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October 18, 2017
There are two main functions of UPS:
1.When the power supply is normal, the quality of the power supply is improved, and the backup battery is charged;
2.In the event of abnormal power supply, the backup battery to ensure uninterrupted power supply to the load.
At present, the energy saving of UPS must be carried out from the aspects of scheme, UPS, battery and power distribution.
Flexible planning for capacity expansion on demand
The construction of data center is not in one step, it will consider expansion in the next few years, in the design of UPS capacity are generally considered relatively large capacity, installed several sets of high power UPS at one time, At initial stage, the charge capacity is only 10% to 20% of capacity planning, so that the utilization rate of UPS very low, and resulting in a waste of electricity. How to avoid this situation, from the angle of UPS power supply system, it should include:
1. Power supply scheme design
At present, the UPS power supply scheme mainly has two kinds of decentralized power supply and centralized power supply. Decentralized power supply is a UPS power supply for one or more devices. The advantage of decentralized power supply is to disperse the risk, It doesn't cause most of the devices blackouts when a UPS abnormal; the disadvantage is that UPS decentralized layout, not convenience to management, and wiring is not easy to plan. The other is centralized power supply, which is powered by a set of high power UPS directly to all the loads in the data center. The advantage of centralized power supply is easy planning, convenient management and convenient maintenance. The disadvantage is that if the UPS system is abnormal, it is easy to cause large area blackout accident in data center, and this shortcoming can be avoided by adopting parallel frame.
Therefore, the above two schemes have their own advantages and disadvantages, and at present , the data center generally adopts centralized power supply scheme. Due to the number of UPS parallel machines is limited, the reliability is not higher than the single power supply system when the number of UPS systems is more than 4 units. When the total installed capacity of UPS in the computer room exceeds a certain limit, it is suggested that the engine room be divided into several areas according to several stages of planning to supply power. When you planning it you can refer to single capacity should not exceed 400kVA, and the number of machines should not exceed 3 units.
2.UPS online parallel expansion function
The UPS capacity planning of the data center can be carried out according to the load capacity requirements of different periods, and the gradual expansion scheme is adopted to make the investment scheme more economical, and it also make the UPS worked reach a better efficiency point. At present, the UPS in the middle and high power section has the function of redundant and parallel, which not only improves the reliability of the system, but also provides the conditions for the expansion of the computer room. As long as the plan is reserved enough air switch before and after UPS, and the corresponding space is planned in the computer room, the function of UPS parallel expansion can be realized. The key is to the treatment process of parallel machine, UPS machine and a variety of brands need to set the UPS amendment, which requires UPS must work in maintenance bypass state, UPS directly by electric load, if the city power is large even blackout, it will cause a large area of paralysis of the system. So it must have the expansion machine online and machine function, that’s to say UPS and machine capacity expansion, it just need to be added to the original UPS and UPS software to modify the system after the agreement, Under the condition of direct UPS without closing the original UPS system will be added into the original system, it makes expansion before and after, UPS work in line mode. To avoid the high risk operation switch to bypass power supply.
3. Modular UPS is used to realize gradual expansion
At present, modular UPS has begun to be applied in China, and modular UPS features include: scalable, average fault repair time (MTTR) is short, the economic implementation of "N+X" redundant parallel machine. In the micro Bo BWM series module electric machine efficiency is higher than 95%, the strength of the industry's leading energy saving; all modules support hot plug, online expansion, maintenance, customers can greatly save maintenance cost, bring better commercial value.
Improve UPS energy efficiency and optimize load efficiency curve
At present, UPS is an on-line dual converter architecture, and there is power loss in the rectifier and inverter when it works. For example,a UPS with capacity of 400kVA, the electricity is calculated at 0.95 yuan per kilowatt hour, and the UPS efficiency is increased by 1% per kilowatt hour, and the annual electricity savings are 400 x 0.8 x 0.01 x 24 x 365 x 0.95=26630.4 yuan per year,.Therefore, improving the efficiency of UPS can save a lot of electricity for the data center. Therefore, improving the efficiency of UPS is the most direct way to reduce the energy consumption of the whole computer room. Therefore, the procurement of UPS, as far as possible procurement of higher efficiency of UPS.
Of course, UPS is not only high efficiency with high efficiency,but also have a high efficiency curve, especially in the "1+1" system, according to system planning, each UPS capacity of not more than 50%, if the efficiency is only 90%, even with more than 95% efficiency, that is no significance, So UPS must take measures to optimize the efficiency curve, the efficiency of the UPS can achieve a higher efficiency in low load.
In addition to improving the efficiency of UPS itself, some of the functions above UPS can also be used. Like ECO's economic operation model. The principle is in the electric environment better, to activate this function, the UPS powered directly by static bypass, the inverter is in standby state and work normally, but it can not output power, once the city power is abnormal, UPS immediately switch to the inverter power supply, switching time is generally within 1ms, the overall efficiency of UPS can be more than 97%, save more than 3% power than in normal mode.
Reduce input current harmonic and improve power factor
The fundamental cause of harmonic generation is that the power line presents a certain impedance, which is equivalent to the passive network composed of resistors, inductors and capacitors. The non sinusoidal current produced by the nonlinear load causes the distortion of the current and voltage in the circuit, it called harmonic. The harm of harmonic caused by electrical components including: additional loss and heat (such as capacitors, transformers, motors and so on); the electrica components rise higher，low efficiency, accelerate the insulation aging, reduce the service life; the equipment cna work normally; reactive power increases, the power equipment of active capacity reduced (such as transformers, cables, power distribution equipment); the efficiency is low; the occurrence of resonance, especially the diesel generator is more serious; circuit breaker tripping, fuse, equipment without damage. UPS is a nonlinear load for the power grid, and generates a large amount of harmonics at the time of operation. Taking UPS with 6 pulse rectifier as an example, the input power factor is generally about 0.75, and the harmonic is greater than 30%. There are some main methods to reduce the working harmonics of UPS:
1. Adopt 12 pulse rectifier. The principle is to add a phase-shifting transformer and a 6 pulse rectifier on the input side based on the original 6 pulse rectifer. After adopting the technical scheme, the harmonic can be reduced to about 10%. The advantage is relatively simple, the harmonic is improved obviously, the disadvantage is that the power factor is limited and the price is slightly higher.
2. Adopt passive filter. According to the principle of LC filter circuit, the harmonic produced by UPS is filtered, and the power factor is compensated. The advantage is that the technology is simple and the cost is low; the disadvantage is that it can only compensate the characteristic order harmonics, and is affected by the load impedance greatly, so it can not be applied to the full power section.
3.Adopt active filter. The principle is to use the controllable power semiconductor device to inject the current equal to the amplitude of the harmonic source and the opposite phase to the power grid, so that the total harmonic current of the power supply is zero, and the harmonic current can be real-timecompensated. The advantage is that it can compensate multiple orders of harmonics, and is not affected by the magnitude of the load impedance; the disadvantage is that the cost of purchase is higher.
4. Using high frequency IGBT rectifier and PFC power factor correct circuit the design of rectifier. The principle is that the IGBT is controlled by high frequency PWM, and the input voltage waveform is segmented so that the input current waveform is close to the sine wave, and the phase difference between the input voltage and the current is compensated. The advantages are light weight, low price and good effect. The disadvantage is that the technical structure is complex, and it is difficult to maintain and it is affected by the power device, and the capacity is limited.
Battery management and distribution management technology
UPS is equipped with a battery pack, the user's investment in the battery pack often accounts for a large part of the UPS power supply system investment, even more than the UPS itself investment, and the battery life is significantly lower than the UPS device. Because of the main materialsof the battery are heavy metal lead, sulfuric acid and not easy to decompose plastic, it will cause serious pollution to the environment. Therefore, to reduce the number of batteries and extend the cycle life of batteries, it not only to save direct and indirect battery investment, but also to reduce the whole environmental pollution. So UPS can save energy through the following technologies.
1. Parallel battery sharing function. Common battery principle is through special rectifier control and fault isolation technology, and make the machine system in two or more UPS rectifier synchronization, parallel flow, each the bus of UPS is directly in parallel in the system, and then meet the system requirements of the parallel battery backup time after connected in parallel bus system. Sharing the battery, reduce the battery investment. Take "1+1" as an example, the traditional UPS scheme, system backup for an hour, consider the fault of a UPS, the battery of UPS2 cannot be used for UPS1, so UPS1 and UPS2 must be the configuration of a one hour battery, it can be protect the system in power for an hour. After using the common battery pack scheme, because the UPS1 fault, the battery in the system can still provide energy for the UPS2, so the whole system only need to configure 1 sets of 1 hours battery. It not only saves the battery direct investment, but also saves the investment of the computer room in the space, load bearing and air conditioning, and reduces the pollution to the environment. A battery or generator with configuration.
2. Smart battery management technology. There are many factors affecting the battery life, including temperature, charging, discharge, cycle times, etc.. If those factors can be comprehensively treated, the service life of the battery can be greatly prolonged, the battery replacement cycle can be prolonged, and the battery investment can be saved. Intelligent battery management technology of UPS mainly include: battery float management (all float control), temperature compensation charging, intelligent discharge termination voltage control, in addition to the battery should have regular automatic detection and battery leakage detection function. In addition, the UPS with wide input voltage range can be selected to reduce the battery discharge times. Through these techniques, the battery life can be greatly extended for 2~3 years.
3. Intelligent UPS power distribution management technology. The principle is to detect the UPS battery voltage or manage the power supply time of the equipment, so as to realize the multiple power protection function of different levels of load in the computer room, reduce the battery investment and improve the battery utilization. Intelligent UPS power distribution management technology has two main solutions: software implementation and hardware implementation.