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Double-frequency circulating current injection method for suppressing capacitor voltage fluctuation of MMC sub-module under fault

A capacitor voltage and sub-module technology, which is applied in the field of double-frequency circulating current injection, can solve the problems of power electronic device damage, sub-module capacitor voltage fluctuation and increase, etc.

Pending Publication Date: 2021-05-28
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When an AC single-phase ground fault occurs, the dynamic characteristics of the MMC will change greatly, and the voltage fluctuation of the sub-module capacitor will inevitably increase, which may cause device overvoltage and cause damage to power electronic devices

Method used

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  • Double-frequency circulating current injection method for suppressing capacitor voltage fluctuation of MMC sub-module under fault
  • Double-frequency circulating current injection method for suppressing capacitor voltage fluctuation of MMC sub-module under fault
  • Double-frequency circulating current injection method for suppressing capacitor voltage fluctuation of MMC sub-module under fault

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Embodiment Construction

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0015] The embodiment of the present invention provides a double-frequency circulating current injection method that suppresses the fluctuation of the capacitor voltage of the MMC sub-module under a fault. The flow chart and the overall system control block diagram are as follows Figure 1 ~ Figure 2 As shown, the method mainly includes the following steps:

[0016] 1. Taking the fundamental frequency and double frequency fluctuation components ...

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Abstract

The invention discloses a double-frequency circulating current injection method for suppressing capacitor voltage fluctuation of an MMC sub-module under a fault. The method comprises the steps: taking the fundamental frequency and double-frequency fluctuation components of capacitor voltage of the sub-module which generates an AC single-phase fault and considers double-frequency circulation injection as suppression targets, and building an optimization target function; carrying out global optimization by taking target function minimization as a target to obtain optimal amplitude and phase of double-frequency circulating current injection; and generating a reference signal according to the optimal amplitude and phase of the double-frequency circulating current injection, and realizing the double-frequency circulating current injection in combination with a modulation algorithm. According to the method, the capacitor voltage fluctuation of the sub-module during the fault period can be effectively reduced, and the maximum voltage borne by the MMC sub-module during the fault period is reduced.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a double-frequency circulating current injection method for suppressing fluctuations in capacitor voltage of an MMC sub-module under fault conditions. Background technique [0002] Flexible direct current transmission (VSC-HVDC) is a new generation of direct current transmission technology after alternating current and conventional direct current transmission. Flexible DC transmission technology has the characteristics of independent adjustment of active power and reactive power, strong weak grid access and low voltage ride-through capabilities, low AC filtering and reactive power compensation requirements, etc. Modular multilevel converter (MMC) has the characteristics of flexible control, module scalability, low switching frequency, and low harmonic content. At present, the Shanghai Nanhui flexible DC project, the Nanao three-terminal flexible DC p...

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Application Information

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IPC IPC(8): H02M1/32H02M7/483H02J3/00H02J3/36
CPCH02J3/36H02J2003/365H02M1/32H02M7/483H02J3/001Y02E60/60
Inventor 许建中邓伟成
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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