A solid-state transformer with uninterrupted operation under fault conditions and its modulation method

Abstract

The invention discloses a solid-state transformer topology and its modulation method for uninterrupted operation under fault conditions. low-voltage AC, low-voltage DC and low-voltage AC ports; the sub-module unit SM of MMC includes: half-bridge sub-modules and full-bridge sub-modules; the ratio of half-bridge sub-modules to full-bridge sub-modules is 1:1; half-bridge sub-modules and The phase of the modulation wave of its corresponding full bridge sub-module is opposite. The method includes: modulating the half-bridge sub-module and the corresponding full-bridge sub-module by using modulated waves with opposite phases. Through the present invention, the uninterrupted operation of the low-voltage side of the solid-state transformer under the medium-voltage DC bipolar short-circuit fault can be realized, the normal energy interaction between the medium-voltage AC and the low-voltage DC can be ensured during the fault period, and the power supply reliability of the AC-DC hybrid distribution network can be improved. , and can maintain better grid-connected harmonic characteristics.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a solid-state transformer that operates uninterruptedly under fault conditions and a modulation method thereof. Background technique [0002] Renewable energy is often connected to the distribution network in the form of distributed power and converted into electrical energy for end users. However, the operation mode of the traditional distribution network is basically based on the supplier-led, one-way radial power supply, and its power distribution primary control equipment (on-load voltage regulator, contact switch, etc.) And the high-precision real-time operation optimization requirements of the distribution network when the load fluctuates frequently. With the continuous increase of distributed power access, the rapid popularization of electric vehicles, and the continuous increase of energy storage and controllable loads, it is difficult for the existing distribu...

AI Technical Summary

Problems solved by technology

The first challenge comes from the relay protection technology of distribution network

At present, the relay protection technology of the AC power grid is relatively mature, and the protection difficulty is low; however, the relay protection technology of the medium and high voltage DC distribution network is not yet mature, and the protection difficulty is relatively high. Currently, the converter topology with DC fault blocking capability is adopted More effective DC fault handling scheme

The second challenge comes from the power supply reliability of the distribution network

However, the patent uses additional duty cycle control to control the capacitor voltage of the MMC sub-module, and the capacitor voltage has a large deviation in the transient process after the fault occurs, which affects the normal operation of the solid-state transformer

Images