Pulzno gostotno moduliran mikrorazsmernik z aktivnim razklopitvenim tokokrogom

Korošec, Lucijan

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Title:	Pulzno gostotno moduliran mikrorazsmernik z aktivnim razklopitvenim tokokrogom
Authors:	ID Korošec, Lucijan (Author) ID Milanovič, Miro (Mentor) More about this mentor...
Files:	DOK_Korosec_Lucijan_2015.pdf (3,98 MB) MD5: AC103774D068CA48BCB280293C0E4FE2
Language:	Slovenian
Work type:	Dissertation
Typology:	2.08 - Doctoral Dissertation
Organization:	FERI - Faculty of Electrical Engineering and Computer Science
Abstract:	V doktorski disertaciji obravnavamo področje enofaznih razsmerniških pretvornikov za posamezne fotovoltaične module, imenovanih mikrorazsmerniki. Pri teh sistemih vhod predstavlja fotovoltaični vir enosmerne in v delovni točki sistema konstantne moči, izhod pa v obliki lokalnega bremena ali električnega omrežja zahteva odjem z izmenično močjo. Posledično je zaradi nenehne razlike v proizvajani in porabljeni moči zahtevana razklopitev s čim manjšo energijsko posodo – razklopitvenim kondenzatorjem, kar predstavlja največji izziv obravnavane tematike, saj vrednost kapacitivnosti, napetostni nivoji in sama velikost razklopitvenega kondenzatorja določajo velikost, ceno in življenjsko dobo celotnega pretvornika. Hkrati velikost pretvornika oz. uporabljenih komponent določa predvsem stikalna frekvenca delovanja sistema, njeno dvigovanje in s tem zmanjševanje velikosti komponent pa omejujejo stikalne izgube uporabljenih tranzistorjev in diod, ki vodijo v slabši izkoristek pretvorbe energije. Glede na te izzive v doktorski disertaciji podajamo pregled obstoječih struktur mikrorazsmernikov in njihovih delovanj. Na podlagi dvostopenjskega mikrorazsmernika z enosmerno zbiralko (DC-linkom), ki dobro zaobide problem velikosti in življenjske dobe razklopitvenega kondenzatorja, smo predlagali novo strukturo pretvornika. Ta uvaja v konfiguracijo vezja aktivni razklopitveni tokokrog z razklopitvenim kondenzatorjem in visokofrekvenčno izmenično zbiralko (HFAC-link) ter v nasprotju z obstoječo rešitvijo omogoča izvedbo mehkega preklapljanja stikal, posledično pa uporabo visoke stikalne frekvence delovanja pretvornika. Zaradi specifičnega načina delovanja smo pri vodenju predlaganega mikrorazsmernika uporabili pulzno gostotno modulacijo. Vodenje pretvornika smo zaradi kompleksnosti in visoke stikalne frekvence (100 kHz) izvedli na programarljivem polju logičnih vrat (FPGA), samo delovanje predlagane strukture mikrorazsmernika pa smo eksperimentalno preverili.
Keywords:	Mikrorazsmernik, pulzno gostotna modulacija, razklopitveni kondenzator, aktivni razklopitveni tokokrog, visokofrekvenčna izmenična zbiralka.
Place of publishing:	Maribor
Publisher:	[L. Korošec]
Year of publishing:	2015
PID:	20.500.12556/DKUM-55485
UDC:	621.383.51:681.586(043.3)
COBISS.SI-ID:	282658048
NUK URN:	URN:SI:UM:DK:VLE51GEC
Publication date in DKUM:	09.12.2015
Views:	2216
Downloads:	271
Metadata:
Categories:	KTFMB - FERI
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Secondary language

Language:	English
Title:	Pulse Density Modulated Microinverter with Active Decoupling Circuit
Abstract:	This doctoral thesis focuses on single phase inverters for individual photovoltaic modules, also known as microinverters. The input of a microinverter is supplied by the photovoltaic module which is a source of constant DC power. The microinverter can supply a local load connected to its output terminals or inject the current into the utility grid. Alternating power is required at the converter's output in both cases. Due to the difference between the instantaneous input and output power, a decoupling capacitor must be incorporated within the microinverter's circuit. The voltage level and the required capacitance of the decoupling capacitor strongly influence the total size, production cost and lifetime of the converter. Hence, the selection of the decoupling capacitor represents one of the main design challenges. The total size of the microinverter also depends on the operating switching frequency, the increase of which allows for a reduction in the size of passive components within the circuit. Nonetheless, operation with a higher switching frequency leads to increased switching losses in semiconductor devices and consequently lower power conversion efficiency. An overview of existing microinverter structures and their operating principles is provided within this thesis. A two stage microinverter with DC-link provides among the best properties in terms of the size and lifetime of the decoupling capacitor, but suffers from high switching losses when operating at higher switching frequencies. In order to overcome this drawback, a new microinverter is proposed based on a two stage microinverter with DC-link. Its main advantage is in soft switching of the utilised transistors and diodes, which allows the operation at higher switching frequencies. Instead of a DC-link, the proposed converter uses a high frequency alternating link (HFAC-link) in combination with an active decoupling circuit. In order to meet the specific operating requirements a pulse-density modulation technique is utilised. Due to a complex control strategy and high switching frequency (100 kHz) the control is implemented within a field programmable gate array (FPGA). Experimental results confirm proper operation of the proposed microinverter.
Keywords:	Microinverter, Pulse Density Modulation, Decoupling Capacitor, Active Decoupling Circuit, High Frequency AC link.

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