Design and assessment of SMES and battery hybrid energy storage for microgrid applications

Abstract

The major challenges of microgrid systems are driven by energy shortages and environmental concerns, which encourage energy storage systems be integrated into microgrids. With the implementation of energy storage systems, microgrids become more stable and more effective. This research propose to hybridize superconducting magnetic energy storage (SMES) with battery to build a hybrid energy storage system (HESS) for microgrid applications. The SMES-battery HESS is a good choice to compensate for the highly fluctuating power demand in microgrids and extent battery service lifetime. However, the SMES-battery HESS applied in microgrids is a newly proposed concept. Challenges remain on the HESS control method, system design, energy management method and HESS sizing optimisation. Therefore, the achievement of this PhD research project is the development of a SMES-battery HESS for microgrid applications. The accomplishments are list below:

- The SMES magnet structure design has been completed in this thesis. The newly developed method is able to design the SMES with a requested energy capacity, which is vital for SMES-battery HESS applications. Moreover, the weak point area in the SMES magnet has been located. That can be used to prevent SMES quench.
- To achieve a high power capacity in the SMES magnet in the HESS for microgrid applications, a feasibility study using Roebel cable to build the SMES magnet has been investigated.
- A new fuzzy logic energy management method has been proposed to deal with the power unbalance inherent in microgrids. The proposed method is able to allocate the power output of the HESS for high fluctuating power demands.
- A novel two-stage energy management method with PI-droop control is developed, which is able to improve the battery performance when a microgrid is disconnected from main grid.
- The SMES-battery HESS experimental platform was built to test the proposed method’s achievability.

By investigating a HESS for microgrid applications, a HESS topology and SMES structure design has been proposed. Furthermore, a control methodology for the HESS in the microgrid application has been established. The experimental results validate the HESS achievability. This prototype SMES-battery HESS is the first step towards the implementation of future commercialised SMES-battery HESS for microgrids.

Date of Award	29 May 2019
Original language	English
Awarding Institution	University of Bath
Supervisor	Francis Robinson (Supervisor) & Xiaoze Pei (Supervisor)