Stability Analysis and Adaptive Resonance Damping of Multi-Converter System with Bidirectional Converters

Bidirectional converters have become extensively applied in various dc power systems that contain battery energy storage systems (BESSs). Such dc power systems typically consist of several feedback-controlled converters, forming a complex power distribution system. Consequently, a number of stability issues arise due to interactions among multiple converter sub-systems. Recent studies have presented adaptive control methods for guaranteeing the stability of a multi-converter system under varying operating conditions. However, most methods have not fully considered the bidirectional power-flow in BESS that significantly affects the system dynamics and stability analysis. This paper demonstrates how a bidirectional converter can be operated as an adaptive virtual impedance to improve overall system performance. In the method, an adaptive resonance term is added to the converter’s voltage controller to damp resonances in the network’s bus impedance, thus improving voltage damping and guaranteeing stability. The reliability and performance of the multi-converter system can be maintained under varying operating conditions by updating the bidirectional converter controller structure so that the required bus voltage damping level is guaranteed.