三相四线制D-STATCOM/HESS系统在配电网中的应用及其仿真研究

针对配电网中存在谐波、无功以及负荷频繁波动等问题,提出了含混合储能(HESS)的三相四线制配电网静止同步补偿器(D-STATCOM),实现配电网无功补偿和谐波抑制,平抑负荷有功功率波动。首先,针对三相四线制配电网,通过对传统ip- iq谐波电流检测法改进,实现了对负荷所需的有功、无功和谐波补偿电流的准确检测。在此基础上,将超级电容器和铅酸蓄电池组成的混合储能系统引入到补偿装置中,实现了对配电网有功、无功和谐波电流的全补偿。结合不同储能装置的充放电特性,采用协调控制方法,确保系统对配电网能量的迅速准确补偿。最后结合某建筑配电网实际负荷,验证了三相四线制D-STATCOM/HESS系统及其控制算法在谐波抑制、无功补偿和平滑负荷有功波动方面的有效性。     

Harmonic estimation using RLS algorithm and elimination with improved current control technique based SAPF in a distribution network

This paper presents the application of well known recursive least square (RLS) harmonic estimation technique and its elimination with improved current control technique based shunt active power filter (SAPF) in a distorted power network. The estimation of amplitude and phase angle of fundamental and harmonics is performed using RLS algorithm, known for their simplicity of computation, accuracy and good convergence properties. The estimates are updated recursively as samples of the harmonic signals are received. In order to eliminate harmonics produced by the nonlinear load connected in the distribution network, a three-phase SAPF with modified current control technique is employed. In this paper, based on the analysis and modeling of SAPF with closed-loop control, a feed forward compensation path of load current and a new pulse width modulation (PWM) control scheme is proposed to improve the dynamic performance of the SAPF. In this case the amplitude and phase angle of the converter AC voltage should be adjusted using PWM, thus producing either leading or lagging reactive power. Harmonic contented in the signal is estimated at the point of common coupling (PCC) with and without SAPF. The comparative results of amplitude and phase angle of fundamental and selected harmonics are determined considering installation of SAPF in the distribution network. The system is studied using MATLAB environment to justify the effectiveness of proposed control technique in comparison to the other techniques discussed in the recent literature.     

An improved control strategy for hybrid series active filter dealing with unbalanced load

This article presents an improved control strategy for hybrid series active power filters (HSAFs) working with nonlinear and unbalanced three‐phase three‐wire loads. An algorithm based on the instantaneous power theory is introduced to precisely extract only harmonic components from supply current, even this current is contaminated with negative sequence components due to the imbalance of the load. An improved control strategy based on that sequence extraction algorithm is proposed and investigated in detail by numerical simulations. The proposed control method has shown a better performance in mitigating harmonics, especially for the nonlinear and unbalanced loads. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Electricity market equilibrium of nonlinear power systems with reactive power control

The impact of reactive power control on the electricity market equilibrium is investigated. The effects of limitations on the reactive power generation and absorption, and load power factor adjustments, are examined using a novel electricity market equilibrium model that solves large-scale nonlinear power systems with asymmetric strategic firms. The algorithm implemented employs the linear supply function theory for bid-based pool markets. AC power flow analysis is used to represent the electricity network, incorporating variable price-responsive active and reactive load demands. The significance of the reactive power modeling in the electricity market equilibrium is demonstrated using the IEEE 14-bus and IEEE 118-bus systems. It is shown that variations on the reactive power in the system result in different market outcomes, as incentives are given to the strategic generating firms to alter their bidding strategies. The convergence characteristics of the IEEE 118-bus system are graphically presented and discussed to demonstrate the superior computational performance of the proposed algorithm in producing results under strict binding constraints and heavy transmission congestion conditions.     

基于LMD和模型匹配的家电负荷识别算法

家电负荷识别是智能用电的重要环节,传统侵入式负荷监测具有成本高、安装维护复杂的缺点,因此以非侵入式负荷监测为基础研究家电负荷识别算法。结合系统辨识的基本原理和方法,以稳态电流、稳态电压为特征,提出一种基于局部平均分解(LMD)和模型匹配的家电负荷识别算法。通过预先获取用电网络中各负荷的稳态数据,构建线性和非线性模型库。利用LMD算法将混合信号分解为单个负荷的用电数据,通过预筛选确定分离数据所属模型库,根据模型匹配原则进行负荷识别。仿真结果表明,所提算法可以准确识别出各负荷的运行状态,运算效率高,并能有效应对用电网络中有新负荷加入的情况。     

基于IEEE 1459标准的非线性负载有功功率测量研究

针对谐波有功损耗测量问题,文中改进了Emanuel功率理论中非线性负载等效模型,并结合基于Emanuel功率理论的IEEE 1459标准中视在功率分解公式,推导了基于改进的非线性负载等效模型的谐波有功损耗测量表达式;利用Matlab仿真分析非线性负载有功损耗的3种测量方式;通过比较得出所提测量方法能更准确方便地测量非线性负载有功损耗。最后,利用电能质量测量仪器,实测某电网10 kV负载谐波含量,结合所提方法计算负载有功损耗,验证了该方法的有效性及其带来的经济效益。     

基于相空间重构和长短期记忆算法的电力系统无功负荷预测模型

为了优化无功控制策略,改善电压质量,减小网损,针对无功负荷的随机性与非线性,提出一种基于相空间重构和长短期记忆神经网络的无功负荷预测模型。利用C-C 法确定最优重构维数和延迟时间;通过计算最大Lyapunov指数说明无功负荷的混沌性;利用相空间重构技术将无功序列映射到高维空间,在高维空间利用长短期记忆神经网络进行预测;最后以海南省某地区的有功及无功负荷数据为例,通过Kolmogorov熵证实无功负荷的混沌程度大于有功负荷的混沌程度,算例验证了该方法的可行性,能提高无功负荷预测结果的准确度,有利于对电力系统无功进行更合理的调配和控制。     

A three‐phase,active power filter with a predictive‐instantaneous‐current PWM controller

One of the most emphasized problems to be solved in power systems in recent years is the line‐current harmonics problem. This is due to the use of diode rectifiers, PWM converters, nonlinear loads, and so on. To reduce or eliminate such current harmonics, an active power filter (APF), which is a sophisticated power electronic converter, has been studied and used in some practical applications. In this paper, we propose and discuss two new control methods for three‐phase shunt APFs: the sinusoidal line‐current control method and the instantaneous‐reactive‐power compensation control method. They are based on pulsewidth prediction control, or a predictive‐instantaneous‐current PWM control. Neither any instantaneous power information nor coordinate transformation is necessary for control. In the sinusoidal line‐current control scheme, the controller governs the switching devices of the APF by using the pulse width that is optimally predetermined at the beginning of every switching period with the sinusoidal current reference. The line currents flow sinusoidally and are in phase with the voltage accordingly. In the instantaneous‐reactive‐power compensation control, the control is performed so that the resultant circuit of the load and the APF is regarded as a time‐variant conductance circuit model. The APF with this control scheme can cancel effectively the instantaneous reactive component produced by the load though the controller is simple. This paper discusses the performance characteristics of the APFs when a three‐phase diode rectifier and an unbalanced load are connected to the line. The practicability of the proposed methods is verified by experiment. © 1999 Scripta Technica, Electr Eng Jpn, 130(3): 68–76, 2000     

一种基于Hilbert数字滤波的无功功率测量方法

提出了一种基于Hilbert数字移相滤波的无功功率测量方法。该方法不仅能测量正弦电路中的无功功率，而且在给定的定义下，也适合于测量含有谐波的非正弦电路中的无功功率。由于该方法是在对电压、电流信号采样后，通过直接进行移相滤波和简单的数值计算测量出无功功率，避免了现有方法中通过测量电压、电流有效值和有功功率计算无功功率所带来的误差。此外，由于所设计的Hilbert数字移相滤波器具有优越的频率响应特性，即使对于相当高次谐波无功功率的测量，也能获得很高的测量准确度。所测无功功率的正负值还可以直接用于判断负载的性质。该方法在将模拟电压、电流信号转化为数字采样信号之后所进行的处理工作都是数字化的，设计简单、便于实现。文中所提出的方法已用于某种高精度数字多用表的设计中。     

考虑负荷不确定性的多目标交直流系统无功优化

提出了一种考虑负荷不确定性的多目标交直流系统无功优化方法,研究负荷模型的不确定性对交直流系统无功优化的影响。本文将系统有功损耗最小、系统电压稳定裕度最大作为目标函数,基于负荷误差的正态分布特征,并利用二层规划理论方法,建立考虑负荷不确定性的多目标交直流系统无功优化数学模型。针对交直流无功优化非线性、多变量、多约束的特点,采用内点法和遗传算法相结合的混合优化算法求解上层模型,下层模型采用实数编码的改进遗传算法求解。采用基于IEEE30标准节点改进的交直流算例对提出的方法进行验证,结果验证了本文提出方法的可行性及有效性。     

A novel probabilistic neural network‐based algorithm for classifying internal fault in transformer windings

The major function of protective devices in a power system is to detect the occurrence of faults and to isolate the faulty sections from the rest of the system. Much progress has been made in the development algorithms for detecting faults in power transformers, which depend on transients‐based techniques. This paper presents an algorithm based on a combination of discrete wavelet transforms and probabilistic neural networks (PNNs) for classifying internal faults in a two‐winding three‐phase transformer. Fault conditions of the transformer are simulated using alternative transients program/electromagnetic transients program (ATP/EMTP) in order to obtain current signals. The mother wavelet Daubechies4 is employed to decompose the high‐frequency components from these signals. All three phases of the differential current signals are used in the fault detection decision algorithm. The variations of first‐scale high‐frequency component that detects fault are used as an input for the training pattern. The training process for the neural network and fault diagnosis decision is implemented using toolboxes on MATLAB/Simulink. Various cases and fault types based on the Thailand electricity transmission and distribution systems are studied to verify the validity of the algorithm. Backpropagation neural network is also compared with the PNN in this paper. It is found that the proposed method gives satisfactory accuracy with less training time, and will be particularly useful in the development of a modern differential relay for a transformer protection scheme. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

检测单相系统谐波电流和无功电流的一种新方法

针对单相系统谐波电流和无功电流检测中存在的问题,提出一种新的检测方法:基于瞬时无功功率的虚拟三相法.通过理论分析和仿真实验论证,表明这种算法能有效解决单相系统和三相不平衡系统中谐波电流和无功电流检测中存在的问题,且检测精度高,动态响应快.     

新型电力系统动态负荷电能测量算法

针对新型电力系统构建中,电网高比例新能源接入,大功率非线性动态负荷增加,电力负荷随机性、波动性和间歇性导致电能测量算法失准,引起电能表计量超差的问题,文中构建了有功电能卷积和测量算法,以及有功电能累加功率阈值约束条件;通过分析低通滤波器输入端功率阈值判断方法是导致传统有功电能测量算法失准的重要原因,提出了改进约束条件的有功电能测量算法,采用抽样响应系数矩阵抽取方法,进一步提出了非交叠抽取动态有功电能测量算法。仿真实验表明：改进约束条件的有功电能测量算法与非交叠抽取动态有功电能测量算法的误差小于传统电能测量算法,可有效解决动态情况下传统电能测量算法失准的问题。     

基于改进鸡群算法的非侵入式负荷监测

监测负荷运行状态有利于加强电网负荷侧管理,引导用户合理消费,实现节能降耗。针对小功率负荷与大功率负荷同时投入时,单一谐波电流特征易受线路电压、电流波动影响导致负荷辨识精度低的问题,提出一种基于改进鸡群算法的负荷监测方法,设计综合考虑稳态谐波电流和功率特征的正态分布度量函数,作为改进鸡群算法的适应度函数。实验结果表明,采用所提方法可有效提高负荷辨识准确率。     

风力发电系统网侧逆变器双闭环控制策略研究

针对风力发电系统经过并网逆变器与外部电网连接时,系统向电网输送的电能必须满足电网的电压和频率要求。在分析系统变流器的数学模型基础上,对网侧逆变器提出了一种基于无功电压调节的电压电流双闭环控制策略,通过调节无功实现系统母线电压幅值稳定,也实现了系统有功无功解耦控制,且输出电流谐波含量少,使系统向电网输送稳定、恒频率的电能。经过仿真分析,在负载变化情况下系统可实现稳定控制及具有良好的电流鲁棒性,有效验证该控制策略的可行性和准确性,对风力发电并网技术研究具有一定的实用价值。     

Analysis and effective controller design for the cascaded H‐bridge multilevel APF with adaptive signal processing algorithms

The cascaded H‐bridge (CHB) multilevel inverter is being recognized as the most suitable topology for high‐power medium‐voltage power quality conditioning applications. This paper presents mathematical modeling and effective controller design methodology for the CHB‐based active power filters (APFs), which achieves dynamic reactive power and harmonic compensation. The most crucial problems in CHB‐APF control are the simultaneous requirements of both accurate harmonic current compensation and the dc‐link voltage stabilization among the H‐bridges, which is the prerequisite for the stable operation of CHB‐APF. To achieve dc‐link stabilization, a novel voltage balancing algorithm is proposed by splitting the dc‐link voltage control task into two parts, namely, the average voltage control and the voltage balancing control, where the sine and cosine functions of the phase angle of the fundamental component of the grid voltage are used, respectively. To ensure accurate phase tracking, a novel phase‐locked loop (PLL) is proposed by using the adaptive linear neural network (ADALINE), where the grid voltage background distortion is also taken into account. The superior performance of the ADALINE‐PLL is validated by comparison with the existing PLLs in literatures. Furthermore, the proportional‐resonant (PR) controller is used for the reference current tracking. A separate ADALINE algorithm is applied for reference current generation (RCG) for the CHB‐APF. The excellent performance of the ADALINE‐based RCG scheme is verified by comparison with the existing RCG schemes, namely, the low‐pass filter approach and the single‐phase p ? qmethod. The experimental results on the three modules CHB‐APF are presented, which verifies the effectiveness of the proposed control algorithms. Copyright © 2011 John Wiley & Sons, Ltd.     

A nonintrusive fast residential load identification algorithm based on frequency‐domain template filtering

User‐side load monitoring is a key technology to realize smart utilization of electric power. Since the traditional intrusive load monitoring involves a comparatively large economic cost and execution complexity, this paper studies a way to rapidly identify residential power load in a nonintrusive monitoring mode. A template‐filtering‐based nonintrusive, rapid residential load identification algorithm is proposed, which is based on frequency‐domain analysis of current signals, in combination with the current model when the nonintrusive monitoring load is in operation, and by making use of the fact that the spectrum components of the current signals working independently are completely contained in the hybrid current spectrum. Characteristic currents of the various loads in the power grid are acquired a priori to establish the characteristic filter, and 0–1 valuation is performed on their spectrum components to get the template filter. The template filter is then used to filter the hybrid current signals captured in the nonintrusive mode, and the operation status of the loads is judged and determined after quantification of the filtered frequency components. For the same type of load under different operating conditions, the template filter can be commonly used. Efficiency of the algorithm is verified by making use of the actually collected power consumption data, which is able to accurately identify the load operation status. Furthermore, the algorithm is shown to be highly efficient and can be realized via fast Fourier transform (FFT), and its hardware packaging can be easily realized. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

考虑主动管理措施的配电网无功补偿双层优化配置

为了适应未来大量分布式电源(DG)并网及自动化水平显著提高的主动配电网发展,在规划阶段应该考虑主动管理措施,优化系统运行方式。同时,现有的无功补偿规划研究忽略了DG及负荷的不确定性。为此,计及间歇性DG及负荷的不确定性,提出主动配电网无功补偿双层优化配置模型。上层规划以无功补偿电容器的投资成本、网络损耗费用综合最优为目标函数,下层规划在此基础上考虑调节无功补偿容量及调节有载变压器抽头两种主动管理措施,对每个场景进行优化。采用K-均值聚类法对场景进行缩减,结合和声搜索算法和粒子群算法联合求解模型。通过IEEE33节点算例进行仿真计算,验证所提模型和方法的正确性。     

A new control strategy for active power line conditioner (APLC) using adaptive notch filter

This paper proposes a new adaptive control algorithm for a three-phase current-source shunt active power-line conditioner (APLC) operating under unbalanced and distorted network conditions. This control scheme aims at compensation of network’s reactive power, elimination of active power’s oscillating components, compensation of network current and voltage harmonic contents resulting in sinusoidal waveforms, and equilibrating the drawn power from the source evenly between the three-phases. Unlike many of the existing methods, the proposed strategy does not require any coordinate transformations or complicated calculations. The reference signals for the hysteresis-band current controlled voltage-source converter (HBCC-VSC) are generated by passing the measured current and voltage signals through two layers of modified adaptive notch filters (ANFs). To ensure superb performance and minimum total harmonic distortion (THD) level of the power system, parameters of the HBCC-VSC are obtained using differential evolution (DE) optimization algorithm. The proposed strategy is simple, easily implementable, and robust against uncertainty or variations of power system parameters and loads. The effectiveness of the proposed control scheme is validated by simulation results of a selected network under various load and power system conditions.     

基于结构熵权法的非侵入式家电识别研究

单一特征所得到的识别结果可能会与实际用电情况不一致,并且居民用电行为是影响负荷识别的重要因素之一,为了更可靠地提升非侵入式电力负荷的分解能力,提出将居民用电行为作为负荷识别的特征之一,并通过结构熵权法将居民用电行为与有功功率、无功功率和电流谐波特征相结合的多特征识别算法,即将定量分析的熵值法和定性分析的主观赋值法相结合,确定最终权值,获得负荷识别结果。最后,采用案例分析,对采用结构熵权法的多特征识别算法与单一特征以及未考虑居民用电行为的负荷识别方式进行对比。结果证明,考虑居民用电行为的多特征识别算法可以有效地提高负荷识别的准确率。