A new buck-type active front end rectifier topology with improved voltage transfer ratio and common mode voltage cancellation

AC/AC power conversion is widely used to feed AC loads with variable voltage and/or variable frequency from a constant voltage constant frequency power grid or to connect critical loads to an unreliable power supply while delivering a very accurate sinusoidal and balanced voltage system of constant amplitude and frequency. The load specifications will clearly impose the requirements for the inverter stage of the power converter, while a wider range of choices are available for the rectifier. This paper investigates the utilization of a buck-type current source rectifier as an active front-end stage of an AC/AC converter for applications that require adjustable DC-link voltage with an improved upper limit as well as elimination of the low-frequency common mode voltage. The proposed solution is to add two asymmetric H-bridge inverters in series with each of the DC-side terminals of the buck rectifier and to develop a new control strategy for this hybrid assembly.