Dynamic voltage adjusting device and method based on modular multi-level inverter

Abstract

The invention relates to a dynamic voltage adjusting device and method based on a modular multi-level inverter, and the device comprises a main circuit and a DSP control circuit. The main circuit comprises an energy storage unit, an MMC inversion unit, and a capacitor coupling unit. The energy storage unit provides energy for a compensator, and the MMC inversion unit is provided with a modular multi-level structure. A single-phase topological structure comprises an upper bridge arm and a lower bridge arm. Each bridge arm comprises a plurality of submodules which are in series connection and have the same structure, and one bridge arm reactor. The voltage waveform which meets the requirements is outputted through controlling the on / off of a switching device in each submodule, and the capacitor coupling unit is used for inhibiting the impact on a load from the voltage fluctuation of a system. Compared with the prior art, the device is low in switching frequency, is low in switching loss, is small in output harmonic, and is good in application prospect.

Description

technical field [0001] The invention relates to a dynamic voltage compensator, in particular to a dynamic voltage adjustment device and adjustment method based on a modular multilevel inverter. Background technique [0002] Since the electricity capacity of the power grid changes at any time and a large number of nonlinear loads are used in production, these devices will inject a large number of high-order harmonics into the power system, and will also cause power quality problems such as voltage fluctuations, voltage dips, and interruptions. The voltage fluctuation on the primary side of the power transformer leads to the instability of the voltage on the secondary side of the distribution transformer, which affects the quality of electricity for users. Studies have shown that voltage fluctuation has become one of the power quality problems that affect the normal and safe operation of many electrical equipment. In addition, more and more people use sophisticated electronic...

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Problems solved by technology

[0004] (1) Two-level converter: the topology is simple but its capacity is small, and the voltage harmonic characteristics are poor

[0005] (2) Multi-level clamped converter: With the increase of the number of levels, the number of clamping components required by the converter increases, the midpoint potential of the DC side voltage is easy to fluctuate, and the control algorithm is more complicated. In practical applications restricted in

[0006] (3) H-bridge cascaded multilevel converter: avoids the problem of capacitor voltage equalization, but as the voltage level increases, the number of secondary windings of the phase-shifting transformer required increases, and the manufacturing cost and difficulty increase. An independent DC power supply is required, which limits its application in some fields

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