Modeling and design of the LLC resonant converter used in solar array simulator

An LLC resonant converter has been used to provide the electrical characteristics of solar arrays. In this paper, its small signal model is derived based on the extended describing function concept. The corresponding frequency response can be easily obtained from IsSpice simulation of the equivalent circuit model. Furthermore, a closed-loop compensation controller is designed according to the derived small-signal model. The experimental measurements have really proved that the stable and fast transient response can be achieved in the system. The system output voltage and current can be adjusted simultaneously to match the electrical characteristics of photovoltaic output.

I. Introduction

Theoretically, the output impedance of resonant converters can be regulated from zero to infinite by applying frequency modulation control [1]. Because this characteristic can match that of photovoltaic output without shunt or serial resistors, resonant converters are more applicable than the traditional PWM dc-dc converters for the solar array simulator (SAS) applications.