DC transformer topology based on three-level CLLLC resonant converter and control method

Abstract

The invention relates to a DC transformer topology based on a three-level bidirectional CLLLC resonant converter and a control method. The topology comprises a high-voltage side topology, a low-voltage side topology and the bidirectional CLLLC resonant converter, wherein the high-voltage side topology comprises N half-bridge three-level circuits which are connected in series, the low-voltage sidetopology comprises N full-bridge circuits which are connected in series, and each group of half-bridge three-level circuits is correspondingly connected with the full-bridge circuits through the bidirectional CLLLC resonant converter. The topology has the characteristic of high voltage class, so the number of modules required by a DC transformer system is reduced, the occupied area and the cost ofthe system are reduced, the fault probability of the system is reduced, the topology adopts an equivalent pulse expansion wave generation method, and bidirectional energy flow, full-range soft switching and voltage sharing of series devices can be realized. Inter-module phase shift control is provided, and ripples of total current output by the low-voltage side parallel modules are reduced. The topological structure that the high-voltage sides of the N modules are connected in series and the low-voltage sides are connected in parallel is suitable for high-voltage large-capacity occasions.

Description

Technical field [0001] The present invention relates to the technical field of transformer design, in particular to a DC transformer topology and control method based on a three-level CLLLC resonant converter. Background technique [0002] The two-level LLC resonant converter has been more and more widely used in the industry because of its simple structure and superior soft switching characteristics, but the main disadvantages are as follows: [0003] 1) The voltage stress of the switching tube in the two-level topology is relatively large, especially in higher voltage applications, where multiple modules are required to be connected in series to meet the requirements. The greater number of modules in series leads to an increase in the probability of system failure and an increase in volume. Large, cost increase, affect the stability and reliability of the system, and increase the workload of system maintenance and system footprint; [0004] 2) At present, the three-level LLC topol...

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Problems solved by technology

[0008] Aiming at the problems of existing DC transformer modules, such as large number, large volume, high cost, and high probability of system failure, a DC transformer topology and control method based on a three-level CLLLC resonant converter is proposed. This topology has the characteristics of high voltage level , thereby reducing the number of modules required for the DC transformer system, reducing the system footprint and cost, and reducing the probability of system failure

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