An enhanced control scheme for uninterruptible power supply

To address the active power feeding issue in the parallel Uninterruptible Power Supply (UPS) system, a DC-link Voltage Protection (DCVP) control strategy is proposed in this paper. The proposed control method only relies on local load information, which increases the system reliability and robustness. Moreover, virtual resistance based regulation strategies are proposed for solving the active power sharing imbalance caused by the active power feeding and harmonic power sharing imbalanced caused by the line resistance mismatching. In addition, an anti-windup based consensus distributed controller is proposed to solve the overshoot issue during the transient time in voltage and frequency restoration. With the proposed anti-windup controller, large overshoot issue is alleviated. Finally, the feasibility of the proposed methods is verified by experimental results from the parallel UPS prototypes.