敏感设备电压暂降免疫力测试标准与尚需研究的问题

电压暂降给各行业采用的敏感设备造成影响和危害,成为全社会关注的重点,针对设备电压暂降免疫力测试标准和评价准则的研究是现代社会的重要课题之一。该文较全面分析现有国际标准及其涉及的相关问题,并结合已有研究,对现有标准中尚值得完善的问题进行简要分析,为科学解决电力系统、敏感用户和全社会关注的电压暂降问题提供参考。     

三相系统电压暂降的相位跳变检测

针对目前相位跳变检测仍缺乏明确的国际标准,提出检测三相系统电压暂降PAJ的4种不同定义和计算方法;方法 1和2基于三相测量电压检测三相PAJ,方法 3和4基于复电压参数检测特征PAJ。详细研究修正频率和暂态过程对4种检测算法的影响,以暂降严重程度和PAJ偏移程度为依据,提出具有一般意义的三相系统PAJ检测标准。以100组系统实测数据对4种方法进行仿真验证,结果表明所提方法正确有效,PAJ检测标准可行实用。     

煤矿电压暂降成因与治理

随着煤矿行业生产机械化程度越来越高,变频器和大功率直流提升机等含有电力电子器件的设备大量运用于煤矿行业,煤矿电网中非线性和冲击性负载比例逐渐增加,直接导致了煤矿电网的电压质量下降,尤以电压暂降问题突出。文章针对电压暂降对煤矿生产的影响,并结合具体电压暂降事件,经过现场测试,确定发生电压暂降的原因,提出相应的治理措施,为煤矿行业该类事件的治理提供借鉴和参考。     

电压暂降抗扰度能力验证结果的不确定度评定

能力验证是评价实验室技术能力的重要手段之一,其结果也是判定实验室维持其技术能力的重要凭证.本文以参加电压暂降抗扰度的能力验证为例,介绍了电压暂降抗扰度能力验证的测量方法,分析了其结果测量不确定的来源,阐述了如何建立测量模型,并对各个分量进行分析和计算,求出了扩展不确定度,为实验室提供指导参考.     

基于隐马尔可夫模型的电压暂降发生时间预测

通过电能质量监测系统(power quality monitoring system, PQMS)中蕴含的电网历史故障变化、趋势等重要信息,对未来电压暂降进行预测,可为用户和电网公司合理规划生产,避免经济损失提供有力帮助。该文提出一种基于隐马尔可夫模型的电压暂降发生时间(occurrence time of voltage sag, OTVS)预测方法。首先对电压暂降发生时间的变量可预测性、数据冗余性、事件混沌性进行分析,揭示电压暂降监测数据特性;然后针对这三种特性,提出基于模糊C-均值聚类算法(fuzzy C-means algorithm, FCMA)和赤池信息准则(Akaike information criterion, AIC)的电压暂降历史状态识别与划分方法,以区间型变量刻画监测数据中的历史变化信息;建立考虑暂降历史变化信息和电网扰动变化信息的隐马尔可夫模型,实现对未来电压暂降的预测。最后,利用中部某省10个监测点的历史数据进行验证,所提方法的预测准确率最高可达92.85%,所提方法的预测性能较其他典型预测方法约高5%～30%。     

基于Matlab/Simulink的电压暂降仿真与分析

介绍了检测电压暂降的有效值算法和傅里叶变换(FFT)算法,在Matlab环境下,针对四种冲击性负荷引起的电压变化进行仿真,并将有效值算法和傅里叶变换(FFT)算法相结合,检测了电压暂降的幅值、持续时间和相位跳变,验证了这两种算法的有效性。仿真结果表明,在正常负荷相同的条件下,冲击性负荷的有功功率对于电压暂降的幅度和相位跳变均有明显的影响;而冲击性负荷的无功功率则主要影响电压暂降的幅度,对于相位跳变的影响很小。     

基于电压畸变观测的PMSM逆变器故障检测方法

针对永磁同步电机(PMSM)驱动系统中脉宽调制(PWM)电压源型逆变器(VSI)容易发生开路故障的问题,提出一种简单且低成本的开路故障检测方法。首先,对PWM逆变器中功率开关发生开路故障时引起的对应端电压变化进行分析,构建开路故障与各相电压波形畸变的关系模型。然后,通过观测各相的电压畸变,并与阈值进行比较来构建各相的布尔错误模型。最后,基于布尔错误模型和错误检测时间来检测故障状态并识别故障开关。同时对检测时间进行分析,避免故障误报。实验结果表明:该方法能够快速且有效地进行故障诊断,具有良好的可行性和实用价值。     

芮城县100MW农光互补光伏逆变器选型与安装技术

本文以芮城县100MW农光互补光伏项目为例,对该项目逆变器的方案设计和选型进行了详细分析,并根据选型结果有针对性地提出逆变器的安装流程和注意事项,可为同类型光伏发电项目逆变器的安装和调试提供借鉴。     

基于Hausdorff距离与OPTICS聚类的电压暂降同源识别方法

为合理评估、治理电压暂降问题,电网公司大量安装电能质量监测终端,实现电压暂降监测和感知,但同时造成暂降事件被不同监测终端重复记录的数据冗余问题.为此,该文提出基于Hausdorff距离的电压暂降波形相似度计算方法.将波形相似度和持续时间作为同源识别特征,构建电压暂降同源识别特征矩阵;提出基于多维尺度分析(multi-d...     

三电平逆变器共模电压分析与抑制

为抑制三电平逆变器共模电压,以二极管钳位式拓扑为例,分析其共模电压产生机理并提出一种抑制共模电压的简化三电平5段式空间矢量脉宽调制算法。该算法通过选取输出共模电压幅值小的基本电压矢量参与调制来抑制共模电压。仿真和实验结果表明,所提算法将共模电压最大幅值抑制到Vdc/6,比传统一般算法、抑制共模电压的7段式、7段式算法分别减少2/3,1/2,0,且可以克服上述3种算法输出共模电压幅值随其调制度变化而变化的缺点。     

Design and analysis of dynamic voltage restorer for deep voltage sag and harmonic compensation

A dynamic voltage restorer (DVR) to compensate deep voltage sags and harmonics is proposed. The DVR consists of shunt and series converters connected back-to-back through a DC-to-DC step up converter. The presence of the DC-to-DC step converter permits the DVR to compensate deep voltage sags for long duration. The series converter is connected to the supply side whereas the shunt converter is connected to the load side. With this configuration, there is no need for large DC capacitors. A design procedure for the components of the DVR is presented under a voltage sag condition. The control system of the proposed DVR is based on hysteresis voltage control. Besides voltage sag compensation, the capability of compensating load voltage harmonics has been added to the DVR to increase the power quality benefits to the load with almost negligible effect on the sag compensation capability. The proposed DVR is modelled and simulated using SIMULINK/MATLAB environment. Time domain simulations are used to verify the operation of the DVR with linear and non-linear loads.     

A grid-tie PV inverter with the ability to improve power quality under unbalanced and distorted source voltage conditions

ABSTRACT

This paper proposes a grid-tie PV inverter that is able to improve power quality under conditions of both distorted and unbalanced source voltage. The presented strategy is based on the instantaneous power theory and uses a second-order generalized integrator-quadrature signal generator (SOGI-QSG). The presented control strategy is aimed at compensating reactive power, eliminating current harmonics, load balancing, and enabling the PV to inject maximum power to the grid. The advantages of the control system are the use of SOGI-QSG adaptive filter and frequency-locked loop (FLL), and removing the low-pass filter and phase-locked loop (PLL). DC–DC and DC–AC converters are utilized for connecting the PV to the grid. The DC–DC and DC–AC converters are responsible for maximum PV power tracking and achieving the control aims, respectively. Using 4-leg converter structure for grid-tie inverter enables achieving the control objectives in 3-phase 4-wire distribution network without any transformer. The presented control strategy is applied to a 3-phase 4-wire distribution network and is simulated in MATLAB/SIMULINK environment. The results of this simulation are then compared with the conventional instantaneous power method in areas including load balancing, reactive power compensation and the elimination of current harmonics, under unbalanced and distorted source voltage conditions.     

影响电压暂降问题的多源属性排序方法

对电压暂降的多源属性进行分析,不仅能为供电工程的规划设计、设备选型、运行维护等环节提供全过程技术支撑,还可以有效评估电能质量事件的风险及其严重程度。该文提出电压暂降的多源属性贡献度排序方法。首先,列举电压暂降的多源属性,将其分为内源属性和外源属性;然后,采用设备兼容度指标,计算多源属性下设备的暂降兼容度,并建立基于层次分析法的三层致因体系,针对多源致因属性的权重进行计算;最后,利用蒙特卡洛法进行仿真,结合实际工程数据,分析多源致因属性下发生电压暂降的严重性程度,评估结果验证该方法可行。     

PWM optimisation for three-level voltage inverter based on clonal selection algorithm

A clonal selection algorithm (CSA) is first applied to determine the switching time for a three-level voltage pulse width modulation (PWM) inverter. To obtain an optimal PWM switching pattern, CSA should calculate a set of nonlinear transcendental equations with nonlinear equality and inequality constraints. Unlike the general CSA by penalising infeasible solutions, this new CSA deals with constraints and guides the search to the true optimum solution by an infeasibility degree with a random disturbance (IFDD) selection operation. The proposed method minimise the total harmonic distortion and generates a waveform with adjustable amplitude of the fundamental component. Calculation results verify that the proposed method is efficient to obtain the optimal PWM switching pattern and is superior to natural sampling and genetic algorithm-based PWM switching pattern.     

对家用电器耐压试验的两点要求

电器在正常使用中绝缘结构既要承受电网额定电压的长期作用,又要经受电路中经常产生的各种过电压和短时冲击电压为了验证电器能在实际电路中长期使用而不致发生绝缘被击穿或出现闪络等事故,以避免危及人身安全,验证方法通常采用冲击耐压试验和工频耐压试验.而目前家用电器安全标准GB4706.1-1998<家用和类似用用途电器的安全第一部分:通用要求>没有冲击耐压试验,只有工频耐压试验(以下简称耐压试验),而且把耐压试验作为家用电器安全检测中最基本的试验之一,所有家用电器产品都有这个试验项目.因此结合本人工作实践,对家用电器耐压试验的设备要求和标准要求提出两点看法.     

NPC型三电平逆变器SVPWM控制方法及中点电位平衡研究

二极管箝位型(NPC)三电平逆变器在中、高压大容量功率变换装置中的需求越来越迫切,目前已成为研究的热点.讨论利用功率开关所生成的不同电压矢量优化合成旋转参考空间电压矢量及各矢量作用时间分配的方案,实现SVPWM控制策略驱动逆变器;讨论实时改变控制负小矢量作用时间的系数以平衡直流侧母线中点电位的问题.仿真结果验证了NPC三电平逆变器SVPWM控制策略的正确性及中点电位平衡控制的有效性.     

Fast sag/swell detection method for fuzzy logic controlled dynamic voltage restorer

In this study, the design and analysis of a fuzzy logic (FL) controlled dynamic voltage restorer (DVR) are presented and extended to perform fast fault detection. A new control method for DVR is proposed by combining FL with a carrier modulated PWM inverter. The proposed control scheme is simple to design and has excellent voltage compensation capabilities. The proposed method for voltage sag/swell detection has the ability of detecting different kinds of power disturbances faster than conventional detection methods. Effectiveness of the proposed detection method is shown by comparison with the conventional methods in the literature. Simulation results under unbalanced supply voltage are presented to evaluate the performance of the designed DVR.