Research On Battery Energy Storage Systems Based On Cascade Dual-boost/Buck Converters

In the current smart grid, the penetration of intermittent renewable energyresources is daily on the increase. Energy Storage System has been more widelyapplication. Different from other storage methods, battery energy system with lowcost and non-pollution. Because of the renewable sources’ stochastic volatility,storage technologies play an important role on the safe and stable operation of powerdistribution network and improving the utilization efficiency of renewable energy.Firstly, there are shoot-through issues and low input dc voltage utilization ratein the traditional cascade H-bridge converter structures. In this paper the cascadedual-boost/buck half-bridge and full-bridge bidirectional ac-dc converters areproposed for grid-tie transformerless battery energy storage systems (BESS).Compared to the cascade H-bridge converter, there is no shoot-through issue in theproposed converter, which is more reliable for BESS.Secondly，the steady state of proposed BESS and overview of unified controlsystem are presented. Then the unified control scheme is proposed for active-powercontrol and individual-SOC balancing control of BESS, emphasis on unified controlscheme for single-phase BESS.In the end, a laboratory BESS is constructed and tested combining a cascadetwo-unit dual-boost/buck half-bridge converter with nine lead-acid series-connectedbattery units. Experimental results obtained from the laboratory system verified thefeasibility and effectiveness of the proposed BESS and unified control scheme.