Abstract: With the development of science and technology and the continuous improvement of power automation level, the application of UPS power system in enterprise power supply system has become more and more extensive. In this regard, based on the detailed analysis of the UPS power system, the article introduces the selection and configuration of the UPS power supply, and conducts in-depth research on the maintenance technology and measures for extending the service life of the UPS to improve the practical application performance of the UPS power supply.
Keywords: UPS power supply; selection; maintenance; measures
1 UPS function
UPS power system covers subsystems such as rectification, energy storage, conversion and switch control. Among them, the rectification system completes the conversion between alternating current and direct current, and the energy storage system is used for energy storage of the UPS power system to realize mutual conversion of electric energy and chemical energy. The conversion system includes an inverter bridge and a control filter circuit for converting direct current into alternating current. The switch conversion control system includes two types of conversion type and parallel type, and is a type of thyristor non-contact switch.
2 UPS Selection and Configuration
2.1 Product Type
The development of UPS power system has gone through two major stages, namely rotary UPS power system and static conversion UPS power system, early rotary UPS power supply. The system has been unable to adapt to the economic and social development needs of the current high-speed development. At the same time, with the development of power electronics technology, the static conversion UPS power system has been widely used. Static UPS systems include three major categories, namely backup, online and online interactive.
2.2 Parameter Specifications
The output parameter of UPS is shown in the following table:
UPS can realize single and multi-machine parallel/series operation, maximum discharge current of battery: I=Scos? Stains? word? Grab i, related to rated output power, load power factor and inverter efficiency. When the UPS multi-machine is operated in combination, the parallel current sharing control under the condition of no cable can be realized between the single machines, the influence of the single point of the system on the system is eliminated, the network protection level is improved, and the bit error rate of the data transmission is reduced.
2.3 Configuration scheme
(1) Centralized and decentralized power supply scheme
Centralized power supply scheme means that a single UPS is equipped with multiple power loads, and its UPS model is relatively large in size, which can be more convenient. Power supply management, power supply and distribution reliability and safety performance are higher, but the cost is also higher; decentralized power supply scheme is a single UPS configuration single load. For the design of UPS power supply project, the UPS power supply configuration plan should be based on the specific application and actual conditions. Economic situation.
(2) Battery configuration time
For the relatively stable power supply area, the UPS system battery configuration takes 15min-1h; for the grid power supply continues to tighten, due to frequent power failures, power supply is tight, this type of UPS configuration The battery generally needs a long delay system of 4-8 hours. When configuring the generator to supply power, the UPS system load configuration only takes 30min-1h.
(3) Reliability Design
The reliability design of UPS power system plays an important role in ensuring the continuous and stable supply of power supply and ensuring the safe and stable operation of power equipment, especially for financial centers and data centers. Reliability design of important departments is particularly important. For the power supply reliability design of such critical loads, two-way AC mains supply plus a standby generator set, plus multiple UPS parallel units (or two-machine serial backup) are usually adopted. It adopts two-way AC mains supply, including high and low voltage substation, switch and UPS system, and can further improve its power supply reliability by redundant parallel mode. In the power supply scheme, the redundant parallel UPS is divided into loads. The degree is aging, and the communication coordination and balance control between multiple machines is completed by the parallel board. UPS1 and UPS2 are connected to the mains in parallel, and the parallel output is supplied to the same critical load to improve the reliability of the whole system.
3 Maintenance technology and measures for UPS extended service life
3.1 Regular inspection
Regular inspection of the terminal voltage and internal resistance of each unit battery in the UPS power system is the guarantee for the normal operation of the power supply system. Taking a 12V unit battery as an example, the system operation can be grasped in time by periodically checking the voltage difference between the unit batterys and the internal resistance. When the terminal voltage difference is greater than 0.4V or the internal resistance is greater than 80mΩ, balanced charging measures should be taken in time to eliminate the terminal voltage imbalance. Unbalanced battery characteristics caused by the operation of the UPS power system are difficult to eliminate through the charging circuit, and offline equalization processing is required in time.
3.2 Reducing Deep Discharge
The operating life of the battery system is closely related to the depth of discharge. In the case of commercial power interruption, when the electric load is small, the ratio of the available capacity of the battery to the rated capacity is larger, and the battery is discharged. The depth is deeper. In actual applications, the deep discharge of the battery pack should be prevented, thereby prolonging the service life of the battery pack.
When the UPS power supply is stopped for more than 10d and then restarted, the internal resistance of the battery will increase continuously due to the long-term non-discharge status of the power supply, resulting in battery failure. For the treatment of such situations, the UPS power supply should be started under no load conditions, so as to recharge the battery for 10-12h or more with the charging circuit inside the machine. At room temperature, the available capacity drops to 97% of its rated capacity after one month of storage, and further decreases with the storage time. Therefore, the discharge operation should be performed every 2-3 months, and the load is about the rated output. 30%.
3.4 Using Power Supply Peak Charging
Zhao Li. Battery Dictionary [M] Beijing: Chemical Industry Press, 2010.