Modulation method and modulation controller for modular multi-level converter

A modular multi-level, modulation method technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve the impact of output performance, low output voltage sine, and low switching frequency. and other problems, to achieve the effect of improving work performance and achieving simple, effective and accurate voltage output.

Inactive Publication Date: 2014-05-21
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology

[0004] In comparison, the switching frequency of fundamental wave modulation is very low, and the loss is small, so it is convenient to embed the sub-module capacitor voltage equalization method in the modulation method, but the sine degree of the output voltage is low when the number of levels is small; PWM modulation, etc. The effective switching frequency is high, and a high-sinusoidal voltage can be output with a small number of levels. However, this modulation method usually requires quite a few PWM circuits, and the implementation is complicated when the number of levels is large. In order to achieve sub-module voltage balance This method usually requires an additional sub-module capacitor voltage equalization algorithm in the control algorithm, a

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  • Modulation method and modulation controller for modular multi-level converter
  • Modulation method and modulation controller for modular multi-level converter
  • Modulation method and modulation controller for modular multi-level converter

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[0035] It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

[0036] refer to figure 1 , figure 1 It is a schematic diagram of the basic structure of a three-phase modular multilevel converter. like figure 1 As shown, each phase of the three-phase modular multilevel converter is composed of upper and lower bridge arms, and each bridge arm is composed of 1 bridge arm reactance and N sub-modules cascaded with the same structure. The first sub-module consists of two switching devices, two anti-parallel diodes and a DC capacitor.

[0037] Figure 2A is a schematic diagram of the circuit structure of each phase unit in a three-phase modular multilevel converter; Figure 2B Generate a schematic for a single-phase waveform for a modular multilevel converter....

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Abstract

The invention discloses a modulation method and a modulation controller for a modular multi-level converter. The modulation method comprises the following steps: calculating the number njp of first sub-modules and the number of njn second sub-modules needing to be input by an upper bridge arm and a lower bridge arm respectively at each current moment according to an output voltage command value of the modular multi-level converter; selecting one of the sub-modules of the upper bridge arm to perform PWM (Pulse-Width Modulation); selecting one of the sub-modules of the lower bridge arm to perform PWM; inputting njp sub-modules of the upper bridge arm in each phase and njn-1 sub-modules of the lower bridge arm; keeping the sub-module performing PWM of the upper bridge arm and the sub-modules performing PWM of the lower bridge arm in an output complementation working state. On the basis of the modulation method and the modulation controller, efficient and accurate voltage output can be realized on a medium-voltage electric energy converting occasion with a small quantity of levels, thereby effectively improving the working performance of the modular multi-level converter.

Description

technical field [0001] The invention relates to the technical field of multilevel converters, in particular to a modulation method and a modulation controller for a modular multilevel converter. Background technique [0002] Multilevel converters are widely used in medium-high voltage and high-power power conversion applications, such as flexible AC-DC transmission technology, high-power variable frequency drives, and new energy centralized grid-connected technologies. Among all kinds of multilevel converters, the modular multilevel converter not only retains the advantages of the H-bridge cascaded multilevel converter with less stress on switching devices, highly modular structure and less distortion of the output voltage waveform, but also has the advantages of The common DC bus is especially suitable for medium and high voltage high power conversion occasions with back-to-back structure. [0003] In order to ensure the performance advantages and device stability of the m...

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Application Information

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IPC IPC(8): H02M7/483
Inventor 徐云飞龙云波徐永海肖湘宁袁敞
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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