Performance Improvement of PWM Control Methods for Voltage Step-Down in Series Resonant DC–DC Converters

Vadim Sidorov,Dmitri Vinnikov,Andrii Chub

doi:10.3390/en13174569

Abstract

The paper is focused on galvanically isolated series resonant DC–DC converters (SRCs) with a low quality factor of the resonant tank. These converters provide input voltage regulation at fixed switching frequency and good power density. Different modulation methods at the fixed switching frequency enable the implementation of the voltage buck functionality in these converters. The SRC under study is considered as a step-up front-end DC–DC converter for the integration of renewable energy sources in DC microgrids. The paper evaluates the voltage buck performance of the SRC achieved by using different pulse-width modulation (PWM) methods including conventional PWM and shifted PWM. Moreover, the new PWM methods, i.e., the hybrid shifted PWM (HSPWM), improved shifted PWM (ISPWM), and hybrid PWM (HPWM), are proposed to overcome the disadvantages of the existing methods. They improve the power conversion efficiency in the buck mode by reducing the power losses in the semiconductor switches and the isolating transformer of the SRC. The proposed and the existing methods are benchmarked in terms of the components stresses and power conversion efficiency. The presented findings have been experimentally validated by the help of a 200 W prototype, which demonstrated the lowest power loss in the case of the HPWM.

Highlights

Much attention is being paid to low-voltage DC microgrids in small-scale systems such as the power systems of buildings
A 200 W prototype of the series resonant DC–DC converter (SRC) converter was built to verify the operation of the pulse-width modulation (PWM) control methods and compare experimental results with the theoretical analysis
Shapes of the transformer current waveforms (Figure 8) correspond to the theoretical curve of the resonant current in Figures 2 and 4 for each PWM method

Summary

Introduction

Much attention is being paid to low-voltage DC microgrids in small-scale systems such as the power systems of buildings. Residential microgrids are usually designed with a centralized DC bus with an operating voltage of 350–400 V [2,3]. Direct-current devices, renewable energy sources, and energy storage are interfaced with the DC bus through individual DC–DC converters. DC microgrids are connected to the utility grid using a grid-tied inverter [4,5]. This technology facilitates realization of zero energy buildings as they require on-site energy production to offset their consumption [6]

Methods

Results

Conclusion