Abstract: With the continuous development of electronic equipment application technology and manufacturing process, advanced control technology and large capacity power supply system can be used in power and communication systems. In this paper, the necessity of integrating UPS system in rail transit will be summarized, and the schemes of rail transit station and UPS system will be studied and compared.
Keywords: rail transit; UPS; DC power supply
Introduction: At present, the advanced control technology and power supply system have created favorable conditions and sufficient technical support for the effective integration of power supply systems in domestic transportation and rail projects. Based on this, the research on rail transit UPS system integration is of great significance.
1、 Necessity of integrating UPS system in rail transit
At present, the weak current system of domestic urban rail transit is huge, and there are many kinds of equipment. For example, the DC operation power supply for substation, accident lighting, automatic fire alarm, PSD, automatic fare collection, equipment monitoring system, signal equipment, communication equipment, etc. require high power supply reliability and quality. In case of failure of the power supply system, a backup emergency power supply shall be provided to deal with the failure and provide emergency power within a certain time.
In the traditional rail transit project, the construction team will set the backup power supply of the electrical system separately, so as to ensure that each weak current system member has a relatively reliable backup power supply; Separate backup power supply for each weak current system can ensure that each weak current system manages its power distribution equipment by itself, and can effectively avoid the paralysis of the whole weak current system caused by the single fault of the system. A large number of batteries and power distribution cabinets will be used to independently set the backup power supply of the weak current system. Repeated configuration of power cabinets will generate more power supply rooms, equipment maintenance personnel, higher investment, and also need to occupy a larger land area.
2、 Scheme of rail transit integrated UPS system
(1) Program purpose
The purpose of integrating UPS system in rail transit project lies in the following aspects: First, integrate the charging device and battery device of each power supply system, and centrally arrange the charging device and battery device of each power supply system, so as to facilitate the subsequent unified management and maintenance of the power supply system. Second, through the centralized layout of each power system, the land area of power system equipment is reduced to a certain extent, and the project cost of the station is effectively reduced. Third, through the effective integration of the charging device of the power supply system and the battery hardware, avoid the repeated battery configuration, share project resources, and save equipment investment. Fourth, select the power supply brand uniformly to facilitate the subsequent equipment bidding.
2） UPS power integration mode
The UPS integrated power supply of rail transit is provided with two sets of power supply devices including battery inverter and rectifier, as well as smart electricity, intelligent control power supply and load synchronization controller. When the system is in normal operation, the UPS device realizes rectification and inversion. With the help of two sets of system equipment, the current is divided equally to provide the same high-quality power supply for each system. When the bus tie disconnector of UPS device is in normal condition, the device is put into operation; When the mains power is lost, the UPS device of rail transit will store the inverter battery
Energy storage, providing the same high-quality power supply for each system; When one UPS device of rail transit fails, the other UPS device will provide stable power supply for each power supply system; In case of extreme conditions, both sets of UPS devices of rail transit project will fail. Is passed. Static bypass. Pass the event to each power system to provide stable and high-quality power supply. If it is necessary to clean the bus temporarily or replace the maintenance switch. The bus coupler switch shall be separated to maintain and clean each section of bus. According to the traditional design process, the operation unit needs to clean the power supply equipment regularly, and preliminarily check the power supply equipment during cleaning; The integrated UPS device can fully meet the traditional design process. At the same time, the integrated UPS can greatly save the land area of the project.
（3） DC power integration mode
The DC power integration mode effectively integrates the battery pack with the continuous current charging module to provide uninterruptible power supply for platforms, automatic fare collection, automatic fire alarm, integrated monitoring, signal equipment, communication equipment and substations. Compared with the decentralized setting mode, this mode can centralize the setting of batteries, charging modules and high-frequency switches, which is convenient for unified maintenance of batteries in all systems, and convenient for rail transit management units to set up professional maintenance teams to enhance maintenance quality]. At the same time, this integration method can reduce the battery capacity of each system, avoid repeated hardware configuration, and reduce the floor space; Compared with the current domestic power integration system, it is progressiveness; However, due to the special power supply system required by weak current systems such as fire alarm, integrated monitoring, signal equipment, communication equipment, etc., it is necessary to configure a separate inverter for the above power system. Considering the reliability of power supply for the power system, UPS devices without batteries are set for each power system.
The operation mode of the DC integration system is as follows: First, under normal conditions, each weak current system of rail transit will use two power supplies to supply power. Second, if all AC power supplies of each weak current system of rail transit fail or lose power, the battery equipped with each weak current system will provide a backup stable power supply, record the power consumption time while the battery is running, and cut off the system load according to the different backup time of each weak current system. Compared with the UPS power integration mode, the DC power integration system can further reduce the floor area of the power integration room and reduce the project cost.
Comparison of three schemes
Comparing the two integration schemes, we can find that both schemes have certain disadvantages. The disadvantage of the DC integration mode is that the accuracy is not as good as that of the UPS power supply system, and it is unable to provide stable power supply for signal equipment and communication equipment with the network equipment and computer equipment as the core. It can only be used as the backup power supply for each power supply system. The UPS power supply system has weak current impact resistance, mainly for the inductive impact load, and is not suitable for the DC impact load power supply system. At the same time, UPS power supply system has high output accuracy, can output stable AC power, and is more suitable for providing power for network and computer equipment [2]
In terms of performance, the DC integration mode has high maintainability and reliability, which can effectively solve the problems of redundant configuration and centralized battery maintenance. It is also highly implementable. Most traditional DC manufacturers in China have the ability to integrate the DC system. UPS power supply system has higher maintainability and reliability, less equipment, and higher integration, and can handle redundant configuration problems under the condition of constant total investment. In contrast, the DC integrated power supply has good economy. The cost of the whole system is about 1.75 million, accounting for only about 40 square meters of land. The cost of the UPS integrated power supply system is 2.5 million, accounting for 90 square meters of land
4、 Conclusion
To sum up, the rail transit UPS integration system has certain necessity. The specific integration scheme is mainly the UPS power integration mode and the DC power integration mode. Both of them have strong maintainability, reliability, enforceability and certain economy, which can improve the quality of rail transit projects, reduce the land occupation area, reduce the project cost, and improve the economic benefits of ten owners