Stability analysis and improvement based on virtual impedance for electrolytic capacitor-less DC multi-port converter

Abstract

The DC multi-port converter's applications are increasing owing to its favourable features, including variable control mode, high power density, and bi-directional power supply. On the other hand, the impedance interaction between each port of the electrolytic capacitor-less DC multi-port converter may generate an instability. To address the above mentioned problem, a method is proposed in this paper for reshaping the impedances of the energy storage converter by constructing a virtual impedance connected in parallel with the output impedance of the electrolytic capacitor-less DC multi-port converter. Furthermore, this paper introduces the stability criterion based on the unified impedance theory, which classifies a converter as either the bus current-controlled converter or the bus voltage-controlled converter. The proposed control approaches raise the magnitude of the output impedance of the electrolytic capacitor-less DC multi-port converter to satisfy the unified impedance theory criterion without modifying each port. The simulation results show that the proposed method is better than the traditional methods, and comprehensive experimental results are provided to validate the proposed methods.