# Active Filters Essay

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Design and Simulation of Harmonic Filters Using MATLAB® Software
Prof. Dr. Suhail. A. Qureshi, Ahmed Hassan, Azeem Talib U.E.T Lahore Pakistan ABSTRACT
Calculations are a major part of design process in all aspects of engineering applications. This la borious and time comsuming process can be made really easy by the aid of a high level engineering software like MATLAB ®. This paper deals with the scope and flexibility of MATLAB ® for: 1. Calculation of design parameters for L -C components of different branc hes of a harmonic filter. Graphical analysis of Harmonic Pollution and different Harmonic components. Verification of design using SIMULINK ® and Power System Toolbox before implementation to check any design error that might cause undesireable results. superposition. Harmonic order or harmonic number is a reference to the frequency of the harmonic component e.g 3 rd order harmonic component refers to a harmonic component h aving frequncy 3 times that of fundamental i.e. for a 5 0 Hz supply 3rd order component is of 3x50=150Hz. [1] Generally the sum of even harmonics is less than 1% of fundamental component thus t hey are not considered also 3 rd, 5 th and 7 th order harmonics constitute about 97% of harmonic Thus it is most econom ically suitable to design harmonic filters for these components as these can reduce the pollution level well below the desired limit and being economically justified .[2] 2.1

2. 3.

CAUSES OF HARMONICS

1.

INTRODUCTION

Recent advancements in the field of electronic computing has shown its effects in every aspect of life. Use of computers for Desi gn and Analysis has reduced the time, energy and resources requi red to be spent using conventional methods invol ving manual calculations. Comput er aided design and analysis has another edge over orthodox means; we can easily verify the design to catch any errors in the design process. Thus a powerful computer soft ware like MATLAB ® can greatly reduce the time and effort spent on the calculations required for the design process.Using Graphical User Interface (GUI) we can develop a computer program capable of design and graphically analyze the given electrical parameters from the point of application of filter. We can also verify the design by using SIMULINK ® and Power System Toolbox to tell for any short comings in the design.

Industrial electronic devices and non linear loads are the major cause of harmonic generation. As the current drawn from the supply no longer remains sinusoidal thus the resultant waveform is made up of a number of different waveforms of different frequencies .[3] 2.2 EFFECTS OF HARMONICS

Harmonics are a major cause of power supply pollution lowering the power factor and increasing electrical losses. This results in premature equipment failure and higher rating requirement for equipment .[4] 2.3 HARMONIC FI LTERS

A harmonic filter is a device used to ‘filter o ut’ components of different harmon ic order from reaching and harming the load thus the name ‘harmonic filter’. 2.4 APPLICATION OF HARMONIC FILTERS

2.

HARMONICS AND HARMONIC ORDER

Harmonics are the odd integral multiples of fundamental frequency resulting in the distortion of supply waveform due to interferance by

Harmonic Filters are applied at different points where power pollution due to harmonics is observed abo ve the desireable limi ts as recommended by IEE 519 standards.[5] These are used in parallel to load thus providing a bypass low impedance path for the flow of

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Harmonic currents of sp ecific frequency or harmonic number. Thus a separate harmonic filter branc h is required for each harmoni c order to be removed. Thus a 3 branch filter might be used to filter out 3 rd, 5th and 7 th harmonic component. [5] 3. HARMONIC FILTERS CAPACITOR BANKS AND

3.3 HARMONIC ANALYZER A harmonic analyzer is used to obtain data in terms of electrical parameters for any point we are interested in for the application of harmonic