Abstract
The virtual synchronous generator (VSG) introduces rotational inertia and damping through the droop control to take part in frequency regulation of the grid. By building the VSG model, the VSG controller, including both the frequency controller and the excitation controller, are analysed and designed. The analysis shows that the large phase difference Δθ between the VSG voltage and the grid voltage at the grid-tied moment may produce large power and damage the VSG. The proposed pre-synchronization control minimizes the phase difference, which is implemented by replacing Δθ with sinΔθ to avoid any step change from Δθ. The proposed method is able to simplify control, shorten pre-synchronization tracking time, and achieve high accuracy without a phase-lock loop. The built 12 kW VSG simulation and prototype verify the theoretical analysis, the proposed control and its associated design.
Highlights
As more and more distributed power sources are integrated into the power grid, their impacts on the grid are receiving more extensive attention
The droop control can make the inverter simulate some external characteristics of synchronous generator enabling the grid-tied inverter to involve in the grid system primary frequency regulation and voltage regulation, but the droop control does not have the capability of Manuscript received 20 December, 2019; accepted 14 September, 2020
In order to enable grid-connected inverters to provide more functions and services to the grid, such as the frequency and voltage regulation, black-start, etc., virtual inertia and virtual damping are introduced into the grid-tied inverter control strategy, and they make the inverter act as a virtual synchronous generator (VSG) [5]–[7]
Summary
Xuhai Chen1, Yiwang Zhang2, Jiqing Dong2 , Xingkui Mao2, *, Jiaqiao Chen1, Buyin Wen2, Zhe Zhang3 1PowerChina Fujian Electric Power Engineering Co., Ltd, Fuzhou, China Index Terms—Virtual synchronous generator (VSG); Pre-synchronization control; Droop control; Energy storage.
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