4,301 research outputs found
An internal model approach to (optimal) frequency regulation in power grids with time-varying voltages
This paper studies the problem of frequency regulation in power grids under
unknown and possible time-varying load changes, while minimizing the generation
costs. We formulate this problem as an output agreement problem for
distribution networks and address it using incremental passivity and
distributed internal-model-based controllers. Incremental passivity enables a
systematic approach to study convergence to the steady state with zero
frequency deviation and to design the controller in the presence of
time-varying voltages, whereas the internal-model principle is applied to
tackle the uncertain nature of the loads.Comment: 16 pages. Abridged version appeared in the Proceedings of the 21st
International Symposium on Mathematical Theory of Networks and Systems, MTNS
2014, Groningen, the Netherlands. Submitted in December 201
Global Tracking Passivity--based PI Control of Bilinear Systems and its Application to the Boost and Modular Multilevel Converters
This paper deals with the problem of trajectory tracking of a class of
bilinear systems with time--varying measurable disturbance. A set of matrices
{A,B_i} has been identified, via a linear matrix inequality, for which it is
possible to ensure global tracking of (admissible, differentiable) trajectories
with a simple linear time--varying PI controller. Instrumental to establish the
result is the construction of an output signal with respect to which the
incremental model is passive. The result is applied to the boost and the
modular multilevel converter for which experimental results are given.Comment: 9 pages, 10 figure
Integral control of port-Hamiltonian systems: non-passive outputs without coordinate transformation
In this paper we present a method for the addition of integral action to
non-passive outputs of a class of port-Hamiltonian systems. The proposed
integral controller is a dynamic extension, constructed from the open loop
system, such that the closed loop preserves the port-Hamiltonian form. It is
shown that the controller is able to reject the effects of both matched and
unmatched disturbances, preserving the regulation of the non-passive outputs.
Previous solutions to this problem have relied on a change of coordinates
whereas the presented solution is developed using the original state vector
and, therefore, retains its physical interpretation. In addition, the resulting
closed loop dynamics have a natural interpretation as a Control by
Interconnection scheme.Comment: 8 pages, 2 figure
Modeling and Control of High-Voltage Direct-Current Transmission Systems: From Theory to Practice and Back
The problem of modeling and control of multi-terminal high-voltage
direct-current transmission systems is addressed in this paper, which contains
five main contributions. First, to propose a unified, physically motivated,
modeling framework - based on port-Hamiltonian representations - of the various
network topologies used in this application. Second, to prove that the system
can be globally asymptotically stabilized with a decentralized PI control, that
exploits its passivity properties. Close connections between the proposed PI
and the popular Akagi's PQ instantaneous power method are also established.
Third, to reveal the transient performance limitations of the proposed
controller that, interestingly, is shown to be intrinsic to PI passivity-based
control. Fourth, motivated by the latter, an outer-loop that overcomes the
aforementioned limitations is proposed. The performance limitation of the PI,
and its drastic improvement using outer-loop controls, are verified via
simulations on a three-terminals benchmark example. A final contribution is a
novel formulation of the power flow equations for the centralized references
calculation
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