Experimental validation of multi-loop controllers for two-level cascaded positive output boost converter

In this paper, an investigation of multi-loop controllers (MLCs) for two-level cascaded positive output boost converter (TLCPOBC) operating in the continuous conduction mode (CCM) was carried out. The TLCPOBC is a recently designed DC-DC converter that can offer a higher voltage transfer ratio, good efficiency, and minimized capacitor voltage and inductance current ripples when compared to traditional DC-DC converters. The dynamic characteristics of the TLCPOBC are nonlinear in nature due to its switching mode operation. During line and load variations, conventional controllers are not able to overcome the dynamic characteristics. Hence, to control the output voltage and inductor current of the TLCPOBC, MLCs are suggested in this paper. The control structure of the TLCPOBC consists of two loops. Here, a fuzzy logic controller (FLC) and a proportional double integral controller (PDIC) act as an outer loop voltage controller for voltage regulation. Meanwhile, a proportional controller (PC) acts as an inner current loop for the inductor current regulation of the converter. The PC and PDIC parameters were obtained by the state-space equations of the TLCPOBC using the Ziegler-Nicholas tuning method. The rules of the FLC are derived from the characteristics of the TLCPOBC without a mathematical model. The performance of the TLCPOBC using MLCs was verified at different states by developing MATLAB/SIMULINK simulations and prototype models. Simulation and experimental results are validated to show the importance of the TLCPOBC with the designed controllers.