Second Life Battery Energy Storage Systems: Converter Topology and Redundancy Selection

Abstract

Battery energy storage systems have traditionally been manufactured using new batteries with a good reliability. The high cost of such a system has led to investigations of using second life transportation batteries to provide an alternative energy storage capability. However, the reliability and performance of these batteries is unclear and multi-modular power electronics with redundancy have been suggested as a means of helping with this issue. This paper reviews work already undertaken on battery failure rate to suggest suitable figures for use in reliability calculations. The paper then uses reliability analysis to investigate six different multi-modular topologies and suggests how the number of series battery strings and power electronic module redundancy should be determined for the lowest hardware cost using a numerical example. The results reveal that the cascaded dc-side modular with single inverter is the lowest cost solution among the topologies.

Analysis and Comparative Study of Different Converter Modes in Modular Second-Life Hybrid Battery Energy Storage Systems

“…In order to address challenges in integrating these second life batteries to the grid system modular power electronic converters are preferred [7] - [9] because this type of converters provides a better reliability and flexibility compared to traditional two level designs. Previous research on modular BESS considered the same type of batteries and focused mainly on high power, medium voltage grid systems (e.g.…”

Control of Cascaded DC-DC Converter Based Hybrid Battery Energy Storage Systems: Part – I: Stability Issue

“…<100V) to a grid-tie inverter: a) a parallel converter approach and b) a series/cascaded approach. A previous study on this area suggested a cascaded approach over the parallel approach from reliability and cost perspective [6]. Apart from the reliability/cost issues, the parallel approach has other drawbacks in conjunction with low voltage energy sources [7], [8] such as: a) low converter efficiency (e.g.…”

“…It can be seen that the terms like vbatt,i and vdc,i in the transfer functions (6) and (9) are essentially time varying. However, these are slow variables and take several minutes to change depending on the battery charge capacity which is normally 10's Ah.…”

“…According to this method, the regulator gains Kv and Tv are selected such that the amplitude and the phase plot of GHv (s) are symmetrical about the crossover frequency ωgc, which is at the geometric mean of the two corner frequencies of GHv (s). Now, assume Tv = aTd, where 'a' is a nonnegative real value, therefore, expressions of gain-cross over frequency ωgc and PM become the following: ) to vary according to (6) which in turn alters the designed gain crossover frequency or the closed loop bandwidth. The expressions for gain crossover frequency can be found by solving (13).…”

“…Finally in-depth experimental results are presented to prove the stability using a hybrid battery energy storage system prototype. [3]- [6] covering both theoretical studies and small prototype units with similar batteries. However, battery chemistry development is a highly funded research area and it is unlikely that battery chemistry in vehicles to date will be the same as that in 10 years' time.…”