UPS (Uninterruptible Power Supply) is an uninterruptible power supply with energy storage device. It is mainly used to provide uninterruptible power supply for some equipment requiring high power supply stability.
When the mains power input is normal, the UPS will supply the mains power to the load after it is stabilized. At this time, the UPS is an AC electric voltage stabilizer, and it also charges the battery in the machine; When the mains power is interrupted (emergency power failure), UPS will immediately supply 220V AC power to the load through inverter switching, so that the load can maintain normal operation and protect the load software and hardware from damage. UPS equipment can usually provide protection against over voltage or under voltage.
Uninterrupted Power Supply (UPS), a foreign language name, refers to UPS application communication, power, finance, petroleum, military and other classified double conversion, online interactive, passive backup functions to provide a stable and uninterrupted power supply
Uninterruptible power supply (UPS) is a system equipment that connects batteries (mostly lead-acid maintenance free batteries) with the host, and converts DC power into mains power through the inverter and other module circuits of the host. It is mainly used to provide a stable and uninterrupted power supply for a single computer, computer network system or other power electronic equipment such as solenoid valve, pressure transmitter, etc., to ensure the uninterrupted operation of these equipment and instruments, and to prevent computer data loss, telephone communication network interruption or instrument loss of control.
UPS is widely used in mines, aerospace, industry, communications, national defense, hospitals, computer business terminals, network servers, network equipment, data storage equipment, emergency lighting systems, railways, shipping, transportation, power plants, substations, nuclear power plants, fire safety alarm systems, wireless communication systems, program-controlled switches, mobile communications, solar energy storage energy conversion equipment, control equipment and their emergency protection systems Personal computers and other fields.
(1) When the mains power is normally supplied within the range allowed by the UPS, the thick line depicts the flow direction of the power supply energy.
(2) After the main power failure, i.e. the mains power is cut off, the power supply will be switched to the inverter to provide energy instantaneously, as shown in Figure 3.
(3) When the load is too large or the inverter in the power supply fails, the UPS will turn on the bypass circuit to supply power directly from the main power supply
(1) A single UPS power supply can supply all loads, and the connection method is simple.
(2) The total load power needs two or more UPS power supplies. This connection mode is called parallel connection without backup.
(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.
(4) After the failure of the entire UPS power supply system, the mains will disconnect the UPS power supply and directly connect the load without affecting the maintenance of the UPS power supply system.
When there is no fault in the UPS power system, the maintenance switch is opened, and the input switch and output switch are closed; When the UPS power system fails, the maintenance switch is closed, and the input switch and output switch are opened. In this way, the normal operation of the electrical load is ensured without affecting the online maintenance of UPS power supply system faults.
With the increasing requirements of computer application systems on power supply, UPS has been paid more and more attention, and gradually developed into a power protection system with the functions of voltage stabilization, frequency stabilization, filtering, anti electromagnetic and radio frequency interference, anti voltage surfing, etc. Especially when the line and power supply quality of the power grid is not high, the anti-interference technology is backward, and the computer system has high requirements for power supply, the role of UPS is more obvious.
The protection function of UPS is to stabilize the voltage of mains power supply. The input voltage range of UPS is relatively wide, generally from 170V to 250V, while the quality of output power supply is quite high. The output voltage of backup UPS is 5%~8%, and the output frequency is stable at 1Hz; As shown in Figure 1, the output voltage of the online UPS is stable within 3% and the output frequency is stable at 0.5Hz. When the mains power is normal, the UPS power supply is equivalent to the AC mains voltage stabilizer; 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 will automatically switch to battery power supply to keep the computer working normally and protect software and hardware from damage.
According to the new standard IEC (International Electrotechnical Commission), UPS is divided into the following three categories according to its structure and operation principle:
(1) Passive backup UPS power supply
Uninterruptible power supply
Uninterruptible power supply
It means that the inverter is connected in parallel between the mains and the load and is simply used as a backup power supply. 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.
Passive backup UPS has the advantages of simple structure and the lowest price. It is used for some non important loads, such as home computers. However, when the mains power is cut off, the relay will switch the inverter to the load. The switching time is long, and it usually requires several milliseconds of interruption. Therefore, the passive backup UPS power supply should not be used for slightly important computer equipment.
(2) Online interactive UPS power supply
It means that the inverter is connected in parallel between the mains power and the load, acting as a backup power supply, while the inverter serves as a charger to charge the battery. It interacts with the mains through the reversible operation mode of the inverter, so it is called interactive. When the mains power is normal, the load is powered by the improved mains power, and the inverter acts as a charger to charge the battery. At this time, the inverter acts as an AC/DC converter; In case of mains power failure, the load is completely supplied by the inverter. At this time, the inverter acts as a DC/AC converter.
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 particularly suitable for systems where some computer equipment in the network uses distributed power supply. The disadvantage of this power supply is that its voltage stabilization performance is not high, especially its low dynamic response speed. Secondly, its anti-interference ability is not strong, and the circuit will generate harmonic interference and modulation interference.
(3) Dual conversion UPS power supply
The inverter is connected in series between the AC input and the load, and the power supply continuously supplies power to the load through the inverter. The power supply mode of this UPS power supply is as follows: when the mains power is normal, the mains power supplies the load through the rectifier and inverter; When the mains power is abnormal, the load is supplied by the accumulator through the inverter.
Dual conversion UPS is the mainstream product of UPS power supply. It has the advantages of good performance, high voltage stability and frequency stability, strong function, hot backup connection and parallel redundant connection. Its disadvantage is that when the capacity is less than 10kVA, the overall efficiency is not high, generally about 85%.
Editing and broadcasting of technical indicators
Most of the inverters in the new UPS use PWM technology, and quartz crystal oscillation is used to control the frequency of the inverter. The voltage negative feedback circuit ensures the stability of the output voltage. It has a series of advantages of switching power supply. By precisely adjusting the pulse width, it can ensure stable power output. At the same time, the application of switching power supply technology can greatly reduce its own loss. The main technical indicators are as follows:
(1) Rated output power and maximum output power;
(2) Switching time;
(3) Output voltage stability, reference value ± 0.5%~± 2%;
(4) Output frequency stability, reference value ± 0.01%~± 0.5%;
(5) The output waveform is pure (sine wave output), the voltage distortion is less than 1%, and there is no hidden wave distortion;
(6) High efficiency and low loss. The reference index is higher than 90%;
(7) Fault free working time. Due to the adoption of microprocessor monitoring technology and advanced IGBT driven SPWM and other high technologies, the current UPS has reached a very high level of reliability. For large UPS power supplies, the annual mean time between failures (MTBF) of a single unit has exceeded 200000 hours. If the multi machine "redundant" UPS power supply system with dual bus output is adopted, its MTBF can even reach the order of 10 million hours.
(1) UPS adopts modular online parallel expansion function. At present, most UPS in high-power section have the redundant parallel operation function. The redundant parallel operation of multiple modules in the ups, or even the system redundancy operation technology composed of multiple UPS, in parallel operation, when a single module or a single unit fails, its functions are automatically transferred to the redundant unit, which greatly improves the reliability of the UPS power supply system.
(2) High efficiency and high reliability. Improve UPS energy efficiency, optimize load efficiency curve, reduce input current harmonics, and improve power factor.
(3) Digital and intelligent UPS.
(4) UPS is green, energy-saving and environmental friendly. Energy conservation and environmental protection have become the guiding principle of UPS product technology innovation. For UPS, the input power factor indicates its ability to absorb the active power of the grid and the extent of its impact on the grid.
Notes Edit Broadcast
Because of the particularity of its inverter and storage battery, the installation and use of UPS power supply must have a set of strict and scientific operating procedures to improve the working stability, reduce equipment failure rate, and truly achieve uninterrupted power supply of equipment.
(1) The installation environment of UPS power supply shall be free from direct sunlight, and sufficient ventilation space shall be reserved to keep the temperature of working environment not higher than 25 ℃. If the working environment temperature exceeds 25 ℃, the battery life will be shortened by about half for every 10 ℃ increase in temperature.
(2) It is not suitable to use high-power silicon controlled load, silicon controlled bridge rectifier or half wave rectifier load at the output end of UPS power supply. Such load may easily cause the final drive transistor of inverter to be burnt.
(3) The operation shall be carried out in strict accordance with the correct startup and shutdown sequence to avoid large fluctuation of UPS voltage output due to sudden increase or decrease of load, which will make UPS unable to work normally.
(4) It is prohibited to turn off and turn on the UPS power frequently. Generally, it is required to wait at least 30 seconds after turning off the UPS power. The reason for the high frequency of failures of small and medium-sized UPS power supply is that the user frequently starts or shuts down, and the UPS power supply carries the load to switch between inverter power supply and bypass power supply.
(5) Practice has proved that for most UPS power supplies, it is the best way to control the load within the range of 50%~60% of the rated output power. Overload use 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 triode will often be broken down under the inverter state. It is not suitable to operate with excessive light load, which is easy to cause battery failure due to too small battery discharge current.
(6) Regularly maintain the UPS power supply: observe the status of the work indicator light, remove dust, measure the battery voltage, replace unqualified batteries, check the fan operation, detect and adjust the system parameters of the UPS, etc.
(7) UPS power supply is more suitable for micro capacitive load, not for charged inductive load, such as air conditioner, motor, electric drill, fan, etc. If the UPS power load is resistive or inductive, the load must be reduced as appropriate to avoid overload operation.