Research On Three-phase Y-Δ Type Interleaved Incomplete Symmetry CLLLC Resonant Converter

The new energy system generates mostly direct current when generating electricity.It needs to be inverted and merged into the power grid.It also needs to be rectified when DC load is used.There will be a great power loss in the process inverting and re-rectifying,so the demand for DC distribution network is increasing.Therefore,DC/DC converter is required to have high efficiency,large capacity,small volume,bidirectional transmission and so on.In this paper,a novel bidirectional power transmission CLLLC DC/DC resonant converter with three-phase Y-Δinterleaved parallel structure is proposed.It takes into account the large capacity characteristics of multi-phase staggered parallel structure and the bidirectional power transmission capability of CLLLC structure,and has many performance advantages such as automatic phase current sharing.Firstly,the basic structure and working principle of this topology are introduced in this paper.The structure is Y-type staggered parallel at high voltage side and Δ-type staggered parallel at low voltage side,which achieves better current sharing effect and reduces the turn ratio of primary and secondary sides of transformer.The working process of the resonant converter is described.And the basic characteristics of CLLLC resonant converter are analyzed.The influence of parameters on gain characteristics is analyzed by fundamental wave analysis method,and the forward and backword gain expressions are obtained.Then the gain characteristics of CLLLC resonant converter in the case of incomplete symmetry of resonant cavity at high and low voltage sides are analyzed,and two direct and target gain parameter design methods based on MATLAB are proposed.This design method starts with the target gain,judges and chooses the parameters from the angle of two parameters separately,realizes the frequency conversion control to change the output gain,so as to ensure that the high voltage side achieves enough output voltage.Finally,the structure and design method are validated by Saber simulation and physical experiment system.An experimental prototype of 200 kHz frequency and 1.5 kW power is used to verify the feasibility of the topology and parameter design method.The designed converter achieves high efficiency in the full load range.There are 54 papers,6 tables and 50 references in this paper.