15 research outputs found
Distributed PI-Control with Applications to Power Systems Frequency Control
This paper considers a distributed PI-controller for networked dynamical
systems. Sufficient conditions for when the controller is able to stabilize a
general linear system and eliminate static control errors are presented. The
proposed controller is applied to frequency control of power transmission
systems. Sufficient stability criteria are derived, and it is shown that the
controller parameters can always be chosen so that the frequencies in the
closed loop converge to nominal operational frequency. We show that the load
sharing property of the generators is maintained, i.e., the input power of the
generators is proportional to a controller parameter. The controller is
evaluated by simulation on the IEEE 30 bus test network, where its
effectiveness is demonstrated
Inherent Synchronization in Electric Power Systems with High Levels of Inverter-based Generation
The synchronized operation of power generators is the foundation of electric
power system stability and key to the prevention of undesired power outages and
blackouts. Here, we derive the condition that guarantees synchronization in
electric power systems with high levels of inverter-based generation when
subjected to small perturbations, and perform a parametric sensitivity to
understand synchronization with varied types of generators. Contrary to the
popular belief that achieving a stable synchronized state is tied chiefly to
system inertia, our results instead highlight the critical role of generator
damping in achieving this pivotal state. Additionally, we report the
feasibility of operating interconnected electric grids with a 100% power
contribution from renewable generation technologies with assured system
synchronization. The findings of this paper can set the basis for the
development of advanced control architectures and grid optimization methods and
has the potential to further pave the path towards the decarbonization of the
electric power sector
An Online Data-Driven Method for Microgrid Secondary Voltage and Frequency Control with Ensemble Koopman Modeling
Low inertia, nonlinearity and a high level of uncertainty (varying topologies
and operating conditions) pose challenges to microgrid (MG) systemwide
operation. This paper proposes an online adaptive Koopman operator optimal
control (AKOOC) method for MG secondary voltage and frequency control. Unlike
typical data-driven methods that are data-hungry and lack guaranteed stability,
the proposed AKOOC requires no warm-up training yet with guaranteed
bounded-input-bounded-output (BIBO) stability and even asymptotical stability
under some mild conditions. The proposed AKOOC is developed based on an
ensemble Koopman state space modeling with full basis functions that combines
both linear and nonlinear bases without the need of event detection or
switching. An iterative learning method is also developed to exploit model
parameters, ensuring the effectiveness and the adaptiveness of the designed
control. Simulation studies in the 4-bus (with detailed inner-loop control) MG
system and the 34-bus MG system showed improved modeling accuracy and control,
verifying the effectiveness of the proposed method subject to various changes
of operating conditions even with time delay, measurement noise, and missing
measurements.Comment: Accepted by IEEE Transactions on Smart Grid for future publicatio
Control of Synchronization in two-layer power grids
In this work we suggest to model the dynamics of power grids in terms of a
two-layer network, and use the Italian high voltage power grid as a
proof-of-principle example. The first layer in our model represents the power
grid consisting of generators and consumers, while the second layer represents
a dynamic communication network that serves as a controller of the first layer.
In particular, the dynamics of the power grid is modelled by the Kuramoto model
with inertia, while the communication layer provides a control signal for
each generator to improve frequency synchronization within the power grid. We
propose different realizations of the communication layer topology and
different ways to calculate the control signal. Then we conduct a systematic
survey of the two-layer system against a multitude of different realistic
perturbation scenarios, such as disconnecting generators, increasing demand of
consumers, or generators with stochastic power output. When using a control
topology that allows all generators to exchange information, we find that a
control scheme aimed to minimize the frequency difference between adjacent
nodes operates very efficiently even against the worst scenarios with the
strongest perturbations
Synchronization in Complex Oscillator Networks and Smart Grids
The emergence of synchronization in a network of coupled oscillators is a
fascinating topic in various scientific disciplines. A coupled oscillator
network is characterized by a population of heterogeneous oscillators and a
graph describing the interaction among them. It is known that a strongly
coupled and sufficiently homogeneous network synchronizes, but the exact
threshold from incoherence to synchrony is unknown. Here we present a novel,
concise, and closed-form condition for synchronization of the fully nonlinear,
non-equilibrium, and dynamic network. Our synchronization condition can be
stated elegantly in terms of the network topology and parameters, or
equivalently in terms of an intuitive, linear, and static auxiliary system. Our
results significantly improve upon the existing conditions advocated thus far,
they are provably exact for various interesting network topologies and
parameters, they are statistically correct for almost all networks, and they
can be applied equally to synchronization phenomena arising in physics and
biology as well as in engineered oscillator networks such as electric power
networks. We illustrate the validity, the accuracy, and the practical
applicability of our results in complex networks scenarios and in smart grid
applications