A novel approach to minimize line-current harmonics in interfacing power electronics equipment with 3-phase utility systems

It has been estimated that by the end of this decade, as much as 50% of the electrical load in the U.S. will be supplied through power electronics interface. Very often in such systems, line-frequency ac voltages are converted into an uncontrolled dc voltage by means of diode-bridge rectifiers, which draw a highly distorted current from the utility source. This paper presents a novel approach to achieve nearly sinusoidal line current rectification of 3-phase utility voltages by dc-link current modulation. Significant other benefits of this approach are as follows: (i) only two transistor switches are required, (ii) a regulated dc voltage is provided at the output, thus simplifying the design of the rest of the power electronics equipment, (iii) the output dc voltage which can be quite large is automatically shared equally by two series-connected capacitors, and (iv) the usual disadvantages of passive filters are avoided. This novel approach can be applied to most of the power electronics equipment with 3-phase utility input, as well as to interface generation using renewable energy sources such as wind, solar, etc.