Modified LQR Technique for Fuel-Cell-Integrated Boost Converter

Abstract

Fuel cells (FCs) are an alternative source of energy whose by-products are heat, vapor, and water. For medium-power and standalone operation, an FC is integrated with a boost converter, as the required voltage level is higher than the supply. Control of such a converter with a slow dynamic source requires a fast-acting controller, since the demand executed by the controller affects the action taken by the hydrogen valve in FCs. In this article, a linear-quadratic regulator (LQR) is developed to control the power converter. In practical applications, the conventional LQR produces offset in output voltage due to effective series resistance (ESR) of the output capacitor. To make the LQR dynamic with load perturbation, information of inductor reference current is required, which changes with variation in load current. To solve these two problems, two modifications in the classical LQR have been proposed to minimize the impact of ESR (m-LQR) and incorporate control action based on the reference inductor current (M-LQR). The proposed methods are compared with the conventional average current-mode control technique. The M-LQR-based scheme is found to outperform the classical m-LQR technique in terms of improved transient dynamics and reduced offset at the steady state. In addition to numerical simulations, the proposed control techniques have been validated experimentally.