Disadvantages of modular uninterruptible power supply

The difficulties in the development of the modular uninterruptible power supply are mainly in the increase of the power density, the increase in the number of parallel, and the reduction of the price. Rack mounted modular UPS developed from the traditional vertical (tower type) structure, has wide cooling channel and a vast volume and high power cooling fan compared with the traditional vertical (tower type) structure, modular UPS is smaller and lighter to facilitate the replacement of the monomer. Due to the limit of the size, in the case of UPS module power increased, the heat dissipation has become a big problem. In order to achieve the purpose of safe work, modular UPS syetem not only uses the original passive heat dissipation, active cooling, axial flow and air duct diversion type cooling technology, but also uses the heat pipe cooling. In order to ensure the maximum availability and scalability of the power supply, the modules should be used in parallel without limitation. When multiple UPS are connected in parallel, the most important indicator is the current sharing. That is, if N sets of UPS are connected in parallel, we must ensure that the output current of each set of UPS output current is 1 / N of the total, at least the maximum unbalance between each set should keep in the required range (usually less than 2%). In practical application, the output impedance of every ups is not the same, coupled with the inverter output voltage and voltage phase locked has positive and negative error, each UPS voltage has both phase difference and amplitude difference. All of these limit the parallel units increased, which in turn limits the improvement of power of the whole machine. At the same power, the modular UPS is much more expensive than the traditional UPS. In the future, with the continuous development of electronic technology, the demand of UPS system will be continuously improved.