DC-side current compensation control in the rectifier terminal for power variations in back-to-back converters

Back-to-back (BTB) converters, which consist of an AC/DC rectifier cascaded with a DC/AC inverter, have been widely adopted in the interconnection of power systems. The DC link, being the interface between the rectifier and inverter terminals, is susceptible to disturbances, particularly from power fluctuations. Regardless of the magnitude of power or changes in the power flow direction, stability degradation will occur. To lessen the influence of power, a DC-link current compensation control scheme is proposed and applied to the rectifier terminal. The proposed scheme reduces the DC link impedance gain of the rectifier terminal to balance the impedance at both ends, and thus enhance stability and controllability. The scheme is applied to a BTB converter to improve the system's resistance to disturbance, regardless of variations in power magnitude or power flow direction. The accuracy of the theoretical analysis and the effectiveness of the proposed scheme are verified using simulations and a scaled-down experimental setup.