Analysis of bi-directional buck-boost converter for energy storage applications

Energy storage backed applications require bi-directional energy flow. A dual carrier four switch buck-boost converter, which is one of the favorite options to support such an operation, is presented in the paper. Universal modulator required to drive the converter in all operation modes is analyzed first. It is shown that in case of dual loop cascaded control, a single controller is sufficient for stabilizing inductor current in all operation topologies. The controller output serves as an input signal to the pulsed width modulator block that includes two shifted carrier waves to create appropriate driving pulses for both converter legs. Simulation results are presented in support of the proposed theory.