The problem of distributing gas through a network of pipelines is formulated as a cost minimization subject to nonlinear flow-pressure relations, material balances, and pressure bounds. The solution method is based on piecewise linear approximations of the nonlinear flow-pressure relations. The approximated problem is solved by an extension of the Simplex method. The solution method is tested on real-world data and compared with alternative solution methods.

The gas transmission problem solved by an extension of the simplex algorithm

We give a complete characterization of the analytic and Darbouxian first integrals of the Rikitake system, which serves as a model for the reversal of polarity of the Earth's electromagnetic field. Our approach uses the Darboux theory of integrability.

Rikitake system: analytic and Darbouxian integrals

A review of regional energy internet in smart city from the perspective of energy community

We study large time behavior of the solutions to the initial value problem for the generalized Burgers equation. It is known that the solution tends to a self-similar solution to the Burgers equation at the rate $t^{-1} \log t$ in $L^{\infty}$ as $t \to \infty$. The aim of this paper is to show that the rate is optimal under suitable assumptions and to obtain the second asymptotic profile of large time behavior of the solutions.

/pdf/large-time-behavior-of-solutions-to-the-generalized-burgers-mq6m521a86.pdf

Large time behavior of solutions to the generalized Burgers equations

A two-level ANN-based method using synchronized measurements to locate high-impedance fault in distribution systems

Gas and electricity transmission systems are increasingly interconnected, and an attack on certain assets can cause serious energy supply disruptions, as stated in recommendation (EU) 2019/553 on cybersecurity in the energy sector, recently approved by the European Commission. This study aims to assess the vulnerability of coupled natural gas and electricity infrastructures and proposes a method based on graph theory that incorporates the effects of interdependencies between networks. This study is built in a joint framework, where two different attack strategies are applied to the integrated systems: (1) disruptions to facilities with most links and (2) disruptions to the most important facilities in terms of flow. The vulnerability is measured after each network attack by quantifying the unmet load (UL) through a power flow analysis and calculating the topological damage of the systems with the geodesic vulnerability ( v ¯ ) index. The proposed simulation framework is applied to a case study that consists of the IEEE 118-bus test system and a 25-node high-pressure natural gas network, where both are coupled through seven gas-fired power plants (GFPPs) and three electric compressors (ECs). The methodology is useful for estimating vulnerability in both systems in a coupled manner, studying the propagation of interdependencies in the two networks and showing the applicability of the v ¯ index as a substitute for the UL index.

/pdf/assessing-the-criticality-of-interdependent-power-and-gas-5748f6e2vq.pdf

Assessing the criticality of interdependent power and gas systems using complex networks and load flow techniques

We consider the Cauchy problem for the Korteweg-de Vries-Burgers equation. Global existence and smoothing effect for the Cauchy problem to the Kortewegde Vries-Burgers equation was proved previously for the case of large initial data. Recently the first term of the large time asymptotics was obta ined without restriction on the size of the initial data. The aim of the present paper is to obtain the second term of the large time asymptotic behavior of solutions to the Cauchy problem for the Korteweg-de Vries-Burgers equation in the case of the initial data of arbitrary size.

/pdf/second-term-of-asymptotics-for-kdvb-equation-with-large-14kapwke94.pdf

Second term of asymptotics for KdVB equation with large initial data

Most of the distribution networks may contain reactive power sources such as distributed generators with reactive support, static VARs compensators or even switching capacitors. In this sense, it is necessary to have an appropriate and convenient model for controlled-voltage (PV) nodes to be applied in power flow distribution networks. On the other hand, the conventional power flow analysis has been an important tool for all power systems engineers. The nonlinear methods based on the Newton- Raphson method and its decoupled forms and the Gauss-Seidel with Ybus factorized method have been popular to nowadays. However, these methods have presented some convergence problems when are applied to distribution networks analysis. The reasons are the inherent characteristics of distribution networks, such as high r/x ratios, very low branch impedances, radial feeder configurations, among others. In this sense, the techniques based on Backward/Forward Sweep (BFS) methods for power flows have been widely applied in distribution systems. However, as above mentioned for controlled-voltage (PV) nodes some challenges in BFS power flow algorithms are presented, some authors have proposed hybrid methods, iterative methods, sensitivities matrix- based methods, among others. Unfortunately, those methods usually require complex formulations and long execution times. In this paper a new approach and easily controlled-voltage (PV) formulation joint with a simple power flows methodology, called LRSV method, is presented. The results show that this no-complex methodology permits to obtain better execution times, responses in a better way for different load, generation and configurations and some tests cases to demonstrate the effectiveness of the proposed methodology.

A New Approach for PV Nodes Using an Efficient Backward/Forward Sweep Power Flow Technique

We study nonlinear Landau–Ginzburg-type equations on the half-line in the critical case where β ∈ C, ρ > 2. The linear operator K is a pseudodifferential operator defined by the inverse Laplace transform with dissipative symbol K(p) = αpρ, M = [1/2ρ]. The aim of this paper is to prove the global existence of solutions to the initial–boundary-value problem and to find the main term of the asymptotic representation of solutions in the critical case, when the time decay of the nonlinearity has the same rate as that of the linear part of the equation.

Landau–Ginzburg-type equations on the half-line in the critical case

Electric power systems are prone to disturbances and contingencies, which can trigger cascading failures with severe consequences for society. These undesirable events could disintegrate the electrical infrastructure in areas with disconnected elements. In this article, we propose a novel procedure to restore a collapsed power grid composed of multiple islands and isolated assets. The framework developed identifies the power lines to be closed during the electrical network recovery stages. In the latter, link overload limits and generation thresholds are taken into account. Two disintegrated networks based on the well-known IEEE 57-bus test system are built to demonstrate the performance of our proposal. In summary, this methodology provides a solution to recover the power system optimally and reliably.

Hector F. Ruiz-Paredes

Papers

Assessing the criticality of interdependent power and gas systems using complex networks and load flow techniques

Second term of asymptotics for KdVB equation with large initial data

A New Approach for PV Nodes Using an Efficient Backward/Forward Sweep Power Flow Technique

Landau–Ginzburg-type equations on the half-line in the critical case

A Novel Framework Based on Mixed-Integer Linear Programming to Restore a Disintegrated Power Grid after Cascading Failures