Coordinative impedance damping control for back-to-back converter in solar power integration system

The back-to-back topology of dual active bridges DC/DC converter cascaded with DC/AC inverter has been widely used in solar power integration system. The output impedance of DAB converter will interact with the input impedance of inverter, and without proper design, stability degradation will be engaged. Against the impedance interaction caused stability degradation problems, typical solution is to modify converter's impedance feature through control strategies, named as active solution, but conventional active solutions solely pay attention to single individual converter. Here, a coordinative impedance active damping control method is proposed, which simultaneously modifies the front DAB and rear inverter impedances, promoting a more stable manner. This article compares the proposed control with conventional individual impedance damping control methods. The impedance-based stability evaluations show that the proposed control can prompt DC-link connected converters to perform resistive impedance in the low-frequency band, thus the impedance interaction will be more damped, which contributes to an enhanced stability and dynamics. The effectiveness of the proposed control has been tested by both simulation and experiment results.