Figure 3.Fractional-order sliding mode controller (FOSMC) for the FOSEPIC converter
Figure 3 illustrates the fractional-order sliding mode controller (FOSMC) for the FOSEPIC converter, featuring the sliding surfaces and controller responses in both boost and buck modes. Panel (a) displays the FOSMC for the boost mode, while panel (b) shows the sliding surface for the boost mode. Similarly, panel (c) presents the FOSMC for the buck mode, and panel (d) depicts the sliding surface for the buck mode. This figure highlights the steady-state responses of the input voltage, output voltage, and inductor currents with a load resistance (𝑅𝐿) of 50Ω.
Performance Under Input Voltage Variations
Figure 4 shows the dynamic responses of the inductor current (𝑖𝐿1 ) and output current (𝑖𝑜𝑢i out) following changes in the input voltage (𝑣𝑛 ),with a reference voltage 𝑉𝑟𝑒𝑓 ) of 48V and a load resistance of 50Ω. The results correspond to variations in input voltage from 60V to 30V and then back from 30V to 60V. Initially, the converter operates in buck mode at 𝑣𝑖𝑛=60𝑉. When the input voltage decreases to 30V, the converter switches from buck mode to boost mode. Conversely, when the input voltage increases back to 60V, the operation shifts from boost mode to buck mode. During these transitions, the input current adjusts accordingly to ensure that the power delivered to the load remains constant, as illustrated in Figure 4 for both operating modes. Notably, the output voltage successfully maintains its reference level at 48V in both modes.