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The low-frequency current ripple that always appears at the input of the single-phase DC/AC inverters decreases the lifetime of DC voltage sources, such as fuel cells and chemical batteries. In this study, based on series and parallel feedback theory, a proportional-integral (PI) controller is designed for the front-end boost converter in two-stage power converters. This controller increases the output impedance of the boost converter, which reduces the low-frequency current ripple at the input of this two-stage converter. Since the designed controller corrupts the dynamic response of the boost converter, the DC-link voltage severely over/undershoots in step load conditions. Overcoming this issue by employing a non-linear gain in the forward path is shown. By applying this proposed technique, the output voltage over/undershoot stays in an acceptable range. Therefore both the low-frequency input current ripple and the DC-link over/undershoot problems disappear simultaneously without employing any additional equipment, especially a bulky DC capacitor. The simulation and experimental results for a 2.5 kW prototype confirm the performance of the proposed idea.
Date of Publication: November 2012