Low-voltage ride through control strategy of virtual synchronous generator

What is it about?

When the VSG technology is employed to distributed power supply and microgrid for grid-connected operation, the stable operation and control performance under grid fault must be considered. In this paper, the reactive power regulation principle of the grid-connected SG is used to ensure that the system can maintain the advantage of SG operation under grid fault. In order to fully inherit the existing research results, the idea of state maintenance is adopted, and the control structure of VSG is improved to avoid the additional smooth handoff algorithm. It can be proved that the proposed control strategy can deal with both symmetric and asymmetric grid voltage drop problems at the same time.

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Why is it important?

We improve the design of droop characteristics, reactive loop and active power loop, the mutual conversion between the normal excitation and under excitation state is effectively accelerated, and some operation problems are also resolved such as the excessive increment of reactive power, the unavoidable impact current, and the enhancement of coupling between active and reactive power loops. In addition, the additional current loop is redesigned with a new orientation method to assist the operation in the under excitation state and suppress the unbalance current without changing the original VSG characteristics.

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