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Suppression method for DC voltage fluctuation based on MMC virtual capacitor

A voltage fluctuation and virtual capacitor technology, applied in electrical components, circuit devices, AC network circuits, etc., can solve problems such as the inability to DC power supply network voltage fluctuations, and achieve the effect of enhancing the ability to suppress voltage fluctuations and improving stability

Active Publication Date: 2020-12-04
EXAMING & EXPERIMENTAL CENT OF ULTRAHIGH VOLTAGE POWER TRANSMISSION COMPANY CHINA SOUTHEN POWER GRID
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It mainly solves the problem that the existing MMC control strategy cannot provide a stable suppression effect on the voltage fluctuation of the DC power supply network

Method used

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  • Suppression method for DC voltage fluctuation based on MMC virtual capacitor
  • Suppression method for DC voltage fluctuation based on MMC virtual capacitor
  • Suppression method for DC voltage fluctuation based on MMC virtual capacitor

Examples

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Effect test

Embodiment 1

[0018] according to figure 1 As shown, this embodiment proposes a method for suppressing DC voltage fluctuations based on the MMC virtual capacitor, and controls the electrical parameters of the MMC through a preset control strategy, and the control strategy is equivalent to an adjustable capacitor. A dummy capacitor, adjusting a dummy coefficient of the dummy capacitor according to the magnitude of the voltage fluctuation, so as to suppress the DC voltage fluctuation.

[0019] The control strategy includes:

[0020] Step 1, define the point where the converter is connected to the DC power supply network as a common connection point, and calculate the square value of the actual voltage value of the common connection point, the square value of the nominal voltage value of the common connection point, and the internal energy of the MMC The nominal value and an adjustable virtual inertia coefficient are used as input, and the MMC internal energy reference value is output. The ca...

Embodiment 2

[0052] A system for suppressing DC voltage fluctuations based on MMC virtual capacitors. The electrical parameters of MMC are controlled through a preset control system, and the control system is equivalent to a virtual capacitor with adjustable capacitance. According to the magnitude of voltage fluctuations Adjusting virtual coefficients of the virtual capacitor.

[0053] Such as figure 2 As shown, the control system includes an energy reference calculation module, an internal energy control module, a DC voltage control module, a PI control module, a sliding mode direct power control module, and a current control module;

[0054] The energy reference calculation module is used to calculate the internal energy reference value of the MMC, the internal energy control module is used to calculate the absorbed power reference value of the virtual capacitor, and the DC voltage control module is used to calculate the reference value of the AC power, so The PI control module is used...

Embodiment 3

[0057] A computer-readable storage medium stores a computer program, wherein the computer program causes a computer to execute the method described in Embodiment 1.

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Abstract

The invention discloses a method for suppressing DC voltage fluctuation based on an MMC virtual capacitor. The method comprises the steps: controlling electrical parameters of an MMC through a presetcontrol strategy, enabling the control strategy to be equivalent to a virtual capacitor with adjustable capacitance, and adjusting the virtual coefficient of the virtual capacitor according to the amplitude of voltage fluctuation so as to suppress the DC voltage fluctuation. According to the invention, by presetting the control strategy in the MMC, the converter and the virtual capacitor can showa physical behavior similar to the parallel connection of the converter with the capacitor with adjustable size and the direct-current power supply network, and the virtual capacitor shows the behavior of the MMC after the control strategy provided by the invention is carried out; and specifically the virtual capacitance is changed by adjusting the virtual coefficient, so that the inertia of the direct-current power supply network is influenced, the voltage fluctuation suppression capability of the direct-current power supply network can be enhanced, and the stability of the direct-current power supply network is improved.

Description

technical field [0001] The invention relates to the technical field of flexible DC transmission, in particular to a method for suppressing DC voltage fluctuations based on MMC virtual capacitors. Background technique [0002] Modular multilevel converter (MMC) is a converter topology commonly used in flexible DC transmission systems. At present, the commonly used converter in HVDC transmission projects is VSC, which contains a large capacitor connected to the DC grid. The inertia of the DC grid depends on the size of the capacitor connected to it. If a large capacitor is connected to the DC grid, then The DC power grid has a high inertia, on the contrary, if the connected capacitor is small, the inertia of the DC power grid is small, but the capacitor terminal voltage is coupled with the DC transmission network voltage, which is a prominent shortcoming of it , In addition, the output signal of VSC is quite different from the ideal signal, and the ideal signal can only be ob...

Claims

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Application Information

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IPC IPC(8): H02J3/36H02M1/32H02M7/483
CPCH02J3/36H02J2003/365H02M1/32H02M7/483Y02E60/60
Inventor 李清
Owner EXAMING & EXPERIMENTAL CENT OF ULTRAHIGH VOLTAGE POWER TRANSMISSION COMPANY CHINA SOUTHEN POWER GRID
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