Flexible multi-state switch, flexible alternating current and direct current interconnection system and control method

Abstract

The invention provides a flexible multi-state switch, a flexible alternating current and direct current interconnection system and a control method. The flexible multi-state switch comprises at least two chain type current converters. The chain type current converter comprises three energy balance current conversion chains, and the power unit is composed of a first direct current capacitor and a power assembly; the power assembly is in a half-bridge, full-bridge or direct series connection mode. The direct-current balance unit comprises three ports which are respectively defined as a first direct-current port, a second direct-current port and a third direct-current port, the first direct-current port and the second direct-current port are cascaded, and the head end and the tail end of the first direct-current port and the tail end of the second direct-current port are respectively defined as a first balance port and a second balance port of the current conversion chain; and the third direct-current port is connected with the positive electrode or the negative electrode of the first direct-current capacitor. The flexible multi-state switch also comprises at least one direct-current interconnection unit. The two ends of the direct-current interconnection unit are respectively connected with the first direct-current capacitors located on any different power units of the two chain type current converters.

Description

technical field [0001] The present application relates to the technical field of power electronics, in particular to a flexible multi-state switch, a flexible AC-DC interconnection system and a control method. Background technique [0002] With the continuous improvement of users' requirements for power consumption, power quality and power supply reliability, it is becoming more and more difficult for traditional power supply networks to meet users' power supply needs. When one of the lines in the existing power supply and distribution network is overloaded or fails, it often leads to a large-scale power outage. In the case of dual busbar power supply, one busbar is often overloaded and the other busbar is lightly loaded, and there is an unbalanced power load. If the two busbars are interconnected using power electronic technology, the reliability of power supply can be improved. , can also achieve active power balance. At the same time, in the AC and DC distribution netwo...

AI Technical Summary

Problems solved by technology

At the same time, in the AC and DC distribution network, the application range of distributed power generation in the power grid is becoming more and more extensive, and it has gradually become an effective supplement to the large power grid. Distributed power sources, loads and energy storage devices constitute a micro-grid. The types of loads, loads, and energy storage devices are different, including DC or AC, and the voltage level and capacity are also different. How to economically and effectively connect the above-mentioned low-voltage units and conduct unified management is a difficult problem to solve

[0003] In the prior art, the flexible loop-closing device based on voltage source converters (voltage source converters, VSC) back-to-back with full-control devices can realize the loop-closing operation of the power distribution network, improve the reliability of power supply, and realize the mutual transmission of active power , but the cost of the above method is too high; and the interconnection method is single, which can only realize the interconnection between two medium-voltage AC power sources, and cannot provide low-voltage AC-DC system access or realize low-voltage AC-DC interconnection

cannot be an economical and effective solution

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