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.