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The Black Swan: The Impact of the Highly Improbable

The Art and Science of Negotiation

Continuously expanding deployments of distributed power-generation systems (DPGSs) are transforming the conventional centralized power grid into a mixed distributed electrical network. The modern power grid requires flexible energy utilization but presents challenges in the case of a high penetration degree of renewable energy, among which wind and solar photovoltaics are typical sources. The integration level of the DPGS into the grid plays a critical role in developing sustainable and resilient power systems, especially with highly intermittent renewable energy resources. To address the challenging issues and, more importantly, to leverage the energy generation, stringent demands from both utility operators and consumers have been imposed on the DPGS. Furthermore, as the core of energy conversion, numerous power electronic converters employing advanced control techniques have been developed for the DPGS to consolidate the integration. In light of the above, this paper reviews the power-conversion and control technologies used for DPGSs. The impacts of the DPGS on the distributed grid are also examined, and more importantly, strategies for enhancing the connection and protection of the DPGS are discussed.

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Distributed Power-Generation Systems and Protection

This paper focuses on the role of networked microgrids as distributed systems for enhancing the power system resilience against extreme events. Resilience is an intrinsically complex property which requires deep understanding of microgrid operation in order to respond effectively in emergency conditions. The paper first introduces the definition and offers a generic framework for analyzing the power system resilience. The notion that large power systems can achieve a higher level of resilience through the deployment of networked microgrids is discussed in detail. In particular, the management of networked microgrids for riding through extreme events is analyzed. In addition, the merits of advanced information and communication technologies (ICTs) in microgrid-based distributed systems that can support the power system resilience are presented. The paper also points out the challenges for expanding the role of distributed systems and concludes that networked microgrids in particular provide a universal solution for improving the resilience against extreme events in Smart Cities.

Networked Microgrids for Enhancing the Power System Resilience

Power systems have typically been designed to be reliable to expected, low-impact high-frequency outages. In contrast, extreme events, driven for instance by extreme weather and natural disasters, happen with low-probability, but can have a high impact. The need for power systems, possibly the most critical infrastructures in the world, to become resilient to such events is becoming compelling. However, there is still little clarity as to this relatively new concept. On these premises, this paper provides an introduction to the fundamental concepts of power systems resilience and to the use of hardening and smart operational strategies to improve it. More specifically, first the resilience trapezoid is introduced as visual tool to reflect the behavior of a power system during a catastrophic event. Building on this, the key resilience features that a power system should boast are then defined, along with a discussion on different possible hardening and smart, operational resilience enhancement strategies. Further, the so-called $\Phi \Lambda {E}\Pi $ resilience assessment framework is presented, which includes a set of resilience metrics capable of modeling and quantifying the resilience performance of a power system subject to catastrophic events. A case study application with a 29-bus test version of the Great Britain transmission network is carried out to investigate the impacts of extreme windstorms. The effects of different hardening and smart resilience enhancement strategies are also explored, thus demonstrating the practicality of the different concepts presented.

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Power Systems Resilience Assessment: Hardening and Smart Operational Enhancement Strategies

In recent years, natural disasters around the world have underscored the need for operative solutions that can improve the power grid resilience in response to low-probability high-impact incidents. The advent of microgrids (MGs) in modern power systems has introduced promising measures that can fulfil the power network resiliency requirements. This paper presents a two-stage stochastic programing approach to the optimal scheduling of a resilient MG. The impact of natural disasters on the optimal operation of MGs is modeled using a stochastic programming process. Other prevailing uncertainties associated with wind energy, electric vehicles, and real-time market prices are also taken into account. The proposed hourly scheme attempts to mitigate damaging impacts of electricity interruptions by effectively exploiting the MG capabilities. Incorporating AC network constraints in the proposed model offers a better solution to the security-constrained operation of MGs. The proposed model is linearized which offers robustness, simplicity, and computational efficiency in optimizing the MG operation. The effectiveness of proposed approach is illustrated using a large-scale MG test bed with a realistic set of data.

Microgrid Scheduling With Uncertainty: The Quest for Resilience

This paper analyzes the notion of resilience in power systems from a fundamental viewpoint and thoroughly examines its practical implications. This paper aims to describe and classify different high-impact rare (HR) events, provide a more technical definition of power system resilience, and discuss linkages between resilience and other well-established concepts, such as security and reliability. Most relevant decisions of system operators in the face of HR events involve a significant level of stress and strain. In order to make informed decisions within this context, it is crucial to have an all-inclusive picture of the state of the system. This paper provides an appropriate framework that not only characterizes the various states of the system but also derives informed decisions from a resilience-oriented perspective. It also describes and analyzes diverse resilience improvement strategies. Comprehensive models and classifications are provided to clearly capture various aspects of power system resilience.

Toward a Consensus on the Definition and Taxonomy of Power System Resilience

power grids are supposed to be fault-tolerant, but you doubt the premise when you consider daily outages in more populated parts of the world and more recent brownouts and blackouts globally. Power engineers have been pushing forward the frontiers of power systems, and the hard-fought battle against the darkness is supposed to have been won, but the struggle is by no means over. Indeed, the electricity grid today is faced more intensely with challenging issues concerning cyber and physical system security. The recent blackout in Turkey on 31 March 2015, which knocked out the transportation infrastructure in major cities, causing massive traffic jams, is a testimony to this claim. It also shut down vital services to thousands of offices for several hours, inflicting business and social losses (see Figure 1). Although widespread blackouts are regarded as low-probability events, they carry immense socioeconomic costs. In such events, the burden of responsibility often lies with extreme weather events, cascading failures, or similar low-probability, high-impact incidents. According to a report from the White House Council of Economic Advisors, severe weather is the major cause of power grid outages in the United States. Meanwhile, it is estimated that weather-related power outages cost the American economy more than US$300 billion between 2003 and 2012. The report calls for increased investment to enhance the resilience of the power grid against rising incidences of extreme weather such as thunderstorms, hurricanes, and blizzards predicted by climate models.

Front Lines Against the Darkness: Enhancing the Resilience of the Electricity Grid Through Microgrid Facilities

Deploying microgrids ( $\boldsymbol {\mu G} \text{s}$ ) with the capability of islanding and self-supply can considerably enhance power system resilience in coping with weather events. To this end, practical methods are needed in order to operationally position and manage the $\boldsymbol {\mu G}$ to optimally control its resources and minimize the risk in the face of such disturbances. This paper proposes a two-stage adaptive robust formulation for $\boldsymbol {\mu G}$ predisturbance scheduling to minimize the damaging consequences of islanding events. The approach considers different uncertainties and obtains the best day-ahead schedule for the $\boldsymbol {\mu G}$ , which is robust against realization of uncertain parameters. An appropriate decomposition strategy, called column-and-constraint generation algorithm, is adopted to efficiently solve the problem, and “budget of uncertainty” parameters are introduced to control the conservatism of the robust solution. The effectiveness of the novel framework is evaluated and discussed on a $\boldsymbol {\mu G}$ using a set of illustrative case studies. The simulations show that the framework mitigates the huge cost of load shedding at the expense of a small increase in the predisturbance preparation cost. The advantages of our model are particularly remarkable when a weather event will come through, and a significant level of uncertainty exists.

Proactive Management of Microgrids for Resiliency Enhancement: An Adaptive Robust Approach

Transportation and electricity industries are considered as major sources of greenhouse gases (GHGs) emission. Different methods have been proposed to deal with the increasing rate of the emission, such as employing plug-in electric vehicles (PEVs) and integrating renewable energy sources (RESs). However, it is important to scrutinise different scenarios of incorporating the mentioned elements to decrease the concerning emission rate while considering the economic constraints. In this study, a combined economic emission dispatch (CEED) is employed to investigate the effectiveness of using PEVs and RESs from different aspects. A sensitivity analysis is executed to survey the influence of emission and cost coefficients. Two test cases each including different scenarios are simulated to determine the efficacy of different types of integration in the proposed model. To have a more accurate and realistic survey, an extended model of the wind farm's cost function is employed in economic dispatch calculations. The particle swarm optimisation algorithm is applied to solve the CEED non-linear problem. The obtained results indicate that the integration of PEVs cannot necessarily reduce the net emission of two industries. In fact, the optimum solution should include the incorporation of PEVs along with RESs to return the desired results.

Amin Gholami

Papers

Microgrid Scheduling With Uncertainty: The Quest for Resilience

Toward a Consensus on the Definition and Taxonomy of Power System Resilience

Front Lines Against the Darkness: Enhancing the Resilience of the Electricity Grid Through Microgrid Facilities

Proactive Management of Microgrids for Resiliency Enhancement: An Adaptive Robust Approach

Environmental/economic dispatch incorporating renewable energy sources and plug-in vehicles