Cascaded H-Bridge Multilevel Converter for Large-Scale Solar PV-BES System

In this paper, a fundamental switched modulated MW size eleven-level cascaded H-bridge (11L-CHB) VSC (Voltage Source Converter) is utilized in a 48MW/336MWh BES (Battery Energy Storage) for a 80 MW solar PV plant for energy timeshifting application. The CHB-VSC and NAS-battery both complement each other, as CHB allows a direct connection of a NAS battery container with its H-bridges for independent control of the battery state of charge (SOC). On the other hand, the NAS-battery offers an isolated voltage source for a CHB VSC for generation of staircase voltage waveform and allows a high voltage integration of NAS-BES to the grid. Moreover, with the utilization of soft-switching technique in CHB, enables high conversion efficiency and lower device switching losses as compared with high-frequency PWM switching. An 11L-CHB VSC with NAS-BES is developed in Matlab/Simulink environment to validate the design and control. Harmonics, steady state and dynamic performances of it, are demonstrated in detail to justify its utility.