Uninterruptable power supplies (UPS) are systems, which segregate the load from the grid. If the voltage drops briefly, the UPS maintains the voltage by means of an energy buffer, such as batteries, supercaps or flywheels. Especially in sites in which even the slightest interruption is not acceptable, like servers, IT equipment, or hospitals a UPS is an essential part of the electrical installation.
Evidently, the required energy buffer predominantly determines the total cost of the UPS. Although a backup generator consisting of an internal combustion motor and generator is not as dynamically as an UPS. Due to the high cost of batteries, the UPS is often coupled to a secondary backup generator. It is recommended to consult in a premature stage of an UPS project with an expert, because a well-dimensioned UPS might generally result in a more price competitive solution, which also increases the success rate of the overall project.
For very high power ratings, exceeding the MW threshold, UPS systems are often very expensive. Direct Voltage Restorers (DVR) are devices which in case of voltage dips, increase the output voltage for the end customer. Essentially, this can be compared to an autotransformer, which maintains the secondary voltage. In practice, these devices are fully power electronic based. The advantage of these systems is that they do not need additional energy buffers, in contradiction to UPS systems. The disadvantage is that these devices do not sustain the voltage if the grid is fully decoupled. These systems are suitable in very weak power grids, for very high power ratings, if UPS systems are no longer price competitve.
Within ATS PQ, several people have received specialized training to adequately dimension, commission and service those systems. Again, multiple brands and a variety of technologies can be offered.
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