Electrically isolated unidirectional dc-dc converter without voltage equalization control

Abstract

The invention provides an electrically isolated unidirectional DC-DC converter without voltage equalization control. The unidirectional DC-DC converter is jointly constructed by a DC-AC converter based on a modular multilevel converter (MMC), a diode rectifier bridge and an AC transformer. The modular multilevel converter can clamp DC side faults, and can also use its modular characteristics to easily realize the application of the unidirectional DC-DC converter in high-voltage and high-power occasions; the uncontrollable rectifier bridge is used to complete AC‑DC conversion; the transformer ensures electrical isolation between the two sides of the converter. Electrically isolated unidirectional DC‑DC converters without voltage equalization control rely on internally configured auxiliary capacitors, auxiliary IGBT modules, and clamping diodes to spontaneously balance DC‑DC on the basis of DC voltage conversion in unidirectional DC‑DC converters. The capacitor voltage of the sub-module in the AC converter without special voltage equalization control.

Description

technical field [0001] The invention relates to the technical field of power transmission and distribution, in particular to an electrically isolated unidirectional DC-DC converter without voltage equalization control. [0002] technical background [0003] The DC-DC converter is an important part of the DC power grid. The DC-DC converter based on the modular multilevel converter MMC is suitable for high-voltage large Power occasions have high application prospects. [0004] The DC side voltage of the MMC is not supported by a large capacitor, but by a series of independent floating sub-module capacitors connected in series. Also in order to improve the conversion efficiency of the DC-DC converter, it is necessary to ensure that the capacitor voltage of the sub-module is in a dynamic and stable state during the periodic flow of bridge arm power. [0005] The sorting voltage equalization algorithm based on capacitor voltage sorting is currently the mainstream idea to solve t...

AI Technical Summary

Problems solved by technology

First of all, the realization of the sorting function must rely on the millisecond-level sampling of the capacitor voltage, which requires a large number of sensors and fiber optic channels to cooperate; secondly, when the number of sub-modules increases, the calculation amount of the capacitor voltage sorting increases rapidly, which is a challenge for the hardware design of the controller. In addition, the implementation of the sorting voltage equalization algorithm has high requirements on the switching frequency of sub-modules, which are closely related to the voltage equalizing effect. In practice, it may not be possible due to the limitation of the voltage equalizing effect. Do not increase the trigger frequency of sub-modules, which will increase the loss of the converter

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