Differential Input Current Regulation in Parallel Output Connected Battery Power Modules

Parallel output connected converters have been widely investigated with a focus on equal current and power sharing. However, parallel output connected battery power modules (BPMs) require unequal currents to enable state-of-charge (SOC) control in active battery management systems (BMS.) This article presents simple differential input current regulation for SOC control. Compared with equal current sharing, differential current regulation is more critical on the system stability due to the cross-coupling between the paralleled BPMs. The article proposes design guidelines that enable differential current control while considering the cross-coupling between the paralleled BPMs. The small-signal model of a battery brick consisting of N parallel output connected BPMs that operate in boost mode is presented. This article shows the effect of paralleling and differential currents on the individual input current regulation loops. Simulations and experiments verify the analysis. Experimental validation using a 300-W prototype consisting of three parallel output connected battery modules in an active BMS is presented.