COMPENSATION OF REACTIVE POWER AND HYBRID OPERATION IN THE SYSTEMS OF UNINTERRUPTIBLE POWER SUPPLY (UPS)
Taking into account common use of electric and electronic parts, devices, and systems in all the areas of human activity, both in private and professional realm (science, industry, administration, services, etc.), the problems related to the quality of delivered power and to reasonable power management become very important.
The faults or interruptions in electric power delivery are not only burdensome to the users, due to precluded operation of the electric equipment, but may be conducive to severe consequences. These consequences may be of economic, technological, and information nature, in the form of data loss in computer systems, damage to electric equipment, expensive shutdowns of the equipment operation, or the discomfort related to insufficient heating of usable premises (mainly in winter) or operation of the access control devices (automatic gates, the parts of intelligent buildings, alarm systems etc.).
A good solution to such problems is the use of a guaranteed power supply provided by UPS emergency power supply devices. In the reserve operation mode (actuated in case of improper parameters or decay of the mains voltage) these devices use the electric energy stored in the accumulators (batteries), in order to ensure feeding of the secured receivers (of key meaning) within a predefined time, with a view to terminate the current processes [1-5]. These systems often offer many additional functions that enable more optimized power management, financial savings, or improved quality and security of operation of the equipment.
Incessant need of reasonable power management and growing cost of the electric energy force the undertakers to permanent control of its consumption. Any energetic savings are justified not only from the economical but also from technological and good management point of view. One of the factors of energy saving consists in reactive power compensation [6,7]. An important question related to this problem is how to reduce the apparent (total) power absorbed from the supply source without the change in active (usable) power of the receivers? The present paper formulates the question in slightly different way: namely, how to reduce the total power absorbed from mains by the system of guaranteed power supply, without reduction of the effective power of the receivers connected to its output, inserting no additional parts or devices compensating the reactive power.
One of the most important utility parameters of UPS power supply devices is the supply maintenance time in the reserve operation mode (in case of improper parameters of the mains voltage). The time may be extended by connection of additional battery modules, i.e. by increase of the energy stored in the accumulators. Hence, another question may be formulated: is it possible to extend the supply maintenance time of a receiver on other way, without changing the power consumed by it? It appears that another possibility of extension of the autonomous mode under definite UPS operation conditions consists in the use of hybrid operation [1-3,8-9].
The paper presents two new functions of the guaranteed power supply in the form of compensation of UPS reactive power and the hybrid operation, that allow the user to attain both economic and technological (operational) advantages. Moreover, results of the studies and calculations are presented that are relative to the considered problem for a real physical object, namely the UPS EVER POWERLINE GREEN 33.
dr inż. Karol Bednarek - EVER Sp. z o.o