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Voltage-equalizing modulation method and voltage-equalizing modulation device with recent level approximation

A recent technology of level approximation and modulation method, which is applied in the field of flexible power transmission and transformation, can solve the problems of large switching loss and many IGBT switching times

Active Publication Date: 2019-06-25
TBEA SUNOASIS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] However, in the traditional voltage equalization control strategy, it is necessary to continuously determine the switching status of each sub-module according to the sorted capacitor voltage and the direction of the bridge arm current. Even if the capacitor voltage of the sub-module does not change much, switching may occur frequently Conversion, resulting in many switching times of IGBT in each bridge arm, and large switching loss

Method used

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  • Voltage-equalizing modulation method and voltage-equalizing modulation device with recent level approximation
  • Voltage-equalizing modulation method and voltage-equalizing modulation device with recent level approximation
  • Voltage-equalizing modulation method and voltage-equalizing modulation device with recent level approximation

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Embodiment 1

[0040] This embodiment provides a voltage equalization modulation method with closest level approximation. Such as figure 2 As shown, the voltage equalization modulation method includes the following steps S101 to S104.

[0041] S101. Real-time collection of capacitor voltage values ​​and switching status information of all sub-modules in each bridge arm in each control cycle, as well as the current i of each bridge arm arm direction information.

[0042] In this embodiment, the arm current i arm When the direction is downward, it is the positive direction (i arm >0), that is, the bridge arm current i arm It is the positive direction when the positive pole Vdc+ of the DC bus voltage flows to the negative pole Vdc- of the DC bus voltage. At this time, the capacitor of the sub-module that has been put into the bridge arm is charged; otherwise, the bridge arm current i arm When the direction is upward, it is the negative direction (i arm arm direction information, and in t...

Embodiment 2

[0114] This embodiment provides a voltage equalization modulation device with closest level approximation. Such as Figure 4 As shown, the voltage equalization modulation device includes an acquisition unit 100 , an acquisition unit 200 , a calculation unit 300 and a control unit 400 .

[0115] Wherein, the collection unit 100 is used for real-time collection of capacitor voltage values ​​and switching state information of all sub-modules in each bridge arm in each control cycle, as well as each bridge arm current i arm direction information;

[0116] The acquisition unit 200 is used to acquire the current average capacitance voltage U of the sub-modules in each bridge arm in this control cycle. ave , the maximum and minimum values ​​of the capacitor voltage in the sub-modules where each bridge arm has been put into use, and the maximum and minimum values ​​of the capacitor voltage in the sub-modules where each bridge arm has been removed;

[0117] The calculation unit 300 ...

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Abstract

The present invention provides a voltage equalization modulation method with the nearest level approximation, including: preset sub-module unbalance degree h, if the bridge arm current i arm is positive, then control the switching of the sub-module in the bridge arm so that the difference between the maximum value of the capacitor voltage in the sub-module that has been put into the bridge arm and the minimum value of the capacitor voltage in the sub-module that has been removed is less than h*U ave ; If the arm current i arm If the direction of the bridge arm is negative, then control the switching of the sub-module in the bridge arm so that the difference between the maximum value of the capacitor voltage in the sub-module that has been cut off and the minimum value of the capacitor voltage in the sub-module that has been put into the bridge arm is less than h*U ave . Correspondingly, a voltage equalization modulation device is provided. The invention can reduce the switching times of the power device and reduce the switching loss under the premise of satisfying the voltage equalization requirement.

Description

technical field [0001] The invention relates to the technical field of flexible power transmission and transformation, in particular to a voltage equalization modulation method with closest level approximation and a voltage equalization modulation device with closest level approximation. Background technique [0002] Compared with traditional voltage source converters, modular multilevel converters (Modular Multilevel Converter, MMC) have the advantages of good scalability, small harmonics, low switching frequency, and less requirements for consistent triggering of devices. The advantages are obvious, especially suitable for DC transmission applications. MMC-based flexible DC transmission technology is widely used in new energy transmission, urban expansion, regional power grid interconnection, and island power supply. Compared with traditional DC transmission technology, the advantages of flexible DC transmission technology are gradually highlighted. A number of flexible D...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/483
CPCH02M7/483H02M7/4835
Inventor 刘韬于向恩李东松
Owner TBEA SUNOASIS