Modular multilevel DC solid state transformer and charging control method thereof

Abstract

The invention discloses a modular multilevel DC solid state transformer and a charging control method thereof. The transformer comprises two groups of MMCs, a high-frequency transformer, a resistor and a switch, wherein one group of MMCs is connected with the primary side of the high-frequency transformer and the other group of MMCs is connected with the secondary side of the high-frequency transformer; the MMCs at the primary side are connected with a DC power supply through a parallel structure of the resistor and the switch; and the MMCs at the secondary side are connected with a load. In the method, all 2N sub modules in each phase of the MMCs at the primary side of the DC transformer are inputted; then, through comparing the primary current value and a limited current value, the inputted number of the primary MMC sub modules is reduced; and finally, the inputted sub modules in each phase are distributed again in an upper bridge arm and a lower bridge arm, a phase-shift angle is combined to determine triggering pulses of the primary MMCs, and soft charging of the DC transformer is realized. the primary DC of the DC transformer and the AC of the high-frequency transformer are reduced, and power sub modules and the high-frequency transformer are protected during the DC transformer charging process.

Description

technical field [0001] The invention relates to high-voltage and high-power power electronic technology, in particular to a modular multilevel DC solid-state transformer and a charging control method thereof. Background technique [0002] In recent years, due to the disadvantages of system instability and large transmission loss in AC transmission, the development of AC transmission has encountered a bottleneck. With the rapid development of power electronics technology, DC transmission has ushered in a new opportunity for development. DC transformer is an important part of DC transmission system. At present, modular multi-level DC solid-state transformers using power electronic devices are widely concerned by scholars at home and abroad. Modular multilevel DC solid-state transformers have the characteristics of simple control, small circulating current, and strong fault handling capabilities, which are particularly important for DC distribution networks. However, the modu...

AI Technical Summary

Problems solved by technology

However, the modular multi-level DC solid-state transformer also has shortcomings, because the current overshoot in the voltage of the sub-module capacitor charging of the modular multi-level DC solid-state transformer is easy to cause damage to power electronic devices and high-frequency transformers

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