Direct-current solid-state transformer with the fault ride-through capability and a control method thereof

Abstract

The invention discloses a direct-current solid-state transformer with the fault ride-through capability and a control method thereof. The direct-current solid-state transformer is composed of a filterinductor, a full-bridge sub module, N-1 half-bridge sub modules, and N DC-DC isolated converters. The bridge sub modules are in cascaded connection and then the cascaded connection unit is connectedin series with the filter inductor to connect an intermediate-voltage direct-current grid. The output terminal of each bridge sub module is connected with a direct-current input terminal of each DC-DCisolated converter; and direct-current output terminals of all DC-DC isolated converters are connected in parallel and then are connected with a low-voltage direct-current grid. When a short-circuitfault occurs at the intermediate-voltage direct-current grid, if the voltage of the intermediate-voltage direct-current grid with the fault is higher than a preset threshold, the duty ratio of all thebridge sub modules of the direct-current solid-state transformer are adjusted to realize a fault ride-through effect; and if the direct-current voltage is lower than or equal to the preset threshold,the half-bridge sub modules and the connected DC-DC isolated converters are turned off and only the full-bridge sub module and the connected DC-DC isolated converters work to realize the fault ride-through effect.

Description

technical field [0001] The invention belongs to the technical field of power electronics applications, and relates to a DC power grid short-circuit fault and a solid-state transformer, in particular to a DC solid-state transformer with fault ride-through capability and a control method thereof. Background technique [0002] The short-circuit fault handling of the DC power grid is a difficult problem. In the DC power grid, since the short-circuit current does not have a natural zero-crossing point, the DC circuit breaker needs to break a large fault current within a few milliseconds, which is a great challenge for the DC circuit breaker. At present, there is no DC circuit breaker application Engineering examples. Therefore, there are related literatures that propose a DC fault clearing strategy without DC circuit breakers. By combining the current control capability of power electronic converters and DC switching devices that cannot break large currents but are simple in str...

AI Technical Summary

Problems solved by technology

[0003] As the basic equipment of the power system, the traditional power transformer cannot realize DC voltage conversion

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