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Frequency reduction control method of modular multilevel converter containing auxiliary sub-modules

A modular multi-level, auxiliary sub-module technology, applied in high-efficiency power electronic conversion, output power conversion devices, conversion of AC power input to DC power output, etc., can solve the problem of high output voltage harmonic distortion rate and power quality. Can not meet the transmission demand and other problems to achieve the effect of reducing harmonic distortion rate, reducing requirements and costs, and reducing switching frequency

Active Publication Date: 2020-12-25
HUNAN UNIV
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Problems solved by technology

However, when the number of sub-modules is small, the number of MMC output levels is reduced, and the harmonic distortion rate of the output voltage will be high, making the power quality unable to meet the power transmission requirements

Method used

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  • Frequency reduction control method of modular multilevel converter containing auxiliary sub-modules
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  • Frequency reduction control method of modular multilevel converter containing auxiliary sub-modules

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Embodiment Construction

[0018] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

[0019] figure 1 It is a topological structure diagram of a modular multilevel converter containing auxiliary sub-modules. The modular multilevel converter is composed of 6 bridge arms; the 6 bridge arms are divided into 3 groups on average, and each group constitutes a Phase unit, each phase unit includes upper and lower bridge arms; the upper and lower bridge arms are connected in series, the connection is called the midpoint of the phase unit, and the phase units are connected in parallel; the upper bridge of each phase unit The arm is composed of N half-bridge sub-modules, 1 full-br...

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Abstract

The invention discloses a frequency reduction control method of a modular multilevel converter containing auxiliary sub-modules. Each bridge arm of the modular multilevel converter topology is formedby connecting N half-bridge sub-modules, one auxiliary sub-module and one bridge arm inductor in series, the auxiliary sub-module adopts a full-bridge structure, and the capacitor voltage of the auxiliary sub-module is controlled to be 1 / 2 of that of the half-bridge sub-modules. A nearest level approximation modulation mode is adopted for the half-bridge sub-modules of each bridge arm, and the auxiliary sub-modules are input only when the input number of the bridge arm half-bridge sub-modules is smaller than or equal to a preset value; The forward input and the reverse input of the auxiliary sub-modules need to be determined according to the deviation between the actual values and the reference values of the capacitor voltages of the auxiliary sub-modules in the current state and the current directions of the bridge arms. According to the control method, the auxiliary sub-modules connected in series can only be input in part of time periods, the switching frequency of the auxiliary sub-modules is effectively reduced while the output level number of the MMC is increased and the output voltage harmonic distortion rate of the modular multilevel converter is reduced, and the loss of the system is reduced.

Description

technical field [0001] The invention belongs to the field of power electronic conversion, in particular to a frequency reduction control method of a modular multilevel converter with auxiliary sub-modules. Background technique [0002] In recent years, the rapid development of industry and economy has led to rapid energy consumption. Electric energy has been favored by various countries because of its clean, convenient and sustainable advantages. However, the voltage level and power quality of traditional transmission methods cannot meet the demand gradually. With the continuous advancement of power electronic switching devices and control technology, flexible DC transmission technology has developed rapidly. Modular multilevel converter (MMC) has become the preferred solution for current DC transmission projects due to its technical advantages such as high power, high reliability, strong fault handling capability and convenient expansion. [0003] Commonly used MMC modulat...

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Application Information

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IPC IPC(8): H02M7/483H02M7/5387H02M1/12
CPCH02M1/12H02M7/483H02M7/53871H02M1/0048Y02B70/10
Inventor 荣飞孙宗卿徐爽潘烙陈志忠刘成
Owner HUNAN UNIV
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