DC DC convertors can convert the EV's high voltage DC power supply into the low voltage DC power supply. In order to design an excellent convertor one must be guided by theory of automatic control. The principl...DC DC convertors can convert the EV's high voltage DC power supply into the low voltage DC power supply. In order to design an excellent convertor one must be guided by theory of automatic control. The principle and the method of design, modeling and control for DC DC convertors of EV are introduced. The method of the system response to a unit step function input and the frequency response method are applied to researching the convertor's mathematics model and control characteristic. Experiments show that the designed DC DC convertor's output voltage precision is high, the antijamming ability is strong and the adjustable performance is fast and smooth.展开更多
The analog-to-information convertor (AIC) is a successful practice of compressive sensing (CS) theory in the analog signal acquisition. This paper presents a multi-narrowband signals sampling and reconstruction model ...The analog-to-information convertor (AIC) is a successful practice of compressive sensing (CS) theory in the analog signal acquisition. This paper presents a multi-narrowband signals sampling and reconstruction model based on AIC and block sparsity. To overcome the practical problems, the block sparsity is divided into uniform block and non-uniform block situations, and the block restricted isometry property and sub-sampling limit in different situations are analyzed respectively in detail. Theoretical analysis proves that using the block sparsity in AIC can reduce the restricted isometric constant, increase the reconstruction probability and reduce the sub -sampling rate. Simulation results show that the proposed model can complete sub -sampling and reconstruction for multi-narrowband signals. This paper extends the application range of AIC from the finite information rate signal to the multi-narrowband signals by using the potential relevance of support sets. The proposed receiving model has low complexity and is easy to implement, which can promote the application of CS theory in the radar receiver to reduce the burden of analog-to digital convertor (ADC) and solve bandwidth limitations of ADC.展开更多
An all-fiber LP_(01)-LP_(11) mode convertor based on side-polished small-core single-mode fibers(SMFs) is numerically demonstrated. The linearly polarized incident beam in one arm experiences π shift through a fiber ...An all-fiber LP_(01)-LP_(11) mode convertor based on side-polished small-core single-mode fibers(SMFs) is numerically demonstrated. The linearly polarized incident beam in one arm experiences π shift through a fiber half waveplate, and the side-polished parts merge into an equivalent twin-core fiber(TCF) which spatially shapes the incident LP_(01) modes to the LP_(11) mode supported by the step-index few-mode fiber(FMF). Optimum conditions for the highest conversion efficiency are investigated using the beam propagation method(BPM) with an approximate efficiency as high as 96.7%. The proposed scheme can operate within a wide wavelength range from 1.3 μm to1.7 μm with overall conversion efficiency greater than 95%. The effective mode area and coupling loss are also characterized in detail by finite element method(FEM).展开更多
基于模块化多电平换流器的柔性直流输电(modular multilevel convertor based high voltage direct current,MMC-HVDC)系统存在的中高频振荡问题严重危胁电力系统的正常运行。首先,基于MMC的动态相量模型,建立了MMC的交流侧阻抗模型;其...基于模块化多电平换流器的柔性直流输电(modular multilevel convertor based high voltage direct current,MMC-HVDC)系统存在的中高频振荡问题严重危胁电力系统的正常运行。首先,基于MMC的动态相量模型,建立了MMC的交流侧阻抗模型;其次,利用阻抗法分析控制环节及控制参数对MMC阻抗特性的影响,得到了功率外环、电流内环及控制链路延时是导致MMC呈现负阻尼特性的主要原因;再次,在分析现有基于电压前馈环节和电流内环的协同振荡抑制策略不足的基础上,提出了功率外环附加直流电流反馈的振荡抑制策略,极大程度消除系统中的谐波分量,改善了MMC的阻抗特性;最后,通过电磁仿真软件验证理论分析和抑制措施的正确性与有效性。展开更多
文摘DC DC convertors can convert the EV's high voltage DC power supply into the low voltage DC power supply. In order to design an excellent convertor one must be guided by theory of automatic control. The principle and the method of design, modeling and control for DC DC convertors of EV are introduced. The method of the system response to a unit step function input and the frequency response method are applied to researching the convertor's mathematics model and control characteristic. Experiments show that the designed DC DC convertor's output voltage precision is high, the antijamming ability is strong and the adjustable performance is fast and smooth.
基金supported by the National Natural Science Foundation of China(61172159)
文摘The analog-to-information convertor (AIC) is a successful practice of compressive sensing (CS) theory in the analog signal acquisition. This paper presents a multi-narrowband signals sampling and reconstruction model based on AIC and block sparsity. To overcome the practical problems, the block sparsity is divided into uniform block and non-uniform block situations, and the block restricted isometry property and sub-sampling limit in different situations are analyzed respectively in detail. Theoretical analysis proves that using the block sparsity in AIC can reduce the restricted isometric constant, increase the reconstruction probability and reduce the sub -sampling rate. Simulation results show that the proposed model can complete sub -sampling and reconstruction for multi-narrowband signals. This paper extends the application range of AIC from the finite information rate signal to the multi-narrowband signals by using the potential relevance of support sets. The proposed receiving model has low complexity and is easy to implement, which can promote the application of CS theory in the radar receiver to reduce the burden of analog-to digital convertor (ADC) and solve bandwidth limitations of ADC.
基金supported by the Fundamental Research Funds for the Central Universities(No.2016JBM002)
文摘An all-fiber LP_(01)-LP_(11) mode convertor based on side-polished small-core single-mode fibers(SMFs) is numerically demonstrated. The linearly polarized incident beam in one arm experiences π shift through a fiber half waveplate, and the side-polished parts merge into an equivalent twin-core fiber(TCF) which spatially shapes the incident LP_(01) modes to the LP_(11) mode supported by the step-index few-mode fiber(FMF). Optimum conditions for the highest conversion efficiency are investigated using the beam propagation method(BPM) with an approximate efficiency as high as 96.7%. The proposed scheme can operate within a wide wavelength range from 1.3 μm to1.7 μm with overall conversion efficiency greater than 95%. The effective mode area and coupling loss are also characterized in detail by finite element method(FEM).
文摘基于模块化多电平换流器的柔性直流输电(modular multilevel convertor based high voltage direct current,MMC-HVDC)系统存在的中高频振荡问题严重危胁电力系统的正常运行。首先,基于MMC的动态相量模型,建立了MMC的交流侧阻抗模型;其次,利用阻抗法分析控制环节及控制参数对MMC阻抗特性的影响,得到了功率外环、电流内环及控制链路延时是导致MMC呈现负阻尼特性的主要原因;再次,在分析现有基于电压前馈环节和电流内环的协同振荡抑制策略不足的基础上,提出了功率外环附加直流电流反馈的振荡抑制策略,极大程度消除系统中的谐波分量,改善了MMC的阻抗特性;最后,通过电磁仿真软件验证理论分析和抑制措施的正确性与有效性。
