Coordinated Capacitor Voltage Balancing Method for Cascaded H-bridge Inverter with Supercapacitor and DC-DC Stage

Cascaded H-bridge inverter(CHBI) with supercapacitors(SCs) and dc-dc stage shows significant promise for medium to high voltage energy storage applications. This paper investigates the voltage balance of capacitors within the CHBI, including both the dc-link capacitors and SCs. Balance control over the dc-link capacitor voltages is realized by the dcdc stage in each submodule(SM), while a hybrid modulation strategy(HMS) is implemented in the H-bridge to balance the SC voltages among the SMs. Meanwhile, the dc-link voltage fluctuations are analyzed under the HMS. A virtual voltage variable is introduced to coordinate the balancing of dc-link capacitor voltages and SC voltages. Compared to the balancing method that solely considers the SC voltages, the presented method reduces the dc-link voltage fluctuations without affecting the voltage balance of SCs. Finally, both simulation and experimental results verify the effectiveness of the presented method.

OFDM with Generalized Cascade Index Modulation for Secure Communications

Cascade index modulation(CIM) is a recently proposed improvement of orthogonal frequency division multiplexing with index modulation(OFDM-IM) and achieves better error performance.In CIM, at least two different IM operations construct a super IM operation or achieve new functionality. First, we propose a OFDM with generalized CIM(OFDM-GCIM) scheme to achieve a joint IM of subcarrier selection and multiple-mode(MM)permutations by using a multilevel digital algorithm.Then, two schemes, called double CIM(D-CIM) and multiple-layer CIM(M-CIM), are proposed for secure communication, which combine new IM operation for disrupting the original order of bits and symbols with conventional OFDM-IM, to protect the legitimate users from eavesdropping in the wireless communications. A subcarrier-wise maximum likelihood(ML) detector and a low complexity log-likelihood ratio(LLR) detector are proposed for the legitimate users. A tight upper bound on the bit error rate(BER) of the proposed OFDM-GCIM, D-CIM and MCIM at the legitimate users are derived in closed form by employing the ML criteria detection. Computer simulations and numerical results show that the proposed OFDM-GCIM achieves superior error performance than OFDM-IM, and the error performance at the eavesdroppers demonstrates the security of D-CIM and M-CIM.

Compact temperature-insensitive modulator based on a silicon microring assistant Mach-Zehnder interferometer

On the silicon-on-insulator platform, an ultra compact temperature-insensitive modulator based on a cascaded microring assistant Mach-Zehnder interferometer is proposed and demonstrated with numerical simulation. According to the calculated results, the tolerated variation of ambient temperature can be as high as 134 ℃ while the footprint of such a silicon modulator is only 340 μm2.

Synchronization analysis on cascaded multilevel converters with distributed control

Cascaded multilevel converters built with integrated modules have many advantages such as increased power density,flexible distributed control,multi-functionality,increased reliability and short design cycles.However,the system performance will be affected due to the synchronization errors among each integrated modules.This paper analyzes the impact of the three kinds of synchronization errors on the whole system performance,as well as detailed synchronization implementation.Some valuable conclusions are derived from the theoretical analysis,simulations and experimental results.

THD Analysis of Cascaded H-Bridge Inverter with Fuzzy Logic Controller

In recent days, the multilevel inverter technology is widely applied to domestic and industrial applications for medium voltage conversion. But, the power quality issues of the multilevel inverter limit the usage of much sensitive equipment like medical instruments. The lower distortion level of the output voltage and current can generate a quality sinusoidal output voltage in inverters and they can be used for many applications. The harmonics can cause major problems in equipments due to the nonlinear loads connected with the power system. So, it is necessary to minimize the losses to raise its overall efficiency. In this paper, a new topology of seven level asymmetrical cascaded H-bridge multilevel inverter with a Fuzzy logic controller had been implemented to reduce the Total Harmonic Distortion (THD) and to improve the overall performance of the inverter. The proposed model is well suited for use with a solar PV application. In this topology, only six IGBT switches are used with three different voltage ratings of PV modules (1:2:4). The lower number of semiconductor switches leads to minimizing overall di/dt ratings and voltage stress on each switches and switching losses. The gate pulses generated by Sinusoidal Pulse Width Modulation (SPWM) technique with a Fuzzy logic controller are also introduced. A buck-boost converter is used to maintain the constant PV voltage level integrated by an MPPT technique followed by Perturb and Observer algorithm is also implemented. The MPPT is used to harness the maximum power of solar radiations under its various climatic conditions. The new topology is evaluated by a Matlab/Simulink model and compared with a hardware model. The results proved that the THD achieved by this topology is 1.66% and realized that it meets the IEEE harmonic standards.

基于改进Cascade RCNN的输电线路防振锤脱落检测方法

无人机巡检输电线路时,因拍摄角度和距离问题,容易出现被输电线遮挡和远距离拍摄的防振锤脱落目标,导致目标特征被遮挡且分辨率较低,且部分防振锤出现滑移现象,导致目标识别准确率降低。针对以上问题,提出一种基于改进Cascade RCNN的防振锤脱落检测网络。第一,设计了对比学习网络,将正负样本与真实样本的特征进行对比学习,利用对比损失函数训练网络,使其能更加关注到被遮挡的防振锤脱落目标,提升其特征提取能力;第二,进行了分类器增强操作,筛选出网络级联结构中回归效果较好的感兴趣区域并送入最后的分类回归队列中,提高了分类器的分类能力,进而提升检测目标的分类分数;第三,设计了并行注意力机制模块,整合网络提取的特征,增大关键特征的权重,使网络关注到图像中更关键的区域;在特征金字塔中,将双线性插值方法代替为反卷积,提升特征还原能力。经交叉验证实验结果表明,改进后的模型召回率、精确率和平均精度达到了97.5%,91.0%和92.0%,相比基线模型分别提高了6.9%,28.4%和8.0%。

Thin-film lithium niobate dual-parallel Mach-Zehnder modulator for a simple photonic system measuring Doppler frequency shift

In recent years,thin-film lithium niobate(TFLN)electro-optic(EO)modulators have developed rapidly and are the core solution for the next generation of microwave photonics(MWP)problems.We designed and fabricated a dual-parallel Mach-Zehnder modulator(DPMZM)based on TFLN,achieving a 3 dB electro-electro(EE)bandwidth of 29 GHz and a low drive voltage(Vπ=6 V).The device we manufactured is metal-encapsulated.It is noteworthy that we proposed a single-channel Doppler frequency shift(DFS)measurement system based on this device and conducted verification experiments.We coupled light from an external laser into the chip and passed it through each of the two sub-MZMs of the DPMZM.These lights were modulated by echo signals and reference signals.By measuring the frequency of the output signal,we can obtain a DFS value without directional ambiguity.The success of this experiment marks a key step in the practical application of TFLN modulators in MWP.

Highly-sensitive NO,NO2,and NH3 measurements with an open-multipass cell based on mid-infrared wavelength modulation spectroscopy

A compact prototype based on mid-infrared wavelength modulation spectroscopy（WMS）is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers（QCLs）with central frequencies around 1900.0 cm^-1,1600.0 cm^-1,and 1103.4 cm^-1are used for NO,NO2,and NH3detections,respectively,by timedivision multiplex.An open-path multi-pass cell of 60-m optical path length is applied to the instrument for high sensitivity and reducing the response time to less than 1 s.The prototype achieves a sub-ppb detection limit for all the three target gases with an average time of about 100 s.The instrument is installed in the Jiangsu environmental monitoring center to conduct performance tests on ambient air.Continuous 24-hour measurements show good agreement with the results of a reference instrument based on the chemiluminescence technique.

FSK Modulation Scheme for High-Speed Optical Transmission

In this paper, we describe the generation, detection, and performance of frequency-shift keying （FSK） for high-speed optical transmission and label switching. A non-return-to-zero （NRZ） FSK signal is generated by using two continuous-wave （CW） lasers, one Mach-Zehnder modulator （MZM）, and one Mach-Zehnder delay interferometer （MZDI）. An RZ-FSK signal is generated by cascading a dual-arm MZM, which is driven by a sinusoidal voltage at half the bit rate. Demodulation can be achieved on 1 bit rate through one MZDI or an array waveguide grating （AWG） demultiplexer with balanced detection. We perform numerical simulation on two types of frequency modulation schemes using MZM or PM, and we determine the effect of frequency tone spacing （FTS） on the generated FSK signal. In the proposed scheme, a novel frequency modulation format has transmission advantages compared with traditional modulation formats such as RZ and differential phase-shift keying （DPSK）, under varying dispersion management. The performance of an RZ-FSK signal in a 4 x 40 Gb/s WDM transmission system is discussed. We experiment on transparent wavelength conversion based on four-wave mixing （FWM） in a semiconductor optical amplifier （SOA） and in a highly nonlinear dispersion shifted fiber （HNDSF） for a 40 Gb/s RZ-FSK signal. The feasibility of all-optical signal processing of a high-speed RZ-FSK signal is confirmed. We also determine the receiver power penalty for the RZ-FSK signal after a 100 km standard single-mode fiber （SMF） transmission link with matching dispersion compensating fiber （DCF）, under the post-compensation management scheme. Because the frequency modulation format is orthogonal to intensity modulation and vector modulation （polarization shift keying）, it can be used in the context of the combined modulation format to decrease the data rate or enhance the symbol rate. It can also be used in orthogonal label-switching as the modulation format for the payload or the label. As an example, we propose a simple orthogonal optical label switching technique based on 40 Gb/s FSK payload and 2.5 Gb/s intensity modulated （IM） label.

Atmospheric N2O gas detection based on an inter-band cascade laser around 3.939 μm

N2O is a significant atmospheric greenhouse gas that contributes to global warming and climate change.In this work,the high sensitivity detection of atmospheric N2O is achieved using wavelength modulation spectroscopy(WMS)with an inter-band cascade laser operating around 3.939μm.A Lab VIEW-based software signal generator and software lock-in amplifiers are designed to simplify the system.In order to eliminate the interference from water vapor,the detection was performed at a pressure of 0.1 atm(1 atm=1.01325×10^5 Pa)and a drying tube was added to the system.To improve the system performance for long term detection,a novel frequency locking method and 2 f/1 f calibration-free method were employed to lock the laser frequency and calibrate the power fluctuations,respectively.The Allan deviation analysis of the results indicates a detection limit of^20 ppb(1 ppb=1.81205μg/m3)for a 1 s integration time,and the optimal detection limit is^5 ppb for a 40-s integration time.

Spectroscopy system based on a single quantum cascade laser for simultaneous detection of CO and CO_2

A quantum cascade laser（QCL） based system for simultaneous detection of CO and CO_2 is developed.The QCL can scan over two neighboring CO（2055.40 cm^（-1）） and CO_2（2055.16 cm^（-1）） lines with a single current scan.The wavelength modulation spectroscopy（ f = 20 k Hz） is utilized to enhance the signal-to-noise ratio.A white cell with an effective optical path length of 74 m is used.The calibration of the sensor is performed and minimum detection limits of 1.3 ppb（1 × 10^（-9））for CO and 0.44 ppm（1 × 10^（-6）） for CO_2 are achieved.

单相级联型多电平变换器直流纹波电压分析及抑制策略

级联H桥型多电平变换器采用移相变压器+整流供电时具有功率因数高、输出电压谐波含量低等优点,在大功率工业领域范围内得到了广泛应用。传统的调制算法都以假设直流母线电压恒定为前提,然而在直流侧会出现低频纹波并被调制和传输到负载,导致输出电压波形畸变。目的为了探讨级联H桥单元供电侧存在大量直流纹波电压导致输出负载电压波形畸变的问题,方法本文首先采用双重傅里叶理论分析直流纹波电压,在此基础上引入一种直流纹波前馈补偿策略,通过测量每个级联H桥的直流侧实际输入电压除以电压基准值并与传统载波信号相乘,进而与调制电压进行载波移相调制;同时采用矢量控制,通过FFT变换虚拟出无功电压,以获得更快的收敛速度、更高的稳定性和更小的振荡。结果仿真和实验结果表明,所提调制算法和控制策略可有效抑制负载电压中的低次谐波,减小输出电压波形畸变,实现逆变电源的快速动态响应和无稳态误差控制。结论实验结果验证了本文所采用的调制策略和控制策略的可行性与合理性。

Capacitor Pattern H-Bridge Multilevel Inverter (CPHMLI) Using Phase Diposition Pulse Width Modulation for Grid Applications

This work presents an implementation of an innovative single phase multilevel inverter using capacitors with reduced switches. The proposed Capacitor pattern H-bridge Multilevel Inverter (CPHMLI) topology consists of a proper number of Capacitor connected with switches and power sources. The advanced switching control supplied by Pulse Width Modulation (PDPWM) to attain mixed staircase switching state. The charging and discharging mode are achieved by calculating the voltage error at the load. Furthermore, to accomplish the higher voltage levels at the output with less number of semiconductors switches and simple commutation designed using CPHMLI topology. To prove the performance and effectiveness of the proposed approach, a set of experiments performed under various load conditions using MATLAB tool.

一种两倍升压五电平开关电容逆变器

开关电容型逆变器具有使用单直流电源输入、电容电压自均衡、输出谐波含量低以及高电压增益的优势。本文提出一种新型五电平逆变器拓扑,该拓扑由1个直流电源、2个浮动电容、1个电感以及4对互补开关管构成;采用多载波层叠调制策略实现开关电容与输入电源的分时串并联运行;实现了2倍电压增益、五电平输出以及电容电压自均衡;通过增加电感抑制了开关电容充电时存在的脉冲电流,降低了开关管的电流应力。此外,逆变电路中没有单独二极管器件,使得该电路具有能量双向流动的能力,扩展了电路的应用范围。本文详细分析了电路的构成及工作过程,仿真及实验结果验证了所提出的逆变器具有可行性。

面向超分辨率重建的层次间局部特征增强网络

基于卷积神经网络的超分辨率重建模型以单项传播为主,层次越靠后感知信息的能力越微弱,导致层次间局部特征部分丢失,难以实质提升网络的特征表达能力。针对此问题,提出层次间局部特征增强网络。该方法由级联残差模块、层次间特征增强块和特征感知注意力机制组成。级联残差模块通过有效残差连接增加对残差分支信息的利用;层次间特征增强块提取不同深度特征的依赖关系,自适应调整中间层特征权值增强捕获关键信息的能力;特征感知注意力机制采用方向感知和位置判断的方式准确定位和识别感兴趣对象。多项标准数据集的实验结果表明,该方法能改善超分辨率的视觉重建效果,整体性能优于现有方法。

单相级联整流器开路故障诊断和容错均压空间矢量脉宽调制算法

针对单相级联H桥整流器(CHBR)的功率开关器件存在的开路故障问题,研究一种开关管开路故障的快速诊断算法,以及针对开关管开路故障的容错均压空间矢量脉宽调制(SVPWM)算法。首先,该文分析单相CHBR功率开关管开路故障时电流流通路径的变化,建立电流误差变化率的分析模型,并提出一种基于电流误差变化率的快速诊断算法。该算法可以快速且准确地定位到故障开关管,且易于在程序中实现。其次,该文提出一种故障容错均压SVPWM算法,该算法在开关管开路故障时利用冗余矢量和冗余开关状态可以使系统在发生故障时仍然可以正常运行,并且各模块间的直流电压也能保持均衡。最后,通过仿真和实验验证了该文所提算法的可行性。

一种非对称级联H桥三相逆变器的功率均衡混合随机脉宽调制方法

为了降低电压比为1∶1∶1∶3的非对称级联H桥三相逆变器输出线电压的脉宽调制(PWM)噪声峰值,该文提出一种融合阶梯波调制、同相载波层叠调制、随机调制及功率均衡的功率均衡混合随机脉宽调制(PB-HRPWM)方法。该方法可概述为:(1)通过高压H桥单元的调制波与参考电位相比较,产生高压H桥单元的驱动脉冲和低压H桥单元的调制波;(2)通过同相层叠随机载波与低压H桥单元的调制波相比较,产生随机脉冲;(3)通过脉冲逻辑运算方法对随机脉冲按照0.5T_(ah)进行循环分配,得到低压H桥单元的驱动脉冲;(4)使用高低压H桥单元的驱动脉冲控制三相逆变器的运行。仿真和实验结果表明:该方法可以降低线电压PWM噪声峰值,同时实现低压H桥单元之间的功率均衡。相比传统的随机和非随机PWM方法,所提PB-HRPWM方法具有更低的线电压PWM噪声峰值和更小的线电压总谐波畸变率(THD)。最后,通过仿真对比和实验验证了所提PB-HRPWM方法的有效性和可行性。

痕量N_(2)O气体检测中数字锁相放大器的设计

针对笑气(N_(2)O)等气态物质的滥用,基于量子级联激光器与波长调制技术相结合的检测方法,可以对吸食人员呼出笑气浓度进行检测,实现吸食人员的现场快速鉴定。针对检测过程中激光器光强抖动带来的测量误差,提出一种适用于痕量N_(2)O气体检测中数字锁相放大器的设计。该锁相放大器中集成了激光器光强调制模块,当碲镉汞探测器接收到吸收后的光强信号后,同时在FPGA中进行一次和二次谐波的解调,并对二次谐波进行归一化处理,避免光强抖动对测量的影响。使用该锁相放大器对检测系统的性能进行评估,通过质量流量控制器配置不同浓度N_(2)O气体,当激光器调制频率为5kHz,测得归一化二次谐波峰值平均值与N_(2)O气体浓度值之间的线性拟合度为0.992 1。使用Allan方差对检测系统的检出限进行评估,当系统的积分时间为0.1 s时,N_(2)O气体的检出限为17.7×10^(-9);积分时间为6.3 s时,N_(2)O气体的检出限达到最低为8.9×10^(-9)。该锁相放大器具有集成度高、检测速度快、信噪比高等优点,适用于痕量N_(2)O气体的现场快速检测。

应用于收发链路多模块级联的优化设计方法

为解决波束赋形芯片中子电路模块由于寄生效应而导致的级联失配问题提出了一种优化设计方法。该设计方法通过主动引入相邻器件阻抗牵引效应,并使其与级联阻抗失配相抵消从而实现阻抗“预失配”的设计方案。对“预失配”的技术原理以及设计流程进行了简要分析,并通过加工一款采用优化设计方案的4通道X/Ku波段的射频收发芯片,验证了该设计方案的可实现性与有效性。在8 GHz~18 GHz频带范围内,该芯片与基于端口驻波设计体系的原芯片相比,收发链路增益分别为6.5 dB和14 dB,提升了超过2 dB。发射链路输出功率21 dBm,发射效率为15.7%,分别提升了1 dB和9%。接收链路噪声系数为8.72 dB,降低了1.2 dB。收发链路最大移相均方根误差为5.12°和5.25°,分别下降了3.17°和1.75°。

相间短路故障条件下级联H桥光伏逆变器的有功功率回流抑制策略

针对现有零序电压补偿策略无法有效抑制级联H桥光伏并网逆变器在电网不对称故障期间存在有功功率回流的问题,定量分析现有零序电压补偿策略的局限性,提出一种正负序最大最小值谐波零序电压注入控制策略,该策略能有效缩小过调制区域,扩大级联H桥型光伏并网逆变器在相间短路故障条件下的运行范围。实验结果验证了所提出控制策略的有效性和可行性。