State-of-charge balancing method for multi-branch parallel grid-connected battery energy storage system
A technology of battery energy storage system and state of charge, which is applied in charge balancing circuits, battery circuit devices, AC network load balancing, etc. question
Active Publication Date: 2021-06-22
ZHEJIANG DAYOU IND CO LTD HANGZHOU SCI TECH DEV BRANCH CO +2
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Problems solved by technology
With the gradual application of decommissioned power batteries in the battery energy storage system in the future, this problem will become more and more obvious. It is manifested that as the SOH of each battery pack gradually decays, the degree of SOH dispersion increases, and the offline setting in the traditional droop control method It is difficult to adjust the parameters of the droop curve in time, resulting in the inaccurate allocation of the overall output power
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[0041] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments.
[0042] The embodiment of the present invention proposes a multi-branch parallel grid-connected battery energy storage system charge state equalization method, such as figure 1 shown, including the following steps:
[0043] S1: Definition of the state of charge SOC of the energy storage battery pack.
[0044] The state of charge refers to the ratio of the remaining capacity of the energy storage battery after it has been used for a period of time or left unused for a long time to the capacity of the fully charged state, usually expressed as a percentage. The ampere-hour integration method is considered to be the most commonly used SOC estimation method due to its simplicity and effectiveness. Its definition is shown in formula (1):
[0045]
[0046] Among them, SOC 0 Refers t...
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The invention relates to the field of grid-connected battery energy storage systems, in particular to a state-of-charge balancing method for a multi-branch parallel grid-connected battery energy storage system. The balancing method comprises the steps of defining the state-of-charge (SOC) of an energy storage battery pack; defining the SOH (state of health) of the energy storage battery pack; obtaining the maximum available capacity Qmax_i of each battery pack, and calculating the initial health state SOH0i of each battery pack; and defining an SOH calculation formula considering the depth of discharge (DOD) and the number of cumulative cycles (Cacu); calculating SOHi of each battery pack; setting an SOC index n in SOC equalization according to the SOC difference value of each energy storage battery pack; setting initial droop coefficients mSOH and SOC; when the difference of the SOC of each energy storage battery pack is greater than a threshold value d, executing an energy storage battery pack SOC equalization strategy; and when the SOC difference of the energy storage battery packs is smaller than a threshold value d, enabling the energy storage battery pack SOC equalization strategy to quit. According to the method, SOC equalization of all the energy storage battery packs is realized, the influence of SOH on SOC equalization is considered, and the problem of unreasonable power distribution caused by reduction of the maximum available capacity of the battery packs is solved.
Description
technical field [0001] The invention relates to the field of energy storage battery grid-connected systems, in particular to a method for balancing the state of charge of a grid-connected battery energy storage system with multiple branches connected in parallel. Background technique [0002] In order to solve the uncertainty of renewable energy power generation, and also to meet the needs of power grid frequency regulation and peak shaving and valley filling, energy storage battery systems in microgrids have developed rapidly in recent years. Lithium battery, as the carrier of electric energy storage in the energy storage system, has excellent discharge and charge volt-ampere battery curves, and is convenient for later maintenance. However, limited by its own physical properties, the capacity or power of a single battery cannot satisfy medium and large loads, so a multi-energy storage battery pack system is introduced to meet the load. [0003] In a multi-energy storage ba...
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IPC IPC(8): H02J7/00H02J3/32
CPCH02J7/0048H02J7/005H02J7/0014H02J3/32Y02E40/10
Inventor 郑伟彦单立新吴靖陈佩军金明蒋燕萍赵海荣赵欢伟
Owner ZHEJIANG DAYOU IND CO LTD HANGZHOU SCI TECH DEV BRANCH CO