Control methods for Line-interactive Uninterruptible Power Supply with Shunt Active Power Filter Function

With the increasing number of non-linear loads in industry and households, power quality is given more importance. Power supply continuity and unity power factor are the requirements on the grid and load, respectively. Both of these requirements are satisfied by the application of a hybrid UPS/APF system that can operate as an uninterruptible power supply (UPS) and as an active power filter (APF). Such a hybrid UPS/APF system is a modification of the Line-interactive single conversion UPS system. When working as an APF, i.e. achieving a unity power factor, the hybrid UPS/APF injects such a current into the point of common coupling (PCC) that the source current becomes a sine wave synchronous with the source voltage. When working as a UPS, it supplies non-linear loads with power as when they were connected to the sine AC grid. The hybrid UPS/APF system consists of two converter circuits, i.e. the inverter/rectifier and the bidirectional DC/DC converter, and hybrid energy storage composed of a supercapacitor and battery. This paper presents a simulation model in which simulation experiments tested the functionality of the converters control methods of a hybrid UPS/APF system when operating in both modes. This paper also analyzes the model predictive control (MPC) algorithm for inverter/rectifier when working as an active power filter and the modified SPWM method when working as a UPS system.