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چكيده انگليسي :

Design of Harmonic Filters Considering Power Grid Fateme Zare fateme zare@ec iut ac ir August 1 2018 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Prof Mehdi Moallem moallem@cc iut ac ir Abstract Increment of using nonlinear loads in power grids has cause to intensify harmonics in these systems Thedispersion of loads with high distortion rates can cause different issues in low voltage grids For instance the amplitudeof third order harmonics is more than 80 percent in LED lamps As well as these kinds of lamps the other loads in thedistribution system such as low power lamps TVs monitors printers and so forth also have high percentage of harmoniccurrents Harmonics in power grids can damage other loads and grid equipment and also increase energy losses in network For example they affect transformers motors cables measurement protection devices and so forth Harmonic Distortionalso lead to their improper performance and reduce their lifespan besides increasing losses In addition they occupy the ca pacity of transmission lines and transformers and subsequently increase need for investment in power systems The domainof current harmonics in the distribution system is third order harmonic which mostly exhibits common electrical angle on allthree phases Thus this frequency component from the three phases will be added up and flow through the neutral wire oftransformers Therefore the amplitude of neutral wire current is often high in these transformers In some measurements theamplitude of neutral wire current is higher than three phases current Based on mentioned points it is necessary to considerproper solutions to reduce negative effects of this issue In this thesis after studying the effects of harmonics on differentequipments of power grid such as transformers induction motors capacitor banks and etc different methods for designingvarious passive filters such as high pass filters and C type filters will be investigated Forthermore international standardson designing passive filters especially selection methods of their components will be reviewed Thence anumber of com mon loads and their harmonics in power grids will be analyzed In addition voltage and current harmonics in distributiontransformers will be studied in order to investigate the overall behavior of loads One of the most common methods forcompensating current harmonics is designing of passive filters however using these kinds of filters in low voltage gridshave some challenges In the following section the challenges of designing these filters will be reviewed and some practi cal solutions will be presented Afterward the effects of mentioned solutions on frequency response of passive filters willbe discussed Then a brief review of utilizing the earth transformer as one of the third order harmonic current reductionmethods will be considered and possible changes on frequency response curve will be studied At the end designing andmanufacturing of a harmonic filter by focusing on compensating current harmonics will be discussed Key Words Current Harmonics Distribution System Grounding Transformer Passive Filter PowerQuality Zero Sequense

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طراحي فيلترهاي هارمونيكي با در نظر گرفتن شبكه

ترانسفورمر زمين , توالي صفر , سيستم توزيع , فيلتر پسيو , كيفيت توان , هارمونيك‌هاي جريان