Start-Up Control to Prevent Overcurrent During Hot Swap in Paralleled DC–DC Converters

Paralleled power systems require a hot swap which indicates the replacement of a converter module without shutting down the whole system for easy maintenance, repair, and upgrade. A practical issue for the hot swap is an overcurrent toward a newly activating module due to inevitable nonuniformity among the paralleled modules, which causes the excessive current and thermal stresses and even leads to a device failure. In this paper, by analyzing the start-up operation of a converter module during the hot swap, the reason for the overcurrent is demonstrated. Then, based on this analysis, a method increasing the voltage reference exponentially is presented, which can contribute to reduce the overcurrent. However, the overcurrent still remains and causes a problem as the number of paralleled modules or difference in output voltage set points increases. Therefore, a control scheme adjusting the output voltage reference during the start-up is proposed to eliminate the overcurrent effectively. Experimental results from 1-kW paralleled phase-shifted full-bridge converters are shown to verify the proposed works.