The Study of Dead Time Effect Compensation in Cascaded H-bridge Multilevel Inverters

Cascaded H-bridge multilevel inverters are widely used in renewable energy systems, high-performance power transmission systems, UPSs, and so on, due to their high degree of modularity, the need for fewer devices at the same output level, and the low stress on switching devices. However, when cascaded H-bridge multilevel inverter outputs, in order to avoid the phenomenon of straight-through between the upper and lower IGBTs of the same bridge arm, it is necessary to inject a certain dead time into the turn-on signals of the power devices. The dead time coupled with nonlinear factors such as power device turn-on and turn-off lead to serious distortion of the inverter output voltage, which ultimately leads to distortion of the load current. Aiming at the traditional PI controller's inability to suppress the periodic disturbances brought by such periodic dead time, an improved repetitive control + PI (RC-PI) strategy is proposed to utilize the tracking and suppression of periodic signals by repetitive control to compensate for the output voltage distortion brought by the dead time, so as to improve the output performance of the inverter. Simulation demonstrates the effectiveness and practicality of the proposed control approach.