Harmonic Load Flow Analysis

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Contents
1. INTRODUCTION – HARMONIC LAOD FLOW ANALYSIS SOFTWARE3
2. POWER SYSTEM HARMONICS4
2.1 Concept of Power System Harmonics4
2.1.1Fourier Series and Harmonics4
2.1.2 Distortion Indices6
2.1.3 Characteristics of Harmonics in Power Systems7
2.2 HARMONIC SOURCES8
2.3 EFFECT OF HARMONICS9
2.3.1 Thermal losses in harmonic environment10
2.3.2 Effects on power system equipment10
2.3.3 Capacitor banks10
2.3.4 Transformers11
2.3.5 Rotating machines11
3. HARMONIC LOAD FLOW ANALYSIS12
3.1 LOAD FLOW ANALYSIS12
3.1.1 Load flow problem formulation12
3.1.2 Backward forward sweep method14
3.2THREE PHASE HARMONIC ANALYSIS17
3.2.1 Components model18
3.2.2 Algorithm18
4. INTERNAL FUNCTIONING OF HARMONIC LOAD FLOW ANALYSIS SOFTWARE21
1. Display and control using Visual C++6.021
2. Running Analysis using C++ language21
4.1CHOICE OF SOFTWARE - VISUAL C++ 6.0 & C++ LANGUAGE21
1.Visual C++ 6.021
2.C++ language22
4.2IMPLEMENTATION OF HARMONIC ANALYSIS SOFTWARE23
4.2.1 The GUI:23
List of classes and their member variable and functions23
The view and usage of GUI visible to user –27
An example of working of GUI and adding elements30
4.2.2 The main background code and its flow of control32
Classes used32
4.3 Program Flow33
4.4 Software testing of a sample system:35
5. Conclusion39
5.Further work/improvement40
6.Bibliography41
Appendix43
List of Equations43

1. INTRODUCTION – HARMONIC LAOD FLOW ANALYSIS SOFTWARE

Power Systems of today are very large, complex interconnected network of various components. Major components of a power system can be subdivided into: a. Generation
b. Transmission and Sub transmission
c. Distribution
Conventional ac electric power systems are designed to operate with sinusoidal voltages and currents. However, nonlinear and electronically switched loads distort steady state ac voltage and current waveforms. It is important to calculate these distortions for safe and reliable operation of the power system. Periodically distorted waveforms can be studied by examining the harmonic components of the waveforms. The text here presents method of 3 – phase harmonic analysis for industrial distribution systems with the aid of a personal computer using the harmonic analysis software. This software uses C++ for analysis and Visual C++ based GUI as front end. It performs following analyses. * Load Flow Analysis

* 3 – Phase Harmonic Analysis
The software allows the user to draw and model a distribution network and input the injected harmonic currents. It performs load flow analysis using backward- forward sweep method. Same method is used for 3- phase harmonic analysis. Finally harmonic voltages and total harmonic distortion (THD) at various buses is calculated. Objective of this project was to build software for designing a 3- phase distribution system and its harmonic load flow analysis. Backward- Forward Sweep method was used due to its efficacy in radial distribution systems. This software works for a non branched network and can be easily extended into a complete radial network. 2. POWER SYSTEM HARMONICS

A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f . . . etc. The harmonics have the property that they are all periodic at the fundamental frequency; therefore the sum of harmonics is also periodic at that frequency. In relation to power systems, harmonics are used to represent the multiple frequencies of voltage and current waveforms. The following sections discuss the concept of power system harmonics, their sources and effects. 2.1 Concept of Power System Harmonics

Nonlinear and switched loads and sources can cause distortion of the nominal sinusoidal current and voltage waveform in an ac power system. In this...
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