State feedback control strategy and voltage balancing scheme for a transformer‐less STATic synchronous COMpensator based on cascaded H‐bridge converter

In this study, a transformer‐less STATic synchronous COMpensator (STATCOM) based on cascaded H‐bridge (CHB) multilevel converter with floating DC links is presented. This study introduces a control strategy based on state feedback control algorithm in order to supply reactive power to the grid and to compensate the total losses in the internal H‐bridge cells. Using this strategy, the converter stability and the fast dynamic response are guaranteed. Moreover, a voltage balancing strategy is proposed, which not only regulates the DC‐link voltage of H‐bridge cells to the reference value, but also evenly distributes total reactive power among the converter cells, even when there is difference between the losses of H‐bridge cells. A 21‐level CHB‐based STATCOM is simulated in PSCAD/EMTDC environment to evaluate the performance and effectiveness of the new control strategy. Furthermore, the validity of new method is verified on a down‐scaled 7‐level CHB prototype.