Program Topic: Micro-Grid – Stability & Optimization

W1-2Wednesday 09:40-10:40

09:40 Robust MPC-Based Optimal Sizing and Energy Management of a Hybrid Source for Remote Communities

Mohamed Taha (University of Alberta, Canada); Yasser Mohamed (University of Alberta, Canada)

In this paper, robust optimal sizing and energy management of a hybrid energy source for remote communities, based on the model predictive control (MPC) approach, is proposed. The proposed optimal sizing approach considers both the hourly and seasonal uncertainties (the wind speed and solar irradiation) associated with the renewable energy resources, as well as the load power forecast uncertainty. Moreover, the demand-side management is also taken into account by including the deferrable loads in the design problem. The robust optimization problem is formulated as a multi-objective mixed-integer nonlinear programming (MINLP) problem in order to achieve three objectives: (1) to minimize the total system cost (including the investment cost, operation and maintenance cost); (2) to minimize the total dump energy; and (3) to minimize the pollutant gas emissions from the diesel generator (DG) unit. The optimal planning decisions are determined by solving the optimization problem for the worst-case uncertain conditions. Numerical simulations are carried out to verify the effectiveness of the proposed approach. Further, sensitivity analysis of the planning results with different levels of uncertainty is carried out.

10:00 Robust MPC-Based Energy Management System of a Hybrid Energy Source for Remote Communities

Mohamed Taha (University of Alberta, Canada); Yasser Mohamed (University of Alberta, Canada)

In this paper, a robust energy management system (EMS) of a hybrid energy source for a remote community is proposed. The proposed EMS is based on the model predictive control (MPC) approach. The hybrid energy source consists of dispatchable; nondispatchable; and battery storage, which can work in both grid-connected and isolated modes. Moreover, the demand-side management is considered by the inclusion of deferrable and dump loads in the optimization problem. The uncertainties associated with renewable energy sources such as the wind speed and the solar irradiation as well as the demand power are taken into account. The optimization problem was formulated as a mixed-integer nonlinear (MINL) programming framework with three objectives: (1) to minimize the total operating cost, (2) to minimize the pollutant gas emissions, and (3) to minimize the dump energy, especially in the isolated mode. The battery daily number of cycles (DNC), the minimum state of charge (SOC), and the initial SOC are considered as decision variables in the optimization problem which are optimally determined by the EMS to minimize the total system operating cost while considering all the practical performance and side constraints of the different energy sources. Four different case studies are considered to verify the proposed EMS system. The results show that the values of the optimal DNC, the minimum SOC, and the initial SOC of the BS, which depend on the pool price variation, have a significant effect on the total operation cost.

10:20 Real-Time Implementation & Evaluation of Grid-Connected Microgrid Energy Management System

Carlos Rangel (McGill University, Canada); Diego Mascarella (McGill University, Canada); Geza Joos (McGill University, Canada)

This paper proposes the real-time implementation of an energy management system (EMS) optimization sequence and enumerates a set of performance metrics for grid-connected microgrids. The operation and performance of the proposed microgrid EMS is validated using a real-time hardware-in-the-loop (HIL) testing platform. The test system emulates the microgrid network, the distributed energy resources (DER) and their corresponding local controllers on a real-time-digital-simulator (RTDS). The microgrid EMS script under evaluation runs on a desktop computer and interfaces the RTDS through a separate digital controller. Real-time simulation results are used to quantify the performance of a grid-connected microgrid EMS in terms of power import constraints, the levelized cost of energy and fuel consumption provided by the DER scheduling algorithms. A utility 25 kV distribution test-line featuring a Type-4 wind turbine generator (WTG), battery energy storage system (BESS), diesel generator and controllable loads has been used for the benchmark test system.

W2-2Wednesday 11:00-12:20

11:00 An Application of a Centralized Model Predictive Control on Microgrids

Khaled Hajar (Gipsa-lab, France); Ahmad Hably (Université Grenoble Alpes, GIPSA-Lab, France)

In this paper, a centralized model predictive control (MPC) is applied on a group of interconnected microgrids (MGs) with the main grid. The objective is to maximize the benefits from one hand for all the elements constituting the MGs and for the main grid on the other hand. The MPC application in our case needs a forecasting information about energy prices, production power, and loads. The algorithm is tested on five interconnected MGs with main grid. Results have shown the performance of the proposed algorithm, especially for the benefits of MG owners, the coordination between MGs while respecting of the constraints related to each on of them.

11:20 Improved Reactive Power Sharing with Adaptive Droop Control in Islanded Microgrids

Javad Fattahi (University of Ottawa, Canada); Joan Haysom (Leidos Canada & University of Ottawa, Canada); John Cook (University of Ottawa, Canada); Karin Hinzer (University of Ottawa, Canada); Henry Schriemer (University of Ottawa, Canada)

Appropriate control strategies for power sharing between multiple generation units operating in parallel are required to create a stable AC microgrid bus. In this paper, we explore the droop control strategy, implemented by power electronics units, to maintain a stable AC bus voltage without the need for a separate (central) communication layer. In particular, our suggested control method is based on adaptive control. Fundamentally in microgrids, due to the effects of feeder and line impedance, the droop control method is subject to real and reactive power coupling and steady-state reactive power sharing errors, and in particular for complex microgrid configurations, the reactive power sharing poses certain challenges. To improve the reactive power sharing equalization, an enhanced adaptive strategy has been utilized to calculate a droop coefficient for reactive power control, where the reactive power error has been compensated through the injection of small real power disturbances. Root locus analysis of a representative microgrid with three inverters has been undertaken to confirm that stable solutions are feasible.

11:40 Power Flow Analysis of AC/DC Hybrid Microgrids

Abdelsalam Eajal (University of Waterloo, Canada); Mohamed Abdelwahed (University of Waterloo, Canada); Ehab El-Saadany (Waterloo University, Canada); Kumaraswamy Ponnambalam (University of Waterloo, Canada)

The future smart grid can have an AC/DC hybrid structure that enables the integration of AC/DC energy supply and demand, thus permitting the formation of AC/DC hybrid microgrids (HMGs). The AC/DC HMG is a promising concept that provides the envisioned smart grid with the plug-and-play feature. Nevertheless, understanding such hybrid systems, especially during islanding, require an accurate and robust load flow program. To this end, this paper proposes a novel robust power flow algorithm for isolated AC/DC HMGs. The power flow problem is formulated as a least-squares minimization problem, and solved using the Levenberg-Marquardt algorithm. The accuracy of the proposed load flow algorithm is validated against time domain simulation results, while its robustness is demonstrated on a highly-resistive network. The proposed load flow algorithm is expected to reveal the light for further studies on AC/DC HMGs.

12:00 Educational Microgrid- A Microgrid Training Platform and Emulator

Clinton Murtagh (British Columbia Institute of Technology, Canada); Omar Mihirig (British Columbia Institute of Technology, Canada); Ygor Gonzalez (British Columbia Institute of Technology, Canada); Ali Palizban (British Columbia Institute of Technology, Canada); Katherine Manson (British Columbia Institute of Technology, Canada)

With the ever growing demand for power and development of renewable energy technologies, the concepts of distributed generation and microgrids are quickly coming to the forefront. A microgrid is an electrical power grid where the load and power generation are within close proximity. Increasingly educational institutions are trying to capitalize on the need to educate future and current professional engineers in the design, maintenance, and operation of a microgrid. The main concept behind our project is to create a live, scaled down microgrid system which incorporates renewable energy sources and interconnection to utility power, all using industry standard equipment. Our educational microgrid platform will allow for comprehensive education with practical hands-on experience which will be useful for practicing engineers, undergrad students, as well as technologists and technicians. We have designed and tested a prototype that can be used as a basis for future instruction for the subject, which will in turn benefit students, education, and the industry as a whole.

W3-2Wednesday 13:20-15:00

13:20 Design of Renewable Energy System for a Remote Mobile Office in Newfoundland

Emadeddin Hussein (Memorial University of Newfoundland, Canada); Tariq Iqbal (Memorial University of Newfoundland, Canada)

Renewable Energy Systems are becoming a common choice for small communities in Canada where the cost of diesel fuel are high. In this paper, a PV/Wind hybrid system is been considered for supplying an electrical load of a Mobile office which is proposed and presented along with relevant statistics. An optimal configuration of different renewable energy system is been obtained. The optimal configuration has been determined by taking the total cost as the objective function. The system optimization done through optimization features from NREL, HOMER. The results show the hybrid renewable energy system is a cost effective solution. Furthermore, it is expected that the proposed system will help companies to provide uninterrupted power for their sites in remote areas.

13:40 Optimal Sizing of a Stand-Alone Hybrid Energy System for Water Pumping in Sirte, Libya

Faisal Alkarrami (Memorial University, Canada); Mohammad Tariq Iqbal (Memorial University of Newfoundland, Canada); Kevin Pope (Memorial University of Newfoundland, Canada)

In this paper, the size optimization of standalone Photovoltaic (PV)/Wind turbine hybrids system for water pumping in Sirte City, Libya are compared using HOMER Pro, HOMER Beta, and iHOGA softwares, specifically the cost of energy (COE), total net present cost (NPC), and size of the system. Various loads of water pumping for farm land are used. The optimal system suggested by iHOGA had the lowest NPC but highest COE, whereas HOMER Pro had the highest NPC but lowest COE. The results are supportive of using the renewable hybrid system for water pumping in Sirte, Libya.

14:00 Comparison of Microgrid Solutions for Remote Areas

Mark Markovic (BHP Billiton, Australia); Zorica Nedic (University of South Australia, Australia); Andrew Nafalski (Uni. Of South, Australia)

Often, remote locations are not within close proximity to a mains power grid. A common solution to providing electricity in remote areas is diesel generation. Historically, it is a type of power generation that is proven reliable, but not without adverse environmental impacts. Diesel generation is not capital intensive. However, it can have long term negative financial impacts as well as producing less than desirable amounts of greenhouse gases due to excessive consumptions of diesel fuel. Alternative is the use of renewable sources especially that e.g. solar energy is vastly available in the Australian outback. However, solar generation, unlike diesel requires large initial capital investment, which companies are hesitant to allocate without a proper economic analysis of alternative solutions. To alleviate these concerns, this article investigates the economy of the use of renewable sources complemented by diesel generation for a remote area pump station. It is shown that diesel powered system not only has inevitable adverse environmental impact but also contributes to the company’s financial inefficiency.

14:20 Renewable Energy Assisted Base Station Collaboration as Micro Grid

Faran Ahmed (National University of Science and Technology & Pakistan air force, Pakistan); Muhammad Naeem (Ryerson University, Canada); Muhammad Iqbal (COMSATS INSTITUTE OF IT, Pakistan); Alagan Anpalagan (Ryerson University, Canada)

In this paper, we present the case for cellular base stations enabled with renewable energy sources (RES) to be interconnected in a mini-smart grid (SG). Such an arrangement is envisaged to power the base stations (BSs) with clean sustainable energy as well as provide power to the local community. The technologies associated with RES as well as SGs have matured enough to be integrated with cellular NWs, for the benefit of both the network operator and the community. We also explore an energy cost minimization framework for a cellular network, by formulating a novel energy cooperation scheme that ensures optimal energy cooperation between green BSs. In our proposed economical and environment friendly frame work, the grid energy is minimized by optimal sharing of surplus green energy among the base stations. The intended scenario requires causal knowledge of harvested energy as well as traffic awareness by the network to workout energy demand of a BS and local grid. A realistic objective is developed, which entails energy borrowing from neighboring base stations offering their cheaper surplus energy, thereby reducing the overall energy cost of the network.

14:40 Equal Power Sharing in Islanded AC/DC Hybrid Microgrids

Abdelsalam Eajal (University of Waterloo, Canada); Ehab El-Saadany (Waterloo University, Canada); Kumaraswamy Ponnambalam (University of Waterloo, Canada)

AC/DC hybrid microgrid is a promising architecture that allows for hosting energy resources and modern loads from AC and DC types; and in turn, it reduces the number of conversion stages among other technical and economical benefits. Consequently, power distribution planners started to investigate the possibility of hybridizing the existing AC grids and designing new AC/DC hybrid clusters referred to as microgrids as a step towards the envisioned smart grid with AC/DC technologies and “plug-and-play” feature. Nevertheless, while being islanded, AC/DC hybrid microgrids bring operational challenges to the system operation such as coordination among the distributed resources in both AC/DC subgrids, control and management of the power transfer through the interlinking converters, droop control of inverter-based distributed energy resources, and accurate power sharing. This paper looks closely at the problem of active and reactive power sharing in islanded droop-based AC/DC hybrid microgrids and proposes a unified power sharing scheme that is able to simultaneously ensure precise power sharing in both AC and DC subgrids. Test results demonstrate the capability of the proposed scheme in achieving exact power sharing not only among the energy resources in proportion to their ratings but also among the interlinking converters.