Grid Connected Photovoltaic System Using Resonant Converter

Abstract

The high penetration of solar energy systems has driven researchers worldwide to direct their efforts towards improving the efficiency of these systems. This thesis is concerned with double stage grid-connected photovoltaic (PV) systems where the DC-DC converter is a very effective component. Traditional pulse width modulated (PWM) DC-DC converters suffer from the drawbacks of hard switching which degrades the efficiency because of the increased switching losses. Also hard switching limits the range of operating frequency which results in low power density. Resonant DC-DC converters have been introduced as an attempt to mitigate the limitations found in traditional PWM DC-DC converters. These converters offer soft switching mechanisms like zero voltage switching (ZVS) and zero current switching (ZCS) which significantly reduce the switching losses and consequently increase the efficiency. In addition, soft switching enables operation at very high frequencies increasing the power density of the converter. A LLC resonant DC-DC converter is proposed to boost the DC voltage output of the PV array and perform the task of maximum power point tracking (MPPT). This converter has the advantages of wide input and output regulation capability, high boost ratio, high efficiency and high power density. Furthermore, the power density can be enhanced by the utilization of the magnetizing and leakage inductances of the transformer as parts of the resonant tank. The incremental conductance MPPT is applied using PI controller for its simplicity and decent accuracy. The performance of the MPPT controller is enhanced through the application of ant colony