Virtual synchronous generator low voltage ride through control method and device

Abstract

The embodiment of the invention provides a virtual synchronous generator low voltage ride through control method and device, and the method comprises the steps: enabling a virtual synchronous generator to operate a grid-connected inverter control algorithm based on a VSG, to operate a grid-connected pre-synchronization algorithm after entering a first steady state, to execute automatic grid connection after being synchronized with a power grid, and to cut off the grid-connected pre-synchronization algorithm; inputting grid-connected active power and reactive power after grid connection, so that the virtual synchronous generator is increased to a given value by a slope curve and enters a second steady state; when a power grid fault is detected, the fault type and the drop depth are determined through a fault detection module, a virtual resistor is switched in, grid-connected active power output is adjusted, the control capability of the VSG on the current is improved through an additional current loop, and the operation characteristics of the simulated SG in an under-excitation state are kept; and when the power grid fault is recovered, the output omega of the active loop and the output E of the reactive loop of the virtual synchronous generator are recovered to a normal operation state after being delayed for a plurality of periods. The stability of the VSG control system is improved when the power grid voltage breaks down.

Description

technical field [0001] This document relates to the technical field of virtual synchronous generators, in particular to a method and device for low voltage ride-through control of virtual synchronous generators. Background technique [0002] In recent years, energy and environmental issues have become a huge challenge for the development of human society. New energy sources have been widely used, and more and more distributed power sources have begun to be connected to the grid. With the expansion of the capacity and scale of the distributed power grid connected to the grid, the proportion of synchronous generators in the grid is getting lower and lower, but the advantages of synchronous generators in the grid are outstanding: first, the inertia of the rotor makes it have a strong Robustness, the damping between the machines limits the rapid changes of their states; secondly, the synchronous generator can directly participate in the voltage regulation and frequency regulatio...

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Problems solved by technology

However, this control scheme still has overcurrent during the low voltage ride through process, and the peak value of the transient current is relatively large. At the same time, the virtual resistance at the VSG output increases the impedance of the filter and the transmission network when the VSG is running normally, changing the filter and the impedance characteristics of the transmission network will bring the following effects: 1) Increase the output impedance of VSG, resulting in a decrease in the synchronous power of VSG, which is not conducive to the stability of VSG; 2) Change the active and reactive power and the potential phase of VSG -The coupling relationship of the amplitude; 3) The voltage drop of the VSG normal working current on the virtual resistance will affect the performance of the VSG under normal grid conditions

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