Harmonics In Distribution Systems Research Articles

Implementation of UPQC to Mitigate Voltage Sag, Swell and Harmonics in Distribution System

Abstract available with the full text.

Harmonic Compensation Techniques in Electrical Distribution System- A Review.

Harmonics in the power system is not new issue. This phenomenon has been introduced by technocrat throughout in the history of electrical power system. Maintaining the power quality in a power system is an essential assignment due to increase in wide variety of non-linear loads. The current drawn by such non linear loads are non-sinusoidal and therefore contains harmonics. Therefore, it becomes necessary to compensate these unwanted harmonics for better performance of the system. In this paper, a review of compensations of harmonics in distribution system has been explained.

Economic assessment of non-sinusoidal energy in distorted distribution systems

PurposeThe purpose of this paper is to analyze annual energy expenditure in the presence of non-linear load and substation voltage harmonics in distribution systems. Economic assessment of non-sinusoidal energy is a challenging task that involves complex computations of harmonic load powers and harmonic line losses.Design/methodology/approachThe paper evaluates fundamental and non-sinusoidal components of electrical energy by applying backward/forward sweep technique in distorted distribution systems. This work involves harmonic power computations at the substation by including harmonic losses occurring in various lines of the distribution system.FindingsThe paper found that annual energy expenditure significantly depends upon the non-linear load, supply voltage harmonics and type of tariff structure considered in the distribution system. Impact of individual harmonic orders on the energy billing is also assessed.Originality/valueThe paper concludes that considering harmonic distortions in the distribution system analysis would help electricity regulators formulate adequate pricing structures, which would further generate appropriate economic signals for electricity utility and the consumers.

A New Approach to Compensating Voltage Unbalance by UPQC-Based PAC

This paper proposes a novel algorithm for power angle control (PAC) which aims to simplify the control algorithm and obtain a fast dynamic response. It also extends the capability of PAC to compensate voltage unbalance with or without phase angle jump in a simple way. Using this control strategy, unified power quality conditioner (UPQC) can improve power quality problems such as sag, swell, and unbalances of source voltage, load reactive power and harmonics in distribution systems. The series converter in UPQC is responsible for compensation for voltage-related problems. In PAC method, the series converter also participates in load reactive power compensation which is the superiority of this control strategy. The proposed method uses triangular rules of vector addition/subtraction to determine phase and magnitude of voltage that should be injected by series converter. It reduces the required calculations and hence raises the velocity of compensation. For achieving a better dynamic response, a sliding mode control is used to control DC link voltage instead of conventional PI control. This makes the control algorithm faster and more robust. Simulation results obtained through MATLAB/SIMULINK verify the effectiveness of the proposed method.

A Novel Control Strategy Based Dynamic Voltage Restorer for Compensation of Voltage Harmonics in Distribution System

Power quality is one of the areas that the power sector is worried about. Power quality is the measure of practical system resemblance to ideal system. Voltage quality can be defined as the maintenance of voltage waveform shape close to ideal shape with proper magnitude and frequency. Even a slight change in voltage of the system can cause serious damage to the power system. Sensitive loads cannot adjust for small change in voltage. This paper presents Dynamic Voltage Restorer (DVR) for voltage harmonic suppression along with sag/swell compensation in distribution system. DVR is a voltage source converter which sends compensating signals when operated through switches of voltage source converter. This paper presents a novel control strategy to control DVR to block out the voltage harmonics in distribution system. The models and results are developed using MATLAB/SIMULINK software and comparative analysis of source voltage harmonics and load voltage harmonics during sag/swell compensation was tabulated.

Role of PI/Fuzzy Logic Controlled Transformerless Shunt Hybrid Power Filter using 6-Switch 2-Leg Inverter to Ease Harmonics in Distribution System

Background/Objective: The intention of this paper is to propose a Transformerless Shunt Hybrid Power Filter (TSHPF) using 6-Switch 2-Leg Inverter (SSTL) to enhance the power quality in distribution systems. Methods/Statistical Analysis: The TSHPF comprises of SSTL inverter and passive filter coupled to Point of Common Coupling (PCC). Here SSTL inverter acts as Shunt Active Filter (SAF). The DC bus voltage in SSTL inverter is retained by using PI/Fuzzy controller. To generate switching pulses in inverter linear control method is used. Here a TSHPF incorporated with fuzzy controller is developed and comparative analysis is made w.r.t conventional PI controller. Findings: The proposed system is simulated in MATLAB/ SIMULINK for both control strategies. Simulation results shows that compared to PI, by including fuzzy controller the total harmonic distortion is reduced from 8.64% to 3.40%. Improvement: The PI controller is not feasible because explicit mathematical model is needed. Hence, fuzzy controller based TSHPF is much efficient for enhancing the power quality.

ARTIFICIAL NEURAL NETWORK CONTROLLER BASED DISTRIBUTION STATIC COMPENSATOR FOR VOLTAGE SAG MITIGATION

Switching of loads, capacitors, along with the proliferation of power electronics equipment, non-linear loads in industrial, commercial and domestic applications have lead to power quality issues in the distribution system. Power quality issues such as voltage sag, voltage swell and harmonics, which are certainly major concerning issues in the present era. These issues can lead to failure or malfunction of the many sensitive loads connected to the distribution system, thus incurring a high cost for end users. Power quality problems are solved by advanced custom power devices. This study presents how the custom power device Distribution Static Compensator (D-STATCOM) is used to mitigate voltage sag and voltage harmonics in distribution system. Artificial Neural Network (ANN) controller based D-STATCOM is simulated in MATLAB-SIMULINK environment. Prototype model for single phase D-STATCOM is developed to verify the results. The simulation and hardware results show clearly the performance of the D-STATCOM in mitigating voltage sag and voltage harmonics in distribution system.

Calculations of diversified harmonic currents in electric distribution systems

A comprehensive analysis of the characteristics of distribution-system harmonics is provided. This analysis leads to the formulation of harmonic diversity factor tables. These tables give a reliable estimate of harmonic currents in distribution feeders and enable the engineers to determine the amount of background distortion of the voltage waveform. The use of the proposed tables will ease the computational difficulties in performing distribution system harmonic studies. Both deterministic and probabilistic methods were integrated in the conducted analysis in this paper to generate the diversity factor tables. The proposed method and the analysis results are presented in detail.

A Mini-Project in Power Distribution System Harmonics Analysis and Effect of Harmonic Filter Installation

This paper presents a PC-based mini-project in power distribution system harmonics simulation for undergraduate students. The developed software may be used as a tool to assist the student in the analysis and design of a typical distribution system by taking into account the significant levels of harmonics. The paper also demonstrates the use of the harmonics filter which can identify the harmonics effect before and after the filter installation.

Application of algorithms and artificial-intelligence approach for locating multiple harmonics in distribution systems

A new method is proposed for locating multiple harmonic sources in distribution systems. The proposed method first determines the proper locations for metering measurement using fuzzy clustering. Next, an artificial neural network based on the back-propagation approach is used to identify the most likely location for multiple harmonic sources. A set of systematic algorithmic steps is developed until all harmonic locations are identified. The simulation results for an 18-busbar system show that the proposed method is very efficient in locating the multiple harmonics in a distribution system.

配電糸統高調波の測定解析と高調波拡大現象の抑制手法

配電糸統高調波の測定解析と高調波拡大現象の抑制手法

Unique aspects of distribution system harmonics due to high impedance ground faults

The effects of the many sources of harmonics which occur on distribution systems are discussed and contrasted with the single source of harmonics from a high-impedance ground fault. Field data are presented which show the complexity of modeling the ambient harmonics and the simplicity of the change in the phasor value of the third harmonic which occurs due to a high-impedance ground fault. This phasor change is shown to be unique and predictable and hence suitable for use in detecting these faults. It is shown that variations in ambient harmonics may be greater than the change due to a high-impedance ground fault and must be considered in the fault detection system. Calculations of fault current harmonics are simpler than those for the ambient harmonics. >

Measurement of the harmonic characteristics of radial distribution systems

This article presents the results of a project involving the measurement of distribution system harmonics on nominal 13.2 kV radial distribution systems. Measurements were taken on seven different distribution systems during the course of the project. The harmonics present on these systems were due to distributed harmonic sources. The measurement system and the analysis of the data from the measurements are presented. The analysis shows that similar harmonic patterns exist on these systems.

Distribution System Harmonics: Controls for Large Power Converters

Because of the anticipated applicaton of large ac/dc power converters on utility distribution systems, the Electric Power Research Institute (EPRI) funded Project RP1024-1 to study distribution system surge and harmonic characteristics. The harmonics produced by large converters depends on converter type (line-or self-commutated), converter pulse number, thyristor firing angle controls, commutation angles, voltage regulation techniques, voltage unbalance, and?very importantly?network impedance frequency response. Of particular significance is the fact that a great deal of effort is still required to determine tolerable levels of harmonic voltages and currents on distribution systems. Harmonic controls for power converters-important because of their effect on converter cost and efficiency-are now specified on the basis of engineering data which need to be enhanced by further testing and analysis. In the face of observable and ever-increasing background levels of distribution system harmonics, more precise anticipation of future concerns is required. Test methods and instrumentation need to be standardized to ensure conformance to yet-to- be-determined permissible harmonic limits. This paper discusses line-and self-commutated power converters and techniques for controlling the harmonics associated with them and presents the principal results of EPRI Project RP1024-1.

Measuring Voltage and Current Harmonics on Distribution Systems

This paper describes the instrumentation systems and test methodologies used for simultaneously measuring voltage and current harmonic magnitudes at the harmonic source and remote-feeder locations on each of two distribution systems. Results of two sets of field tests are presented. Recommendations are offered for measuring distribution system harmonics.