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Cascaded voltage step-up type unidirectional direct current voltage transformer

A technology of DC transformer and AC transformer, applied in the direction of converting DC power input to DC power output, instruments, adjusting electrical variables, etc., can solve the problems of increasing the total cost of the device, complicated control, reducing system reliability, etc., and reducing operating losses. and cost, the overall system structure is simple, and the effect of reducing control complexity

Active Publication Date: 2016-08-10
HUAZHONG UNIV OF SCI & TECH
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  • Summary
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  • Claims
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Problems solved by technology

However, when a large number of DC-AC-DC transformer power units are used in series and parallel, it will bring about the problem of voltage and current sharing among the power units, and it will also bring great difficulties to the development of the control system. The total cost, but also greatly reduces the reliability of the system, this type of modular series-parallel structure still needs to put all the power units into operation at low load, making the efficiency low at low load
[0005] Although it is possible to use an inductance-capacitance-inductance step-up DC-AC-DC transformer without galvanic isolation for the internal AC circuit, such as the document "LCL DC / DC converter for DC grids" (Dragan Jovcic, Lu Zhang, IEEE Transactions on Power Delivery, 2013, 28(4), 2071-2079) disclosed a capacitor-inductor-capacitor step-up DC-AC-DC transformer, whose typical transformation ratio is higher than that of high-frequency transformers, but only relies on Inductor-capacitor-inductor boost, the highest boost ratio is generally 5, and it is still difficult to achieve a transformation ratio of 20-40
Moreover, because the DC systems on both sides of this type of topology can only use symmetrical bipolar topology, it cannot be used to connect unipolar DC systems, and this type of topology cannot be used as a basic power unit for modular series-parallel combination, making it difficult to further improve its step-up ratio, and it is for bi-directional power transfer, cost-inefficient for uni-directional power transfer applications
[0006] In summary, the existing high-power and high-voltage DC-AC-DC transformers have the defects of complex system structure and control, low power unit conversion ratio, and low operating efficiency under low-load conditions.

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Embodiment Construction

[0047] In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

[0048] The unidirectional DC transformer provided by the present invention is mainly used to unidirectionally transmit DC power from a low-voltage DC system to a high-voltage DC system. The high step-up ratio characteristics of the transformer solve the defects of too many series and parallel power modules and difficult voltage and current sharing in conventional unidirectional DC transformers i...

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Abstract

The invention discloses a unidirectional direct current voltage transformer which comprises a voltage source type current converter, an uncontrollable rectifier, and an inductor-capacitor voltage step-up loop circuit, wherein positive and negative electrodes of the voltage source type current converter are respectively connected with positive and negative electrodes of a low voltage direct current system; positive and negative electrodes of the uncontrollable rectifier are respectively connected with positive and negative electrodes of a high voltage direct current system; an alternating current side of the voltage source type current converter is connected with one end of an alternating current inductor, the other end of the alternating current inductor is connected with one end of an alternating current capacitor, the other end of the alternating current inductor is also connected with an alternating current side of the uncontrollable rectifier via an alternating current voltage transformer, and the other end of the alternating current capacitor is grounded. According to the converter in the invention, technologies of realizing two stage voltage step-up via the inductor-capacitor and the alternating current voltage transformer are adopted, the quantity of used power modules can be greatly reduced, and difficulty of controlling voltage sharing and current sharing among all power modules can be lowered.

Description

technical field [0001] The invention belongs to the technical field of electric power transmission and distribution, and more specifically relates to a cascaded step-up unidirectional DC transformer, which is used to unidirectionally transmit DC power from a low-voltage DC system to a high-voltage DC system to achieve a high step-up ratio . Background technique [0002] High transformation ratio DC transformer is the key equipment in DC distribution network, photovoltaic DC grid-connected system, and wind power DC grid-connected system. It is used to realize the power interconnection between low-voltage DC system and high-voltage DC system, and its transformation ratio can be as high as 20- 40. High-power DC transformers usually use DC-AC-DC conversion technology to realize bidirectional power transmission between two DC grids. The converters used are voltage source converters, which bring high costs and high losses. the price. [0003] In some typical applications, such ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M3/335
CPCH02M3/33569
Inventor 林卫星周猛文劲宇
Owner HUAZHONG UNIV OF SCI & TECH
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