# Performance evaluation of a series-connected step-up/down partial power converter for battery energy storage applications

## TL;DR

This paper introduces a new high-efficiency battery energy storage converter that reduces component stress and improves power density.

## Contribution

A novel series-connected partial power converter is proposed with reduced voltage and current stress and high efficiency.

## Key findings

- The SUDPPC reduces voltage and current stress on components compared to traditional converters.
- The prototype achieved 98.15% peak efficiency with only 14.3% of active power processed under full load.
- Design guidelines and universal interconnection schemes were developed for practical implementation.

## Abstract

The conventional full power converter (FPC) for battery energy storage applications is limited by bulky components and suboptimal efficiency. In response, a series-connected step-up/down partial power converter (SUDPPC) with high power density is proposed in this paper. It consists of an LLC resonant converter operating at a fixed switching frequency cascaded with a full-bridge converter capable of providing bipolar output. By connecting the SUDPPC in series with the load, the voltage stress on the series side and the current stress on the parallel side are markedly reduced. The four-quadrant function provides support for further optimization of the rated power level. Universal series interconnection schemes are elaborated, and design guidelines are formulated based on power distribution characteristics. Furthermore, the topology is evaluated in terms of nonactive power and component stress factor (CSF), and benchmarked against a four-switch buck/boost FPC and a phase-shifted full-bridge step-up partial power converter (SUPPC). Finally, a 1.1 kW prototype is developed to experimentally validate the theoretical analysis, demonstrating that only 14.3% of the total active power is processed under full-load conditions, with a peak efficiency of 98.15%.