Foreword: In the balancing management process of megawatt-level energy
storage frequency modulation power stations, the balancing current is required
to be large, and the balancing process will produce large losses. Soft switching
can reduce switching losses, improve balancing efficiency, avoid electromagnetic
interference, and reduce volume. It is Development trends in balanced topology.
However, with the development of large-capacity batteries in the future,
improving the consistency of the battery body is the primary direction to extend
the service life of energy storage power stations.
Research background: Lithium-ion batteries have developed rapidly in the
field of frequency modulation of energy storage power stations in recent years
due to their advantages such as high energy density, fast response speed, and
long cycle life. In order to meet the voltage and power requirements of
frequency modulation power stations, a large number of battery cells need to be
connected in series. The resulting inconsistency in series connection of the
battery packs, as well as the inconsistency aggravated by high rates and
frequent switching of charge and discharge states during the frequency
modulation process, seriously affect the battery. The service life and safety
performance of the group. Among the measures to mitigate inconsistency, the
battery manufacturing process and battery sorting only improve the consistency
of the initial state of the frequency modulated battery pack. Battery aging
maintenance management only targets frequency modulation modules in non-working
states, and the use environment and usage condition management only It can slow
down the deterioration of inconsistency in battery packs during frequency
modulation applications. Therefore, under the limitations of the existing
manufacturing process level, more effective balance management technology should
be used to actively control the battery pack to improve the inconsistency of the
series lithium-ion battery pack based on power frequency regulation in the
resting state and in use. Sexual issues.
Key content introduction: At present, lithium-ion series battery pack
balancing management technology is mainly used in application scenarios such as
small-capacity storage battery packs, electric vehicle power batteries, and
energy storage power stations. There is relatively little research on the
balancing management of energy storage frequency modulation batteries.
Therefore, this article focuses on current The lithium-ion series battery pack
balancing management technology is studied in combination with the
characteristics of power frequency regulation, and the applicability of the
lithium-ion series battery pack balancing management technology based on power
frequency regulation is reviewed and analyzed.
Among them, the energy transfer equilibrium topology between any monomers
has the advantage of high equilibrium efficiency, but the equilibrium speed is
low. Using multiple arbitrary inter-cell energy transfer topologies for
hierarchical control can increase the number of target batteries in a balancing
process, but the cost will be greatly increased and the control will be more
complex. It is used for series-connected lithium-ion battery packs in
large-scale energy storage power stations. Balanced management lacks economy.
The energy transfer balancing topology between the cell and the battery pack can
realize the energy transfer between one battery and the entire battery pack in
one balancing process. It has the advantage of fast balancing speed and is
suitable for large-scale energy storage frequency modulation power station
applications. Advantages of fast equalization. However, in this type of
topology, there is a phenomenon of reverse balancing of some battery cells
during the balancing process. That is, when the single battery with the highest
power transfers power to the entire battery pack, some of the battery cells with
higher power in the battery pack were originally It should release power but
increases its own power, resulting in a reverse equilibrium phenomenon, so it
needs to be gradually improved. The energy transfer balancing topology between
battery packs transfers the power of some batteries with higher power to some
batteries with lower power in the battery pack. It has the advantages of fast
balancing speed and high balancing efficiency. It is an ideal balance for
large-scale energy storage frequency modulation power stations. Regarding the
future development trend of management, the current main problems are that there
are a large number of switches and complex control methods, and related research
is still in its infancy. This article believes that the energy transfer
balancing structure of any number of batteries between battery packs can solve
the problem of reverse balancing while taking into account the balancing speed.
This topology has important research value and will play an important role in
balancing lithium-ion batteries in series for large-scale energy storage in the
future. Management is of great importance.
Conclusion: This article classifies and reviews the different balancing
topologies and control strategies of series lithium-ion battery packs from the
perspective of energy flow and balancing control objectives. It also combines
the high-rate shallow charging and shallow discharging of energy storage
batteries based on frequency modulation and the frequent switching of charging
and discharging states. Characteristics, the applicability of battery pack
balancing in energy storage frequency modulation power stations is analyzed. The
following suggestions are made for the development trend of balancing technology
of series-connected lithium-ion battery packs in megawatt-level large-scale
energy storage frequency modulation power stations:
(1) At present, the balancing efficiency of the two-way energy transfer
balancing topology between the cell and the battery pack can reach 72%~93%,
which is the most widely used. The balancing efficiency of the energy
transferring topology between adjacent two cells between the battery packs is as
high as 75%. ~99%. In the balancing process, increasing the number of cells of
the balancing target battery in one balancing process and the selectivity of any
balancing target battery can alleviate the reverse phenomenon and improve the
balancing efficiency and speed. In the future, especially any multi-cell energy
transfer balancing topology between battery packs will have important research
value, and is of great significance to the balancing management of
megawatt-level large-scale energy storage frequency modulation power
stations.
(2) In terms of balancing strategies, since the parameters of the battery
pack are coupled to each other and have complex relationships, they should be
closely integrated with actual applications, and appropriate parameters should
be selected as the balancing consistency evaluation criteria for different
application scenarios. The balancing strategy that selects multiple parameters
as the balancing target can effectively avoid the failure of the balancing
target. Compared with the balancing strategy that uses a single parameter as the
balancing target, it is more reliable and can be better suitable for power
frequency modulation energy storage battery balancing, but its control process
It is complex, has higher technical requirements and needs further research.
(3) The balanced topology should minimize the number of electrical
components and switches used, reduce costs and control complexity, reduce the
probability of component accidents, and reduce the impact of the balanced
topology itself on the life of the energy storage power station. In addition, in
the balancing management process of megawatt-level energy storage frequency
modulation power stations, the balancing current is required to be large, and
the balancing process will produce large losses. Soft switching can reduce
switching losses, improve balancing efficiency, avoid electromagnetic
interference, and reduce volume. It is Development trends in balanced topology.
However, with the development of large-capacity batteries in the future,
improving the consistency of the battery body is the primary direction to extend
the service life of energy storage power stations.
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