横联差动及和相电流保护装置无法正常投入原因分析

通过实例计算证明并不是所有并列运行的双回线路都适于装设横联差动及和相电流延时速断保护装置;结合现场实际分析横联差动及和相电流延时速断保护装置在重负荷长线路双回线应用时无法正常投入原因。     

变压器差动保护用电流互感器饱和的原因分析及解决办法

针对沙角A电厂脱硫变压器差动保护用电流互感器在较小的一次电流下发生饱和的现象,从电流波形、互感器的稳态饱和特性、暂态饱和特性等方面进行了分析计算,并根据分析结果,提出了解决办法,取得了预期效果。     

Measurement of leak current generation distribution in PEFC and its application to load fluctuation testing under low humidification

A study was performed to establish a method for measuring the position and amount of leak current increase during operation of a fuel cell. This measurement method was applied to load fluctuation testing at low humidification and the increase in the leak current was observed in the downstream zone of the cell. The tested cell was disassembled and cross sections were observed under the SEM. The SEM images revealed the formation of a Pt band near the cathode catalyst in the downstream zone of the cell. This may be the cause of the degradation of the membrane at the downstream. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 1–9, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21038     

Inverter for interchangeable use as current source inverter and voltage source inverter for interconnecting to grid

We propose a novel inverter that can be operated either as a current source inverter (CSI) or as a voltage source inverter (VSI) by changing only the control signals. It is proper to use it for interconnecting systems with renewable energy, such as photovoltaic cells or wind generation systems, to a grid. This inverter is usually operated as a CSI connected to the grid. Even if the energy source has a lower voltage than the grid, energy can be supplied to the grid through the proposed inverter. The power factor can be brie?y maintained close to unity. When power supply from the grid is interrupted, the proposed circuit should be operated as a VSI in the stand‐alone operation mode. In this way, the circuit can maintain a constant output voltage to the loads. In this paper, the proposed circuit con?guration and the control schemes for both the CSI and the VSI are described. The circuit characteristics for both are also discussed experimentally. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 45–53, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22349     

电网故障下双馈风电机组暂态电流评估及分析

为了便于分析并网双馈风力发电机组低电压穿越(LVRT)运行的承受能力,有必要对电网故障下双馈风电机组的暂态电流进行评估.本文利用双馈发电机定、转子磁链的暂态变化机理,推导并提出了双馈风电机组在机端短路故障和电网电压不同跌落程度时的定、转子暂态电流评估的解析表达式,并通过考虑风力机传动链柔性的机组暂态仿真结果验证了推导表达式的正确性.在此基础上,应用推导的表达式对双馈风电机组在不同初始输出有功功率、无功功率以及电网电压不同跌落程度时的定、转子暂态电流最大值进行了计算,并得到了不同运行工况对机组暂态性能的影响规律.     

Studies of characteristics and design of superconducting fault current limiter with adjustable trigger current level in current limiting operation

Superconducting fault current limiters (SCFCLs) are expected to improve not only reliability but also stability of power systems. To introduce an SCFCL in a power system, various specifications such as trigger current level, impedance in current limiting operation, recovery time, and so on are necessary. Fault analyses point out that accuracy of the trigger current level is necessary. Therefore, an SCFCL of a transformer type with adjustable trigger current level was proposed and manufactured. Using the trial SCFCL, adjustability of the trigger current level was confirmed. It is found that the SCFCL has good limiting and recovery characteristics. In this paper, characteristics of the SCFCL are considered from a design point of view. Most of the specifications necessary for design depend on the characteristics in current limiting operation. Therefore, the characteristics of the SCFCL in current limiting operation are discussed. It is shown that this kind of SCFCL has good property for easy design, and its design principle is summarized. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(3): 30–38, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10054     

接地网电流分布的测量与分析

由于在实际接地网中测量接地网电流是不可能的，因此，提出了一种实验室接地模拟的方法来分析实际接地网的电流分布，即在实验水池中，用电量隔离传感器测量接地网的电流分布，测出不同接地网——单根垂直接地体、十字形接地网、水平接地网、复合接地网的电流分布，所得的实验结果为研究接地网中的电位分布及接地网的设计提供较准确的科学数据。     

变频器对风电系统轴电压和轴电流的影响

在现代风力发电系统作中,由于大量采用了高频电力电子器件,给整个系统带来了轴电流问题,严重影响着系统的安全运行和发电机轴承等机械部件寿命。精确分析发电机内部电容参数对准确预测轴电压和轴电流的重要作用。首先分析了风力发电系统的共模电路,通过研究风力发电机内部结构,确定了电机耦合电容的解析计算公式,同时提出了有限元计算方法。等效分析轴承运行过程中轴承等效电容模型,进而确定了风力发电机系统轴电流形成机理和影响因素。     

可调阻抗无互联线并联逆变器的控制方法

传统的无互联线并联逆变器PQ下垂法是由同步电机并网理论推导而来的,它具有稳态均流精度低和动态响应差等缺点.分析了逆变器并联系统的有功功率和无功功率的环流模型,并且基于传统的PQ下垂法,增加了具有阻抗调节功能的两个控制环节,提高了系统的动态和静态环流抑制能力,并且降低了系统对线阻抗等参数不平衡的敏感程度.仿真和实验结果均验证了该方案的良好性能.     

An analysis of superconducting fault current limiter for stabilization of synchronous generators in multimachine system: A two‐machine infinite bus system

This paper presents the results of analyses of the effectiveness of a superconducting fault current limiter (SFCL) to stabilize the synchronous generators, suppress turbine shaft torque oscillations, and limit the fault current in a two‐machine infinite bus system. In this study, the system model with two SFCLs having shunt resistance installed at each generator terminal was used taking 3LG (three lines to ground) fault at 12 fault points into account. These analyses were performed using EMTP/ATP. It is found that the use of SFCL with a shunt resistance value of 1.1 pu is most effective for all fault points for the stabilization of synchronous generators, the suppression of turbine shaft torque oscillations, and the limitation of fault current. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 44–53, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10272     

10 kV配电网合环电流暂态过程的分析与仿真

分析了配电网合环暂态过程及合环冲击电流对电网安全运行的影响.结合配电网特点建立了数学模型,推导出了合环冲击电流的数学表达式,并应用PSCAD/EMTDC软件对实际算例进行了暂态仿真计算.仿真计算结果表明,建立的数学模型正确可行.     

电流互感器潜伏性故障的原因分析及处理措施

针对哈尔滨电业局近年来电流互感器潜伏性故障频发的问题,阐述了油中溶解气体色谱分析诊断故障的方法,分析了形成电流互感器故障的原因,提出了相应的处理措施.实践证明,利用油中溶解气体色谱分析技术,可以及时准确地诊断出电流互感器的潜伏性故障及其位置,并有利于技术人员对其分析及处理.     

中低压铜芯电缆经济电流密度的更新与分析

在过去几年中,铜价上升的幅度很大,导致铜芯电缆成本成倍增长,经济截面有减小的趋势,因此以前确定的经济截面是否仍满足载流量要求有待验证.对中低压铜芯电缆的材料费等原始数据进行了系统的收集和整理,据此更新了经济电流密度数据,并通过引入电缆类型系数,使得经济电流密度数据得以更加简洁,进而方便查阅.再者,结合实例分析了更新后的经济电流密度的稳定性,考察了更新前后经济电流密度的变化情况,验证了更新后的经济选型数据的经济性和准确性.     

Optimal current control methods of a non‐salient pole hybrid field‐synchronous motor for energy‐efficient and wide speed‐range operation

This paper proposes new practical optimal current control methods for a newly emerging class of non‐salient pole synchronous motors with hybrid rotor fields by both permanent magnet and winding. In practical situations with limited voltage, the extensively used permanent magnet synchronous motor hardly achieves an ideal performance that allows simultaneously both low‐speed high‐torque and wide speed‐range operations, due to its constant magnet field. Hybrid field synchronous motors (HFSM) have recently emerged to achieve ideal performance as practical motors with controllable hybrid rotor field. For HFSM, the same torque can be produced by a variety of currents due to nonlinearity between torque and currents. Consequently, appropriate determination of a set of stator and rotor current commands plays a key role in achieving possible energy‐efficient and wide speed‐range operation. Proposed methods determine the current commands corresponding to a given torque command such that total winding copper loss due to stator and rotor currents can be minimized if the exact solution exists; the best approximate torque can be produced if no exact solution exists. The determined current commands are optimal in the sense of energy efficiency or degree of approximation in wide speed‐range operation under voltage limit. New real‐time recursive algorithms searching the optimal current solution are also given. The proposed methods are analytical but practical, and their usefulness is verified through experiments. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 70–83, 2006; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20156     

一种软起动电源系统及其逆变器的无线并联控制

提出一种应用于轨道机车辅助电源的三相交流电源系统,由位于各车厢的逆变器并联构成。各逆变器独立带本车厢负载变频软起动,达到稳态运行后通过无互联线并联控制实现并联运行。为有效抑制逆变器并联瞬间电流冲击,提出基于空间矢量控制(space vector control,SVC)特性和依据输出功率母线电压相位的热并机准同步控制,结合下垂法均流算法,该控制改善了稳态均流性能和动态过程可靠性。分析并机电感参数对逆变器及其并联系统特性的影响,并给出设计原则。搭建两台逆变器组成的并联系统并进行动态和稳态实验,验证了所提出系统及控制的可行性。     

乌昌地区220kV母线短路电流限制措施的研究

“十二五”期间,新疆被确定为我国重要的能源基地,加快电网建设,提高电力外送水平已成为新疆电力在“十二五”期间工作的重中之重。随着电网的发展和大量机组的接入,乌昌地220kV系统短路容量逐步上升成为影响电网安全稳定运行的主要问题。结合新疆电网2012年冬季最大运行方式,通过PSASP软件的仿真计算．寻找最经济、快速、有效的措施解决乌昌地区220kV母线2012年四季度短路电流过大的问题。     

Numerical analysis of transit conduction current in an insulating liquid with added ionic electrolyte

We simulated the phenomena of transit conduction in an insulating liquid with added ionic molecules such as surfactant, by using the charge‐injection model with dissociation‐recombination. When the parameters of C_i (density of injected charge) and C₀ (density of created charge in the liquid) are C_i>C₀ in this simulation, the waveform of current density showed an injection type with a peak, and when C_i<C₀, it showed a dissociation‐recombination type. A decreasing characteristic appeared in the low electric field, maximum one in the middle field, and saturating one in the high field. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 10– 16, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20327     

A novel approach of reference current generation for power quality improvement in three-phase, three-wire distribution system using DSTATCOM

This paper presents a novel approach based on an improved instantaneous active and reactive current component theory for generating reference currents for distribution static compensator (DSTATCOM). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the DSTATCOM using the proposed control strategy has been evaluated under various source and load conditions. The performance of the proposed control strategy has been evaluated in terms of load balancing, reactive power compensation, compensator rating and harmonic mitigation. A three-phase, three-wire distribution system supplying star connected linear as well as non-linear unbalanced load is considered for simulation study. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategy.     

自耦变压器绕组漏磁场及涡流损耗的二维数值分析

利用ANSYS软件建立了油浸式自耦变压器的有限元模型,采用“场-路耦合”方法分析了变压器绕组的漏磁分布,得到绕组的涡流损耗分布情况.将有限元计算结果与工程计算结果对比,说明了计算方法的准确性,对自耦变压器的设计具有一定的理论参考价值.