Research On Method Of Single-phase Power Factor Correction Under Medium Frequency Grid

With the development of power electronic technology, boost PFC (power factor correction) converters are more and more widely used in medium frequency environment, especially in aeronautical power grid. In a grid with 400-800Hz or higher frequency, the input current zero-crossing distortion may become drastic, causing the power factor to descend. At the same time, dramatic current ripples may also result in greater losses. These have already become restrictions on application of PFC to high grid frequencies.This thesis analyzes the reasons for the generation of the input current zero-crossing distortion from the perspectives of main circuit topology and parameters, pointing out that grid frequency f, phase differenceθ, angleψDCM and inductance L all have influence on current zero-crossing distortion. Simulation tests are implemented to prove these analyses. Existing solutions to input current zero-crossing distortion, such as budget control, duty-ratio feed forward, bridgeless rectifier and initial phase angle correction, are discussed and their deficiencies are fully demonstrated.This thesis illustrates the theory in how interleaving technology solves the problem of input current zero-crossing distortion. The working principle of interleaving PFC converters is analyzed, small-signal model analysis is conducted, and control circuits are designed. The simulation tests verify the effectiveness of interleaving PFC converters restraining input current zero-crossing distortion in medium frequency grid. Furthermore, some related characteristics of this topology are analyzed, and the application of coupling inductance is discussed. This thesis analyzes the effects of coupling inductance on interleaving converters'characteristics in forward coupling and reverse coupling modes, pointing out that adequate forward coupling helps raise the electric current rising slope of the converter. Simulation tests are implemented, and the results indicate that coupling inductance has a dramatic effect on reducing the electric current ripples and improving wave form factors.The design process of the main circuit, the control circuit and the time-delay circuit are elaborated after an experimental research of interleaving PFC converters. Typical waveforms showing the performance of the system have been collected in staged experimental processes debugging the control circuit, the time-delay circuit and the main circuit respectively. The theoretical analyses are verified with analyses of the tested waveforms.