1,720,967 research outputs found
Local and Wide-Area Sliding Mode State Observation, Fault Reconstruction and Control with Application to Modern Power Systems
Full text linkThe present thesis summarises the research activity carried our by the PhD candidate Gianmario
Rinaldi from October 2016 to September 2019 at the Department of Electrical, Computer and Biomedical
Engineering at the University of Pavia, Italy.
In recent years, radical changes are taking place to power systems. A worldwide consensus has
been reached for the reduction of greenhouse effects, by promoting the growth of renewable energy
sources in power grids. Therefore, a special shared interest has been raised amongst researchers and
practitioners to turn the existing power grids into smarter and more reliable ones, which are able to
safely, efficiently, an reliably integrate the growing renewable energy sources.
Supervisory Control And Data Acquisition (SCADA) has been the conventional control and state
estimation methodology practically used in the last few decades. Recent progress in computer science
and electronic technologies has opened the door to the implementation of the so-called Wide Area
Measurement Systems (WAMS). In particular, with a widespread deployment of Phasor Measurement
Units (PMUs), a more accurate depiction of the state in power systems has become achievable
in practice.
Latest advances in computer science and electronic technologies have laid the groundwork for
the conception of the so-called cyber-attacks, which can be defined as computer-based algorithms
capable of destabilising the power network by compromising the collected measurements to be sent
to a control centre, attack the communication networks, or alter and delay the control variables.
In order to turn the existing power system into a smarter one capable of both harmoniously
integrating renewable power sources and efficiently and safely dealing with faults and cyber-attacks,
the attention is now focused on the following relevant research areas:
The design and assessment of more accurate, robust and dynamic state estimators in power systems,
which are able to obtain a near-real time depiction of all the state variables, instrumental
in enhancing the monitoring of the networks.
The implementation of timely fault detection, reconstruction and mitigation methodologies,
devoted to preserve the stability of the entire power network, thus preventing wide-spread
outages, blackouts, and degradations of the power quality.
The design of identification schemes to determine key-properties of the components in power
system context.
The design and assessment of novel control approaches devoted to both regulate the frequency
deviations and minimise the cost of the power generation. These control schemes are also required to be robust to possible faults, disturbances, and uncertainties affecting the power
systems.
The present thesis aims to fit into the aforementioned promising research areas in power systems. In
particular, four challenges are addressed:
The first addressed challenge considers the design of robust state estimators which are able to
depict in near real time the state of the overall power systems to globally enhance the monitoring
of the power systems, thus reducing the number of the deployed sensors. The undertaken
analysis started at the local level and then consider the power system as a large-scale system.
The second addressed challenge focuses on the design of fault detection, reconstruction, and
mitigation approaches devoted to enhance the resilience of the power network.
The third addressed challenge considers the design and the assessment of robust sliding mode
observer-based controllers which are capable of regulating the frequencies in power systems
whilst minimising the cost associated with the generators.
Finally, the fourth addressed challenges examines the identification of the relative degree properties
with application to electrical and power systems frameworks.
Furthermore, the outline of the present thesis is coherent with the development of the contributions
illustrated above
Automatic identification of the relative degree of nonlinear systems: Application to sliding mode control design and experimental assessment
No full textThis paper deals with the design and the experimental-based assessment of a scheme to identify the relative degree of a system in order to correctly design the controller. The system is assumed to have an unknown dynamics, and the output is measured in a discrete-time fashion. Provided that a prescribed input signal is applied, it is proven that a set of inequalities holds only for the
th time derivative of the output, where
is the relative degree. A practical algorithm for the relative degree identification is also formulated, which is written in a pseudo-code notation. In the paper, a special reference is made to the design of sliding mode controllers. Specifically, a self-configuring sliding mode control strategy is presented, which automatically selects the controller in case of changes to the relative degree. The scheme is implemented in a practical set-up composed of a lab-scale overhead crane mechanically coupled with a 12 Volts DC motor. The aim is to identify the relative degree of the position of the crane (the output), with respect to the DC motor armature voltage (the control input). The experimental results reveal the high accuracy of the proposed strategy for the identification of the relative degree
Design and Experimental Validation of an Embedded Sliding Mode Controller for Voltage Regulation With SEPIC Converters
No full textThis article addresses the challenge of regulating the output voltage in single-end primary inductor converters (SEPICs) and introduces a practical solution based on the generation of second-order suboptimal sliding modes (2-SOSM). In contrast to the common assumption of a lossless SEPIC, in this article, a lossy SEPIC is explored. A concise mathematical representation of its model is presented, and the equilibrium point is explicitly defined. Using only the output voltage as a measurement, it is proven that the proposed 2-SOSM strategy achieves finite-time convergence of the output voltage with its reference. The proposed method effectively handles saturation constraints on the control variable, ensuring that the SEPIC duty ratio remains between 0 and 1. Furthermore, the approach proves to be robust to variations in the load resistor. The experimental analysis validates the effectiveness of our proposal and highlights its practical benefits. A comparison with a standard proportional integral control on an embedded platform underscores the superiority of the adopted approach
Decentralised Model Predictive Control with Integral Sliding Mode for Frequency Regulation in Power Grids
No full text
Decentralized Integral Sliding Mode Approach for Frequency Control and Unknown Demand Reconstruction in Power Systems
No full textSliding Mode Observer-Based Finite Time Control Scheme for Frequency Regulation and Economic Dispatch in Power Grids
No full textIn this brief, a novel sliding mode (SM) observer-based scheme is proposed to achieve frequency regulation and economic dispatch (ED) in power grids composed of interconnection of generators and load buses. The ED problem is addressed in two steps. Assuming only the voltage phase angles are measured, in the first step a network of heterogeneous SM observers, suitably interconnected in a distributed fashion, is created to estimate both frequency deviations and unknown power levels associated with each bus. In the second step, the observer scheme is coupled with an SM control strategy which is able to reach the optimal value of the control input in each generator bus in finite time. The scheme is assessed via the IEEE 39 bus benchmark, and a comparison with existing control methods is provided
Sliding Mode Based Dynamic State Estimation for Synchronous Generators in Power Systems
Full text linkThis is the author accepted manuscript. The final version is available from IEEE via the DOI in this record This letter deals with the design of a robust sliding mode observer for dynamic state estimation applied to synchronous generators in power systems. Assuming only the frequency deviation of the generator is measured via phasor measurement units, we use a robust sliding mode estimation technique to dynamically reconstruct the rotor angle and the transient voltage. The adopted estimation technique is insensitive to matched bounded uncertainties affecting the dynamics of the synchronous generator. A stability analysis and tuning rules for the observer are also provided. Numerical simulations confirm the validity of the approach
Third Order Sliding Mode Observer-Based Approach for Distributed Optimal Load Frequency Control
No full textIn this letter, we propose a third order sliding mode observer-based approach for optimal load frequency control in power networks which are partitioned into control areas. We model each area by an equivalent generator including second-order turbine-governor dynamics. Assuming to measure only few state variables, we design two third order sliding mode observers for each control area to locally estimate the unmeasured states. We introduce also a distributed second order sliding mode control strategy, which makes use of the estimates coming from the observers and achieves both frequency regulation and minimization of generation costs. The simulation results confirm the validity of the proposed approach
Distributed observers for state estimation in power grids
No full textIn this paper an estimation scheme for a power grid based on distributed observers is presented. Assuming that the only measurements available are the generator phase angles, our approach allows us to consider an observer for each bus of the power grid, exploiting on only knowledge of local information about the power system. In particular, we design a super-twisting-like sliding mode observer for each generator bus and a so-called “algebraic observer” for each load bus, based on a distributed iterative algorithm. The proposed scheme is able to deal with power grid changes that may involve the insertion of new generators or new power transmission lines affecting the grid topology. Numerical examples and simulations confirm the validity of our approach
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