466 research outputs found
Performance evaluation of secondary control policies with respect to digital communications properties in inverter-based islanded microgrids
A key challenge for inverted-based microgrids working in islanded mode is to maintain their own frequency and voltage to a certain reference values while regulating the active and reactive power among distributed generators and loads. The implementation of frequency and voltage restoration control policies often requires the use of a digital communication network for real-time data exchange (tertiary control covers the coordi- nated operation of the microgrid and the host grid). Whenever a digital network is placed within the loop, the operation of the secondary control may be affected by the inherent properties of the communication technology. This paper analyses the effect that properties like transmission intervals and message dropouts have for four existing representative approaches to secondary control in a scalable islanded microgrid. The simulated results reveals pros and cons for each approach, and identifies threats that properly avoided or handled in advance can prevent failures that otherwise would occur. Selected experimental results on a low- scale laboratory microgrid corroborate the conclusions extracted from the simulation study.Peer ReviewedPostprint (author's final draft
Robust Decentralized Secondary Frequency Control in Power Systems: Merits and Trade-Offs
Frequency restoration in power systems is conventionally performed by
broadcasting a centralized signal to local controllers. As a result of the
energy transition, technological advances, and the scientific interest in
distributed control and optimization methods, a plethora of distributed
frequency control strategies have been proposed recently that rely on
communication amongst local controllers.
In this paper we propose a fully decentralized leaky integral controller for
frequency restoration that is derived from a classic lag element. We study
steady-state, asymptotic optimality, nominal stability, input-to-state
stability, noise rejection, transient performance, and robustness properties of
this controller in closed loop with a nonlinear and multivariable power system
model. We demonstrate that the leaky integral controller can strike an
acceptable trade-off between performance and robustness as well as between
asymptotic disturbance rejection and transient convergence rate by tuning its
DC gain and time constant. We compare our findings to conventional
decentralized integral control and distributed-averaging-based integral control
in theory and simulations
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