TITLE:
Virtual Synchronous Generator: A Control Strategy to Improve Dynamic Frequency Control in Autonomous Power Systems
AUTHORS:
Miguel Torres, Luiz A. C. Lopes
KEYWORDS:
Frequency Control; Mini-Grid; Energy Storage; Inverter
JOURNAL NAME:
Energy and Power Engineering,
Vol.5 No.2A,
April
29,
2013
ABSTRACT: Ideally, diesel hybrid autonomous power systems would operate with
high penetration of renewable energy sources such as wind and photovoltaic to
minimize fuel consumption. However, since these are inherently intermittent and
fluctuating, the grid-forming diesel engine generator sets are usually required
to operate with larger amounts of spinning reserve, often at low loading
conditions what tends to increases operating and maintenance costs. Frequency
stability is of great concern in “small” systems, such as mini-grids, where any
individual generator in-feed represents a substantial portion of the total
demand. There, the initial rate of change of frequency is typically larger and
a lower value of frequency can be reached in a shorter time than in
conventional systems with all generation supplied by rotating machines,
possibly resulting in under-frequency load shedding and tripping of renewable
energy generators. The first part of this paper, discusses some general
concepts regarding frequency stability in a diesel hybrid mini-grid and how
energy storage systems can be used to enhance system performance. Then, a
particular technique based on a virtual synchronous generator is presented and
its effectiveness is demonstrated with simulation results.