Effect of harmonic distortion in reactive power measurement

The authors present the effect of harmonics on reactive power measurements and offer a new method for calculating active, reactive apparent, and residual power in nonsinusoidal conditions. The method considers common and uncommon harmonic components of voltage and current waveforms. It properly defines all power components at different harmonic frequencies, such as rotating real power, quadrature power, and the residual power (distortion). Each component is calculated correctly at different frequencies to define its physical meaning. A computer algorithm is developed to calculate all the power components for any distorted voltage and current waveforms     

Testing the performance of three-phase induction watthour meters inthe presence of harmonic distortion

Computer-based testing of a three-phase induction watthour meter in the presence of harmonic distortion is reported. Two three-phase harmonic generators produce the distorted current and voltage waveforms. Each waveform consists of prespecified harmonic magnitude and phase. Therefore, balanced or unbalanced conditions can be simulated in the testing. A fiber optic sensor is designed to convert the rotation of the disk of the meter into digital signals to be stored in an IBM PC/AT. A data acquisition system transfers the samples of current and voltage waveforms to compute the power and energy for comparison. Presented are: the computer-based harmonic generator facilities for testing, the testing procedure, and the impact of the different harmonics magnitude and phase angle on the meter's registration error     

Evaluating power system unbalance in the presence of harmonic distortion

This paper presents a new method to evaluate power system unbalance in the presence of harmonic distortion. The balanced, the first unbalanced, and the second unbalanced components are obtained from the original three-phase current and voltage phasors of each harmonic component. The equivalent root-mean-square (RMS) value of three-phase voltage and current is then decomposed into the balanced fundamental, the unbalanced fundamental, the balanced harmonic, and the unbalanced harmonic components. The same decomposition is applied to the apparent power, and the system unbalance can then be evaluated through the proposed system total unbalance distortion factor. The unbalanced fundamental, the balanced harmonic, and the unbalanced harmonic distortion factors are defined. These distortion factors clarify the interleaving between the unbalance and harmonic distortion, and are suitable for unbalance evaluation in the presence of harmonics. Numerical examples are also presented to illustrate the application of the proposed method on the study and characterization of unbalance in power systems.     

数字式真无功电能表测量原理及四象限无功概念

介绍了数字式真无功电能表的测量原理和特点，以及四象限无功的基本概念。     

Background voltage distortion influence on power electric systems in the presence of the Steinmetz circuit

In traction systems, it is usual to connect reactances in delta configuration with single-phase loads to reduce voltage unbalances and avoid electric system operation problems. This set is known as Steinmetz circuit. Parallel and series resonances can occur due to the capacitive reactance of the Steinmetz circuit and affect power quality. In this paper, the series resonance “observed” from the supply system is numerically located. The study of this resonance is important to avoid problems due to background voltage distortion. Experimental measurements are also presented to validate the obtained numerical results.     

基于反馈解耦控制和畸变矫正的单相无功补偿策略

分析了单相逆变系统并建立了单相逆变器在d-q轴下的有功无功模型.该有功无功模型和三相系统一样,可以借用反馈解耦控制进行有功无功的控制.为了实现单相d-q变换,论文给出了一种滑动窗口滤波的方法.但是滑动窗口使得有功和无功不能完全解耦,从而反馈解耦控制系统的动态效果较差.为了克服这些缺点,文中提出了一种畸变矫正的方法,这种...     

风电机组无功动态响应性能评价

风电场无功对电网有较大的影响,目前相关标准对风电场动态无功响应时间、持续时间提出了要求,却未对风机的无功动态响应性能提出要求,因此,提出风机无功功率响应时间、响应能力和支撑能力指标,实现对风电机组无功动态响应性能的定量评价。利用PSD-BPA仿真及实际风电场电压、无功运行监测数据对风机无功功率支撑能力指标的有效性进行验证。该指标值与风机暂态电压稳定极限值正相关,风机电压跌落深度越小,风机发出无功持续时间越长,该值越大,说明风机无功支撑能力越强。     

Power distortion and reactive power compensation by means of an active filter with predictable relay control

For different types of power consumers, an investigation of the simulation of the compensation quality of power distortion and reactive power by means of an active filter with predictable relay control has been carried out.     

Evaluation of actively clamped resonant link inverter forlow-output harmonic distortion high-power-density power converters

The suitability of a soft-switched actively clamped resonant DC-link (ACRDCL) inverter for low-output harmonic distortion/high-power-density power conversion is evaluated. Modulation and control techniques for achieving low-output harmonic distortion are described. Performance and power density of the ACRDCL inverter are maximized through the optimal design of the clamp circuit, resonant components, and output filter components. The ACRDCL inverter simulation and design are validated experimentally. For the same output kilovoltamperes, efficiency and harmonic performance as the ACRDCL inverter, hard-switched designs are compared. Methods to increase the power density of the ACRDCL are proposed, including the use of recently developed nonpunchthrough insulated gate bipolar transistors     

电力市场条件下的无功优化研究

在电力市场条件下,传统无功优化的目标函数应做相应的修改,由原来的一次能源消耗量最小转变为经济利益最大。由于无功电量要定价,所以电网公司购买的无功电量应计入目标函数。同时．无功优化对电网公司购买有功电量也会产生很大的影响,通过改进遗传算法对新的目标函数进行优化。具体算例表明,新的无功优化数学模型可行,并具有很好的经济性。     

Linearization: reducing distortion in power amplifiers

This article discusses techniques for the cancellation of distortion (linearization) in power amplifiers. Different methods of linearization are introduced and compared. The linearization of solid-state power amplifiers (SSPAs), traveling-wave tube amplifiers (TWTAs) and klystron power amplifiers (KPAs) are considered. Although the focus of this article is on power amplifiers, many of the techniques are applicable to other components such as mixers, low-noise amplifiers, and even photonic components, such as lasers and optical modulators     

A new reactive,distortion and non-active power measurement method for nonstationary waveforms using wavelet packet transform

The definitions of power components that are contained in the IEEE Standard 1459-2000 [IEEE Std. 1459-2000, Definitions for the measurement of electric quantities under sinusoidal, non-sinusoidal, balanced or unbalanced conditions, 2000] are based on the Fourier transform (FT) which is suitable only for the case of stationary waveforms. However, for nonstationary waveforms, the FT produces large errors. Therefore, the power components based on this transform become inaccurate. A new approach based on the wavelet packet transform (WPT) for defining these power components is developed in this paper. The advantages of using the wavelet transform are that it can accurately represent and measure nonstationary waveforms, providing uniform frequency bands while preserving both time and frequency information. In addition, this paper addresses the problem of choosing the most appropriate mother wavelet for power components measurements. The results of applying both approaches to stationary and nonstationary waveforms show that the currently used definitions according to the IEEE Standard 1459-2000 result in large errors for the case of nonstationary waveforms while the proposed approach (WPT based) gives more accurate results in this situation.     

浅谈电力系统中电压无功功率的控制

电力系统的负荷需要消耗大量的无功功率,而无功功率平衡要满足众多的结点电压,就需要分级分层就地平衡。地区电网的电压无功控制,主要是控制其管辖范围内的各级变电站,使电网的电压合格,并实现无功的就地平衡,降低网损。为此,通过分析变电站电压无功控制的主要设备：有载调压变压器、并联电容器以及并联电抗器,说明变电站电压无功控制的原则、要求、实现方式。     

基于无功功率波动系数的无功功率考核方法

针对现行的均权平均功率因数考核方法不能反映用户无功功率负荷特性,不能对影响电能质量的用户加收改善电能质量的电费问题,提出了一种基于波动系数的无功功率考核方法.该方法通过动态无功补偿装置或专用的无功检测设备,记录无功功率的变化规律,根据设定的无功功率允许波动范围,将超出范围的不同时段无功功率波动陡度系数与幅度系数乘积的和定义为无功功率波动系数.采用与电费收费对应时段内无功功率波动系数与均权平均功率因数共同对用户的无功功率进行考核,促使用户主动改善电能质量,提高电能的使用效率.     

基于无功功率波动系数的无功功率考核方法

针对现行的均权平均功率因数考核方法不能反映用户无功功率负荷特性,不能对影响电能质量的用户加收改善电能质量的电费问题,提出了一种基于波动系数的无功功率考核方法。该方法通过动态无功补偿装置或专用的无功检测设备,记录无功功率的变化规律,根据设定的无功功率允许波动范围,将超出范围的不同时段无功功率波动陡度系数与幅度系数乘积的和定义为无功功率波动系数。采用与电费收费对应时段内无功功率波动系数与均权平均功率因数共同对用户的无功功率进行考核,促使用户主动改善电能质量,提高电能的使用效率。     

Fuzzy reactive power optimization in hybrid power systems

Reactive power control, which is one of the important issues of power system studies, has encountered some intrinsic changes because of the presence of the hybrid AC/DC systems. The uncertainty in determination of some ill-defined variables and constraints underlines the application of fuzzy set as an uncertainty analysis tool. Herein a fuzzy objective function and some fuzzy constraints have been modeled for the purpose of reactive power optimization then this fuzzy model is dealt with as a linear programming problem to be solved. Contrary to the separate modeling of the conventional AC/DC optimization methods, this study attempts to attain the most optimal solution by the simultaneous employment of the total contributing factors of both AC and DC parts. In this way, the conventional issue of the coordinated control of firing angle and the transformer tap of the DC terminals is resolved, yet the method provides more flexibility to gain the most optimal condition since it uses more control factor for solving the optimization problem. The proposed method is performed on the modified IEEE 14 and 30-bus systems; and it is shown to have less computational burden and further minimized objective function than the conventional method.     

电力系统无功测量方法综述

无功测量在电力系统中有着重要的地位和作用.本文分正弦和非正弦两种情况,论述了包括移相法,积分法,Hilbert法等在内的几种主流各种无功测量方法,对现有方法的精度和误差进行了分析,探讨了各种方法下的误差应对策略.并简要介绍了各种方法的软硬件实现的可行性.     

浅析无功补偿在电网中的发展趋势

阐述了无功功率在电压稳定和谐波抑制方面的作用,根据宁夏电网无功补偿的实际情况和发展趋势,分析了3种动态无功补偿装置（SVC）的原理,介绍了无功补偿方式的发展趋势和方向。     

Security-constrained reactive power dispatch

A method of solving the preventive security-constrained reactive power VAr dispatch problem is presented. A decomposition-coordination scheme is conceived in order to take advantage of the special structure of the problem. Instead of tearing the network, the problem itself is decomposed into smaller subproblems. Techniques are presented for contingency simulation and for the handling of these contingencies in the optimization process. The computing procedure is given for the step-by-step solution for online implementation. VAr-oriented load flow and optimal power flow methods are described. Numerical testing results are reported     

低压电网无功补偿对功率因数的影响

分析了无功补偿的作用和补偿容量的选择方法,着重论述了低压电网和异步电动机无功补偿容量的配置。结合应用实例,说明采用无功补偿技术,提高低压电网和用电设备的功率因数,已成为节电工作的一项重要措施。