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Unified power flow controller adopting modular structure and starting method for unified power flow controller

A power flow controller and modular technology, applied in the direction of power transmission AC network, etc., can solve the problems of limited controllable range, charging of series converters, etc., and achieve the effect of improving device reliability, high reliability, and simple control method

Active Publication Date: 2013-09-18
STATE GRID CORP OF CHINA +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Because the UPFC series converter passes through the transmission line current, the current depends on the line load, is limited by many factors, and the controllable range is limited. For the sake of system safety and device safety, the series converter cannot be directly charged by the system current

Method used

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  • Unified power flow controller adopting modular structure and starting method for unified power flow controller
  • Unified power flow controller adopting modular structure and starting method for unified power flow controller
  • Unified power flow controller adopting modular structure and starting method for unified power flow controller

Examples

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Effect test

Embodiment 1

[0070] Put in the DC current limiting resistor current limiting start to limit the current after the converter is unlocked when the sub-module is low voltage; the circuit structure is as follows figure 1 shown;

[0071] When the parallel converter makes the sub-module capacitor voltage reach the rated value through controllable rectification, the capacitor voltage of the MMC module on the series side reaches half of the rated value. At this time, the series-side MMC pulse is unlocked, and the sub-modules are divided into two groups for input. At the same time, a current-limiting resistor is put into the DC side to limit the inrush current. The series-side MMC can absorb electric energy through the DC side to charge the module capacitor. When the number of modules put into each group of each phase of the MMC on the series side is N, the capacitors of the N modules can be charged to the rated voltage. Through the two-stage switching and alternate charging methods, the capacitor...

Embodiment 2

[0077] Putting in the AC current limiting resistor to start the current limit, the circuit structure is as follows figure 2 shown. This scheme omits the DC current limiting resistor and its bypass switch, but it will increase the valve's requirements for voltage and current tolerance. In the uncontrolled rectification stage, a current-limiting resistor is required on the AC side, and the resistor is bypassed after the uncontrolled rectification ends. This resistor can be switched back on to limit inrush current when controlled rectification begins.

[0078] The full charging procedure is as follows:

[0079] The parallel converter triggers pulse unlocking, and uses constant DC voltage control until the AC side charges the capacitor voltage of the parallel converter sub-module to the rated value. At this time, the capacitor voltage of the series converter sub-module is charged to half of the rated value.

[0080] Disconnect the soft start resistor bypass switch BKRST;

[0...

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Abstract

The invention discloses a unified power flow controller adopting a modular structure and a starting method for the unified power flow controller. According to the method, inter-phase current generated through the line voltage of an alternating current system between bridge arms of a converter is used for charging a parallel converter module of the unified power flow controller, and a series converter module is charged through a direct current side by a parallel side. The unified power flow controller adopting the modular structure is rapidly and normally started by controlling the switching of each bridge arm sub-module for the pre-charging of all sub-module capacitors. A starting process is dependent on an alternating current power grid, an auxiliary direct current power supply is not required, and starting energy is provided for the controller through a one-sided alternating current power grid of the parallel side. The controller and the method are also applied to the starting of a modular multilevel converter-based direct current power transmission system during power supply to a passive network.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a unified power flow controller adopting a modular structure and a starting method thereof. Background technique [0002] The unified power flow controller (UPFC) is a series-parallel hybrid FACTS device based on voltage source converters, which can flexibly control multiple electrical parameters and is an effective means to improve the controllability of the power grid. In order to match the voltage and power level of the transmission network, effective measures must be taken to increase the capacity of the UPFC converter. The modular multilevel converter (MMC) breaks through the design idea of ​​the traditional voltage source converter, and installs the DC capacitors in each sub-module in a scattered way, and adopts the method of directly connecting the modules in series, through multiple Small level values ​​are superimposed to generate multi-level AC vo...

Claims

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Application Information

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IPC IPC(8): H02J3/36
CPCY02E60/60
Inventor 周飞宋洁莹荆平胡娟苏雪源詹建荣陈颖
Owner STATE GRID CORP OF CHINA
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