640 research outputs found

    Real-Time Load Frequency Control for an Isolated Microgrid System

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    Microgrids are small power grids with distinct operation characteristics; they can operate either independently or connected to larger grids, and usually a significant proportion of their generation capacity is comprised from intermittent resources such as solar and wind power generations. Power grids, in general, must operate such that the power generation and power demand are balanced at all times. Such balance is attained by implementing a Load Frequency Control (LFC) mechanism. The goal of LFC in a microgrid system is to maintain the system\u27s frequency within acceptable limits around nominal value under various conditions, such as fluctuating power demand and/or contingency situation such as unexpected loss of one or more of the system\u27s generating units, in order to ensure system\u27s stable operation. In case of small and isolated microgrid systems, however, the stability of the microgrid system is an issue of much greater significance as there are no means of connecting to primary grid power. The objective of this thesis is to design a Load Frequency Control (LFC) mechanism using Battery Storage System (BSS) and Diesel Generation (DG) units for an isolated microgrid system. The microgrid system under consideration is comprised from two DG units, a BSS unit, and two solar panels. The proposed LFC mechanism is implemented in a decentralized fashion. It was tested under different operation conditions; fluctuating power demand which represents the normal operation of power systems, and emergency situations where one of the system\u27s generation units was lost in each case. Results show that the proposed control systems were robust and successful to regulate the system\u27s frequency under all conditions. The microgrid model as well as the proposed control strategy is developed within the Simulink and SimPowerSystems environments

    Coordinated Control and Management of Multiple Electric Ships forming Seaport Microgrids

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    Electric thermal storage in isolated wind diesel power systems: use of distributed secondary loads for frequency regulation

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    Thesis (Ph.D.) University of Alaska Fairbanks, 2017Isolated coastal utilities in Arctic villages commonly use a mix of diesel and wind power to provide electrical service to their consumers. It is common for such communities to experience periods of high wind generation for which no immediate demand exists and either waste, curtail, or poorly utilize the surplus. The objective of the present work is to explore (through mathematical and numerical modelling) the technical feasibility of and optimization strategies for distributing this excess wind energy as domestic space heat for use as a cleaner, more economical alternative to fossil fuels. Autonomously controlled Electric Thermal Storage (ETS) devices are considered as a solution to decouple the supply of excess wind power with domestic heat demand without the need for communication infrastructure or a second distribution circuit. First, using numerical heat transfer analysis, it is shown that the performance of an ETS heater core can be generalized and expressed in terms of its physical properties and simple geometric dimensions in such a way as to inform system sizing and economic performance studies for prospective applications. Furthermore, a collection of autonomous ETS units is shown (using a full-scale lab-validated mathematical model) to possess the ability to assume the role of partial and/or sole frequency regulator on a hybrid wind-diesel system. Several design changes are proposed, which render the commercially-available units more amenable to frequency regulation. Ultimately, ETS is shown to be a promising alternative means of utilizing excess renewable energy for domestic space heat while providing additional stability to the electrical grid.Chapter 1 Introduction -- 1.1 Hybrid Wind-Diesel Systems -- 1.2 Frequency Regulation -- 1.3 Voltage Regulation -- 1.4 Energy Storage -- 1.5 Secondary Loads -- 1.6 Electric Thermal Storage -- 1.7 Summary and Organization of Subsequent Chapters -- 1.8 Nomenclature -- 1.9 References -- Chapter 2 Summary of Measurement and Modeling Methodologies -- 2.1 Numerical Heat Transfer - Measurement -- 2.2 Numerical Heat Transfer - Physical Modeling -- 2.3 Electromechanical Dynamics - Measurement -- 2.3.1 Field Measurements -- 2.3.2 Raw Data -- 2.3.3 Post Processing: RMS Values -- 2.3.4 Post Processing: Frequency and Power Factor -- 2.3.5 Post Processing: Impedance, Real Power, and Reactive Power -- 2.4 Electromechanical Dynamics - Modeling -- 2.4.1 Model Structure -- 2.4.2 Equivalent Circuit Simulation Process -- 2.4.3 Solution of Nonlinear Ordinary Differential Equations (ODEs) -- 2.5 References -- Chapter 3 Generalized Heat Flow Model of a Forced Air Electric Thermal Storage Heater Core -- 3.1 Abstract -- 3.2 Introduction -- 3.3 Model -- 3.3.1 Definitions -- 3.3.2 Structure -- 3.3.3 Governing Equations -- 3.3.4 Boundary Conditions -- 3.3.5 Material Properties -- 3.4 Analysis -- 3.4.1 Solution Linearization and Air Velocity Profile -- 3.4.2 Thermal Gradients -- 3.4.3 Parameter Sweep -- 3.5 Results and Discussion -- 3.5.1 One-parameter Model -- 3.5.2 Two-parameter Model -- 3.5.3 Core Energy Balance -- 3.5.4 Stove Modelling -- 3.6 Conclusions -- 3.7 Acknowledgements -- 3.8 Funding -- 3.9 Nomenclature -- 3.10 References -- Chapter 4 Development of a Full-Scale-Lab-Validated Dynamic Simulink© Model for a Stand-Alone -- Wind-Powered Microgrid -- 4.1 Abstract -- 4.2 Introduction -- 4.3 Mathematical Model -- 4.3.1 Diesel Engine/Governor Model -- 4.3.2 Synchronous Generator Model -- 4.3.3 Excitation System Model -- 4.3.4 Induction Generator Model -- 4.4 Data Collection -- 4.5 Results -- 4.5.1 Data Processing -- 4.5.2 Diesel Only (DO) Mode - Laboratory Results -- 4.5.3 Diesel Only (DO) Mode - Simulation Results -- 4.5.4 Wind-Diesel (WD) Mode -- 4.6 Conclusions -- 4.7 Future Work -- 4.8 Acknowledgements -- 4.9 References -- Chapter 5 Frequency Regulation by Distributed Secondary Loads on Islanded Wind-Powered Microgrids -- 5.1 Abstract -- 5.2 Introduction -- 5.3 Mathematical Model -- 5.3.1 Wind-Diesel Hybrid System -- 5.3.2 Individual ETS Units Response -- 5.3.3 Aggregate DSL Response -- 5.4 Analysis -- 5.4.1 Invariant Model Inputs (Machine Parameters) -- 5.4.2 Variable Model Inputs -- 5.4.3 Model Outputs -- 5.5 Results and Discussion -- 5.5.1 Synchronized Switching -- 5.5.2 Staggered Switching -- 5.5.3 Additional Observations and Discussion -- 5.6 Conclusion and Future Work -- 5.7 References -- Chapter 6 Modelling Integration Strategies for Autonomous Distributed Secondary Loads on High Penetration Wind-Diesel Microgrids -- 6.1 Abstract -- 6.2 Introduction -- 6.3 Model -- 6.3.1 System Requirements -- 6.3.2 System Components -- 6.3.3 Control Strategy -- 6.4 Results and Discussion -- 6.4.1 Ramp Simulation -- 6.4.2 Representative Simulation -- 6.4.3 Design Considerations -- 6.5 Conclusions -- 6.6 Acknowledgements -- 6.7 References -- Chapter 7 Results and Observations -- 7.1 Result and Observations of Chapter 3 -- 7.2 Results and Observations of Chapter 4 -- 7.3 Results and Observations of Chapter 5 -- 7.4 Results and Observations of Chapter 6 -- Chapter 8 Conclusions -- 8.1 Conclusions for Generalized Heat Flow Model of a Forced Air Electric Thermal Storage Heater Core -- 8.2 Conclusions for Development of a Full-Scale-Lab-Validated Dynamic Simulink© Model for a Stand-Alone Wind-Powered Microgrid -- 8.3 Conclusions for Frequency Regulation by Distributed Secondary Loads (DSLs) on Islanded Wind-Powered Microgrids -- 8.4 Conclusions for Modeling Integration Strategies for Autonomous Distributed Secondary Loads on High Penetration Wind-Diesel Microgrids -- 8.5 Suggestions for Future Research -- 8.6 Overall Conclusions -- 8.7 Acknowledgements

    Optimal Planning and Scheduling of Battery Energy Storage Systems for Isolated Microgrids

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    Balancing the energy demand in isolated microgrids is a critical issue especially in the presence of intermittent energy sources. Battery Energy Storage Systems (BESS) can be installed in such circumstances to supply the demand and support the reserve requirements of the isolated microgrid. However, due to the high installation costs of BESS, there is a need for proper mechanisms to select such systems and size them optimally. Furthermore, since BESS are often installed to serve multiple applications, these should be properly modeled to coordinate their different functionalities. In this thesis, a multi-year operational planning model is developed to determine the BESS optimal power rating and energy capacity along with the year of installation taking into account its coordinated operation. The model includes unit commitment formulation with renewable energy and BESS operational constraints. The optimal planning decisions are obtained for different BESS technologies under several scenarios of ownerships. The uncertain patterns of solar and wind resources and system demand are considered and several microgrid operational scenarios are created. A stochastic optimization model is developed to determine the optimal BESS size and installation year including the different states of the uncertain microgrid variables. The stochastic optimization model is solved using a decomposition based two-stage iterative approach to cope with the large computational burden of such problems.4 month

    Improved predictive current model control based on adaptive PR controller for standalone system based DG set

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    This paper investigates an improved current predictive model control (PCMC) strategy with a prediction horizon of one sampling time for voltage regulation in standalone system based on diesel engine driven fixed speed of a synchronous generator. An adaptive PR controller with anti-windup scheme is employed to achieve high performance regulation without saturation issues. In addition, new method to obtain the optimal parameters of the adaptive PR controller to achieve high performance during the transition and in steady state is provided. To balance the power at the point of common coupling (PCC) as well as to feed a clean power to the connected loads, a three-phase voltage source inverter (VSI) with LRC filter is controlled using the developed improved PCMC strategy, where the output filter current is controlled using the predicting of the system behaviour model in the future step, at each sampling prediction time. The performances of the proposed configuration and the improved control strategy are verified using Matlab/Simulink interface

    Grid-Connected Distributed Wind-Photovoltaic Energy Management: A Review

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    Energy management comprises of the planning, operation and control of both energy production and its demand. The wind energy availability is site-specific, time-dependent and nondispatchable. As the use of electricity is growing and conventional sources are depleting, the major renewable sources, like wind and photovoltaic (PV), have increased their share in the generation mix. The best possible resource utilization, having a track of load and renewable resource forecast, assures significant reduction of the net cost of the operation. Modular hybrid energy systems with some storage as back up near load center change the scenario of unidirectional power flow to bidirectional with the distributed generation. The performance of such systems can be enhanced by the accomplishment of advanced control schemes in a centralized system controller or distributed control. In grid-connected mode, these can support the grid to tackle power quality issues, which optimize the use of the renewable resource. The chapter aims to bring recent trends with changing requirements due to distributed generation (DG), summarizing the research works done in the last 10 years with some vision of future trends

    A second-order cone programming reformulation of the economic dispatch problem of bess for apparent power compensation in ac distribution networks

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    The problem associated with economic dispatch of battery energy storage systems (BESSs) in alternating current (AC) distribution networks is addressed in this paper through convex optimization. The exact nonlinear programming model that represents the economic dispatch problem is transformed into a second-order cone programming (SOCP) model, thereby guaranteeing the global optimal solution-finding due to the conic (i.e., convex) structure of the solution space. The proposed economic dispatch model of the BESS considers the possibility of injecting/absorbing active and reactive power, in turn, enabling the dynamical apparent power compensation in the distribution network. A basic control design based on passivity-based control theory is introduced in order to show the possibility of independently controlling both powers (i.e., active and reactive). The computational validation of the proposed SOCP model in a medium-voltage test feeder composed of 33 nodes demonstrates the efficiency of convex optimization for solving nonlinear programming models via conic approximations. All numerical validations have been carried out in the general algebraic modeling system.Fil: Montoya Giraldo, Oscar Danilo. Universidad Distrital Francisco José de Caldas; Colombia. Universidad Tecnológica de Bolívar; ColombiaFil: Gil González, Walter. Institución Universitaria Pascual Bravo; ColombiaFil: Serra, Federico Martin. Universidad Nacional de San Luis. Facultad de Ingeniería y Ciencias Agropecuarias. Laboratorio de Control Automático; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; ArgentinaFil: Hernández, Jesus C.. Universidad de Jaén; EspañaFil: Molina-Cabrera, Alexander. Universidad Tecnológica de Pereira; Colombi

    Electric Power Conversion and Micro-Grids

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    This edited volume is a collection of reviewed and relevant research chapters offering a comprehensive overview of recent achievements in the field of micro-grids and electric power conversion. The book comprises single chapters authored by various researchers and is edited by a group of experts in such research areas. All chapters are complete in themselves but united under a common research study topic. This publication aims at providing a thorough overview of the latest research efforts by international authors on electric power conversion, micro-grids, and their up-to-the-minute technological advances and opens new possible research paths for further novel developments

    A Generalized Optimal Planning Platform for Microgrids of Remote Communities Considering Frequency and Voltage Regulation Constraints

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    Access to electricity is a key factor behind development and expansion of modern societies, and electric power systems are the backbone infrastructure for economic growth of nations and communities. However, more than a billion people all over the world have no or limited access to electricity and are deprived of basic services. Furthermore, there are many communities that rely on small-scale isolated microgrids to supply their electric power demands, and many challenges exist in keeping those microgrids operating. The cost of operating isolated microgrids is a major issue which impacts the availability of a proper power network in remote communities. Hence, many organizations, communities and governments around the world are looking into alternative options for electrification of remote communities by considering Renewable Energy (RE) resources, such as wind and solar power, and utilization of Energy Storage Systems (ESS). This thesis investigates the feasibility of RE deployment in remote communities, by proposing a generalized optimal planning platform and conducting comprehensive simulation studies based on real measured data, and evaluates the impact of economic, technical and operation constraints on the planning of an isolated microgrid involving conventional generation, RE resources and ESS. This work suggests that further investigation should be made on the potential impacts of the integration of RE resource on systems operation constraints, such as frequency and voltage regulation, and the results justify the importance of such investigations. Detailed studies on the impact of operation constraints on the planning and sizing of the microgrid are performed. The impact of ESS on planning studies and its potential role in system operation are analyzed. Furthermore, the impact of RE integration on reduction of diesel generation and thus carbon footprint in remote communities is evaluated. The inclusion of a demand response management strategy in microgrid planning problem is considered and its impact on the integration of RE and ESS in remote communities is analyzed. The proposed planning platform is applied to the microgrid of Kasabonika Lake First Nation (KLFN), a northern Ontario remote community. The results indicate that RE and ESS integration projects are achievable considering alternative incentives and funding resources. It is also shown that frequency regulation constraints have remarkable impact on the sizing of the RE units and ESS. A sensitivity analysis is also performed in order to study the effect of variable parameters on the optimal design of the microgrid at KLFN

    Optimal Sizing and Power Management Strategies of Islanded Microgrids for Remote Electrification Systems

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    Over the past few years, electrification of remote communities with an efficient utilization of on-site energy resources has entered a new phase of evolution. However, the planning tools and studies for the remote microgrids are considered inadequate. Moreover, the existing techniques have not taken into account the impact of reactive power on component sizes. Thus, this thesis concentrates on optimal sizing design of an islanded microgrid (IMG), which is composed of renewable energy resources (RERs), battery energy storage system (BESS), and diesel generation system (DGS), for the purpose of electrifying off-grid communities. Owing to the utilization of both BESS and DGS, four power management strategies (PMSs) are modeled upon analyzing the impacts of reactive power to chronologically simulate the IMG. In this work, two single-objective optimization (SOO) and two multiobjective optimization (MOO) approaches are developed for determining the optimal component sizes in an IMG. Chronological simulation and an enumeration-based search technique are adopted in the first SOO approach. Then, an accelerated SOO approach is proposed by adopting an improved piecewise aggregate approximation (IPAA)-based time series and a genetic algorithm (GA). Next, an adaptive weighted sum (AWS) method, in conjunction with an enumeration search technique, is adopted in a bi-objective optimization approach. Finally, an elitist non-dominated sorting GA-II (NSGA-II) technique is proposed for MOO of the IMG by introducing three objective functions. The enumeration-based SOO approach ensures a global optimum, determines the optimal sizes and PMSs simultaneously, and offers a realistic solution. The accelerated SOO approach significantly reduces the central processing unit (CPU) time without largely deviating the life cycle cost (LCC). The bi-objective optimal sizing approach generates a large number of evenly spread trade-off solutions both in regular and uneven regions upon adopting the LCC and renewable energy penetration (REP) as the objective functions. Using the MOO approach, one can produce a diversified set of Pareto optimal solutions, for both the component sizes and PMSs, at a reduced computational effort. The effectiveness of the proposed approaches is demonstrated by simulation studies in the MATLAB/Simulink software environment
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