DC-link Voltage Feed Forward Controller for Buck Active Power Decoupling Circuit

Single phase ac to dc power converter generally requires an energy storage element to support instantaneous power difference between dc side and ac side. An option to use a large value of electrolytic capacitors as energy storage is not viable due to their limited lifetime and poor reliability. Hence, in reliable rectifier designs, Active Power Decoupling (APD) circuits are preferred to allow the use of long life ceramic or film capacitors. The use of bidirectional buck converter as APD circuit is advantageous due to its simple control and low switch count. With conventional controller for buck APD circuit, dc-link voltage fluctuations during load changes are often large. This may result in maloperation of dc loads and increase the voltage rating of power devices in rectifier. To address said challenges, this study ideates a dc-link voltage feed forward controller for buck APD circuit. Proposed controller does not require additional sensors to synthesize the feed forward signal. Further, it supports seamless integration of buck APD circuit into an existing rectifier design with minimum changes in host system. The design recommendations and stability analysis for buck APD circuit with proposed controller are also provided. The satisfactory operation of proposed controller is confirmed with the help simulations using MATLAB/Simulink.