Analysis and Control of Ripple Eliminators in DC Systems

Bulky capacitors are often needed in DC systems to smooth voltage ripples, which reduces the power density and system reliability considerably. In this paper, a Ripple Eliminator (RE) that is a bidirectional buck-boost converter terminated with an auxiliary capacitor is proposed to reduce voltage ripples after connecting it to the DC bus. A controller is proposed to transfer the voltage ripples on the DC bus to the auxiliary capacitor, of which the voltage can be controlled either lower or higher than the DC-bus voltage. Three control strategies are proposed for this purpose and simulation results are presented to verify the control performance.