With the rapid development of economy and the deepening understanding of network construction by grass-roots central banks, the construction and transformation of central computer rooms are in full swing in recent years. However, it is followed by an increasingly huge electricity bill and investment in the construction of the central computer room, in which electrical, power supply, refrigeration and other system facilities account for more than half of the investment. High power consumption makes the whole data center run at high cost, and the central computer room is facing the embarrassing situation of "building without using".
Reducing the operating cost and energy saving of the central computer room has become a concern of the relevant departments of the grassroots central bank. Energy saving can start from the following aspects. First, the energy-saving of the computer room environment, including refrigeration environment and power supply environment; Secondly, save energy from IT hardware equipment and reduce the energy consumption of IT equipment; Finally, the energy saving of integrated circuits in IT equipment, such as CPU, etc. UPS is the most important part of AC power supply, and almost all IT equipment in the computer room is powered by UPS, so it is imperative to improve the energy efficiency during operation. The energy saving of UPS must be carried out from various aspects such as scheme, battery and power distribution.
Second, flexible planning for capacity expansion on demand.
The construction of the general municipal center computer room is not in one step, and the demand in the next five to 10 years will be considered. UPS is generally in place in one step, and two sets of high-power UPS are installed in parallel at a time. Results the initial load was only 10% ~ 20% of the planned capacity, and the equipment was eliminated before the planned load. This not only wastes investment, but also can not make UPS run at a higher efficiency point, resulting in a waste of electric energy. How to avoid this situation, from the perspective of UPS power supply system, should include the following aspects.
(A) power supply scheme design
At present, UPS power supply schemes mainly include decentralized power supply and centralized power supply. Decentralized power supply is characterized by a UPS supplying power to one or more load devices. The advantage of decentralized power supply is that it disperses risks and will not cause large-scale power outage because of abnormal power supply of a UPS; The disadvantage is that UPS is distributed, which is inconvenient for management and wiring planning. The other is to use centralized power supply.
In this case, the high-power UPS power supply system directly supplies power to all loads in the computer room. The advantages of centralized power supply are convenient planning, management and maintenance; The disadvantage is that if the UPS system is abnormal, it is easy to cause large-scale power failure, which can be avoided by adopting various parallel architectures. Therefore, the above two schemes have their own advantages and disadvantages. At present, the centralized power supply scheme is widely used in the central computer room, which also concentrates the power supply risk. When the total installed capacity of UPS in the computer room exceeds a certain limit, it is suggested to divide the computer room into several areas for power supply according to several phases of planning.
(B) UPS online parallel extension function.
In the capacity planning of UPS in computer room, according to the demand of load capacity in different periods, the scheme of gradual expansion can be adopted, which makes the investment scheme more economical and makes UPS work at a better efficiency point. At present, UPS in medium and large power section has redundant parallel operation function, which not only improves the reliability of the system, but also provides conditions for the expansion of the computer room. As long as enough air switches are reserved in the distribution boxes before and after UPS and the corresponding space is planned in the computer room, the parallel expansion function of UPS can be realized. The key is the process of parallel operation. When multi-brand UPS is connected in parallel, the UPS settings need to be modified. At this time, UPS must work in the maintenance bypass state, and UPS is directly loaded by the commercial power. If the power supply fluctuates greatly or even loses power at this time, the system will be paralyzed in a large area. Therefore, parallel expansion must have online parallel function, that is, when UPS is in parallel expansion, it only needs to modify the new UPS software to make it consistent with the original UPS system, and directly merge the new UPS into the original system without shutting down the original UPS system. Before and after capacity expansion, UPS works in online mode to avoid high-risk operation of switching to bypass power supply.
(C) the use of modular UPS to achieve gradual expansion
At present, modular UPS has been applied in China. The characteristics of modular UPS mainly include: capacity expansion, short mean time to repair (MTTR) and "N+X" redundant parallel operation. Take Delta C series ~IJUPS as an example, each module is 20kVA, and the maximum capacity of the whole system can be increased to 160kVA, which can be gradually expanded according to the actual capacity requirements of the computer room, as long as the distribution capacity is planned in the initial stage of the computer room. At the same time, it is more cost-effective to realize "N+X" redundancy. For example, to realize the "N+I" redundancy with a capacity of 60kVA, the traditional scheme must extend a 60 kva module, while the modular UPS only needs to extend a 20kVA module, which saves a lot of money.
Third, improve UPS's own energy efficiency and optimize the load efficiency curve.
At present, UPS is an on-line double conversion structure, and both rectifier and inverter have power loss when working. Take a UPS with a capacity of 60kVA as an example. If the power consumption per kilowatt-hour is calculated as 1.2 yuan, the annual electricity saving will be 5045.76 yuan for every increase in UPS efficiency of 1%. It can be seen that improving the working efficiency of UPS can save a lot of electricity for the data center, and it is also the most direct way to reduce the energy consumption of the whole computer room. So try to buy a more efficient UPS.
Of course, the high efficiency of UPS is not only the high efficiency at full load, but also a high efficiency curve. Especially in the "1+ 1" parallel system, according to the system planning, the capacity of each UPS should not be greater than 50%. If the efficiency is only below 90%, even if the full-load efficiency is above 95%, it is meaningless, so UPS must take measures to optimize the efficiency curve.
In addition to improving the efficiency of UPS itself, some functions of UPS can be used. For example, in ECO economic operation mode, the principle is to activate this function in a good commercial power environment, so that UPS can be directly powered by static bypass. At this time, the inverter is in standby state and works normally but does not output energy. When the commercial power is abnormal, UPS will immediately switch to the inverter power supply state, and the switching time is generally within 1 millisecond. Because the inverter is in standby state, its own loss is very small, and the overall efficiency of UPS can reach ~ 1J at this time.
There are two conditions for using ECO mode: First, two sets of high-reliability thyristors must be used for static bypass, and the combination of contactor and thyristor is not allowed, because the contactor will strike a fire at the contact and work for hundreds of times, but the thyristor does not have this problem, and the switching time can be shortened. Second, it is recommended to use it in a better electricity environment, such as a first-class power supply unit.
Fourth, reduce the input current harmonics and improve the power factor.
The fundamental reason of harmonic generation is that the power line presents a certain impedance, which is equivalent to a passive network composed of resistance, inductance and capacitance. The non-sinusoidal current generated by nonlinear load distorts the current and voltage in the circuit, which is called harmonics. Harm of harmonics includes additional loss and heating of electrical components (such as capacitors, transformers, motors, etc.). ); The temperature rise of electrical components leads to low efficiency, accelerates insulation aging and reduces service life; Interfere with the normal operation of equipment; With the increase of reactive power, the active capacity of power equipment (such as transformers, cables and distribution equipment) decreases; Low power efficiency; Resonance occurs, especially when diesel generators generate electricity; No-load trip, fuse blown, equipment damaged without cause. UPS is a nonlinear load to the power grid, and it will produce a lot of harmonics when it works. Take UPS equipped with 6-pulse rectifier as an example, its input power factor is generally around 0.75, and the harmonic is greater than 30%. There are several main ways to reduce the harmonics of UPS32.
(1) 12 pulse rectifier
Its principle is to add a phase-shifting transformer and a 6-pulse rectifier on the input side on the basis of the original 6-pulse rectifier. After adopting this technical scheme, the harmonic can be reduced to about 10%. Its advantages are simplicity and obvious harmonic improvement. Disadvantages are limited improvement of power factor and slightly higher price.
(2) Passive filter
According to the principle of LC filter circuit, the harmonics generated by UPS are filtered and the power factor is compensated. Its advantages are simple process and low cost. The disadvantage is that it can only compensate the last harmonic, which is greatly affected by the load impedance and cannot be applied to the full power section.
(3) Active filter
Its principle is to inject a current with the same amplitude and opposite phase to the harmonic source current into the power grid by using controllable power semiconductor devices, so that the total harmonic current of the power supply is zero, and the purpose of compensating the harmonic current in real time is achieved. The advantages are that it can compensate multi-order harmonics and is not affected by load impedance; The disadvantage is the high purchase cost.
(4) Design of high frequency IGBT rectifier and PFC power factor correction circuit.
The principle of rectifier is to use high-frequency PWM to control IGBT conduction, divide the input voltage waveform, make the input current waveform as close as possible to sine wave, and compensate the phase difference between input voltage and current. Advantages are light volume, low price and good effect; Disadvantages are complex technical structure, difficult maintenance and limited current capacity affected by power devices.
Comparing the above technologies, performance and investment, we can choose a suitable scheme according to the actual needs.
Five, battery management and distribution management technology
UPS is equipped with batteries, and users' investment in battery packs often accounts for a large proportion of the investment in the whole UPS power supply system, even exceeding the investment of UPS itself, and the service life of batteries is obviously lower than that of UPS mainframe. Because the main materials of the battery are heavy metal lead, sulfuric acid and non-degradable plastics, it will cause serious pollution to the environment. Therefore, reducing the number of batteries and prolonging the cycle life of batteries not only saves direct and indirect battery investment, but also reduces the environmental pollution caused by the equipment in the whole computer room. Therefore, UPS can save energy through the following technologies.
(a) parallel battery function
* * * The principle of using battery pack is to isolate faults through a special rectifier, so that two or more UPS rectifiers in parallel system can be synchronized, and the buses can be current-shared, so that all UPS buses in the system can be directly connected in parallel, and then the batteries that meet the requirements of system standby time can be connected in parallel to the parallel bus system, so as to realize the enjoyment of batteries and reduce battery investment. Take "1+ 1" as an example. In the traditional UPS scheme, the system is backed up for one hour. When a UPS fails, the battery of UPS2 cannot be used for UPS 1. Therefore, UPS 1 and UPS2 must each be equipped with a battery pack of -4 hours to ensure that the system can be backed up for one hour after power failure. After adopting the * * * battery pack scheme, because the batteries in the system can still provide energy for UPS2 after UPS 1 fails, the whole system only needs to be equipped with one set of batteries for one hour. This not only saves the direct investment of batteries, but also saves the space, load bearing and air conditioning investment of the computer room, and also reduces the pollution to the environment.
(B) Intelligent battery management technology
There are many factors that affect the battery life, including temperature, charging, discharging, cycle times and so on. If the above factors can be comprehensively dealt with, the service life of the battery can be greatly prolonged, the battery replacement cycle can be prolonged and the battery investment can be saved. UPS's intelligent battery management includes: battery uniform floating charge management (uniform floating charge control), intelligent discharge termination voltage control during charging, in addition to power detection and battery leakage detection functions. In addition, UPS with wide voltage range can be selected to reduce battery discharge times. Through the above technology, the battery life can be greatly prolonged by 2-3 years.
(C) Intelligent UPS power distribution management technology
The principle is that by detecting the voltage or management time of UPS battery, the power-off protection function of different grades of loads in the computer room can be realized many times, so as to reduce battery investment and improve battery utilization. There are two main schemes for intelligent UP technology: software implementation and hardware implementation. Take Delta UPS as an example, its software mode is to install Deltashutd0wnAgent shutdown agent on the load server when UPS is monitoring. When the mains power supply is abnormal and meets the battery voltage or timing conditions, the system program will be automatically saved, and then the server will be shut down.
The hardware mode is that the UPS output is equipped with intelligent power distribution panel, and the battery voltage or timing requirements of UPS are detected by PLC. When the above conditions are met, the intelligent power distribution panel turns off a certain output in time-sharing according to the setting. At present, the scheme has been applied in UPS power supply systems of several subways in China.
Ending of intransitive verbs
The central green data center must start from top to bottom, or from infrastructure to core equipment. UPS is the core of the whole AC power supply link. Doing a good job of UPS energy saving can not only save a lot of equipment investment and maintenance costs, but also greatly reduce the later operating costs.