Fast-scale instability analysis of valley-current-mode controlled buck converter with high-frequency pulsed current load

In a DC distribution power system, the input current of post-stage converter can be regarded as a high-frequency pulsed current load (HFPCL) of pre-stage converter. Different from the traditional resistive load, HFPCL is a type of periodic and time-varying load and its frequency is around the switching frequency of the pre-stage converter. To reveal the fast-scale instability induced by the HFPCL, a valley current mode (VCM) controlled buck converter is taken as the pre-stage converter. First, the fast-scale instabilities in the VCM controlled buck converter with HFPCL are shown by the bifurcation diagrams. Second, an equivalent model of the VCM controlled buck converter with HFPCL is built up. Third, by utilizing Filippov's method and Floquet theory, the monodromy matrix of the equivalent model is obtained and the corresponding eigenvalue analyses are carried out. The results manifest that under HFPCL, the stability effects of the circuit parameters of front-stage converter can be significantly changed. Finally, the correctness of the theoretical and simulation results is confirmed by the experimental results.