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A. Oulis Rousis
Electrical & Electronic Engineering, Imperial College London, 4615 London, United Kingdom of Great Britain and Northern Ireland, SW7 2AZ

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Journal article
Published: 28 April 2021 in IEEE Transactions on Power Systems
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Extreme events can cause severe power system damage. Resilience-driven operation of networked microgrids (MGs) has been heavily studied in literature. There is, though, little research considering the influence of resilience on decision making for planning. In this paper, a three-level model is suggested to solve the optimal sizing problem of networked MGs considering both resilience and cost. In the first level, a meta-heuristic technique based on an adaptive genetic algorithm (AGA) is utilized to tackle the normal sizing problem, while a time-coupled AC OPF is utilized to capture stability properties for accurate decision-making. The second and third levels are combined as a defender-attacker-defender model. In the former, the suggested AGA is utilized to generate attacking plans capturing load profile uncertainty and contingencies for load shedding maximization, while a multi-objective optimization problem is suggested for the latter to obtain a trade-off between cost and resilience. Simulations considering meshed networks and load distinction into critical and non-critical are developed to demonstrate algorithm effectiveness on capturing resilience at the planning stage and optimally sizing multiple parameters. The results indicate that higher resilience levels lead to higher investment cost, while sizing networked MGs leads to decreased investment in comparison with standalone MGs sizing.

ACS Style

Yi Wang; Anastasios Oulis-Rousis; Goran Strbac. A three-level planning model for optimal sizing of networked microgrids considering a trade-off between resilience and cost. IEEE Transactions on Power Systems 2021, PP, 1 -1.

AMA Style

Yi Wang, Anastasios Oulis-Rousis, Goran Strbac. A three-level planning model for optimal sizing of networked microgrids considering a trade-off between resilience and cost. IEEE Transactions on Power Systems. 2021; PP (99):1-1.

Chicago/Turabian Style

Yi Wang; Anastasios Oulis-Rousis; Goran Strbac. 2021. "A three-level planning model for optimal sizing of networked microgrids considering a trade-off between resilience and cost." IEEE Transactions on Power Systems PP, no. 99: 1-1.

Journal article
Published: 20 March 2021 in Sustainable Energy, Grids and Networks
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High-impact and low-probability (HILP) events can cause severe damage to power systems. Networked microgrids (MGs) with distributed generation resources provide a viable solution for the resilience enhancement of power systems. However, most literature utilizes centralized control methods based on energy management systems to model networked MGs and employs static storage units to enhance resilience, which are both unrealistic. In this paper, a hierarchical control approach based on detailed AC OPF algorithm is developed to capture technical constraints relating to voltage, angle and power loss as well as obtaining accurate solutions of power exchange between MGs, while the routing of electric vehicles (EVs) is incorporated into the model to reduce load shedding during extreme events. Uncertainties relating to load profiles and renewable energy sources are captured via stochastic programming. The impacts of limited generation resources and different levels of contingencies (including multiple line faults) are captured in the model to mimic a realistic scenario and verify the effectiveness of the proposed resilience enhancement strategy. Appropriate sensitivity analyses are suggested to investigate the influence of uncertain event occurrence time, tie-line capacity and EV scheduling horizon.

ACS Style

Y. Wang; A. Oulis Rousis; G. Strbac. A resilience enhancement strategy for networked microgrids incorporating electricity and transport and utilizing a stochastic hierarchical control approach. Sustainable Energy, Grids and Networks 2021, 26, 100464 .

AMA Style

Y. Wang, A. Oulis Rousis, G. Strbac. A resilience enhancement strategy for networked microgrids incorporating electricity and transport and utilizing a stochastic hierarchical control approach. Sustainable Energy, Grids and Networks. 2021; 26 ():100464.

Chicago/Turabian Style

Y. Wang; A. Oulis Rousis; G. Strbac. 2021. "A resilience enhancement strategy for networked microgrids incorporating electricity and transport and utilizing a stochastic hierarchical control approach." Sustainable Energy, Grids and Networks 26, no. : 100464.

Journal article
Published: 15 September 2020 in IEEE Transactions on Sustainable Energy
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The electrical energy generated from renewable energy resources connected to transmission and distribution systems and the displacement of synchronous generators continues to grow. This presages a paradigm-shift away from the traditional provision of ancillary services, essential to ensure a robust system, from transmission-connected synchronous generators towards provision from synchronous and non-synchronous generation (including distribution-connected resources). Given that the available resources at the disposal of system operators are continuously increasing, the flexibility for operating the network can be enlarged. In this context, this paper introduces a dedicated voltage ancillary services strategy for provision of reactive power. A main feature of the proposed strategy is that it is technology-neutral, unlike existing ones that are focused on synchronous generators. The system need for voltage stability is placed at the core of this strategy, which is translated into a requirement for reactive power provision. The proposed strategy achieves, through the combined utilization of distributed generation and traditional resources, to defer the investments in reactive compensating equipment. Dynamic and transient studies are conducted to demonstrate the technical benefits of the strategy, while its practical feasibility is also validated through hardware-in-the-loop testing.

ACS Style

Anastasios Oulis Rousis; Dimitrios Tzelepis; Yousef Pipelzadeh; Goran Strbac; Campbell David Booth; Timothy C. Green. Provision of Voltage Ancillary Services Through Enhanced TSO-DSO Interaction and Aggregated Distributed Energy Resources. IEEE Transactions on Sustainable Energy 2020, 12, 897 -908.

AMA Style

Anastasios Oulis Rousis, Dimitrios Tzelepis, Yousef Pipelzadeh, Goran Strbac, Campbell David Booth, Timothy C. Green. Provision of Voltage Ancillary Services Through Enhanced TSO-DSO Interaction and Aggregated Distributed Energy Resources. IEEE Transactions on Sustainable Energy. 2020; 12 (2):897-908.

Chicago/Turabian Style

Anastasios Oulis Rousis; Dimitrios Tzelepis; Yousef Pipelzadeh; Goran Strbac; Campbell David Booth; Timothy C. Green. 2020. "Provision of Voltage Ancillary Services Through Enhanced TSO-DSO Interaction and Aggregated Distributed Energy Resources." IEEE Transactions on Sustainable Energy 12, no. 2: 897-908.

Journal article
Published: 03 August 2020 in IEEE Access
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High-impact and low-probability extreme events can cause severe damage to power systems, especially for distribution systems. Microgrids (MGs) with distributed generation resources provide a viable solution for local load survivability via islanding schemes during extreme events. Recently, much research has focused on resilience-driven modeling and operations of MGs. In this paper, a resilience-driven operational model incorporating two operational modes (grid-connected and islanded) and detailed technical characteristics, such as voltage-related operational constraints, is developed for the resilience enhancement of a hybrid AC/DC MG. A detailed AC optimal power flow (OPF) algorithm is employed to model operational constraints and the power exchange between AC and DC subgrids. Preventive power importing is utilized for better preparedness before extreme events and demand response is employed to reduce load shedding during emergency mode. Existing literature on resilience assessment is reviewed and a modified multi-phase curve is proposed to fully represent the influence of limited generation resources and uncertain event duration on resilience. Extensive case studies capturing the distinction of critical loads and non-critical loads and two types of contingencies (multiple line faults and interrupted connection between AC subgrid and DC subgrid) are conducted to demonstrate the effectiveness of the proposed resilience strategy on protecting critical loads and reducing total load shedding. Particularly, a sensitivity analysis considering different event occurrence time has been simulated to capture, in a simple but rather effective way, the effect of the uncertainty surrounding event occurrence.

ACS Style

Yi Wang; Anastasios Oulis Rousis; Goran Strbac. Resilience-Driven Modeling, Operation and Assessment for a Hybrid AC/DC Microgrid. IEEE Access 2020, 8, 139756 -139770.

AMA Style

Yi Wang, Anastasios Oulis Rousis, Goran Strbac. Resilience-Driven Modeling, Operation and Assessment for a Hybrid AC/DC Microgrid. IEEE Access. 2020; 8 ():139756-139770.

Chicago/Turabian Style

Yi Wang; Anastasios Oulis Rousis; Goran Strbac. 2020. "Resilience-Driven Modeling, Operation and Assessment for a Hybrid AC/DC Microgrid." IEEE Access 8, no. : 139756-139770.

Journal article
Published: 20 June 2019 in IEEE Transactions on Power Systems
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This paper focuses on developing an appropriate combinatorial optimization technique for solving the optimal sizing problem of hybrid AC/DC microgrids. A novel two-stage iterative approach is proposed. In the first stage, a metaheuristic technique based on a tailor-made genetic algorithm is used to tackle the optimal sizing problem, while, in the second, a non-linear solver is deployed to solve the operational problem subject to the obtained design/investment decisions. The proposed approach, being able to capture technical characteristics such as voltage and frequency through a detailed power flow algorithm, provides accurate solutions and therefore can address operational challenges of microgrids. Its capability to additionally capture contingencies ensures that the proposed sizing solutions are suitable both during normal operation and transient states. Finally, the genetic algorithm provides convergence of the model with relative computational simplicity. The proposed model is applied to a generalizable microgrid comprising of AC and DC generators and loads, as well as various types of storage technologies in order to demonstrate the benefits. The load and natural resources data correspond to real data.

ACS Style

Anastasios Oulis Rousis; Ioannis Konstantelos; Goran Strbac. A Planning Model for a Hybrid AC–DC Microgrid Using a Novel GA/AC OPF Algorithm. IEEE Transactions on Power Systems 2019, 35, 227 -237.

AMA Style

Anastasios Oulis Rousis, Ioannis Konstantelos, Goran Strbac. A Planning Model for a Hybrid AC–DC Microgrid Using a Novel GA/AC OPF Algorithm. IEEE Transactions on Power Systems. 2019; 35 (1):227-237.

Chicago/Turabian Style

Anastasios Oulis Rousis; Ioannis Konstantelos; Goran Strbac. 2019. "A Planning Model for a Hybrid AC–DC Microgrid Using a Novel GA/AC OPF Algorithm." IEEE Transactions on Power Systems 35, no. 1: 227-237.

Journal article
Published: 01 February 2019 in Energy Procedia
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This paper focuses on developing an appropriate optimization technique for solving the optimal operation problem of hybrid AC/DC microgrids. A non-linear mathematical formulation is deployed to solve the problem subject to the exhaustive set of constraints and equations pertaining to the operation of AC and DC networks. The proposed approach, being able to capture technical characteristics, such as voltage and frequency, through the detailed power flow algorithm, provides accurate solutions and therefore can address operational challenges of MGs. The approach is applied to a highly-generalizable microgrid comprising of AC and DC generators and loads, as well as storage technologies in order to demonstrate the benefits. The simulation results demonstrate how voltage and frequency are effectively captured across the whole network via the utilised formulation and the power flow through the interlinking converter is associated with frequency (i.e. 49-51 Hz) and voltage variation (i.e. 0.95-1.05 p.u.).

ACS Style

A. Oulis Rousis; I. Konstantelos; P. Fatouros; G. Strbac. An AC OPF with voltage – frequency coupling constraints for addressing operational challenges of AC/DC microgrids. Energy Procedia 2019, 159, 261 -266.

AMA Style

A. Oulis Rousis, I. Konstantelos, P. Fatouros, G. Strbac. An AC OPF with voltage – frequency coupling constraints for addressing operational challenges of AC/DC microgrids. Energy Procedia. 2019; 159 ():261-266.

Chicago/Turabian Style

A. Oulis Rousis; I. Konstantelos; P. Fatouros; G. Strbac. 2019. "An AC OPF with voltage – frequency coupling constraints for addressing operational challenges of AC/DC microgrids." Energy Procedia 159, no. : 261-266.

Journal article
Published: 14 August 2018 in Inventions
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This paper is concerned with the design of an autonomous hybrid alternating current/direct current (AC/DC) microgrid for a community system, located on an island without the possibility of grid connection. It is comprised of photovoltaic (PV) arrays and a diesel generator, AC loads, and battery energy storage devices for ensuring uninterruptible power supply during prolonged periods of low sunshine. A multi-objective, non-derivative optimisation is considered in this residential application; the primary objective is the system cost minimisation, while it is also required that no load shedding is allowed. Additionally, the CO2 emissions are calculated to demonstrate the environmental benefit the proposed system offers. The commercial software, HOMER Pro, is utilised to identify the least-cost design among hundreds of options and simultaneously satisfy the secondary objective. A sensitivity analysis is also performed to evaluate design robustness against the uncertainty pertaining to fuel prices and PV generation. Finally, an assessment of the capabilities of the utilised optimisation platform is conducted, and a theoretical discussion sheds some light on the proposal for an enhanced design tool addressing the identified issues.

ACS Style

Anastasios Oulis Rousis; Dimitrios Tzelepis; Ioannis Konstantelos; Campbell Booth; Goran Strbac. Design of a Hybrid AC/DC Microgrid Using HOMER Pro: Case Study on an Islanded Residential Application. Inventions 2018, 3, 55 .

AMA Style

Anastasios Oulis Rousis, Dimitrios Tzelepis, Ioannis Konstantelos, Campbell Booth, Goran Strbac. Design of a Hybrid AC/DC Microgrid Using HOMER Pro: Case Study on an Islanded Residential Application. Inventions. 2018; 3 (3):55.

Chicago/Turabian Style

Anastasios Oulis Rousis; Dimitrios Tzelepis; Ioannis Konstantelos; Campbell Booth; Goran Strbac. 2018. "Design of a Hybrid AC/DC Microgrid Using HOMER Pro: Case Study on an Islanded Residential Application." Inventions 3, no. 3: 55.