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Modulation method of modular multilevel converter (MMC)

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 problem of limiting the performance of converters and increasing the harmonic content of output voltage and other problems, to achieve the effect of reducing harmonic content, reducing volume and weight

Inactive Publication Date: 2011-09-21
INST OF ELECTRICAL ENG CHINESE ACAD OF SCI
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Problems solved by technology

In addition, although the unified modulation method only needs two carriers with different phases, the number of output voltage levels is much smaller than that of the separate modulation method, resulting in a significant increase in the harmonic content of the output voltage of the modular multilevel converter, which limits the Converter performance

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  • Modulation method of modular multilevel converter (MMC)

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Embodiment Construction

[0018] figure 1 It is the circuit schematic diagram of the modular multilevel converter. u dc is the DC supply voltage, SM U1 -SM UN and SM L1 -SM LN They are respectively N submodules of the upper bridge arm and the lower bridge arm of a bridge arm, where N is a positive integer. The internal structure of each submodule is the same, such as figure 2 shown, where C SM is the sub-module capacitance, U SM is the sub-module capacitor voltage. L U and L L is the arm snubber inductance. u U and i U is the voltage and current of the upper bridge arm, u L and i L are the voltage and current of the lower arm. u an is the output voltage of one arm of the modular multilevel converter.

[0019] A bridge arm of a modular multilevel converter is composed of 2N sub-modules with the same internal circuit. Such as figure 2 As shown, each sub-module is internally controlled by the first switch S 1 , the second switch S 2 and capacitance C SM constitute, the first switc...

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Abstract

The invention provides a modulation method of a modular multilevel converter (MMC). The modulation method comprises the following steps: calculating a reference voltage of each submodule according to the reference voltage of each bridge arm, current direction of buffer inductance of each bridge arm and capacitive voltage of each submodule; and comparing the reference voltage of each submodule with the same triangular carrier so as to decide the on-off state in each submodule and realize pulse width modulation (PWM). The modulation method has the beneficial effects that output voltage of the MMC can generate 2N+1 (N is the number of the submodules of the upper bridge arm or the lower bridge arm in the MMC) electrical levels without carrier phase shifting (CPS), thus simplifying implementation procedures and saving software and hardware resources; the step height of a step wave of the output voltage is only 50% of that of each capacitive voltage, thus obviously reducing the harmonic content of the output voltage; the capacitive voltage on each submodule can be balanced without any capacitive voltage closed-loop controller; and meanwhile the average voltage on the buffer inductance of each bridge arm is zero without a direct current (DC) component and a low frequency component, thus reducing volume and weight of the inductance.

Description

technical field [0001] The invention relates to a modulation method of a multilevel power electronic converter, in particular to a pulse width modulation method of a modular multilevel converter. Background technique [0002] Modular Multilevel Converter (MMC) is a new type of power electronic converter that has recently received widespread attention. It was first proposed by A. Lesnicar and R. Marquardt in Germany around 2002. The modular and cascadable structure of the modular multilevel converter determines that it is especially suitable for the application of medium-voltage to high-voltage power electronic conversion. Relevant research institutions at home and abroad have done a lot of research on the control method of modular multilevel converters. US patent applied by Siemens AG: US 2010 / 0067266A1. [0003] In addition to the control method, the quality of the modulation method will also significantly affect the output voltage characteristics of the converter and sys...

Claims

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Application Information

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IPC IPC(8): H02M7/483
CPCH02M7/5395H02M2007/4835H02M7/4835
Inventor 李子欣王平李耀华朱海滨楚遵方王松
Owner INST OF ELECTRICAL ENG CHINESE ACAD OF SCI
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