Browsing by Author "Canizares, Claudio A."

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Aggregated BESS Dynamic Models for Active Distribution Network Studies
(Institute of Electrical and Electronics Engineers (IEEE), 2020-12-31) Calero, Fabian; Canizares, Claudio A.; Bhattacharya, Kankar
This article proposes a transmission-system-level aggregated model of Battery Energy Storage Systems (BESSs) distributed through Active Distribution Networks (ADNs), to study the dynamic performance and services provided by these systems to power grids. ADNs comprise intelligent loads, local generation, particularly solar PV, and BESSs, which can provide different services to transmission grids, including voltage control, oscillation damping, frequency regulation, and active and reactive power injections. Proper equivalent models of the ADN components allow to evaluate the impact and integration of these networks on power grids. In this article, ADN's measurements of the aggregated response of the BESSs at the boundary bus with the transmission system are used to develop an aggregated black-box model based on two Neural Networks (NNs), one for active power and another for reactive power, with their optimal topology obtained using a Genetic Algorithm (GA). Detailed simulations are performed, using a commercial-grade software for power system analysis, of multiple BESSs connected to a CIGRE benchmark ADN connected to a bus of the 9-bus WSCC benchmark transmission network; the test ADN is then replaced by the proposed black-box model, with aggregated models of the loads and PV generation, demonstrating that the proposed model can accurately reproduce the results obtained.
An Effective Controllable Grid Interface for Microgrids
(Institute of Electrical and Electronics Engineers (IEEE), 2022-08-31) Tamimi, Behnam; Gu, Hanwen; Canizares, Claudio A.
The interest in the integration of distributed power generation and microgrids into power grids has significantly increased. In this context, interfacing microgrids with a host grid is of significant relevance, and therefore, in this paper, a cost-effective controllable grid interface for microgrids is proposed, modeled, and studied under various conditions, including smooth and abrupt power fluctuations, faults, and interface tripping. The proposed interface, named Microgrid Connector Controller (MGC), is an adequate and affordable alternative to the existing Back-to-Back (B2B) microgrid-grid interface, at a fraction of its capital costs. Thus, the proposed MGC’s performance is compared a B2B interface through detailed time-domain simulations in a realistic benchmark test system to demonstrate the controller’s capabilities. Compared with B2B, MGC’s direct frequency synchronization and power and voltage control capabilities makes it easier for microgrid operators to satisfy required standards and reduce wear and tear in grid equipment and customer loads. Finally, the MGC’s lower voltage ratings may translate into significantly smaller size and thus easier logistics and lower costs.
An Energy Management System for Isolated Microgrids With Thermal Energy Resources
(Institute of Electrical and Electronics Engineers (IEEE), 2020-02-11) Violante, Walter; Canizares, Claudio A.; Trovato, Michele A.; Forte, Giuseppe
A novel Energy Management System (EMS) model for an isolated microgrid, integrating thermal energy resources, such as Combined Heat and Power (CHP) units, boilers, Heat Pumps (HPs), and Thermal Storage System (TSS), while considering thermal load models, is proposed in this paper. The developed EMS is tested and validated with a real testbed microgrid located in Bari, Italy, which supplies both electricity and heat to a building at the Politecnico di Bari. The proposed EMS aims to minimize the fuel cost and includes thermal comfort requirements and building models, along with suitable models for CHP units and hot water-based TSS, based on an optimization problem formulated as a Mixed Integer Linear Programming (MILP) problem, which is readily handled with commercial solvers, making the EMS fit for online applications. The proposed EMS is compared with an electrical-only EMS, i.e., a practical EMS that does not include thermal systems, with the simulations carried out for different winter days demonstrating the economic benefits of accounting for thermal system models in a microgrid EMS, resulting in significant savings in the daily fuel cost.
Behind-the-meter compressed air energy storage feasibility and applications
(Elsevier, 2020-08-08) Anierobi, Chioma C.; Bhattacharya, Kankar; Canizares, Claudio A.
In this paper, the operations model of a behind-the-meter Small Scale Compressed Air Energy Storage (SS-CAES) facility is developed for an industrial customer with existing wells/caverns that can be re-purposed for air storage. The operations model seeks to minimize the electricity costs of the industrial customer, while determining the energy output and the corresponding charging and discharging decisions of the SS-CAES system. In order to examine the financial viability of a practical behind-the-meter SS-CAES facility, an economic analysis is carried out using real data of an industrial customer based in Ontario, Canada. Key parameters such as life cycle, CAES capacity and capital cost, and electricity price are considered for carrying out a sensitivity analysis, with the results showing that SS-CAES is economically viable for the current Ontario electricity tariff rate structure. The low capital cost of a SS-CAES project with a re-purposed storage cavern, and the high Global Adjustment charges levied in Ontario are shown to be a key determining factors for the economic feasibility of deployment of SS-CAES in Ontario.
Distributed Computing Architecture for Optimal Control of Distribution Feeders With Smart Loads
(Institute of Electrical and Electronics Engineers (IEEE), 2016-09-28) Mosaddegh, Abolfazl; Canizares, Claudio A.; Bhattacharya, Kankar; Fan, Hongbing
This paper presents a distributed computing architecture for solving a distribution optimal power flow (DOPF) model based on a smart grid communication middleware (SGCM) system. The system is modeled as an unbalanced three-phase distribution system, which includes different kind of loads and various components of distribution systems. In this paper, fixed loads are modeled as constant impedance, current and power loads, and neural network models of controllable smart loads are integrated into the DOPF model. A genetic algorithm is used to determine the optimal solutions for controllable devices, in particular load tap changers, switched capacitors, and smart loads in the context of an energy management system for practical feeders, accounting for the fact that smart loads consumption should not be significantly affected by network constraints. Since the number of control variables in a realistic distribution power system is large, solving the DOPF for real-time applications is computationally expensive. Hence, to reduce computational times, a decentralized system with parallel computing nodes based on an SGCM system is proposed. Using a “MapReduce” model, the SGCM system runs the DOPF model, communicates between master and worker computing nodes, and sends/receives data among different parts of parallel computing system. Compared to a centralized approach, the proposed architecture is shown to yield better optimal solutions in terms of reducing energy losses and/or energy drawn from the substation within adequate practical run-times for a realistic test feeder.
Duck-Curve Mitigation in Power Grids With High Penetration of PV Generation
(Institute of Electrical and Electronics Engineers (IEEE), 2021-10-25) Calero, Ivan; Canizares, Claudio A.; Bhattacharya, Kankar; Baldick, Ross
Small-scale PV generation has become popular with residential customers in several jurisdictions with high solar radiation, as an alternative to improve their carbon footprint and reduce their electricity bills. However, massive deployment of such distributed generation is creating a particular and undesirable shape in the net demand, which deepens at hours of peak solar PV injections at noon and suddenly rises towards the evening, known as the “duck curve”. Hence, this paper investigates the use of pre-cooling strategies in residential households to mitigate the duck-curve effects. To this aim, appropriate thermal models and simulations of houses are first developed and carried out to demonstrate the technical feasibility of pre-cooling in a house with a typical configuration, based on the Smart Residential Load Simulator (SRLS) developed at the University of Waterloo. Then, an aggregation technique is proposed to evaluate the effects on a large grid of different penetration levels of PV, and pre-cooling approaches to manage the duck-curve in California and Texas, concluding that such techniques are capable of substantially flattening the system net demand curve.
Dynamic Modeling of Battery Energy Storage and Applications in Transmission Systems
(Institute of Electrical and Electronics Engineers (IEEE), 2020-08-13) Calero, Fabian; Canizares, Claudio A.; Bhattacharya, Kankar
In this paper, a Battery Energy Storage System (BESS) dynamic model is presented, which considers average models of both Voltage Source Converter (VSC) and bidirectional buck-boost converter (dc-to-dc), for charging and discharging modes of operation. The dynamic BESS model comprises a simplified representation of the battery cells, which allows to simulate the effects of battery degradation, dc-to-dc converter, VSC, and the dynamics associated with the filter and transformer connecting the BESS to the grid. A decoupled dq-current control is used for the VSC, allowing the operation of the BESS in several modes, i.e., constant active and reactive power, constant power factor, voltage regulation, frequency regulation, oscillation damping, and a combination of the latter two. The proposed model is implemented in DSATools and tested for different contingencies on a benchmark system, and compared with a industry-grade BESS model used in power system dynamic studies. The importance of modeling the current control and dynamics of the dc-to-dc are demonstrated, especially when the battery cells are degraded due to, for instance, aging.
Energy Storage in Microgrids: Compensating for Generation and Demand Fluctuations While Providing Ancillary Services
(Institute of Electrical and Electronics Engineers (IEEE), 2017-08-16) Farrokhabadi, Mostafa; Solanki, Bharatkumar V.; Canizares, Claudio A.; Bhattacharya, Kankar; Koenig, Sebastian; Sauter, Patrick S.; Leibfried, Thomas; Hohmann, Soren
Driven by global environmental emission issues, energy access in remote communities, and tighter requirements for system resilience and reliability, electricity production is shifting from a centralized paradigm to a decentralized one. In this context, renewable energy sources (RESs) have proliferated over the past decade, exhibiting a steadily increasing trend. Thus, today, a large number of wind turbines and photovoltaic (PV) panels are connected to medium- (1-69 kV) and low-voltage (=1 kV) grids, with traditional integrated bulk power systems becoming decentralized in the presence of active distribution networks, where the flow of power is bidirectional between generators and "prosumers." In particular, with decreasing RES s costs, these technologies are becoming attractive solutions to bring energy to remote communities and/or replace expensive fossil-fuel-based generators. However, RES s such as wind and solar are intermittent sources of energy, difficult to predict, and prone to large output fluctuations-therefore, significantly affecting system voltage and frequency.
Equivalency of Continuation and Optimization Methods to Determine Saddle-Node and Limit-Induced Bifurcations in Power Systems
(Institute of Electrical and Electronics Engineers (IEEE), 2008-05-28) Avalos, Rafael J.; Canizares, Claudio A.; Milano, Federico; Conejo, Antonio J.
This paper presents a comprehensive and detailed study of an optimization-based approach to identify and analyze saddle-node bifurcations (SNBs) and limit-induced bifurcations (LIBs) of a power system model, which are known to be directly associated with voltage stability problems in these systems. Theoretical studies are presented, formally demonstrating that solution points obtained from an optimization model, which is based on complementarity constraints used to properly represent generators' voltage controls, correspond to either SNB or LIB points of this model. These studies are accomplished by proving that optimality conditions of these solution points yield the transversality conditions of the corresponding bifurcation points. A simple but realistic test system is used to numerically illustrate the theoretical discussions.
Frequency Regulation in Isolated Microgrids Through Optimal Droop Gain and Voltage Control
(Institute of Electrical and Electronics Engineers (IEEE), 2021-10-02) Alghamdi, Baheej; Canizares, Claudio A.
This article presents an adaptive active power droop controller and voltage setpoint control in isolated microgrids for optimal frequency response and stability after disturbances. The control scheme involves an optimal and model predictive control approach that continuously adjusts the active power droop gains and the voltage setpoints of Distributed Energy Resources (DERs) to maintain the frequency of the system within acceptable limits and enhance the primary frequency response of the system, while taking into account the active power sensitivity of the microgrid loads to the system's operating voltage. The proposed control scheme is tested, validated, and compared with previously proposed techniques using time-domain simulations for a test system based on a CIGRE medium voltage benchmark microgrid under different realistic conditions, demonstrating the advantages of the proposed approach.
Frequency Regulation Model of Bulk Power Systems With Energy Storage
(Institute of Electrical and Electronics Engineers (IEEE), 2021-08-30) Guzman E., Noela Sofia; Canizares, Claudio A.; Bhattacharya, Kankar; Sohm, Daniel
This paper presents a Frequency Regulation (FR) model of a large interconnected power system including Energy Storage Systems (ESSs) such as Battery Energy Storage Systems (BESSs) and Flywheel Energy Storage Systems (FESSs), considering all relevant stages in the frequency control process. Communication delays are considered in the transmission of the signals in the FR control loop and ESSs, and their State of Charge (SoC) management model is considered. The system, ESSs and SoC components are modelled in detail from a FR perspective. The model is validated using real system and ESSs data, based on a practical transient stability model of the North American Eastern Interconnection (NAEI), and the results show that the proposed model accurately represents the FR process of a large interconnected power network including ESS, and can be used for long-term FR studies. The impact of communication delays and SoC management of ESS facilities in the Area Control Error (ACE) is also studied and discussed, as well as the computational efficiency of the proposed FR model.
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.
Ground Source Heat Pump Modeling, Operation, and Participation in Electricity Markets
(Institute of Electrical and Electronics Engineers (IEEE), 2021-12-07) Peralta, Dario; Canizares, Claudio A.; Bhattacharya, Kankar
Over the last decades, Ground Source Heat Pump (GSHP) systems have grown in popularity and acceptance worldwide, having the potential to bring about significant benefits, especially if these systems participate in electricity markets through a load aggregator to optimize their operations and provide services such as load shifting and demand reduction, as proposed here. In this context, GSHP systems can be considered as an economically viable and attractive alternative to existing Heating Ventilation and Air Conditioning (HVAC) systems for space heating/cooling in buildings and houses from an aggregator point of view. Hence, this paper presents a detailed mathematical model for a GSHP with a vertical U-pipe Ground Heat eXchanger (GHX) configuration to provide residential space heating/cooling, integrating several such GSHPs into a load aggregator model. Then, a two-stage operational strategy for the GSHP price-taker aggregator participating in day-ahead and real-time electricity markets is proposed, to determine the optimal annual heating/cooling load dispatch to control the temperatures for a community of houses that minimizes the aggregator’s cost. Detailed numerical studies and comparisons with HVAC systems are carried out to demonstrate the feasibility and benefits of the proposed aggregated operation of GSHPs in electricity markets.
Implementation of Transient Stability Model of Compressed Air Energy Storage Systems
(Institute of Electrical and Electronics Engineers (IEEE), 2020-05-19) Calero, Ivan; Canizares, Claudio A.; Bhattacharya, Kankar
This paper discusses the implementation of a transient stability model of Compressed Air Energy Storage (CAES) systems in a power system analysis package. A block-diagram based model of a two-machine CAES system is proposed, including specific controls for active power, reactive power, and State of Charge (SoC), which consider limits associated with the cavern pressure. As an application, the model is implemented in Powertech's TSAT software connected to the 9-bus WSCC benchmark power system, which is then used to study the impact of a CAES facility in the transient and frequency stability of the system. Several contingencies are simulated comparing the CAES performance to a gas turbine and a base-case without storage, demonstrating that the CAES system improves the system transient stability due to its charging stage, controls, and additional inertia. Finally, the CAES model is used to study the effects of cavern sizes in the frequency of the system. It is shown that CAES systems have certain special characteristics that make them attractive as a storage technology to provide stability and regulation services, besides their energy arbitrage capabilities.
Microgrid Stability Definitions, Analysis, and Examples
(Institute of Electrical and Electronics Engineers (IEEE), 2019-06-28) Farrokhabadi, Mostafa; Canizares, Claudio A.; Simpson-Porco, John W.; Nasr, Ehsan; Fan, Lingling; Mendoza-Araya, Patricio A.; Tonkoski, Reinaldo; Tamrakar, Ujjwol; Hatziargyriou, Nikos; Lagos, Dimitris; Wies, Richard W.; Paolone, Mario; Liserre, Marco; Meegahapola, Lasantha; Kabalan, Mahmoud; Hajimiragha, Amir H.; Peralta, Dario; Elizondo, Marcelo A.; Schneider, Kevin P.; Tuffner, Francis K.; Reilly, Jim
This document is a summary of a report prepared by the IEEE PES Task Force (TF) on Microgrid Stability Definitions, Analysis, and Modeling, IEEE Power and Energy Society, Piscataway, NJ, USA, Tech. Rep. PES-TR66, Apr. 2018, which defines concepts and identifies relevant issues related to stability in microgrids. In this paper, definitions and classification of microgrid stability are presented and discussed, considering pertinent microgrid features such as voltage-frequency dependence, unbalancing, low inertia, and generation intermittency. A few examples are also presented, highlighting some of the stability classes defined in this paper. Further examples, along with discussions on microgrid components modeling and stability analysis tools can be found in the TF report.
Practical Framework for Frequency Stability Studies in Power Systems With Renewable Energy Sources
(Institute of Electrical and Electronics Engineers (IEEE), 2020-11-05) Ortiz-Villalba, Diego; Rahmann, Claudia; Alvarez, Ricardo; Canizares, Claudio A.; Strunck, Christoph
The transition from power systems dominated by synchronous machines to systems based on converter-based generation technologies (CGTs), is weakening currently robust power systems by reducing system inertia with the replacement of synchronous generators with low-inertia CGTs. From a frequency stability viewpoint, this is resulting in faster frequency dynamics and more frequent and larger frequency excursions after system contingencies, thus significantly affecting the stability of power systems dominated by CGTs, requiring detailed stability assessments to ensure the secure integration of CGTs. In this paper, a practical framework is presented for frequency stability studies based on time domain simulations of power systems with CGTs. A fundamental part of the proposed approach is the use of a filter to first identify worst-case scenarios among various possible system operating conditions. Once these worst-case scenarios are identified, a clustering technique is used to select representative worst-case operating conditions to evaluate the frequency stability of the system using time-domain simulations. The effectiveness of the proposed framework is demonstrated on the Chilean Northern Interconnected System (NIS), where it is shown that the proposed filter is able to quickly identify worst-case scenarios for further study. Moreover, we show that the selected representative operating conditions cover a wide-range of worst-case frequency responses, demonstrating the effectiveness of the proposed tool for frequency stability analyses.
Primary Frequency Control in Isolated Microgrids Using Thermostatically Controllable Loads
(Institute of Electrical and Electronics Engineers (IEEE), 2020-07-28) Mendieta, William; Canizares, Claudio A.
Hybrid renewable energy sources (RES)-diesel systems are now being considered as an economic, attractive and clean option for remote isolated microgrids, to offset diesel consumption by displacing generation from conventional units; however, system security and stability is a challenge as the penetration of RES increases. In this context, Demand Response (DR) can be used to increase grid flexibility, improve efficiency, and facilitate the penetration of RES. Thermostatically controllable loads (TCLs), i.e., electric water heaters (EWHs), air conditioners (ACs), and ground source heat pumps (GSHPs), are ideal candidates to participate in such a DR strategy, since their power consumption can be controlled without affecting consumer comfort. Therefore, this paper presents novel, computationally efficient, and adequate thermo-electrical dynamic models of ACs and GSHPs, along with an existing model of EWHs, to adapt and improve a decentralized DR strategy for Direct Load Control (DLC) for primary frequency regulation in hybrid isolated microgrids. Different cases studies are presented for a real microgrid to analyze and compare the system frequency response and determine the adequacy of the proposed approach and models, demonstrating their effectiveness for primary frequency control provision to facilitate higher RES penetrations.
Probabilistic Optimal Power Flow in Electricity Markets Based on a Two-Point Estimate Method
(Institute of Electrical and Electronics Engineers (IEEE), 2006-11-30) Verbic, Gregor; Canizares, Claudio A.
This paper presents an application of a two-point estimate method (2PEM) to account for uncertainties in the optimal power flow (OPF) problem in the context of competitive electricity markets. These uncertainties can be seen as a by-product of the economic pressure that forces market participants to behave in an “unpredictable” manner; hence, probability distributions of locational marginal prices are calculated as a result. Instead of using computationally demanding methods, the proposed approach needs2nruns of the deterministic OPF fornuncertain variables to get the result in terms of the first three moments of the corresponding probability density functions. Another advantage of the 2PEM is that it does not require derivatives of the nonlinear function used in the computation of the probability distributions. The proposed method is tested on a simple three-bus test system and on a more realistic 129-bus test system. Results are compared against more accurate results obtained from MCS. The proposed method demonstrates a high level of accuracy for mean values when compared to the MCS; for standard deviations, the results are better in those cases when the number of uncertain variables is relatively low or when their dispersion is not large.
Self-Scheduling Models of a CAES Facility Under Uncertainties
(Institute of Electrical and Electronics Engineers (IEEE), 2021-01-06) Zambroni de Souza, Matheus F.; Canizares, Claudio A.; Bhattacharya, Kankar
This paper presents two mathematical formulations to represent uncertainties in self-scheduling models of a price-taker Compressed Air Energy Storage (CAES) facility. The proposed model is from the point of view of the plant owner participating in the energy, spinning, and idle reserve markets. The first described formulation is based on Robust Optimization (RO) and the second one is based on Affine Arithmetic (AA) techniques, which are both range arithmetic methodologies, and consider the thermodynamic characteristics of the CAES facility for a more realistic representation. The implementation of both methods are tested, validated and compared with each other and with Monte Carlo Simulations (MCS) using prices from the Ontario market. From the simulation results, it can be observed that both methods have some similarities, presenting lower computational burden compared with MCS, and demonstrate the advantage of applying the proposed models for CAES plant owners to hedge against price uncertainties.