Research On Large-Signal Stability Of Cascaded System Of DC/DC Converter

The large-signal stability of cascaded power electronics system is studied in this paper, which tried to provide the theoretical design criteria for the power electronics application system using standard modules.First of all, the large signal stability phenomena of cascaded power electronics system during load transient or startup is discussed and summarized, which is quite different from conventional small-signal stability. Based on two cascaded voltage mode Buck converters, the small-signal stability and large-signal stability of the system are analyzed, and an analysis method for large-signal stability is proposed in this paper. With the proposed analysis method, the large-signal stability of cascaded system under load transient can be analyzed and designed. The simulation and experimental results verified the analysis method.Then, the existing large signal models for DC/DC converters are systematically reviewed. And their advantages and disadvantages are discussed by simulation. Based on the review, this paper presents a new large-signal modeling method for DC/DC converter using gyrator based on the principle of energy conservation, which is not affected by the topology and operation mode. The proposed gyrator-based large signal model can simulate the large-signal load transition under different conditions (such as CCM and DCM), which is suitable for system level modeling and large signal stability analysis for cascaded system. The analysis of the parameters required for the proposed model for different topology is also presented in the paper. The simulation and experimental results show that the model can accurately reflect the characteristics of ports of the power module, which can also be used to system simulation and experimental research for the large signal stability of cascade system.At last, to improve the instability phenomena of cascaded system, a voltage bus compensator (VBC) is proposed to mitigate the voltage transients on bus. The detailed control scheme is discussed in the paper. Simulation and experiment show that the cascaded system is more stable when the dc bus compensator is attached to the system.