The present disclosure relates generally to uninterruptible power supplies (UPSs), and particularly to synchronization control systems for control thereof.
UPSs are employed in a variety of applications where a constant source of power is desired at a load. A typical UPS system involves an inverter feed path, also generally referred to as the inverter, that is operably connectable in parallel with a bypass feed path, also generally referred to as the mains. The mains may be connected to a utility, but may also receive power from some other supply not connected to a utility electrical grid. The inverter may receive power from the same source as the mains, but may also receive power from some other supply.
There are several types of UPSs depending on their operation mode. Double conversion UPSs offer the maximal protection level as the load is always fed by the inverter. On the other hand, with line-interactive UPSs, the load is fed by the mains and the inverter is used to correct the shape of the load voltage.
There are also several possible UPS configurations to supply a critical load, such as Redundant Parallel Architecture (RPA), Dual Independent Configuration, Load Bus Synchronization, and Power Tie, for example. With the RPA concept, (N+M) UPSs are paralleled to supply a load that can be fed by N UPSs only. This way, a redundancy of M units is achieved. More and more, and for high availability, Dual Independent Configurations are requested by customers. This requires the synchronization of two independent UPS groups and the use of an Intelligent Static Switch (ISS) that automatically switches the critical load from one source to the other. Another concept is Load Bus Synchronization where two independent UPS groups can be temporarily synchronized in order to move the critical load from one side to the other for maintenance purposes. An extension of the Load Bus Synchronization concept is the Power Tie concept, where the two independent UPS groups are permanently synchronized and their load shared as if they were a unique UPS group in a RPA configuration. Finally, and with consideration to the bypass configuration, it is desirable to be able to choose between two different options, a centralized bypass or decentralized bypass.
Accordingly, there is a need in the art for a control system and apparatus that allows multiple configurations of UPSs in critical power management systems.