Current optimization-based control of dual three-phase PMSM for low-frequency temperature swing reduction

In this paper,a control scheme based on current optimization is proposed for dual three-phase permanent-magnet synchronous motor(DTP-PMSM)drive to reduce the low-frequency temperature swing.The reduction of temperature swing can be equivalent to reducing maximum instantaneous phase copper loss in this paper.First,a two-level optimization aiming at minimizing maximum instantaneous phase copper loss at each electrical angle is proposed.Then,the optimization is transformed to a singlelevel optimization by introducing the auxiliary variable for easy solving.Considering that singleobjective optimization trades a great total copper loss for a small reduction of maximum phase copper loss,the optimization considering both instantaneous total copper loss and maximum phase copper loss is proposed,which has the same performance of temperature swing reduction but with lower total loss.In this way,the proposed control scheme can reduce maximum junction temperature by 11%.Both simulation and experimental results are presented to prove the effectiveness and superiority of the proposed control scheme for low-frequency temperature swing reduction.

基于VSR-VSI的电梯能量回馈系统建模与控制

基于电压源型整流器(VSR)与电压源型逆变器(VSI)整合而成的VSR-VSI双PWM变换器已在电梯能量回馈系统中得到应用。本文围绕VSR-VSI系统的直流母线电压可控与能量可双向流动的特点,首先阐述了基于VSR-VSI电梯永磁同步电机驱动系统在dq坐标系下的PI双闭环控制结构与参数设计方法,分析了VSR-VSI系统直流母线电压与并网电流存在谐波畸变的机理,在此基础上提出了基于PI+谐振(PI plus resonant,PIR)调节器的VSR电流内环改进控制策略以抑制并网电流谐波,最后利用仿真结果验证了上述理论分析的准确性与有效性。

Deciphering engineering principle of three-phase interface for advanced gas-involved electrochemical reactions

As an alternative to conventional energy conversion and storage reactions,gas-involved electrochemical reactions,including the carbon dioxide reduction reaction(CO_(2)RR),nitrogen reduction reaction(NRR)and hydrogen evolution reaction(HER),have become an emerging research direction and have gained increasing attention due to their advantages of environmental friendliness and sustainability.Various studies have been designed to accelerate sluggish kinetics but with limited results.Most of them promote the reaction by modulating the intrinsic properties of the catalyst,ignoring the synergistic effect of the reaction as a whole.Due to the introduction of gas,traditional liquid-solid two-phase reactions are no longer applicable to future research.Since gas-involved electrochemical reactions mostly occur at the junctions of gaseous reactants,liquid electrolytes and solid catalysts,the focus of future research on reaction kinetics should gradually shift to three-phase reaction interfaces.In this review,we briefly introduce the formation and constraints of the three-phase interface and propose three criteria to judge its merit,namely,the active site,mass diffusion and electron mass transfer.Subsequently,a series of modulation methods and relevant works are discussed in detail from the three improvement directions of‘exposing more active sites,promoting mass diffusion and accelerating electron transfer’.Definitively,we provide farsighted insights into the understanding and research of three-phase interfaces in the future and point out the possible development direction of future regulatory methods,hoping that this review can broaden the future applications of the three-phase interface,including but not limited to gas-involved electrochemical reactions.

Electrical characteristics of new three-phase traction power supply system for rail transit

A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit.With the application of two-stage three-phase continuous power supply structure,the electrical characteristics exhibit new features differing from the existing traction system.In this work,the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive.The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses.Based on the chain network model of the traction network,a simulation model is established to analyze the electrical characteristics such as traction current distribution,voltage losses,system equivalent impedance,voltage distribution,voltage unbalance and regenerative energy utilization.In a few words,quite a lot traction current of about 99%is undertaken by long-section cable network.The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure,and the voltage unbal-ance caused by impedance asymmetry of traction network is less than 1‰.In addition,the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.

Speed Regulation Method Using Genetic Algorithm for Dual Three-phase Permanent Magnet Synchronous Motors

Dual three-phase Permanent Magnet Synchronous Motor(DTP-PMSM)is a nonlinear,strongly coupled,high-order multivariable system.In today’s application scenarios,it is difficult for traditional PI controllers to meet the requirements of fast response,high accuracy and good robustness.In order to improve the performance of DTP-PMSM speed regulation system,a control strategy of PI controller based on genetic algorithm is proposed.Firstly,the basic mathematical model of DTP-PMSM is established,and the PI parameters of DTP-PMSM speed regulation system are optimized by genetic algorithm,and the modeling and simulation experiments of DTP-PMSM control system are carried out by MATLAB/SIMULINK.The simulation results show that,compared with the traditional PI control,the proposed algorithm significantly improves the performance of the control system,and the speed output overshoot of the GA-PI speed control system is smaller.The anti-interference ability is stronger,and the torque and double three-phase current output fluctuations are smaller.

Optimization of Control Loops and Operating Parameters for Three-Phase Separators Used in Oilfield Central Processing Facilities

In this study,the Stokes formula is used to analyze the separation effect of three-phase separators used in a Oilfield Central Processing Facility.The considered main influencing factors include(but are not limited to)the typical size of oil and water droplets,the residence time and temperature of fluid and the dosage of demulsifier.Using the“Specification for Oil and Gas Separators”as a basis,the control loops and operating parameters of each separator are optimized Considering the Halfaya Oilfield as a testbed,it is shown that the proposed approach can lead to good results in the production stage.

Purification of Moringa oleifera Leaves Protease by Three-Phase Partitioning and Investigation of Its Potential Antibacterial Activity

One of plant-based products for dental care is plant-based proteolytic enzymes which are principally proteases. In order not to damage the protein and bioactive content, an efficient method should be employed for their purifications. As such, three-phase partitioning (TPP) was used to purify protease from moringa (Moringa oleifera). TPP is an emerging, promising, non-chromatographic and economical technology which is simple, quick, efficient and often one-step process for the separation and purification of bioactive molecules from natural sources. It involves the addition of salt (ammonium sulphate) to the crude extract followed by the addition of an organic solvent (butanol). The protein appears as an interfacial precipitate between upper organic solvent and lower aqueous phases. The various conditions such as ammonium sulphate, ratio of crude extract to t-butanol and pH which are required for attaining efficient purification of the protease fractions were optimized. Under optimized conditions, it was seen that, 35% of ammonium sulphate saturation with 1:0.75 ratio of crude extract to t-butanol at pH 7 gave 4.94-fold purification with 96.20% activity yield of protease in the middle phase of the TPP system. The purified enzyme from Moringa oleifera has no antimicrobial effect on the pathogenic bacteria tested. However, this purified enzyme, can be considered as a promising agent, cheap, and safe source which is suitable for using in various industries.

Vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers under blast load

In this article,vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers subjected to blast load are studied.Higher-order ES-MITC3 element based on higher-order shear deformation theory(HSDT)to achieve the governing equations.The sandwich plates with the ultra-light feature of the auxetic honeycomb core layer(negative Poisson’s ratio)and reinforced by two laminated three-phase skin layers.The obtained results in our work are compared with other previously published to confirm accuracy and reliability.In addition,the effects of parameters such as geometrical and material parameters on the vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers are fully investigated.

Enhancing ammonia production rates from electrochemical nitrogen reduction by engineering three-phase boundary with phosphorus-activated Cu catalysts

Electrochemical N_(2) reduction reaction(eNRR) over Cu-based catalysts suffers from an intrinsically low activity of Cu for activation of stable N_(2) molecules and the limited supply of N_(2) to the catalyst due to its low solubility in aqueous electrolytes.Herein,we propose phosphorus-activated Cu electrocatalysts to generate electron-deficient Cu sites on the catalyst surface to promote the adsorption of N_(2) molecules.The eNRR system is further modified using a gas diffusion electrode(GDE) coated with polytetrafluoroethylene(PTFE) to form an effective three-phase boundary of liquid water-gas N_(2)-solid catalyst to facilitate easy access of N_(2) to the catalytic sites.As a result,the new catalyst in the flow-type cell records a Faradaic efficiency of 13.15% and an NH_(3) production rate of 7.69 μg h^(-1) cm^(-2) at-0.2 V_(RHE),which represent 3.56 and 59.2 times increases from those obtained with a pristine Cu electrode in a typical electrolytic cell.This work represents a successful demonstration of dual modification strategies;catalyst modification and N_(2) supplying system engineering,and the results would provide a useful platform for further developments of electrocatalysts and reaction systems.

Automatic measurement of three-phase contact angles in pore throats based on digital images

With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flooding experiment videos as the data source. The results of the new method were verified through comparing with the manual measurement data.On this basis, the dynamic changes of the three-phase contact angles under flow conditions were clarified by the contact angles probability density curve and mean value change curve. The results show that, for water-wetting rocks, the mean value of the contact angles is acute angle during the early stage of the water flooding process, and it increases with the displacement time and becomes obtuse angle in the middle-late stage of displacement as the dominant force of oil phase gradually changes from viscous force to capillary force. The droplet flow in the remaining oil occurs in the central part of the pore throats, without three-phase contact angle. The contact angles for the porous flow and the columnar flow change slightly during the displacement and present as obtuse angles in view of mean values, which makes the remaining oil poorly movable and thus hard to be recovered. The mean value of the contact angle for the cluster flow tends to increase in the flooding process, which makes the remaining oil more difficult to be recovered. The contact angles for the membrane flow are mainly obtuse angles and reach the highest mean value in the late stage of displacement, which makes the remaining oil most difficult to be recovered. After displacement, the remaining oils under different flow regimes are just subjected to capillary force, with obtuse contact angles, and the wettability of the pore throat walls in the microfluidic model tends to be oil-wet under the action of crude oil.

Application of CD34 expression combined with three-phase dynamic contrast-enhanced computed tomography scanning in preoperative staging of gastric cancer

BACKGROUND Accurate preoperative staging of gastric cancer(GC),a common malignant tumor worldwide,is critical for appropriate treatment plans and prognosis.Dynamic three-phase enhanced computed tomography(CT)scanning for preoperative staging of GC has limitations in evaluating tumor angiogenesis.CD34,a marker on vascular endothelial cell surfaces,is promising in evaluating tumor angiogenesis.We explored the value of their combination for preoperative staging of GC to improve the efficacy and prognosis of patients with GC.Medical records of 106 patients with GC treated at the First People's Hospital of Lianyungang between February 2021 and January 2023 were retrospectively studied.All patients underwent three-phase dynamic contrast-enhanced CT scanning before surgery,and CD34 was detected in gastroscopic biopsy specimens.Using surgical and pathological results as the gold standard,the diagnostic results of three-phase dynamic contrast-enhanced CT scanning at different T and N stages were analyzed,and the expression of CD34-marked microvessel density(MVD)at different T and N stages was determined.The specificity and sensitivity of three-phase dynamic contrast-enhanced CT and CD34 in T and N staging were calculated;those of the combined diagnosis of the two were evaluated in parallel.Independent factors affecting lymph node metastasis were analyzed using multiple logistic regression.RESULTS The accuracy of three-phase dynamic contrast-enhanced CT scanning in diagnosing stages T1,T2,T3 and T4 were 68.00%,75.00%,79.41%,and 73.68%,respectively,and for diagnosing stages N0,N1,N2,and N3 were 75.68%,74.07%,85.00%,and 77.27%,respectively.CD34-marked MVD expression increased with increasing T and N stages.Specificity and sensitivity of three-phase dynamic contrast-enhanced CT in T staging were 86.79%and 88.68%;for N staging,89.06%and 92.86%;for CD34 in T staging,64.15%and 88.68%;and for CD34 in N staging,84.38%and 78.57%,respectively.Specificity and sensitivity of joint diagnosis in T staging were 55.68%and 98.72%,and N staging were 75.15%and 98.47%,respectively,with the area under the curve for diagnosis improving accordingly.According to multivariate analysis,a longer tumor diameter,higher pathological T stage,lower differ-entiation degree,and higher expression of CD34-marked MVD were independent risk factors for lymph node metastasis in patients with GC.CONCLUSION With high accuracy in preoperatively determining the invasion depth and lymph node metastasis of GC,CD34 expression and three-phase dynamic contrast-enhanced CT can provide a reliable basis for surgical resection.

10Gbit/s甚短距离(VSR)并行光传输系统

介绍了一个适用于甚短距离(Very Short Reach,VSR)网络传输的并行光传输系统。系统的发射部分用垂直腔面发射激光器(Vertical Cavity Surface Emitting La-ser,VCSEL)1×12列阵代替传统的边发射激光器,接收部分也采用相应的探测器列阵,并由多模光纤列阵相连接,在300m距离内以单信道1.25 Gbit/s速率实现的10Gbit/s的高传输速率。

VSR直流侧滤波电容的计算及实验分析

针对直流侧滤波电容是VSR的重要部件,须根据系统性能的要求进行计算的情况,分析了VSR滤波电容的作用,在考虑系统的快速跟随能力和抗负载扰动性能的情况下,分别给出了电容的计算方法,并结合工程实际确定了电容的取值范围.仿真及实验结果证明了所做分析计算的正确性.

基于优化SVPWM三相VSR的仿真与研究

介绍了三相电压型PWM整流器(VSR)的拓扑结构和电压定向控制(VOC)的基本原理。针对三相VSR传统中电压空间矢量(SVPWM)算法的缺陷性,提出了一种优化SVPWM调制方法。该方法利用电压空间矢量旋转的幅角来判断扇区,并由相电压的电压差值计算基本电压矢量的作用时间,完全省略了坐标变换和三角函数计算,化简了SVPWM算法步骤。经过MATLAB/SIMULINK建立电压定向控制(VOC)仿真模型,可以证明该优化SVPWM算法的正确性,为改进三相VSR的硬件设计提供了依据。

一种提高三相VSR直流母线电压控制能力的方法

在三相VSR系统中,当直流母线电压跌落较大时会导致交流侧电压饱和,从而引起交流侧电流畸变和系统的动态响应变差。针对该问题,通过分析三相VSR直流侧电压对交流侧电流的影响以及交流侧矢量关系,提出从电网吸收或向其注入一定无功功率的方法。同时给出了给定无功电流的选取方法。实验结果表明,当直流母线电压跌落并导致变换器交流侧电压饱和时,所提方法可使交流侧电压降低到线性调制区域,降低了交流侧电流的畸变率,改善了系统的动态响应。

基于非线性积分滑模变结构控制三相VSR的研究

为了提高三相电压型PWM整流器(VSR)对系统参数变化及负载扰动的能力,在传统积分滑模的基础上,提出非线性积分滑模变结构控制策略。该控制策略含有误差和误差积分项,减小稳态误差和抖振的同时又能提高系统的鲁棒性,并在此基础上对积分项进行削弱,防止积分饱和效应(windup)带来超调过大及响应时间过长的问题。采用指数趋近律,提高滑模面上的运动品质,以进一步削弱抖振效应。最后仿真结果表明,非线性积分滑模变结构控制策略与传统积分滑模、双闭环PI相比,该方法使系统具有超调小和更好的抗扰性、跟踪能力。

基于网侧功率平衡的电网不对称时三相VSR控制方法研究

对三相VSR在电网电压不对称条件下进行建模分析。在网侧功率平衡的基础上,基于正、负旋转坐标系下双电流环控制策略对直流侧电压进行了研究。仿真结果表明,这种控制策略可有效抑制因电网电压不对称所导致的三相VSR直流侧电压二次谐波。

三相VSR的一种改进型前馈补偿控制策略研究

根据三相电压型PWM整流器(VSR)工作原理,工程上常采用传统的电压电流双闭环控制系统,其存在启动时电压过冲、抗干扰能力弱、功率因数降低等问题。为此,提出了在电流内环引入有功电压前馈补偿,在电压外环引入负载电流前馈补偿的控制思想,优化了dq坐标系下的电压电流双闭环控制策略,抑制了启动过程中的电压过冲、增强了系统的抗干扰能力,提高了功率因数。最后通过Matlab/Simulink软件仿真分析,仿真结果验证了改进后的控制策略的可行性和有效性。

基于并行光学互连的OC-192接口VSR技术及其应用

论述了OC-192接口VSR技术的基本原理,对四种VSR标准做了简单的比较,讨论了VSR的应用。

国家公园生态系统健康测度模型构建及黄山实证研究

国家公园是中国生态文明建设的重要制度实践,其生态系统健康的科学评估是国家公园分区管理、空间管制、生态保护的基础。国家公园生态系统具有特殊性和复合性,区别于城市、流域、湿地等生态系统,亟需建立一套适合国家公园生态系统的生态系统健康测度模型。基于国家公园生态系统的特殊性和生态系统健康概念的多维性,探讨了现有模型存在的问题和不足,从生态系统与人类活动交互的视角,建立了“VSR”(生态活力Vigor、服务能力Service、抗干扰力Resilience)国家公园生态系统健康测度模型。此外,将“VSR”模型应用到黄山国家公园生态系统健康的测度中,可视化了黄山国家公园生态系统健康的时空过程和格局,通过随机森林回归模型和增强回归树模型验证了“VSR”模型的有效性和稳定性。“VSR”国家公园生态系统健康测度模型有效量化了国家公园生态系统健康的时空差异性和时空动态性,为国家公园空间管制、生态保护等目标实施提供了科学支撑。