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An Optimum Modulation Method for Switching Frequency of Converter in Flexible HVDC Transmission System

A technology of power transmission system and flexible DC, applied in the field of converter stations, can solve the problems of large variation range and large current THD, etc.

Inactive Publication Date: 2016-08-17
XI AN JIAOTONG UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

After analyzing the error between the synthetic flux linkage formed by the switching voltage vector and the reference flux linkage formed by the reference voltage vector, it can be obtained: due to the constant sampling (carrier) frequency, the flux linkage error curve follows the reference flux in each sector The change of the voltage vector angle is approximately sinusoidal. In high-power applications, when the switching frequency of the converter is low, the change range is relatively large, so the output AC voltage and current have problems such as single harmonic content and large THD.

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  • An Optimum Modulation Method for Switching Frequency of Converter in Flexible HVDC Transmission System
  • An Optimum Modulation Method for Switching Frequency of Converter in Flexible HVDC Transmission System
  • An Optimum Modulation Method for Switching Frequency of Converter in Flexible HVDC Transmission System

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[0041] The present invention is described in further detail below in conjunction with accompanying drawing:

[0042] refer to figure 1 ,and figure 2 , the flexible direct current transmission system converter switching frequency optimization modulation method of the present invention comprises the following steps:

[0043] 1) Divide the vector space into 6 sectors by using the switching vector of the flexible DC transmission system converter through SVPWM modulation, and calculate the switching voltage vector action time corresponding to the reference voltage vector of each sector;

[0044] 2) For the sector division of the three-phase voltage modulation wave, the symmetrical 7-segment wave transmission sequence in each sector is obtained, and the error between the synthetic flux linkage formed by the switching voltage vector and the reference flux linkage formed by the reference voltage vector is calculated;

[0045] 3) Reference Figure 4 , from step 2), it can be seen t...

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Abstract

The invention discloses a method for optimizing and modulating the switching frequency of a converter of a voltage source converter based high-voltage direct-current (VSC-HVDC) system. The switching frequency in the process of modulation is changed with the reference voltage vector angle according to specific rules in each sector in order to achieve the purposes of reducing the flux linkage error and reducing output alternating voltages, the current harmonic ratio and the total harmonic distortion (THD). As the SVPWM modulation mode and the carrier modulation mode are equivalent specifically, the method of the invention is also applicable to the carrier modulation mode.

Description

technical field [0001] The invention belongs to the field of design of a modulation mode in a converter station, especially a converter station control system of a flexible direct current transmission system, relates to a switching frequency optimization modulation method, and in particular to a flexible law enforcement. Background technique [0002] The core of the flexible direct current transmission system based on the voltage source converter is the use of fully controlled turn-off power electronic devices and pulse width modulation (PWM) technology. It can be used not only to connect to the conventional AC power grid, but also to supply power to the passive network and improve its power quality. It can also realize independent control of active power and reactive power and four-quadrant operation. It is convenient to connect to the multi-terminal DC transmission system and realize The role of the static synchronous compensator (STATCOM) is to compensate the reactive pow...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/36H02J3/01
CPCH02J3/01H02J3/36Y02E40/40Y02E60/60
Inventor 孟永庆李宦曹均正张洁华
Owner XI AN JIAOTONG UNIV