Analysis of power system harmonics using singular value decomposition, least square estimation and FFT

The APLC (active power line conditioner) is a type of active power filter that compensates voltage waveform distortion caused by harmonics in power systems. This paper presents a new approach, based on optimization theory, to investigate the determination of locations and sizes of APLCs. The objective is to minimize the new APLC injection currents and the voltage distortion while satisfying the harmonic standard. The test results for an 18-bus distribution system show the applicability of the proposed method.

This work aims to demonstrate the development of a computer code (HPFCODE) that uses the MATLAB GUI to calculate power flow and losses in power systems under the effect of harmonics. After being explained, the programme was tested on two networks, IEEE 6 and IEEE 14. Static Var Compensator (SVC), Thyristor controlled Reactor (TCR), and Unified Power Flow Controller ((UPFC)) were used to calculate the power flow using the Newton-Raphson approach, where the loads are linear and nonlinear, respectively. The findings were truly consistent and demonstrate how higher harmonics affect power losses in electrical networks. We have confirmed the possibility to analyze other nonlinear loads with this computer code HPFCODE generating harmonics in power systems.

Traditional methods to measure power system harmonics employ the power harmonic analyzer or a software package, such as Matlab or others, but they do have certain limitations in the graphical programming environment, applications for remote monitoring and control performance and for multi‐point harmonic measurement. In this paper, a PC‐based virtual instrument (VI) based on Fast Fourier Transform (FFT) to implement a remote multi‐point power system harmonics analysis and monitoring using LabVIEW is proposed. The nearby PC (Server) can collect real‐time waveform data from different multi‐locations and transmit it to remote PCs (Clients) for on line harmonic analysis and monitoring via the Internet. The history of Total Harmonic Distortion (THD) in the waveform signals from remote locations can be also recorded and tracked in the data base. The strategies and guidelines are also developed to enhance teaching and/or learning the basics of operating Internet‐based systems. Experimental results have testified its well performance and remote Web‐based capability. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 17: 241–252, 2009; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20175

A novel approach to compensating for harmonics in power systems is presented. It is a combined system of a shunt passive filter and a small rated series active filter. The compensation principle is described, and some filtering characteristics are discussed in detail. Excellent practicability and validity to compensate for harmonics in power systems are demonstrated experimentally. Although the source harmonic voltage was only 1%, the source harmonic current reached about 10% before the series active filter was started. After it was started, no harmonic current flowed into the shunt passive filter. In addition, no harmonic voltage appeared at the terminals of the shunt passive filter, because the source harmonic voltage was applied to the series active filter. The total loss of the series active filter was less than 40 W. It is concluded that the combined system is far superior in efficiency to conventional shunt active filters. >

Harmonics in a power system caused by highly nonlinear devices degrade its performance. Controlling and reducing such harmonics have been a major concern of power engineers for many years. The power system harmonic analysis is the process of calculating the magnitudes and phases of the fundamental and higher order harmonics of system signals. The frequency domain solution method is one of the major mathematical approaches for such analysis. The paper discusses the frequency domain solution method in the power system harmonic analysis. It identifies harmonic sources and their effects on power system operation. It also discusses computer applications of such method.

The presence of non-linear loads and the increasing number of distributed generation power systems (DGPS) in electrical grids contribute to change the characteristics of voltage and current waveforms in power systems, which differ from pure sinusoidal constant amplitude signals. Under these conditions advanced signal processing techniques are required for accurate measurement of electrical power quantities. The impact of non-linear loads in electrical power systems has been increasing during the last decades. Such electrical loads, which introduce non-sinusoidal current consumption patterns (current harmonics), can be found in rectification front-ends in motor drives, electronic ballasts for discharge lamps, personal computers or electrical appliances. Harmonics in power systems mean the existence of signals, superimposed on the fundamental signal, whose frequencies are integer numbers of the fundamental frequency. The electric utility companies should supply their customers with a supply having a constant frequency equal to the fundamental frequency, 50/60 Hz, and having a constant magnitude. The presence of harmonics in the voltage or current waveform leads to a distorted signal for voltage or current, and the signal becomes non-sinusoidal signal which it should not be. Thus the study of power system harmonics is an important subject for power engineers. The power system harmonics problem is not a new problem; it has been noticed since the establishment of the ac generators, where distorted voltage and current waveforms were observed in the thirtieth of 20th century [2]. Concern for waveform distortion should be shared by all electrical engineers in order to establish the right balance between exercising control by distortion and keeping distortion under control. There is a need for early co-ordination of decisions between the interested parties, in order to achieve acceptable economical solutions and should be discussed between manufacturers, power supply and communication authorities [1]. Electricity supply authorities normally abrogate responsibility on harmonic matters by introducing standards or recommendations for the limitation of voltage harmonic levels at the points of common coupling between consumers.

Due to the proliferation of non-linear modern power electronics, currents and voltages produced by non-linear loads have lead to the deterioration and distortion of the output sine wave forms of the source currents and voltages. These distortions have resulted in the power quality problems. The non-linear load draws reactive power and harmonics from the ac source in the fundamental current. The harmonics in power system caused by non-linear loads such as, arc furnaces, switch mode power supply, fluorescent lamps rectifiers etc all are the main sources of harmonics, as a result of these non-linear loads the supply system lead to overheating of cables and conductors, electromagnetic interference to nearby communication facilities etc. Therefore, as a result of theses harmonics, a traditional passive filters are used to suppressed the integer multiple fundamental frequencies, but due to the passive filter draws back in producing series or parallel impedance with the supply impedance and heavy in sized, its limitations in service becomes an old scheme. The application of shunt active power filter in mitigating these harmonics problems supersedes the used of passive filter. This paper, presents the modeling and simulation of single-phase shunt active power filter controlled with fuzzy logic controller (FLC) to mitigate the harmonics drawn by non-linear loads. The proposed scheme is performed by using MATLAB fuzzy tool box environment. Simulation results obtained by the proposed control algorithm found to be satisfied and within the recommended imposed IEEE 519-1992 harmonic standard limit.

Harmonics are multiples of the fundamental frequency of power system. These harmonics are creating distorted voltages and currents in the power system. Distortion of voltages and currents can affect the power quality. This article covers Harmonics sources in power system. Different Sources of harmonics in power system have been discussed.

With the development of today's era, the power industry has also made great progress, and the electricity market has also risen. The components of power system begin to use nonlinear related components, but the use of non-linear components will inevitably produce harmonics, which will lead to the distortion of current and voltage waveforms to a certain extent, and will pose a great threat to the security of power grid. The harmfulness of harmonics in power system will affect the safety of electrical equipment in power system, so it is the future research direction to design a reasonable and efficient harmonic detection method and filter device so that it can complete the detection task. Starting from the generation and harmfulness of harmonics, this paper summarizes the common methods of harmonic detection in power system in today's power industry, and how to control harmonics, so that it can provide a reference path for the detection of power harmonics and the treatment of harmonics.

In this study, a test signal proposed in the literature for amplitude and phase estimation of harmonics in power systems is utilized. The test signal is applied to the proposed Kalman-based approach under noise conditions of 10 dB, 20 dB, and 40 dB. Performance is evaluated by comparing the obtained estimation results with those reported in the literature. For 10 dB Gaussian noise, the mean squared error (MSE) was 0.006649, and the normalized mean squared error (NMSE) was 0.014542; for 20 dB Gaussian noise, the MSE was 0.000613, and the NMSE was 0.001340; and for 40 dB Gaussian noise, the MSE was 0.000004, and the NMSE was 0.000009. The average computational time across all three cases is 0.06 seconds. For each noise level, the original, noisy, and estimated signals are analyzed in both the time and frequency domains, with visual assessments consistent with the numerical results.

Nowadays, power quality is considered as a major concern that is faced by electrical energy producer, consumers, industries and researchers. Whereas one among the main issues in such concern is the current and voltage harmonics detection, mitigation and compensation. Indeed, the proliferation of harmonics in power system can create serious problems within all levels and their impacts along the whole power system from the production to the end users can lead to critical technical and economic situations. Therefore, their accurate detection in real time is of great importance and interest where many techniques have been proposed for solving such major problem. The work presented in this paper deals with the evaluation of a technique that has been proposed for the estimation of harmonic content in a signal based on iterative computing technique. This technique is based on several keystone parameters, which have major influences on the accuracy of the identification of the different harmonics without the need of a costly computation, and that can be easily implemented and performed in real-time. It is worthy to clarify that the technique under investigation in this paper is the based on the idea of adaptive filtering process called the Variable length Step Size- Least mean squares method (VLSS-LMS), it is basically very sensitive to three main parameters such as the sampling frequency, the step size value and the measurement window. The evaluation of the effects of these parameters have been assessed based on simulation testes of a specific original signal containing harmonics components. The obtained simulation results clearly prove the optimal choices of the aforementioned parameters in ensuring precise estimation of the harmonics content and the reconstruction of the estimated signal with high precision and minimized average error.

Active filtering has now become a mature technology to compensate harmonics in power systems with nonlinear loads. This paper introduces an iterative algorithm to investigate the optimal determination of location of an active filter. The objective function includes minimization of transmission lines losses and total harmonic distortion. The 5 bus IEEE power system is used to evaluate the applicability of the proposed method.

Chapter 16 - Electrical harmonics estimation in power systems using bat algorithm

This paper aims to analyzing and probing the influences of power system harmonics on a differential relay used for distribution transformer protection. The increased use of nonlinear devices in industry, commercial and residential areas can lead to a significant increase the level of harmonic distortion in the power system. This harmonic has the significant effects to the differential protection systems components such as current transformer (CT) and relay. The CT tends to saturate due to the presence of current harmonics in power system, so it will produce magnitude secondary current error and make the differential relay to miss operations. The harmonic distortion effects on the differential protection have been investigated through laboratory test. To determine the CT errors when operates under harmonic condition, the CT has been test with certain level of THDi. The result of this testing was found that with increasing of the THDi, the magnitude of secondary current error increased and differential relay will operate at no fault conditions.

This paper extends the investigation into the bivariate normal distribution (BND) model which has been widely used to study the asymptotic behaviour of the sum of a sufficiently large number of randomly‐varying harmonic phasors (of the same frequency). Although the BND model is effective and applicable to most problems involving harmonic summation, its main drawback resides in the computation time required to extract the probability density function of the harmonic magnitude from the two‐dimensional BND model. This paper proposes a novel approach to the problem by assimilating the generalized Gamma distribution (GGD) model to the marginal distribution (the magnitude) of the BND using the method of moments. The proposed method can accurately estimate the parameters of the GGD model without time‐consuming calculation. A power system containing ten harmonic sources is taken as an example where the comparison of the Monte‐Carlo simulation, the BND model and the GGD model is given and discussed. The comparison shows that the GGD model approximates the BND model very well.