Improved Control Method of Virtual Synchronous Generator under Symmetrical Voltage Dip

Abstract

The invention discloses a control method for a virtual synchronous generator with a reactive compensation function under symmetrical voltage sag, which belongs to the field of microgrid power qualitycontrol. The method comprises the steps that for an overcurrent phenomenon caused by a symmetrical voltage sag fault in a power grid, a given voltage amplitude E0 and power grid voltage value U are selected in a reactive-voltage regulation control loop to ensure that fault current is within a reasonable range during the voltage sag of the power grid; and in an active-frequency control structure, aconstant given power value is improved to an adaptive value which varies according to the voltage variation of the power grid, which reduces surge current caused by imbalance between required power and VSG output power. A reactive power reference value setting method is provided. Reactive power support is provided for the power grid with the maximum capacity of VSG, which is beneficial to the voltage recovery of the power grid. The control method provided by the invention makes up for the blank of the control policy of the virtual synchronous generator when the power grid fails, and improvesthe stability of a system.

Description

technical field [0001] The invention relates to a control method of a virtual synchronous generator with a reactive power compensation function under a symmetrical voltage sag, and belongs to the field of power quality control of a microgrid. Background technique [0002] Due to the existence of rotating parts, the traditional synchronous generator has a moment of inertia. When the power grid fails, the synchronous generator can release the kinetic energy stored in the rotating parts to the power grid, thereby ensuring the stability of the power grid. However, due to the gradual increase in the penetration rate of distributed power sources, traditional inverters without damping and inertia have become the main interface for them to be connected to the power grid. adverse effects. [0003] In recent years, a new inverter control method, the virtual synchronous generator control strategy, has attracted extensive attention from scholars at home and abroad. The basic idea is t...

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Problems solved by technology

[0004] However, there are still relatively few studies on the control strategy of virtual synchronous generators in the case of grid abnormalities.

During the actual operation of the actual power system, faults such as voltage sag, three-phase unbalance and harmonic distortion often occur, which have a negative impact on the continuous operation of the VSG (Virtual Synchronous Generator) and the stability of the power grid.

At the same time, the traditional VSG does not have the ability to suppress the fault current in the case of a grid fault, and it cannot provide reactive power support

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