Novel zero-sequence current compensator

Abstract

The invention provides a novel zero-sequence current compensator. An inverter bridge is connected between a neutral point and a neutral line of a zigzag transformer; and a current output by the inverter bridge is injected into a system through a low-impedance zero-sequence current channel which is provided by the zigzag transformer so as to compensate for a neutral current. A controllable rectifier module is connected with the secondary side of the zigzag transformer to supply a direct-current power supply to the inverter bridge, and thus, the two-way flow of energy is realized and the problem of direct-current voltage rise caused when the compensator absorbs active power is solved. The novel zero-sequence current compensator has a series of advantages of good compensation effect, low direct-current voltage, small switching stress, few influences of system parameters, flexible control, few influences on system operation and the like.

Description

technical field [0001] The invention belongs to the technical field of electric power, in particular to a novel zero-sequence current compensator which can be used in a low-voltage distribution network. Background technique [0002] In the three-phase four-wire system, large-scale shopping malls, office buildings, and residential quarters continue to emerge, which contain a lot of single-phase nonlinear loads, which will generate a large number of harmonics during work, which will have a certain impact on the power grid. The third harmonic content in the single-phase nonlinear load is very large, resulting in a large flow of the third harmonic current in the neutral line. In addition, the fundamental zero-sequence component caused by the unbalanced three-phase load also flows in the neutral line. Often the current in the neutral conductor exceeds the current in the phase conductors. When designing the distribution network, the cross section of the neutral wire is usually th...

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Problems solved by technology

On the other hand, the operating conditions of the low-voltage distribution network are relatively complex, and voltage imbalance and distortion often occur. The inverter compensation current interacts with the output voltage, and the output active power may be negative, that is, the inverter absorbs active power

If the absorbed power is larger than the loss of switching devices, since the structure uses uncontrolled rectification to provide DC power for the inverter, the electric energy is irreversible, which will lead to an increase in the voltage of the DC side and easily cause damage to the equipment.

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