Hierarchical Power Allocation Control for Star-Connected Hybrid Energy Storage System Using Cascaded Multilevel Converters

Youyou Lu ,Jianguo Lyu,Zhao Liu,Xing Wei

doi:10.3389/fenrg.2021.748508

Abstract

Hybrid energy storage system (HESS) using cascaded multilevel converters (CMC) has received increasing attention due to its merits on smoothing power fluctuations for renewable energy systems (RESs). However, CMC-based HESS still faces tough challenges due to asymmetrical ac power distribution. In this paper, hierarchical power allocation control strategy is utilized in CMC-based star-connected HESS to coordinate power between batteries and supercapacitors (SCs). Using the proposed power allocation mechanism, energy management strategy (EMS) with two operation modes can be achieved, which includes SC voltage regulation mode and power compensation mode. In SC voltage regulation mode, SC voltages are regulated to achieve long-term stable operation. Power compensation mode aims to allocate the active power fluctuation and employs SCs to mitigate it. Meanwhile, the principle of the hierarchical power allocation strategy is analyzed to facilitate the accurate control and flexible switching of different operation modes. A series of simulation and experiment tests are executed to demonstrate the performance of the proposed control strategy.

Highlights

Renewable energy systems (RESs), especially wind power systems and photovoltaic (PV) systems, have been globally installed in dc-ac micro-grids in recent years (Liao et al, 2017; Kavousi et al, 2018; Chen et al, 2021)
Hierarchical power allocation strategy is proposed for cascaded multilevel converters (CMC)-based star-connected battery-SC hybrid energy storage system (HESS)
To solve the challenge caused by the synchronous ac current on the converter arms, the presented hierarchical control aims to achieve asymmetrical power coordination by distributing output voltage of SC and battery clusters

Summary

Introduction

Renewable energy systems (RESs), especially wind power systems and photovoltaic (PV) systems, have been globally installed in dc-ac micro-grids in recent years (Liao et al, 2017; Kavousi et al, 2018; Chen et al, 2021). A hierarchical power allocation control strategy is designed for the battery-SC HESS to solve the following challenges: 1) CMC structure is employed for the HESS to solve the limitations of the conventional two-level converters, such as rapid switching frequency, lower efficiency and higher output distortion.

Results

Conclusion