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

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.