Method for compensating three-phase unbalanced currents on basis of SVG (static var generator)

Abstract

The invention relates to a method for compensating three-phase unbalanced currents on the basis of an SVG (static var generator). The method includes determining whether load currents needs to be compensated or not via three-phase unbalanced judging links by the aid of load current signals which are used as control input; acquiring frequencies and phases of power grid voltages via adaptive frequency locking and phase locking links when the load currents need to be compensated; filtering harmonic current components in the load currents by the aid of discrete second-order generalized integrators; computing negative-sequence current values required to be converted for various phases if the three-phase unbalanced currents are in balanced states; transmitting the negative-sequence current values to control instruction computation modules in SVB devices; driving IGBT (insulated gate bipolar transistors) to act; generating currents equal to fundamental negative-sequence components in the load currents so that the three-phase unbalanced currents can be in the balanced states. The negative-sequence current values are used as reference current signals. The directions of the currents are opposite to the directions of the fundamental negative-sequence components in the load currents. The method has the advantages that the three-phase unbalanced currents can be dynamically compensated, and accordingly the stability and the reliability of power grids can be improved; low-pass filters can be omitted when negative-sequence currents are extracted, and accordingly the method is low in computational burden and high in response speed and tracking precision.

Description

technical field [0001] The invention relates to a three-phase unbalanced current compensation method, in particular to a method for compensating three-phase unbalanced current by using a SVG of a fully-controlled converter device. Background technique [0002] The three-phase current unbalance phenomenon means that the magnitude of the three-phase current is asymmetrical, and its causes can be summarized as accidents and normality. The former refers to the failure of one or two phases in the three-phase power system, resulting in three-phase imbalance; the latter refers to the fact that a large number of user loads are single-phase loads, and the power consumption is not simultaneous, and the distribution system is prone to three-phase Phase imbalance, especially for loads such as electrified railways, whose traction load is a high-power load with single-phase movement and frequent amplitude changes. balance. [0003] In recent years, with the increasing number of unbalanc...

AI Technical Summary

Problems solved by technology

The synchronous rotating coordinate method needs to use a low-pass filter to filter the rotated current, which will increase the calculation burden and convergence time; while the Fourier transform method needs a power frequency cycle to calculate the reference current to be compensated, which is not conducive to real-time control

In recent years, some scholars have proposed the second-order generalized integrator method. Compared with the traditional unbalanced current detection method, this method has the advantages of high detection accuracy and small calculation burden. methods and other issues need to be resolved

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