Compensating for the effects of reduced synchronous inertia on frequency stability using virtual synchronous generators
Zhu, Jeffrey
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https://hdl.handle.net/2142/104813
Description
Title
Compensating for the effects of reduced synchronous inertia on frequency stability using virtual synchronous generators
Author(s)
Zhu, Jeffrey
Issue Date
2019-04-12
Director of Research (if dissertation) or Advisor (if thesis)
Sauer, Peter
Department of Study
Electrical & Computer Eng
Discipline
Electrical & Computer Engr
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
virtual synchronous generator, frequency stability, inertia response,
Abstract
The power grid has traditionally been dominated by large synchronous generators which have provided frequency stability through their inertia and governor responses. As more renewable energy sources (RES), particularly wind and solar, are added to the grid, they displace synchronous generators. Many of these RES generators do not inherently contribute inertia to the system, so their inclusion in the generation portfolio decreases the aggregate inertia of the grid. Low inertia makes a grid more vulnerable to fast frequency dynamics in the wake of a disturbance. A virtual synchronous generator (VSG) can compensate for the displacement of synchronous generators by emulating the inertia response and governor response of a synchronous generator. This thesis reviews prior investigations into VSGs and then uses a series of simulations to examine how synchronous inertia, VSG sizing, control parameters and battery speed affect the frequency dynamics after a disturbance. The main findings of this thesis are as follows: VSGs have some inherent delay, so a certain amount of synchronous inertia will still be needed even if a VSG is installed. Batteries are an attractive technology to use with VSGs because their fast response times can create VSGs with low delays. A VSG with a faster response offers more benefit to the grid. The best way to control a VSG is to combine strong primary frequency control with inertia control. A VSG that is powerful enough to match the power imbalance caused by a disturbance can stabilize the frequency on its own before governors can typically act, but even a less powerful VSG can benefit the grid by slowing the frequency dynamics following a disturbance.
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