Multi-Mode Operation for On-line Uninterruptible Power Supply System

To enhance the robustness and disturbance rejection ability of an on-line uninterruptible power supply (UPS) system, an internal model control-based dc-link voltage regulation method is proposed in this paper. Furthermore, the multimode operations of the on-line UPS system are investigated and their corresponding control strategies are proposed. The proposed control strategies are capable of achieving the seamless transition in traditional normal mode, photovoltaic-aided normal mode, enhanced eco-mode (EEM), and burn-in test mode (BTM). Meanwhile, the uninterruptible load voltage is promised during the mode transition. The small-signal analysis is also conducted to investigate the stability of EEM and BTM. Finally, extensive experimental results are provided to validate the effectiveness of the proposed methods.