Обобщенная непрерывная модель безмостового корректора коэффициента мощности

Abstract

An approach to constructing the continuous model of a new converter topology, namely, a bridgeless power factor corrector (bridgeless PFC) on the basis of a buck-boost voltage converter is considered. The reasons substantiating the need to develop new topologies of voltage converters suitable for use as power factor correctors are shown. A general approach to constructing the mathematical models of switched-mode voltage converters is presented, and the transition from switched models of these devices to continuous ones is substantiated. The range of tasks that can be solved using continuous models is formulated, and the limitations inherent in models of this type are pointed out. The continuous model of a bridgeless PFC is constructed in a stage-wise manner using the state-space averaging method. It is shown that the solution of this problem leads to construction of two models representing different operation modes of the buck-boost converter's choke: one is for its operation with continuous currents, and the other is for its operation with discontinuous currents. A method that allows a universal model suitable for use in any of these modes to be constructed is considered. An example of constructing a universal model for being used in the Micro-Cap circuit simulation program is given. The results obtained using the full switched model are compared with those obtained using the developed continuous model. It is shown that the results obtained using these models are very close to each other for the choke operating with both continuous and discontinuous currents. The ability of the used voltage converter topology to operate with both positive and negative power supply voltage is illustrated. A sine-wave shape of the consumed current during operation with discontinuous choke currents in applying an AC network voltage to its input — an important property of a bridgeless PFC on the basis of a buck-boost voltage converter — has been demonstrated. The obtained results confirm the adequacy of the developed model and the possibility of using it for obtaining the static characteristics of a bridgeless PFC. In addition, the developed nonlinear continuous model can be used for obtaining the converter’s frequency responses. The model is automatically linearized by means of circuit simulation programs. Therefore, the presented model can be used for analyzing and ensuring the stability of closed-loop control systems that will include the considered voltage converter.