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Five advantages of high voltage DC power supply system

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Source:
2021/03/03 15:10

The reliability of the DC power supply system is greatly improved-the main purpose of applying high-voltage DC power supply technology is to improve the safety of the system. The UPS system itself only has a redundant backup for the parallel host, and the system components are more connected in series. Its availability is the result of the multiplication of the reliability of each part of the component, and the overall reliability is lower than the reliability of a single component. In contrast to the DC system, the parallel rectifier modules and battery packs of the system constitute a redundant relationship. The unreliability is the result of the multiplication of each component, and the overall reliability is higher than the reliability of a single component. Both theoretical calculations and operating practices show that the reliability of the DC system is much higher than that of the UPS system. An example is that there are basically no incidents of large-scale DC system breakdown.

DC power supply system

The efficiency of the DC power supply system is greatly improved. At present, the UPS hosts that are widely used are all on-line double conversion types. When the load rate is greater than 50%, the conversion efficiency is similar to that of the switching power supply. However, a reality that cannot be ignored is that in order to ensure the reliability of the UPS system, the UPS hosts all operate in the n+1 (n=1, 2, 3) mode, and are affected by the harmonics and crest factor input from the back-end load. The UPS host cannot meet the requirements for operation. Usually, the maximum stable operation load rate of a single UPS is only 35 to 53%. Affected by the false increase in power consumption of back-end equipment and business development, many UPS systems usually reach the design load rate in the middle and late stages of their life, or even fail to reach the design load rate at all. A single UPS host runs at a very low load rate for a long time, and its conversion efficiency is usually more than 80% or even lower. For the DC power supply system, because of its modular structure, the monitoring module, monitoring system or field duty personnel can flexibly control the number of modules to start and run according to the size of the output load, so that the load rate of the rectifier module is always kept high. Therefore, the conversion efficiency of the system is maintained at a high level.

The input parameters of the DC power supply system have been greatly improved. The field test found that the current commonly used 12-pulse online double conversion UPS mainframe, after adding 11 filters, its input power factor is usually 0.8 to 0.9, and the maximum is only 0.95, and the input current The harmonic content is usually around 7.5%. Correspondingly, due to the application of the PFC circuit, under rated conditions, the input power factor of the switching rectifier module is usually above 0.99, and the input current harmonic content is usually below 5%. The direct effect of the improvement of input parameters is that the capacity of the front-end equipment can be greatly reduced, and the front-end low-voltage power distribution cabinet can no longer be equipped with reactors, which can also reduce the withstand voltage requirements of the compensation capacitor.

The load capacity of the DC power supply system is greatly improved. The load capacity of the UPS system is restricted by two factors. One is the power factor of the load. Taking a certain type of host of a large domestic UPS manufacturer as an example, the output power factor is 0.5 (capacity). The maximum allowable load factor is only 50%; the second is the current crest factor of the load, usually the design crest factor of the UPS host is 3, if the current crest factor of the load is greater than 3, the UPS host will be derated for use. For the DC system, there is no problem of power factor; because it is connected in parallel with large-capacity battery packs with extremely low internal resistance, and the rectifier module has a lot of surplus (charging and standby), its load capacity with high current crest factor is very high. Strong, without special consideration of safety and surplus capacity, it can be used as the main backup power for the centralized power supply of the main base station.

The transmission voltage drop of the DC power system is small-the DC cable line does not have the trouble of the capacitive current in the AC cable line, there is no magnetic induction loss and dielectric loss, basically only the core wire resistance loss, the insulation voltage is relatively low, the DC transmission technology is more suitable for long distances Transmission, in line with the current national requirements for energy saving and environmental protection, is a green and environmentally friendly power supply program.

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