Minimal UPS structure with sliding mode control and adaptive hysteresis band

The application of a sliding control mode based on a variable structure system (VSS) for an uninterruptable power supply (UPS) is presented. The incorporation of adaptive control facilitates converter operation within a constant commutation frequency, adding an implicit harmonic control to the intrinsic voltage regulation capacity of the VSS systems. The converter is characterized by online generation and good transient performance. The validity of this technique is confirmed by computer simulation. As a consequence of the system´s behavior, a minimal-UPS structure is proposed for operation in parallel with the utility grid. The resultant power converter can operate as a reactive power compensator, an energy storage system, and an active filter for the line