Browsing by Author "Cañizares, Claudio"

Now showing 1 - 4 of 4

Frequency and voltage coordinated control of a grid of AC/DC microgrids
(Elsevier BV, 2022-01-17) Alghamdi, Baheej; Cañizares, Claudio
This paper proposes a hierarchical control scheme based on a distributed controller design for a multi-microgrid system. Thus, a proposed control approach of ac and dc microgrid interfaces is presented, based on virtual synchronous generators to control the power exchange of the interconnected microgrids, and provide frequency support, voltage regulation, and virtual inertia for the individual microgrids and ac host grid. A hierarchical distributed control technique is proposed, with primary controls of interfacing virtual synchronous generators providing adaptive inertia for all ac systems, while a secondary distributed control regulates the frequency and the voltages of the ac host grid and the interconnected ac and dc microgrids, based on a consensus technique with limited information about the overall system. The proposed controller shares the total system load among the grid and microgrids, while minimizing the overall frequency and dc-voltage deviations in all interconnected systems. The presented interface and the controller are implemented, tested, and validated using time-domain simulations for a multi-microgrid test system, which is based on a CIGRE benchmark medium voltage system and consists of both ac and dc microgrids.
Geographic-information-based stochastic optimization model for multi-microgrid planning
(Elsevier, 2023-04-01) Vera, Enrique Gabriel; Cañizares, Claudio; Pirnia, Mehrdad
This paper presents a model for the realistic planning of multi-microgrids in the context of Active Distribution Networks with the assistance of Geographic Information Systems. The model considers the distribution system grid as well as the geographic features of the Region of Interest. It also includes long-term purchase decisions and short-term operational constraints, and considers uncertainties associated with electricity demand and Renewable Energy Resources using an existing Two-Stage Stochastic Programming approach. Geographic Information Systems along with Deep Learning are used to estimate the areas of rooftops within the Region of Interest and model the Low Voltage grid. The planning model is used to study the feasibility of implementing a multi-microgrid system consisting of 4 individual microgrids at an Active Distribution Network in a municipality in the state of São Paulo, Brazil. The results of the model presented in this paper are compared with the results obtained using Monte Carlo Simulations and an existing, less detailed, Two Stage Stochastic model. It is demonstrated that the stochastic solutions are close to those obtained with Monte Carlo at a lower computational cost, and that the use of Geographic Information allows to determine both the capacity and location of the PV panels, batteries, and distribution transformers on the microgrids grid, thus providing more precise and useful planning results.
Operation of Microgrids with Conventional and Virtual Energy Storage Systems
(University of Waterloo, 2022-11-30) Cordova, Samuel; Cañizares, Claudio; Lorca, Álvaro
Distribution systems are now increasingly becoming more active due to the sustainable integration of Distributed Energy Resources (DER). While this has enabled a cleaner and more efficient generation, it has also resulted in new challenges for the operation of modern power systems. In this context, the operation of isolated microgrids is particularly challenging, as these systems are characterized by a low inertia and significant renewable integration, and must be capable of an autonomous operation without the support of other electrical grids. Thus, the present thesis focuses on the design of an Energy Management System (EMS) for the reliable and economic operation of modern isolated microgrids. Isolated microgrid operation requires considering additional aspects typically omitted in the operation of robust bulk power systems. In particular, as demonstrated in this thesis, second-to-second renewable power fluctuations need to be considered in the microgrid EMS, since these fluctuations can have a large impact on the system’s frequency regulation due to its low inertia. Furthermore, to ensure an economic yet reliable operation, modern flexible technologies capable of counterbalancing these short-term fluctuations, such as Battery Energy Storage Systems (BESS) and Demand Response (DR), need to be integrated in the microgrid EMS. Hence, the present thesis focuses on designing a microgrid EMS model that integrates short-term renewable power fluctuations, their impact on frequency regulation, and the role that BESS and DR can play for their management. In the first part of the thesis, models are presented to characterize short-term renewable power fluctuations and their impact on microgrid operations, including the role that BESS can play to manage power fluctuations and the battery degradation resulting from providing this service. These models are then used to develop a practical EMS considering short-term renewable fluctuations and BESS flexibility, which is validated through exhaustive simulations on two realistic test microgrids, showing the operational benefits of the proposed EMS and highlighting the need to properly model short-term fluctuations and battery degradation in EMS for isolated microgrids. In the second part of the thesis, the above EMS model is extended to also incorporate the impact of short-term power fluctuations on the microgrid’s frequency regulation performance. For this purpose, accurate linear equations describing the frequency deviation and Rate-of-Change-of-Frequency (RoCoF) resulting from these fluctuations are developed, which are then used to build a frequency-constrained EMS model capable of guaranteeing an adequate frequency regulation performance in line with current DER operating standards. Exhaustive transient simulations on a realistic test microgrid considering detailed frequency dynamic and control models are presented, demonstrating the accuracy of the proposed frequency-constrained EMS and the operational benefits resulting from its implementation. Finally, the integration of DR techniques for an enhanced microgrid operation is discussed. In particular, the smart control of Thermostatically Controlled Loads (TCL) is studied, as these type of loads comprise a significant share of the total residential demand, and have the capability of managing second-to-second power imbalances without significantly affecting customer comfort. Since computational limitations prevent the direct integration of TCLs within operational models, alternative computationally efficient aggregate models representing TCL flexibility and frequency dynamics are proposed, which are referred to as Virtual Energy Storage Systems (VESS) due to their close resemblance to Conventional Energy Storage Systems (CESS) such as batteries. The proposed aggregate VESS models are then used to design a practical EMS integrating TCL flexibility, and study the impact of TCL integration on microgrid operation and frequency control. Computational experiments using detailed frequency transient and thermal dynamic models are presented, demonstrating the accuracy of the proposed aggregate VESS models, as well as the economic and reliability benefits resulting from using these aggregate models to integrate TCLs in microgrid operation.
Toward transactive control of coupled electric power and district heating networks
(Elsevier, 2022-12-19) Maurer, Jona; Tschuch, Nicolai; Krebs, Stefan; Bhattacharya, Kankar; Cañizares, Claudio; Hohmann, Sören
Although electric power networks and district heating networks are physically coupled, they are not operated in a coordinated manner. With increasing penetration of renewable energy sources, a coordinated market-based operation of the two networks can yield significant advantages, as reduced need for grid reinforcements, by optimizing the power flows in the coupled systems. Transactive control has been developed as a promising approach based on market and control mechanisms to coordinate supply and demand in energy systems, which when applied to power systems is being referred to as transactive energy. However, this approach has not been fully investigated in the context of market-based operation of coupled electric power and district heating networks. Therefore, this paper proposes a transactive control approach to coordinate flexible producers and consumers while taking into account the operational aspects of both networks, for the benefit of all participants and considering their privacy. A nonlinear model predictive control approach is applied in this work to maximize the social welfare of both networks, taking into account system operational limits, while reducing losses and considering system dynamics and forecasted power supply and demand of inflexible producers and consumers. A subtle approximation of the operational optimization problem is used to enable the practical application of the proposed approach in real time. The presented technique is implemented, tested, and demonstrated in a realistic test system, illustrating its benefits.