Method and apparatus for de-centralized signal frequency restoration in a distributed UPS system

摘要

An Uninterruptible Power Supply (UPS) for de-centralized operation in a distributed UPS system is described. The UPS system includes a number of UPS units that do not have communication links between them and therefore operate in a de-centralized manner. Coordinated operation in the UPS system is achieved through a controller associated with each UPS unit. The controller identifies when the operating power signal frequency on the UPS system does not correspond to a nominal operating frequency. In response to this condition, the controller generates a frequency reference signal that is used to control the inverter of the UPS unit. The controller continuously estimates the fractional loading of the distributed system by gauging the system response to disturbances, and sets its own operating point accordingly. The controller also ensures that the system operates at its nominal frequency independent of loading. As a result, the inverter produces a power signal at the target frequency and with a power level equivalent to the power level associated with each of the UPS units of the UPS system. The performance of the overall system is not sensitive to small differences in the nominal frequency settings of the individual UPS units.