Low-voltage ride-through control method of modular multi-level power electronic transformer

Abstract

The invention discloses a low-voltage ride-through control method of a modular multi-level power electronic transformer. The low-voltage ride-through control method comprises the following steps: 1, in a normal operation state of a power grid, the high-voltage input stage of the modular multi-level power electronic transformer adopts an active priority control principle; 2, when a voltage of the power grid sags, the pu value of a voltage U of a grid-connected point of the modular multi-level power electronic transformer is judged; if the voltage U of the grid-connected point is higher than orequal to 0.9, the high-voltage input stage of the modular multi-level power electronic transformer adopts the active priority control principle; if the voltage U of the grid-connected point is lower than 0.9, the high-voltage input stage of the modular multi-level power electronic transformer adopts reactive priority control; and when the fluctuation of a direct-current voltage is caused due to system energy imbalance caused by sag of the voltage of the power grid, the direct-current bus voltage is kept constant by adopting energy storage coordination control. According to the method, the grid-connected operation of the modular multi-level power electronic transformer can still be ensured during the grid voltage sag period, so that safe low voltage ride through is realized.

Description

technical field [0001] The invention relates to a low-voltage ride-through control method of a modularized multi-level power electronic transformer, belonging to the technical field of power electronic equipment. Background technique [0002] As an important part of the power system, the power transformer mainly undertakes the functions of voltage level conversion, electrical isolation and energy transfer. However, the traditional transformer has a single function and is bulky, and when the power system is disturbed or fails, it will be transmitted through the transformer, and isolation cannot be achieved. [0003] Therefore, traditional power transformers can no longer meet the needs of power grid development. In recent years, with the need for renewable energy to be connected to low-voltage AC and DC grids and the advancement of power semiconductor technology, the concept of power electronic transformers has been introduced. It is a new type of transformer that uses powe...

AI Technical Summary

Problems solved by technology

[0004] At present, after the failure of the modular multi-level power electronic transformer, it should ensure that it has low voltage ride-through capability, so that it can continue to operate for a certain period of time without going out of the grid.

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