Stability Analysis of Control System Based on Linearized Model of Mutually Connected TAB Converters

An autonomous dc microgrid system has been developed that consists of triple active bridge (TAB) converters as power routing units. To achieve high-speed response of the system to power demand and short-circuit faults, high stability of voltages at all connecting points between TAB converters, and high operational stability of the entire system, a model of mutually connected TAB converters and a control system for the converters must be developed. In this paper, a linearized model of mutually connected TAB converters is proposed and used to analyze the operational stability of the control system. Next, an experiment using prototype TAB converters was conducted to validate the stability analysis. When the power flow pattern among ports of the TAB converters changed in step, the power value of each port converged to the desired power value. Therefore, we conclude that the TAB converters are stably operated by using the developed control system even when TAB converters are connected in series.