Study on Identification of Inductive-Motors Load Partition Based on Coherence

A new inductive motors load equivalence algorithm based on coherence is proposed in this paper. In order to partite motors load rapidly and accurately, fuzzy c-means clustering along with particle swarm optimization (PSO-FCM) algorithm is proposed to identify coherent motors base on its physical essence of fuzziness. The merits of PSO algorithm are independent to initial value and convergent to optimum value rapidly, and the validity function is constructed to assess clustering validity. The test on IEEE 39-Bus System is presented to evaluate the effectiveness of the new algorithm, the membership matrix definite not only coherence group of motors but also correlation value of coherence between motors. The algorithm can be used to partite motor load based on coherency in dynamic equivalence with power system operating on different modes.

Crack dynamic propagation properties and arrest mechanism under impact loading

Crack dynamic propagation and arrest behaviors have received extensive attention over the years.However,there still remain many questions,e.g.under what conditions will a running crack come to arrest?In this paper,drop weight impact(DWI)tests were conducted to investigate crack arrest mechanism using single cleavage triangle(SCT)rock specimens.Green sandstone was selected to prepare the SCT specimens.Dynamic stress intensity factors(DSIFs)were calculated by ABAQUS code,and the critical DSIFs were determined by crack propagation speeds and fracture time measured by crack propagation gauges(CPGs).The test results show that the critical DSIF at propagation decreases with crack propagation speed.Numerical simulation for SCT specimens under different loading waves was performed using AUTODYN code.The reflected compressive wave from the incident and transmitted plates can induce crack arrests during propagation,and the number of arrest times increases with the wave length.In order to eliminate the effect of the incident and transmitted plates,models consisting of only one SCT specimen without incident and transmitted plates were established,and the same trapezoid-shaped loading wave was applied to the SCT specimen.The results show that for the SCT specimen with transmitted boundary(analogous to an infinite plate),the trapezoid-shaped loading wave cannot induce crack arrest anymore.The numerical results can well describe the occurrence of crack arrest in the experiments.

Determination of conditions for stable operation of induction motor resistance load using load flow and fuzzy techniques

Discusses the significance of induction motor constant resistance (IM R) load on the lower part of the PV curve of a power system and determines the conditions for stable operation of IM R load using fuzzy techniques and load flow.

Probabilistic Load Flow Algorithm with the Power Performance of Double-Fed Induction Generators

Probabilistic load flow(PLF)algorithm has been regained attention,because the large-scale wind power integration into the grid has increased the uncertainty of the stable and safe operation of the power system.The PLF algorithm is improved with introducing the power performance of double-fed induction generators(DFIGs)for wind turbines(WTs)under the constant power factor control and the constant voltage control in this paper.Firstly,the conventional Jacobian matrix of the alternating current(AC)load flow model is modified,and the probability distributions of the active and reactive powers of the DFIGs are derived by combining the power performance of the DFIGs and the Weibull distribution of wind speed.Then,the cumulants of the state variables in power grid are obtained by improved PLF model and more accurate power probability distributions.In order to generate the probability density function(PDF)of the nodal voltage,Gram-Charlier,Edgeworth and Cornish-Fisher expansions based on the cumulants are applied.Finally,the effectiveness and accuracy of the improved PLF algorithm is demonstrated in the IEEE 14-RTS system with wind power integration,compared with the results of Monte Carlo(MC)simulation using deterministic load flow calculation.

Direct Torque Control of Induction Motor Load Generator

DTC （direct torque control） of induction motor drives has many outstanding performance and implementation properties. This paper presents an innovative direct torque controlled load generator based on space vector modulation suitable for the emerging applications such as electrical test benches that require extremely fast large-signal torque and dynamic responses. To realize system performance, two methods based on the classical DTC （with six-sector switch table） and the proposed twelve-sector DTC have been analyzed and used for modelling the dynamometer. The performance of the proposed dynamometer is investigated by simulating different parts of the system and results are presented for several industrial load profiles. Finally, limitations and advantages of each controller are presented and analyzed.

Step-Loading Characteristics of Gas Engine Cogeneration System Using Doubly-Fed Induction Generator in Stand-Alone Operation

Application of a DFIG （doubly-fed induction generator）, which is one of adjustable speed generators, to a gas engine cogeneration system has been investigated. To operate during a blackout as an emergency power supply is one of important roles for the gas engine eogeneration system. In the case of conventional constant speed of synchronous generator, the amount of the allowed step load is limited to around 30% of the rated power. On the other hand, DFIG is expected to increase the amount of step load during the stand-alone operation. In this paper, it has been demonstrated that an increase in the gas engine speed resulted in an increase in the maximum amount of step load using experimental equipment with a real gas engine. It has been concluded that the proposed system can improve the performance of an emergency power supply at step-loading.

Rotor broken bar fault diagnosis for induction motors based on double PQ transformation

A new rotor broken bar fault diagnosis method for induction motors based on the double PQ transformation is pre-sented. By distinguishing the different patterns of the PQ components in the PQ plane,the rotor broken bar fault can be detected. The magnitude of power component directly resulted from rotor fault is used as the fault indicator and the distance between the point of no-load condition and the center of the ellipse as its normalization value. Based on these,the fault severity factor which is completely independent of the inertia and load level is defined. Moreover,a method to reliably discriminate between rotor faults and periodic load fluctuation is presented. Experimental results from a 4 kW induction motor demonstrated the validity of the proposed method.

Distributed Model Predictive Load Frequency Control of Multi-area Power System with DFIGs

Reliable load frequency control LFC is crucial to the operation and design of modern electric power systems. Considering the LFC problem of a four-Area interconnected power system with wind turbines, this paper presents a distributed model predictive control DMPC based on coordination scheme. The proposed algorithm solves a series of local optimization problems to minimize a performance objective for each control area. The generation rate constraints GRCs, load disturbance changes, and the wind speed constraints are considered. Furthermore, the DMPC algorithm may reduce the impact of the randomness and intermittence of wind turbine effectively. A performance comparison between the proposed controller with and without the participation of the wind turbines is carried out. Analysis and simulation results show possible improvements on closed-loop performance, and computational burden with the physical constraints. © 2014 Chinese Association of Automation.

A Digital Phase Locked Loop Speed Control of Three Phase Induction Motor Drive: Performances Analysis

This paper deals with performance analysis and implementation of a three phase inverter fed induction motor (IM) drive system. The closed loop control scheme of the drive utilizes the Digital Phase Locked Loop (DPLL). The DPLL is safely implemented all around the well known integrated circuit DPLL 4046. An ex-perimental verification is carried out on one kw scalar controlled IM system drives for a wide range of speeds and loads appliance. This presents a simple and high performance solution for industrial applications.

可吸收载抗菌药物硫酸钙与生物骨水泥链珠膜诱导在儿童足跟组织缺损合并创伤性跟骨骨髓炎中的效果比较

目的:探讨可吸收载抗菌药物硫酸钙与生物骨水泥链珠膜诱导在儿童足跟组织缺损合并创伤性跟骨骨髓炎中的效果。方法:选取2018年1月~2022年12月期间某院收治的96例儿童足跟组织缺损合并创伤性跟骨骨髓炎患儿作为研究对象,根据手术方式不同分为对照组(n=54)和观察组(n=42)。对照组患儿采用合理皮瓣修复后联合生物骨水泥链珠膜诱导治疗,观察组患儿采用合理皮瓣修复后联合可吸收载抗菌药物硫酸钙治疗。比较两组患儿创面分泌物细菌培养、感染性指标[肿瘤坏死因子-α(TNF-α)、白介素-6(IL-6)、白介素-8(IL-8)、白细胞计数(WBC)、红细胞沉降率(ESR)]、视觉模拟评分法(VAS)评分、住院时间、愈合时间、并发症、感染复发率及对照组患儿再次手术情况。结果:两组患儿创面分泌物细菌培养结果提示,均以金黄色葡萄球菌为主。术后7天、14天,两组患儿WBC、ESR、IL-6、IL-8、TNF-α均降低(P<0.05),且观察组低于对照组(P<0.05)。术后1、3个和6个月,两组患儿VAS评分均降低(P<0.05),观察组患儿术后1、3个月VAS评分低于对照组(P<0.05),两组患儿术后6个月VAS评分比较无统计学差异(P>0.05)。观察组患儿住院、愈合时间均短于对照组(P<0.05)。两组患儿并发症总发生率、术后6个月感染复发率比较均无统计学差异(P>0.05)。对照组患儿均需要再次手术取出骨水泥链珠,其中9例患儿再次接受骨水泥植入。结论:合理皮瓣修复后联合可吸收载抗菌药物硫酸钙治疗可更有效减轻患儿疼痛,抑制炎症反应,促进术后康复和骨愈合。

西北核技术研究所强脉冲辐射模拟装置近年发展综述

西北核技术研究所是我国强脉冲辐射环境建设的主体单位,成立至今自主成功研制了一系列大型辐射模拟装置,形成了具有我国自主特色的辐射环境模拟体系和技术体系。近10年来,随着应用需求的持续拓展,西北核技术研究所在辐射模拟装置及其技术方面取得了新突破。本文重点介绍了西北核技术研究所近年新建成的大型强脉冲辐射模拟装置,包括大面积脉冲γ射线试验装置“云光一号”、4 MV脉冲X射线闪光照相装置“剑光二号”及强脉冲X射线试验装置等,分析了感应电压叠加、快脉冲直线变压器、多型射线负载等方面取得的最新技术进展,提出了未来强脉冲辐射模拟装置建设及其关键技术发展的初步设想。

考虑源荷特性的双馈风电机组动态减载协同调频控制

为使双馈风电机组(doubly fed induction generator,DFIG)的有功输出能响应电网频率的变化,有效参与电网频率调节,提高风电系统的稳定性,文中分析了虚拟惯性控制、下垂控制以及减载控制的基本原理,探究了相关参数对风电并网系统频率特性的影响。在此基础上,提出一种考虑系统源荷特性的动态减载协同调频控制策略。该策略结合源荷扰动情况实现减载率修正,通过MATLAB/SIMULINK仿真验证表明:当负荷波动时,该控制策略相较于固定减载调频使含风电系统在不同风速下的频率稳定性有了显著提高。

双绕组感应发电机交直流集成发电系统的自抗扰控制策略

针对双绕组感应发电机交直流集成发电系统,为实现简单易调、性能优越、负载适应力强的发电控制,该文提出一种基于线性自抗扰控制器的交直流电压控制策略,通过交流电压和直流电压与控制绕组和功率绕组的传递函数模型,构建交直流电压的线性扩张状态观测器,同时对交流电压有效值、直流电压和电压扰动进行观测,并利用电压和扰动观测值设计线性误差反馈控制律,对交直流电压进行控制。最后,通过仿真和实验验证该控制策略提高电压扰动抑制能力和负载适应性,同时各模块参数可独立设计、控制器结构简单,避免需要较多传感器及降低调参难度。

带感性负载的Buck-Boost变换器的非线性行为分析及优化控制

Buck-Boost变换器在某些参数发生变化时会呈现出丰富的非线性行为,这些行为将严重影响系统的稳定性,使得系统输出的电能质量劣化。文章基于实际变换器的负载特性,深入研究了感性阻抗负载下Buck-Boost变换器的非线性行为产生机理,提出了一种对数延迟反馈控制方法。该方法选取系统的输出延迟值与自身的值作差形成反馈信号;将该信号通过比例环节、求和环节和对数环节形成控制信号,以负反馈的形式施加于系统;最后基于稳定判据确定最优控制参数并对系统实施控制。为验证该方法的有效性,进行了大量的仿真实验,结果表明该方法能很好地抑制系统的非线性行为,扩展其稳定边界,改善系统输出的电能质量。

采用可控负荷灵敏度的DFIG并网电力系统低频振荡模式抑制

双馈感应发电机(doubly fed induction generator,DFIG)并网加剧了低频振荡(low-frequency oscillations,LFO)。电力市场和智能用电设备,使得负荷可参与阻尼控制。此时危险模式阻尼比受负荷影响,增加特征灵敏度解析表达难度。现有恒阻抗模型,不能反映综合负荷对小扰动稳定影响;异步电机模型精确,但参数辨识难度大,很难用于小扰动稳定分析。该文为避免潮流计算和稳定分析中负荷模型差异,采用ZIP负荷模型修正系统状态方程。以潮流解对负荷灵敏度为中间变量,提出危险模式阻尼比对负荷灵敏度的解析表达。引入准比例谐振控制(quasi-proportional resonance,qPR)调节负荷,相应修正阻尼比灵敏度,以改善阻尼控制的鲁棒性。仿真结果验证了所提算法的控制效果。

基于栅极限流的SiC MOSFET栅电荷测试方案

SiC MOSFET是一种高性能的电力电子器件,其开通/关断过程中积累/释放的栅电荷Q_(g)对MOSFET的开关速度、功率损耗等参数有重要影响。通常采用在栅极设置恒流源驱动,对时间进行积分的方法来测量Q_(g)。为了降低驱动复杂度,提高测试结果精度和可视性,基于双脉冲测试平台的感性负载回路,改用耗尽型MOSFET限制栅极电流实现恒流充电,对SiC MOSFET进行测试。同时利用反馈电阻将较小的栅极电流信号转换为较大的电压信号。实验结果表明:在误差允许范围(±5%)内该测试方案能较为准确地测得SiC MOSFET的Q_(g),测试结果符合器件规格书曲线。

低加速力波动感应线圈型发射器的外电路设计

感应线圈型发射器中每级驱动线圈都会对电枢产生脉冲形式的电磁推力,导致电枢在发射过程中加速力波动较大。过大的加速力峰值以及加速力波动都可能对载荷造成不利影响甚至损坏其内部携带的敏感电子器件,因而限制了感应线圈型发射器在实际工程应用中的价值。针对上述问题,提出一种多电容分时触发的新型驱动电路,并通过分析电容值和电枢触发位置变化对发射器发射效率的影响,说明了该电路的可行性。设计三种模式的驱动电路进行对比,研究结果表明:相比于其他电路触发模式,提出的分时触发模式在初始储能相同和电枢出口速度近似的情况下,电磁加速力峰值降低了2.04 kN,加速力波动降低了2.36 kN。因此,采用分时触发电容的驱动外电路,可以有效降低电枢的加速力峰值和加速力波动,并为携带敏感载荷的感应线圈型发射器的设计提供了参考价值。

一款400μm^(2)用于极短距离接收机具有中频补偿的56 Gb/s PAM4反相器型连续时间线性均衡器

高速极短距离有线数据接口是芯粒间互连的重要技术方案。传统的基于电流模逻辑的连续时间线性均衡器由于高电源电压和无源器件的使用已经无法满足芯粒间数据接口高密度、小型化、低功耗的需求。针对该问题,本文提出了一种带中频补偿的反相器型连续时间线性均衡器,可在极短距离应用中传输28 Gb/s非归零信号以及56 Gb/s四电平脉冲幅度调制信号。本设计采用28 nm CMOS工艺实现,核心面积仅为400μm^(2)。经过-9.4 dB@14 GHz的极短距离信道后,基于版图的仿真结果表明,所提出的连续时间线性均衡器使28 Gbaud的非归零信号与四电平脉冲幅度调制信号眼宽分别提升0.14 UI与0.41 UI,眼高提升328 mV与119 mV,56 Gb/s四电平脉冲幅度调制信号工况下功耗为6.12 mW。

考虑感应电机负荷特性的主动配电网电压模型预测控制

针对高比例新能源并网引发主动配电网电压越限问题,提出了一种考虑感应电机负荷特性的主动配电网电压模型预测控制方法。首先,通过建立感应电机负荷的稳态模型,分析了其有功和无功与并网点电压的耦合关系,提出考虑感应电机负荷特性的配电网状态估计方法,实现了对关键状态量的实时在线监测。然后,计及各类电压调节资源,构建考虑感应电机负荷特性的电压模型预测控制方法,并通过状态预测、滚动优化和反馈控制3个关键环节,在维持配电网电压安全的前提下,以最低调节成本实现感应电机负荷并网点电压与设定值的偏差最小化。最后,基于IEEE33节点系统算例进行仿真,验证了所提方法在提高状态估计精度、改善电压控制效果方面的有效性。

LLC谐振低频感应加热系统设计

对LLC谐振电路的电压增益、电流增益等特性进行了理论分析。通过Simulink搭建了基于LLC谐振电路的低频感应加热电源,对电路的预充滤波电路、整流电路、PID闭环控制电路、SPWM控制电路进行了仿真分析。搭建了基于LLC谐振的并联型低频感应加热电源,对电路的IGBT驱动信号、输出电流电压、工作频率和功率因素进行了测试。结果显示:加热电源的输出电压约200V,输出电流约310A,铝合金棒料加热温度超过450℃时,功率因素达到0.97。