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Voltage balance modulation method and device based on nearest level approximation

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

Active Publication Date: 2017-05-31
TBEA SUNOASIS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] 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 balance modulation method and device based on nearest level approximation
  • Voltage balance modulation method and device based on nearest level approximation
  • Voltage balance modulation method and device based on nearest level approximation

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Embodiment 1

[0040] This embodiment provides a voltage equalization modulation method based on nearest 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 current i of each bridge arm 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 <0), at this time, disc...

Embodiment 2

[0117] This embodiment provides a voltage equalization modulation device based on nearest 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 .

[0118] Wherein, the collection unit 100 is used to collect the capacitance voltage values ​​and switching state information of all sub-modules in each bridge arm in each control period, as well as the current i of each bridge arm armThe direction information; the acquisition unit 200 is used to obtain the conduction number Non(k) of each bridge arm neutron module in this control cycle and the conduction number Non(k-1 of each bridge arm neutron module in the last control cycle ), wherein k is an integer greater than 1; the calculation unit 300 is used to calculate the maximum value U of the sub-module capacitor voltage in each bridge arm in this control cycle max and the capacitor voltag...

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Abstract

The invention provides a voltage balance modulation method based on nearest level approximation. The voltage balance modulation method based on nearest level approximation comprises the following steps: presetting a voltage limitation value delta U and an adjusting factor H; if Umax-Umin is less than delta U, controlling switching of submodules in various bridge arms in the control period at this time according to Non(k), Non (k-1) and direction of current iarm of the various bridge arms to implement voltage balance underclocking; if Umax-Umin is greater than or equal to delta U, respectively acquiring first additional adjusting module numbers NBAN1 corresponding to the bridge arms according to capacitor voltage minimum values Umin of submodules in the various bridge arms, the voltage limitation value delta U, the adjusting factor h and the directions of current iarm of the various bridge arms, and respectively acquiring second additional adjusting module number NBAN2 corresponding to the various bridge arms according to capacitor voltage maximum values Umax of the submodules in the various bridge arms, the voltage limitation value delta U, the adjusting factor h and the directions of the current iarm of the various bridge arms; and controlling switching of the submodules in the various bridge arms in the control period at this time according to NBAN 1, NBAN 2, Non (k) and Non (k-1) to implement voltage balance underclocking. Correspondingly, the invention provides a voltage balance modulation device. On the premise of meeting requirements of voltage balance, switching frequency of a power device is reduced, and switching loss is reduced.

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 based on nearest level approximation and a voltage equalization modulation device based on nearest 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 fl...

Claims

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Application Information

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IPC IPC(8): H02M7/483
CPCH02M7/483H02M7/4835
Inventor 于向恩刘韬郝翔
Owner TBEA SUNOASIS
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