Waterloo Research

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Northern Lights: Access to Electricity in Canada's Northern and Remote Communities
(Institute of Electrical and Electronics Engineers (IEEE), 2014-06-12) Arriaga, Mariano; Canizares, Claudio A.; Kazerani, Mehrdad
Access to energy in many of the world's remote communities is still restricted; these locations only have access to simple and inexpensive local energy sources, such as biomass for cooking and kerosene lamps or candles for lighting. The World Bank and the International Energy Agency (IEA) perceive this energy deficit as a major obstacle to achieving community economic development as well as to obtaining adequate access to health services and clean water. Electricity is a flexible, modern source of energy that is considered to be one of the principal driving forces that stimulate community development and access to basic services in remote locations. Governments, private institutions, and nongovernmental organizations have gradually recognized these energy needs and have established electrification programs at the national and regional levels that aim at the gradual electrification of remote locations. The main objective is to give the reader a better understanding of the challenges and opportunities with regard to electricity generation in Canada's N&RCs beased on their use of renewable energy (RE) alternatives.
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.
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.
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.
Optimal Incentive Design for Targeted Penetration of Renewable Energy Sources
(Institute of Electrical and Electronics Engineers (IEEE), 2014-08-28) Das, Indrajit; Bhattacharya, Kankar; Canizares, Claudio
Environmental concerns arising from fossil-fuel-based generation have propelled the integration of less-polluting energy sources in the generation portfolio and simultaneously have motivated increased energy conservation programs. In today's deregulated electricity market, most participants [e.g., GENCOs and local distribution companies (LDCs)] focus on maximizing their profits, and thus they need to be incentivized to invest in renewable generation and energy conservation, which are otherwise not profitable ventures. Therefore, this paper proposes a novel holistic generation expansion plan (GEP) model that enables the central planning authority (CPA) to design optimal incentive rates for renewable integration and energy conservation targets, considering the investor interests and constraints. The model also determines the siting, sizing, timing, and technology required to adequately supply the projected demand over the planning horizon. The model is applied to the generation planning of Ontario, Canada, based on realistic data, to determine appropriate incentives for investors in renewable generation and energy conservation by LDCs. The obtained optimal incentives are shown to be similar to the ones currently in place in Ontario, with a slightly shorter payback period for investors. The effect of uncertainties associated with solar and wind energy availability on the GEP model is also examined using Monte Carlo simulations.
A Novel Affine Arithmetic Method to Solve Optimal Power Flow Problems With Uncertainties
(Institute of Electrical and Electronics Engineers (IEEE), 2014-05-02) Pirnia, Mehrdad; Canizares, Claudio A.; Bhattacharya, Kankar; Vaccaro, Alfredo
An affine arithmetic (AA) method is proposed in this paper to solve the optimal power flow (OPF) problem with uncertain generation sources. In the AA-based OPF problem, all the state and control variables are treated in affine form, comprising a center value and the corresponding noise magnitudes, to represent forecast, model error, and other sources of uncertainty without the need to assume a probability density function (pdf). The proposed AA-based OPF problem is used to determine the operating margins of the thermal generators in systems with uncertain wind and solar generation dispatch. The AA-based approach is benchmarked against Monte Carlo simulation (MCS) intervals in order to determine its effectiveness. The proposed technique is tested and demonstrated on the IEEE 30-bus system and also a real 1211-bus European system.
Optimal Operation of Climate Control Systems of Produce Storage Facilities in Smart Grids
(Institute of Electrical and Electronics Engineers (IEEE), 2014-08-07) Bozchalui, Mohammad Chehreghani; Canizares, Claudio A.; Bhattacharya, Kankar
This paper presents mathematical optimization models of produce storage facilities to optimize the operation of their energy systems in the context of smart grids. In the storage facilities, climate control of the storage rooms consumes considerable energy; thus, in this paper, a mathematical model of storage facilities appropriate for their optimal operation is developed, so that it can be implemented as a supervisory control in existing climate controllers. The proposed model incorporates weather forecasts, electricity price information, and the end-user preferences to optimally operate existing climate control systems in storage facilities. The objective is to minimize total energy costs and demand charges while considering important parameters of storage facilities, i.e., inside temperature and humidity should be kept within acceptable ranges. The performance of the proposed model for various electricity prices and weather conditions and their variations are studied via Monte Carlo Simulations (MCS). The presented simulation results show the effectiveness of the proposed model to reduce total energy costs while maintaining required operational constraints.
Optimal Energy Management of Greenhouses in Smart Grids
(Institute of Electrical and Electronics Engineers (IEEE), 2014-12-23) Bozchalui, Mohammad Chehreghani; Canizares, Claudio A.; Bhattacharya, Kankar
This paper presents a novel hierarchical control approach and new mathematical optimization models of greenhouses, which can be readily incorporated into energy hub management systems (EHMSs) in the context of smart grids to optimize the operation of their energy systems. In greenhouses, artificial lighting, CO2 production, and climate control systems consume considerable energy; thus, a mathematical model of greenhouses appropriate for their optimal operation is proposed, so that it can be implemented as a supervisory control in existing greenhouse control systems. The objective is to minimize total energy costs and demand charges while considering important parameters of greenhouses; in particular, inside temperature and humidity, CO2 concentration, and lighting levels should be kept within acceptable ranges. Therefore, the proposed model incorporates weather forecasts, electricity price information, and the end-user preferences to optimally operate existing control systems in greenhouses. Effects of uncertainty in electricity price and weather forecast on optimal operation of the storage facilities are studied through Monte Carlo simulations. The presented simulation results show the effectiveness of the proposed model to reduce total energy costs while maintaining required operational constraints.
Smart Distribution System Operations With Price-Responsive and Controllable Loads
(Institute of Electrical and Electronics Engineers (IEEE), 2014-12-09) Sharma, Isha; Bhattacharya, Kankar; Canizares, Claudio
This paper presents a new modeling framework for analysis of impact and scheduling of price-responsive as well as controllable loads in a three-phase unbalanced distribution system. The price-responsive loads are assumed to be linearly or exponentially dependent on price, i.e., demand reduces as price increases and vice versa. The effect of such uncontrolled price-responsive loads on the distribution feeder is studied as customers seek to reduce their energy cost. Secondly, a novel constant energy load model, which is controllable by the local distribution company (LDC), is proposed in this paper. A controllable load is one that can be scheduled by the LDC through remote signals, demand response programs, or customer-end home energy management systems. Minimization of cost of energy drawn by LDC, feeder losses, and customers cost pertaining to the controllable component of the load are considered as objectives from the LDCs and customers' perspective. The effect of a peak demand constraint on the controllability of the load is further examined. The proposed models are tested on two feeders: 1) the IEEE 13-node test feeder; and 2) a practical LDC feeder system. Detailed studies examine the operational aspects of price-responsive and controllable loads on the overall system. It is observed that the LDC controlled load model results in a more uniform system load profile, and that with a reduction in the peak demand cap, the energy drawn decreases, consequently reducing feeder losses and LDC's and customers' costs.
Optimal Operation of Industrial Energy Hubs in Smart Grids
(Institute of Electrical and Electronics Engineers (IEEE), 2014-12-18) Paudyal, Sumit; Canizares, Claudio A.; Bhattacharya, Kankar
This paper presents the development of a generic optimal industrial load management (OILM) model, which can be readily incorporated into energy hub management systems (EHMSs) for industrial customers, in interaction with local distribution companies (LDCs), for automated and optimal scheduling of their processes. The mathematical models comprise an objective function to minimize the total energy costs and/or demand charges for industrial customers, and a set of equality and inequality constraints to represent the industrial process, storage units, distribution system components, operator's requirements, and other relevant constraints. The effectiveness of the proposed OILM model is demonstrated in two industrial customers: 1) a flour mill; and 2) a water pumping facility. The results show that the proposed OILM model, in conjunction with communication and control infrastructures at the customer and LDC levels, would allow optimal operation of industrial EHMSs in smart grids.
Gene transcription and splicing of T-type channels are evolutionarily-conserved strategies for regulating channel expression and gating
(Public Library of Science (PLOS), 2012) Senatore, Adriano; Spafford, J. David
T-type calcium channels operate within tightly regulated biophysical constraints for supporting rhythmic firing in the brain, heart and secretory organs of invertebrates and vertebrates. The snail T-type gene, LCav3 from Lymnaea stagnalis, possesses alternative, tandem donor splice sites enabling a choice of a large exon 8b (201 aa) or a short exon 25c (9 aa) in cytoplasmic linkers, similar to mammalian homologs. Inclusion of optimal 25c exons in the III-IV linker of T-type channels speeds up kinetics and causes hyperpolarizing shifts in both activation and steady-state inactivation of macroscopic currents. The abundant variant lacking exon 25c is the workhorse of embryonic Cav3 channels, whose high density and right-shifted activation and availability curves are expected to increase pace-making and allow the channels to contribute more significantly to cellular excitation in prenatal tissue. Presence of brain-enriched, optional exon 8b conserved with mammalian Cav3.1 and encompassing the proximal half of the I-II linker, imparts a ~50% reduction in total and surface-expressed LCav3 channel protein, which accounts for reduced whole-cell calcium currents of +8b variants in HEK cells. Evolutionarily conserved optional exons in cytoplasmic linkers of Cav3 channels regulate expression (exon 8b) and a battery of biophysical propertie4s (exon 25c) for tuning specialized firing patterns in different tissues and throughout development.
Optimal Operation of Distribution Feeders in Smart Grids
(Institute of Electrical and Electronics Engineers (IEEE), 2011-02-04) Paudyal, Sumit; Canizares, Claudio A.; Bhattacharya, Kankar
This paper presents a generic and comprehensive distribution optimal power flow (DOPF) model that can be used by local distribution companies (LDCs) to integrate their distribution system feeders into a Smart Grid. The proposed three-phase DOPF framework incorporates detailed modeling of distribution system components and considers various operating objectives. Phase specific and voltage dependent modeling of customer loads in the three-phase DOPF model allows LDC operators to determine realistic operating strategies that can improve the overall feeder efficiency. The proposed distribution system operation objective is based on the minimization of the energy drawn from the substation while seeking to minimize the number of switching operations of load tap changers and capacitors. A novel method for solving the three-phase DOPF model by transforming the mixed-integer nonlinear programming problem to a nonlinear programming problem is proposed which reduces the computational burden and facilitates its practical implementation and application. Two practical case studies, including a real distribution feeder test case, are presented to demonstrate the features of the proposed methodology. The results illustrate the benefits of the proposed DOPF in terms of reducing energy losses while limiting the number of switching operations.
Re-defining the reactive power dispatch problem in the context of competitive electricity markets
(Institution of Engineering and Technology (IET), 2010-02-05) Cañizares, C.A.; Bhattacharya, K.; El-Samahy, I.; Haghighat, H.; Pan, J.; Tang, C.
This study proposes a novel reactive power dispatch model that takes into account both the technical and economical aspects associated with reactive power dispatch in the context of the new operating paradigms in competitive electricity markets. The main objective of the proposed model is to minimise the total amount of dollars paid by the system operator to the generators for providing the required reactive power support. The real power generation is decoupled and assumed fixed during the reactive power dispatch procedures; however, because of the effect of reactive power on real power, a re-schedule in the real power generation is allowed within given limits. The 32-bus CIGRE benchmark system is used to illustrate the proposed reactive power dispatch technique. The developed model is generic in nature and designed to be adopted by system operators in any electricity market structure, as demonstrated by its application to Ontario's grid considering its market rules for reactive power payments.
Optimal Transition to Plug-In Hybrid Electric Vehicles in Ontario, Canada, Considering the Electricity-Grid Limitations
(Institute of Electrical and Electronics Engineers (IEEE), 2009-06-26) Hajimiragha, Amirhossein; Canizares, Claudio A.; Fowler, Michael W.; Elkamel, Ali
This paper analyzes the feasibility of optimally utilizing Ontario's grid potential for charging plug-in hybrid electric vehicles (PHEVs) during off-peak periods. Based on a simplified zonal model of Ontario's electricity-transmission network and a zonal pattern of base-load generation capacity from 2009 to 2025, an optimization model is developed to find the optimal, as well as maximum, penetrations of PHEVs into Ontario's transport sector. The results of this paper demonstrate that the present and projected electricity grid in Ontario can be optimally exploited for charging almost 6% of the total vehicles in Ontario or 12.5% of the vehicles in Toronto's transport sector by 2025; this corresponds to approximately 500 000 PHEVs that can be charged from the grid without any additional transmission or power-generation investments beyond those currently planned.
Stability Modeling and Comparative Study of Series Vectorial Compensators
(Institute of Electrical and Electronics Engineers (IEEE), 2009-12-08) Gonzalez, Juan Miguel; Canizares, Claudio A.; Ramirez, Juan M.
Complete stability analyses, including voltage, small perturbation and transient stability studies, and the associated models and controls of a series vectorial compensator (SVeC) are presented in this paper. It is also shown through detailed simulations that the SVeC is a competitive device against series power-flow controllers and it might be a better option for similar purposes where space and costs are at premium. Hence, a full comparative evaluation of this controller with respect to controllers used mainly for oscillation control in transmission corridors, namely, thyristor-controlled series capacitors (TCSC) and series static synchronous compensators (SSSC), is also presented for the first time. The IEEE 14-bus benchmark system and a 190-bus, 46-machine model of the Mexican grid are used for illustrative and comparison purposes. The results obtained show that the SVeC has better oscillation damping characteristics than the TCSC and SSSC, hence making these types of controllers a competitive alternative against existing series flexible ac transmission system (FACTS) controllers for dynamic series compensation of transmission lines.
Gossip-Based Visibility Control for High Performance Geo-Distributed Transactions
(Springer Nature, 2021-01) Fan, Hua; Golab, Wojciech
Providing ACID transactions under conflicts across globally distributed data is the Everest of transaction processing protocols. Transaction processing in this scenario is particularly costly due to the high latency of cross-continent network links, which inflates concurrency control and data replication overheads. To mitigate the problem, we introduce Ocean Vista—a novel distributed protocol that guarantees strict serializability. We observe that concurrency control and replication address different aspects of resolving the visibility of transactions, and we address both concerns using a multi-version protocol that tracks visibility using version watermarks and arrives at correct visibility decisions using efficient gossip. Gossiping the watermarks enables asynchronous transaction processing and acknowledging transaction visibility in batches in the concurrency control and replication protocols, which improves efficiency under high cross-data center network delays. In particular, Ocean Vista can access conflicting transactions in parallel and supports efficient write-quorum/read-one access using one round trip in the common case. We demonstrate experimentally in a multi-data center cloud environment that our design outperforms a leading distributed transaction processing engine (TAPIR) more than tenfold in terms of peak throughput, albeit at the cost of additional latency for gossip and a more restricted transaction model. The latency penalty is generally bounded by one wide area network (WAN) round trip time (RTT), and in the best case (i.e., under light load) our system nearly breaks even with TAPIR by committing transactions in around one WAN RTT.
Economic Impact of Electricity Market Price Forecasting Errors: A Demand-Side Analysis
(Institute of Electrical and Electronics Engineers (IEEE), 2009-10-30) Zareipour, Hamidreza; Canizares, Claudio A.; Bhattacharya, Kankar
Several techniques have been proposed in the literature to forecast electricity market prices and improve forecast accuracy. However, no studies have been reported examining the economic impact of price forecast inaccuracies on forecast users. Therefore, in this paper, the application of electricity market price forecasts to short-term operation scheduling of two typical and inherently different industrial loads is examined and the associated economic impact is analyzed. Using electricity market price forecasts as the expected next-day electricity prices, optimal operating schedules and the associated costs are determined for each load. These costs are compared with those of a ¿perfect¿ price forecast scenario in which actual prices are used to determine the operating schedules. Numerical results and discussions are provided based on price forecasts with different error characteristics.
Robust Optimal Power Flow Solution Using Trust Region and Interior-Point Methods
(Institute of Electrical and Electronics Engineers (IEEE), 2010-09-16) Sousa, Andréa A.; Torres, Geraldo L.; Canizares, Claudio A.
A globally convergent optimization algorithm for solving large nonlinear optimal power flow (OPF) problems is presented. As power systems become heavily loaded, there is an increasing need for globally convergent OPF algorithms. By global convergence, one means the optimization algorithm being able to converge to an OPF solution, if at least one exists, for any choice of initial point. The globally convergent OPF presented is based on an infinity-norm trust region approach, using interior-point methods to solve the trust region subproblems. The performance of the proposed trust region interior-point OPF algorithm, when applied to the IEEE 30-, 57-, 118-, and 300-bus systems, and to an actual 1211-bus system, is compared with that of two widely used nonlinear interior-point methods, namely, a pure primal-dual and its predictor-corrector variant.
Effect of Reactive Power Limit Modeling on Maximum System Loading and Active and Reactive Power Markets
(Institute of Electrical and Electronics Engineers (IEEE), 2010-02-05) Tamimi, Behnam; Canizares, Claudio A.; Vaez-Zadeh, Sadegh
This paper presents a comparative investigation of various representations of reactive power limits in maximum loadability and active and reactive power market studies. Previously proposed optimal power flow (OPF) models for these types of analyses are first reviewed and briefly discussed. Different models for representing reactive power limits in these optimization problems are then presented, concentrating in particular on the proper modeling of the generators' capability curves as terminal voltages change, which has been identified as a shortcoming of previous studies. Comparative numerical analyses of the effect of various reactive power limit models in maximum loading and active and reactive power dispatch and pricing levels are presented and discussed, to thus quantify the effect these various limit representations have on the corresponding results. Two test systems, namely, the CIGRE-32 benchmark system and a 1211-bus dispatch model of a European network, are used for numerical studies. The presented results show that in most OPF applications, the improvement on the reactive power limits representation lead to subtle differences at the cost of increased computational complexity, which in some cases may be difficult to justify in practice.
Sustainable convergence of electricity and transport sectors in the context of a hydrogen economy
(Elsevier, 2011-04-03) Hajimiragha, Amir H.; Cañizares, Claudio A.; Fowler, Michael W.; Moazeni, Somayeh; Elkamel, Ali; Wong, Steven
This paper analyzes the electricity and transport sectors within a single integrated framework and presents the capabilities of this integrated approach to realize an environmentally and economically sustainable transport sector based on fuel cell vehicles (FCVs). A comprehensive robust optimization planning model for the transition to FCVs is developed, considering the constraints of both electricity and transport sectors. This model is finally applied to the real case of Ontario, Canada to determine the Ontario’s grid potential to support these vehicles in the transport sector for a planning horizon ending in 2025. With a reasonable trade-off between optimality and conservatism, it is found that more than 170,000 FCVs can be introduced into Ontario’s transport sector by 2025 without jeopardizing the reliability of the system or any additional grid investments such as new power generation and transmission installations.

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