基于二阶广义积分器的谐波电流检测算法

为解决谐波电流检测算法问题,依据三相负载电流在αβ坐标系下的表现形式,提出了一种基于二阶广义积分器的谐波电流检测方法,适用于三相三线制对称和不对称系统。该方法通过Clark变换将三相电流信号转化为静止坐标系下的两相电流,再分别利用二阶广义积分器的特性提取基波电流分量,最后通过反Clark变换将基波电流分量变换成三相电流,与电网电流相减后得到谐波电流,便于工程中有源滤波器只对谐波电流进行补偿。仿真结果表明,该方法简单可靠、易于数字实现、检测效果好。     

基于正弦幅值积分器的全电流谐波检测方法

基于瞬时无功功率理论的i_p-i_q谐波检测法,环节繁多且结构复杂,同时低通滤波器(low pass filter,LPF)的存在又影响了谐波检测的快速性。为了准确且快速检测出电网谐波电流,实现对电网的补偿,该文提出一种基于正弦幅值积分器(sinusoidal amplitude integrator,SAI)的全电流谐波检测法,该方法在i_p-i_q谐波检测法的基础上省去负载电流有功分量和无功分量的计算环节,利用SAI的正序基波提取结构替换原来检测法中的LPF,提取出正序基波电流经过运算得到谐波指令电流,从而对电网进行补偿。在平衡电网下对所提方法进行仿真与实验,验证了该方法的可行性和有效性。     

基于改进SOGIQ PLL与卡尔曼滤波的APF谐波检测方法研究

谐波污染的有效治理是电能质量控制的关键。基于有源电力滤波器可实现对谐波的跟踪及补偿的优点,电网中常采用有源电力滤波器实现谐波的治理,但有源电力滤波器谐波检测应用的传统ip-iq法存在检测精度低、速度慢的问题。正基于此,该文提出了一种融合二阶广义积分正交锁相环和卡尔曼滤波器的新型ip-iq谐波检测方法。以改进型二阶广义积分正交锁相环,提高相角检测准确度;以卡尔曼滤波器提升滤波跟踪实时性。通过理论推导结合仿真分析,结果表明该方法能实现谐波的有效补偿,从而提升谐波检测准确性。     

基于自适应容积卡尔曼滤波的动态谐波检测

对电网中的谐波进行实时、准确的检测是有效治理谐波的前提。针对某些运行工况下电网中出现的动态谐波,提出了一种基于自适应容积卡尔曼滤波的动态谐波检测算法估计谐波信号的幅值和相角。首先针对传统卡尔曼滤波处理非线性关系上的局限性,利用容积卡尔曼滤波不需要任何线性化关系的特性估计谐波的状态向量和误差偏差矩阵,然后引入噪声估值遗忘因子来实时更新系统的噪声矩阵方程。最后通过对比实验,验证了该算法在动态谐波检测上的优越性能,并将其应用于有源滤波器的谐波检测中。     

局部电网三相不平衡畸变电流补偿方法

在三相三线制局部低压配电网中,易出现电流畸变和三相不平衡情况,对设备运行及配电网安全造成不利影响。在采用有源电力滤波器（APF）进行谐波与三相不平衡综合补偿时,因传统[ip-iq]法无法有效消除二倍频分量,故补偿效果不甚理想。该文基于传统[ip-iq]方法提出了一种改进[ip-iq]法,得出了低通滤波器参数与APF补偿电流的定量关系,并据此进行了APF主要参数的设计。仿真与实验结果证明采用改进[ip-iq]法时,谐波与不平衡补偿的效果与低通滤波器的截止频率无关,保持了良好的稳定性,且提高了系统的响应速度。     

基于实测的三相不对称电力系统谐波阻抗估计

通过分析星形和三角形连接下的三相不对称电力系统,推导建立了三相不对称电力系统谐波阻抗的矩阵估计模型。模型基于大量系统和负荷公共联接点处的实测数据,采用多元线性回归法,对系统侧的谐波阻抗矩阵各元素值进行估计。仿真实验及误差分析表明,所得模型是准确有效的。提出的方法数据获取简单、线性回归模型计算速度快,可用作实时估计。该研究结果可作为三相不对称情况下估计非线性负荷的谐波发射水平和配置谐波滤波器的基础工作。     

基于电力载波的电动汽车充电电路谐波抑制CSCD

基于电力载波的电动汽车充电电路中的谐波会干扰PLC通讯影响系统稳定性.对三相四线不可控整流和高频功率变换电路中的谐波电流,采用指定次谐波控制策略的有源滤波和无源滤波相结合的方法,将检测到的负载电流信号中的n次谐波通过同步旋转坐标变换变为直流量,经低通滤波器提取后进行电流模糊PI控制,达到消除指定次谐波的目的.理论分析和仿真实验表明,该方法可有效滤除电流谐波,保证电流波形的正弦特性,为今后电动汽车充电站PLC通信建设提供理论参考.     

牵引供电系统谐波补偿分析

牵引供电系统中大量非线性元件的使用,在系统中产生了大量的谐波与无功电流。采用有功电流分离法,分离出牵引变压器副边的基波有功电流,从而得到补偿电流,利用有源电力滤波器对其进行补偿,通过MATLAB仿真,说明了补偿方法的可行性。     

电力系统的谐波电流及有源滤波器

讨论了电力系统有源滤波器的特性及原理,并提出了一种检测谐波电流的方法,该方法不仅可以检测出谐波电流,还可以检测出负序电流及波动电流。并采用有源滤波器进行了仿真,结果表明了该方法的有效性。     

应用并联型有源电力滤波器对空压机变频器进行谐波治理

针对山东中烟工业公司济南卷烟厂空压机变频器工作时产生的谐波电流导致厂内动力部分出现变压器温度过高、噪音增大、信号波动、通讯中断等故障现象,采用并联型有源电力滤波器进行谐波治理。对并联型有源电力滤波器的控制系统和主电路进行了介绍,给出现场谐波治理的方案。通过该滤波器现场运行效果表明,并联型有源电力滤波器具有理想的谐波补偿效果,同时降低了空压机运行的电流,实现节能降耗。     

基于小波神经网络的单相三电平逆变器谐波检测

本文采用小波神经网络（Wavelet Neural Network,WNN）算法对时变谐波信号进行检测。利用Harr小波对谐波信号的幅值和相角进行逼近;将小波对信号的自适应时频分割特性引入神经网络,提高神经网络的逼近和收敛速度;给出网络参数的选定方案;确定网络的训练算法。在MATLAB/SIMULINK环境下对该算法进行仿真,与传统的小波算法比较,该算法不仅可行,而且精确度得到提高。     

电力系统谐波、负序与无功电流复合补偿策略的研究

基于瞬时无功功率理论,提出了一种适用于三相三线制和三相四线制电力系统谐波、负序以及无功电流的复合补偿策略。数值仿真结果表明,该复合补偿策略的投入使用,可使电力系统综合补偿装置运行在有源电力滤波器和静止无功发生器功能相结合的复合工作模式,从而实现具有不对称非线性负载的电力系统的谐波抑制、无功补偿以及负载不平衡抑制等综合控制任务。     

Performance investigation of artificial intelligence based controller for three phase four leg shunt active filter

In this paper, the choice of power quality compensator is a DSTATCOM which constitutes a three phase four leg voltage source converter (VSC) with a DC capacitor. The control strategy proposed for the DSTATCOM is a neural network based one cycle control (OCC). This control strategy involves neural network block, digital circuits and linear elements, which eliminates the sensors required for sensing the load current and coupling inductor current in addition to the multiplier employed in the conventional method. The calculation of harmonic and reactive currents for the reference current generation is also eliminated, thus minimizing the complexity in the control strategy. The control strategy mitigates harmonic/reactive currents, ensures balanced and sinusoidal source current from the supply mains that are nearly in phase with the supply voltage, compensates neutral current, and maintains voltage across the capacitor under unbalanced source and load conditions. The performance of the DSTATCOM with the proposed artificial neural network (ANN) controllers is validated and investigated through simulations using Matlab software. The simulation results prove the efficacy of the proposed neural network based control strategy under varying source and load conditions.     

边缘检测小波对信号奇异性的检测在汽液两相流动中的应用

对于函数（信号）奇异性的检测方法主要是用小波变换实现的,小波分解具有良好的空间域和频率域的局部化特性,因此小波变换可以刻画出信号的变化规律以及对信号内奇异点的各种奇异性质进行检测和分析。对汽液两相的流动工况也可以用边缘检测小波变换去进行分析,并实现对汽液两相流动的热工数值检测。通过对汽液两相均相流动模型压力曲线的边缘检测,证明了边缘检测小波完全可以用于对汽液两相的流动工况进行边缘检测。     

1000kV同塔双回线路相序布置及导线安全距离研究

同塔双回线路共有六种相序布置方式,为选取最优相序,以皖电东送淮南—上海1000 kV特高压输变电工程为例,利用CDEGS软件包、MATLAB、EMTP程序,仿真计算了同塔双回线路各种导线排列方式下电场、磁场、无线电干扰、可闻噪声、自然功率、线路不平衡度和反击跳闸率。结果表明,相序布置对同塔双回线路的电磁环境、自然功率、线路不平衡度及耐雷性能等电气特性有一定的影响;线路的工频电场、自然功率和线路不平衡度是决定线路最优相序布置的关键因素。综合各种电气特性因素,得出了线路的最优相序布置——ABC/CBA;最后在最优相序布置下推算了1000 kV同塔双回线路跨域建筑物的安全距离。其计算方法与结果可供实际工程参考。     

Modeling and simulation of three phase multilevel inverter for grid connected photovoltaic systems

This paper presents a control for a three phase five-level neutral clamped inverter (NPC) for grid connected PV system. The maximum power point tracking (MPPT) is capable of extracting maximum power from the PV array connected to each DC link voltage level. The MPPT algorithm is solved by fuzzy logic controller. The fuzzy MPPT is integrated with the inverter so that a DC–DC converter is not needed and the output shows accurate and fast response. A digital PI current control algorithm is used to remain the current injected into the grid sinusoidal and to achieve high dynamic performance with low total harmonic distortion (THD). The validity of the system is verified through MATLAB/Simulink and the results are compared with three phase three-level grid connected NPC inverter in terms of THD.     

Construction of phase diagrams to estimate phase transitions at high pressures: A critical point at the solid liquid transition for benzene

Phase diagrams are an integral part of the estimation of material properties in the case of high temperature and pressure. The pressure-temperature (P-T) phase diagram is used to determine the state of aggregation (solid, liquid, gaseous) of a substance under given conditions. This article presents a method to reveal new states in the phase diagram, including the possibility of the plasma state. Using the empirical data of benzene, a critical pressure beyond solid-liquid equilibrium was estimated. It is highly probable that beyond these pressures, benzene may ionize and exhibit plasma behavior. The method proposed in this work for benzene could also be applied to create a comprehensive phase diagram of Hydrogen at certain pressure and temperature. Because the complex behavior of hydrogen, as well as the constant discovery of new varieties and the creation of many different phases of hydrogen makes it very difficult to construct a realistic phase diagram.     

A new model of phase change process for thermal energy storage

Thermal energy can be converted into mechanical energy through the melting process of a phase change material (PCM). A PCM mixed with an insoluble liquid has higher energy converting efficiency during the whole melting process, where the massive microvacuum formed during the freezing process is filled by the insoluble liquid, which increases utilization of the volume change. The traditional theoretical model of the phase change process is unable to sufficiently describe the mixed PCM; therefore, a new model aimed at analyzing the characteristics of the volumetric change rate, as well as the freezing and melting times of the mixed PCM, is theoretically constructed. In this paper, the effective heat capacity method is used, and the effects of porosity are considered when the PCM is in the solid state. Comparisons of this model with the traditional model are carried out using both simulations and experiments for different pressures and geometric structures. Our results indicate that the introduced model has better accuracy when describing the phase change process of the pure PCM mixed with an insoluble liquid.     

Robust switched fractional controller for performance improvement of single phase active power filter under unbalanced conditions

A novel controller is proposed to regulate the DC-link voltage of a single phase active power filter (SPAPF). The proposed switched fractional controller (SFC) consists of a conventional PI controller, a fractional order PI (FO-PI) controller and a decision maker that switches between them. Commonly, the conventional PI controller is used in regulation loops due to its advantages in steady-state but it is limited in transient state. On the other hand, the FO-PI controller overcomes these drawbacks but it causes dramatic degradation in control performances in steady-state because of the fractional calculus theory and the approximation method used to implement this kind of controller. Thus, the purpose of this paper is to switch to the PI controller in steady-state to obtain the best power quality and to switch to the FO-PI controller when external disturbances are detected to guarantee a fast transient state. To investigate the efficiency and accuracy of the SFC considering all robustness tests, an experimental setup has been established. The results of the SFC fulfill the requirements, confirm its high performances in steady and transient states and demonstrate its feasibility and effectiveness. The experiment results have satisfied the limit specified by the IEEE harmonic standard 519.