Flexible direct current transmission system for connecting alternating current networks with different voltage classes

A flexible DC and AC system technology, applied in the direction of power transmission AC network, etc., can solve the problems of cost and land occupation, will not be fully utilized, waste of number of sub-modules, etc., and achieve the effect of avoiding land occupation and cost problems

Inactive Publication Date: 2012-12-12
TSINGHUA UNIV +1
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Problems solved by technology

However, the modular multilevel converter connected to the AC system with low voltage will operate in the case of low modulation, and the N sub-modules will not be fully utilized, resulting in a waste of the number of sub-modules, resulting in a decrease in cost and land occupation. raised

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  • Flexible direct current transmission system for connecting alternating current networks with different voltage classes
  • Flexible direct current transmission system for connecting alternating current networks with different voltage classes
  • Flexible direct current transmission system for connecting alternating current networks with different voltage classes

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Embodiment Construction

[0016] The present invention proposes a flexible direct current transmission system connected to alternating current grids of different voltage levels, and its structural block diagram is as follows figure 1 As shown, in the flexible direct current transmission system, the first modular multilevel converter, the direct current transmission line and the second modular multilevel converter are sequentially connected in series between the first alternating current system and the second alternating current system;

[0017] The first AC system is a transmission conductor containing three AC lines, and the rated line voltage value is U ac1 ,

[0018] The second AC system is a transmission conductor containing three AC lines, and the rated line voltage value is U ac2 ,

[0019] Suppose the rated line-to-line voltage value U of the first AC system ac1 Greater than the rated line voltage U of the second AC system ac2 , then the rated DC voltage U d For: U d more than the

[00...

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Abstract

The invention provides a flexible direct current transmission system for connecting alternating current networks with different voltage classes, which belongs to the technical field of direct current transmission. When the rated line voltage value of a first alternating current system is more than the rated line voltage value of a second alternating current system, a first modularization multi-level current converter, a direct current transmission line and a second modularization multi-level current converter are sequentially connected between the first alternating current system and the second alternating current system in series. The two modularization multi-level current converters are subjected to the same direct current voltage, sub modules with the same rated voltage are also adopted, but the modularization multi-level current converter for being connected with the alternating current system with the lower voltage class can be directly connected with the alternating current system without a transformer, and moreover, a relatively smaller sub module cascade number can be adopted. After the transmission system provided by the invention is adopted, the cost of the modularization multi-level current converters is lowered through reducing the number of the sub modules; and additionally, the occupied area and cost problems which are brought by the alternating current transformer can also be solved.

Description

technical field [0001] The invention relates to a flexible direct current transmission system connected to alternating current grids of different voltage levels, belonging to the technical field of direct current transmission. Background technique [0002] For the sake of sustainable development, using renewable energy such as solar energy and wind energy to generate electricity has become the development direction of the future power system. These power generation methods have the characteristics of being far away from the main grid and fluctuating greatly over time. The flexible DC transmission system is based on the voltage source converter (VSC) and pulse width modulation (PWM) to invert the DC voltage into an AC voltage with controllable amplitude and phase, and can independently and quickly control the transmitted active power and reactive power. It greatly enhances the flexibility of power transmission and becomes the most potential power transmission method to reali...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/36
CPCY02E60/60
Inventor 饶宏宋强罗雨许树楷刘文华黎小林李立浧
Owner TSINGHUA UNIV
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