Design Of Single-phase Two-stage AC/DC Converter

In recent years,more and more electronic devices have been applied in the fields of life,medical care,education,etc.As the key device for powering electronic devices,the single-phase two-stage AC/DC converter with the merits of strong stability and high power factor,has been the focus of researchers.Therefore,this thesis mainly concentrate on the design and control methods of single-phase two-stage AC/DC converter.Firstly,by comparing the advantages and disadvantages of various PFC topologies and DC/DC topologies,the dual-diode bridgeless PFC circuit and the half-bridge LLC resonant converter are selected as the pre-stage and the post-stage of the single-phase two-stage AC/DC converter respectively.Secondly,the working process of the converter is analyzed in detail;and the gain characteristics of the pre-stage PFC topology and the post-stage half-bridge LLC resonant circuit are derived by switching element averaging method and extended function description method respectively in this thesis.In addition,he mathematic models of the AC/DC converter is established.Then,to meet the requirement of wide converter output voltage range,a hybrid control strategy based on bus voltage is proposed in this thesis,this method can achieve a large output voltage range while ensuring a small bus voltage range.The proportional resonant feedforward control method is used to suppress the low-frequency ripple of the output voltage,so that the ripple coefficient of the output voltage is controlled no more than 2%.In addition,for the matter of input current Zero-point distortion issue,a proportional resonance control method based on duty cycle compensation is introduced to improve the power factor of the input voltage.The simulation circuit was built with PSIM software.Finally,a 1 kW experimental prototype was built.Both experimental and simulation results verify the correctness and feasibility of the design method and the control strategy proposed in this thesis.