Discussion on power supply mode of data center computer room

October 22, 2021
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Discussion on power supply mode of data center computer room

In the construction of IDC room, the construction of power system is undoubtedly the top priority. The development of various businesses and the stable work of various servers are inseparable from stable, reliable and uninterrupted power supply. This paper briefly discusses the basic principle, advantages and disadvantages and feasibility of several power system structures in IDC room.

1、 The demand of IDC room for power supply has the following characteristics
1. High reliability for power supply
IDC's customers are generally enterprise customers, and some are even portal websites. If the load is interrupted, IDC service providers will face huge losses, so they have high requirements for the reliability of power supply.

2. Large load capacity
IDC computer room construction investment is huge, and will take into account the business growth in the next few years, so it should be able to undertake a large enough business volume. Generally, about 50-100 racks are placed in a machine room, and the load of each rack is about thousands of watts. Therefore, the load of a machine room is about hundreds to thousands of watts. An IDC center may build multiple machine rooms.

3. Relatively centralized power supply mode
In order to share risks and take into account the convenience of centralized power supply management, it is generally considered according to the load capacity of a computer room, which is about hundreds to thousands of kilowatts.

4. High requirements for harmonic pollution of equipment
With the increasing requirements of the state for energy conservation and environmental protection, telecom operators respond positively. At the same time, IDC room is also a large power user, which is the key focus of power supply units. It has a high degree of attention to harmonics, which is a trend.

2、 Traditional UPS power supply solution
Traditional data communication equipment requires AC input power supply, which is generally the same voltage and frequency as the municipal power supply, that is, 220V, 50Hz single-phase AC power supply. The power supply system of traditional data communication equipment is UPS system. UPS system is generally composed of rectifier, inverter, battery and static switch. When the mains power is normal, the mains power is transformed into DC power through rectifier to supply inverter, and charge the battery at the same time. The inverter converts DC power into AC power to supply load. In case of UPS failure, the load can be converted to bypass mains power supply through static switch. In case of long-term mains power failure, the standby generator set will supply power.
Although the equipment in IDC room is powered by single-phase power supply, the power is getting larger and larger, and the power of single-phase UPS can not be done very much, which is limited. The solution is to use three-phase UPS for power supply, the power is generally divided into three phases, and UPS is combined at the same time to solve the reliability of power supply. Since UPS finally supplies power to the data equipment through inverter, if the inverter and switching part fails, the battery does not directly supply power to the data equipment, which will lead to the interruption of the data equipment.
Several common UPS power supply modes

1. Tandem hot backup
This UPS power supply mode eliminates single point of failure and is simple to realize, but only one UPS is loaded at the same time. Therefore, it has the problems of poor overload capacity and uneven aging of main and standby machines, which has been rarely used at present.

2. Parallel redundancy
The biggest advantage of this UPS power supply mode is that the load can be divided equally. If any UPS fails, it will be cut off. The UPS system can still work in online mode without any switching. The system capacity can be expanded by adding UPS according to the load.
3. Dual bus power supply mode

The biggest feature of this UPS power supply mode is to provide two mutually unaffected power supply buses at the same time, which are respectively provided to dual power loads or to single power loads through STS. This method also eliminates the single point of fault, but limited to the power supply scheme, LBS (synchronous control) and STS (two-way switching) are added, so the fault point is also added.
Advantages of UPS power supply scheme:
The technical scheme is mature and is widely used at present.
AC output, not easy to pull arc.

Disadvantages of UPS power supply scheme:
It is difficult to parallelize, and voltage, frequency and phase synchronization are required.
The system design is complex and there are many single points of failure
There are many transformation stages and the efficiency is relatively low
High input harmonic and low power factor

3、 Solution of hybrid system sharing 48V bus
The structure of this power supply system is characterized in that the power supply systems of DC load and AC load use - 48V bus as the input power supply. In case of mains power failure or rectifier failure, the - 48V bus power supply is uninterrupted because the battery is connected in parallel with the output bus. The DC load is directly powered by - 48V bus, and the AC load is powered by inverter, that is, the inverter powered by - 48V DC power supply replaces ups.
Advantages of hybrid system solution:
The technology is mature. 48V power supply is a real uninterruptible power supply with pure output, so the overall stability of the system is improved. It is not easy to pull arc and has high safety.
Disadvantages of hybrid system solution:
In the power chain of AC load, the number of power conversion is increased, and the voltage is low and the current is large, which increases the loss and reduces the system efficiency.
This power supply system structure is only applicable to the case where the AC load is medium and small power.

4、 Rectifier type RAC high voltage power supply solution
Represented by the best new power supply for new telecom networks and services published by Intelec in 2001 and the new research on RAC power supply technology integrating Telecom and Data Communication published in 2000, France Telecom tried it out. RAC power supply system, similar to the traditional 48V DC power supply system, the DC bus is replaced by the rectified bus, which is actually pulsating DC. The system consists of rectifier bridge, high voltage battery pack, battery switch, charger, etc. The input harmonic current suppression and power factor of this RAC power supply system need to be compensated, and the harmonic suppressor must be connected in parallel on the RAC bus.

Advantages of Rac high voltage power supply solution:
There is only one conversion stage in the whole power supply circuit, with low loss and high efficiency; The battery charger is only used to charge the battery offline, so it has small capacity and low cost. Disadvantages of Rac high voltage power supply solution:
High voltage and high safety standards are adopted; A large number of single batteries are used, which requires more strict battery management.

5、 Discussion on the feasibility of high voltage DC power supply
The internal power supply condition of data equipment is that the internal power supply of computer host, display, printer and other electrical equipment is switching power supply. The input AC 220V is rectified and filtered into DC 300V, and then reduced and stabilized into low voltage through power switch tube and switching transformer to provide power for each part. Generally, the AC voltage is between 110-250V, and the DC voltage after rectification and filtering is between 150v-340v. Therefore, if a 150v-340v DC voltage is input to these equipment, the equipment can work normally. Considering that the rated voltage is within the range of 228v ~ 280v (19 or 20 backup 12V batteries), the DC power is still 228v ~ 280v after passing through the bridge rectifier circuit and filtering, and is between 150v-340v, so the switching power supply can still work normally, The current experiments show that the effect is good when the data equipment inputs about dc270v.

6、 Solution 1 of high voltage DC power supply system
The AC input, rectifier circuit, storage battery and charger of high voltage DC supplier scheme I are the same as RAC power supply system. The difference is that Rac power supply system directly supplies RAC to centralized high-power DC / DC converter, and then converts it into stable high-voltage dc270v. NTT company of Japan has tested this system. In case of AC input power failure, the battery supplies 270V DC to the load equipment through DC switch and high-power DC / DC converter.
Advantages of this power supply system:
High reliability and efficiency, especially when the power of load equipment is large; Low cost;
Disadvantages of this power supply system:
Single high-power DC / DC is adopted, with high voltage, high current and high safety standards; A large number of batteries are used, which requires more strict battery management.

7、 Solution II of HVDC power supply system
This scheme is a trial power supply system for domestic telecom operators to improve power supply in IDC room. Yancheng Telecom was the first representative. Now some telecom branches and mobile branches have tried it. Similar to the traditional 48V power supply system, it is composed of multiple parallel redundant rectifiers and batteries. Under normal conditions, the rectifier converts the mains power into 270V DC power to supply telecommunications equipment and charge the battery at the same time. In case of mains power failure, the battery discharges to supply power to the telecommunication equipment. In case of long-term mains power failure, the standby generator set shall supply power. As with the traditional - 48V DC power supply system, the battery standby time is 1 ~ 24h, and the typical battery standby time is 1 ~ 3H. The advantages of this high-voltage DC power supply system have been fully reflected in the trial.


Discussion on power supply mode of data center computer room

Advantages of this power supply system:

Reliability: the modular output of the power supply and the battery are directly connected in parallel to supply power to the load, the battery is directly connected in parallel to the output bus, and the bus power supply is uninterrupted. Hierarchical distributed control is adopted, and the rectifier module and CSU are controlled independently in case of fault to avoid fault diffusion.
Easy maintenance: easy parallel operation, modular power supply design, support with hot plug, easy replacement, hierarchical distributed control, rectifier module and CSU can be controlled independently for easy maintenance.
Intelligent management: like the traditional 48V DC power supply system, the system management adopts a comprehensive intelligent management mode; The management of the battery part is perfect, which effectively prolongs the service life of the battery.
No harmonic interference and easy capacity expansion: for computers and servers, DC input is adopted, which no longer has the problem of phase and frequency. Multi machine parallel connection becomes simple and easy without harmonic interference.
Safety: standard electrical cabinet is adopted to monitor the insulation status of shunt output and bus in real time, with high safety.
Cost performance: for the system with the same capacity, the high-voltage DC power supply system adopts n + 1 mode, which has low investment and high cost performance.
Disadvantages of this power supply system:
This power supply system requires DC special components; High requirements for device arc extinguishing; Due to the high voltage and no zero crossing, it has high requirements for safety.
7、 Solution 3 of HVDC power supply system
Scheme 3 of high voltage DC power supply system is similar to scheme 2. The difference is that the power supply system in scheme 3 adds a boost circuit to increase the DC output voltage to 400V (this similar power supply system has an experimental point in the mobile company, with a DC voltage of 350V). It is a special high-voltage server power supply. At present, this server is still under development. Due to the high output voltage of the system, some servers in use are unavailable, but due to some outstanding advantages, it may become a development trend in the future.
Advantages of power supply system of this scheme:
Modular power supply, battery directly connected to load, bus power supply uninterrupted; The highest power efficiency and the most energy-saving; The output is DC, without rate factor and harmonic problems, with maximum load capacity; The smallest power supply cable saves cost and space.
Disadvantages of the power supply system of this scheme:
The installation and removal of fault is easy to cause arcing; High requirements for safety and high requirements for devices.
The rapid development of telecommunication technology has promoted the progress of power supply equipment technology. Scheme 2 and scheme 3 of high voltage DC power supply system are especially suitable for IDC room power supply in occasions with high equipment power because of their high reliability and high efficiency. Scheme 2 is suitable for the current server and is also the most suitable scheme for the transformation of power supply in IDC room. Scheme 3 may be a development trend of equipment power supply in IDC room. What is the best power supply system in IDC room is still worthy of in-depth discussion and research, and finally a suitable scheme will be found.