Two-stage single phase bi-directional PWM power converter with DC link capacitor reduction

摘要

DC link capacitance in a bi-directional AC/DC power converter using a full-bridge or H-bridge switching circuit can be greatly reduced and the power density of the power converter correspondingly increased by inclusion of a bi-directional synchronous rectifier (SR) DC/DC converter as a second stage of the power converter and controlling the second stage with a control loop having a transfer function common to both buck and boost modes of operation of the bi-directional SR DC/DC converter and a resonant transfer function to increase gain at the ripple voltage frequency (twice the AC line frequency) to control the duty cycle of the switches of the bi-directional SR DC/DC stage and controlling the duty cycle of the switches of the full-bridge or H-bridge switching circuit using a control loop including a notch filter at the ripple voltage frequency.

主权项

1. A single-phase bi-directional AC/DC power converter having a DC side and an AC side for interfacing between a DC power distribution network to which DC loads and/or DC power sources are connected and an AC power distribution grid operating at a line frequency, comprising
a full-bridge switching circuit connected between an AC source or load and a DC link, a DC link capacitor, and a bi-directional synchronous rectifier (SR) DC/DC power converter in series with said full bridge switching circuit and receiving power from or delivering power to said DC link and capable of providing DC voltage regulation in one direction of power transfer and an increased DC voltage in another direction of power transfer, and a DC side control loop in said DC side of said power converter for controlling duty cycle of switches of said bi-directional SR DC/DC converter whereby capacitance of said DC link capacitor can be reduced while limiting voltage variation at an output of said DC/DC power converter, said DC side control loop having a transfer function that has relatively increased gain at twice the AC line frequency to limit DC side voltage variation at a frequency which is twice said line frequency.