Distributed Parallel Operation of Modified Deadbeat Controlled UPS Inverters

A novel control scheme is proposed for the parallel operation of UPS modules. In this scheme, each UPS in parallel is controlled by a modified deadbeat control method. The traditional deadbeat control has a robust problem to parameter imprecision, which restricts its application. A proportional element is added in the proposed method to solve this problem. The modified deadbeat controlled inverter has good static performance and fast dynamic response and is insensitive to parametric deviation. A distributed control method is used here to realize parallel operation. All the UPS modules are connected by two common lines. One provides a phase signal to synchronize the output voltage. The other one provides the average current signal for the instantaneous average current-sharing control. Experiments are carried out on three 1 kVA on-line UPS modules. The theoretic analysis and experimental results show that the system acts satisfactorily both in steady state and dynamic process. The load distribution among UPS modules is precise in different load conditions, and the real abundance can be achieved.