Multi-voltage grade direct current grid system and control protection method

Abstract

The invention discloses a multi-voltage grade direct current grid system. The direct current grid system comprises at least one direct current transformer, at least two direct current buses and at least one outgoing line current limiter. One end of the direct current transformer is connected with a first direct current bus, and the other end of the direct current transformer is connected with a second direct current bus, so that the conversion of direct current voltage is realized. The outgoing line current limiter comprises a group of direct current switches and a first current limiting unit,wherein the first current limiting unit is composed of a first by-pass switch and a first current limiting resistance unit. The invention further comprises a control protection method of the multi-voltage grade direct current grid system, when a bus or an outgoing line of a direct current grid is in a short-circuit fault, a current limiting resistance unit comes into service rapidly, short-circuit current is reduced, and the voltage of the bus is maintained to be normal, so that the fault ride-through is realized, and the operational reliability of the direct current grid is greatly improved.

Description

technical field [0001] The invention belongs to the field of power electronic converters, and in particular relates to a multi-voltage level DC power grid system and a control and protection method. Background technique [0002] In recent years, the application range of DC grid technology has become more and more extensive. Due to the introduction of a large number of power electronic converters, the operation mode of DC grid is more flexible and more complex. How to effectively ensure the reliability of DC grid operation has become a limiting DC power grid. The bottleneck of network development: due to the small line impedance of the DC system, once a short-circuit fault occurs, on the one hand, the short-circuit current rises very fast, and the power electronic converter is composed of power semiconductors, and the overcurrent capability of power semiconductor devices is limited. The current will cause damage or blockage of the converter; on the other hand, the short-circu...

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Problems solved by technology

[0002] In recent years, the application range of DC grid technology has become more and more extensive. Due to the introduction of a large number of power electronic converters, the operation mode of DC grid is more flexible and more complex. How to effectively ensure the reliability of DC grid operation has become a limiting DC power grid. The bottleneck of network development: due to the small line impedance of the DC system, once a short-circuit fault occurs, on the one hand, the short-circuit current rises very fast, and the power electronic converter is composed of power semiconductors, and the overcurrent capability of power semiconductor devices is limited. The current will cause damage or blockage of the converter; on the other hand, the short-circuit current caused by the short circuit of the outgoing line will pull down the DC bus voltage, and the reduction of the DC bus voltage will affect all equipment and loads connected to the same bus.

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