A kind of direct current converter and its control method

A technology of DC converter and control method, which is applied in the direction of converting DC power input to DC power output, converting irreversible DC power input into AC power output, control/regulation system, etc., and can solve problems such as difficult zero-voltage turn-on of switches , to achieve the effect of reducing the resonant current, improving the conversion efficiency, and improving the conversion efficiency

CN113437879BActive Publication Date: 2022-08-09HUNAN UNIV
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Publication Date
2022-08-09

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Abstract

The invention discloses a direct current converter and a control method thereof, comprising a soft switching network, a combined circuit, a resonance network, a transformer, a rectifier and an output capacitor, and the output voltage is controlled by adjusting the switching frequency. The combined circuit includes a first bridge arm, a second bridge arm, a third bridge arm, and a fourth bridge arm connected in series, and each bridge arm includes N series-connected sub-modules. By introducing triangular wave compensation current, the soft switching capability of each bridge arm switch is extended in a wide input voltage range. In the control method provided by the present invention, a fixed phase shift and a duty cycle are introduced between the bridge arms, so as to realize the frequency multiplication operation and obtain a high step-down ratio. The invention can realize zero-voltage turn-on of all switch tubes in a wide input voltage range, effectively reduce resonant current, reduce switching loss and conduction loss, and improve the conversion efficiency of the combined resonant converter.
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Description

technical field

[0001] The invention relates to the technical field of switching converters, in particular to a method for realizing zero-voltage turn-on of a combined resonant converter in the technical field of power electronics. Background technique

[0002] With the rapid development of medium-voltage direct current transmission systems, the need for long-distance interconnection of systems at different levels is becoming more and more urgent. High-power step-down DC converter, as one of the key equipment of DC transmission, is indispensable in the construction of multi-terminal DC power grid. Efficient power delivery, high power density, high step-down ratio, wide input range and stable operation are the key technical indicators of step-down DC-DC converters. The modular multilevel resonant converter MMR (Modular Multilevel Resonant, post-stage DC / DC isolation circuit) proposed by the invention "a resonant power electronic converter and converter device" (application n...

Examples

Embodiment Construction

[0032] The topological structure of the combined resonant converter proposed by the present invention is as follows: figure 1 As shown, it includes a soft-switching network 10 , a combined circuit 20 , a resonant network 30 , a transformer 40 , and a rectifier 50 . V i , V o are the converter input and output voltages, respectively. Each bridge arm contains N sub-modules, and each sub-module has the same structure, including an upper switch tube S u , a lower switch tube S d and a capacitor, the upper switch tube is connected in series with the lower switch tube and then connected in parallel with the capacitor, the sub-module drives the signal g x It is the driving signal of the lower switch tube, and the duty ratios of the upper and lower switch tubes are complementary and will not be turned on at the same time. I Lr , I Lm are the resonant current and the excitation current, respectively.

[0033] The soft-switching network consists of capacitor C 1 , C 2 , C 3 ,...