained much attention for its operation involving applications ranging values of high power rating. This paper proposes a switching topology for asymmetric multilevel inverter utilizing less number of power electronics components. When the number of the output level increases, it requires more switching states and eventually the number of switching components. The increased number of switches results in higher switching losses which may lead to power loss, and reduction of efficiency of the overall conversion system. The salient feature of this proposed topology is that the module can be used as a sub multiple level structure and can be extended for any number of level with minimal increase in the switching components.
文摘工频同步相量是支撑电力系统分析、保护和稳定控制的基本信息,不同场景对其估计精度与速度要求日益严格。短路故障初期,工频分量、衰减直流分量(decaying DC component,DDC)以及谐波之间频域混叠,导致工频相量准确估计面临严峻挑战。针对多种干扰影响相量测量精度问题,提出一种基于改进离散傅里叶变换的强鲁棒性相量估计算法。首先,对DDC误差原理进行分析,利用多个1/4波离散傅里叶变换(discrete Fourier transform,DFT)计算频域误差,同时引入放大乘子以提升算法鲁棒性;然后,在改进DFT基础上提出算法计算量精简方法,将算法计算效率提升近一倍;最后,构建二次谐波陷波滤波器配合所提算法,弥补了二次谐波难以滤除的缺陷。算例测试表明,所提算法不受DDC参数与采样频率限制,并在多种干扰下表现出良好的抗干扰能力,同时有效缩短了相量估计的暂态时间。
基金Zhangjiang LaboratoryNational Natural Science Foundation of China(91950203,11874374)。
文摘The high-order harmonic generation(HHG)in solids permits the exploration of the ultrafast electron dynamics in strong-field light–matter interaction.In particular,the laser ellipticity dependence of HHG provides insight into the energy band structure and the electron dynamics.Here,we report the harmonics up to the 10th order generated from monolayer MoS2in experiment.The perpendicular components of even harmonics display unreported enhanced yield at a finite ellipticity,which is sensitive to the crystal orientations.The abnormal ellipticity dependence indicates a novel mechanism that the Berry curvature distributed in a two-dimensional structure manipulates the subcycle electron dynamics during harmonics generation.So far,the research of the BC is limited to the theoretical configuration or one-dimensional experimental measurement,lacking a comprehensive characterization of the BC in the whole Brillouin zone.Our experiment provides a potential experimental scheme to characterize the complex BC structure in two-or three-dimensional materials and a new way to control the subcycle electron dynamics based on the Berry curvature field.
