A Cascaded Super-Twisting Sliding Mode Control Strategy for Fast Voltage Regulation of SEPICs

In this paper, a cascaded Super Twisting Sliding Mode Control (ST-SMC) is proposed for voltage control of SEPICs. The theoretical analysis shows that the duty cycle affects the output voltage through the internal converter dynamics, including the inductor currents and the coupling capacitor. Therefore, the use of the cascaded control approach is more suitable for voltage regulation of SEPIC converters, consistent with existing studies. In this paper, the input inductor’s reference current is generated based on the output voltage error by using the outer-loop ST-SMC. The input inductor current control is achieved by the inner loop ST-SMC method. Thus, both input current and output voltage control are achieved simultaneously. The duty cycle is generated as a result of this cascaded control structure, and the switching signal is generated based on PWM. The main objective of the proposed cascaded ST-SMC method is to improve the dynamic performance of the output voltage control. The effectiveness of the proposed method is investigated by experimental studies under variations in the input voltage, load resistance, and reference voltage. The proposed cascaded ST-SMC method is compared with existing PI-SMC, PI-MPC, and cascaded terminal ST-SMC approaches. Compared to existing methods, a significant improvement is achieved, especially in terms of dynamic response.