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Distributed averaging-based integral (DAI) controllers are becoming increasingly popular in power system applications. The literature has thus far primarily focused on disturbance rejection, steady-state optimality and adaption to complex physical system models without considering uncertainties on the cyber and communication layer nor their effect on robustness and performance. In this paper, we derive sufficient delay-dependent conditions for robust stability of a secondary-frequency-DAI-controlled power system with respect to heterogeneous communication delays, link failures and packet losses. Our analysis takes into account both constant as well as fast-varying delays, and it is based on a common strictly decreasing Lyapunov–Krasovskii functional. The conditions illustrate an inherent trade-off between robustness and performance of DAI controllers. The effectiveness and tightness of our stability certificates are illustrated via a numerical example based on Kundur’s four-machine-two-area test system.
Synthesizing Sparse and Delay-Robust Distributed Secondary Frequency Controllers for Microgrids
(2020)
Consensus-based control schemes experience increasing popularity in the context of secondary frequency control in microgrids. Fundamental aspects in their practical implementation are the design of the communication topology as well as robustness with respect to both time-varying communication delays and exogenous disturbances. Motivated by this, we propose a design procedure for a consensus-based secondary frequency controller that ensures robustness with respect to heterogeneous fast-varying communication delays and simultaneously provides the option to trade off the L₂-gain performance against the number of required communication links. Our design criterion is equilibrium-independent and based on the Lyapunov-Krasovskii method for interval time-varying delays together with the descriptor method. The efficacy of the proposed approach is demonstrated by using numerical experiments on the CIGRE benchmark medium-voltage distribution network.
The increasing ease of obtaining and processing data together with the growth in system complexity has sparked the interest in moving from conventional model-based control design toward data-driven concepts. Since in many engineering applications time delays naturally arise and are often a source of instability, we contribute to the data-driven control field by introducing data-based formulas for state feedback control design in linear discrete-time time-delay systems with uncertain delays. With the proposed approach, the problems of system stabilization as well as of guaranteed cost and H∞ control design are treated in a unified manner. Extensions to determine the system delays and to ensure robustness in the event of noisy data are also provided
Consensus-based distributed secondary frequency
control schemes have the potential to simultaneously ensure
real-time frequency restoration and economic dispatch in future
power systems with large shares of renewable energy sources.
Yet, due to their distributed nature these control schemes
critically depend on communication between units and, thus,
robustness with respect to communication uncertainties is
crucial for their reliable operation. Furthermore, when applied
in bulk power systems the control design and analysis should
take higher-order turbine-governor dynamics of the generation
units explicitly into account. Both aspects have not been
addressed jointly in the existing literature. Motivated by this,
we derive conditions for robust stability of a consensus-based
distributed frequency control scheme applied to a power system
model with second-order turbine-governor dynamics in the
presence of heterogeneous time-varying communication delays
and dynamic communication topology. The result is established
by a novel coordinate transformation and reduction to eliminate
the invariant subspace in the closed-loop dynamics and by
constructing a strict common Lyapunov-Krasovskii functional.