Effect of feedback parameters on instability of PFC converter

摘要

Recently, power factor correction (PFC) converter is considered as the heart of any power system. A boost PFC with average current mode control is commonly used and more attractive than other approaches because of its improved noise immunity and less total harmonic distortion (THD). Many researchers try to catch the optimum technique for designing PFC circuits. Unfortunately, in many areas of power electronics, the development is principally motivated by practical applications, and in it often turns out that a particular circuit topology or system implementation has found widespread applications long before it is thoroughly analyzed and most of its details are uncovered. Most prior works had some assumptions to reduce the non-linear PFC system to a linear system. Recently, we have detected some unstable phenomena in the region predicted to be stable by these prior linear models. This paper aims to investigate the contribution of all circuit parameters to the PFC stability and to show the importance of a detailed model describing for feedback design. The output capacitance and feedback capacitance demonstrate the major effects on the PFC stability. As the PFC operating condition moves toward heavy load, the stability is assured and instability regions lessen. The system moves to instability as the input voltage increases. Also, the instability region moves as the input frequency changes from 50 Hz, to 60 Hz. The feedback gain has a major effect on the system stability; instability area is increased and the system becomes more susceptible to instability as the feedback resistance increased. A nonlinear mathematical model is introduced that is confirmed by the simulation and experiment with a very good matching. Preferably, a suitable output and feedback parameters should be incorporated in the original PFC converter design, criteria are developed that avoids unstable operation and selects the suitable range.