Decoupling Control Strategy for Input-Series Output-Parallel Systems Based on Dual Active Bridge dc-dc Converters

Abstract

This paper focuses on dual active bridge (DAB) bidirectional DC-DC converters connected input-series-output-parallel (ISOP) configuration. Generalized average modeling approach is used to get state equations of a single DAB converter. The transformer current in DAB in purely AC, and input voltage need to be balanced, a fourth-order generalized average model of this converter has been established, using the dc components of input and output capacitor voltages and first order components of transformer current as state variables. Then small-signal model is used to derive control-to-output and control-to-input transfer functions in a single DAB converter. On this basis, the small-signal model of a four-DAB ISOP system is derived and a decoupling control strategy is applied to make input voltage balance control and output control independent of each other. Three voltage balance control loops and one output control loop are carried out by lag compensators respectively to regulate the ISOP DAB system. A single 2.5KW DAB and a 10KW ISOP system including four DAB modules are simulated in MATLAB/Simulink to verify the effectiveness and correctness of proposed strategy.