| 1. |
- Besselink, Bart, et al.
(författare)
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Controllability of a class of networked passive linear systems
- 2013
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Ingår i: Proceedings of the 52nd IEEE Conference on Decision and Control, Florence, Italy. - : IEEE conference proceedings. ; , s. 4901-4906
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Konferensbidrag (refereegranskat)abstract
- In this paper, controllability properties of networks of diffusively coupled linear systems are considered through the controllability Gramian. For a class of passive linear systems, it is shown that the controllability Gramian can be decomposed into two parts. The first part is related to the dynamics of the individual systems whereas the second part is dependent only on the interconnection topology, allowing for a clear interpretation and efficient computation of controllability properties for a class of networked systems. Moreover, a relation between symmetries in the interconnection topology and controllability is given. The results are illustrated by an example.
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| 2. |
- Ishizaki, Takayuki, et al.
(författare)
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Dissipativity-Preserving Model Reduction for Large-Scale Distributed Control Systems
- 2015
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Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 60:4, s. 1023-1037
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Tidskriftsartikel (refereegranskat)abstract
- We propose a dissipativity-preserving structured model reduction method for distributed control systems. As a fundamental tool to develop structured model reduction, we first establish dissipativity-preserving model reduction for general linear systems on the basis of a singular perturbation approximation. To this end, by deriving a tractable expression of singular perturbation models, we characterize dissipativity preservation in terms of a projection-like transformation of storage functions, and we show that the resultant approximation error is relevant to the sum of neglected eigenvalues of an index matrix. Next, utilizing this dissipativity-preserving model reduction, we develop a structured controller reduction method for distributed control systems. The major significance of this method is to preserve the spatial distribution of dissipative controllers and to provide an a priori bound for the performance degradation of closed-loop systems in terms of the H-2-norm. The efficiency of the proposed method is verified through a numerical example of vibration suppression control for interconnected second-order systems.
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| 3. |
- Ishizaki, Takayuki, et al.
(författare)
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Modularity in Design of Dynamical Network Systems : Retrofit Control Approach
- 2021
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Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 66:11, s. 5205-5220
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we develop a modular design method of decentralized controllers for linear dynamical network systems, where multiple subcontroller designers aim at individually regulating their local control performance with accessibility only to their respective subsystem models. First, we derive a constrained version of the Youla parameterization that characterizes all retrofit controllers for a single subcontroller, defined as an add-on-type subcontroller that manages a subsystem. The resultant feedback system is kept robustly stable for any variation in the neighboring subsystems, other than the subsystem of interest, provided that the original system is stable prior to implementing the retrofit control. Subsequently, we find out a unique internal structure of the retrofit controllers, assuming that the interaction input signal from the neighboring subsystems is measurable. Furthermore, we show that the simultaneous implementation of multiple retrofit controllers, designed by individual subcontroller designers, can improve the upper bound of the overall control performance. Finally, the practical significance of the method is demonstrated via an illustrative example of frequency regulation using the IEEE 68-bus power system model.
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| 4. |
- Ishizaki, Takayuki, et al.
(författare)
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Retrofit control : Localization of controller design and implementation
- 2018
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Ingår i: Automatica. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0005-1098 .- 1873-2836. ; 95, s. 336-346
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a retrofit control method for stable network systems. The proposed approach is a control method that, rather than an entire system model, requires a model of the subsystem of interest for controller design. To design the retrofit controller, we use a novel approach based on hierarchical state-space expansion that generates a higher-dimensional cascade realization of a given network system. The upstream dynamics of the cascade realization corresponds to an isolated model of the subsystem of interest, which is stabilized by a local controller. The downstream dynamics can be seen as a dynamical model representing the propagation of interference signals among subsystems, the stability of which is equivalent to that of the original system. This cascade structure enables a systematic analysis of both the stability and control performance of the resultant closed-loop system. The resultant retrofit controller is formed as a cascade interconnection of the local controller and an output rectifier that rectifies an output signal of the subsystem of interest so as to conform to an output signal of the isolated subsystem model while acquiring complementary signals neglected in the local controller design, such as interconnection signals from neighboring subsystems. Finally, the efficiency of the retrofit control method is demonstrated through numerical examples of power systems control and vehicle platoon control.
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| 5. |
- Jouini, Taouba Kaouther, et al.
(författare)
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Input and state constrained inverse optimal control with application to power networks
- 2023. - 2
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Ingår i: IFAC-PapersOnLine. - 9781713872344 ; , s. 5451-5456
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Konferensbidrag (refereegranskat)abstract
- We study input and state constrained inverse optimal control problems starting from a stabilizing controller with a control Lyapunov function, where the goal is to make the controller an explicit solution of the resulting constrained optimal control problem. For an appropriate cost design and initial states for which a sublevel set of the Lyapunov function is contained in the state constraint set and the initial input lies on an ellipsoid inside the input constraint set, we show that the stabilizing controller solves the constrained optimal control problem. Compared to the state-of-the-art, we avoid solving nonlinear optimization problems evaluated pointwise, i.e., for every state, or in a repetitive fashion, i.e., at each time step. We apply our theoretical results to study the angular droop control studied in (Jouini et al., 2022) of an inverter-based power network. For this, we accommodate the constraints on the angle and power generation and exemplify our approach through a two-inverter case study.
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| 6. |
- Lefeber, Erjen, et al.
(författare)
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A Robust Observer with Gyroscopic Bias Correction for Rotational Dynamics
- 2023
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Ingår i: IFAC-PapersOnLine. - 2405-8963. - 9781713872344 ; 56:2, s. 1641-1648
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Konferensbidrag (refereegranskat)abstract
- We propose an observer for rotational dynamics subject to directional and gyroscopic measurements, which simultaneously estimates the gyroscopic biases and attitude rates. We show uniform almost global asymptotic and local exponential stability of the resulting error dynamics, implying robustness against bounded disturbances. This robustness is quantified with respect to a popular nonlinear complementary filter in quantitative simulation studies, and we explore how the measurement noise propagates to the asymptotic errors as a function of tuning.
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| 7. |
- Sadamoto, Tomonori, et al.
(författare)
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Distributed Design of Locally Stabilizing Controllers for Large-Scale Networked Linear Systems
- 2015
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Ingår i: 2015 IEEE CONFERENCE ON CONTROL AND APPLICATIONS (CCA 2015). - : IEEE conference proceedings. - 9781479977871 ; , s. 1835-1840
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Konferensbidrag (refereegranskat)abstract
- In this paper, we consider designing locally stabilizing controllers, each of which stabilizes each disconnected subsystem, in a distributed manner for large-scale networked linear systems. To this end, we design a low-dimensional hierarchical distributed compensator such that the L-2-performance of the closed-loop system improves as long as that of the locally stabilizing controllers improves. We solve a controller reduction problem where the approximation error of the low-dimensional compensator gets better as long as the performance of the locally stabilizing controllers improves, while preserving the hierarchical distributed structure of the original compensator. Finally, we demonstrate the efficiency of the proposed method through a numerical example of a power network.
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| 8. |
- Sadamoto, Tomonori, et al.
(författare)
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Dynamic Modeling, Stability, and Control of Power Systems With Distributed Energy Resources : Handling Faults Using Two Control Methods in Tandem
- 2019
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Ingår i: IEEE Control Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 1066-033X. ; 39:2, s. 34-65
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Tidskriftsartikel (refereegranskat)abstract
- This article presents an end-to-end differential algebraic model of a power system in its entirety, including synchronous generators, wind farms, solar farms, energy storage, power electronics converters, and controllers for each device. Distributed energy resources (DERs) and power electronics devices are shown to affect small-signal stability and the dynamic performance of the grid. The article then presents a two-layer control architecture for future grids, where one layer consists of decentralized plug-and-play controllers for power electronics converter control of DERs, and another layer is composed of system-wide distributed controllers actuated through the generators.
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| 9. |
- Sadamoto, Tomonori, et al.
(författare)
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Retrofitting State Feedback Control of Networked Nonlinear Systems Based on Hierarchical Expansion
- 2016
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Ingår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509018376 ; , s. 3432-3437
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a systematic method to design retrofit controllers for networked nonlinear systems. The retrofit controller, which consists of a linear state feedback controller and a dynamical compensator, can improve the control performance for a subsystem of interest, while guaranteeing the stability of the whole closed-loop system. Towards the retrofit controller design, we introduce a type of state-space expansion, called hierarchical expansion. The cascade structure of the hierarchical expansion realization enables the systematic design of a stabilizing controller for a low-dimensional linear model extracted from the subsystem of interest. As a result, we can design a retrofit controller without explicit consideration of the dynamics of subsystems other than the subsystem of interest. The effectiveness of the proposed method is demonstrated through a power network example.
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| 10. |
- Sasahara, Hampei, et al.
(författare)
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Disconnection-aware Attack Detection in Networked Control Systems
- 2020
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Ingår i: IFAC PAPERSONLINE. - : Elsevier BV. - 2405-8963. ; , s. 3515-3520
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Konferensbidrag (refereegranskat)abstract
- This study deals with security issues in dynamical networked control systems. The goal is to establish a unified framework of the attack detection stage, which includes the four processes of monitoring the system state, making a decision based on the monitored signal, disconnecting the corrupted subsystem, and operating the remaining system during restoration. This paper, in particular, considers a disconnection-aware attack detector design problem. Traditionally, observer-based attack detectors are designed based on the system model with a fixed network topology and cannot cope with a change of the topology caused by disconnection. The disconnection-aware design problem is mathematically formulated and a solution is proposed in this paper. A numerical example demonstrates the effectiveness of the proposed detector through an inverter-based voltage control system in a benchmark model.
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