Modeling and Voltage Control of Bidirectional Resonant DC/DC Converter for Application in Marine Power Systems

Abstract

DC/DC converters have gained popularity in a number of industrial applications like electric vehicles or marine power systems, due to their high efficiency and power density levels. Pulse width modulation (PWM) and resonant converters are two main types of the DC/DC converters. Thereby, the resonant converters happen to be the preferred technology in the design of modern marine power systems since these converters are more suitable for the high and middle voltage DC applications. The resonant converters are, however, highly nonlinear systems, which limits the use of linear control methods. In this study, we propose a comprehensive analysis, modeling and control concept of a DC/DC resonant converter in marine power systems. First, a mathematical model of the DC/DC resonant converter in the so-called CLLC topology is derived based on the generalized state-space averaging method. The model is used to design a dual-loop voltage control, which aims to regulate the voltage level at the low-voltage DC bus of the resonant converter. The dual-loop voltage control consists of the primal linear controller, which directly regulates the voltage and the reference generator, which dynamically modifies the voltage reference of the primal controller. The major advantage of the suggested control concept is the improved performance of the simple controller without the need to substitute it as well as the possibility to realize, if required, a multi-rate control concept. Simulation studies under different load conditions show that the suggested modeling and control concept improves voltage control and the closed-loop system response.