Research And Design For The Cascaded H-bridge Energy Storage System

The grid-connected and power transmission and distributiontechnology of the intermittent power like the wind and solar power iscurrently one of the themes of priority development areas. This applicationcorresponding with battery energy storage system has also attracted wideattention. Energy storage power conversion system (PCS) is theinterconnection of the storage battery and grid also the core of the energystorage system control strategy. Its basic features are: bi-directional energyflow capacity, the DC terminal voltage fluctuations, different capacityneeds different topologies.On the basis of the modulation strategy for multi-level converters, forthe H-bridge cascaded structure, this article first made a deep study of themodulation manners output characteristics of the three kind of modulationmethod which consist of PS-PWM, LS-PWM and SW-PWM and proposeda more novel step wave modulation method. Secondly made themathematical model of the H-bridge energy storage systems, designed thePCS power control strategy. Based on zero-sequence voltage injectedtheory, this paper proposed Stage-of-Charge (SOC) phase to phase balancecontrol strategy. Based on the fundamental voltage injection and carrierwave control, in two ways, this paper proposed the SOC balance controlinto phase, and then verified effectiveness of the theoretical analysis andthe control method through building the system model in the MATLAB/Simulink. According to project requirements, this article completed theparameter design of the entire cascade H-bridge energy storage system, particularly the number of cascaded H-bridge link. Conducted apreliminary selection for the corresponding system elements, finally madea preliminary calculation about the cascaded H-bridge system overall lossfor the connected inductance and the IGBT, proved that the PCS withH-bridge structure has a very good efficiency characteristics.