Development of parallel processing type UPS using a novel independent control for parallel-connected UPS units

In this paper, a novel independent parallel operation control method for inverters is proposed to achieve high reliable AC distribution configurations. The proposed parallel control system improves output voltage and frequency characteristics compared to a conventional independent control system, and it is simple because it does not calculate active power, P, and apparent power, Q. The proposed parallel control system is adapted to the parallel processing type UPS that has high efficiency and no-interruption output characteristics by the original control method. In experimental results, it is confirmed that the output currents of each UPS unit are well balanced by parallel redundant system of 200 kVA+100 kVA using the proposed parallel control method. Therefore, high efficiency, high reliability and safety by the developed parallel processing UPS is achieved so that it is expected to suitable for data centers.