Multi-functional grid-connected inverter with enhanced disturbance rejection capability

Apart from the basic renewable generation function, the multi-functional grid-connected inverter (MFGCI) derived from traditional grid-connected inverter could provide ancillary power quality enhancement functions for the interfaced grid. However, with multiple functions integrated into one control system, the control scheme of MFGCI would become inevitably more complicated and vulnerable to the disturbance in distribution networks. Here, a control scheme of MFGCI for rejecting both the steady-state and dynamic-state disturbance is designed. The proposed control scheme includes an inner loop controller and an improved reference current generation algorithm, which constitutes an overall MFGCI control scheme. To reject the steady-state disturbance which would distort the output current of MFGCI, the inner loop controller by combining the linear adaptive disturbance rejection controller (LADRC) and repetitive controller (RC) is designed. While for the dynamic-state disturbance which would amplify the output current of MFGCI or even destroy the stability of the system, an improved reference current generation algorithm with enhanced dynamic disturbance rejection capability is proposed. The proposed MFGCI could provide overall improvements in both dynamic- and steady-state disturbance rejection capability. Finally, some experiments are conducted to verify the superiority of the proposed MFGCI.