13841

12579

كارشناسي ارشد

قدرت

اصفهان: دانشگاه صنعتي اصفهان، دانشكده برق و كامپيوتر

۱۳۹۷

هشت، ۸۷ص.: مصور، جدول، نمودار

حميدرضا كارشناس

احمدرضا تابش، مسعود حاجيان

1397/06/25

كتابنامه

برق و كامپيوتر

مهندسي برق و كامپيوتر

ID12579

Analysis of Series Connection Issues of High Power SemiconductorSwitches and Active Voltage Control Method for Voltage Balancing Mohammad Hossein Zoofaghari mh zoofaghari@ec iut ac ir June 12 2018 Department of Electrical and Computer Engineering Degree M Sc Language Farsi Dr Hamid Reza Karshenas karshen@cc iut ac irAbstractThis thesis is concerned with series connection issues of IGBTs and methods of voltage balancing activevoltage control in particular The wide use of high voltage converters in power electronics applications suchas high power traction and industrial drives high voltage dc transmission systems HVDC and flexible actransmission systems FACTS in recent years calls for high voltage power semiconductor switches Insulatedgate bipolar transistor IGBT as a high power semiconductor switch with attractive features are increasinglybeing used in the mentioned applications However due to some technological issues the maximum voltageblocking capability of commercially available IGBTs is 6 5kV Higher voltage ratings for switches in highvoltage converters can be achieved by connecting IGBTs in series The main problem with the seriesconnection of semiconductor switches is unbalanced static and dynamic voltage sharing Static and dynamicvoltage sharing are respectively defined as equal voltage sharing between series connected switches in off state and in switching transients turn off and turn on Unequal voltage sharing can damage the overstressedswitch or reduce its lifetime that can in turn cause failure or make the system less reliable Static voltage sharingcan be achieved easily however there are more difficulties with dynamic voltage balancement Spread indevice parameters and external circuit conditions are two main causes of voltage unbalancement Properselection of devices and symmetrical design reduce the unequal voltage sharing However near ideal dynamicvoltage sharing can only be attained by special methods and extra circuitry Snubbers active voltage clampingand active gate control are three main methods for mitigating voltage sharing Some parameters such as voltageunbalancement mitigation degree effective operation region switching and circuit losses scalability reliability complexity and cost are among the most important criteria for voltage balancing method selection In this thesis issues challenges and practical considerations of series connection of IGBTs are discussed andinvestigated Voltage balancing methods are also introduced and a comparison of them is made Active voltagecontrol AVC as a closed loop control by a high degree of unbalancement mitigation introduced and an AVC based gate drive designed and implemented In this method in the simplest way the collector emitter voltageof IGBT is compared with a reference the error passes through a proportional controller and after currentamplification is applied to IGBT gate resistor In order to improve AVC performance two extra feedbacks gate emitter voltage and collector emitter derivative are added to form a cascaded active voltage control CAVC method Effect of different parameters on AVC performance to control the voltage of a single IGBTand then to resolve voltage unbalancement of two series connected IGBTs is discussed and verified usingimplementation results KeywordsIGBTs series connection static voltage sharing dynamic voltage sharing active voltagecontrol AVC power semiconductor switch

حميدرضا كارشناس

احمدرضا تابش، مسعود حاجيان