The performance of demand meters under varying load conditions

The influence of load variations on the performance of four different types of electricity demand meters was studied using a computer controlled test system capable of reproducing load profile data recorded in the field. Results of the tested meters are compared with computer calculated demand values based on readings of a fast response reference multimeter. Differences in readings in the range of -9.3% to +5.3% were observed during the tests of the four demand meters. For the load profiles considered, demand calculations based on one minute subintervals resulted in values closer to the true peak demand than calculations with five minute subintervals     

非正弦波及不对称下三相功率因数的定义

尽管三相不对称下功率因数定义已有多种公式,但在非正弦波形又不对称下的功率因数定义依然存有争议。本文从单相非正弦波形下无功功率的时域分析定义出发,导出三相不对称时视在功率的公式,从而获得非正弦波形又不对称下三相功率因数的计算公式。     

多路三相电能表远程微机检测系统的开发

目前，国内外电能表现场实负荷检测，仍沿用传统方法，展望测试系统与计算机通信网结合的发展方向，本文提出了研制开发远程电能表微机检测系统，利用现有电力系统电话网，实现足不出户即可远程检测电能表。     

A novel approach to the design of a shunt active filter for anunbalanced three-phase four-wire system under nonsinusoidal conditions

A new approach is presented for the design of a shunt active filter in a three-phase, four-wire distribution system with unbalanced, distorted sources and unbalanced loads. The purpose of the shunt active filter is to provide compensation currents such that the source needs to supply balanced (positive-sequence) fundamental source current at unity power factor even though the load consumes harmonic currents as well as positive, negative, and zero-sequence currents. A major feature of the proposed approach is that it does not require symmetrical component transformation to transform the three-phase voltages and currents to α-β-o quantities. This makes practical implementation of the proposed method easier than the symmetrical component transformation approach. In addition, the power factor of the positive-sequence fundamental component is close to unity and only positive-sequence power is supplied by the source. The effectiveness of the proposed control algorithm is demonstrated by computer simulation and experimental results of a shunt active filter for a three-phase four-wire distribution system with distorted, unbalanced source voltages and unbalanced loads     

高压电能表校验装置电流档位控制器设计

高压电能表校验装置具有输出高电压、大电流的能力,为了检定与校验不同电流规格的高压电能表,需要输出符合检定规程的电流。目前大部分校验装置需要在停机且断电状态下由操作人员手动改变升流器或电流互感器的档位接线,以输出满足精度要求的电流值。文中提出了一种在装置内部高、低压侧电流档位智能切换的自动控制器,并详细介绍了其工作原理和软硬件设计。该控制器以多个磁保持继电器同步切换为基础,在校验装置不停机的情况下,可以控制连续输出最大允许电流之内的任意值,有效提高了自动校验时的安全性、可靠性和快速性。     

非正弦情况下主要无功功率测量方法的对比研究

针对电力系统无功比重的增加以及人们对无功的关注程度日益提高,本文对几种主要无功功率计算方法进行了系统、全面的对比研究。首先依据无功功率的定义,对基波移相90度、微分法、FFT法和Hilbert滤波器法等无功算法进行对比研究,分析各种算法的基本原理和理论计算精度,比较各种算法的性能优、劣;然后对各种算法的软件实现方法进行研究,并对相关算法进行资源优化使其适用于嵌入式实时平台,进一步提高各算法的性能;最后以基于DSP的高性能三相表为测试平台,对各无功算法进行准确度对比测试。数据分析表明,正弦和非正弦情况下的测试结果与各算法的理论分析结果完全一致。本文的研究成果对各种主要无功算法在优化设计以及电能计量领域的应用具有重要的指导意义。     

A cyclodissipativity characterization of power factor compensation of nonlinear loads under nonsinusoidal conditions

Recently, it has been established that power factor (PF) improvement for nonlinear loads with nonsinusoidal source voltage is equivalent to imposing the property of cyclodissipativity to the source terminals. Using this framework, the classical capacitor and inductor compensators were interpreted in terms of energy equalization. The purpose of this brief note is to extend this approach in three directions. In the result reported in the literature, the supply rate is a function of the load, which is usually unknown, stymieing the applicability of the technique for compensator synthesis. Our first contribution is a new cyclodissipativity condition, which is also equivalent to PF improvement, but whose supply rate is now function of the compensator. Second, we consider general lossless linear compensators, instead of only capacitive or inductive compensators. As a result, we show that the PF is improved if and only if a certain equalization condition between the weighted powers of inductors and capacitors of the load is ensured. Finally, we exhibit the gap between the ideal compensator, namely the one that achieves unitary PF, and the aforementioned equalization condition. This result naturally leads to the formulation of a problem of optimization of the parameters of the compensator. Copyright © 2011 John Wiley & Sons, Ltd.     

Application of local variations and maximum sensitivities selection for optimal placement of shunt capacitor banks under nonsinusoidal operating conditions

A new iterative algorithm is proposed for optimal sizing and placement of fixed and switched capacitor banks in radial distribution lines in the presence of linear and nonlinear loads. The method is a combination of maximum sensitivities selection (to improve convergence by selecting candidate buses) and local variations (to improve accuracy in the permissible solution region) and is implemented using the HARMFLOW codes. Objective functions include minimum energy losses, peak losses and capacitor costs while IEEE-519 power quality limits are used as constraints. The 18 bus IEEE distorted system is used to investigate the advantages and limitations of the proposed algorithm and compare its performance with the maximum sensitivities selection (MSS) method. The contributions of the proposed algorithm, as compared to prior publications, are the consideration of harmonic couplings and reactions of actual nonlinear loads, improved convergence and more accurate solutions.     

风-光-储能源系统变工况动态仿真研究

新能源的规模化高效利用已成为我国构建清洁高效能源体系,实现碳中和战略目标的重大需求。本文耦合风电、光伏以及光热发电形成综合型风-光-储能源系统,拟通过相对可控的光热发电平抑风电、光伏发电的随机波动性,进而在系统整体层面实现电功率的平滑输出。本文据此建立了系统关键设备的数学模型,研究了时变风光资源条件下系统变工况运行的实时响应特性,在此基础上,制定了熔融盐蓄热主动调控策略以平抑风电、光伏发电的波动性。结果表明,相比于单一的风电、光电电站,风-光-储能源系统的负荷跟随能力显著提高,负荷跟随匹配度从78.94%提高至93.90%,能源利用率增加至19.68%,弃电率从18.51%下降至0.96%,负荷波动幅度也从120 MW减小到25 MW左右。     

高海拔环境下智能电能表运行稳定性分析

针对环境影响智能电能表运行稳定性的问题,通过在西藏羊八井高海拔环境下开展长时间现场运行试验,研究智能电能表功率误差在实际运行过程中伴随日历时间的演化过程,通过分析在不同功率因数和电流条件下功率误差演变的差异性以阐释功率因数和电流对功率误差影响规律,通过分析在不同温度、湿度、辐照条件下电能表功率误差的变化阐明环境因素对电...     

移动气象计量现场校准核查信息系统

针对自动气象站现场较准核查工作需求,设计了移动气象计量现场核查校准信息系统。以VB编程技术和数据库技术为基础,采用串口通信和基于EXCEL的VB报表制作等方式,完成了自动站常用采集器DT50与ZQZ-CII的自动校准,以及温度、湿度、气压、风向风速、雨量、蒸发、辐射的现场校准与核查。系统通过在区域站现场较准核查工作中实际应用,能够对采集的数据进行处理,合格判断,并将数据保存到数据库中,实现数据查询,校准证书打印和数据记录表输出等功能。所设计系统为气象计量工作提供了一个智能化的现场校准核查平台,提高了气象计量的工作效率和自动化水平,保证了自动气象站的正常运行和数据的准确可靠。     

综合能源系统综合需求响应行为研究

面向耦合电、气、冷、热等多种形式能源的综合能源系统,研究柔性负荷、储能和电动汽车等需求侧资源的综合需求响应,有利于挖掘多能负荷的响应潜力,激发综合能源系统的灵活性,提升能源利用效率。首先以区域电-气互联综合能源系统为基础,构建了园区级冷-热-电-气综合能源系统,其次建立了综合能源系统调度模型,通过节点能量平衡方程分析节点能源价格,明确了系统调度-能源价格-综合需求响应的传递关系,然后基于节点能源价格建立了考虑柔性负荷、储能、电动汽车为参与主体的综合需求响应模型;最后通过算例分析了柔性负荷、储能、电动汽车的响应情况,基于节点能源价格对不同位置多能用户综合需求响应前后的负荷曲线进行了分析。     

电压不平衡时单同步坐标系锁相环的改进算法

为了在电网电压不平衡时能跟踪电网电压基波相位和频率,分析了单同步坐标系的三相软件锁相环(SSRF-SPLL)在电网电压不平衡时不能准确快速锁定基波电压相位的原因,即电网电压不平衡时,dq变换得到的eq中含有二次谐波分量,在使用PI控制时,此二次谐波分量将导致PI难以实现无误差跟踪,影响锁相输出角度。在提高稳态性能并考虑动态性能的基础上,提出了在PI调节器之前增加2次陷波器和特定截止频率的低通滤波器的改善方案。最后通过搭建仿真和实验平台验证了方案的可行性和有效性。     

现场运行环境与电应力对电能表计量误差影响研究

针对智能电能表现场计量精度问题,利用现场运行数据分析温度、电流、功率因数对批量电能表计量误差及其一致性的影响.基于正态分布计算电能表计量误差的均值和标准差,利用三倍标准差开展计量误差一致性分析.基于正弦函数构建电能表计量误差伴随日历时间的演变规律模型,在分别阐明功率因数和电流应力对电能表计量误差均值和标准差影响的基础上,基于艾林模型构建环境温度和电应力作用下电能表计量误差响应模型,以阐释温度和电流对电能表计量误差的综合影响.统计分析发现,温度越低、电流越大,电能表计量误差越大.依据研究结果可以补偿电能表计量误差,提高计量结果准确性,同时对进一步优化电能表运维方案,改进设计也具有参考价值.     

一种射频信号相位差校准方法及系统实现

通信系统中通道材料和环境会对射频信号的相位产生影响,针对传统相位校准方法存在校准频率低、误差大的问题,提出了一种基于软件无线电技术的相位差校准方法。利用快速傅里叶变换和坐标旋转数字计算机求解频谱最大谱线处的相位值,结合数字正交技术完成信号的相位校准。以亿门级FPGA为核心搭建实验平台对该方法进行了实验测试,利用Xilinx Artix 7产生参考和待校准信号,设计亿门级FPGA的DDR3存储、相位差测量、校准等逻辑电路完成相位差校准。测试结果表明,对于相位差为-90°~90°范围内频率为1 GHz的射频信号,经系统校准后相位差的相对误差小于03%,均方根误差仅为007°。     

电能表现场校验技术研发应用现状及其发展趋势(上 )

较全面地梳理了国内外电能表现场校验技术、校验装置的研究和应用现状。注意到接收数字量的数字化电能表的现场校验方法有待深入研究,数字化电能计量量传体系急需建立;电力负载的强非线性、波动性和随机性,对如何准确计量其实际耗用的电能,以及如何校验电能表的计量准确性等均提出了挑战。在此基础上,展望了电能表现场校验技术的进步方向及发展趋势。     

双碳目标下含P2G与需求响应的综合能源系统双层优化

在“双碳”目标背景下,对能源系统节能与减排提出了更高的要求。综合能源系统(IES)作为能源系统节能减排的主要载体,为深度发挥IES中用户侧与社区运营商的减排能力,文中提出将用户侧参与需求响应的负荷分为刚性负荷、价格型敏感负荷与碳价型敏感负荷,并在社区运营商中增设P2G设备。在此基础上,建立了用户与IES运营商参与的双主体阶梯碳交易机制,并建立双层优化模型。上层模型为IES运营商运营收益最大,下层模型为用户侧受到园区内碳价与分时能源价格下的用能费用最小。与传统优化模型相比,用户侧行为不仅受到能源价格影响,还受到碳交易价格的影响。此外分析敏感型负荷对需求响应的影响,需求响应及P2G联合优化在IES上的节能减排优势。最后通过4种情境下的仿真,验证了所提模型的有效性。     

Dual three phase transformation for comprehensive fault analysis of a six phase system

Recently there has been a growing interest in the concept of six phase transmission as an alternative to the upgradation of a line, to increase the power transfer capability within the existing right of way. In this work the six phase system is treated as two mutually coupled three phase systems and a transformation called dual three phase transformation (DTPT) is proposed for the analysis of a six phase system compared to earlier works on this subject. This method has reduced the number of significant combinations to 13, by choosing appropriate reference phases and renaming of the conductors, compared to 23 groups. The DTPT sequence networks are obtained in terms of the familiar three phase sequence components avoiding the use of complex ratio or phase shifting transformers, mutual inductances and the results completely agree with the results of fault analysis using the phase coordinate method. In a companion paper titled “Transposition of a six phase transmission line” it has been established that in the case of conversion of an existing double circuit three phase transmission line into a six phase line, a three barrel transposition somethat similar to the transposition of a double circuit line is sufficient, in which case there is mutual coupling only between the two zero sequence components of the two mutually coupled three phase systems which constitute the six phase system.     

电能表现场校验技术研发应用现状及其发展趋势（下）

较全面地梳理了国内外电能表现场校验技术、校验装置的研究和应用现状。注意到接收数字量的数字化电能表的现场校验方法有待深入研究,数字化电能计量量传体系急需建立;电力负载的强非线性、波动性和随机性,对如何准确计量其实际耗用的电能,以及如何校验电能表的计量准确性等均提出了挑战。在此基础上,展望了电能表现场校验技术的进步方向及发展趋势。     

Stochastic maximum power point tracking of photovoltaic energy system under partial shading conditions

A large portion of the available power generation of a photovoltaic (PV) array could be wasted due to partial shading, temperature and irradiance efects, which create current/voltage imbalance between the PV modules. Partial shading is a phenomenon which occurs when some modules in a PV array receive non-uniform irradiation due to dust, cloudy weather or shadows of nearby objects such as buildings, trees, mountains, birds etc. Maximum power point tracking (MPPT) techniques are designed in order to deal with this problem. In this research, a Markov Decision Process (MDP) based MPPT technique is proposed. MDP consists of a set of states, a set of actions in each state, state transition probabilities, reward function, and the discount factor. The PV system in terms of the MDP framework is modelled frst and once the states, actions, transition probabilities, and reward function, and the discount factor are defned, the resulting MDP is solved for the optimal policy using stochastic dynamic programming. The behavior of the resulting optimal policy is analyzed and characterized, and the results are compared to existing MPPT control methods.