Browsing by Author "Olivares, Daniel E."

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A Centralized Energy Management System for Isolated Microgrids
(Institute of Electrical and Electronics Engineers (IEEE), 2014-04-25) Olivares, Daniel E.; Canizares, Claudio A.; Kazerani, Mehrdad
This paper presents the mathematical formulation of the microgrid's energy management problem and its implementation in a centralized Energy Management System (EMS) for isolated microgrids. Using the model predictive control technique, the optimal operation of the microgrid is determined using an extended horizon of evaluation and recourse, which allows a proper dispatch of the energy storage units. The energy management problem is decomposed into Unit Commitment (UC) and Optimal Power Flow (OPF) problems in order to avoid a mixed-integer non-linear formulation. The microgrid is modeled as a three-phase unbalanced system with presence of both dispatchable and non-dispatchable distributed generation. The proposed EMS is tested in an isolated microgrid based on a CIGRE medium-voltage benchmark system. Results justify the need for detailed three-phase models of the microgrid in order to properly account for voltage limits and procure reactive power support.
Aggregate Modeling of Thermostatically Controlled Loads for Microgrid Energy Management Systems
(Institute of Electrical and Electronics Engineers (IEEE), 2023-03-09) Córdova, Samuel; Cañizares, Claudio A.; Lorca, Álvaro; Olivares, Daniel E.
Second-to-second renewable power fluctuations can severely hinder the frequency regulation performance of modern isolated microgrids, as these typically have a low inertia and significant renewable energy integration. In this context, the present paper studies the coordinated control of Thermostatically Controlled Loads (TCLs) for managing short-term power imbalances, and their integration in microgrid operations through the use of aggregate TCL models. In particular, two computationally efficient and accurate aggregate TCL models are developed: a virtual battery model representing the aggregate flexibility of TCLs considering solar irradiance heat gains and wall/floor heat transfers, and a frequency transient model representing the aggregate dynamics of a TCL collection considering communication delays and the presence of model uncertainty and time-variability. The proposed aggregate TCL models are then used to design a practical Energy Management System (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 TCL models, as well as the economic and reliability benefits resulting from using these aggregate models to integrate TCLs in microgrid operations.
An Energy Management System With Short-Term Fluctuation Reserves and Battery Degradation for Isolated Microgrids
(Institute of Electrical and Electronics Engineers (IEEE), 2021-08-10) Cordova, Samuel; Canizares, Claudio; Lorca, Alvaro; Olivares, Daniel E.
Due to the low-inertia and significant renewable generation variability in isolated microgrids, short time-scale fluctuations in the order of seconds can have a large impact on a microgrid’s frequency regulation performance. In this context, the present paper presents a mathematical model for an Energy Management System (EMS) that takes into account the operational impact of the short-term fluctuations stemming from renewable generation rapid changes, and the role that renewable curtailment and batteries, including their degradation, can play to counter-balance these variations. Computational experiments on the real Kasabonika Lake First Nation microgrid and CIGRE benchmark test system show the operational benefits of the proposed EMS, highlighting the need to properly model short-term fluctuations and battery degradation in EMS for isolated microgrids with significant renewable integration.
Frequency-Constrained Energy Management System for Isolated Microgrids
(Institute of Electrical and Electronics Engineers (IEEE), 2022-04-28) Cordova, Samuel; Canizares, Claudio A.; Lorca, Alvaro; Olivares, Daniel E.
Second-to-second power imbalances stemming from renewable generation can have a large impact on the frequency regulation performance of isolated microgrids, as these are characterized by low inertia and, more commonly nowadays, significant renewable energy penetration. Thus, the present paper develops a novel frequency-constrained Energy Management System (EMS) that takes into account the impact of short-term power fluctuations on the microgrid’s operation and frequency regulation performance. The proposed EMS model is based on accurate linear equations describing frequency deviation, rate-of-change-of-frequency, and regulation provision in daily microgrid operations. Dynamic simulations on a realistic CIGRE benchmark test system show the economic and reliability benefits of the presented EMS model, highlighting the need of incorporating fast power fluctuations and their impact on frequency dynamics in EMSs for sustainable isolated microgrids.
Robust Energy Management of Isolated Microgrids
(Institute of Electrical and Electronics Engineers (IEEE), 2018-05-07) Lara, Jose Daniel; Olivares, Daniel E.; Canizares, Claudio A.
This paper presents the mathematical formulation and architecture of a robust energy management system for isolated microgrids featuring renewable energy, energy storage, and interruptible loads. The proposed strategy addresses the challenges of renewable energy variability and forecast uncertainty using a two-stage decision process combined with a receding horizon approach. The first-stage decision variables are determined using a cutting-plane algorithm to solve a robust unit commitment; the second stage solves the final dispatch commands using a three-phase optimal power flow. This novel approach is tested on a modified International Council on Large Electric Systems (CIGRE) test system under different conditions. The proposed algorithm is able to produce reliable dispatch commands without considering probabilistic information from the forecasting system. These results are compared with deterministic and stochastic formulations. The benefits of the proposed control are demonstrated by a reduction in load interruption events and by increasing available reserves without an increase in overall costs.
Stability Analysis of Unbalanced Distribution Systems With Synchronous Machine and DFIG Based Distributed Generators
(Institute of Electrical and Electronics Engineers (IEEE), 2014-07-30) Nasr-Azadani, Ehsan; Canizares, Claudio A.; Olivares, Daniel E.; Bhattacharya, Kankar
There are many technical aspects and challenges in distributed generation (DG) that have not been properly understood and addressed so far. Distribution systems cannot be considered as balanced three-phase systems, because these are inherently unbalanced in steady-state operation. A full characterization of the unbalanced system with respect to system stability allows a better understanding of the dynamic behavior of such systems. This paper presents a comprehensive investigation of the effects of system unbalance on the stability of the distribution systems with synchronous generator (SG) and doubly-fed induction generator (DFIG) based DG units at different loading levels. Detailed steady-state and dynamic analyses of the system are performed. Based on classical voltage, small-perturbation and transient stability studies, it is demonstrated that system unbalance can significantly affect the distribution system dynamic performance, in ways that have not been discussed in the technical literature so far. A simple and effective control strategy based on an Unbalanced Voltage Stabilizer (UVS) is also proposed to improve the system control and the stability of unbalanced distribution systems with SG and DFIG. Eigenvalue analyses and time-domain simulations (TDS) demonstrate the effectiveness of the proposed UVS for unbalance conditions.
Stochastic-Predictive Energy Management System for Isolated Microgrids
(Institute of Electrical and Electronics Engineers (IEEE), 2015-09-14) Olivares, Daniel E.; Lara, Jose D.; Canizares, Claudio A.; Kazerani, Mehrdad
This paper presents the mathematical formulation and control architecture of a stochastic-predictive energy management system for isolated microgrids. The proposed strategy addresses uncertainty using a two-stage decision process combined with a receding horizon approach. The first stage decision variables (unit commitment) are determined using a stochastic mixed-integer linear programming formulation, whereas the second stage variables (optimal power flow) are refined using a nonlinear programming formulation. This novel approach was tested on a modified CIGRE test system under different configurations comparing the results with respect to a deterministic approach. The results show the appropriateness of the method to account for uncertainty in the power forecast.
Trends in Microgrid Control
(Institute of Electrical and Electronics Engineers (IEEE), 2014-05-20) Olivares, Daniel E.; Mehrizi-Sani, Ali; Etemadi, Amir H.; Canizares, Claudio A.; Iravani, Reza; Kazerani, Mehrdad; Hajimiragha, Amir H.; Gomis-Bellmunt, Oriol; Saeedifard, Maryam; Palma-Behnke, Rodrigo; Jimenez-Estevez, Guillermo A.; Hatziargyriou, Nikos D.
The increasing interest in integrating intermittent renewable energy sources into microgrids presents major challenges from the viewpoints of reliable operation and control. In this paper, the major issues and challenges in microgrid control are discussed, and a review of state-of-the-art control strategies and trends is presented; a general overview of the main control principles (e.g., droop control, model predictive control, multi-agent systems) is also included. The paper classifies microgrid control strategies into three levels: primary, secondary, and tertiary, where primary and secondary levels are associated with the operation of the microgrid itself, and tertiary level pertains to the coordinated operation of the microgrid and the host grid. Each control level is discussed in detail in view of the relevant existing technical literature.