Non-droop-control-based cascaded superconducting magnetic energy storage/battery hybrid energy storage system

Abstract

Existing parallel-structured superconducting magnetic energy storage (SMES)/battery hybrid energy storage systems (HESSs) expose shortcomings, including transient switching instability, weak ability of continuous fault compensation, etc. Under continuous faults and long-term power fluctuations, SMES part in existing SMES/battery HESSs will run out its energy and fail to quickly respond to subsequent disturbances. This paper proposes a new cascaded topology of SMES/battery HESS. It remains the superiorities of conventional HESS schemes from aspects of fast response (~5 ms) and large energy capacity. Moreover, it avoids the use of droop control and then resolves the transient dynamic problem between the switchover of the battery and SMES. In the cascaded HESS, both the energy storages simultaneously activate when power variation is detected, where the SMES is just for compensating the initial power insufficiency before the full-power start of the battery. The stored energy in SMES can be sustainably utilized and available for multiple repeated power compensations. A simulation is established to discuss the performance of the HESS as an uninterruptable power source with comparisons of the other three cases in aspects of response time, energy capacity, and capital cost. Finally, a scaled-down experiment is tested, and performance comparisons are discussed to verify the technical advancement of cascaded HESS.