Modular Impedance Modeling and AC Bus Voltage Stability Analysis of Cascaded System in More-Electric Aircraft

The three-stage generator (TSG), as one of the most used more-electric aircraft generators, is crucial for the stable operation of aircraft power supply systems. The presence of numerous converters in cascade with the generator leads to complex physical and control dynamic interactions, which affect the stability of the ac bus voltage. To address the stability issue, two major contributions are made in this article. First, a dual-port modular impedance/admittance modeling method suitable for cascaded system with TSG and pulse width modulation (PWM) rectifier (TSG-PWM) is presented. In this method, a dual-port network is formed by Thevenin's theorem and Norton's theorem to analyze the modules' stability directly. Due to the advantages of modular modeling, this method also offers generality and scalability. Subsequently, a self-defined stability margin criterion based on the Gershgorin circle theorem is proposed. This criterion can determine the ac bus voltage stability state of the actual system accurately. Compared to the generalized Nyquist stability criterion, it permits the definition of stability margins based on system requirements prior to the system design. In addition, the proposed criterion enables the determination of parameter thresholds at the stability boundary with minimal computational effort. Finally, the proposed stability criterion is validated through a hardware-in-the-loop platform using the derived dual-port network model of the cascaded system. Theoretical and experimental results agree well.