Research On Single Stage High Frequency Isolated AC-DC Converter Based On Bidirectional Switches

With the increasing demand for the efficiency of charging topology,the common two-stage topology becomes hard to meet the requirements.Single-stage charging topology has become a research hotspot.A high frequency isolated single stage AC-DC converter based on bidirectional switches is studied in this paper.The topology has natural step-down characteristic,which can regulate DC side voltage or current from 0.The high frequency link constructed by bidirectional switches in transformer isolate input and output,which increases the safety.Under high frequency design,the transformer's volume can also be reduced.The topology has good theoretical and practical significance.The topology's working condition can be regarded as alternated positive and negative sets of current source PWM rectifier(CSR).Based on the theory of CSR,this paper studies the basic principle and modulation strategy of the topology,and derives the mathematical model and the double closed loop control strategy.In order to solve the problem that a large amount of harmonics is introduced by input LC resonance,the resonant suppression method with active damping is studied.In addition,this paper also analyzes the relationship between above-mentioned modulation strategy and the modulation strategy based on AC-DC-AC equivalent circuit of matrix converter.In order to ensure the safety of the commutation,it is necessary to design the bidirectional switching process.In this paper,the principle of bidirectional switch commutation between the vectors in different sectors is analyzed.Soft switching condition can be realized by the partial switch in the process of commutation.Since the process is similar to the full bridge ZVS soft switching(Zero Voltage Switching),the parameter design principle can be the reference.Based on the above analysis,a simulation and test platform is built to verify the above topology.The closed loop control of input current,output current/voltage and unit power factor operation are completed by using double closed loop control strategy in dq frame.The realization of soft switching in theoretical analysis is verified.