“The data center is an important infrastructure carrier for the implementation of “Internet +” in my country. Relevant statistics show that by the end of 2014, a total of 310 data centers were planned and constructed nationwide, 230 of which have been put into use, about one third of which are large data centers. According to the “Data Center Industry Development White Paper” released by the Data Center Industry Alliance, the total investment in my country’s data centers will exceed 1 trillion yuan from 2011 to 2016. Among them, the cost of high and low voltage power supply and distribution, uninterruptible power supply, refrigeration system and other supporting facilities account for about 75% to 80% of the infrastructure cost.
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The data center is an important infrastructure carrier for the implementation of “Internet +” in my country. Relevant statistics show that by the end of 2014, a total of 310 data centers were planned and constructed nationwide, 230 of which have been put into use, about one third of which are large data centers. According to the “Data Center Industry Development White Paper” released by the Data Center Industry Alliance, the total investment in my country’s data centers will exceed 1 trillion yuan from 2011 to 2016. Among them, the cost of high and low voltage power supply and distribution, uninterruptible power supply, refrigeration system and other supporting facilities account for about 75% to 80% of the infrastructure cost.
The construction boom of large data centers hits. However, in the operation of large data centers, huge power distribution costs are posing challenges to operators, and power distribution units often occupy a large area, which is not conducive to the energy conservation and environmental protection of data centers. Therefore, how to realize the innovation of the power distribution system and significantly reduce the power distribution cost while ensuring the stable operation of the data center has become a concern of the industry. It is under this trend that the medium-voltage UPS began to rise. Medium-voltage UPS can increase the voltage level close to the load center, reduce the low-voltage power distribution link, and reduce energy consumption. It is foreseeable that with the further advancement of de-telecomification, distribution reduction and efficiency enhancement in the telecommunications industry, medium voltage UPS systems will usher in broad market prospects.
The low-voltage power distribution system of large data centers needs to be innovated
my country’s early communication system bears political security responsibilities. Once the communication network is interrupted, relevant parties will be held politically responsible. Therefore, the redundant configuration in my country’s communication system is relatively high, which is evident from the inconsistency of the backup time of early UPS and switching power supply battery packs. Therefore, when constructing the power supply system of the data center, in order to ensure the safety and reliability of the system, the equipment configuration and redundancy should be fully considered.
At present, the power supply and distribution structure of large-scale data center parks or large-scale data centers generally leads high-voltage (110kV) or medium-voltage (35kV, 10kV) from the mains to the high-voltage power distribution room, and then distributes it to the dry-type transformer (converted to 380V) and configures it. A complete set of low-voltage power distribution system, the feeder cabinet in the complete set of low-voltage power distribution system distributes electrical energy to the low-voltage power distribution cabinet on each floor through dense busbars or cables, and then distributes it to large UPS (such as 500kVA, 600kVA). The low-voltage power distribution system generally has a maximum configuration of 2000kVA, and each low-voltage system has at most two sets of large-capacity 1+1-type UPS systems or 2N-type UPS systems. The structure from high-voltage power distribution system-low-voltage power distribution system-UPS is Small and medium-sized data centers were widely used in the early days, but with the increase of the power distribution capacity of a single UPS system in the data center, there are many defects in this power distribution structure.
First, there is a serious waste of investment. A single set of low-voltage power distribution system has wasteful phenomena such as waste of investment, waste of equipment room space, and waste of dense busbars. Although the transformer can also be arranged on each floor, the power supply and distribution structure has not changed. With the use of large-scale UPS, two sets of 600kVA (1+1) are installed under each 2000kVA low-voltage power distribution system to consider the charging current and load redundancy. The remainder will be full.
Second, increasing the level of power supply and distribution increases security risks. In the same power device environment, for the power distribution system, the fewer upstream and downstream switches, the safer, the less the power distribution level, the higher the reliability, and the higher the voltage level close to the load center, the more energy-saving. Large-scale data center park 35kV switch station – 10kV high voltage distribution cabinet – 10kV distribution cabinet – transformer – low voltage distribution cabinet – dense busbar – floor distribution cabinet – UPS system, 8-level power distribution structure, each additional level is It means adding a hidden trouble point.
Third, it affects the usable area of the computer room and increases the construction cost. For a large data center, if each floor is equipped with a transformer low-voltage power distribution room and a UPS system power supply room, more than 40% of the corresponding power supply area should be reserved. And the greater the redundancy of the low-voltage power distribution structure, the larger the area of the computer room.
Medium voltage integrated UPS is on the rise
Looking back at the development trend of high and low voltage power distribution in the field of communication, the AC system has changed from 380V to 10kV in the early stage, and the uninterruptible power supply has changed from 220V to 240V and 336V high-voltage DC. The higher the power consumption of equipment, the higher the voltage level of the power distribution system. The use of high-voltage equipment can reduce line loss, cable bus investment, save equipment floor space, and reduce conversion times, which also means energy saving. Voltage levels up to 10kV and above also have the above advantages. The premise of using UPS such as 10kV is to transfer the metering function, power compensation function and low-voltage generator set of the traditional low-voltage distribution system to the 10kV system.
The measurement in low-voltage power distribution can be measured at the high-voltage side. Traditional data centers often configure metering cabinets in the low-voltage power distribution system in the low-voltage section. However, with the increasing scale of data centers, large-scale data centers have more than 10 sets of low-voltage power distribution systems, which are divided into Electricity, office electricity, etc., it will become a trend to put statistical work on high voltage. While using high-voltage side measurement, it can still automatically report statistics through the data acquisition of the transformer of the medium-voltage integrated UPS.
The compensation function in low-voltage power distribution can be changed to high-voltage compensation and load center proximity compensation. For data centers, inductive loads and capacitive loads exist at the same time. Inductive loads are mainly motor equipment such as air conditioners and fans; rectifier equipment and IT equipment are capacitive loads; that is to say, inductive loads and capacitive loads in data centers are exist at the same time and complement each other. Statistics show that at present, most of the low-voltage capacitor cabinets in the communication bureau buildings are set up manually, because due to the coexistence of inductive and capacitive loads, the power factor cosΦ is usually above 0.92. Compensation in the low-voltage power distribution system belongs to post-compensation and does not play an effective role, and it is easy to cause capacitor resonance in a harmonic environment and there is a risk of explosion. Therefore, the future data center should test its harmonics and reactive power load conditions for the specific computer room environment and perform nearby compensation.
It is an inevitable trend for large data centers to use high-pressure oil machines. At present, large and super-large data centers have promoted the use of high-voltage oil generators, which brings many advantages: the configuration of cables and upstream and downstream switches simplifies the power distribution structure. 1/26 of the cost of upstream and downstream switches and cables, saving investment in upstream and downstream switches and cables, convenient laying and construction, small line loss, and high safety; The output capacity bottleneck faced by the machine system; if the high-pressure air conditioner is used, the high-pressure oil machine must be used, and the starting current of the centrifugal unit is relatively large. , 10kV power supply should be used.” After the high-pressure chiller is used for power supply, the investment in transformers and low-profile and dense busbars and cables can be reduced accordingly. By comprehensively comparing the price factors of high-pressure chillers, preliminary statistics can save 0.75 million yuan/kW (cooling capacity); centralized arrangement of high-pressure oil generators , according to the development of power consumption in the park, the investment can be made in stages and one by one, while the low-pressure oil generator can only be matched with the low-profile modularization regardless of the actual load rate of the oil generator, resulting in a waste of oil generator investment; after the promotion of the use of high-pressure oil generators The ATS cabinet in the low-voltage power distribution system can be reduced.
The above analysis proves that the main functions in the low-voltage power distribution system, such as metering, capacitors, ATS cabinets, etc., can be replaced. Implementing the secondary conversion from high voltage to load center can obviously save more costs and reduce intermediate power distribution links than going through the low-voltage side. It also makes the reliability much improved.
Application Status of Foreign Medium Voltage UPS System
From the perspective of the development of medium-voltage UPS systems in Europe, medium-voltage UPS systems are mostly used in industrial-grade uninterruptible power supply applications, with megawatt-level rated power and up to 99.5% of medium-voltage UPS, energy storage and inverters are still At low pressure levels, it also greatly simplifies maintenance and reduces system costs. Medium voltage UPSs can be retrofitted to custom designs and are compatible with a wide variety of energy storage devices, depending on the required protection time. Supercapacitors and flywheels provide high-density protection in seconds, while batteries can achieve up to 15 minutes of backup time.
The early industrial medium-voltage UPS systems in North America are mostly container-type structures or open-air box structures. The medium-voltage UPS systems used in data centers are mostly indoor and modular, with a capacity of 2.0MW to 20MW. Including input and output switch cabinet, transformer box, main control unit, PES cabinet (medium voltage), bidirectional converter, energy storage box, etc. The backup time of the outdoor type energy storage box is 1~3 minutes, and the backup time of the indoor type can be configured according to customer needs, which can reach more than 30 minutes.
It can be seen that there are similar products abroad, but the foreign medium-voltage UPS is mostly positioned to concentrate the functions of the UPS system in the medium-voltage section, and it has been applied in some large data centers in the United States.
It is particularly worth mentioning that, compared with traditional low-voltage UPS, the medium and low-voltage integrated UPS will reduce the investment cost by 80% in the same scenario, and the reason why this “incredible” change can be brought about is mainly due to the It greatly reduces the area of traditional low-voltage power distribution cabinets, and saves a lot of low-voltage power distribution busbars and cables. At the same time, the use of high-voltage oil generators for generator sets is also convenient for installment investment. It is foreseeable that the construction of the medium voltage UPS system will save a lot of power supply and distribution costs for operators and further enhance the market competitiveness of operators.
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