Uninterruptible Power SupplyEnergy storage deviceUninterruptible power supply for.It is mainly used to provide uninterruptible power supply for some equipment requiring high stability of power supply.[1]
WhenMains electricityWhen the input is normal, UPS supplies the mains voltage toloadWhen used, the UPS is an AC power supplypressure regulatorAt the same time, it alsocharge；When the mains power is interrupted（Accident power failure）The UPS immediately transfers the DC power of the battery through theinverterContinue to supply 220V to the load by switchingalternating currentTo keep the load working normally and protect the load software and hardware from damage.UPS equipment is usually sensitive to high voltage orVoltage too lowCan provide protection.[1]
(1) When the mains supply is normal within the allowable range of the UPS, as shown in Figure 2, the thick line depicts the flow direction of the power supply energy.[3]
（2）Main power supplyThe fault is that after the mains power is cut off, the power supply will be switched to the inverter to provide energy in an instant, as shown in Figure 3.[3]
(3) When the load is too large or the inverter in the power supply fails, the UPS will turn on the bypass to supply power directly from the main power supply, as shown in Figure 4.[3]
Connection mode
Figure 7
(1) A single UPS power supply can supply all loads. The connection diagram is shown inschematic diagramThe connection method is simple.[3]
(2) The total load power needs two or more UPS power supplies, as shown in Figure 5Connection modeIt is called parallel connection withoutBackup mode。[3]
(3) The total capacity of two or more UPS power supplies is more than the total load capacity, but the system must have the capacity of one more UPS power supply than the total load capacity. When any one UPS power supply fails, the rest can still supply all loads, as shown in Figure 6.This connection mode is called parallel backup mode.[3]
(4) When the whole UPS power supply system fails, the mains will disconnect the UPS power supply and connect the load directly without affecting the maintenance of the UPS power supply system. This circuit design is shown in Figure 7.[3]
When there is no fault in the UPS power supply system, the maintenance switch is opened, and the input switch and output switch are closed;When UPS power supplysystem failure When the maintenance switch is closed, the input switch and output switch are open.In this way, the normal operation of the electrical load is ensured without affecting the online maintenance of UPS power system faults.[3]
Function
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Figure 1 Schematic Diagram of Online UPS
With the computerapplication systemThe requirement for power supply is getting higher and higher, and UPS has gradually developed into a power supply with voltage stabilization, frequency stabilization, filtering, electromagnetic resistance andRF interference, anti voltage surfing and other functionsprotection system 。Especially in the lines andPower supply qualityNot too high, the anti-interference technology is backward, andcomputer systemIn the case of high requirements for power supply, the role of UPS is more obvious.[4]
The protection function of UPS is firstly shown in itsMains electricityPower supply for voltage stabilization, UPSInput voltage rangeIt is relatively wide, generally from 170V to 250V, and the quality of output power supply is quite high. Backup UPSoutput voltage At 5%~8%, outputFrequency stabilityAt 1Hz;As shown in Figure 1, online UPS outputVoltage stabilityWithin 3%, the output frequency is stable at 0.5Hz.When the mains power is normal, the UPS power supply is equivalent to the AC mains power supplypressure regulator；At the same time, the mains charge the battery, which is also equivalent to the charger.In case of sudden power failure of mains power, UPS automatically switches toBattery power supplyTo keep the computer working normally and protect the software and hardware from damage.[4]
classification
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UPS according to new standard IEC（International Electrotechnical Commission）According to its structure and operation principle, it can be divided into the following three categories:[5]
Refers to that the inverter is connected in parallel between the mains and the load simply asemergency power supplyuse.When the mains power is normal, the load is completely and directly supplied by the mains power, the inverter does not do any power conversion, and the battery is powered by an independent charger;When the mains power is abnormal, the load is completely powered by the inverter.[5]
passiveBackup UPSIt has the advantages of simple structure and the lowest price, and can be used for some non important loads, such as home computers.However, when the mains power is cut off, the relay switches the inverter to the load, which takes a long time and usually requires several milliseconds of interruption. Therefore, the passive backup UPS power supply should not be used for slightly important computer equipment.[5]
(2) Online interactive UPS power supply
It means that the inverter is connected in parallel between the mains and the loadBackup power supplyAt the same time, the inverter acts as a charger toBattery charging。Through the reversible operation mode of the inverter, it interacts with the mains, so it is called interactive.When the mains power is normal, the load is powered by the improved mains power, and the inverter is used as the charger to charge the batteryAC/DCConverterThe role of;When the mains power fails, the load is completely powered by the inverter,inverterIt functions as a DC/AC converter.[5]
The online interactive UPS has the advantages of simple structure, convenient implementation, easy parallel connection, easy maintenance and repair, high efficiency, low operating cost, high reliability of the whole machine, etc. Its performance meets some load requirements, and is especially suitable for some computer equipment in the networkDistributed power supplySystem.The disadvantage of this power supply is that its voltage stabilizing performance is not high, especially dynamicresponse speedLow, nextAnti interference capabilityNot strong, the circuit will produceHarmonic interferenceAnd modulation interference.[5]
(3) Dual conversion UPS power supply
Refers to the inverter connected in series between AC input andloadThe power supply continuously supplies power to the load through the inverter.This UPS power supplyPower supply modeAs follows: When the mains supply is normal, the mains supply power to the load through the rectifier and inverter;When the mains power is abnormal, the load is powered by the accumulator through the inverter.[5]
Dual conversion UPS is the mainstream product of UPS power supply, with good performanceVoltage stabilityAndFrequency stabilityHigh performance, strong function, hot standby connection and parallel redundant connectiondeficienciesWhen the capacity is less than 10kVA, the overall efficiency is not high, generally about 85%.[5]
Technical indicators
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Most inverters in the new UPS usePWM technology, while adoptingquartzThe frequency of the inverter is controlled by the crystal oscillation, and the output voltage is stable through the voltage negative feedback circuit.It has a series of advantages of switching power supplypulse widthThe application of switching power supply technology also greatly reduces its own loss.mainTechnical indicatorsAs follows:[3]
(6) High efficiency and low loss.The reference index is higher than 90%;[3]
（7）Fault free working time。becausemicroprocessorMonitoring technology and advancedIGBTDrive typeSPWMWith the adoption of advanced technology, the current UPS has reached a very high level of reliability. For large UPS power supply, the average annual trouble free working time of its single machine（MTBF）More than 200000 hours.If multiple "redundant" UPS with dual bus output is adoptedpower supply systemIts MTBF can even reach 10 million hoursOrder of magnitude。[3]
Development characteristics
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(1) UPS adopts modular online parallel expansion function.At present, most of the UPS in the high-power section have the redundant parallel operation function, and the UPS has multiple module redundancyparallel operation , or even multiple UPSSystem redundancyOperation technology: in parallel operation, when a single module or single machine fails, its functions will be automatically transferred to the redundant unit, greatly improving the UPS power supplySystem reliability。[1]
(2) High efficiencyhigh reliability。Improve UPS energy efficiency, optimize load efficiency curve, reduce input current harmonics, and improvepower factor 。
(3) Digital and intelligent UPS.[1]
(4) UPS is green, energy-saving and environmentally friendly.Energy saving and environmental protectionIt has become the guiding principle of UPS product technology innovation.For UPS,Input powerThe high or low of the factor indicates that it absorbs the power gridActive powerAnd the degree of impact on the power grid.[1]
matters needing attention
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Because of the particularity of its inverter and storage battery, the installation and use of UPS power supply must have a strict and scientificOperating ProceduresIn order to improve working stability and reduceEquipment failure rate, truly achieve uninterrupted power supply of equipment.[6]
(1) The installation environment of UPS power supply shall avoid direct sunlight, and sufficient ventilation space shall be reserved to keep the temperature of working environment not higher than 25 ℃.If workingambient temperatureOver 25 ℃, everytemperature riseIf the temperature is increased by 10 ℃, the battery life will be shortened by about half.[6]
(2) It is not suitable to use high power at the output end of UPS power supplySilicon controlled rectifierLoad, thyristorBridge rectifierOr half wave rectifier load, which is easy to cause final drive of invertertransistorBurned.[6]
(3) The operation shall be carried out in strict accordance with the correct startup and shutdown sequence to avoid the large fluctuation of the UPS voltage output due to the sudden increase or decrease of load, which will make the UPS unable to work normally.[6]
(4) It is forbidden to turn off and turn on the UPS frequently. Generally, it is required to wait at least 30 seconds after turning off the UPS power before turning on the UPS power.The reason for the frequent failure of small and medium-sized UPS power supply is that the user frequently starts or shuts down the UPS power supply with load to supply power to the inverter andbypassPower supply switching period.[6]
（5）Practical proof: For most UPS power suppliesloadControl at 50%~60%Rated output powerScope is the best way to work.Overload is prohibited. The manufacturer recommends that the maximum starting load of the UPS power supply should be controlled within 80%. If it is overloaded, the inverter will often be broken down under the inverter statetriode。It is not advisable to operate with excessive light load, which is easy to be caused by the batterydischarge current Too small causes battery failure.[6]
(6) Regular maintenance of UPS power supply: observationindicator lightStatus, dust removal, measurement of battery voltage, replacement of unqualified batteries, inspection of fan operation, detection and regulation of UPSsystem parameterEtc.[6]
(7) UPS power supply is more suitable for micro capacitive load, not suitable for electrificationinductive load , such as air conditioner, motorElectric drill, fan, etc.If the UPS power load is resistive or inductive, it must be reduced as appropriateLoadAvoid overload operation.[6]
