Thesis PARTIAL POWER DC-DC CONVERTERS FOR TWO STAGE PHOTOVOLTAIC ENERGY CONVERSION SYSTEMS
Date
2018
Authors
ZAPATA AMORES, JAIME WLADIMIR
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Abstract
Las con guraciones fotovoltaicas (PV) tradicionales de dos etapas han incrementadosu popularidad debido al desacoplamiento entre el voltaje en el enlacedcy el voltaje a nivel de modulos PV, agregando exibilidad para extender elrango de operacion al realizar el algoritmo de seguimiento de maximo punto depotencia (MPPT). Sin embargo, el convertidor dc-dc adicional incrementa elnumero de etapas de conversion de energa, y por ende las perdidas en la etapade conversion. El concepto de convertidores de potencia parcial (PPC), el cualesta enfocado en reducir la cantidad de potencia procesada en la etapa-dc, reduceesta cantidad de perdidas. Sin embargo, el tipo de topologa, la cantidadde potencia procesada y el rango de operacion pueden variar de manera signi -cante dependiendo del tipo de aplicacion PV. Ademas, el tipo de funcionamientode la etapa-dc va a diferir entre operar como etapa de elevacion, en caso de unmodulo PV, o de reduccion cuando el sistema tiene un varios modulos conectadosen serie. Esta tesis provee un analisis de las posibles soluciones pararealizar las con guraciones PPC, ademas la aplicacion PV mas adecuada segunla con guracion PPC. Para las pruebas se han dise~nado tres con guracionesPPC, considerando las mas interesante para aplicaciones practicas. Los resultadosexperimentales muestran que los PPC incrementan considerablemente lae ciencia global del sistema, aun cuando el convertidor dc-dc tiene una bajae ciencia. Otras ventajas al manejar una potencia menor, es la reduccion deltama~no del convertidor sin perder desempe~no del sistema.
Two-stage photovoltaic (PV) con gurations (for microinverters, string or multistringinverters) have become increasingly popular due to the decoupling betweenthe inverter dc-link voltage and the PV voltage, adding exibility toextend the MPPT range. However, the additional dc-dc converter increases thecomponent count, reduces the volume and power converter losses. The conceptof partial power converters (PPC), which reduces the amount of power handledby the dc-stage can mitigate this eect. However, the type of topology, itspower and voltage rating, eciency, and operating range can vary signi cantlydepending on the type of PV application and scale. Furthermore, the type offunction of the dc-dc stage will also dier depending on the PV application.From boosting with a high step-up ratio for one module in a microinverter, to abuck mode for larger PV strings when using modern 1500V isolation modules.This thesis provides an analysis of the possible combinations of connectionsand corresponding applications based on the scale of the PV system. The threemost suitable solutions for practical PV systems are further elaborated, includingsimulations and experimental validation. Experimental results show thatthe PPC greatly improves the overall PV system eciency, even when the ef- ciency of the isolated dc-dc converter is low. An added bene t is that thedc-dc stage power rating achieved are only a fraction of the PV system, reducingsize and increasing power density of the power converter without aectingsystem performance.
Two-stage photovoltaic (PV) con gurations (for microinverters, string or multistringinverters) have become increasingly popular due to the decoupling betweenthe inverter dc-link voltage and the PV voltage, adding exibility toextend the MPPT range. However, the additional dc-dc converter increases thecomponent count, reduces the volume and power converter losses. The conceptof partial power converters (PPC), which reduces the amount of power handledby the dc-stage can mitigate this eect. However, the type of topology, itspower and voltage rating, eciency, and operating range can vary signi cantlydepending on the type of PV application and scale. Furthermore, the type offunction of the dc-dc stage will also dier depending on the PV application.From boosting with a high step-up ratio for one module in a microinverter, to abuck mode for larger PV strings when using modern 1500V isolation modules.This thesis provides an analysis of the possible combinations of connectionsand corresponding applications based on the scale of the PV system. The threemost suitable solutions for practical PV systems are further elaborated, includingsimulations and experimental validation. Experimental results show thatthe PPC greatly improves the overall PV system eciency, even when the ef- ciency of the isolated dc-dc converter is low. An added bene t is that thedc-dc stage power rating achieved are only a fraction of the PV system, reducingsize and increasing power density of the power converter without aectingsystem performance.
Description
Catalogado desde la version PDF de la tesis.
Keywords
CONVERTIDORES DC-DC , CONVERTIDORES DE POTENCIA PARCIAL , ENERGIA SOLAR FOTOVOLTAICA
