@misc{LorenzMeyerBobtsovOrtegaetal., author = {Lorenz-Meyer, Nicolai and Bobtsov, Alexey and Ortega, Romeo and Nikolaev, Nikolay and Schiffer, Johannes}, title = {PMU-Based Decentralized Mixed Algebraic and Dynamic State Observation in Multi-Machine Power Systems}, series = {IET Generation, Transmission \& Distribution}, volume = {14}, journal = {IET Generation, Transmission \& Distribution}, number = {25}, issn = {1751-8695}, doi = {10.1049/iet-gtd.2020.1275}, pages = {6267 -- 6275}, abstract = {We propose a novel decentralized mixed algebraic and dynamic state observation method for multi-machine power systems with unknown inputs and equipped with Phasor Measurement Units (PMUs). More specifically, we prove that for the third-order flux-decay model of a synchronous generator, the local PMU measurements give enough information to reconstruct algebraically the load angle and the quadrature-axis internal voltage. Due to the algebraic structure a high numerical efficiency is achieved, which makes the method applicable to large scale power systems. Also, we prove that the relative shaft speed can be globally estimated combining a classical Immersion and Invariance (I\&I) observer with—the recently introduced—dynamic regressor and mixing (DREM) parameter estimator. This adaptive observer ensures global convergence under weak excitation assumptions that are verified in applications. The proposed method does not require the measurement of exogenous inputs signals such as the field voltage and the mechanical torque nor the knowledge of mechanical subsystem parameters.}, language = {en} } @misc{MetzkowRuedaEscobedoDoeringetal., author = {Metzkow, Ren{\`e} and Rueda-Escobedo, Juan G. and D{\"o}ring, Daniela and Schiffer, Johannes}, title = {An Internal Model Approach to Robust Current Control of IPMSM Drives with Respect to Unknown and Varying Inductances}, series = {IFAC PapersOnLine}, volume = {53}, journal = {IFAC PapersOnLine}, number = {2}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2020.12.1046}, pages = {14185 -- 14191}, abstract = {Interior permanent magnet synchronous machines (IPMSMs) are well-suited for high-performance applications, such as traction drives in hybrid and electric vehicles. Yet a major challenge to fully exploit their potential is the fact that their self and cross-coupling inductances vary significantly across the operation range. In addition, this variation is difficult to characterize and complicates the design of provably stabilizing and robust controls. Motivated by this, by using an IPMSM model with current dependant inductances together with the internal model principle, a nonlinear current control scheme is derived that renders the equilibrium point of the closed-loop system exponentially stable. Both the control and the stability result only require the knowledge of an upper bound of the gradient of the inductances as well as lower and upper bounds on the inductance values themselves, while their actual evolution can be completely unknown. This is a major advantage compared to existing (PI-based) current control approaches, as it makes costly practices to determine the inductance variations unnecessary. The efficacy of the proposed control scheme is demonstrated in a simulation example.}, language = {en} } @misc{BaiZhangCaietal., author = {Bai, Handong and Zhang, Hongwai and Cai, He and Schiffer, Johannes}, title = {Voltage regulation and current sharing for multi-bus DC microgrids: A compromised design approach}, series = {Automatica}, volume = {142}, journal = {Automatica}, issn = {0005-1098}, doi = {10.1016/j.automatica.2022.110340}, pages = {7}, abstract = {It is well known that accurate current sharing and voltage regulation are both important, yet conflicting control objectives in multi-bus DC microgrids. In this paper a distributed control scheme is proposed, which simultaneously considers these two control objectives via a trade-off factor. This factor permits to adjust the degree of compromise between accurate voltage regulation and current sharing. At the same time, the voltage of a critical node can be precisely regulated. A sufficient condition for closed-loop stability is given and it is shown that the control parameters can always be chosen, such that stability is guaranteed. In addition, the steady state voltage and current deviations relative to their rated values are quantified via suitable metrics. For a given topology and settings of a DC microgrid, a sufficient condition for the existence of the trade-off factor is provided. The results are illustrated by simulation examples.}, language = {en} } @misc{BobtsovOrtegaNikolaevetal., author = {Bobtsov, Alexey and Ortega, Romeo and Nikolaev, Nikolay and Lorenz-Meyer, Nicolai and Schiffer, Johannes}, title = {State Observation of Power Systems Equipped with Phasor Measurement Units: The Case of Fourth Order Flux-Decay Model}, series = {IEEE Transactions on Automatic Control}, volume = {67}, journal = {IEEE Transactions on Automatic Control}, number = {4}, issn = {0018-9286}, doi = {10.1109/TAC.2021.3073887}, pages = {2123 -- 2130}, abstract = {The problem of effective use of phasor measurement units (PMUs) to enhance power systems awareness and security is a topic of key interest. The central question to solve is how to use these new measurements to reconstruct the state of the system. In this article, we provide the first solution to the problem of (globally convergent) state estimation of multimachine power systems equipped with PMUs and described by the fourth-order flux-decay model. This article is a significant extension of our previous result, where this problem was solved for the simpler third-order model, for which it is possible to recover algebraically part of the unknown state. Unfortunately, this property is lost in the more accurate fourth-order model, and we are confronted with the problem of estimating the full state vector. The design of the observer relies on two recent developments proposed by the authors, a parameter estimation based approach to the problem of state estimation and the use of the dynamic regressor extension and mixing (DREM) technique to estimate these parameters. The use of DREM allows us to overcome the problem of lack of persistent excitation that stymies the application of standard parameter estimation designs. Simulation results illustrate the latter fact and show the improved performance of the proposed observer with respect to a locally stable gradient-descent-based observer.}, language = {en} } @misc{OrtegaBobtsovNikolaevetal., author = {Ortega, Romeo and Bobtsov, Alexey and Nikolaev, Nikolay and Schiffer, Johannes and Dochain, Denis}, title = {Generalized parameter estimation-based observers: Application to power systems and chemical-biological reactors}, series = {Automatica}, journal = {Automatica}, number = {129}, issn = {0005-1098}, doi = {10.1016/j.automatica.2021.109635}, abstract = {In this paper we propose a new state observer design technique for nonlinear systems. It consists of an extension of the recently introduced parameter estimation-based observer, which is applicable for systems verifying a particular algebraic constraint. In contrast to the previous observer, the new one avoids the need of implementing an open loop integration that may stymie its practical application. We give two versions of this observer, one that ensures asymptotic convergence and the second one that achieves convergence in finite time. In both cases, the required excitation conditions are strictly weaker than the classical persistent of excitation assumption. It is shown that the proposed technique is applicable to the practically important examples of multimachine power systems and chemical-biological reactors.}, language = {en} } @misc{RuedaEscobedoFridmanSchiffer, author = {Rueda-Escobedo, Juan G. and Fridman, Emilia and Schiffer, Johannes}, title = {Data-Driven Control for Linear Discrete-Time Delay Systems}, series = {IEEE Transactions on Automatic Control}, volume = {67}, journal = {IEEE Transactions on Automatic Control}, number = {7}, issn = {1558-2523}, doi = {10.1109/TAC.2021.3096896}, pages = {3321 -- 3336}, abstract = {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}, language = {en} } @misc{KrishnaSchiffer, author = {Krishna, Ajay and Schiffer, Johannes}, title = {A Port-Hamiltonian Approach to Modeling and Control of an Electro-Thermal Microgrid}, series = {IFAC-PapersOnLine}, volume = {54}, journal = {IFAC-PapersOnLine}, number = {19}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2021.11.092}, pages = {287 -- 293}, abstract = {We address the problems of modeling and controlling multi-energy microgrids (meMGs) composed of an electrical and a thermal system, which are connected via heat pumps (HPs). At first, we model the individual subsystems in a port-Hamiltonian (pH) framework. Then, by exploiting the structural properties of pH systems, we interconnect the subsystems in a passive manner and show that the overall meMG is shifted passive with respect to the control input-output mapping. We then use this property to propose a distributed passivity based-control (PBC) that addresses frequency and temperature regulation by utilizing the resources in the meMG in a proportional fashion and renders the closed-loop equilibrium asymptotically stable.}, language = {en} } @misc{RuedaEscobedoMorenoSchiffer, author = {Rueda-Escobedo, Juan G. and Moreno, Jaime A. and Schiffer, Johannes}, title = {L2-Gain Tuning for the Gradient Descent Algorithm in the Presence of Disturbances}, series = {2022 European Control Conference (ECC)}, journal = {2022 European Control Conference (ECC)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-3-9071-4407-7}, doi = {10.23919/ECC55457.2022.9838051}, pages = {1610 -- 1616}, abstract = {Due to its simplicity and inexpensive computation, the gradient descent algorithm is one of the most used tools in adaptive control and system identification. Although it has been studied for decades, little has been achieved in terms of tuning methods in the presence of disturbances. One of the main difficulties in its analysis is the time-varying nature of the algorithm. In this work, we contribute in such direction by providing LMI tools for tuning the gradient descent algorithm gain such that a guaranteed upper bound on the L2 -gain with respect to parameter variations and measurement noise is achieved. Two academic examples are provided to illustrate the efficient application of the method.}, language = {en} } @misc{JaramilloCajicaSchiffer, author = {Jaramillo-Cajica, Ismael and Schiffer, Johannes}, title = {A Dwell-Time Approach for Grid-Aware Operation of a Distributed Generator in an Islanded DC Microgrid}, series = {2022 European Control Conference (ECC)}, journal = {2022 European Control Conference (ECC)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-3-9071-4407-7}, doi = {10.23919/ECC55457.2022.9838354}, pages = {1079 -- 1084}, abstract = {We propose a switched control law for a DC-DC Buck converter that enables a grid-aware operation of a distributed generator (DG) in a low-voltage islanded DC microgrid (MG). The qualifier grid-aware means that the DG adjusts its operation mode in dependency of the MG status. The resulting closed-loop system is a switched system, in which the subsystems possess different equilibrium points. By means of a time- and state-dependent switching logic together with dwell-time stability analysis methods, we derive sufficient stability criteria that ensure the existence of a unique and globally exponentially stable equilibrium point of the resulting closed-loop switched system. The performance of the proposed control is illustrated via a numerical example.}, language = {en} } @misc{MendozaAvilaEfimovMercadoUribeetal., author = {Mendoza-Avila, Jesus and Efimov, Denis and Mercado-Uribe, Angel and Schiffer, Johannes}, title = {On Relaxed Conditions of Integral ISS for Multistable Periodic Systems}, series = {Proceedings of the 2021 61st IEEE Conference on Decision and Control (CDC)}, journal = {Proceedings of the 2021 61st IEEE Conference on Decision and Control (CDC)}, pages = {6}, abstract = {A novel characterization of the integral Inputto- State Stability (iISS) property is introduced for multistable systems whose dynamics are periodic with respect to a part of the state. First, the concepts of iISS-Leonov functions and output smooth dissipativity are introduced, then their equivalence to the properties of bounded-energy-bounded-state and global attractiveness of solutions in the absence of disturbances are proven. The proposed approach permits to relax the usual requirements of positive definiteness and periodicity of the iISSLyapunov functions. Moreover, the usefulness of the theoretical results is illustrated by a robustness analysis of a nonlinear pendulum with a constant bias input and an unbounded statedependent input coefficient.}, language = {en} } @misc{RuedaEscobedoMorenoSchiffer, author = {Rueda-Escobedo, Juan G. and Moreno, Jaime A. and Schiffer, Johannes}, title = {Design and Tuning of the Super-Twisting-Based Synchronous Reference Frame Phase-Locked-Loop}, series = {2022 IEEE 61st Conference on Decision and Control (CDC) ; December 6-9, 2022, Cancun, Mexico}, journal = {2022 IEEE 61st Conference on Decision and Control (CDC) ; December 6-9, 2022, Cancun, Mexico}, abstract = {The worldwide transition to climate-friendly energy systems entails the substitution of conventional energy generation based on synchronous generators by renewable energy sources based on power electronics. As a consequence, the overall inertia of the grid decreases, resulting in high volatility of the frequency and posing new challenges for the estimation of the latter quantity. To address this problematic, in the present paper a phase-locked-loop (PLL) based on the super-twisting algorithm is considered for the estimation of the phase angle and time-varying frequency of a symmetric three-phase signal. A rigorous proof of the algorithm's exact convergence in the presence of a fast-varying frequency together with tuning rules for its gains are derived by means of Lyapunov theory. Additionally, an estimate of the region of attraction is provided. The effectiveness of the proposed tuning method is illustrated in numerical simulations, while comparing its performance against a standard synchronous reference frame PLL.}, language = {en} } @misc{SyedMachadoSchiffer, author = {Syed, Wasif H. and Machado, Juan E. and Schiffer, Johannes}, title = {Distributed Adaptive Control for a DC Power Distribution System of a Series-Hybrid-Electric Propulsion System of a Commuter Aircraft}, series = {2024 American Control Conference (ACC)}, journal = {2024 American Control Conference (ACC)}, publisher = {IEEE}, doi = {10.23919/ACC60939.2024.10644618}, pages = {2598 -- 2603}, language = {en} } @misc{RuedaEscobedoMetzkowSchiffer, author = {Rueda-Escobedo, Juan G. and Metzkow, Ren{\´e} and Schiffer, Johannes}, title = {Robust current control of IPMSM drives under uncertain and varying inductances}, series = {Automatica}, volume = {152}, journal = {Automatica}, issn = {0005-1098}, doi = {10.1016/j.automatica.2023.110998}, abstract = {Interior permanent magnet synchronous machines (IPMSMs) are gaining popularity in e-mobility applications due to their wide constant power speed range when compared with other electric motors. The high-performance of IPMSMs is due to the pronounced degree of magnetic saliency, which originates from embedding their magnets inside the rotor. Yet, this feature complicates their control since it increases nonlinear phenomena such as cross-magnetization and saturation. This results in pronounced variations of the machine inductances, which are highly dependent on the machine current. This behaviour is of particular relevance in e-mobility applications, where a highly dynamic operation of the machine is required. In contrast to most existing current control approaches, where precise inductance knowledge is required, we address this challenge by deriving a controller that exploits the machine dynamics to achieve exponential current tracking in the presence of unknown and varying inductances. By interpreting the flux linkage as a modelled disturbance, we propose a dynamic compensator based on the internal model principle. As a by-product, the method provides an estimate of the flux linkage. The gain in performance compared to the standard PI controller is illustrated in simulation.}, language = {en} } @misc{SchifferEfimov, author = {Schiffer, Johannes and Efimov, Denis}, title = {Strong and Weak Leonov Functions for Global Boundedness of State Periodic Systems}, series = {IEEE Transactions on Automatic Control}, volume = {68}, journal = {IEEE Transactions on Automatic Control}, number = {12}, issn = {0018-9286}, doi = {10.1109/TAC.2023.3251903}, pages = {7958 -- 7965}, abstract = {We present new results for the analysis of global boundedness of state periodic systems. Thereby, we address both the case of systems, whose dynamics is periodic with respect to a part of the state vector, and the case of systems, whose dynamics is periodic with respect to all state variables. To derive the results, the notion of strong Leonov functions is introduced. The main results are complemented by a number of relaxations based on the concept of weak Leonov functions.}, language = {en} } @misc{MercadoUribeMendozaAvilaEfimovetal., author = {Mercado-Uribe, Angel and Mendoza-{\´A}vila, Jes{\´u}s and Efimov, Denis and Schiffer, Johannes}, title = {A Leonov Function for Almost Global Synchronization Conditions in Acyclic Networks of Heterogeneous Kuramoto Oscillators}, series = {IFAC-PapersOnLine}, volume = {56}, journal = {IFAC-PapersOnLine}, number = {2}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2023.10.248}, pages = {9505 -- 9510}, abstract = {Sufficient conditions for almost global synchronization in acyclic networks of Kuramoto oscillators with heterogeneous coupling strengths and natural frequencies are presented. The result is established by employing the recently developed Leonov function framework for systems whose dynamics are periodic for all state variables. The synchronization property is accompanied by necessary and sufficient conditions to guarantee the existence of equilibria. The implications of these conditions on the network topology, the oscillator's coupling strengths and natural frequencies are discussed. Finally, the results are illustrated via a numerical example.}, language = {en} } @misc{MendozaAvilaMercadoUribeEfimovetal., author = {Mendoza-Avila, Jesus and Mercado-Uribe, Angel and Efimov, Denis and Schiffer, Johannes}, title = {Design of controls for ISS and Integral ISS Stabilization of Multistable State Periodic Systems}, series = {IFAC-PapersOnLine}, volume = {56}, journal = {IFAC-PapersOnLine}, number = {2}, doi = {https://doi.org/10.1016/j.ifacol.2023.10.936}, pages = {4472 -- 4477}, language = {en} } @misc{WuerfelLorenzMeyerSchiffer, author = {W{\"u}rfel, Hans and Lorenz-Meyer, Nicolai and Schiffer, Johannes}, title = {Experimentally Validated Reduced-Order Models for Grid-Connected Inverters Using Balanced Residualization}, series = {2023 8th IEEE Workshop on the Electronic Grid (eGRID), Karlsruhe, Germany, 16-18 October 2023}, journal = {2023 8th IEEE Workshop on the Electronic Grid (eGRID), Karlsruhe, Germany, 16-18 October 2023}, address = {Karlsruhe}, isbn = {979-8-3503-2700-7}, doi = {10.1109/eGrid58358.2023.10380931}, pages = {6}, language = {en} } @misc{GernandtKrenzlinHagemannetal., author = {Gernandt, Hannes and Krenzlin, Franziska and Hagemann, Willem and Schiffer, Johannes}, title = {Data-based modeling for optimizing the operation of seasonal underground storages}, series = {Der Geothermiekongress 2023 : 17.-19. Oktober 2023 in Essen : Tagungsband}, journal = {Der Geothermiekongress 2023 : 17.-19. Oktober 2023 in Essen : Tagungsband}, address = {Essen}, organization = {Geothermische Vereinigung - Bundesverband Geothermie}, pages = {6}, abstract = {Underground thermal energy storages (UTES) are essential for decarbonizing the existing heating networks. To accurately simulate the storage and the connected heat supply system, typically detailed numerical models of the UTES and the heat supply system are required. In a co-simulation these models must be coupled, which is often time-consuming and has therefore not been used to operate systems in real-time. In this contribution, we present a method that leads to a data-based surrogate model of low complexity, which can then be directly integrated in the operational optimization. To illustrate the method, we derive a surrogate model from a Feflow model of a borehole thermal energy storage (BTES) as a particular type of UTES and integrate the surrogate model into a supply system that is optimized for electrical energy consumption using the Python toolbox Pyomo.}, language = {de} } @misc{ZuritaBustamanteRuedaEscobedoSchiffer, author = {Zurita-Bustamante, Erik W. and Rueda-Escobedo, Juan G. and Schiffer, Johannes}, title = {Passivity-Based Conditions for Asymptotic Stability of Speed Control for Three-Phase and Dual Three-Phase Permanent Magnet Synchronous Motors}, series = {62nd IEEE Conference on Decision and Control (CDC), 2023}, journal = {62nd IEEE Conference on Decision and Control (CDC), 2023}, isbn = {979-8-3503-0124-3}, issn = {2576-2370}, doi = {10.1109/CDC49753.2023.10383817}, pages = {6}, language = {en} } @misc{MendozaAvilaEfimovMercadoUribeetal., author = {Mendoza-Avila, Jesus and Efimov, Denis and Mercado-Uribe, Angel and Schiffer, Johannes}, title = {Design of Controls for Boundedness of Trajectories of Multistable State Periodic Systems}, series = {62nd IEEE Conference on Decision and Control (CDC), 2023}, journal = {62nd IEEE Conference on Decision and Control (CDC), 2023}, isbn = {979-8-3503-0124-3}, issn = {2576-2370}, doi = {10.1109/CDC49753.2023.10383528}, pages = {6}, language = {en} } @misc{MercadoUribeMendozaAvilaEfimovetal., author = {Mercado-Uribe, Angel and Mendoza-{\´A}vila, Jes{\´u}s and Efimov, Denis and Schiffer, Johannes}, title = {A Control Leonov Function Guaranteeing Global ISS of Two Coupled Synchronverters}, series = {62nd IEEE Conference on Decision and Control (CDC), 2023}, journal = {62nd IEEE Conference on Decision and Control (CDC), 2023}, isbn = {979-8-3503-0124-3}, issn = {2576-2370}, doi = {10.1109/CDC49753.2023.10383811}, pages = {6}, language = {en} } @misc{JaramilloCajicaMercadoUribeSchiffer, author = {Jaramillo-Cajica, Ismael and Mercado-Uribe, Angel and Schiffer, Johannes}, title = {Coordinated Control of Load Tap Changer Transformers for Voltage Regulation and Voltage Hunting Prevention: A Switched Systems Approach}, series = {62nd IEEE Conference on Decision and Control (CDC), 2023}, journal = {62nd IEEE Conference on Decision and Control (CDC), 2023}, isbn = {979-8-3503-0124-3}, issn = {2576-2370}, doi = {10.1109/CDC49753.2023.10383763}, pages = {6}, language = {en} } @misc{MathewRuedaEscobedoSchiffer, author = {Mathew, Riya and Rueda-Escobedo, Juan G. and Schiffer, Johannes}, title = {Robust Design of Phase-Locked Loops in Grid-Connected Power Converters}, series = {European Journal of Control}, journal = {European Journal of Control}, edition = {Volume 80}, doi = {10.1016/j.ejcon.2024.101055}, pages = {6}, language = {en} } @misc{LorenzMeyerWuerfelSchiffer, author = {Lorenz-Meyer, Nicolai and W{\"u}rfel, Hans and Schiffer, Johannes}, title = {Consensus + Innovations approach for online distributed multi-area inertia estimation}, series = {2024 IEEE PES Innovative Smart Grid Technologies Europe (ISGT EUROPE)}, journal = {2024 IEEE PES Innovative Smart Grid Technologies Europe (ISGT EUROPE)}, publisher = {IEEE}, address = {New York}, doi = {10.1109/ISGTEUROPE62998.2024.10863379}, pages = {1 -- 6}, abstract = {The reduction of overall system inertia in modern power systems due to the increasing deployment of distributed energy resources is generally recognized as a major issue for system stability. Consequently, real-time monitoring of system inertia is critical to ensure a reliable and cost-effective system operation. Large-scale power systems are typically managed by multiple transmission system operators, making it difficult to have a central entity with access to global measurement data, which is usually required for estimating the overall system inertia. We address this problem by proposing a fully distributed inertia estimation algorithm with rigorous analytical convergence guarantees. This method requires only peer-to-peer sharing of local parameter estimates between neighboring control areas, eliminating the need for a centralized collection of real-time measurements. We robustify the algorithm in the presence of typical power system disturbances and demonstrate its performance in simulations based on the well-known New England IEEE 39-bus system.}, language = {en} } @misc{MercadoUribeMendozaAvilaEfimovetal., author = {Mercado-Uribe, Angel and Mendoza-{\´A}vila, Jes{\´u}s and Efimov, Denis and Schiffer, Johannes}, title = {Sufficient conditions for global boundedness of solutions for two coupled synchronverters}, series = {2024 IEEE 63rd Conference on Decision and Control (CDC)}, journal = {2024 IEEE 63rd Conference on Decision and Control (CDC)}, publisher = {IEEE}, address = {New York}, doi = {10.1109/CDC56724.2024.10886006}, pages = {2785 -- 2790}, abstract = {This paper analyzes two synchronverters connected in parallel to a common capacitive-resistive load through resistive-inductive power lines. This system is conceptualized as a microgrid with two renewable energy sources controlled using the synchronverter algorithm. It is modeled as an interconnection of three port-Hamiltonian systems, and the dq-coordinates model is derived by averaging the frequencies. Applying the recent Leonov function theory, sufficient conditions to guarantee the global boundedness of the whole system's trajectories are provided. This is necessary to reach the global synchronization of microgrids. Additionally, a numerical example illustrates the potential resonance behavior of the microgrid.}, language = {en} } @book{ParisioSchifferHans, author = {Parisio, Alessandra and Schiffer, Johannes and Hans, Christian A.}, title = {System level control and optimisation of microgrids}, editor = {Parisio, Alessandra and Schiffer, Johannes and Hans, Christian A.}, publisher = {The Institution of Engineering and Technology}, address = {London}, isbn = {9781785618758}, doi = {10.1049/PBPO149E}, pages = {300}, abstract = {Microgrids are essential components of next-generation energy grids. A microgrid is a local, integrated energy system comprising interconnected loads and distributed energy resources; they can represent urban or rural districts, islands or local communities. Microgrids can operate in parallel with the main grid or independently in an intentional island mode. When on-site generation is included, intelligent buildings can also function as microgrids. Efficient optimization and control algorithms are crucial for ensuring optimal microgrid performance, making them a continuous focus of research and development in the field of power systems. The next-generation energy grid and urban environment need to be smart and sustainable to deal with the growing energy demand and achieve environmental goals. In this context, the role of local energy systems at the distribution level, which can represent urban or rural districts, islands or local communities, is crucial. System Level Control and Optimisation of Microgrids offers a comprehensive and systematic review of developments in this field. The chapters cover topics such as modelling of integrated energy systems and district heating systems, dynamics and control of grid-connected microgrids, frequency regulation, distributed optimization for energy grids, integration of distributed energy resources, transactive energy management for multi-energy microgrids, and laboratory validation. Real-world examples are provided through case studies based on the EUREF Energy Workshop and fog computing-based decentralized energy management. This book presents a wide range of perspectives from academia and industry on the challenges and solutions in microgrid optimization and control. It serves as a thorough resource for engineers and academics in the control and power systems fields, as well as for graduate students in related disciplines. Advanced control and optimization techniques for microgrids are discussed in depth, with examples and case studies demonstrating their practical application in shaping the future of energy systems.}, language = {en} } @misc{KrenzlinHagemannGernandtetal., author = {Krenzlin, Franziska and Hagemann, Willem and Gernandt, Hannes and Schiffer, Johannes}, title = {Data-driven modeling of borehole thermal energy storage (BTES) for operational optimization of renewable heat production systems}, series = {37th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2024)}, journal = {37th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2024)}, publisher = {ECOS 2024}, address = {Zografos, Greece}, doi = {10.52202/077185-0157}, pages = {1831 -- 1841}, abstract = {The utilization of underground thermal energy storage (UTES) systems, such as borehole thermal energy storage (BTES) systems plays a crucial role in the decarbonization of district heating. To ensure high performance and operation efficiency under the condition of a robust system operation, heat supply systems require advanced control and operation strategies including the operation of the thermal storage systems. The focus of our operational optimization lies on the heat production side, comprising a BTES and diverse heat sources, buffer storage systems and heat pumps. We utilize a nonlinear model of the heating network that explicitly integrates mass flows and temperatures instead of solely relying on heat flow considerations. The advantage of this more detailed consideration is that realistic constraints on temperatures and mass flows can be easily incorporated into the model. A major challenge in such realistic modeling is the correct representation of the temperature dynamics of thermal storage components, especially when the storage parameters are unknown and only limited input-output data are available. In this work, we propose a novel method leading to a reduced surrogate model of the BTES temperature dynamics that can be directly included in the optimization or control algorithms. The resulting data-based surrogate model captures the fundamental dynamics while being deployable to operational optimization and system control algorithms. In particular, we employ a Python-based operational optimization process of a theoretical system setup using Pyomo. In conclusion, the presented storage modeling approach is a first step towards a broad variety of system configurations including different UTES types.}, language = {en} } @misc{MercadoUribeMendozaAvilaEfimovetal., author = {Mercado-Uribe, Angel and Mendoza-Avila, Jesus and Efimov, Denis and Schiffer, Johannes}, title = {Conditions for global synchronization in networks of heterogeneous Kuramoto oscillators}, series = {Automatica}, volume = {175}, journal = {Automatica}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0005-1098}, doi = {10.1016/j.automatica.2025.112180}, pages = {1 -- 11}, abstract = {The Kuramoto model is essential for studying synchronization. In this work, we present sufficient conditions for global synchronization in networks of heterogeneous Kuramoto oscillators in the absence of homoclinic and heteroclinic cycles. The result is established by constructing a suitable Leonov function candidate for the Kuramoto model, which provides sufficient conditions for almost global synchronization in networks with acyclic and meshed topologies. The synchronization property is accompanied by necessary and sufficient conditions to guarantee the existence of equilibria, which are satisfied if the conditions for synchronization hold. The implications of the main conditions and their relationship with the network topology and parameters are discussed. Finally, the results are illustrated via a numerical example.}, language = {en} } @incollection{SchifferSimpsonPorcoParisio, author = {Schiffer, Johannes and Simpson-Porco, John W. and Parisio, Alessandra}, title = {Control in Low-Inertia Power and Integrated Energy Systems}, series = {Reference Module in Materials Science and Materials Engineering}, booktitle = {Reference Module in Materials Science and Materials Engineering}, publisher = {Elsevier}, isbn = {9780128035818}, doi = {10.1016/B978-0-443-14081-5.00068-4}, pages = {20}, abstract = {Driven by global efforts to mitigate the climate crisis, power systems are undergoing unprecedented changes. An important factor in this energy transition is the replacement of large-scale conventional fossil fuel-driven synchronous generators by renewable-driven inverter-based generation. This substitution entails a large reduction of the overall power system inertia, leading to faster and more volatile dynamics. Such power systems are therefore termed low-inertia power systems. In the present chapter, key properties and aspects for modeling, control and operation of this kind of future power systems are introduced, with a focus on automatic frequency control, dynamic state estimation and grid-synchronization of inverter-based resources. As moving beyond decarbonization of only the electricity sector is viewed as essential for the successful development of climate-neutral societies, the exposition is complemented by identifying current trends in integrated energy systems. These novel energy system architectures are characterized by integration of diverse energy vectors, such as electricity, heat, transportation, and (hydrogen) gas, in a holistic manner. Overall, the chapter places a control-theoretic lens on these societal-scale sustainability challenges.}, language = {en} } @misc{JaramilloCajicaSchiffer, author = {Jaramillo-Cajica, Ismael and Schiffer, Johannes}, title = {A dwell-time approach for decentralized grid-aware operation of islanded DC microgrids}, series = {Automatica}, volume = {160}, journal = {Automatica}, publisher = {Elsevier BV}, issn = {0005-1098}, doi = {10.1016/j.automatica.2023.111461}, pages = {1 -- 11}, abstract = {In islanded microgrid (MG) applications, renewable-based distributed generation units (DGUs) are commonly operated in grid-feeding mode, while storage-based DGUs assume the grid-forming responsibilities. This results in limited controllable power reserves, which may pose severe threats to the overall system stability. Motivated by this, we consider the problem of designing a more flexible grid-aware control scheme for enlarging the actuation power of a DC MG. That is, existing DGUs are able to adopt different operation modes by switching among two decentralized passivity-based subsystem control laws in dependency of their node status. To this purpose, we design a time- and state-dependent switching logic that coordinates the DGU mode transitions and ensures that the closed-loop interconnected MG possesses a unique equilibrium point. Then, we derive sufficient tuning conditions on the control parameters that ensure global exponential stability of this equilibrium by adopting a multiple Lyapunov functions approach that exploits the passive interconnection properties of the MG together with dwell-time methods for switched systems. The advantageous performance of the proposed strategy is illustrated via a numerical example.}, language = {en} } @misc{ReimannRoseKuepperetal., author = {Reimann, Ansgar and Rose, Max and K{\"u}pper, Jan and Schiffer, Johannes}, title = {Nonlinear system identification and predictive control for waste heat recovery with heat pumps}, series = {IFAC-PapersOnLine}, volume = {58}, journal = {IFAC-PapersOnLine}, number = {2}, publisher = {Elsevier BV}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2024.07.103}, pages = {130 -- 135}, abstract = {The utilization of low-temperature waste heat, particularly from electrolyzers, in district heating networks via heat pumps presents a promising approach to accelerate the decarbonization of the heat sector. However, managing the electrolyzer's specific temperature requirements and dynamic waste heat output, while simultaneously meeting the district heating network's variable temperature demands, requires the implementation of an advanced control system for the heat pump cycle. For this, model predictive control is a promising approach since it not only ensures the satisfaction of constraints, but also facilitates a direct optimization of the heat pump's operational efficiency. Nevertheless, model predictive control requires a dynamic heat pump model. In this context, first-principles models are often used. However, they are very complex and difficult to parameterize for real heat pumps. Therefore, in the present paper, a data-based system identification is carried out to obtain a reduced-order heat pump model from a high-fidelity first-principles simulation model. Based on the identified model, a predictive controller is implemented. The effectiveness of the obtained controller for operating the first-principles model is demonstrated in a numerical case study.}, language = {en} } @misc{HerrmannPlietzschRoseetal., author = {Herrmann, Ulrike and Plietzsch, Anton and Rose, Max and Gernandt, Hannes and Schiffer, Johannes}, title = {A predictive operation management scheme for hydrogen networks based on the method of characteristics}, series = {2024 European Control Conference (ECC)}, journal = {2024 European Control Conference (ECC)}, publisher = {IEEE}, doi = {10.23919/ECC64448.2024.10591107}, pages = {1084 -- 1089}, abstract = {As future hydrogen networks will be strongly linked to the electricity system via electrolysers and hydrogen power plants, challenges will arise for their operation. A suitable response to phenomena, such as rapidly changing boundary conditions and unbalanced supply and demand, requires the implementation of operational concepts based on transient pipe models. The transient pipe flow can be described by the isothermal Euler equations, which we discretize using an explicit Method Of Characteristics. Based on this, we develop a nonlinear space-time discretized network model that incorporates various other components, including hydrogen storage facilities, active elements such as valves and compressor stations, as well as electrolyzers and fuel cells. This network model serves as the foundation for the development of a tailored economic model predictive control algorithm designed for fast timescales. The algorithm enables controlled pressure changes within specified bounds in response to changes in supply and demand while simultaneously minimizing fast pressure fluctuations in the pipelines. Through a detailed case study, we demonstrate the algorithm's proficiency in addressing these transient operation challenges.}, language = {en} } @misc{TexisLoaizaZuritaBustamanteSchiffer, author = {Texis-Loaiza, Oscar and Zurita-Bustamante, Eric W. and Schiffer, Johannes}, title = {A BL-homogeneous observer for inter-turn short-circuit fault detection in PMSMs}, series = {2024 IEEE Conference on Control Technology and Applications (CCTA)}, journal = {2024 IEEE Conference on Control Technology and Applications (CCTA)}, publisher = {IEEE}, doi = {10.1109/CCTA60707.2024.10666505}, pages = {248 -- 253}, abstract = {Electric vehicle propulsion systems heavily depend on the reliable operation of permanent magnet synchronous motors (PMSMs). However, the susceptibility of PMSMs to electrical faults, particularly inter-turn short circuit (ITSC) faults, poses a significant threat to their overall reliability. With the purpose of enabling an immanent fault detection, we design a fault detection observer using the recently developed bi-limit-homogeneous sliding mode observer (BL-H SMO) technique. The BL-H SMO has the ability to offer zero error estimates within finite or fixed-time intervals even in the presence of unknown inputs, which is a distinctive advantage enhancing its efficacy in fault detection for PMSMs compared to standard Kalman filter schemes. These advantages are illustrated via a simulation study that validates and compares the proposed BL-H SMO's performance with that of a Kalman filter.}, language = {en} } @misc{LorenzMeyerSuchantkeSchiffer, author = {Lorenz-Meyer, Nicolai and Suchantke, Ren{\´e} and Schiffer, Johannes}, title = {Dynamic state and parameter estimation in multi-machine power systems—Experimental demonstration using real-world PMU-measurements}, series = {Control Engineering Practice}, volume = {135}, journal = {Control Engineering Practice}, issn = {0967-0661}, doi = {10.1016/j.conengprac.2023.105491}, abstract = {Dynamic state and parameter estimation (DSE) plays a key role for reliably monitoring and operating future, power-electronics-dominated power systems. While DSE is a very active research field, experimental applications of proposed algorithms to real-world systems remain scarce. This motivates the present paper, in which we demonstrate the effectiveness of a DSE algorithm previously presented by parts of the authors with real-world data collected by a Phasor Measurement Unit (PMU) at a substation close to a power plant within the extra-high voltage grid of Germany. To this end, at first we derive a suitable mapping of the real-world PMU-measurements recorded at a substation close to the power plant to the terminal bus of the power plants' synchronous generator. This mapping considers the high-voltage transmission line, the tap-changing transformer and the auxiliary system of the power plant. Next, we introduce several practically motivated extensions to the estimation algorithm, which significantly improve its practical performance with real-world measurements. Finally, we successfully validate the algorithm experimentally in an auto- as well as a cross-validation.}, language = {en} } @misc{RoseHansSchiffer, author = {Rose, Max and Hans, Christian A. and Schiffer, Johannes}, title = {A Predictive Operation Controller for an Electro-Thermal Microgrid Utilizing Variable Flow Temperatures}, series = {IFAC-PapersOnLine}, volume = {56}, journal = {IFAC-PapersOnLine}, number = {2}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2023.10.195}, pages = {5444 -- 5450}, abstract = {We propose an optimal operation controller for an electro-thermal microgrid. Compared to existing work, our approach increases flexibility by operating the thermal network with variable flow temperatures and in that way explicitly exploits its inherent storage capacities. To this end, the microgrid is represented by a multi-layer network composed of an electrical and a thermal layer. We show that the system behavior can be represented by a discrete-time state model derived from DC power flow approximations and 1d Euler equations. Both layers are interconnected via heat pumps. By combining this model with desired operating objectives and constraints, we obtain a constrained convex optimization problem. This is used to derive a model predictive control scheme for the optimal operation of electro-thermal microgrids. The performance of the proposed operation control algorithm is demonstrated in a case study.}, language = {en} } @misc{Mendoza‐AvilaEfimovAngelMercado‐Uribeetal., author = {Mendoza-Avila, Jesus and Efimov, Denis and Angel Mercado-Uribe, Jose and Schiffer, Johannes}, title = {Design of control laws for robust global stabilization of multistable state periodic systems}, series = {International journal of robust and nonlinear control}, journal = {International journal of robust and nonlinear control}, publisher = {Wiley}, address = {New York, NY}, issn = {1049-8923}, doi = {10.1002/rnc.70206}, pages = {1 -- 20}, abstract = {This paper continues with the development of the input-to-state stability (ISS)-control Leonov function (CLeF) approach. The definitions of practical ISS and integral ISS (iISS)-CLeFs are refined, and the proposed methodology for control synthesis is improved to simplify the final control law. Then, it is shown that the existence of practical ISS- and iISS-CLeFs is a sufficient condition to guarantee the existence of a controller that endows multistable state periodic systems with the ISS and iISS properties, respectively. Furthermore, a methodology for the design of such a controller is provided via the well-known Sontag's universal formula. Besides, an extension of the main result is presented to connect the ISS-CLeF approach with the standard Leonov function method such that the maximal invariant set of the closed-loop system is compact on a manifold. Finally, the proposed approach is applied to the design of an excitation controller for a synchronous generator, which guarantees global ISS properties for the closed-loop system, unlike the usual local results reported in the literature. The obtained control is also independent of the load angle. The effectiveness of the designed controller is demonstrated in simulations.}, language = {en} } @misc{ŞenMachadoSchiffer, author = {Şen, G{\"o}k{\c{c}}en Devlet and Machado, Juan E. and Schiffer, Johannes}, title = {A cost-optimal predictive operation scheme for sector-coupled energy plants with start-up delays and start-up costs}, series = {IFAC-PapersOnLine}, volume = {59}, journal = {IFAC-PapersOnLine}, number = {9}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {2405-8963}, doi = {10.1016/j.ifacol.2025.08.143}, pages = {241 -- 246}, abstract = {In this work we present a cost-optimal energy management scheme for sector-coupled energy plants, focusing on systems that enable gas-to-electricity, gas-to-heat, and power-to-heat conversions. To capture realistic operational challenges, the considered system model incorporates dynamic constraints, including start-up delays and off-time-dependent start-up costs. By accounting for the impact of these factors, we demonstrate on a case study that they can significantly reduce overall operational costs. The energy management problem is cast as a mixed-integer nonlinear programming (MINLP) problem, which is then solved within a model predictive control (MPC) framework. The proposed approach provides a structured methodology for real-time energy management, enhancing energy efficiency while minimizing costs.}, language = {en} } @misc{RoseGernandtFaulwasseretal., author = {Rose, Max and Gernandt, Hannes and Faulwasser, Timm and Schiffer, Johannes}, title = {Exact time-varying turnpikes for dynamic operation of district heating networks}, series = {IEEE control systems letters}, volume = {9}, journal = {IEEE control systems letters}, publisher = {IEEE}, address = {New York, NY}, issn = {2475-1456}, doi = {10.1109/LCSYS.2025.3582614}, pages = {1706 -- 1711}, abstract = {District heating networks (DHNs) are crucial for decarbonizing the heating sector. Yet, their efficient and reliable operation requires the coordination of multiple heat producers and the consideration of future demands. Predictive and optimization-based control is commonly used to address this task, but existing results for DHNs do not account for time-varying problem aspects. Since the turnpike phenomenon can serve as a basis for model predictive control design and analysis, this letter examines its role in DHN optimization by analyzing the underlying optimal control problem with time-varying prices and demands. That is, we derive conditions for the existence of a unique time-varying singular arc, which constitutes the time varying turnpike, and we provide its closed-form expression. Additionally, we present converse turnpike results showing a exact time-varying case implies strict dissipativity of the optimal control problem. A numerical example illustrates our findings.}, language = {en} } @misc{BuettnerWuerfelLiemannetal., author = {B{\"u}ttner, Anna and W{\"u}rfel, Hans and Liemann, Sebastian and Schiffer, Johannes and Hellman, Frank}, title = {Complex-phase, data-driven identification of grid-forming inverter dynamics}, series = {IEEE transactions on smart grid}, volume = {9}, journal = {IEEE transactions on smart grid}, number = {6}, publisher = {IEEE}, address = {New York, NY}, issn = {1949-3053}, doi = {10.1109/TSG.2025.3591891}, pages = {4854 -- 4864}, abstract = {The increasing integration of renewable energy sources (RESs) into power systems requires the deployment of grid-forming inverters to ensure a stable operation. Accurate modeling of these devices is necessary. In this paper, a system identification approach to obtain low-dimensional models of gridforming inverters is presented. The proposed approach is based on a Hammerstein-Wiener parametrization of the normal-form model. The normal-form is a gray-box model that utilizes complex frequency and phase to capture non-linear inverter dynamics. The model is validated on two well-known control strategies: droop-control and dispatchable virtual oscillators. Simulations and hardware-in-the-loop experiments demonstrate that the normalform accurately models inverter dynamics across various operating conditions. The approach shows great potential for enhancing the modeling of RES-dominated power systems, especially when component models are unavailable or computationally expensive.}, language = {en} } @misc{LorenzMeyerRuedaEscobedoMorenoetal., author = {Lorenz-Meyer, Nicolai and Rueda-Escobedo, Juan G. and Moreno, Jaime A. and Schiffer, Johannes}, title = {A robust consensus + innovations-based distributed parameter estimator}, series = {IEEE transactions on automatic control}, journal = {IEEE transactions on automatic control}, publisher = {IEEE}, address = {New York, NY}, issn = {0018-9286}, doi = {10.1109/TAC.2025.3597563}, pages = {1 -- 15}, abstract = {While distributed parameter estimation has been extensively studied in the literature, little has been achieved in terms of robust analysis and tuning methods in the presence of disturbances. However, disturbances such as measurement noise and model mismatches occur in any real-world setting. Therefore, providing tuning methods with specific robustness guarantees would greatly benefit the practical application. To address these issues, we recast the error dynamics of a continuous-time version of the widely used consensus + innovations-based distributed parameter estimator to reflect the error dynamics induced by the classical gradient descent algorithm. This paves the way for the construction of a strong Lyapunov function. Based on this result, we derive linear matrix inequality-based tools for tuning the algorithm gains such that a guaranteed upper bound on the L2-gain with respect to parameter variations, measurement noise, and disturbances in the communication channels is achieved. An application example illustrates the efficiency of the method.}, language = {en} } @misc{EstradaRuedaEscobedoMorenoetal., author = {Estrada, Manuel A. and Rueda-Escobedo, Juan G. and Moreno, Jaime A. and Schiffer, Johannes}, title = {Systematic and robust tuning of proportional-resonant controllers for current and voltage tracking}, series = {2025 IEEE Conference on Control Technology and Applications (CCTA), August 25-27, 2025, San Diego, CA, USA}, journal = {2025 IEEE Conference on Control Technology and Applications (CCTA), August 25-27, 2025, San Diego, CA, USA}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {979-8-3315-3908-5}, issn = {0018-9286}, doi = {10.1109/CCTA53793.2025.11151423}, pages = {768 -- 773}, abstract = {In the control and operation of power inverters, proportional-resonant (PR) controllers are used to track references and reject disturbances that can be described by a sum of sinusoidal signals of known frequency. The relevance of these controllers is increasing due to the increase in distortion and volatility of three-phase signals in the grid. However, as reported in the literature, the tuning of PR controllers is far from trivial due to their large number of parameters and the presence of pure imaginary poles in the associated transfer function. To address these issues, a time-domain framework based on linear matrix inequalities (LMIs) is presented for the tuning of PR controllers with applications to voltage and current tracking. The advantage of this approach is the straightforward combination with other techniques such as H∞ control. The effectiveness of the approach is illustrated through numerical simulations, where the injection of a constant active power is achieved in the presence of distorted voltages.}, language = {en} } @misc{OrtegaBobtsovFangetal., author = {Ortega, Romeo and Bobtsov, Alexey and Fang, Leyan and Texis-Loaiza, Oscar and Schiffer, Johannes}, title = {Interturn fault detection in PMSMs : two adaptive observer-based noise insensitive solutions}, series = {IEEE transactions on control systems technology}, journal = {IEEE transactions on control systems technology}, publisher = {IEEE}, address = {New York, NY}, issn = {1063-6536}, doi = {10.1109/TCST.2025.3612450}, pages = {1 -- 12}, abstract = {In this article, we address the problem of online detection of interturn short-circuit faults (ITSCFs) that occur in interior- and surface-mounted permanent magnet synchronous motors (PMSMs). We propose two solutions to this problem: 1)a very simple linear observer and 2) a generalized parameter estimation-based observer, that incorporates a high performance estimator—with both observers detecting the short-circuit current and the fault intensity. Although the first solution guarantees the detection of the fault exponentially fast, the rate of convergence is fully determined by the motor parameters that, in some cases, may be too slow. The second observer, on the other hand, ensures finite convergence time (FCT) under the weakest assumption of interval excitation (IE). To make the observers adaptive, we develop a parameter estimator that, in the case of surface-mounted motors, estimates online (exponentially fast) the resistance and inductance of the motor. It should be underscored that, in contrast with existing observers (including the widely popular Kalman filter) that provide indirect information of the fault current, our observers provide an explicit one—namely the amplitude of the fault current. An additional advantage of the observers is that they do not require the knowledge of the motor currents, making them insensitive to current measurement noise. The performance of both observers, in their linear and generalized parameter estimation-based versions, is illustrated with realistic simulation studies.}, language = {en} } @misc{HagemannWeichmannGernandtetal., author = {Hagemann, Willem and Weichmann, Jaßper and Gernandt, Hannes and Krenzlin, Franziska and Schiffer, Johannes}, title = {Modeling and optimization of borehole thermal energy storage systems using physics-based neural networks}, series = {Renewable energy : an international journal}, volume = {256, Part A}, journal = {Renewable energy : an international journal}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0960-1481}, doi = {10.1016/j.renene.2025.123753}, pages = {1 -- 14}, abstract = {Borehole thermal energy storage (BTES) systems are critical components in the decarbonization of district heating networks as they enhance operational flexibility by seasonally storing thermal energy. While various modeling approaches for BTES exist, they are typically unsuitable for optimization problems and model-based control design. In this work, we propose a novel modeling approach that leads to a physics-based neural network surrogate model of the BTES temperature dynamics, capturing the fundamental dynamics with sufficient accuracy, while maintaining a relatively low complexity that makes it suitable for deployment in operational optimization or control algorithms. Specifically, we examine a standard BTES system that combines multiple heat sources, heat pumps, and storage buffers, detailing the associated mass flows and temperatures. We utilize a Python-based operational optimization process for the theoretical system setup using Pyomo and demonstrate that our modeling approach enables accurate optimizations over planning horizons of up to one year with a sample time of one hour. The new modeling approach significantly improves prediction accuracy across the relevant system states, with mean absolute errors reduced by approximately one-third compared to a single-capacitance model identified with the sparse identification framework SINDy.}, language = {en} } @misc{ArchilaWouwerSchiffer, author = {Archila, Oscar F. and Wouwer, Alain Vande and Schiffer, Johannes}, title = {A multiple artificial potential functions approach for collision avoidance in UAV systems}, series = {IEEE transactions on intelligent transportation systems}, volume = {26}, journal = {IEEE transactions on intelligent transportation systems}, number = {10}, publisher = {IEEE}, address = {New York, NY}, issn = {1524-9050}, doi = {10.1109/TITS.2025.3579157}, pages = {16688 -- 16699}, abstract = {Collision avoidance is a problem largely studied in robotics, particularly in uncrewed aerial vehicle (UAV) applications. The main challenges in this area are hardware limitations, the need for rapid response, and the uncertainty associated with obstacle detection. Artificial potential functions (APOFs) are a prominent method to address these challenges. However, existing solutions lack assurances regarding closed-loop stability and may result in chattering effects. Hence, we propose a high-level control method for static obstacle avoidance based on multiple artificial potential functions (MAPOFs), with a set of switching rules with conditions on the parameter tuning ensuring the stability of the final position. The stability proof is established by analyzing the closed-loop system using tools from hybrid systems theory. Furthermore, we validate the performance of the MAPOF control through simulations and real-life experiments, showcasing its effectiveness in avoiding static obstacles.}, language = {en} } @misc{TexisLoaizaMercadoUribeMorenoetal., author = {Texis-Loaiza, Oscar and Mercado-Uribe, Angel and Moreno, Jaime A. and Schiffer, Johannes}, title = {A finite-time convergent primal-dual gradient dynamics based on the multivariable super-twisting algorithm}, series = {2025 European Control Conference (ECC)}, journal = {2025 European Control Conference (ECC)}, publisher = {IEEE}, address = {New York, NY}, isbn = {978-3-907144-12-1}, doi = {10.23919/ECC65951.2025.11186834}, pages = {1892 -- 1898}, abstract = {We propose a novel primal-dual gradient dynamics (PDGD) algorithm to dynamically solve an optimization problem with linear equality constraints in finite time. To ensure finite-time convergence, we endow the PDGD with suitable homogeneity properties. More precisely, departing from the standard PDGD and based on the associated Lagrangian of the optimization problem, the algorithm is derived by suitably combining a change of coordinates of the standard PDGD with the multivariable super-twisting algorithm. In our new coordinates, the proposed PDGD's global convergence to the optimal solution of the optimization problem is then proven via a smooth, strong Lyapunov function. Additionally, we provide a numerical example to compare the performance of our algorithm with existing approaches from the literature.}, language = {en} } @misc{TexisLoaizaMorenoMercadoUribeetal., author = {Texis-Loaiza, Oscar and Moreno, Jaime A. and Mercado-Uribe, Angel and Schiffer, Johannes}, title = {A third-order bl-homogeneous sliding mode observer for uncertain triangular nonlinear systems}, series = {2025 European Control Conference (ECC)}, journal = {2025 European Control Conference (ECC)}, publisher = {IEEE}, address = {New York, NY}, isbn = {978-3-907144-12-1}, doi = {10.23919/ECC65951.2025.11186860}, pages = {1955 -- 1960}, abstract = {In this paper, we propose a global third-order homogeneous in the bi-limit sliding mode observer (BL-H SMO) that can estimate the states of an uncertain nonlinear system with unknown inputs in finite time. The system must be strongly observable w.r.t. unknown inputs (UIs) and uniformly observable w.r.t. known inputs. To handle the UIs and non-Lipschitz nonlinearities, the proposed observer combines sliding-mode and high-gain observers, extending the generalized super-twisting observer. The convergence of the BL-H SMO to the system states is proven through a Lyapunov function. Finally, to showcase the effectiveness of the proposed method, the paper includes an academic example and a practical example, namely a three-phase converter with LCL-filter.}, language = {en} } @misc{CortesMartinezSuryawanshiRuffertetal., author = {Cort{\´e}s Mart{\´i}nez, Rolando and Suryawanshi, Abhijeet Sanjay and Ruffert, Christine and Herglotz, Christian and Schiffer, Johannes}, title = {Towards a modular 5G motion capture testbed for indoor UAVs}, series = {MikroSystemTechnik Kongress 2025 : Mikroelektronik, Mikrosystemtechnik und ihre Anwendungen - Nachhaltigkeit und Technologiesouver{\"a}nit{\"a}t : proceedings : 27.-29. Oktober 2025, Duisburg}, journal = {MikroSystemTechnik Kongress 2025 : Mikroelektronik, Mikrosystemtechnik und ihre Anwendungen - Nachhaltigkeit und Technologiesouver{\"a}nit{\"a}t : proceedings : 27.-29. Oktober 2025, Duisburg}, publisher = {VDE VERLAG GmbH}, address = {Berlin}, isbn = {978-3-8007-6614-7}, pages = {373ff.}, language = {en} }