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A monitoring method for capacitance value of modular multilevel converter

A modular multi-level, capacitance-capacitance technology, applied in capacitance measurement, measurement of resistance/reaction/impedance, instruments, etc., can solve problems such as MMC system failure, sensor noise error, and reducing MMC operating performance.

Active Publication Date: 2021-09-14
SOUTHEAST UNIV
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Problems solved by technology

If the change of capacitance parameters cannot be monitored in time and the failed capacitor is replaced, it will not only affect the operation performance of the capacitor itself, but also affect the reliable operation of other electrical components, reduce the overall operation performance of the MMC, and even cause the failure of the MMC system
[0005] Existing research often needs sub-module switching function to monitor capacitance value, but the switching function based on carrier phase shift control is generated in FPGA, and the switching frequency is high, while the capacitance value monitoring algorithm is in DSP Realized, which means that obtaining an accurate switching function requires a very high sampling frequency, which will bring a great burden to the communication in the DSP and FPGA, and the error caused by the noise of the sensor will affect the traditional capacitance monitoring precision

Method used

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  • A monitoring method for capacitance value of modular multilevel converter
  • A monitoring method for capacitance value of modular multilevel converter
  • A monitoring method for capacitance value of modular multilevel converter

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Embodiment 1

[0044] Aiming at the problem that the capacitance value of the capacitor decreases, the present invention proposes a method for monitoring the capacitance value of the MMC, wherein the MMC topology is composed of six bridge arms, such as figure 1 , figure 2 As shown, each bridge arm contains n identical submodules (Submodule, SM) and a bridge arm inductance L s , the sub-module adopts a half-bridge structure, and the sub-module includes two power switches T 1 , T 2 , 2 diodes D 1 、D 2 and 1 DC capacitor, the capacitor voltage balance method is:

[0045] According to the difference Δu between the bridge arm current, the sub-module capacitor voltage and the bridge arm sub-module average capacitor voltage ci Generate a compensation component, when the bridge arm current is greater than 0, the compensation component and Δu ci Inversely proportional; when the bridge arm current is less than 0, the compensation component and Δu ci Proportional to;

[0046] The compensation ...

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Abstract

The invention discloses a method for monitoring the capacitance value of a modular multilevel converter. The monitoring method includes the following steps: only one sub-module is detected at each moment, and the N T fundamental frequency period monitoring period, calculate the eigenvalue A ui , B ui 、A ii and B ii , after the monitoring period is over, the feature quantity F is calculated ui and F ii , and then calculate the capacitance value of the sub-module under test. The monitoring method of the present invention uses the modulation signal of the sub-module, does not need the precise switching function of the sub-module, reduces the communication burden and calculation burden of the controller, and has a good immune effect on sensor noise, and will not affect the modular multi-level conversion The control of the device has a negative impact.

Description

technical field [0001] The invention relates to a method for monitoring capacitance value, in particular to a method for monitoring capacitance value of a modularized multilevel converter. Background technique [0002] Compared with traditional two-level and three-level converters, modular multilevel converters (ModularMultilevel Converter, MMC) have the characteristics of high efficiency, small output AC voltage harmonics, and high modularity, and are more suitable for high voltage , high-power applications, and has broad prospects in flexible DC transmission, medium-voltage motor drives and other fields. [0003] The reliable operation of MMC is one of the keys to this technology research. The fault sources of MMC mainly include power semiconductor device faults, capacitor faults, wiring and terminal faults, and other faults. MMC usually contains a large number of modules, among which capacitor failure accounts for 30%, which is one of the main sources of MMC failure. Ca...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R27/26
CPCG01R27/2605
Inventor 邓富金刘诚恺
Owner SOUTHEAST UNIV
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