Calculation of Eddy Current Loss and Short-circuit Force in SSZ11-50000/110 Power Transformer

The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination of the product and TEAM Problem 21B, the surface impedance method shows its great advantage in the calculation of eddy current loss.

基于临界超标样本扩充的数据驱动短路电流超标精准校验方法

短路电流超标校验中,针对现有技术在临界超标场景下存在计算精度不足、易误判的缺陷,提出一种基于临界超标样本扩充的数据驱动短路电流超标精准校验方法。首先,在短路电流领域首次采用生成对抗网络(generative adversarial networks,GAN)产生与蒙特卡洛模拟具有相同效力的大量样本,再筛选其中的临界超标样本;其次,设计了一种临界超标占比高、非临界超标占比低的新型样本构成方式,据此融合GAN生成临界超标样本与蒙特卡洛仿真样本以形成数据驱动样本集;继而,采用数据驱动的代表性回归算法LightGBM开展短路电流超标校验;最后,仿真结果表明所提方法能有效提高短路电流超标的校验准确度,相比其他物理计算方法和数据驱动方法具有更高效率和计算精度,以及更快的计算速度。

Characteristics of Bi-2223 HTS Tapes Under Short-Circuit Current Impacts in Hybrid Energy Transmission Pipelines

A hybrid energy transmission pipeline is proposed with the aim of long-distance cooperative transmission of electricity and chemical fuels, which is composed of an inner high-temperature superconducting (HTS) power cable and outer liquefied natural gas (LNG) pipeline. The flowing LNG could maintain the operating temperature of the inner HTS power cable within the range of 85 K-90 K, thus the Bi-2223 superconductors in the HTS power cable produce little Joule loss with the transmission current below the critical current. Owing to the advantages of high power density, low transmission losses and economical manufacturing costs, the hybrid energy transmission pipeline is expected to be widely utilized in the near future. In order to ensure the safety of the HTS power cable and explosive LNG in case of short-circuit faults, this paper tests and analyzes the characteristics of Bi-2223 HTS tapes of the Type HT-CA, Type HT-SS and Type H models under short-circuit current impacts at the LNG cooling temperature (85 K-90 K). An experimental platform is designed and established for the ampacity tests of HTS tapes above LN2 cooling temperature (77 K). The AC over-current impact tests at 85 K-90 K are carried out on each sample of Bi-2223 tapes respectively, and the experimental results are analyzed and compared to evaluate their performances under different operating conditions. The results indicate that the Type HT-CA tape can withstand 50 Hz short-circuit current impact with the amplitude of 1108 A (10 times of critical current Ic ) for 100 ms at 90 K, and its resistance is the smallest of the three tested samples under similar current impacts. Therefore, the Type HT-CA Bi-2223 tape is the optimal superconductor of the HTS power cable in the hybrid energy transmission pipeline.

Placement optimization of Multi-Type fault current limiters based on genetic algorithm

The fault current limiter(FCL)is an effective measure for improving system stability and suppressing short-circuit fault current.Because of space and economic costs,the optimum placement of FCLs is vital in industrial applications.In this study,two objectives with the same dimensional measurement unit,namely,the total capital investment cost of FCLs and circuit breaker loss related to short-circuit currents,are considered.The circuit breaker loss model is developed based on the attenuation rule of the circuit breaker service life.The circuit breaker loss is used to quantify the current-limiting effect to avoid the problem of weight selection in a multi-objective problem.The IEEE 10-generator 39-bus system in New England is used to evaluate the performance of the proposed genetic algorithm(GA)method.Comparative and sensitivity analyses are performed.The results of the optimized plan are validated through simulations,indicating the significant potential of the GA for such optimization.

Research on Numerical Simulation of 3D Leakage Magnetic Field and Short-circuit Impedance of Axial Dual-low-voltage Split-winding Transformer

It is difficult to accurately calculate the short-circuit impedance, due to the complexity of axial dual-low-voltage split-winding transformer winding structure. In this paper, firstly, the leakage magnetic field and short-circuit impedance model of axial dual-low-voltage split-winding transformer is established, and then the 2D and 3D leakage magnetic field are analyzed. Secondly, the short-circuit impedance and split parallel branch current distribution in different working conditions are calculated, which is based on field-circuit coupled method. At last, effectiveness and feasibility of the proposed model is verified by comparison between experiment, analysis and simulation. The results showed that the 3D analysis method is a better approach to calculate the short-circuit impedance, since its analytical value is more closer to the experimental value compared with the 2D analysis results, the finite element method calculation error is less than 2%, while the leakage flux method maximum error is 7.2%.

数据—物理融合驱动的含新能源电网短路电流超标评估策略

目前含新能源电网短路电流超标问题日益严重,因其状态变化更快、幅度更大,离线的短路电流超标分析可能无法穷尽超标场景,在线实时分析具有相当的必要性。考虑到主流物理模型计算方法难以满足在线计算速度需求,更快速的计算具有重大意义,因此,提出一种数据—物理融合驱动的短路电流超标评估策略。首先,在分析影响短路电流主要因素的基础上,为了提高计算速度,将原先特征降维为仅考虑负荷的影响,再结合最优潮流及随机模拟生成大量样本集合,通过机器学习算法训练得出数据驱动模型,在此基础上,使用漏检率和误检率对数据模型进行阈值整定;然后,利用数据驱动模型初步筛选短路电流超标场景;最后,通过最新研究中所提理论物理模型对初筛后的短路电流场景进行高精度校验,并在含光伏电源的IEEE 39节点模型上进行验证。仿真结果表明:该策略可在确保不遗漏超标短路电流场景的前提下有效提升校验速度。

500kV电网短路电流超标机理及限制措施适应性

提出一种利用短路点自阻抗分析500kV电网短路电流超标机理的方法,并应用于短路电流限制措施的适应性研究。基于二端口网络理论,构建双端电源等值电路,从短路点自阻抗各组成要素的物理意义角度分析不同位置、不同类型短路电流的主要影响因素,揭示其超标机理。500kV侧短路电流主要取决于500kV侧电网结构,因此其限制措施主要是改变500kV侧电网参数;220kV侧短路电流受变压器等值阻抗和220kV电网结构的影响,但不同站点受二者影响程度不同,应根据不同影响程度采取相应的措施以增大变压器等值阻抗或改变220kV侧电网参数。应用于广东500kV电网短路电流分析和限制措施的研究结果证明了其正确性和实用性。

多种保护电路的低压差线性稳压器设计及仿真

针对电路系统中对低压差线性稳压器高稳定性要求,以及在使用过程中过热及输出电流过大而使电路遭到破坏.提出了一款具有过温保护、短路及限流保护功能的LDO,采用电压与温度成正比的器件感知电路中的温度,将正温度系数电压与恒定电压相比较作为控制信号,利用将输出电流镜像到某个电阻上,其电压与一个恒定电压相比较,调节流过功率管的电流,以达到限流保护.结果表明:过温保护电路的迟滞温度为30℃;过流保护电路在负载电流达到812mA时开启保护;短路保护电路当输出电压小于0.7V时开启保护.在0.1μF电容负载上进行了仿真验证.

Numerical study on short-circuit current of single layer organic solar cells with Schottkey contacts

The influence of the cathode work function,carriers mobilities and temperature on the short-circuit current of single layer organic solar cells with Schottkey contacts was numerically studied,and the quantitative dependences of the short-circuit current on these quantities were obtained.The results provide the theoretical foundation for experimental study of single layer organic solar cells with Schottkey contacts.

Regulating effect of Tong Xie-Yao Fang on colonic epithelial secretion via Cl- and HCO3- channel

AIM To investigate the pharmacological effect of Tong XieYao Fang(TXYF) formula, a Chinese herbal formula, on Diarrhea-predominant irritable bowel syndrome(D-IBS) rats.METHODS In a neonatal maternal separation plus restraint stress(NMS + RS) model of D-IBS, male Sprague Dawley rats were randomly divided into two groups(NMS + RS group and TXYF-formula group) with no handlings were used as controls(NH group). Starting from postnatalday 60, rats in TXYF-formula group were administered TXYF-formula(4.92 g/100 g bodyweight) orally twice a day for 14 consecutive days while NH group and NMS + RS group were given distilled water. Using short-circuit current technology, we observed 5-HT-induced changes of current across ion channels, such as cystic fibrosis transmembrane conductance regulator(CFTR) Clchannel, epithelial Na+ channel(ENaC), Ca2+-dependent Cl- channel(CACC), Na+-K+-2Cl- co-transporter(NKCC), and Na+-HCO-3 co-transporter(NBC), in the colonic epithelium of three groups after exposure to drugs and specific blockers with a Power Lab System(AD Instruments International).RESULTS Under basal conditions, the changes of short-circuit current(?Isc, μA/cm2) induced by 5-HT were similar in NH group and TXYF-formula group, and both higher than NMS + RS group(70.86 μA/cm2 ± 12.32 μA/cm2, 67.67 μA/cm2 ± 11.68 μA/cm2 vs 38.8 μA/cm2 ± 7.25 μA/cm2, P < 0.01, respectively). When CACC was blocked by 4,4′-diisothiocyanato-stilbene-2,2′-disulfonic acid, 5-HT-induced ?Isc was smaller in NMS + RS group than in NH group and TXYF-formula group, respectively(48.41 μA/cm2 ± 13.15 μA/cm2 vs 74.62 μA/cm2 ± 10.73 μA/cm2, 69.22 μA/cm2 ± 11.7 μA/cm2, P < 0.05, respectively). The similar result could be obtained when ENaC was blocked by Amiloride(44.69 μA/cm2 ± 12.58 μA/cm2 vs 62.05 μA/cm2 ± 11.26 μA/cm2, 62.11 μA/cm2 ± 12.01 μA/cm2, P < 0.05, respectively). However, when CFTR Cl- channel was blocked by 1,1-dimethyl piperidinium chloride(DPC), 5-HT-induced ?Isc did not significantly differ in three groups(42.28 μA/cm2 ± 10.61 μA/cm2 vs 51.48 μA/cm2 ± 6.56 μA/cm2 vs 47.75 μA/cm2 ± 7.99 μA/cm2, P > 0.05, respectively). The similar results could also be obtained in three groups when NBC and NKCC were respectively blocked by their blockers.CONCLUSION TXYF-formula can regulate the Cl- and HCO-3 secretion of colonic mucosa via CFTR Cl- channel, Cl-/HCO-3 exchanger, NBC and NKCC co-transporters.

Simulation and experimental study of a novel bifacial structure of silicon heterojunction solar cell for high efficiency and low cost

A novel structure of Ag gridlSiNx/n＋-c-Si/n-c-Si/i-a-Si：H/p＋-a-Si：HlTCO/Ag grid was designed to increase the ef- ficiency of bifacial amorphous/crystalline silicon-based solar cells and reduce the rear material consumption and production cost. The simulation results show that the new structure obtains higher efficiency compared with the typical bifa- cial amorphous/crystalline silicon-based solar cell because of an increase in the short-circuit current （Jsc）, while retaining the advantages of a high open-circuit voltage, low temperature coefficient, and good weak-light performance. Moreover, real cells composed of the novel structure with dimensions of 75 mm×75 mm were fabricated by a special fabrication recipe based on industrial processes. Without parameter optimization, the cell efficiency reached 21.1% with the Jsc of 41.7 mA/cm^2. In addition, the novel structure attained 28.55% potential conversion efficiency under an illumination of AM 1.5 G, 100 mW/cm^2. We conclude that the configuration of the Ag grid/SiNx/n＋-c-Si/n-c-Si/i-a-Si：H/p＋-a-Si：H/TCO/Ag grid is a promising structure for high efficiency and low cost.

Application of thyristor controlled phase shifting transformer excitation impedance switching control to suppress short-circuit fault current level

Short-circuit fault current suppression is a very important issue in modern large-interconnected power networks. Conventional short-circuit current limiters, such as superconducting fault current limiters, have to increase additional equipment investments. Fast power electronics controlled flexible AC transmission system(FACTS)devices have opened a new way for suppressing the fault current levels, while maintaining their normal functionalities for steady-state and transient power system operation and control. Thyristor controlled phase shifting transformer(TCPST) is a beneficial FACTS device in modern power systems, which is capable of regulating regional powerflow. The mathematical model for TCPST under different operation modes is firstly investigated in this study. Intuitively, the phase shifting angle control can adjust the equivalent impedance of TCPST, but the effect has been demonstrated to be weak. Therefore, a novel transformer excitation impedance switching(EIS) control method, is proposed for fault current suppressing, according to the impedance characteristics of TCPST. Simulation results on IEEE 14-bus system have shown considerable current limiting characteristic of the EIS control under various fault types. Also, analysis of the timing requirement during fault interruption, overvoltage phenomenon, and ancillary mechanical support issues during EIS control is discussed,so as to implement the proposed EIS control properly for fast fault current suppression.

基于改进REI等值法的网架调整限流策略

为了提高传统全网遍历限流方案的求解效率,面对大规模电力系统,给出一种基于改进REI等值法的网架调整限流策略。将网络等值技术与500 k V网架调整限流机理相结合,根据支路限流灵敏度指标对原系统进行一次预处理,将其划分为研究系统和若干外部子系统。再利用改进的动态REI等值法对各子系统进行化简,以等值过程中各发电机在虚拟支路上的功率传输因子来确定等值发电机的参数。通过在两个算例上的仿真验证,结果表明改进后的REI等值法能够较好地保留原系统的动态特性,同时迅速筛选出最优限流开断线路方案。

10kV零损耗深度限流装置技术研究

针对变电站10 kV母线短路电流超标问题,分析对比了不同短路电流的超标治理方法存在系统压降、电能损耗大、限流深度与可靠性不足的问题,研究了一种10 kV零损耗深度限流装置。该装置采用了基于涡流驱动的快速真空断路器技术、“零前分闸”相控技术、深度限流电抗器等关键技术。系统正常时,装置运行于“零损耗、零压降”状态;系统发生需限流的10 kV短路故障时,装置在20 ms内断开快速真空断路器并投入限流电抗器深度限制短路电流,有效地解决了以往限流设备存在的上述不足。该装置成功安装应用于220 kV同益变电站,将该站超标的10 kV母线短路电流限制在合格范围内,保障了10 kV设备安全运行。

Research on Influence of Motor Parameters on the Negative-Salient Permanent Magnet Synchronous Motor

The d-axis inductance(Ld)of the negative-salient permanent magnet synchronous motor(NSPMSM)is larger than the q-axis inductance(Lq).Compared with the traditional motor,the NSPMSM has the characteristics of a high overload capacity,wide speed range,and preventing permanent magnet demagnetization.Positive d-axis current(id)is applied to control positive reluctance torque when running at base speed.When the motor is running at high speed,a relatively small id can achieve speed expansion and effectively expand the motor flux-weakening range.The use of a magnetic bridge to increase the Ld and a W-type permanent magnet to reduce the Lq is proposed in this article as a novel NSPMSM rotor structure.Firstly,the working principle of the NSPMSM was determined according to the equivalent magnetic circuit.Secondly,using the finite element method,the influence of motor structure on torque and speed performance of NSPMSM was analyzed,and the motor structure was optimized.Thirdly,the effect of the internal power factor angle on the performance of the two motors is analyzed.Finally,the short circuit simulation and analysis verified that the NSPMSM has a stronger short circuit current suppression ability without sacrificing overload ability.

Influence of band gap of p-type hydrogenated nanocrystalline silicon layer on the short-circuit current density in thin-film silicon solar cells

The impact of the optical band gap（Eg） of a p-type hydrogenated nanocrystalline silicon layer on the short-circuit current density（Jsc） of a thin-film silicon solar cell is assessed. We have found that the Jsc reaches maximum when the Eg reaches optimum. The reason for the Jsc on Eg needs to be clarified. Our results exhibit that maximum Jsc is the balance between dark current and photocurrent. We show here that this dark current results from the density of defects in the p-layer and the barrier at the interface between p-and i-layers. An optimum cell can be designed by optimizing the p-layer via reducing the density of defects in the p-layer and the barrier at the p/i interface. Finally, a 6.6% increase in Jsc was obtained at optimum Eg for n-i-p solar cells.

110kV GIS型零损耗深度限流装置设计与实现

针对以往电力系统限流设施占地面积大、限流深度不足、存在电能损耗和压降的问题,提出并研制了一种适用于110 kV及以下电压等级的110 kV GIS型零损耗深度限流装置。该装置采用一体化设计的气体绝缘金属封闭开关设备(gas insulated metal-enclosed switchgear,GIS)结构技术,实现了体积小型化封装,有效解决占地面积大的问题;采用基于电磁斥力驱动的快速真空断路器并联限流电抗器技术,在电力系统正常运行时投入快速真空断路器,实现“零损耗、零压降”,解决电能损耗与压降的问题;采用“零前分闸”相控技术,在电力系统故障时快速切除真空断路器,由限流电抗器进行深度限流,有效解决深度限流不足的问题。

Organic Film Photovoltaic Cells with Gadolinium Complex as an Electron Acceptor

A series of organic photovoltaic (PV) cells in which the electron acceptor and donor are gadolinium (dibenzoylmethanato)_3(bathophenanthroline) [Gd(DBM)_3bath] and N,N′-diphenyl-N,N′bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine [TPD], respectively, were fabricated. Although TPD acts as an active layer in the bilayered cells, insertion of a Gd-complex film between TPD and the alloy cathode is necessary for efficient carrier photogeneration. Open-circuit voltage of 3.2 V was obtained due to efficient exciton dissociation near the interface between Gd(DBM)_3bath and TPD. By incorporating an ultrathin mixed layer of Gd-complex and TPD, external quantum efficiency is improved significantly. Photovoltaic performance of the devices has a common origin, exciplex formation, which results in broadband emission during both photoluminescent and the electroluminescent processes.

Simulation of a-Si:H/c-Si heterojunction solar cells: From planar junction to local junction

In order to obtain higher conversion efficiency and to reduce production cost for hydrogenated amorphous silicon/crystalline silicon(a-Si:H/c-Si) based heterojunction solar cells, an a-Si:H/c-Si heterojunction with localized p–n structure(HACL) is designed. A numerical simulation is performed with the ATLAS program. The effect of the a-Si:H layer on the performance of the HIT(heterojunction with intrinsic thin film) solar cell is investigated. The performance improvement mechanism for the HACL cell is explored. The potential performance of the HACL solar cell is compared with those of the HIT and HACD(heterojunction of amorphous silicon and crystalline silicon with diffused junction) solar cells.The simulated results indicate that the a-Si:H layer can bring about much absorption loss. The conversion efficiency and the short-circuit current density of the HACL cell can reach 28.18% and 43.06 m A/cm^2, respectively, and are higher than those of the HIT and HACD solar cells. The great improvement are attributed to(1) decrease of optical absorption loss of a-Si:H and(2) decrease of photocarrier recombination for the HACL cell. The double-side local junction is very suitable for the bifacial solar cells. For an HACL cell with n-type or p-type c-Si base, all n-type or p-type c-Si passivating layers are feasible for convenience of the double-side diffusion process. Moreover, the HACL structure can reduce the consumption of rare materials since the transparent conductive oxide(TCO) can be free in this structure. It is concluded that the HACL solar cell is a promising structure for high efficiency and low cost.

Significant performance enhancement of all-inorganic CsPbBr_(3)perovskite solar cells enabled by Nb-doped SnO_(2)as effective electron transport layer

All-inorganic CsPbBr_(3)-based perovskite solar cells(PSCs)have attracted great attention because of their high chemical and thermal stabilities in ambient air.However,the short-circuit current density(J_(sc))of CsPbBr_(3)-based PSCs is inadequate under solar illumination because of the wide bandgap,inefficient charge extraction and recombination loss,leading to lower power-conversion efficiencies(PCEs).It is envisaged that in addition to narrowing the bandgap by alloying,J_(sc)of the PSCs could be enhanced by effective improvement of electron transportation,suppression of charge recombination at the interface between the perovskite and electron transporting layer(ETL),and tuning of the space charge field in the device.In this work,Nb-doped SnO_(2)films as ETLs in the CsPbBr_(3)-based PSCs have been deposited at room temperature by high target utilization sputtering(Hi TUS).Through optimizing the Nb doping level alone,the J_(sc)was increased by nearly 19%,from 7.51 to 8.92 mA·cm^(-2)and the PCE was enhanced by 27%from 6.73%to 8.54%.The overall benefit by replacing the spin-coated SnO_(2)with sputtered SnO_(2)with Nb doping was up to 39%increase in J_(sc)and 62%increase in PCE.Moreover,the PCE of the optimized device showed negligible degradation over exposure to ambient environment(T~25°C,RH~45%),with 95.4%of the original PCE being maintained after storing the device for 1200 h.