A multi-voltage level DC power grid system and its control and protection method

Abstract

The invention discloses a multi-voltage level direct current power grid system. The direct current power grid system has at least one direct current transformer, at least two direct current busbars and at least one outlet current limiter; one end of the direct current transformer is connected to the first direct current busbar, and the other end It is connected with the second DC bus to realize DC voltage conversion; the outlet current limiter includes a group of DC switches and a first current limiting unit composed of a first bypass switch and a first current limiting resistor unit connected in parallel. The present invention also includes a control and protection method for a DC power grid system with multiple voltage levels. When a short-circuit fault occurs in the DC power grid busbar or outgoing line, the short-circuit current can be reduced by quickly investing in a current-limiting resistor unit, and the busbar voltage can be kept normal to realize the failure. Ride-through greatly improves the operational reliability of the DC power grid.

Description

Technical field [0001] The invention belongs to the field of power electronic converters, and particularly relates to a multi-voltage-level DC power grid system and a control and protection method. Background technique [0002] In recent years, the application of DC grid technology has become more and more extensive. Due to the introduction of a large number of power electronic converters, the operation of the DC grid is more flexible and more complicated. How to effectively ensure the reliability of the DC grid operation has become a limitation of DC power 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 quickly, and the power electronic converter is composed of power semiconductors, and the overcurrent capability of power semiconductor devices is limited, and short-circuit Current will cause the converter to be damaged or blocked; on the other hand, t...

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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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