Predictive Current Control for Voltage Source Inverters Considering Dead-Time Effect

This paper proposes a new concept of synthesized voltage vector to address dead-time effect issue for Finite Control Set Model Predictive Control(FCS-MPC)technique.For a voltage source inverter(VSI),dead-time is inevitably inserted between the turn off and turn on instants of power devices to avoid short circuit phenomenon.The influence of dead-time leads to output voltage vector error of three-phase inverters.Furthermore,it will result in computing deviation in cost function,and will deteriorate the performance of the system if not properly dealt with.In this paper,the problem is clearly analyzed,and the solution to this issue is proposed by introducing a synthesized voltage vector.The proposed solution is verified by Hardware-in-the-loop(HiL)test in real time,and results validate the effectiveness of the proposed solution.

Effect of temperature on heavy ion-induced single event transient on 16-nm FinFET inverter chains

The variations of single event transient(SET)pulse width of high-LET heavy ion irradiation in 16-nm-thick bulk silicon fin field-effect transistor(Fin FET)inverter chains with different driven strengths are measured at different temperatures.Three-dimensional(3D)technology computer-aided design simulations are carried out to study the SET pulse width and saturation current varying with temperature.Experimental and simulation results indicate that the increase in temperature will enhance the parasitic bipolar effect of bulk Fin FET technology,resulting in the increase of SET pulse width.On the other hand,the increase of inverter driven strength will change the layout topology,which has a complex influence on the SET temperature effects of Fin FET inverter chains.The experimental and simulation results show that the device with the strongest driven strength has the least dependence on temperature.

Modeling and simulation of induction motor drive system to investigate and mitigate of PWM inverter’s adverse effects

Modeling and simulation of induction motor drive system to investigate and mitigate the adverse effects of PWM inverter based on analysis, modeling and simulation are presented. The estimation of conducted disturbances and other adverse effects of PWM inverter by simulation offer a considerable gain from the economic point of view. For an accurate model of the motor drive system including mains, rectifier, inverter, motor and its long cables, the high frequency parasitic current paths are taken into account. The novel model and its parasitic values for three-phase induction motor system are presented. Finally a new solution for suppressing EMI, common mode voltage, leakage current, bearing current and shaft voltages is proposed and the results show the excellent performances of proposed solution including active and passive filters.

Mixed Dead-time Effect Suppression Strategy for Modular Multilevel Converters

Dead time is necessary for the coupled power switches to prevent shoot-through,especially in the modular multilevel converters(MMCs)with a large number of power switches.This paper proposes a dead-time effect suppression strategy for MMCs with nearest level modulation.The operational principles of MMCs are first analyzed.According to the operational features of MMCs,the method that removes a switching signal from the coupled switches and the reduced switching frequency voltage balancing algorithms(RSFVBAs)are mixed in the proposed method.In the intervals that are furthest away from the zerocrossing points(ZCP)of arm currents,the single switching signal method can completely eliminate the dead-time effect(DTE).Alternatively,the DTE is suppressed by the RSFVBA in intervals that are close to the ZCP.By the combination of the two methods,the dependence of the DTE suppression method on currents is reduced and the influences of ZCP are also released without degrading the normal operation performance of MMCs.Moreover,the output performance of MMCs is improved and the voltage stress on the arm inductor dramatically decreases.Finally,the validation of the method is verified by the simulation results with the professional tool Matlab/Simulink.

Effective Surface Treatment for High‑Performance Inverted CsPbI2Br Perovskite Solar Cells with Efficiency of 15.92%

Developing high-efficiency and stable inverted CsPbI2Br perovskite solar cells is vitally urgent for their unique advantages of removing adverse dopants and compatible process with tandem cells in comparison with the regular.However,relatively low opening circuit voltage(Voc)and limited moisture stability have lagged their progress far from the regular.Here,we propose an effective surface treatment strategy with high-temperature FABr treatment to address these issues.The induced ions exchange can not only adjust energy level,but also gift effective passivation.Meanwhile,the gradient distribution of FA+can accelerate the carriers transport to further suppress bulk recombination.Besides,the Br-rich surface and FA+substitution can isolate moisture erosions.As a result,the optimized devices show champion efficiency of 15.92%with Voc of 1.223 V.In addition,the tolerance of humidity and operation get significant promotion:maintaining 91.7%efficiency after aged at RH 20%ambient condition for 1300 h and 81.8%via maximum power point tracking at 45°C for 500 h in N2.Furthermore,the unpackaged devices realize the rare reported air operational stability and,respectively,remain almost efficiency(98.9%)after operated under RH 35%for 600 min and 91.2%under RH 50%for 300 min.

Starting Characteristics of Motor in Inverter-Motor Drive System

When the induction motor is fed from the PWM VSI inverter, with and without torque enhancing function, the variations of the starting torque and the starting current versus the starting frequency are analyzed, based on the steady state equivalent circuit of the induction motor.The corresponding expressions are derived, and the corresponding curves are also drawn, from which the initial starting frequency range can be determined properly and easily. The initial starting frequency range is the common range, in which the starting torque should be high enough and the starting current low enough.Some other useful formulas are also derived.These results are significant for electrical drive designers to make the starting schemes. The effects of the increase of the stator and the rotor resistances on the starting torque and the initial starting frequency range are also discussed, which is caused by the skin effects of the high order harmonics present in the PWM inverter output voltage.

Coordinated Control for Harmonic Mitigation of Parallel Voltage-source Inverters

The increasing use of power electronic devices can deteriorate the power quality by introducing voltage and current harmonics.In islanded microgrids,the presence of nonlinear loads can distort the point of common coupling(PCC)voltage,while the dead-time effect can also bring additional circulating current harmonics among parallel inverters.To simultaneously attenuate the PCC voltage harmonics and suppress the dead-time induced circulating current harmonics,this paper proposes a coordinated control strategy for harmonic mitigation of parallel inverters.The proposed control strategy allows inverter impedances to be properly reshaped at selective harmonic frequencies.As a consequence,the PCC voltage harmonics are filtered by the inverter operating in the harmonic compensation mode(HCM),whereas the dead-time induced circulating current harmonics are suppressed by the inverter operating in the harmonic rejection mode(HRM).Experimental results from an islanded microgrid prototype with two parallel inverters are provided to validate the effectiveness of the proposed control strategy.

高管薪酬结构与企业创新——基于高管风险承担视角

创新是企业获得技术优势的重要行为,有助于国家实现高水平科技自立自强,高管是企业做出创新决策的主体。以2008—2021年中国沪深A股上市公司为研究对象,对高管薪酬结构影响企业创新的效应及作用机制进行了实证检验。研究发现,随着高管薪酬结构中股权薪酬比例的提升,企业创新投入水平呈先上升后下降的倒“U”型趋势。进一步地,以激励物的Delta指数和Vega指数为度量的高管风险承担在薪酬结构影响企业创新的路径中发挥了中介作用。异质性分析表明,高管股权薪酬对企业创新的正向激励效果仅显著存在于非国有企业和位于高市场化程度地区的企业当中。因此,企业要制定合理的薪酬结构,适当提高股权薪酬占比,并注重改善激励环境提升高管的风险承担能力,为企业创新创造良好的内外部环境。

火灾下面内约束钢筋混凝土简支双向板力学响应机理

现有分析方法对火灾下面内约束简支双向板的开裂、变形响应以及面内约束导致抗火性能降低的机理缺乏合理解释,本文应用ABAQUS有限元软件对火灾下面内约束钢筋混凝土简支双向板的温度场和热力耦合场进行了三维实体有限元分析,在实验验证基础上进行参数分析,探究钢筋和混凝土的挠度、应力变化规律和力学响应机理.结果表明:在火灾下,面内约束力削弱了板的倒拱效应与拉力膜效应,导致抗火性能显著降低.单向和双向面内约束、长宽比、荷载比的增大均会缩短板的倒拱效应与拉力膜效应阶段的时间.

高雷诺数下倒虹吸闸墩绕流水力特性

为研究倒虹吸出口闸墩绕流特性,以南水北调某典型倒虹吸为例,基于Flow3D软件建立倒虹吸模型,根据现场原型实测水位、流速进行模型验证;利用该模型模拟了雷诺数6.17×10^(6)~9.38×10^(6)范围下闸墩绕流特性。结果表明,高雷诺数条件下,随着雷诺数的增加,闸墩绕流造成的液面波动幅度增加,中墩液面波动显著大于边墩;闸墩后的尾涡量持续增加,雷诺数对斯特劳哈尔数影响不大;边侧闸墩受力的非对称性明显,边墩闸室间特征流速偏流比存在先增大再减小的变化规律,偏流效应造成的离心距不断增加。本研究可针对性改善输水工程水流流态。

基于有效感受野和注意力融合机制的脑肿瘤全自动分割

深度学习在医学图像分割领域取得了显著成果,但其在脑肿瘤分割任务中,仍面临感受野不足、冗余信息过多、信息丢失等问题;为此,本研究提出一种基于编-解码结构的脑肿瘤分割网络模型(EAU-Net)。EAU-Net采用有效感受野拓展模块和注意力融合模块改善脑肿瘤分割网络感受野不足与冗余信息过多带来的不利影响;同时,引入基于倒残差结构的瓶颈重采样模块,有效避免上下采样时造成的信息损失,并采用深度卷积降低网络的计算量。在BraTS2020数据集上的实验结果表明,EAU-Net获得最优的分割精度,验证了其在脑肿瘤分割任务中的可行性和有效性。

企业规模、市场竞争与企业数字化转型——熊彼特假说的再考察

在数字技术快速发展的背景下,数字化转型成为企业提高竞争力、实现高质量发展的必然要求。本文基于熊彼特假说视角,利用2011~2022年我国沪深A股上市公司数据,分析企业规模和市场竞争对企业数字化转型的影响。研究发现:企业规模对企业数字化转型具有非线性促进作用,且边际效应递减;市场竞争和企业数字化转型之间呈“倒U型”关系,即在某一市场竞争程度下,企业数字化转型意愿达到峰值,超过这一阀值,企业的数字化转型意愿逐渐降低。异质性检验表明,若企业是国有企业或制造业企业,企业规模对数字化转型的推动效应具有稳定性。进一步分析发现,企业规模与市场竞争的交互作用会抑制企业数字化转型。据此,本文提出促进企业数字化转型的对策建议。

提高LCL型并网逆变器鲁棒性的延时补偿策略

在LCL型并网逆变器中,数字控制延迟会影响传统电容电流反馈有源阻尼(CCFAD)的有效阻尼区间,LCL滤波器的谐振频率必须低于系统采样频率的1/6,否则虚拟阻抗对应的虚拟电阻为负值,影响系统的稳定性。针对此问题,提出了一种扩展CCFAD的有效阻尼区间的控制策略,在一阶相位超前补偿器的基础上加入积分环节,理论分析证明了所提控制策略可以将虚拟电阻呈正阻尼特性的区域扩展到(0,0.35fs),进一步扩大了有效阻尼区间。同时,提出了一套参数设计方法,根据稳定裕度约束条件得到补偿器参数的可取值范围。最后通过仿真和实验表明,在弱电网下该控制策略相比传统CCFAD控制策略具有更好的鲁棒性,验证了所提控制策略的正确性和有效性。

数字经济发展与共同富裕:理论分析及经验证据

文章基于2011—2019年我国30个省份的面板数据,运用面板固定效应模型、门槛效应模型和空间计量模型,就数字经济发展对共同富裕的影响效应进行实证检验。研究发现:(1)我国数字经济发展对共同富裕的影响呈现先促进后抑制的“倒U”型特征,拐点处的数字经济发展指数约为0.975。现阶段,我国数字经济发展对共同富裕具有促进作用。(2)数字经济发展对共同富裕的影响存在门槛效应。一方面,对外开放度越高,数字经济发展对共同富裕的抑制作用越显著;另一方面,数字经济发展对共同富裕的抑制作用会随着政府干预力度的加大而弱化。(3)数字经济发展对本地共同富裕的影响存在显著的先促进后抑制的非线性效应,但对邻近地区共同富裕的空间溢出效应不明显。

基于55 nm DICE结构的单粒子翻转效应模拟研究

单粒子翻转(single event upset,SEU)是器件在辐照空间中应用的关键难题,本文以55 nm加固锁存单元为研究载体,通过三维数值模拟方法,获得了重离子不同入射条件下的线性能量转移(linear energy transfer,LET)阈值和电压脉冲变化曲线,研究了双互锁存储单元(dual interlockded storage cell,DICE)的抗辐照性能和其在不同入射条件下的SEU效应.研究表明,低LET值的粒子以小倾斜角入射器件时,降低了器件间的总电荷收集量,使得主器件节点的电压峰值和电压脉宽最小,器件SEU敏感性最低;由于空穴与电子迁移率的差异,导致DICE锁存器中Nhit的入射角敏感性远大于Phit;合理调节晶体管间距可以削弱电荷共享效应,使得从器件总电荷收集量减小,仿真计算得到此工艺下晶体管间距不能小于1.2μm.相关仿真结果可为DICE锁存单元单粒子效应的物理机制研究和加固技术提供理论依据和数据支持,有助于加快存储器件在宇航领域的应用步伐.

对外直接投资对创新绩效的影响——基于动态整合能力的倒U型调节效应

在全球经济一体化和“大众创业、万众创新”的大背景下,我国上市公司的创新意识和创新能力不断增强。而上市公司如何通过对外直接投资影响企业创新绩效具有重要研究价值。基于此,本文通过我国2007-2020年2123家上市公司数据,使用双重差分法实证检验上市公司对外直接投资对创新绩效的影响及动态整合能力的影响机制。研究结果发现:上市公司对外直接投资对企业创新绩效有显著的正向影响,且这种正向作用存在动态性与持续性,并会受到所有制性质、地区、行业的影响。并且,企业动态整合能力在对外直接投资与创新绩效的关系中起到倒U型调节作用,但在动态整合能力强与动态整合能力弱的公司出现影响机制的差异性。据此,分别从政府管理创新成果与公司强化动态整合能力方面提出相关可行建议。

太阳能光伏在公交停保场中的应用

本文介绍了太阳能光伏系统的基本知识,如设备选型、孤岛效应等;并对如何计算光伏板安装面积和板间距以及逆变器所带组件数量等做了详细介绍;最后以一个公交停保场屋顶光伏系统设计项目为实例,论述了如何结合项目特点合理设计光伏系统和布置光伏组件。

改良切口与传统切口治疗腮腺良性肿瘤的疗效比较

目的 基于多准则决策模型探讨改良切口与传统切口治疗腮腺良性肿瘤的疗效。方法 回顾性选择2019年4月至2022年4月于成都市中西医结合医院采用手术治疗的98例腮腺良性肿瘤患者为研究对象,将采用倒“V”型切口治疗的患者作为改良组,采用“S”形切口治疗的患者作为传统组,两组各49例。比较两组年龄、性别、病理结果、病变部位、手术时间、手术出血量等一般资料;比较两组视觉模拟评分法(VAS)评分、焦虑自评量表(SAS)评分、术后面瘫分级、术后3个月的疗效;比较两组面瘫、涎瘘等术后并发症发生情况。建立改良术式治疗腮腺良性肿瘤的多准则决策模型,并对两组效益值、风险值及决策模型的稳定性进行评价。结果 改良组患者的手术切口长度、术后皮肤表面瘢痕长度、VAS评分及SAS评分与传统组比较,差异均有统计学意义(P<0.05);改良组与传统组的平均效益值分别为83、55,改良组的效益值100%优于传统组;改良组与传统组的平均风险值分别为75、57,改良组的风险值100%低于传统组;改良组与传统组的平均效益-风险总值分别为79、56,改良组的总效益-风险值高于传统组的概率为100%;多准则决策评价模型稳定性较好。结论 倒“V”型切口能明显改善腮腺良性肿瘤患者术后面颈部的美观度,提高患者的生活质量及幸福指数。

倒h形抗滑桩在沿河道路岸坡加固过程中的应用研究

以环环湖公路建设项目为依托工程,分析了以数值模拟的方法对比分析了锚索抗滑桩和倒h形抗滑桩在加固沿湖岸坡的效果。研究分析发现,采用倒h形抗滑桩对河湖岸坡边坡进行加固时,坡体滑动范围、位移量、桩身位移与桩身弯矩均处于较低水平,且支挡效果较好,由此可知,倒h形抗滑桩在加固沿湖岸坡方面具有一定的优越性。

逆变器模型分析及死区补偿控制策略研究

研究并设计一种交流伺服系统内电压源型逆变器死区补偿控制策略,根据电机驱动系统逆变器结构模型,考虑逆变器内开关器件及输出特性,以抑制死区效应,改善逆变器输出电流为目标,分析得出电压源型逆变器死区补偿控制算法。该方法根据电机电磁响应远超前机械响应的特性,考虑死区时间影响,建立电机dq轴下电压动态方程,并构建定子感应电动势变化量与dq轴电流变化的关系,从而计算得出死区扰动补偿电压,并实现在线死区补偿,仿真结果表明,所提方法可有效降低电机相电流谐波畸变率,改善电流波形正弦度,抑制电磁转矩脉动,从而提升系统电流控制性能。