Feed-Forward Control Method for Digital Power Factor Correction in Parallel Connected Buck-Boost Converter (CCM Mode)

Amongst power converters, rectifiers are needed by many devices that are connected at the distribution end of AC electrical power networks. When large capacitors are used to reduce the voltage ripple at the dc output, the line current becomes non-sinusoidal. Such non-sinusoidal line currents increase the total harmonic distortion, resulting in significant power losses within the power network. The power factor correction converter or PFC converter is a well-known alternative to generate a flat dc voltage while shaping the input current to the input ac grid voltage, emulating a resistive behavior. As the parallel connection of PFC converters is a promising way to achieve a higher power rating, questions arise on balancing the current and power over these connected converters. In this paper, based on the differential equations of a buck-boost converter, a method is obtained to compute the duty cycles of the semiconductor devices aimed at obtaining the unity power factor while balancing the current. Feed-forward algorithms are used to tune the model parameters in order to strongly reduce the input current harmonics. The proposed scheme is simulated in MATLAB and results are given showing that the proposed algorithms result in a good power factor correction.