A single phase parallel power processing scheme with power factor control

With the enforcement of the agency standards such as IEC-555-2 for the harmonic components of the input line current, conventional single phase AC/DC power converters with rectifier-capacitor type input interface can no longer be used in switch mode power supplies except for power levels below 75 W. As a result, several alternative AC/DC converters, called power factor corrected (PFC) converters, meeting the agency requirements have been proposed. Most of these achieve near sinusoidal input current irrespective of power levels. However, for lower power levels, IEC-555-2 does not require a sinusoidal input current. Realising this, a parallel power processing scheme is proposed. Here, a conventional offline converter is paralleled with a PFC converter resulting in less overall power handled and thus in improved efficiency. Excellent output dynamics is achieved by two control methods. Method 1 proposes to cancel the second harmonic (100 Hz) current component injected into the output capacitor by the PFC converter. The input harmonic performance was improved further in method 2 which may be viewed as a modification of method 1. SABER simulation using both switched models and averaged models are utilised to confirm the anticipated good performance of the proposed scheme