Stability Prediction in Smart Grid Using PSO Optimized XGBoost Algorithm with Dynamic Inertia Weight Updation

Prediction of stability in SG(Smart Grid)is essential in maintaining consistency and reliability of power supply in grid infrastructure.Analyzing the fluctuations in power generation and consumption patterns of smart cities assists in effectively managing continuous power supply in the grid.It also possesses a better impact on averting overloading and permitting effective energy storage.Even though many traditional techniques have predicted the consumption rate for preserving stability,enhancement is required in prediction measures with minimized loss.To overcome the complications in existing studies,this paper intends to predict stability from the smart grid stability prediction dataset using machine learning algorithms.To accomplish this,pre-processing is performed initially to handle missing values since it develops biased models when missing values are mishandled and performs feature scaling to normalize independent data features.Then,the pre-processed data are taken for training and testing.Following that,the regression process is performed using Modified PSO(Particle Swarm Optimization)optimized XGBoost Technique with dynamic inertia weight update,which analyses variables like gamma(G),reaction time(tau1–tau4),and power balance(p1–p4)for providing effective future stability in SG.Since PSO attains optimal solution by adjusting position through dynamic inertial weights,it is integrated with XGBoost due to its scalability and faster computational speed characteristics.The hyperparameters of XGBoost are fine-tuned in the training process for achieving promising outcomes on prediction.Regression results are measured through evaluation metrics such as MSE(Mean Square Error)of 0.011312781,MAE(Mean Absolute Error)of 0.008596322,and RMSE(Root Mean Square Error)of 0.010636156 and MAPE(Mean Absolute Percentage Error)value of 0.0052 which determine the efficacy of the system.

Omnidirectional simulation analysis of thermomechanical coupling mechanism in inertia friction welding of Ni-based superalloy

The coupling between heat and pressure is the kernel of inertia friction welding(IFW)and is still not fully understood.A novel 3D fully coupled finite element model based on a plastic friction pair was developed to simulate the IFW process of a Ni-based superalloy and reveal the omnidirectional thermo-mechanical coupling mechanism of the friction interface.The numerical model successfully simulated the deceleration,deformation processes,and peak torsional moments in IFW and captured the evolution of temperature,contact pressure,and stress.The simulated results were validated through measured thermal history,optical macrography,and axial shortening.The results indicated that interfacial friction heat was the primary heat source,and plastic deformation energy only accounted for 4%of the total.The increase in initial rotational speed and friction pressure elevated the peak temperature,reaching a maximum of 1525.5K at an initial rotational speed of 2000 r/min and friction pressure of 400 MPa.The interface heat generation could form an axial temperature gradient exceeding 320K/mm.The radial inhomogeneities of heat generation and temperature were manifested in a concentric ring distribution with maximum heat flux and temperature ranging from 2/5 to 2/3 radius.The radial inhomogeneities were caused by increasing linear velocity along the radius and an opposite distribution of contact pressure,which could reach 1.7 times the set pressure at the center.The circumferential inhomogeneity of thermomechanical distribution during rotary friction welding was revealed for the first time,benefiting from the 3D model.The deflection and transformation of distribution in contact pressure and Mises stress were indicators of plastic deformation and transition of quasi-steady state welding.The critical Mises stress was 0.5 times the friction pressure in this study.The presented modeling provides a reliable insight into the thermo-mechanical coupling mechanism of IFW and lays a solid foundation for predicting the microstructures and mechanical properties of inertia friction welded joints.

The Nature of Inertia Explained Using the Field Theory

Analysis of free fall and acceleration of the mass on the Earth shows that using abstract entities such as absolute space or inertial space to explain mass dynamics leads to the violation of the principle of action and reaction. Many scientists including Newton, Mach, and Einstein recognized that inertial force has no reaction that originates on mass. Einstein calls the lack of reaction to the inertial force a serious criticism of the space-time continuum concept. Presented is the hypothesis that the inertial force develops in an interaction of two masses via the force field. The inertial force created by such a field has reaction force. The dynamic gravitational field predicted is strong enough to be detected in the laboratory. This article describes the laboratory experiment which can prove or disprove the hypothesis of the dynamic gravitational field. The inertial force, calculated using the equation for the dynamic gravitational field, agrees with the behavior of inertial force observed in the experiments on the Earth. The movement of the planets in our solar system calculated using that equation is the same as that calculated using Newton’s method. The space properties calculated by the candidate equation explain the aberration of light and the results of light propagation experiments. The dynamic gravitational field can explain the discrepancy between the observed velocity of stars in the galaxy and those predicted by Newton’s theory of gravitation without the need for the dark matter hypothesis.

Inertial Entropy and External Validation of Clusterings

Axiomatization of Shannon entropy is a subject that has received lots of attention in the information theory literature.While Shannon entropy is defined on probability distribution,we define a new type of entropy on the set of partitions of finite subsets of metric spaces,which has a rich algebraic structure as a partially ordered set.We propose an axiomatization of an entropy-like measure of partitions of sets of objects located in metric spaces,and we derive an analytic expression of this new type of entropy referred to as inertial entropy.This approach starts with the notion of inertia of a partition and includes a study of the behavior of the sum of square errors of a partition.In this context,we characterize the chain of partitions produced by the Ward hierarchical clustering method.Starting from inertial entropies of partitions,we introduce conditional entropies which,in turn,generate metrics on partitions of finite sets.These metrics are used as external validation tools for clusterings of labeled data sets.The metric generated by inertial entropy can be used to validate data clustering for labeled data sets.This type of validation aims to determine to what extend labeling of the data coincides with the clustering obtained algorithmically,and we obtain a high degree of consistency of the data labeling with the results of several hierarchical clusterings.

Modeling and analysis of an inextensible beam with inertial and geometric nonlinearities

The present study focuses on an inextensible beam and its relevant inertia nonlinearity,which are essentially distinct from the commonly treated extensible beam that is dominated by the geometric nonlinearity.Explicitly,by considering a weakly constrained or free end(in the longitudinal direction),the inextensibility assumption and inertial nonlinearity(with and without an initial curvature)are introduced.For a straight beam,a multi-scale analysis of hardening/softening dynamics reveals the effects of the end stiffness/mass.Extending the straight scenario,a refined inextensible curved beam model is further proposed,accounting for both its inertial nonlinearity and geometric nonlinearity induced by the initial curvature.The numerical results for the frequency responses are also presented to illustrate the dynamic effects of the initial curvature and axial constraint,i.e.,the end mass and end stiffness.

Moments of inertia of triaxial nuclei in covariant density functional theory

The covariant density functional theory(CDFT)and five-dimensional collective Hamiltonian(5DCH)are used to analyze the experimental deformation parameters and moments of inertia(MoIs)of 12 triaxial nuclei as extracted by Allmond and Wood[J.M.Allmond and J.L.Wood,Phys.Lett.B 767,226(2017)].We find that the CDFT MoIs are generally smaller than the experimental values but exhibit qualitative consistency with the irrotational flow and experimental data for the relative MoIs,indicating that the intermediate axis exhibites the largest MoI.Additionally,it is found that the pairing interaction collapse could result in nuclei behaving as a rigid-body flow,as exhibited in the^(186-192)Os case.Furthermore,by incorporating enhanced CDFT MoIs(factor of f≈1.55)into the 5DCH,the experimental low-lying energy spectra and deformation parameters are reproduced successfully.Compared with both CDFT and the triaxial rotor model,the 5DCH demonstrates superior agreement with the experimental deformation parameters and low-lying energy spectra,respectively,emphasizing the importance of considering shape fluctuations.

Mach’s Principle Revised: Is the Inertia, and also Gravitational Interaction of Bodies, Determined by Their Long-Range Gravitational Interaction with Distant Matter in the Universe?

The work analyzes the basic assumption in Mach’s principle, namely that the inertia of material bodies is determined by their gravitational interaction with distant masses in the universe. However, while Mach’s principle is based on the so-called “long-range gravitational interaction” characterized by an infinitely large propagation velocity, our study is based on a “modified” long-range principle, assuming a very large but finite propagation velocity of the gravitational interaction between local material objects and distant matter. Thus, it is postulated that there are two types of gravitational interaction—short-range gravitational interaction between local objects and long-range gravitational interaction between local objects and distant matter in the universe, which are characterized by different propagation speeds, but with the same gravitational constant. On the basis of the modified long-range principle, a model of distant matter is built in the form of a hollow spherical layer with negligible thickness. The phenomenological assumption is made that the movement with acceleration of the local reference frame (RF) is related to a change in the spherically symmetric distribution of the lines of gravitational interaction of this RF with distant matter, which is expressed in a corresponding asymmetric distribution of the effective mass density on the hollow sphere. A simplified (idealized) model of the effective change of the hollow sphere of distant matter by cutting off separate segments of the sphere is proposed. On the basis of the model, the possibility of representing the inertial effects in three simplest types of reference frames through a corresponding gravitational interaction is considered: 1) inertial RF;2) RF moving in a straight line with constant acceleration;3) RF rotating with constant angular velocity. Expressions were obtained for the gravitational accelerations acting on the test body located inside the hollow sphere with a corresponding change (“cutting”). It is concluded that these accelerations can in a first approximation represent the inertial accelerations of the main types noted above. It is shown that in order to obtain reasonable values of the truncation parameters of the hollow sphere, it is necessary to assume that the gravitational interaction inside this sphere is not of the Newtonian type, i.e. the same depends on the distance not according to the law 1/r2, but according to modified law with a non-integer (fractional) exponent. This law corresponds to a fractal structure of the source of attraction inside the truncated sphere of distant matter. The issue of the possibility of the supposed modified long-range interaction is briefly discussed on the basis of a comparison of the finding a connection with the lines of force of the same with the “cosmic strings” assumed by a number of researchers, along which corresponding excitations (waves, particles) moving at super-light speed. The work advances the idea of the presence of unity and at the same time oppositeness of the inertia of material objects and the known gravitational interaction between them, which are generated by the properties of symmetry of the long-range gravitational interaction. Moreover, while the inertia of the bodies is due to the violation of this symmetry caused by their movement with acceleration, the gravitational interaction between the bodies is due to the aspiration to restore the symmetry of a far-reaching gravitational interaction, which is disturbed by the presence of local material bodies. In the conclusion of the work, the important physico-philosophical significance of Mach’s principle is emphasized, expressed in the understanding that not only the world of microscopic objects (“micro-world”), but also the world of huge cosmic objects (“mega-world”) can have a corresponding impact on our “macroscopic” world.

“大学物理实验”军事特色实验项目设计——以弹头转动惯量测量实验为例

面向高素质专业化新型军事人才培养的使命任务,国防科技大学物理实验课程组建设了系列军事特色实验项目.以弹头转动惯量测量为例,介绍了军事特色实验项目的教学设计,该项目在传统转动惯量测量实验的基础上进行改造,并辅以炮弹专用型转动惯量测试仪,突出实验项目的军事特色.教学设计围绕实验概述—实验原理—实验演示与讨论—实验内容与要求—自主实验—研讨与拓展等环节展开,在教学过程中通过仪器操作与讨论、课堂研讨等互动环节,提高学生对仪器以及实验的理解,提升整体教学质量.

基于虚拟同步机的新能源制氢系统协调控制策略

针对传统控制策略下新能源制氢系统缺乏惯量响应特性,难以主动参与电网调节、系统频率稳定性差等问题,提出基于虚拟同步机(virtual synchronous generator,VSG)的新能源制氢系统协调控制策略。首先,在建立新能源制氢系统模型的基础上,考虑到通过变流器并网的制氢系统惯量缺失和电解槽低功率运行的安全约束,提出基于电解槽与蓄电池的VSG控制方案,建立系统网侧VSG控制模型;其次,为防止VSG过度响应导致系统平抑新能源波动能力下降,提出考虑系统状态的VSG自适应方法;然后,针对系统功率波动影响直流母线电压稳定的问题,设计各单元控制策略,并在电解槽单元加入附加响应控制环节以缓解直流母线电压波动;最后,为实现能量合理分配,针对系统不同运行模式,提出考虑各单元运行状态的能量管理策略。仿真结果表明:所提策略充分发挥了电解槽调节能力,系统具备惯量与一次调频响应特性,频率稳定性增强等。

改进SSA优化BP神经网络的变压器故障诊断

变压器故障类型的准确诊断对保障电网的安全与稳定至关重要。针对BP神经网络与麻雀搜索算法(SSA)存在收敛缓慢和易陷入局部极值导致无法准确诊断的问题,提出将改进的麻雀搜索算法(ISSA)优化BP神经网络应用于变压器故障诊断。首先,引入非线性惯性权重和纵横交叉策略,从而提高算法的收敛速度和全局寻优能力;其次,将ISSA与传统SSA在收敛函数上进行对比分析,得到ISSA算法在迭代12次后以52%的准确率收敛,而SSA算法迭代23次后才达到25%的准确率,证明了ISSA在收敛速度和精度方面有明显提高;最后,将ISSA-BP、SSA-BP和BP诊断模型进行对比。实验结果表明,ISSA-BP模型准确率达到了97%,比SSA-BP、BP神经网络模型分别提高了4%和11%,可以认为提出的算法模型在变压器故障诊断领域具有更高的精度与良好的发展前景。

Improved spatial resolution in soil moisture retrieval at arid mining area using apparent thermal inertia

A surface soil moisture model with improved spatial resolution was developed using remotely sensed apparent thermal inertia（ATI）.The model integrates the surface temperature derived from TM/ETM＋ image and the mean surface temperature from MODIS images to improve the spatial resolution of soil temperature difference based on the heat conduction equation,which is necessary to calculate the ATI.Consequently,the spatial resolution of ATI and SMC can be enhanced from 1 km to 120 m（TM） or 60m（ETM＋）.Moreover,the enhanced ATI has a much stronger correlation coefficient（R^2） with SMC（0.789） than the surface reflectance（0.108） or the ATI derived only from MODIS images（0.264）.Based on the regression statistics of the field SMC measurement and enhanced ATI,a linear regression model with an RMS error of 1.90%was found.

数据要素如何影响企业投资行为?

数据要素进入企业生产流程可有效提升管理层对投资项目前景的认知判断,优化企业投资行为;然而,管理层的认知惯性和行动惯性会阻碍这一优化作用.基于2011—2020年中国A股制造业上市公司数据,实证检验了数据要素对企业投资行为的影响.研究发现:数据要素显著扩大企业投资规模,抑制非效率投资,减缓企业投资不足.数据要素通过监管强化来优化企业投资行为,且投资者专业化程度越高,优化作用越强.由于认知惯性和行动惯性的存在,管理层投资视野不足和实施传统竞争战略会弱化数据要素对企业投资的优化作用;当成本领先战略与差异化战略有效融合时,数据要素能够缩减单一战略带来的非效率投资.

A Fast Method to Compute the Inertia of Bezout Matrix and Its Application

In this paper, we present a fast and fraction free procedure for computing the inertia of Bezout matrix and we can determine the numbers of different real roots and different pairs of conjugate complex roots of a polynomial equation with integer coefficients quickly based on this result.

基于级联惯性负载转矩观测器的永磁伺服电机复合抗扰控制

针对永磁伺服电机在运行时位置跟踪精度差和抗干扰性能弱等问题,提出一种模型预测位置控制与非奇异快速终端滑模速度控制相结合的复合模型预测控制策略。该控制策略采用非奇异快速终端滑模设计速度控制器,以有效提高响应速度及系统鲁棒性;采用模型预测位置控制提高位置跟踪精度;同时,采用基于转动惯量观测和负载转矩观测器相结合的级联惯性负载转矩观测器观测负载转矩并进行前馈补偿,进一步提高系统的抗干扰性能。通过仿真和实验结果可得,所提复合模型预测控制可有效提高永磁伺服电机的动态响应速度和抗负载扰动能力。

基于功率量测的光伏高占比系统频率时空分布特征分析方法

目前,电力系统频率的全局响应分析通常采用系统的共模频率。然而,随着新能源在电力系统中占比的不断提高,系统惯量降低和调频资源分布不均的特征日益明显。节点间频率偏差指标能够反映系统频率在时间、空间上的分布差异。为得到准确的节点间频率偏差测量值,文中提出一种功率量测法。该方法能够在机组内部结构和控制参数未知的条件下,通过测量功率波动得到系统的频率变化情况,从而分析系统的频率时空分布特征。首先,通过仿真模型得到节点间频率偏差,分析光伏高占比系统受到扰动后的频率时空分布特征以及影响因素。然后,采用功率量测法得到频率偏差,并与锁相环、同步相量测量装置得到的节点间频率偏差进行对比,验证其准确性。最后,通过仿真和实验测试验证所提方法得到的节点间频率偏差能够有效体现系统频率的时空分布特征。

并网逆变器惯性特性与提升策略研究

目的 为解决当前大规模新能源发电并网后电力系统低惯量运行的问题,方法 对并网逆变器惯性特性进行分析,并对提升并网逆变器惯性水平的方法进行研究。首先分析电力系统中惯性的本质,推导出并网逆变器惯性水平与自身器件参数的关系,利用根轨迹法绘出以直流侧电容为变量的直流电压控制环根轨迹,结合根轨迹和不同电网工况场景对逆变器惯性水平的需求优化直流侧电容取值;然后在并网逆变器直流侧电压控制环中引入频率反馈环节,提出一种改进的逆变器直流侧电压控制策略和逆变器调制策略,进而提升并网逆变器的瞬时惯量水平,使直流侧电容根据电网频率波动情况进行充放电,抑制电网频率瞬时变化率;最后,使用MATLAB/Simulink搭建仿真平台对所提惯性提升策略进行验证。结果 结果表明,当直流侧电容取0.4 F,虚拟惯性时间常数为5 s时,与未使用本文所提控制策略相比,本文策略的系统频率跌落最大偏移量减小了0.11 Hz,平均跌落速率减小了0.035 Hz/s。结论 所提策略能有效提升并网逆变器惯性水平,抑制电网频率瞬时变化。

弹性伺服系统高阻尼位置控制

针对传统三环控制应用于弹性伺服系统存在的到位抖动和拖尾现象,建立了双惯量系统数学模型,详细分析传统结构导致位置闭环阻尼低的原因。提出调整速度环结构并结合谐振比控制的方法保证速度闭环系统的高阻尼;采用等实部配置、零极点对消和多项式法对三环参数进行设计,实现高阻尼位置闭环特性。仿真结果表明,所提高阻尼位置控制能很好抑制到位抖动,位置跟踪平滑,拖尾现象相比于传统P-PI控制得到显著改善。

变截面门槛梁刚度分析及优化设计

针对传统刚度分析方法在滑板底盘设计开发初期难以快速分析出变截面门槛梁弯曲刚度,以及刚度分析结果未达到设计目标值时优化方向不确定的问题,提出一种数值法与解析法相结合的半解析法并指明了优化方向。通过半解析法求得变截面门槛梁的弯曲刚度值,经分析可知其能够达到设计开发目标;利用有限元软件建模验证半解析法的准确性,结果表明误差在可接受范围内,证实了半解析法的有效性和可行性;提出了在设计允许范围内减小长度或增加截面惯性矩的优化建议,用以指导设计人员提升门槛梁的弯曲刚度,进一步优化车辆性能。

孕晚期MRI量化子宫指标预测产时宫缩乏力

目的观察孕晚期MRI量化分析子宫指标预测产时宫缩乏力的价值。方法回顾性纳入182名孕妇,根据分娩记录或剖宫产手术记录分为宫缩乏力组(乏力组,n=67)及无宫缩乏力组(非乏力组,n=115);比较组间MRI量化子宫指标,将组间存在统计学差异的指标纳入多因素logistic回归分析,构建预测宫缩乏力模型;采用受试者工作特征(ROC)曲线及其曲线下面积(AUC)评估模型预测效能。结果乏力组孕妇子宫手术次数、接受体外受精胚胎移植(IVF-ET)占比及剖宫产占比均高于无乏力组(P均<0.05)。乏力组孕晚期子宫上下径、宫颈长度及胎盘附着处子宫肌层厚度均大于无乏力组(P均<0.05)。子宫手术次数增加、接受IVF-ET,以及孕晚期子宫上下径增加及宫颈长度增加均为产时宫缩乏力的独立预测因素(P均<0.05),以之建立的预测宫缩乏力多因素logistic回归模型的AUC为0.733。结论孕晚期MRI量化子宫指标可用于预测产时宫缩乏力。

带悬臂板单箱双室薄壁箱梁畸变效应分析

为研究带悬臂板单箱双室薄壁箱梁的畸变效应,基于板梁框架法建立了畸变控制微分方程,给出竖向偏心集中荷载作用下该方程的初参数解,同时还导出了带悬臂板单箱双室截面箱梁畸变框架惯性矩的具体解析式.利用解析理论对悬臂梁和简支梁算例进行分析,研究结果表明:解析解与已有文献和有限元计算结果均吻合良好,验证了解析理论的正确性;通过参数分析可知,中腹板厚度越大,双室箱梁的抗畸变变形能力越强,中腹板厚度的变化对边腹板横向弯矩的影响很小,但中腹板的横向弯矩随其板厚的增大而增大,当中腹板厚度与边腹板厚度相等时,中腹板的横向弯矩可近似等于边腹板横向弯矩的2倍.