A low-voltage ride-through operation control method and system for power electronic transformers

Abstract

The invention discloses a low-voltage ride-through operation control method and system of a power electronic transformer, belonging to the technical field of power systems. In the low-voltage ride-through operation, the influence of factors such as the control mode, power direction, and DC voltage quality of the power electronic transformer are fully considered. In the constant power mode, the negative sequence current suppression strategy with reactive power priority is adopted, and the direction and level of active power before and after the fault are maintained. In the constant voltage mode, the DC voltage fluctuation suppression strategy with active power priority is adopted, and reactive power support is provided to the grid. In STATCOM mode, the negative sequence current suppression strategy with active power priority is adopted, and reactive power support is provided to the grid. In addition, a segmented current limit setting method that matches the fault removal time of the staged current protection of the distribution network is adopted. The invention can adapt to complex working conditions such as multiple control modes and bidirectional power of the power electronic transformer, fully exerts its control efficiency, and effectively improves the reliability of power supply of the power grid.

Description

technical field [0001] The invention belongs to the technical field of power systems, and more particularly, relates to a low-voltage ride-through operation control method and system of a power electronic transformer. Background technique [0002] With the growth of distributed energy grid-connected capacity and the proportion of DC load, power electronic transformers have been popularized and applied because of their superior distributed power supply capacity and DC load matching performance. During the grid fault, the low-voltage ride-through operation control method with good performance can not only ensure the safe operation of the power electronic transformer itself, but also maintain uninterrupted operation, assist in the fault removal and operation recovery of the grid, and effectively improve the reliability of the grid power supply. [0003] The research on topology design and normal control methods of power electronic transformers has been relatively mature. Relev...

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Problems solved by technology

Relevant research has been carried out on the low-voltage ride-through operation control method during grid faults, but there are still some problems, which are concentrated as follows: (1) The low-voltage ride-through control method of inverter power sources such as photovoltaic power generation and direct drive wind power generation is continued, The characteristics of bidirectional power transmission of power electronic transformers are ignored; (2) The influence of various control modes such as constant power control and constant voltage control adopted by power electronic transformers, and the needs of different control modes for low-voltage ride-through operation are not fully considered ; (3) The current limit selection during the low-voltage ride-through operation control period is relatively conservative, and the control performance of the power electronic transformer cannot be fully utilized

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