Contingency States Research Articles

A Modified Rao-2 Algorithm for Optimal Power Flow Incorporating Renewable Energy Sources

In this paper, a modified Rao-2 (MRao-2) algorithm is proposed to solve the problem of optimal power flow (OPF) in a power system incorporating renewable energy sources (RES). Quasi-oppositional and Levy flight methods are used to improve the performance of the Rao algorithm. To demonstrate effectiveness of the MRao-2 technique, it is tested on two standard test systems: an IEEE 30-bus system and an IEEE 118-bus system. The objective function of the OPF is the minimization of fuel cost in five scenarios. The IEEE 30-bus system reflects fuel cost minimization in three scenarios (without RES, with RES, and with RES under contingency state), while the IEEE 118-bus system reflects fuel cost minimization in two scenarios (without RES and with RES). The achieved results of various scenarios using the suggested MRao-2 technique are compared with those obtained using five recent techniques: Atom Search Optimization (ASO), Turbulent Flow of Water-based Optimization (TFWO), Marine Predators Algorithm (MPA), Rao-1, Rao-3 algorithms, as well as the conventional Rao-2 algorithm. Those comparisons confirm the superiority of the MRao-2 technique over those other algorithms in solving the OPF problem.

An exact and scalable problem decomposition for security-constrained optimal power flow

In this paper, we present decomposition techniques for solving large-scale instances of the security-constrained optimal power flow (SCOPF) problem with primary response. Specifically, under each contingency state, we require that the nodal demands are met and that the synchronized units generating below their limits follow a linear model for primary response. The resulting formulation is a mixed-integer linear program since the primary response model introduces disjunctions to the SCOPF problem. Unfortunately, exact methods relying on traditional Benders decomposition do not scale well. As an alternative, we propose a decomposition scheme based on the column-and-constraint-generation algorithm where we iteratively add disjunctions and cuts. We provide procedures for preprocessing dedicated cuts and for numerically determining the post-contingency responses based on the master problem solutions. We also discuss heuristics to generate high-quality primal solutions and upper bounds for the method. Finally, we demonstrate the efficiency of the proposed method on large-scale systems.

Reliability Assessment of Power Systems with High Renewable Energy Penetration Using Shadow Price and Impact Increment Methods

With the ever-increasing penetration of renewable resources, more complexities and uncertainties are introduced in power system reliability assessment. This entails an enormous number of contingency states to represent the characteristics of renewable energy. As a result, the unbearable computation burden is the main challenge toward the efficiency of the state enumeration (SE) method. To address that, this paper proposes an improved reliability evaluation approach that can not only increase the accuracy but also accelerate the analysis. In detail, the impact increment method is first employed to decrease the proportion of higher-order contingency states, leading to accuracy improvement. Then, the shadow price is used to solve the optimal power flow (OPF) problem in a faster manner. This shadow price (SP) method allows us to obtain the optimal load curtailment directly from linear functions rather than the time-consuming OPF algorithms. In addition, one hundred percent criterion is used to match shadow-price-based linear functions with system states. Case studies are performed on the RTS-79 system and IEEE 118-bus system, in which test scenarios include loads, photovoltaics (PV), and wind turbines (WT). Results indicate that the proposed method can significantly ease the computation burden and outperform traditional reliability assessment methods in terms of both computing time and accuracy.

COVID-19 pandemic in an Italian obstetric department: sharing our experience.

Background and aim of the work:The outbreak of the novel coronavirus (or SARS-CoV 2) has struck the healthcare system worldwide. Within few weeks hospitals had to reorganize their internal logistics and structure covering any level of care, from the Emergency Room to medical Departments.Methods:Due to the state of medical emergency, the Gynecology and Obstetrics Unit of the University Hospital in Udine developed new protocols for the usual standard of care, ensuring a safe environment for both healthcare providers and patients.Results:By a continuous update of scientific evidence, the Department was able to increase capacity as well as maintain flexibility when an unexpected high number of admissions was required. 40 COVID -19 positive patients were admitted to our Department between March and December 2020, none of them had complications and no case of cross infection between patients and medical staff were registered.Conclusion:We aimed to share our experience, which provided a notable lesson about what to expect and how to prepare a high-risk pregnancy referral center in response to a pandemic. (www.actabiomedica.it)

A Lagrange Multiplier Based State Enumeration Reliability Assessment for Power Systems With Multiple Types of Loads and Renewable Generations

With the integration of multiple types of loads and renewable generations, the number of system states significantly grows. As a result, running optimal power flow (OPF) to analyze a myriad of system states is challenging and this seriously restricts the efficiency of the state enumeration method. To address that, this paper proposes a Lagrange Multiplier based State Enumeration (LMSE) approach to accelerate the analysis without loss of accuracy. The core idea is to directly obtain the optimal load shedding of contingency states by Lagrange multiplier-based functions, rather than the time-consuming OPF algorithms. This approach can also be conveniently integrated with the impact-increment method and the clustering technique for further efficiency enhancement. Case studies are performed on the RTS-79 and IEEE 118-bus systems considering multiple types of loads, photovoltaics (PVs), and wind turbines (WTs). Results indicate that the proposed method can significantly reduce the computing time without compromising the calculation accuracy.

Reliability assessment of composite power systems containing sea wave slot‐coned generators

The generated power of the Sea-wave slot-coned generator (SSG), as one of the high capacity wave energy converters, is dependent on the period and height of the waves. The generated power of this energy-converter changes due to the variation in these parameters. Thus, different aspects of the power systems may be affected that must be investigated by increasing the share of these converters for electricity production in the power-systems. In this paper reliability assessment of composite power-systems containing large-scale SSG is performed. The Xie and Beni (XB) index is calculated for obtaining the optimum number of states in the reliability model of the SSG and fuzzy c-means clustering technique is proposed for reducing the number of states of the model. The contingency analysis method is proposed for calculating the reliability indices of the composite power-system incorporating large-scale SSG. DC load-flow method, which considers line capacity, is used to perform load-flow in the composite power-system including generation and transmission networks. In the proposed technique, a load-shedding program with the goal of minimizing the value of lost load is solved using of the linear programming method based on the interior-point-approach for contingency states leading to the load curtailment.

Covid-19 y animales, ¿una oportunidad para la abolición de la esclavitud especista?

La pandemia por SARS-COV-2, ha exigido al animal humano tomar acciones de salvaguarda, inclusive, lo ha llevado a reflexionar con mayor atención sobre su relación con los demás animales. Frente al panorama actual de contingencia, el ámbito jurídico debe prepararse para ampliar consideraciones de protección jurídica e iniciar el camino de la abolición de la esclavitud especista.

Load control mechanism for operation of microgrids in contingency state

This paper proposes a load control module based on the consumers' vulnerability indices to improve the ability of radial microgrid (MG) to deal with line contingencies. This consumer switching module (CSM) increases the operational flexibility and is suitable for the radial MGs, where, a sudden line outage restricts access to the energy resources and deviates the system frequency in the created island. To cope with this condition, CSM can instantly disconnect some of the loads and reconnects them in an appropriate time sequence, considering loads' vulnerabilities. To include the CSM in the short-term operation of MG, with the lowest complexity, a simple four-stage structure is used. At first, the capability of CSM is determined in different islands related to potential line events. Then, the approximate cost function of CSM is applied to the short-term MG operation which is hour-ahead scheduling (HAS) including both the normal and the contingency state operation. Eventually, the determined optimal CSM participation level in each island is allocated to the consumers based on their exact offered price to calculate the load switching sequence. To evaluate the performance of the proposed scheduling manner, the 13-bus and 123-bus IEEE test systems are precisely analyzed considering different simulation scenarios.

Role of Vitamin D in Boosting Immunity against COVID-19

The world is now in the state of contingency and is facing one common enemy, COVID 19. Front developed countries to the developing and under developed countries, all are fighting against this common enemy which is a virus that is 0.125 microns ( 1 25 nm) with the size ranging from 0.06 to 0.14 microns. The world is now looking for a vaccine to prevent the infection, while the need of the hour is to boost the immunity of individuals against the disease through readily available nutrients. With the increase in incidence of the COVID-19 pandemic, scientists to common public have started to ponder the ways out of it, while boosting the immunity has become the only resolve as no vaccine has been invented until date. It is obvious that there is a correlation between nutrition and immune system; it is a common understanding that people who are well-nourished have a better immunity compared to poorly nourished people with a weak immunity. It is to be noted that people suffering from chronic diseases and elderly will have a weak immunity and are more prone to any disease let alone COVID-19. Though general immunity can be boosted through vitamin C, zinc and other micronutrients, vitamin D is required to boost overall immunity and also strengthen lungs. This review aims at laying emphasis on the need of vitamin D in strengthening immunity against the deadly common enemy COVlD- 19.

Noise as Information: Finance Economics as Second-Order Observation

In noise we hear the possibility of a signal, indeed different signals, and in the multiplicity of signals we hear noise. With variation and selection comes dynamic evolution, a contingent state, one that could be otherwise. The term ‘polemogenous’ (from the French, polémogène) means that which generates polemics. And polemics are creative. If everyone, every system, were to reason in the same way, there would be silence. Every remark would be redundant, having no informational value. Thus noise is not bad. The essence of finance economics, like all that is social in nature, is a forming of meaning. Whatever cannot be formed meaningfully is not available to the system. This unavailability, as ‘noise’, is the dynamic difference (noise/information) that scintillates the system. Information, like morality, is polemogenous – it stirs contention. Without noise and the possibility of its conversion to information there would be no opportunities to exploit. This paper applies a systems theoretical understanding of observation to conceive of finance economics as the economy’s means of observing its noise and capitalizing on that polemic. Niklas Luhmann’s method is utilized to explicate some ideas on noise by financial economist Fischer Black, who suggests the incomprehensible is computable. This is finance. The fact that logical grounds, absolute deductions, and clear calculations are claimed to be rare in finance is no barrier to understanding it. Rather, this polyphonic and polemogenous information-selection is the ‘ground’ of finance, not as totalizing logic, but as different difference-production for the sake of deriving economic opportunity.

Impact of Down Spinning Reserve on Operation Reliability of Power Systems

The development of renewable energy and the increasing peak-valley difference of load demand lead to an increasing requirement of spinning reserve (SR). However, the traditional operation reliability analysis of power system mainly focuses on the up SR and neglects the down SR. Therefore, the operation reliability of power system considering the impacts of down SR is investigated in this paper. Firstly, the constraints of down SR are incorporated into the day-ahead unit commitment (UC) model to obtain the generation scheduling and reserve allocation of power systems. Based on the dispatch results of UC model, the re-dispatched energy and load interruption can be determined using optimal power flow (OPF) model in the real-time operation in various contingency states. Operation reliability indices are calculated based on the load curtailment to represent the reliability performances of power systems. The proposed approaches are validated using the modified IEEE reliability test system. Case studies demonstrate that down SR can improve the operation reliability of power systems.

The Use of Black-Box Optimization Method for Determination of the Bus Connection Capacity in Electric Power Grid

One of the main tasks of the Power System Operators is to ensure a proper, safe, and trouble-free operation and development of power grids. Growth of power system is inseparably linked to a connection of both renewable and classical new energy sources. For network operators and potential investors, it is essential to know the place and volume of generation capacity that can be connected to the grid. A publication of such data is currently a legal obligation for many operators. This paper proposes a method of determining the bus connection capacity in power grid of any type with the use of black-box optimization. Calculations and analyses were performed with a full, nonlinear model of the analyzed network. Obtained results show the effectiveness of this method for both single and multiple nodes in any configuration. All the constraints relevant for the proper and safe system operation, such as bus voltages, line loads, and short-circuit currents, both in a steady-state and (n-1) contingency states, are taken into consideration. Calculations confirmed the good convergence and repeatability of the method for all three tested computational algorithms. This has also confirmed the possibility of use of open source software to extend the functionality of Siemens PSS®E commercial power system calculation software.

The grammaticalisation of a copula in vernacular Arabic

It is standardly assumed that Arabic copula constructions with present tense interpretation involve either a null copula or a pronominal copula. This paper provides evidence that some Arabic vernaculars are developing a three-way split, with an additional copula form occurring in some predicational copula clauses. This form has grammaticalised out of the active participle form of the posture verb meaning ‘sit’. While at different stages of development in different varieties of Arabic, this emergent copula shows the characteristics of a locative (temporary and/or permanent, depending on the variety) or contingent state (stage-level) copula, standing in contrast with the use of a null copula strategy, which marks characterising/defining individual-level properties. We propose a grammaticalisation trajectory for this copula in the Arabic varieties based on the comparative patterns of variation across those dialects, showing that the trajectory postulated for other, typologically distinct languages is also applicable to Arabic and hence providing further support for it. We suggest that there is also evidence of a distinct but related trajectory in some varieties which have developed a semantically bleached lexical existential predicate from this same form. We provide further evidence of the importance of the temporary/permanent split in the copula systems of Arabic arguing that the developing split copula system based on the active participle of the ‘sit’ verb is in alignment with the development of two other parallel split copula systems in other geographically diverse Arabic varieties, which use different bases/strategies for grammaticalisation.

Robots and AR: towards a platform economy for construction

Platform economies like Uber and AirBnB have emerged quickly to dominate and radically reconfiguring social, geographic and organisational structures of existing economic systems; putting markets into a state of contingency and flux. What is a platform economy for construction? This paper reports on research investigating the implementation and combination of new technology, made possible by through a ‘platform’ approach to disrupt design and making processes and offer insight into potential futures. This project explores automated robotic construction, automatic recognition of building components and Augmented Reality overlay of additional data. The paper reviews existing literature to explore similarities and differences between construction and other sectors being disrupted by platforms. The research methodology develops a digital software platform to investigate how much of the design, fabrication and assembly of a ‘digital igloo’ can be automated. The igloo itself is a simple structural form intended to showcase composite panels. Results reveal construction is organizationally strikingly similar to sectors currently being disrupted. They also show the surprising extent to which design, fabrication and assembly can be contained within a digital platform. The biggest challenge was perhaps to do with tolerance, specifically when and where there is a focus on precision. Conclusions suggest the complexity of construction is likely to prevent an immediate and complete shift to a platform economy. It is more likely in the short term that contained and discrete aspects of construction, such as transport or equipment, might be suited to adoption.

Nodal Reliability Evaluation for a VSC-MTDC-Based Hybrid AC/DC Power System

The utilization of voltage-source converter-based multi-terminal HVDC (VSC-MTDC) technology has been envisaged as a cost-effective solution to transmit bulk renewables from multiple sending ends to receiving-end AC systems. However, with complex configurations and various types of components, the reliability evaluation of a VSC-MTDC system is more complicated than that of a conventional HVDC system. In addition, due to stochastic failures and complex operating modes, the application of a VSC-MTDC system can have a significant influence on the reliability of hybrid AC/DC power systems. This paper presents a new technique for evaluating the nodal reliability of a hybrid AC/DC power system based on the VSC-MTDC system. The proposed technique is incorporated within a multi-state model for the VSC-MTDC system. Then, an optimization model for contingency management of a hybrid AC/DC power system is formulated. The model is established based on the optimal power flow technique for a VSC-MTDC based hybrid AC/DC power system. The objective of the model is to minimize the total system cost when determining the load curtailment and generation re-dispatch results for each contingency state. Nodal reliability indices for hybrid AC/DC power systems are proposed to evaluate the reliability performance of customers at each node. The effectiveness of the proposed methods is validated using a modified IEEE reliability test system.

A dynamic objective function for communication-based relaying: Increasing the controllability of relays settings considering N-1 contingencies

Considering different configurations of a protected network in relays coordination offers higher reliability, security, and sustainability. However, overcurrent relaying in N-1 contingency states stands as a complicated problem especially in interconnected sub-transmissions systems with distance relays. To overcome this challenge, the current paper proposes a coordination scheme in which dual setting directional overcurrent relays (D-DOCRs) and low bandwidth communication links are jointly deployed instead of conventional DOCRs. By doing so, more flexibility and extensibility is provided in the coordination process. Moreover, in order to direct the relays settings toward optimal solutions, a new dynamic objective function is devised. This approach strengthens the controllability of relay settings in different conditions by pulling the variables towards the feasible region. The proposed formulation considers both standard and non-standard relay characteristics and demonstrates a nonlinear programming fashion which is solved by chaotic particle swarm optimization algorithm. Results approve that D-DOCRs in conjunction with distance relays can successfully maintain a proper coordination in N-1 contingency states, supported by the proposed dynamic approach.

Risk-based optimal power portfolio methodology for generation companies considering cross-region generation right trade

The generation right trades (GRTs) are of great significance for the improvement of unit utilization hours and reduction of carbon emission, which plays an important role in the cross-regional electricity transactions. In order to hedge the risk in spot markets and ensure the incomes, it is crucial for generation companies (Gencos) to determine the optimal GRT scheme at their risk preferences. In this paper, a power portfolio optimization methodology is proposed considering the bidding behaviours in spot markets, independent system operator (ISO) centralized dispatching, and the cross-region GRTs. Specifically, various risks for Gencos are modelled including spot price fluctuation and system component failures. Then, a bi-level optimal portfolio (BLOP) model is established where the Gencos maximize their total incomes with subject to the ISOs which minimize the local dispatching costs simultaneously. The BLOP model is transformed into a solvable single-level mathematical program with equilibrium constraints (MPCE) through the Karush-Kuhn-Tucker (KKT) conditions. The numerical results on a realistic Chinese testing system illustrate the effect of GRTs for income assurance of Gencos and the necessity to consider the stochastic contingencies in portfolio decisions. Specifically, it is a preferred option for Gencos to exploit approximately 77% of spot power to GRT at the normal state, which can increase the total income by 266.21%. At contingency states, the optimal GRT ratios are 70–80%, the corresponding income grows nearly twice more than pure spot trades.

Optimal Placement of FACTs Devices in Iraqi National Super Grid System (INSGS) Using HLSI

Many of the power cuts in the electricity system in the last decade indicate that there is much work to be done to address the voltage instability and subsequent collapse. This study presents a method to find and select the optimum location of FACTs device using the hybrid line stability index (HLSI) that is appropriate for the prediction voltage collapse in power system networks. Such the HLSI was obtained by deriving expressions basics equivalent Line Stability Index (Lmn), and Fast Voltage Stability Index (FVSI) and mix theirs through a switch logic based on the voltage angle difference Where indicate the nearness voltage collapse. The HLSI has tested in Iraqi National Super Grid System (INSGS) it gives the same results as the other indicators (Lmn & FVSI). For the base state, INSGS was found to be stable with all the three indicators have approximately equal values least than 1 for all lines. The contingency state detects that ranks of bus 24 the weakest bus in the system with the lower maximum allowable reactive load of (490.371 Mvar) and the line critical concerning bus 24, the line connecting bus 20 to bus 24. The values the three indicators, Lmn, FVSI, and HSLI, approximately equal, increasing the accuracy of HLSI.

A new modeling and solution method for optimal energy flow in electricity‐gas integrated energy system

With the increasing interdependency of electricity and gas, it is necessary to simultaneously investigate electric power system and natural gas system from the perspective of an electricity-gas integrated energy system (EGIES). As an extension and integration of both optimal power flow (OPF) and optimal gas flow (OGF), optimal energy flow (OEF) is regarded as the cornerstone of the EGIES and lays an essential foundation for further research on the EGIES's operation and analysis considering stochastic conditions and contingency states. The objective of this paper is to develop a generalized mathematical model and a universally applicable simulation tool for the OEF problem. First, natural gas system is modeled in a way similar to electric power system according to electricity-gas analogy analysis, where gas admittance, gas nodal admittance matrix, and the nodal equation of gas flow conservation are derived. Then, a generalized accurate OEF model is formulated by simultaneously integrating the OPF model and the OGF model as well as their coupling constraints in a unified modeling framework. Furthermore, an available hybrid optimization approach consisting of whale optimization algorithm, MATPOWER, hydraulic calculation iterative program, and nonstationary penalty function method is put forward to solve the OEF problem. The accuracy, feasibility, and applicability of the proposed modeling and solution method is finally demonstrated by analyzing Belgian 20-node gas system combined with IEEE 30-bus test system.

Pranks, Tropes and Raspberries: The Dialogic Demeanour of Satire’s Creative Horizon

Abstract This essay starts off with a modern-day court jester (Nobel laureate Dario Fo) praising a Pope (Albino Luciani, who became John Paul I). Fo presents us with an historic moment: Luciani scandalises his Church by calling God “Mother.” With utmost seriousness, Fo appreciates the Pope’s kindness and warmth by which the artist perceives a way of scandalising the world out of complacency. In their idealised and situated presentations of the world, the sacred and the profane return the necessary to the contingent (and vice-versa) as moments of equal attention and distraction. Likewise, irony and satire mark our situated sense of the ideal by an inability to unlearn the certainties by which we are urged to construct our world. This is done by first presenting a situated pedagogical context that refuses to provide solutions presumed on measurement, certainty or finality. Secondly this begins to lay claim to the political, aesthetic and moral values that are gained through art’s ironic disposition. Thirdly, through our contingent states of being we begin to understand how education is culturally conditioned and why we need to shift it to another gear – that of unlearning through a weak pedagogy. An atheist, Fo suggests that thanks to Pope Luciani, we now could endear to the Holy Spirit as a spirito ridens, a spirit that laughs. Here one finds a kenotic sense that gives us a glimpse in how an ironic disposition owes its strength and effectiveness to a weak pedagogy. By dint of such weakness, the jester’s pedagogical disposition becomes a form of resistance, exiting the Court in order to be with the people and consequently transformed by the people.