In the realm of large-scale integration of wind farms or clusters into power grids, the fault transient characteristics of these grids have experienced significant transformations. Unfortunately, the prevalent single-machine equivalent models are inadequate in accurately depicting the fault transient behavior of wind farms or clusters. Moreover, their simulation computations are exceedingly intensive, resulting in suboptimal simulation efficiency. To address these challenges, this paper introduces a clustering and equivalent modeling approach tailored for direct-drive wind farms, leveraging the capabilities of a particle swarm neural network. Initially, a transient model for direct-drive wind turbines is formulated, and fault characteristic influence factors are established through theoretical analysis. These factors encompass the distance between the wind turbine and the point of common coupling (PCC), the implementation of DC-side current limiting measures, wind speed, and reactive power at the outlet. Following this, the Euclidean distance of the influence factor set is computed, and the initial cluster centers of wind turbines are derived using an enhanced max-min distance method. Ultimately, an equivalent clustering model is formulated by utilizing the influence factors and initial cluster centers as the training set. Simulation outcomes reveal that, in comparison to the single-machine equivalent model, this method enhances simulation efficiency by a range of ${6 2 \%}$ to ${6 7 \%}$ and reduces the steady-state error in fault current simulation by ${0 . 8 \%}$ to ${1 . 9 \%}$.

Transient simulation in power engineering is crucial as it models the dynamic behavior of power systems during sudden events like faults or short circuits. Electromagnetic transient simulations involve multiple coordinated tasks. Traditional simulations are centralized and struggle to meet scalability requirements. To achieve these goals, distributed electromagnetic transient simulation has emerged as a new trend. Nevertheless, the distributed electromagnetic transient simulation introduces network communication. Achieving real-time simulation across distributed nodes poses the challenge of minimizing communication costs. In this paper, our proposal focuses on optimizing the task orchestration to reduce communication costs. Specifically, in the electromagnetic transient simulation, these tasks has certain communication pattern where the communicated objects of each task are pre-defined. We represent the pattern as a graph, with tasks represented as nodes and communications as edges. Furthermore, we propose to use graph partition with the objective of minimal communication costs and fine tune the partitions with the resource requirements of each distributed node. The experimental results demonstrate that our proposal has strength in achieving high-performance electromagnetic transient simulation.

The fault transient characteristics of power grids have undergone a fundamental transformation as a consequence of the advent of hybrid scale access to power grids by new energy sources. Nevertheless, the existing stand-alone equivalent model is unable to accurately characterise the fault transient characteristics of the hybrid light-water-wind electric field/cluster. Furthermore, the simulation computation of the stand-alone equivalent model is considerable in scale and the simulation efficiency is low. This paper proposes a particle swarm neural network-based clustered equivalent modelling method for a light-water-wind hybrid electric field. Firstly, a transient model of the light-water-wind hybrid electric field is established, and the characteristic influence factors of faults are constructed through theoretical analysis. These include the distance between the light-water-wind hybrid electric field and the point of common coupling (PCC), the input of current limiting measures on the DC side, the light, the water speed, the wind speed, and the reactive power at the outlet. Subsequently, the Euclidean distance is calculated for the set of characteristic influencing factors, and the initial centre of clustering of wind turbines is extracted based on the improved maximum-minimum distance method. Ultimately, the clustering equivalent modelling is accomplished through the utilisation of the aforementioned feature influencing factors and the classification initial centre as the training set. The simulation results show that compared with the single-machine equivalent model, The simulation error has been reduced from the order of magnitude of 10-2 p.u. to the order of magnitude of 10-4 p.u., while the simulation efficiency of this method is has been reduced from the order of magnitude of 10-2 s to the order of magnitude of 10-4 s.

With the widespread application of Distributed Photovoltaics (DPV) within the distribution network, issues related to voltage exceedance and voltage fluctuations have become increasingly grave. To effectively address these challenges, this paper proposes a coordinated control methodology for reactive power compensation in the distribution network, integrating the Flexible Load Tap Changer (OLTC). This approach consists of two distinct phases. The first phase involves hourly scheduling, wherein flow calculations and iterative optimizations are conducted based on predictive data for distributed photovoltaics and load, allowing for the determination of the operational status of critical equipment. The second phase focuses on minute-level reactive power optimization, which refines the distribution of reactive power among nodes by leveraging the reactive power characteristics of the flexible OLTC and DPV, thus enhancing voltage conditions. Validation through simulations on the IEEE 33-node distribution system model reveals that the proposed methodology demonstrates significant efficacy and rationality in voltage reactive power optimization and economic improvement.

Addressing the stability challenges posed by the unpredictability and intermittent nature of wind power output during grid integration, and aiming to enhance the understanding of factors influencing grid stability upon wind power system connection and to implement efficient control measures, a grid- connected model of a doubly fed induction generator (DFIG) was established utilizing a customized version of the RTRES (Real-Time Power System Simulation) software, specifically designed for emerging power systems and aligned with wind farm realities. Stability simulations for grid connection were conducted under both voltage regulation mode and reactive power regulation mode across a range of wind speeds, revealing distinct technical behaviors. The findings suggest that the generator's terminal voltage, terminal current, active power, reactive power, and rotor speed exhibit strong correlations with variations in wind speed, and that all parameters are capable of stabilizing following initial disturbances.

The rapid development of renewable energy needs the effective support of simulation technology. Aiming at the shortage of both modeling scale and simulation accuracy of the current large-scale photovoltaic power station, an electromagnetic transient modeling and real-time simulation method suitable for large-scale photovoltaic power stations are proposed. The microsecond accurate real-time simulation of 24 photovoltaic power units is implemented on a single FPGA. Through an equivalent modeling method, the electromagnetic transient model of a photovoltaic power unit including a PV array, DC boost circuit, grid-connected inverter, filter, and grid-side transformer is established. Then, based on the FPGA parallel computing and pipeline time division multiplexing technology, the updating framework of the station collecting network and the power unit is constructed, and the real-time simulation model of the station including 24 photovoltaic power units in 4 sub-stations is built. Finally, the microsecond real-time simulation of the photovoltaic power station is realized through RTRES, a self-developed real-time simulator in China’s Southern Power Grid. The comparison with the detailed PSCAD model shows that the simulation error is within ± 2%, which verifies the correctness of the proposed method and model.

Aiming at the problems of complex design, low scalability and low reusability of resources in the power simulation system, a middle-platform design scheme based on domain-driven design and microservice data is proposed. Through an in-depth study of domain-driven design theory and the characteristics of microservices, this paper proposes a middle-platform design scheme for the power simulation system based on exploring the structure of the power simulation system and the system domain-driven model, and combining the functional requirements and structural characteristics of the simulation software. Finally, this paper verifies that the middle-platform construction of the power simulation system based on domain-driven design and microservices has the characteristics of high scalability, high maintainability and high reusability of resources through the application and analysis of typical business scenarios of power simulation.

A neutronic experiment has been performed using DT neutrons on a blanket mockup of the hybrid tritium breeding blanket (HTBB) at CAEP. As a backup blanket configuration for CFETR, HTBB design which uses uranium alloy, water coolant and ceramic breeder pebble bed has been proposed to obtain high tritium breeding ratio. The experiment has provided validation not only to the preliminary design of HTBB, but also to calculation code and nuclear data used in the simulations. Various neutron responses such as fission reaction rate, plutonium production rate, activation reaction rate and tritium production rate (TPR) have been measured. Numerical analyses were carried out with MCNP-4C code using ENDF/B-VII.1, TENDL-2017, IRDFF-v1.05 and FENDL3.1 nuclear data libraries. The comparisons between the calculation and experimental results show an agreement within about 10% for most of the measured quantities. The ratios of calculated to measured results (C/E) of tritium production rate are in 0.98-1.04 range which shows good agreement. (C) 2021 Elsevier Ltd. All rights reserved.

At present, in the research on virtual and real loops of control and protection systems, scholars at home and abroad are mainly focusing on the field of AC digital substations, and there is less research on the virtual and real loops of UHV DC control and protection systems. Aiming at this problem, this paper proposes an automatic construction and correlation method for virtual and real loops of UHV DC control and protection system. This method automatically constructs the real circuit by analyzing the design drawings and the optical cable inventory, analyzing the DC visualization program to automatically construct the virtual circuit, and then automatically correlates the virtual and real circuits based on the graph depth traversal algorithm. The practical application in UHV DC engineering shows that this method can help relevant personnel complete the automatic construction and correlation of virtual and real loops, and improve the convenience of operation and maintenance of the UHV DC control and protection system.

The power converter based co-phase traction power system has the advantages of canceling neural sections and providing high power quality for both the external grid and the traction system. Electromagnetic transient simulation is a powerful tool for the transient phenomena study, control and protection system design and testing of the co-phase system. However, the number of the converters and its relatively complex converter topology both impose the challenge for the simulation speed, which affects the productivity for the co-phase system study. This work proposes an accelerated model on PSCAD/EMTDC for the static power converter (SPC) based on cascaded AC/DC/AC sub-modules (SMs), which is applied in Beijing Daxing Airport Express co-phase project. The accelerated model can obtain 19.8 times speedup with the accurate and detailed simulation results compared with the complete model using discrete switches in the co-phase system containing 4 SPCs with 16 SMs in each of them.

模块化多电平换流器(MMC)具有低谐波、低开关损耗、模块化等优点,已在国内外多个柔性直流输电工程中投入运行.数字实时仿真可对MMC控制与保护装置进行硬件在环测试,对保障交直流系统安全稳定运行具有重要意义.因具有高度并行计算能力,现场可编程逻辑门阵列(FP-GA)常在实时仿真器中用于MMC模型计算.随着交直流仿真系统中MMC数量的增加,FPGA逻辑计算资源的消耗也成倍增长.在单个仿真计算步长内,元件模型计算与系统电路矩阵计算为顺序执行关系,因此MMC计算单元在周期性运算中存在闲置时间.文章提出了基于桥臂等效电路模型与桥臂平均值模型的动态组合实时仿真模型,FPGA中的MMC计算单元可以在元件模型计算与矩阵求解阶段中复用,实现MMC逻辑资源的优化利用,大幅降低仿真硬件成本.文章在PSCAD/EMTDC离线仿真环境验证了算法的准确性,并在包含FPGA的多核片上系统中实现了三端柔性直流输电系统实时仿真.

受端电网扰动/故障后的暂态电压稳定问题已成为交直流馈入大中心负荷区电网安全稳定的主要威胁.无功电源和无功负荷的动态失衡是导致暂态电压稳定的根本原因.针对该问题,考虑对直流受端电网进行动态无功优化配置,以提升直流受端电网的动态支撑能力.本文对交直流混合系统的无功补偿布点和补偿容量优化方案做了详细研究,将交直流输电系统分为直流和交流两部分进行无功布点的筛选,此过程中主要考虑了交流系统的负载率、暂态电压恢复时间、直流换流站间的交互作用以及发电机作为无功电源的作用等因素,采用网络收缩模型和性能指标设计无功补偿布点;此外,本文采用遗传算法进行优化问题解算,得到全局优化解;最后,基于IEEE39节点系统改进的交直流系统中进行了上述方案的验证.

A multi-terminal hybrid HVDC transmission system, with LCC station in the rectifier and MMC station in the inverter, integrates the advantages of LCC and MMC technology, and it overcomes the commutation failure problem in the inverter. The application includes power supply to weak AC system, passive load, islands and so on. It shows widely application prospect in the field of large capacity, high voltage and long distance HVDC transmission in the future. In this paper, firstly, the mathematical model for a multi-terminal hybrid HVDC transmission system is studied deeply, and its real time simulation system is established in RTDS. Then, a DC voltage margin control strategy for LCC in rectifier, and a transient AC voltage regulation strategy for MMC in inverter is put forward for dealing the AC system fault. The simulation results in RTDS show the control strategy is effective, and the DC voltage and transmission power recovery quickly after AC system series fault. The proposed control strategy is significant for the safety and reliability for the multi-terminal hybrid HVDC.

The measurements of iron, beryllium and carbon sphere neutron leakage spectra using BC501A detector by DT neutron source are presented. The experiments were carried out in Institute of Nuclear Physics and Chemistry (INPC), China. Neutron leakage spectra in a wide energy range at angles of 0° and 30° from the direction of incident deuteron beam were obtained. The results show the leakage neutron flux decreases notably with the spherical shell increasing when neutron energy >10MeV. When neutron energy <6MeV the leakage neutron distribution tends to lower energy side with the shell increase. The total uncertainty evaluation of the neutron spectra is also provided: in the high-energy parts the uncertainty is about 5-7%, while in the low-energy parts the uncertainty is about 7-9%. In order to compare the experiment results a Monte-carlo calculation was made using the MCNP5 Code with the ENDF/B-VII.1 nuclear data files.

In order to extend the use of concealed explosive detecting device in the anti-terrorist area,the safety analysis of explosive,food and drug for the fast neutron irradi-ation was carried out.The Monte Carlo simulation was used to build the evaluated mod-el of fast neutron irradiated on explosive.Combining with the energy deposition and exploded mechanisms,the fast neutron irradiation would not cause the explosive blast. The dose analysis method was used to evaluate the safety of fast neutron irradiated on food and drug.The results show that the fast neutron irradiated on food and drug is safe with the irradiation dose under the standard at home and abroad in the condition of concealed explosive detecting device.

The 238 U (n ,2n) reaction rates of two depleted uranium spheres were meas‐ured .The depleted uranium spheres were irradiated by D‐T neutron at PD‐300 accelera‐tor .The intensity of neutron source was monitored by the associated‐alpha particles from the T (d ,n)He reaction .After radiation ,the activated gamma rays of uranium foils in the 45° hole of uranium spheres were measured using HPGe detector .The 238 U(n ,2n) reaction rates of two depleted uranium spheres were calculated using Monte‐Carlo simu‐lation .It shows that the 238 U(n ,2n) reaction rates from experiments are agreed with the calculations .The change of 238 U(n ,2n) reaction rate with the radius r of depleted urani‐um sphere is obeyed approximately the distribution of e - ar/r2 .

Real-time simulation of modular multilevel converter (MMC)-based HVDC is one of the most important and difficult technologies in the area of utility-scale power electronics research. This paper describes an efficient modeling approach for real-time simulation of MMC-HVDC. Taking advantages of the full parallel architecture of the field-programmable gate array (FPGA), more than 1500 submodules are able to be simulated in a single FPGA. The design details of the physical MMC control system are also presented. The presented MMC-HVDC real-time simulator and physical control system are successfully performed in the Nan-ao Island MMC-HVDC project, which is the world's first three-terminal MMC-HVDC system for research on operation and fault characteristics. The results validate the accuracy of proposed approach and real-time MMC simulator.

In response to the growing terrorist activities, a security check instrument for explosives detection based on associated particles technique (APT)/neutron time of flight(TOF) has been developed. This paper describes the instruments working principle and the development of his process. The instrument can be remotely controlled from any PC-compatible computer. Inside is an APT neutron generator with a 33 matrix of semiconductor detectors of associated alpha-particles, the shielding protection system of neutron and gamma-ray, support platform, arrayed NaI(Tl)-based detectors of gamma-rays, fully-digital data acquisition electronics, data analysis and decision-making software, and transmission device. The common explosives and chemical warfare agents were detected by security check instrument. Results show that the instrument can meet the needs of practical application. The instrument is mainly used to detect explosives in luggage at check routeway, and it can also be trained to detect other hazardous materials, such as chemical/toxic/drug materials, if their chemical composition is in any way different from that of the surrounding materials.

This paper presents the droop control strategies for 4-terminal MMC VSC-HVDC system based on multi point voltage control, which make it possible the automatic coordination among t he converter stations in the VSC-MTDC system independence of the interstation communication. Moreover, the 4-terminal MMC VSC-HVDC system control equipments, upon which the droop control strategies are realized, are designed and implemented. The 4-terminal MMC VSC-HVDC real-time simulation and testing platform, which is mainly the closed-loop connection between the MMC control equipments and RTDS, is also set up in this paper. The simulation and testing results based on the platform prove the validity and accuracy of the droop control strategies for 4-terminal MMC VSC-HVDC system based on multi point voltage control which are presented in this paper.