Author ：Iflowpower – Portable Power Station Supplier
In recent years, with the increasingness of environmental problems, human living environment has been highlighted, how better environmental protection around the world has become the common research direction of today's countries. New energy has become the main force of environmental protection projects, and new energy vehicles should also be delivered. As a battery of the core component, people's research direction often focus on how to improve performance.
The lithium-ion battery is widely used by the advantages of high quality, small size, high energy density, long cycle life, high storage life, high consistency, environmental temperature and non-pollution-free environmental temperature and non-pollution. Electric car. Single from the current new energy automotive industry eliminated by my country, the power lithium battery elsewhere is tested, although it does not apply to car battery life, its energy storage capacity still has a huge practical value.
If you direct disassembly, it is a lot of waste on the value of the battery remaining. In addition to the internal chemical activity, the chemical ingredients inside the battery are still in good condition, and the remaining energy of these batteries is still satisfying. The use of energy storage equipment, distributed power generation, distributed power generation, and backup emergency energy storage equipment, with the advancement and economic improvement of the secondary use of retired lithium-ion batteries, the secondary use of lithium-ion batteries will Rapid development, so that all the value of the lithium-ion battery is fully utilized.
The lithium-ion battery retired from the electric vehicle, there is a big inconsistent problem. This is the following points: (1) The inconsistency of the battery factory performance, the unevenness of the raw materials and the difference in manufacturing process result in the inconsistency problem of the battery, which is an objective appearance. (2) The environment in which the battery is factory factory, such as different ambient temperatures, self-discharging degree, air humidity, ventilation conditions, etc.
, will cause inconsistency problems. (3) Further aggravation of battery inconsistency, the maximum effective capacity of the battery pack is usually determined by the battery that is the smallest capacity. Since it is in the long-term pre-charge release state, the aging speed will accelerate, form a vicious circle, resulting in inconsistencies of the battery pack Expand trend.
(4) Different external use environments will deepen their inconsistency differences, the arrangement of each module in the battery pack, temperature and humidity, heat dissipation conditions, charge and discharging power, etc., and to some extent increase the battery. Group inconsistency.
The inconsistency of the battery is the maximum factor that restricts its reuse. It is important to include a state of charge (SOC), battery internal resistance, battery capacity, open circuit voltage and operating voltage, discharge platform time, magnification performance, self-discharge ratio, charge and discharge efficiency. And affect factors such as cycle life.
In general, the reuse process of the elimination battery is usually the failure processing, external structure disassembly, battery cell detection, screening classification, and then carry out the tradder. This process can reduce a certain degree of inconsistency, but this reduction is still limited. The traditional energy storage power station is a DC end of the energy storage converter (PCS) using a lithium ion battery.
After the PCS, the charging and discharge control of the battery is performed, as shown in Figure-1 storage energy power station reference principle In the middle large project, since the PCS power and battery capacity are relatively large, it will cause a large lithium-ion battery in parallel to access PCS together, and the charge and discharge control strategy is fully consistent. This is very high on the consistency requirements of the lithium ion battery. If you use a new lithium-ion battery, because of all aspects of testing, the products of the same vendor are more secure in terms of consistency.
Therefore, it will not have a big impact in such projects, but due to the existence of inconsistency caused by the production link, the vendor's lithium-ion battery capacity will also be recommended to prevent inconsistency, it is to prevent inconsistency. Problem. However, the inconsistency of retired batteries is more serious, not just different manufacturers and batch factors, including Paler status (SOC), battery internal resistance, battery capacity, open circuit voltage and operating voltage, discharge platform time, Influencing factors such as multivary performance, self-discharge ratio, charge and discharge efficiency, and cycle life.
Taking the problem brought by battery SOC in secondary use as an example. If the retired lithium-ion battery is normal, the capacity of the secondary utilization is 30% to 80%, then there will be due to the different SOCs, and the individual lithium-ion batteries cannot be fully charged or discharged, which cannot be sufficient. Experition of the remaining value of retired batteries.
If this is still used in the traditional battery management system, it will be forced to launch the operation because of the "short board" during charging or discharging. At the same time, there are factors such as battery internal resistance, battery capacity, open circuit voltage and working voltage, which will also cause adverse effects such as charge, battery circulation, fever, and some may lead to security issues. And because of the inconsistent BMS system methods of different vendors, it is also an unfavorable factor of ladder use.
In response to the various inconsistency factors of the above-mentioned retired battery, Cosa launched a targeted product and a solution of the DC-DC converter for a better ladder. The ion battery is incorporated into the DC-DC converter, and the DC terminal of the PCS is incorporated into the DC bus, and the communication between the PCS is incorporated into the AC grid (this case is the grid network method, and the other case methods can also be implemented. , This article does not introduce it).
Method Schematic Figure-2: Figure -2 Drawing Battery Ladder Using System Schematic Since the lithium ion battery is connected to the busbar through a plurality of DC-DC converters, the DC-DC converter can be based on different retired batteries. Different charge and discharge control strategies, docking different BMS systems, can avoid inconsistencies of retired batteries. Through the DC bus to make the decoupling battery differentiated control and the rectification / inverter control of the PCS are well decoupled, so that the entire system is optimally stable.
The system is applied to the retarding battery of the retired battery has a large advantage, with the following system characteristics: System features: Direct access to different brands, categories, SOCs directly, eliminating between different battery packs Circular problem. System Features 2: Solve the problem of lead-acid lead charcoal cells that cannot be largely paralleled, can access different brands of battery packs to achieve economic utilization value. System Features 3: Replace the battery variety and different residual capacity (SOC) battery in the system to achieve efficient use of retired batteries.
System Features Four: Can realize simultaneous charging, simultaneous discharge, or different sets of charging and discharge strategies. System Features Five: The ladder utilization of retired batteries is an important application scenario for this method. In this method system, key devices are DC-DC converters, Cosda corresponding to KDC50H series DC-DC converter.
This series of products uses modular design, single module power is 50kW, can be equipped with a variety of power levels between 50kW to 600kW through different cabinets, flexible applicable to system methods. The topological schematic diagram of the KDC50H module is as follows: Figure -3kdc50h module Topology Schematic This series of DC-DC converters has the following characteristics: compatible with multiple batteries, support shared battery packs, MPPT functions, modular design, standard 3U size, online Hot plug technology, three level technology, maximum effectiveness can reach 99%, high battery capacity utilization. The advantages of the KDC50H series DC-DC converter are obvious, and the ladder utilization of retired batteries can be solved by the method of direct current bus lines, which will also become the mainstream method of the ladder.
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