subject: Maximized battery run-time in a parallel UPS system [print this page] Maximized battery run-time in a parallel UPS system
An UPS(ups manufacturer) includes a plurality of UPS modules. Each of the UPS modules has a battery that provides power to a protected load in the event of a utility power failure. A plurality of controllers control how much power each of the vrla batteries deliver to the protected load, and a communication bus allows the controllers to exchange information about the battery voltages.
Uninterruptible power supplies are designed to provide continuous power to a critical load in the event of a temporary failure of utility power. In some systems, a plurality of UPS modules are connected together in parallel to supply thecritical load. Each UPS module generally includes a rectifier, a sealed lead acid battery, and an inverter. In the event of an interruption of utility power, the critical load will be supplied by DC power from the batteries in the UPS modules. This DC power isconverted to AC power by the inverters on the UPS modules before being passed to the critical bus. One disadvantage of a system using parallel UPS modules is that the load is distributed evenly across each of the deep cycle batteries in the UPS modules. There isno guarantee, however, that the batteries will have the same energy delivery capabilities.
One version of the invention relates to an uninterruptible power supply(ups manufacturer) that has a plurality of batteries that provide power to a protected load in the event of a utility power failure. It includes a plurality of controllers that control howmuch power each of the plurality of batteries deliver to the protected load, and a communication bus that allows the controllers to exchange information about the battery voltages. At least one of the controllers calculates the average battery voltageof the plurality of batteries and adjusts the amount of energy provided by an individual battery such that the battery voltage is about equal to the average battery voltage.
