故障子模块的切除运行会使模块化多电平变换器系统输出不平衡。分析了故障运行期间,由于相与相之间模块的不对称投入,相间环流将明显增大,不及时处理易造成输出过流、子模块过压等的情况。针对无冗余模块的子模块故障问题,使用调制波重...故障子模块的切除运行会使模块化多电平变换器系统输出不平衡。分析了故障运行期间,由于相与相之间模块的不对称投入,相间环流将明显增大,不及时处理易造成输出过流、子模块过压等的情况。针对无冗余模块的子模块故障问题,使用调制波重组方式的故障穿越策略后,证明了相桥臂间仍不对称运行。然后,通过理论推导故障期间以及调制波重组后的环流状态,证明奇次谐波明显增加,并设计了基于二阶广义积分器的多谐波提取控制器,通过准比例谐振调节器完成对环流的抑制。最终,通过Matlab仿真以及10 k W样机平台完成控制策略的验证。展开更多
分布式发电(Distributed generation,DG)单元高渗透性会造成各种电能质量问题,从而导致电网承载能力降低。为此,提出一种面向分布式电源的改进灰狼优化与引力搜索(Grey wolf optimization and gravity search,GWO-GS)电网承载力提升方...分布式发电(Distributed generation,DG)单元高渗透性会造成各种电能质量问题,从而导致电网承载能力降低。为此,提出一种面向分布式电源的改进灰狼优化与引力搜索(Grey wolf optimization and gravity search,GWO-GS)电网承载力提升方法。提出一种谐波滤波器,大范围地抑制谐波并降低功率损耗,从而最大限度地提高谐波约束的随机性承载能力。利用控制系数的自适应调节和适应度值对权重的作用,同时采用改进灰狼算法进行优化,避免陷入局部最优。结合DG间歇输出功率、负载变化等不确定因素,构建基于改进GWO-GS的滤波器优化。利用Matlab仿真平台对所提优化算法进行验证,结果表明所提算法的收敛时间最短,性能优于其他算法。展开更多
The goal of this paper is to find an excellent adaptive window function for extracting the weak vibration signal and high frequency vibration signal under strong noise.The relationship between windowing transform andf...The goal of this paper is to find an excellent adaptive window function for extracting the weak vibration signal and high frequency vibration signal under strong noise.The relationship between windowing transform andfiltering is analyzed first in the paper.The advantage of adjustable time-frequency window of wavelet transform is introduced.Secondly the relationship between harmonic wavelet and multiple analytic band-pass filter is analyzed.The coherence of the multiple analytic band-pass filter and harmonic wavelet base function is discussed,and the characteristic that multiple analytic band-pass filter included in the harmonic wavelet transform is founded.Thirdly,by extending the harmonic wavelet transform,the concept of the adaptive harmonic window and its theoretical equation without decomposition are put forward in this paper.Then comparing with the Hanning window,the good performance of restraining side-lobe leakage possessed by adaptive harmonic window is shown,and the adaptive characteristics of window width changing and analytical center moving of the adaptive harmonic window are presented.Finally,the proposed adaptive harmonic window is applied to weak signal extraction and high frequency orbit extraction of high speed rotor under strong noise,and the satisfactory results are achieved.The application results show that the adaptive harmonic window function can be successfully applied to the actual engineering signal processing.展开更多
Due to development of distribution systems and increase in electricity demand,the use of capacitor banks increases.From the other point of view,nonlinear loads generate and inject considerable harmonic currents into p...Due to development of distribution systems and increase in electricity demand,the use of capacitor banks increases.From the other point of view,nonlinear loads generate and inject considerable harmonic currents into power system.Under this condition if capacitor banks are not properly selected and placed in the power system,they could amplify and propagate these harmonics and deteriorate power quality to unacceptable levels.With attention of disadvantages of passive filters,such as occurring resonance,nowadays the usage of this type of harmonic compensator is restricted.On the other side,one of parallel multi-function compensating devices which are recently used in distribution system to mitigate voltage sag and harmonic distortion,performs power factor correction,and improves the overall power quality as active power conditioner(APC).Therefore,the utilization of APC in harmonic distorted system can affect and change the optimal location and size of shunt capacitor bank under harmonic distortion condition.This paper presents an optimization algorithm for improvement of power quality using simultaneous optimal placement and sizing of APC and shunt capacitor banks in radial distribution networks in the presence of voltage and current harmonics.The algorithm is based on particle swarm optimization(PSO).The objective function includes the cost of power losses,energy losses and those of the capacitor banks and APCs.展开更多
文摘故障子模块的切除运行会使模块化多电平变换器系统输出不平衡。分析了故障运行期间,由于相与相之间模块的不对称投入,相间环流将明显增大,不及时处理易造成输出过流、子模块过压等的情况。针对无冗余模块的子模块故障问题,使用调制波重组方式的故障穿越策略后,证明了相桥臂间仍不对称运行。然后,通过理论推导故障期间以及调制波重组后的环流状态,证明奇次谐波明显增加,并设计了基于二阶广义积分器的多谐波提取控制器,通过准比例谐振调节器完成对环流的抑制。最终,通过Matlab仿真以及10 k W样机平台完成控制策略的验证。
文摘分布式发电(Distributed generation,DG)单元高渗透性会造成各种电能质量问题,从而导致电网承载能力降低。为此,提出一种面向分布式电源的改进灰狼优化与引力搜索(Grey wolf optimization and gravity search,GWO-GS)电网承载力提升方法。提出一种谐波滤波器,大范围地抑制谐波并降低功率损耗,从而最大限度地提高谐波约束的随机性承载能力。利用控制系数的自适应调节和适应度值对权重的作用,同时采用改进灰狼算法进行优化,避免陷入局部最优。结合DG间歇输出功率、负载变化等不确定因素,构建基于改进GWO-GS的滤波器优化。利用Matlab仿真平台对所提优化算法进行验证,结果表明所提算法的收敛时间最短,性能优于其他算法。
基金Project(51675262)supported by the National Natural Science Foundation of ChinaProject(6140210020102)supported by the Advance Research Field Fund Project of ChinaProject(2016YFD0700800)supported by the National Key Research and Development Plan of China
文摘The goal of this paper is to find an excellent adaptive window function for extracting the weak vibration signal and high frequency vibration signal under strong noise.The relationship between windowing transform andfiltering is analyzed first in the paper.The advantage of adjustable time-frequency window of wavelet transform is introduced.Secondly the relationship between harmonic wavelet and multiple analytic band-pass filter is analyzed.The coherence of the multiple analytic band-pass filter and harmonic wavelet base function is discussed,and the characteristic that multiple analytic band-pass filter included in the harmonic wavelet transform is founded.Thirdly,by extending the harmonic wavelet transform,the concept of the adaptive harmonic window and its theoretical equation without decomposition are put forward in this paper.Then comparing with the Hanning window,the good performance of restraining side-lobe leakage possessed by adaptive harmonic window is shown,and the adaptive characteristics of window width changing and analytical center moving of the adaptive harmonic window are presented.Finally,the proposed adaptive harmonic window is applied to weak signal extraction and high frequency orbit extraction of high speed rotor under strong noise,and the satisfactory results are achieved.The application results show that the adaptive harmonic window function can be successfully applied to the actual engineering signal processing.
文摘Due to development of distribution systems and increase in electricity demand,the use of capacitor banks increases.From the other point of view,nonlinear loads generate and inject considerable harmonic currents into power system.Under this condition if capacitor banks are not properly selected and placed in the power system,they could amplify and propagate these harmonics and deteriorate power quality to unacceptable levels.With attention of disadvantages of passive filters,such as occurring resonance,nowadays the usage of this type of harmonic compensator is restricted.On the other side,one of parallel multi-function compensating devices which are recently used in distribution system to mitigate voltage sag and harmonic distortion,performs power factor correction,and improves the overall power quality as active power conditioner(APC).Therefore,the utilization of APC in harmonic distorted system can affect and change the optimal location and size of shunt capacitor bank under harmonic distortion condition.This paper presents an optimization algorithm for improvement of power quality using simultaneous optimal placement and sizing of APC and shunt capacitor banks in radial distribution networks in the presence of voltage and current harmonics.The algorithm is based on particle swarm optimization(PSO).The objective function includes the cost of power losses,energy losses and those of the capacitor banks and APCs.
