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USP power supply system of " high availability " requirements the system must have the function, reliability, maintenance and fault tolerance of four elements, while the UPS internal topology on the reliability of the system and function of play a decisive role. The availability of key elements, especially the maintenance and fault tolerance, largely depends on the UPS redundancy and the choice of distribution system, the UPS internal different topological structure is analyzed and evaluated, shows a structure how to " high availability " power system four factors affect the.
A, UPS topology: off-line UPS or backup power ( SPS )
Off-line topology is one of the most simple UPS structure. Under the conditions of normal operation, AC power directly through the UPS until the important load. The charger or the " 4 quadrant converter " converts alternating current into direct current to charge the battery. Inverter for direct current supplied by the battery is converted into alternating current, when the power fails to supply power for the load. The inverter is usually run in the standby mode, keep the battery charging. If the city electricity exceeds the prescribed scope, an inverter by battery power to the load. The topological structure is known as the " single transformation ", because at any given time, power supply converting only once (AC into DC or DC to AC ). Under the conditions of normal operation, a small amount of the alternating current into direct current, maintain the battery power supply. Input power is outside the specified range, UPS detects a power failure, the switching relay action, output inverter starting the inverter will be supplied by the battery converted into AC DC, power to the load.
An off-line UPS price is very low, only suitable for home or to need only implement power-off protection application of single computer workstation power supply situation. Sometimes the off-line product built-in surge suppression and / or " buck and boost " circuit, compensation of higher or lower input voltage, but does not attempt to provide any valid input power regulation.
An off-line UPS simple in design of higher scores, whereas in other measuring slightly lack of respect. An off-line UPS generally used for single phase non essential load. In particular, is not compatible with generators and other shortcomings, so that it does not apply to three-phase application.
In two, UPS topology: an interactive UPS
Interactive UPS topology structure. The structure and off-line UPS similar products, is different in the electric power supply and load in accordance with series transformer or inductor structure in. The inductor UPS inverter with input power " interactive ", and is connected to the output load power regulation. That is to say when the input voltage is higher and lower case, " buck and boost " circuit capable of performing the corresponding regulation.
Four quadrant converter is generally constant pressure device. A load or an input voltage changes, the four quadrant converter by adjusting the output phase angle, make corresponding changes. Load frequently changing, will result in the discharge of the battery, the battery s frequent discharge will greatly shorten its service life.
Interactive UPS product of another shortcoming is that, if you do not use the battery power supply, will not be able to complete the important load and input power to achieve isolation. Frequency perturbation and power quality is poor, will directly affect the important load. If the implementation is electrically isolated, common-mode noise will directly affect the normal work load.
Interactive UPS product of another shortcoming is that, if you do not use the battery power supply, will not be able to complete the important load and input power to achieve isolation. Frequency perturbation and power quality is poor, will directly affect the important load. If the implementation is electrically isolated, common-mode noise will directly affect the normal work load.
And off-line UPS identical, interactive UPS product prices may be low, and the efficiency is high, reason is, it is only in the input power is abnormal to important load power supply, and only in the battery work during operation. Compared with off-line UPS, interactive UPS equipment because of its series inductor and a power regulation function in terms of efficiency, some loss. In addition, when the UPS conversion for battery power supply, usually there will be at least a little ( but measurable ) voltage drop.
Generator compatibility
An off-line UPS and interactive UPS products need to input power frequency and phase stability. Power frequency must be stable, because the inverter must track power supply frequency, to calibrate the voltage and current, this system can output frequency and the input frequency is same, unless the UPS through the battery operation.
Compared with the typical problems when start the generator on the other load, generator output frequency will produce very big change, resulting in an off-line UPS or interactive UPS through the battery discharge. The problems on natural gas power generation unit is obvious. Battery charging, is likely to lead to a battery, it will greatly shorten the battery life. Another potential problem is the UPS load load, the output of the generator can be unstable, that is to say the UPS load sudden, causes the generator voltage and frequency drop, leading to UPS into the battery discharge condition. When the output of the generator stability after, UPS returned to normal state, if the generator output voltage drop again, UPS will once again into the battery discharge state.
For double conversion UPS does not appear afore-mentioned problems. Double conversion UPS to adjust the input power, and can allow the power frequency appears bigger change, while continuing to provide a stable output frequency, without the use of battery power supply. Moreover, double conversion UPS major manufacturers have developed to reduce output current distortion technology, greatly improve the compatibility of UPS and generator, so that the load size selection is more accurate. Double conversion UPS capacity and the generator capacity ratio can reach 1.25~1.5:1, not running problem.
In three, UPS topology: having power factor correction function in linear interactive structure ( including " Delta transform " products )
In recent years, several companies launched with power factor correction function of online interactive three-phase UPS products. And off-line product and general interactive products, these products have improved power control performance, increase the output of the power supply quality. But it has also produced some adverse factors, such as active power adjustment reduces the efficiency of. In fact, in with nonlinear load (usually a computer load ), the efficiency is lower than the double conversion UPS products. And the complexity of product structure with respect to the double conversion UPS is often go beyond. And as easy to mislead the user is, the types of online interactive products was even billed as " in-line " products, because the inverter always "run", which provides voltage regulation or input power factor correction.
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