Capacitor voltage balancing in cascaded H-bridge multilevel inverter and its modelling analysis for grid integrated wind energy conversion system application

In this study, a comprehensive control scheme for cascaded H-bridge multilevel inverter (CHBMLI)-based grid integrated bulk wind energy conversion system (WECS) addressing the problem of deviation of wind speeds among windmills like a partial shading condition of PV system is presented. The proposed control scheme uses independent dc links with reduced voltages that makes such a topology an ideal candidate for high and medium power WECS with improved reliability. Inconsistency of wind speeds at each turbine causes distinct voltage conditions among the isolated dc links of the CHBMLI H-bridge cells (HBC) leading to unstable power generation. The projected scheme along with maximum and efficient energy conversion has the ability of dc link capacitor voltage balancing in each HBC of CHBMLI during the above said power generation mismatch conditions and also maintains power quality in the grid side voltage and injected currents as per standards. Moreover, the modelling analysis of the adopted CHBMLI for the grid integrated WECS application has also been derived. The system performance under inconsistent wind speed environment has been tested and analysed by using MATLAB simulation and validated by using FPGA-based real-time simulator (Opal-RT-OP5700).