Partitioning Calculation Method of Short-Circuit Current for High Proportion DG Access to Distribution Network

Aiming at the problemthat the traditional short-circuit current calculationmethod is not applicable to Distributed Generation(DG)accessing the distribution network,the paper proposes a short-circuit current partitioning calculation method considering the degree of voltage drop at the grid-connected point of DG.Firstly,the output characteristics of DG in the process of low voltage ride through are analyzed,and the equivalent output model of DG in the fault state is obtained.Secondly,by studying the network voltage distribution law after fault in distribution networks under different DG penetration rates,the degree of voltage drop at the grid-connected point of DG is used as a partition index to partition the distribution network.Then,iterative computation is performed within each partition,and data are transferred between partitions through split nodes to realize the fast partition calculation of short-circuit current for high proportion DG access to distribution network,which solves the problems of long iteration time and large calculation error of traditional short-circuit current.Finally,a 62-node real distribution network model containing a high proportion of DG access is constructed onMATLAB/Simulink,and the simulation verifies the effectiveness of the short-circuit current partitioning calculation method proposed in the paper,and its calculation speed is improved by 48.35%compared with the global iteration method.

High Proportion Renewable Energy Supply and Demand Structure Model and Grid Impaction

In considering of high proportion of renewable energy supply in 2050, the accelerating of energy consumption gross, source and environment can affect the energy system restrict affection are stronger. Add wind and solar to electricity energy with large amount of energy source exploitation. The energy source amount per person is lower. Considering the renewable energy amount and supply, primary energy storage and structure problem is standing out. Before the wide spread of renewable energy, Using the high-carbon energy in China can pollute seriously. Chinese energy supply and demand problem is research key point. This paper researches Chinese energy supply and demand pattern system and evaluation methodology, gives out the inner and outer influencing elements. And evaluate Chinese energy supply and demand pattern from energy gross, structure, distribution and transportation. Use energy supply synthesize radar comparison chart in certain time period. From energy security, economy, clean and efficiency, analyze the benefit comparisons of Chinese energy supply and demand pattern. This energy supply and demand pattern model will give one certain theoretical analysis and practice reference to the further high proportion of renewable energy.

Double-uncertainty optimal operation of hybrid AC/DC microgrids with high proportion of intermittent energy sources

This paper applies double-uncertainty optimization theory to the operation of AC/DC hybrid microgrids to deal with uncertainties caused by a high proportion of intermittent energy sources.A fuzzy stochastic expectation economic model for day-ahead scheduling based on uncertain optimization theory is proposed to minimize the operational costs of hybrid AC/DC microgrids.The fuzzy stochastic alternating direction multiplier method is proposed to solve the double-uncertainty optimization problem.A real-time intra-day unbalanced power adjustment model is established to minimize real-time adjustment costs.Through comparative analysis of deterministic optimization,stochastic optimization and fuzzy stochastic optimization of day-ahead scheduling and real-time adjustment,the validity of fuzzy stochastic optimization based on a fuzzy stochastic expectation model is proved.

KPI-based Real-time Situational Awareness for Power Systems with a High Proportion of Renewable Energy Sources

With the increasing complexity of power systems and the widespread penetration of renewable energy sources(RES),real-time situational awareness for power systems is of great significance for operational scheduling.Considering the impact of RES on power system operations,a situational awareness key performance index(KPI)system for power systems with a high proportion of RES is proposed in this paper,which consists of reserve capacity abundance,ramp resource abundance,center of inertia(COI)frequency deviation,interface power flow margin,synthesized voltage stability,and angle stability margin.Then,the KPIs are synthesized and visualized by the decision tree method and radar chart method,respectively,for monitoring the operation states(i.e,normal,alert,and emergency states)of power systems with a high proportion of RES.Numerical simulations are conducted in a revised New England 16-machine 68-bus power system and an actual CEPRI-RE power system in the northwest region of China with a high proportion of RES.The results show that the proposed KPI-based situational awareness method is able to accurately monitor the real-time state of power systems with a high proportion of RES,and can assist power dispatchers to make effective decisions.

An efficient complex event detection model for high proportion disordered RFID event stream

With the aim of solving the detection problems for current complex event detection models in detecting a related event for a complex event from the high proportion disordered RFID event stream due to its big uncertainty arrival,an efficient complex event detection model based on Extended Nondeterministic Finite Automaton(ENFA)is proposed in this paper.The achievement of the paper rests on the fact that an efficient complex event detection model based on ENFA is presented to successfully realize the detection of a related event for a complex event from the high proportion disordered RFID event stream.Specially,in our model,we successfully use a new ENFA-based complex event detection model instead of an NFA-based complex event detection model to realize the detection of the related events for a complex event from the high proportion disordered RFID event stream by expanding the traditional NFA-based detection model,which can effectively address the problems above.The experimental results show that the proposed model in this paper outperforms some general models in saving detection time,memory consumption,detection latency and improving detection throughput for detecting a related event of a complex event from the high proportion out-of-order RFID event stream.

Mechanical properties of bimrocks with high rock block proportion

For the investigation of mechanical properties of the bimrocks with high rock block proportion,a series of laboratory experiments,including resonance frequency and uniaxial compressive tests,are conducted on the 64 fabricated bimrocks specimens.The results demonstrate that dynamic elastic modulus is strongly correlated with the uniaxial compressive strength,elastic modulus and block proportions of the bimrocks.In addition,the density of the bimrocks has a good correlation with the mechanical properties of cases with varying block proportions.Thus,three crucial indices(including matrix strength)are used as basic input parameters for the prediction of the mechanical properties of the bimrocks.Other than adopting the traditional simple regression and multi-regression analyses,a new prediction model based on the optimized general regression neural network(GRNN)algorithm is proposed.Note that,the performance of the multi-regression prediction model is better than that of the simple regression model,owing to the consideration of various influencing factors.However,the comparison between model predictions indicates that the optimized GRNN model performs better than the multi-regression model does.Model validation and verification based on fabricated data and experimental data from the literature are performed to verify the predictability and applicability of the proposed optimized GRNN model.

A Simple Mix Proportion Design Method Based on Frost Durability for Recycled High Performance Concrete Using Fully Coarse Recycled Aggregate

Durability design of recycled high performance concrete（RHPC） is fundamental for improving the use rate and level of concrete waste as coarse recycled aggregate（CRA）. We discussed a frostdurability-based mix proportion design method for RHPC using 100 % CRA and natural sand. Five groups of RHPC mixes with five strength grades（40, 50, 60, 70 and 80 MPa） were produced using CRA with four quality classes, and their workability, 28 d compressive strengths and frost resistances（measured by the compressive strength loss ratio and the relative dynamic modulus of elasticity） were tested. Relationships between the 28 d compressive strength, the frost resistance and the CRA quality characteristic parameter, water absorption, were then developed. The criterion of a CRA maximum water absorption limit value for RHPC was suggested, independent of its source and quality class. The results show that all RHPC mixes achieve the expected target workability, strength, and frost durability. The research results demonstrate that the application of the proposed method does not require trial testing prior to use.

预测视角下双因子模型与高阶因子模型的一般性模拟比较

高阶因子模型本质上是一种特殊的双因子模型,应用中却常被当做双因子模型的竞争模型。已有研究以满足比例约束的双因子模型(此时等价于一个高阶因子模型)为真实测量模型产生模拟数据,比较了用双因子模型和高阶因子模型作为测量模型的预测效果。本文使用不满足比例约束的双因子模型(此时不与任何高阶因子模型等价)为真实测量模型产生模拟数据进行比较,所得结果与满足比例约束的双因子模型的结果有很大差别,双因子模型结构系数的相对偏差较小、检验力较高,但第Ⅰ类错误率略高。结论是,在比例约束条件成立时可以使用高阶因子模型,否则,从统计角度看,一般情况下使用双因子模型进行预测比较好。

304不锈钢高温非比例多轴应变循环变形行为研究

为了对材料的高温应变循环变形行为进行精确的本构描述,在350℃和700℃下,对304不锈钢在不同加载路径下的单轴和非比例多轴应变循环变形行为进行了实验研究。讨论了材料在不同加载路径及不同工况下的循环硬化特性。研究表明：304不锈钢的高温非比例多轴应变循环变形行为具有明显的温度依赖性和路径依赖性。研究结果为后续循环本构模型的建立提供了实验基础。

304不锈钢高温非比例多轴棘轮行为实验研究

为了对材料的高温棘轮行为进行精确的本构描述,在350℃和700℃下,对304不锈钢的单轴和非比例多轴棘轮行为进行了系统的实验研究。讨论了材料在不同加载路径以及不同工况下的棘轮变形特性,揭示了304不锈钢非比例多轴棘轮行为的平均应力和应力幅值依赖性,以及温度依赖性和路径依赖性。

高精度陀螺稳定平台控制系统参数整定方法

为提高陀螺稳定平台控制系统的稳态精度、加快控制参数的整定速度,在传统的PID参数整定方法——ZN临界比例度法的基础上,运用自适应模糊控制算法与常规PID控制器结合形成自适应模糊PID控制器,并通过自适应模糊PID控制器实现控制参数的在线整定,使系统具有良好的动态和静态性能。仿真实验结果表明:与常规PID相比,自适应模糊PID控制器具有更高的稳态精度,可大幅减小动态调整时间和系统超调。

高油玉米花粉直感等遗传效应对普通玉米籽粒性状的影响

用高油玉米杂交种高油115为父本,与5个普通玉米杂交种进行杂交,研究了杂交当代籽粒的千粒重、胚重比和胚体积比。结果表明:胚重比、胚体积比和千粒重比普通玉米都有显著增加,增加量依次为1.79 %,1.99 %,10.34 %。筛选出了2个较好的组合为:郑单958×高油115,豫玉22×高油115。千粒重分别增加:33.00 g,29.13 g,胚重比分别增加:1.57 %,2.25 %,胚体积比分别增加:3.07 %,1.17 %,表明:高油玉米的花粉直感效应以及它们之间的杂种优势效应在玉米生产上有着广阔的应用前景。

高倍数泡沫灭火系统的研究

高倍数泡沫灭火系统是主动防火的重要措施之一,该系统成本低、灭火效果好,尤其对于大型机械处所灭火效果非常明显。详细研究和对比了高倍数泡沫灭火系统的相关规范要求,分析了不同系统型式的优缺点,同时研究了系统关键性部件的特性,并对关键性技术参数选取及合理性做了较为充分的论证,为该系统的开发设计提供技术支持。

Three-dimensional carbon framework as high-proportion sulfur host for high-performance lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries are anticipated as one of the most promising candidates for the highenergy-density storage systems.However,the insulating nature and shuttling effect of sulfur severely limits their performance.The incorporation of sulfur with carbon materials has been deemed as one of the most powerful strategies to improve electrical conductivity and suppress soluble polysulfide shuttling.Herein,a novel three-dimensional carbon framework(3DCF)is prepared and employed as a sulfur host(3DCF@S)for Li-S batteries.The 3DCF not only supplies abundant paths for lithium ion diffusion and electron transport,but also strengthens polysulfide immobilization during the lithium/sulfur conversion reactions.As a result,the 3DCF@S with high sulfur content of 90%exhibits a high capacity of 1366 mA h/g at 0.1 C and excellent cycling stability with a satisfactory capacity of 601 mA h/g after 600 cycles at 2.0 C.The resultant Li-S button battery based 3DCF@S electrode could power a light-emitting diode for 2 h.The acquired 3DCF@S is expected to be widely used in Li-S batteries and this study will promote developments of carbon/sulfur composites for Li-S batteries.

Physics Insight of the Inertia of Power Systems and Methods to Provide Inertial Response

The growth of renewable energy reduces the moment of inertia for the synchronous AC grid,so the authors put forward two basic questions:1)What is the physics insight that a synchronous AC grid needs for mechanical inertia?2)How to provide inertial response for the power grid dominated with renewable energy?Based on Einstein’s special relativity and the Lorentz transformation,these papers illustrates that the nature of the inertia of the AC grid comes from the relativity of the electromagnetic field and motion,and from the strong coupling between them.According to their nature,the inertial response of the synchronous generator is self-proven.By contrast,the converter for the grid-connection of renewable energies used various algorithms in order to provide virtual inertia.But because algorithms do not rebuild the coupling between electromagnetic fields and motion,it is doubtful whether they can provide inertia and inertial responses.Therefore,the authors propose that there is a need to build extra electromagnetic fields and motion coupling for grids with high penetration rates of renewable energy.Therefore,a new grid-connection technology via Motor-Generator Pair(MGP)is discussed.The electromagnetic-motion coupling of the MGP is analyzed,and the results of simulation and experimental studies are also reported.