Input-output harmonics of line-current-modulated high-frequency link DC to utility power converters

Two types of commutation schemes (called Type I and Type II) are proposed and analyzed for the line-connected inverter used in line-current-modulated high-frequency DC link to utility interface power conditioning systems. In the Type I scheme the high-frequency inverter is switched off well in advance of the zero crossings of line voltage, allowing the line current to go to zero and enabling the line-connected inverter to turn off. A simple lossless forced commutation circuit is used in the Type II scheme. The effects of these schemes on line-side and input DC-side current harmonics are studied in the case of single-phase systems, neglecting the effect of controller action. The performance indices are evaluated. The results obtained from prototype experimental systems are used to verify the theory presented. The analysis presented for single-phase systems is extended to three-phase systems