三相三线制有源电力滤波器谐波检测方法

针对三相三线制有源电力滤波器(Active Power Filter,APF)中的谐波检测,研究了基于瞬时无功理论的谐波电流快速检测算法,结合谐波检测过程中出现的频率混叠现象而搭建的二阶巴特沃斯低通滤波器,共同实现了有源电力滤波器高精度的谐波检测功能.实验结果验证了方法的正确性和可靠性,对于提高APF的补偿性能有很大的帮助.     

基于DSP的一种三相电路谐波电流检测算法

为能用数字信号处理器(DSP)实现三相电路的谐波电流检测,从基于瞬时无功理论的一种谐波电流检测方法出发,分别讨论了三相电流中谐波正序和谐波负序分量检测的数字方法,由此得出了一种实时的谐波电流检测算法.该算法能准确地检测出三相电流中的谐波正序和谐波负序分量.当有源电力滤波器(APF)等装置的谐波电流检测电路采用该算法时,可根据需要适时调整DSP程序来形成不同的参考电流,以便更好地满足APF的不同补偿要求.仿真和实验研究结果表明了该算法的有效性和可行性.     

一种单相软件锁相方法

在新能源并网发电、FACTS设备控制等应用中,均需要准确检测电网相位,鉴于硬件锁相环灵活性较差,而常规软件锁相环需要对三相信号同步采集,软硬件要求更高。本文提出一种软件单相软件锁相方法,通过周期积分的方法完成二次以上谐波滤除,还可用于提取各次谐波幅值。本文介绍了软硬件实现方法,实验验证了结果的正确性。     

电气化铁路产生的谐波对电网电能质量的影响

近些年来,随着经济的发展,电气化铁路在中国取得了巨大的发展。电气化铁路运行时,将产生三相不平衡的谐波电流和负序电流注入到系统,造成电网电压波形畸变、系统功率因素降低等问题,对电力系统安全、稳定和经济的运行带来严重的影响。本文分析了电气化铁路运行产生谐波的原因,提出解决措施,为改善电网电能质量提供了依据。     

三相桥式整流电路谐波电流检测分析与仿真

本文针对电网中最典型的谐波源——三相桥式整流电路,研究基于瞬时无功功率理论的谐波电流检测方法。利用Matlab/Simulink仿真软件,搭建谐波电流检测的仿真模型,进行仿真分析。通过观察得到的仿真波形,验证＂ip-iq＂法在谐波电流检测中的实际效果,从而为治理电网谐波,进行无功补偿,提供简便的分析手段。     

基于场强法的高压线路谐波检测仪的研究与设计

为了对高压输电线路电压谐波含量进行直接测量,及时了解输电线路谐波情况,本文提出了一种基于场强法测量高压线路电压谐波信号的新方法,克服了传统测量方法不能获得高压线路电压谐波信号问题。通过建立场强法获得电压信号的数学模型,并从理论上证明了其正确性;同时设计了谐波检测仪实际测量电路,包括数据采集器和数据接收器,二者之间通过无线发送数据,解决了高低压隔离问题,高压输电线路谐波检测仪可以方便地检测出高压线路上电压的谐波含量。     

电气化铁路的谐波电能计量技术研究

分析了电气化铁路对电力系统电压电流信号测量和电能计量的影响,建立了针对电气化铁路电能计量的基于离散傅里叶变换的非正弦信号电能计量算法,给出了算法模型、实现机理和依据谐波有功功率判据谐波潮流的方法,利用MATLAB对电气化铁路的谐波电能计量方法进行了仿真实验,在此基础上研制的三相多功能谐波电能表的有功电能计量准确度达到0.2 S,谐波测量准确度满足我国A类谐波测量仪器的要求,符合我国现行电网运行需要.     

关于电力谐波影响的几个问题

由于电力谐波及其功率产生和传播的机理不同于基波 ,因此它对电力网中各类设备和元件也起到不同于基波的作用。其中谐波对计量的影响问题应特别引起供用电部门的重视。1　谐波功率对电能计量的影响我们知道 ,谐波功率是由高次谐波(即其频率为 5 0Hz基波的整数倍 )电流和电压而形成 ,而谐波电压与电流的出现主要是由基波的正弦波形畸变引起 ,即由于近年来大量出现的整流、换流装置 ,例如变频设备、不间断电源、直流电源、电弧设备等而产生的。谐波功率分两部分 :一部分为谐波有功 ,另一部分为谐波无功。对计量的影响主要是指这两部分而言。1…     

虚拟仪器技术在谐波检测系统中的应用研究

指出了电力系统中谐波问题的严重性,并就常见的电力系统谐波的分析方法及优缺点进行了概括。重点阐述了采用傅里叶变换的方法对谐波进行检测和分析的原理,对虚拟仪器技术的特点和优点并与传统仪器分析技术进行了初步对比。最后,给出了基于虚拟仪器技术的电力系统谐波检测和分析系统的软、硬件组成,并简要分析了该系统的运行结果。     

基于随机子空间方法的光伏变流器模态识别和分析

光伏大量并网给电网带来大量谐波谐振问题。针对光伏变流器产生的谐振问题,建立了包含光伏变流器和电网等值阻抗的联合模型。推导了含有光伏变流器阻抗和电网阻抗的s域模型,应用反拉普拉斯变换得到的光伏输出电流不仅含有电压频率分量,还含有光伏阻抗的谐振分量。应用随机子空间方法分析光伏并网点和电流含有的模态分量,对照两者模态的区别,提取出光伏变流器阻抗模态。最后,通过仿真和实测数据分析验证了该方法的有效性。     

Frequency and fundamental signal measurement algorithms for distributed control and protection applications

Increasing penetration of distributed generation within electricity networks leads to the requirement for cheap, integrated, protection and control systems. To minimise cost, algorithms for the measurement of AC voltage and current waveforms can be implemented on a single microcontroller, which also carries out other protection and control tasks, including communication and data logging. This limits the frame rate of the major algorithms, although analogue to digital converters (ADCs) can be oversampled using peripheral control processors on suitable microcontrollers. Measurement algorithms also have to be tolerant of poor power quality, which may arise within grid-connected or islanded (e.g. emergency, battlefield or marine) power system scenarios. This study presents a 'Clarke-FLL hybrid' architecture, which combines a three-phase Clarke transformation measurement with a frequency-locked loop (FLL). This hybrid contains suitable algorithms for the measurement of frequency, amplitude and phase within dynamic three-phase AC power systems. The Clarke-FLL hybrid is shown to be robust and accurate, with harmonic content up to and above 28% total harmonic distortion (THD), and with the major algorithms executing at only 500 samples per second. This is achieved by careful optimisation and cascaded use of exact-time averaging techniques, which prove to be useful at all stages of the measurements: from DC bias removal through low-sample-rate Fourier analysis to sub-harmonic ripple removal. Platform-independent algorithms for three-phase nodal power flow analysis are benchmarked on three processors, including the Infineon TC1796 microcontroller, on which only 10% of the 2000 mus frame time is required, leaving the remainder free for other algorithms.     

Modeling of Eddy-Current Loss of Electrical Machines and Transformers Operated by Pulsewidth-Modulated Inverters

Pulsewidth-modulated (PWM) inverters are used more and more to operate electrical machines and to interface renewable energy systems with the utility grid. However, there are abundant high-frequency harmonics in the output voltage of a PWM inverter, which increase the iron losses and result in derating of the machine or transformer connected to them. Predicting the iron losses caused by the PWM supply is critical for the design of electrical machines and transformers operated by PWM inverters. These losses are primarily attributed to eddy-current loss caused by the PWM supply. In this paper, after analyzing the harmonic components of PWM voltage, we derive the effects of different parameters of PWM switching on the eddy-current loss. We compare the iron losses modeled with the proposed analytical methods on a three-phase transformer, a dc motor, and an induction motor with the results of time-stepping finite-element analysis and experiments. We provide detailed equations for the prediction of iron losses. These equations can be directly applied in the design and control of PWM converters and electric motors to improve energy efficiency in electrical machines and transformers operated from PWM converters.      

有源电力滤波器半矢量预测控制策略研究

针对经典模型预测电流控制算法电压矢量选择范围有限、电流跟踪精度不高的问题,提出改进型模型预测电压控制算法。利用滚动寻优得到较优电压矢量,再利用较优电压矢量和零矢量各作用T_s/2得到半幅值矢量,根据较优电压矢量和半幅值矢量的评价函数选择最优电压矢量。每个周期仅增加一个电压矢量,能有效减小预测电压矢量和实际电压矢量之间的误差,实现对谐波电流的准确跟踪,提高有源电力滤波器的补偿性能。仿真结果表明,所提出的改进型模型预测电压控制算法与经典模型预测电流控制算法相比,补偿电流对参考电流的跟踪更加准确,经补偿后并网电流中的谐波含量由4.86%下降到3.32%,且在稳态和动态情况下都能实现单位功率因数并网。     

谐波与间谐波对电能计量误差影响研究

谐波和间谐波是电力系统的常见干扰,定性、定量评价谐波、间谐波对电能表计量误差的影响,对于完善电能表设计、检测体系具有重要的意义。该文从R46电能表国际建议的相关要求出发,首先定性研究谐波与间谐波对电能计量误差的影响,分析R46国际建议对谐波与间谐波测试信号波形参数的要求;然后提出基于直接数字频率合成的间谐波测试信号生成方案;最后根据R46国际建议的要求,开展谐波和间谐波的电能表计量误差影响实验。实验结果表明:按照R46国际建议设计的电能表能够较好地克服谐波和间谐波对计量误差的影响。     

Harmonics and voltage stability analysis in power systems including thyristor-controlled reactor

In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of significant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious harmonic distortions in transmission and distribution systems. In this paper, harmonic generation of a static VAR compensator with thyristor-controlled reactor and effects of the harmonics on steady-state voltage stability are examined for various operational conditions.     

High-efficient three-phase on-line UPS by using T-source inverter with third harmonic injected maximum constant boost PWM control

This paper presents the analysis of three-phase on-line uninterruptible power supply (UPS) by employing T-source inverter (TSI) with third harmonic injected maximum constant boost PWM control and the results are compared with traditional UPS. Traditional UPS consists of step-up transformer or DC–DC booster along with voltage source inverter which decreases the efficiency and increases energy conversion cost. The proposed three-phase UPS using TSI has high-voltage boost capability through shoot-through zero state which is not present in traditional voltage source inverter (VSI) and current source inverter. This proposed UPS with TSI increases the efficiency with fewer components, reduces the harmonics, increases the voltage gain, and reduces the voltage stress. The performance of three-phase on-line UPS based on TSI is analyzed and evaluated in MATLAB/SIMULINK software and the results are compared with Z-source inverter-fed UPS and VSI-fed UPS. Experimental results are presented for the validation of the simulation and theoretical analysis.     

Intelligent controlled shunt active power filter for voltage and current harmonic compensation in microgrid system

An integrated microgrid with a novel shunt active power filter (APF) using Elman neural network (ENN) is proposed in this study. The microgrid consists of a storage system, a photovoltaic (PV) system, the shunt APF, a linear load, and a nonlinear load. Moreover, the master/slave control algorithm is adopted in the microgrid. The storage system, which is considered as the master unit, is adopted to control the active and reactive power outputs (P/Q control) in grid-connected mode and the voltage and frequency of the microgrid (V/f control) in islanded mode. Furthermore, the PV system is considered as the slave unit to implement P/Q control in both grid-connected and islanded modes. In addition, the proposed shunt APF possesses dual functions of voltage and current harmonic compensation for microgrid under voltage harmonic propagation and nonlinear load to reduce the voltage and current total harmonic distortions (THD) effectively. Additionally, an ENN controller is adopted in the proposed shunt APF to improve the transient and steady-state responses of DC-link voltage during the switching between the grid-connected mode and islanded mode. Finally, some simulation results are provided to verify the feasibility and the effectiveness of the integrated microgrid with the intelligent controlled shunt APF.     

基于PSCAD的双馈感应式风力发电系统低压穿越能力仿真研究

在电网故障条件下,风电并网导则要求风电发电机具备低压穿越能力。为了保护发电机及其变流器,DFIG需要采用Crowbar保护电路为转子过电流提供旁路通道,同时抑制直流母线过电压。本文在PSCAD平台下搭建了2MW双馈感应式风力发电系统,并对有无Crowbar电路的DFIG在三相短路条件下进行了仿真。结果表明：具备Crowbar电路的DFIG有较好的暂态特性,并且具各较强的低电压穿越能力。     

煤矿供电系统中谐波的危害及抑制

供配电系统中谐波的危害已经广为人知,本文就煤矿供配电系统中谐波的成因与危害做了简要探讨,并提出了一些针对性的抑制措施。     

Improving the performance of hysteresis direct torque control of IPMSM using active filter topology

This paper describes an active filter topology to improve the performance of hysteresis direct torque control (HDTC) of interior permanent magnet synchronous motor (IPMSM). The filter topology consists of an active filter and two RLC filters, and is connected to the main power circuit through a 1:1 transformer. The active filter is characterized by detecting the harmonics in the motor phase voltages and injecting equivalent harmonic voltages to produce almost sinusoidal voltage waveform to the motor terminals. The active filter uses hysteresis voltage controller while the motor main circuit uses hysteresis direct torque control. The simulation results of this combined control structure show considerable torque ripple reduction in the steady state range and adequate dynamic torque performance as well as considerable harmonic voltage and EMI noise reduction.