Comparison of performance between bipolar and unipolar double-frequency sinusoidal pulse width modulation in a digitally controlled H-bridge inverter system

By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinu- soidal pulse width modulation （BSPWM） and unipolar double-frequency sinusoidal pulse width modulation （UDFSPWM） respectively, the performances of the two modulation strategies are analyzed in detail. The circuit parameters, used in this paper, are fixed. When the systems, modulated by BSPWM and UDFSPWM, have the same switching frequency, the stabil- ity boundaries of the two systems are the same. However, when the equivalent switching frequencies of the two systems are the same, the BSPWM modulated system is more stable than the UDFSPWM modulated system. In addition, a convenient method of establishing the discrete-time model of piecewise smooth system is presented. Finally, the analytical results are confirmed by circuit simulations and experimental measurements.

Radio-frequency compressed electron pulse-width characterization by cross-correlation between electron bunches and laser-induced plasma

A method is proposed to determine the temporal width of high-brightness radio-frequency compressed electron pulses based on cross-correlation technique involving electron bunches and laser-induced plasma. The temporal evolution of 2-dimensional transverse profile of ultrafast electron bunches repelled by the formed transient electric field of laser-induced plasma on a silver needle is investigated, and the pulse-width can be obtained by analyzing these time-dependent images.This approach can characterize radio-frequency compressed ultrafast electron bunches with picosecond or sub-picosecond timescale and up to 105 electron numbers.

Pulse-Width Pulse-Frequency Based Optimal Controller Design for Kinetic Kill Vehicle Attitude Tracking Control

The attitude control problem of the kinetic kill vehicle is studied in this work. A new mathematical model of the kinetic kill vehicle is proposed, the linear quadratic regulator technique is used to design the optimal attitude controller, and the pulse-width pulse-frequency modulator is used to shape the continuous control command to pulse or on-off signals to meet the requirements of the reaction thrusters. The methods to select the appropriate parameters of pulse-width pulse-frequency are presented in detail. Numerical simulations show that the performance of the LQR/PWPF approach can achieve good control performance such as pseudo-linear operation, high accuracy, and fast enough tracking speed.

On the Describing Functions of PWM Pneumatic High-Speed On-Off Valves

High-speed on-off valves are widey used in PWM electropneumatic servo sys- tems and their characteristics are generally described by their on and off delay time. This paper focuses on establishing the relationships between their on-off switching behaviors and their frequency response characteristics. A method is proposed by which the frequency response characteristics of an analog PWM high-speed on-off valve can be calculated for inputs whose periods are certain multiples of the carrier period, based on its switching be- haviors. Thus, a simple and direct describing function for a PWM high-speed on-off valve is established.

Effect of Pulse Width and Frequency of Bias DC Voltage on the Microstructure of Pure Cr Coatings by Magnetron Sputter Ion Plating

Pure Cr coatings were deposited onto the pieces of silicon wafer at different pulse width and frequency of bias voltage by magnetron sputter ion plating.The microstructure and preferential orientation of pure Cr coatings were analyzed by SEM and XRD respectively.Results show that the diffusion ability of atoms on the coating surface was improved due to the substrate temperature rise effect caused by the ion bombardment with the pulse width increased.However,the effect of frequency of bias DC voltage on the microstructure of pure Cr coatings was particularly significant.The bombardment ions action on the coating surface were more uniformly and more dispersed compared with the nucleation rate of Cr atoms and the density of pure Cr coatings both improved with the frequency increased are the main reasons that the microstructure of pure Cr coatings changed from dense,granular columnar grain outcrops to uniformity,small nano-crystalline particles.

The Usage of the Digital Controller in Regulating Boost Converter

This paper proposes the modeling and simulation technique to analyze and design a Boost converter using generalized minimum variance method with discrete-time quasi-sliding mode to adjust the converter switch through a pulse width modulation (PWM), so as to enhance a stable output voltage. The control objective is to maintain the sensed output voltage stable, constant and equal to some constant reference voltage (8 volt) in the load resistance variation (24, 48, 240) Ω and input voltage variation (20, 24, 28) volt circumstances. This control strategy is very appropriate for the digitally controlled power converter and for the system requirement accomplishment, resulting high output voltage accuracy. The performance degradation in practical implementation can be expected due to noise, PWM nonlinearities, and components imperfection. The digital simulation using MATHLAB/Simulink is performed to validate the functionality of the system.

基于单片机的直流电机变频调速方法与仿真

针对电机谐波损耗及逆变器输出谐波信号影响直流电机变频调速的稳定性,导致调速性能不佳等,提出一种基于单片机的直流电机变频调速方法。建立直流电机变频调速状态空间模型,通过上述模型获取变频调速系统的运行状态;采用电流、速度双闭环PI控制器实现直流电机的变频调速初步控制,使直流电机变频调速系统可同时满足静态性能与动态性能;将直流侧电压输入至SVPWM脉宽调制系统,进一步降低电机谐波损耗和脉动转矩,实现变频调速的精确控制。仿真结果表明,所提方法的直流电机变频调速稳定性更佳、精度更高,整体效果更佳。

高频链矩阵变换器直接功率反步控制策略

针对高频链矩阵变换器(HFLMC)电路前后级耦合导致系统动态性能和鲁棒性降低的问题,提出一种基于直接功率的非线性反步控制策略(BS-DPC)。首先,建立HFLMC非线性数学模型和有功、无功功率动态模型,分析双极性电流空间矢量调制策略;然后,在考虑系统不确定性情况下引入2个解耦控制分量,设计直流输出电流和无功功率反步控制器,实现电池不同工况下输出电流参考值的快速跟踪控制;最后,根据李雅普诺夫稳定性理论证明HFLMC闭环系统全局渐进稳定性,并对比传统PI直接功率控制和BS-DPC策略。仿真和实验结果表明,所提BS-DPC策略控制HFLMC提高了输出电流的动态性能和电网波动及直流滤波电感变化下的鲁棒性,响应时间减少了约78%,网侧THD降低了0.98%。

太瓦飞秒脉冲激光峰值功率测量装置及测量不确定度分析

超短超强脉冲激光(飞秒强激光)具有极高的峰值功率,在激光惯性约束聚变、高能物理、激光微加工等领域具有广阔的应用前景。飞秒脉冲激光峰值功率是评价超短超强脉冲激光系统性能的重要参数。介绍了基于光谱相位相干直接电场重构法的太瓦量级飞秒脉冲激光峰值功率测量方法、测量装置组成和工作原理,搭建了一套太瓦量级的飞秒脉冲激光峰值功率测量装置,分析和讨论了影响太瓦激光峰值功率测量结果的测量不确定度分量来源和主要因素。测量峰值功率的重复性为2.9%,测量不确定度达到17.6%(k=2),有效解决了太瓦量级飞秒激光峰值功率测量问题。

适用于三电平逆变器的电流谐波最小脉宽调制策略

受限于散热条件,大功率牵引传动系统中逆变器开关频率通常很低,三电平逆变器由于在低开关频率下具有较小的输出谐波、较低的dv/dt等特点在中高压大功率领域中被广泛应用。以三电平中点钳位型逆变器为研究对象,提出一种电流谐波最小脉宽调制策略(CHMPWM),基于加权总谐波畸变最小的优化目标求解不同开关角个数下的开关角曲线,与目前应用较为广泛的特定次谐波消除脉宽调制进行谐波性能对比。该方法不会完全消除特定次数的谐波成分,但是总体电流谐波可以达到最小。针对电流谐波最小脉宽调制策略在实现过程中存在的困难,设计全速度范围基于电流谐波最小脉宽调制的多模式调制策略。仿真和实验结果表明,提出的调制策略具有良好的谐波性能,与理论分析结果一致。

室内可见光OFDM通信系统调光控制技术

针对室内可见光通信高速率传输和照明控制的问题,分析了采用脉冲宽度调制调光控制技术的可见光正交频分复用技术系统的调光性能与误码性能.提出了基于功耗小、性能好的单极性正交频分复用系统的调光控制方案,对单极性正交频分复用系统的驱动电流和误码率特性进行了仿真,仿真结果表明,单极性正交频分复用系统可在不牺牲照明质量的同时改善系统性能.此外,针对室内低照明、低功耗的应用需求,提出了一种功率更加有效的补零非对称削波正交频分复用系统,仿真分析表明,补零非对称削波正交频分复用系统可在不损失误码性能的情况下提高系统的功率效率.

样品尺寸对脉冲穿透法声速测量误差的影响

岩心的声速测量能够提供关键的储层地质信息,对储层评价和地质模型构建具有实际应用价值。脉冲穿透法是一种常用的声速测量方法,但它要求样品尺寸远大于波长(约10倍)。当特殊场景如需在测井信号主频8~20 kHz下测量样品声速时,被测样品长达数米,不仅制备困难,还存在声波信号衰减大的问题。关于试样尺寸能否缩小或能缩小到什么程度的定量研究很少见到公开报道。该文将数值模拟和实验测量相结合,系统定量地研究了圆柱状样品长度及直径与波长之间的比值对脉冲穿透法声速测量精度的影响。研究表明:为确保脉冲穿透法声速测量的准确性,建议样品沿传播方向上的长度不低于4倍声波波长,横向尺寸不低于2倍波长。研究结果突破了传统脉冲穿透法要求样品尺寸远大于波长的限制,为优化声速测量方法和提高测量精度提供了理论支持。

LLC谐振变换器数字控制技术研究

LLC谐振变换器能够实现全负载范围的初级零电压开关(ZVS)和次级零电流开关(ZCS),因此得到关注。全桥LLC谐振电路可以通过改变初级开关管驱动脉冲频率调制(PFM)方法,调节LLC谐振腔的增益进行闭环控制,保证输出电压在输入电压变化大、不同负载条件下的输出稳定。LLC谐振增益曲线会随负载减轻而调节特性变差,单一PFM调节无法应对。研究集PFM、脉宽调制(PWM)和间歇工作模式(Burst模式)的混合控制方案,解决变换器从空载到满载不同工作条件下的控制方式,并在发生短路故障时变换器迅速保护。此处采用HPM6300系列芯片完成LLC数字控制和保护功能,设计系统的实验装置并编写应用软件。经过整机测试,实验结果表明所采用方案的有效性,并达到设计目标。

IMPROVEMENT IN WAVEFORM OF SWITCHING POINT-PRESET SPWM INVERTERS

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.

超高温随钻测量系统中的电源技术

超高温随钻测量仪器要求井下供电电源具备可靠性高、抗高温、体积小等特点,目前国内尚无成熟产品。介绍了一种井下稳压电源模块的设计方案,该电源基于非隔离型直流变换器交错并联BUCK拓扑,以CISSOID公司的CHT-MAGMA高温脉宽调制器作为主控芯片,采用推挽驱动器对脉宽调制(Pulse-Width Modulation,PWM)逻辑电平进行功率放大,再经脉冲变压器实现了功率管隔离驱动,确保两路交错驱动脉冲能够驱动MOS(Metal-Oxide Semiconductor)管可靠导通与截止,实现高效电源变换。结果表明,该电源模块的转换效率在全温度范围内达86%以上,能够较好地满足随钻仪器在井下超高温环境下的供电要求。

基于滞环控制的航空发动机快速电磁阀控制仪设计

使用滞环控制方法实现快速电磁阀两端电压的脉宽调制,精确控制流过快速电磁阀的强激电流和维持电流的幅值,使用变频变占空比的方法控制流过快速电磁阀电流脉冲的占空比,具备输入过压、输入欠压和输出短路保护功能,设计了一款基于滞环控制的快速电磁阀控制仪。该快速电磁阀控制仪已经在航空发动机快速电磁阀及其主燃油控制附件的维修过程批量使用,杜绝了因控制器输入信号不稳定导致的航空发动机主燃油系统故障,且抗干扰能力强,能够预防维修过程人为差错,起到了提高航空快速电磁阀维修质量的作用。

高重频窄脉宽多波长激光器可靠性分析

本文对高重频窄脉宽多波长激光器的可靠性进行了分析及验证,建立了高重频窄脉宽多波长激光器的框图法模型。在初始设计阶段开展激光器的可靠性分析,定量计算了激光器各单元的可靠性结果,包括失效率λ和平均无故障工作时间(Mean Time Between Failure,MTBF),预计激光器整机的无故障工作时间为1798.8 h。为满足激光器的设计指标要求,通过选用高品质晶体、半导体激光器的Ⅰ级降额设计和电源控制的冗余设计,实现激光器的可靠性优化。经优化设计后,激光器整机的无故障工作时间达2260.9 h。搭建激光器整机对可靠性优化设计结果进行验证,验证结果表明:激光器无故障工作时间可达2400 h。

适用于构网型新能源发电系统的MCSPWM多电平逆变器

构网型新能源发电系统具备系统惯量支持和电压支撑的优势,可利用各种能源之间的互补性,提高能源利用率及系统稳定性。在该系统中,多电平逆变器发挥着重要作用。为此,提出一种新型的开关电容九电平逆变器及基于高频的多重载波正弦脉宽调制(multi-carrier sinusoidal pulse width modulation,MCSPWM)策略,该逆变器在开关数量、管压应力、升压能力和控制难度等方面具有优良的综合性能。该文分析了该逆变器的工作原理和抑制电容充电电流尖峰的方法,在软硬件设计的基础上,成功研制了新型开关电容九电平逆变器实验样机。样机实验结果证明,所提出的拓扑在高频调制策略下具有输出2倍升压、双向功率流的能力,开关电容可自动均压,开关管电压应力不超过输入直流源电压Uin,并且开关电容纹波电压的峰峰值小于2V。新型开关电容九电平逆变器,在构网型新能源发电系统中具有潜在的应用前景。

基于SVPWM的三电平家用变频器的研究

家用变频器的变频调速是保障家用电器备正常运行的关键,其性能直接影响到电器在使用时的安全性和效率。为了提高家用变频器的调速性能,增强家用电器设备的稳定性,在PWM控制的两电平常用变频技术的基础上,提出SVPWM调制,并采用三电平的拓扑结构,然后使用matlab-simulink搭建仿真模型,结果表明:基于SVPWM的三电平家用变频器的输出电压、电流波形非常接近正弦波,可以更加平稳地控制电机,提高家用电器的效率和性能,同时节省能源和降低设备噪音。

基于SVPWM的生产流水线调速系统研究

现代化工厂的生产流水线大多依靠异步电机进行电力传动,而电机调速的准确程度、响应时间等参数对产品质量与工作效率有着重要影响。针对大型流水线需求,采用空间矢量脉宽调制技术(Space Vector Pulse Width Modulation,SVPWM),研究流水线调速系统的控制电路。在Simulink环境下构建变频调速系统的仿真模型并合理设置参数,通过仿真验证系统性能,结果表明:采用SVPWM的流水线调速系统,利用电流内环、转速外环的PI控制方式,可实现在0~1600 r/min范围内的转速可调,响应时间小于30 ms的大型流水线变频调速系统。系统具有调速准确度高、响应时间短等优点,满足现代化工业流水线的需求。