Research On Stability Of Cascaded DC/DC Converters System

As the most basic module connection mode in the distributed DC power system, cascaded system is the fundamental determination of whether the whole distributed power system can operate normally and stably. Unstability might occur when modules are cascaded even though every module behaves normal when operating separately. Hence evaluation of the stability of cascaded system is of great importance. Based on the state-space averaging method, this paper discusses the small and large-signal stability of voltage-to-voltage converters and their cascaded systems with CCM working mode, fixed power flow direction respectively.The state-space averaging method and small-signal modeling is presented at first, and simulation comparison of small-signal stability and large-signal stability is conducted. Secondly, large-signal models of compensator and converter topology based on state-space averaging method are founded. The validity of the models is verified through calculation and simulation of a voltage-feedback Buck converter cutting load example. At last, the necessary and sufficient condition of small-signal stability of cascaded DC/DC converters system is put forward, and its sufficiency and necessity is verified through the simulation of input filter-Buck cascaded system. Large-signal model of DC/DC converter cascaded system is also founded.To sum up, the author builds an applicable large-signal model of DC/DC converters and their cascaded systems based on state-space averaging method. At the same time, precise analytical large-signal responses are solved using this model and applicable conditions of this large-signal model are also presented in this paper.