Deterministic random walk preconditioning for power grid analysis

In reservoir simulation, algebraic multigrid (AMG) solvers are the most effective solvers for linear systems arising from the discretization of pressure equations. The AMG solvers are also important components for many multi-stage preconditioners. In this paper, we introduce our work on developing these solvers on NVIDIA Tesla GPUs. A classical algebraic multigrid solver is developed. Numerical experiments are performed to test the efficiency of this GPU-based parallel AMG solver. The numerical experiments show that the GPU-based algebraic solver is sped up to 12.5 times faster than the corresponding CPU-based algebraic multigrid solver.

Electric power has become an essential part of daily life: we plug our electronic devices in, switch our lights on, and expect to have power. As the availability of power is usually taken for granted in modern societies, we mostly feel annoyed at its absence and perceive the importance of power during outages which have severe effects on the public order. Blackouts have had disastrous consequences for many countries and they continue to occur frequently. Such examples demonstrate the necessity for careful analysis and planning of power grids, to ultimately increase the reliability of power grids. The power grids have evolved due to economic, environmental and human-caused factors. In addition to the contingency analysis, nowadays, the operation and planning of power grids are facing many other challenges (such as demand growth, targeted attacks, cascading failures, and renewable energy integration). Thus, many questions arise, including: which buses (nodes) to connect with a new line (link)? What are the impacts of malicious attacks on power grids? How may an initial failure result in a cascade of failures? How to prepare for the integration of renewable energy? Answering such questions requires developing new concepts and tools for analysing and planning of power grids. Power grids are one of the largest and the most complex man-made systems on earth. The complex nature of power grids and its underlying structure make it possible to analyse power grids relying on network science. The applications of network science on power grids have shown the promising potential to capture the interdependencies between components and to understand the collective emergent behaviour of complex power grids. This thesis is motivated by the increasing need of reliable power grids and the merits of network science on the investigation of power grids. In this context, relying on network science, we model and analyse the power grid and its near-future challenges in terms of line removals/additions, malicious attacks, cascading failures, and renewable integration.

Due to the rapid advances of integrated circuit technology, the size of power distribution network (power grid) is becoming larger and larger. There are usually multi-million nodes on a power grid. Analyzing these huge power grids has become very expensive in terms of both time and memory. This paper presents an efficient parallel implementation of the Additive Schwarz Method (ASM) for IR-drop analysis of large-scale power grid. Based on distributed memory system, a new data storage method is proposed to overcome memory bottleneck of traditional methods. Techniques including overlapping in multiple layer and irregular power grid, via detection and grouping are utilized to accelerate the simulation. Moreover, a new communication strategy exhibiting minimum communication overhead is proposed. The proposed method is very accurate in the final solution, with the maximum error less than 0.1mv. Experimental results on industrial medium size benchmarks show that the proposed method achieves more than 110X speedup over a state-of-the-art direct LU solver. The proposed approach can easily solve very large-scale benchmarks, while LU solver fails to obtain the solution because of system memory limitation. It is the first time reported in literature that IR-drop analysis of power grid with over 190M nodes is successfully solved within 5 minutes.

Power grid analysis is a challenging problem for modern integrated circuits. For 3-D systems fabricated using stacked tiers with TSVs, traditional power grid analysis methods for planar (2-D) circuits do not demonstrate the same performance. An efficient IR drop analysis method for 3-D large-scale circuits, called 3-D voltage propagation method, is proposed in this paper. This method is compared with another widely used power grid analysis method, with preconditioned conjugated gradients. Simulation results demonstrate that the proposed method is more efficient for the IR drop analysis of large size 3-D power grids. Speedups between 10× to 20× over the preconditioned conjugated gradients method are shown.

As VLSI techniques are getting more and more advanced, the size of the power grid network increases dramatically. Therefore, the power grid analysis becomes a challenging task during the design procedure. This work utilizes the macromodeling technique [1] and enhances the Orthogonal Matching Pursuit (OMP) based method [2] to develop an effective and robust incremental analysis method for the power grid network, MA-OMP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sup> . Given a power grid network, MA-OMP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sup> not only can deal with the change of its element values but also can handle the modification of its topology. The experimental results show that MA-OMP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sup> can be an order of magnitude faster than the OMP-based method [2] which can only deal with the change of element values of the power grid. The experimental results also demonstrate that MA-OMP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sup> can accurately and efficiently handle the modified topology of the power grid network.

With the development of power electronic devices, the research of Flexible AC Transmission System (FACTS) in regulating line power flow and improving static voltage stability is more in-depth. This paper discusses the static voltage stability of power grid with new energy taking into account the distributed static series compensator (DSSC), and evaluates the power flow control efficiency of DSSC from the aspect of system static voltage stability. First, the equivalent circuit and working principle of DSSC are analyzed, and the power flow equations are obtained based on the equivalent power injection model of DSSC; Secondly, based on the power flow calculation equation, the efficiency evaluation index that can reflect the static voltage stability of the system is proposed, and the impact of new energy with different capacities on the static voltage stability is calculated and analyzed; Finally, the proposed method is verified by the simulation analysis of IEEE-24 bus system and actual power grid: the proposed method is fast and simple, and has certain engineering application value.

The global power grid is undergoing a major transformation as a result of the growing utilization of renewable energy sources (RESs). The incorporation of these RESs is leading to a decline in the use of conventional synchronous generators and an increase in the use of inverter-based RESs. This shift is causing a decrease in the grid's inertia, presenting substantial difficulties for grid operators to maintain frequency stability. The purpose of this study is to examine the impact of declining inertia on the frequency behavior of the grid, as RESs become more prevalent. In order to measure the impact, this study utilizes eigenvalue analysis of power grids to assess the sensitivity of grid frequency and rate of change of frequency (RoCoF) characteristics, as well as the lowest frequency, to variations in grid inertia resulting from changes in RES penetration. Moreover, we have introduced indices that quantify the impact of RES penetration on the grid frequency behaviour in comparison to a grid without RES. To showcase the proposed approach, this research presents case studies using the modified IEEE 39 bus test system, which demonstrate the ability to assess the impact of a high RESs penetration on grid frequency characteristics.

Regulatory material defines the general technical requirements that power-generating plants must comply with to be connected to the public power transmission or distribution grids. The purpose of these specifications is to preserve the safety of life and property, grid safety, the quality and availability of the distributed voltage. The February 10, 2000, law pertaining to the modernization and development of the electric power utilities stipulates that the requirements will be set down in a decree (statutory material of a higher legal status than an order). In this framework, a decree compiling all the requirements for connections to public power distribution grids is in the works. It will follow up current statutory material. Before the decree is passed, it will be submitted to the review of the Commission de Regulation de l'Electricite (electricity control commission) and the Comite Technique de l'Electricite (electricity technical committee), marshalling experts and representatives of administrations, and will be notified to the European Commission. The main provisions that are being planned (December 2000) are described. They may change depending on further study development and the recommendations from the above-mentioned agencies.

Observational and modeling study of interactions between urban heat island and heatwave in Beijing

The recent developments in electric vehicles (EVs) causes several issues that have not been satisfactorily addressed. One of the foremost problems is the charging–discharging processes of EV batteries with diverse characteristics. Although a charging station is the first choice in this regard, a battery swap station (BSS) is also a suitable alternative solution as it eliminates long waiting periods and battery degradation due to fast charging. BSS has the capability to ensure prompt and efficient service for electric vehicles. Since BSS has a large number of battery systems, optimum planning of the charging–discharging operations of the batteries is critical for both BSS and the grid. This study presents an optimal charging–discharging schedule for multiple BSSs based on the swap demand of privately owned EVs and electric bus (EB) public transportation system. In addition, BSSs reinforce the power grid by providing ancillary services such as peak shaving and valley filling with demand response programs. In order to increase the flexibility of the operation, the mobile swapping station (MSS) concept, an innovative and dynamic service, is introduced to the literature and added to the model. The results indicate that BSS is an essential agent in the ancillary services market and the MSS concept is a yielding solution for both BSSs and power networks. Last, the data utilized in the study for swap demand calculation and power grid analysis are real-world data from Berlin, Germany.

Over the last decade, the Common Information Model (CIM), as specified by IEC 61970 / 61968, has become an important document format for the storage of power grid data. Its object-oriented design makes it easily maintainable and extensible for many use cases in the energy sector. As a result, more and more power grid analysis and simulation tools allow the import and export of CIM based power grid data. Unfortunately, many of them are proprietary and therefore not convenient in the research area since their component models and numerical back-ends often cannot be modified by the user. Thus, open-source alternatives are in demand, such as simulation environments based on the popular modeling language Modelica. Therefore, this paper presents our approach of a template based CIM to Modelica converter. The usage of templates makes it easily adaptable for the generation of Modelica system models targeting arbitrary Modelica libraries. The presented approach is implemented in an open-source project called CIMverter, evaluated on a real-world case with two Modelica power system libraries, and validated against a proprietary simulation tool.

There is a big difference between transmission line state estimation results and actual measured values, which seriously affects the normal operation of power grid analysis and other links. As a kind of static basic data, the accuracy of transmission line parameters affects the result of state estimation. Power system state estimation is the basis of dispatch automation application functions. State estimation can not only provide more credible basic data for power grid analysis, but also the difference between state estimation results and actual measured values can reflect the quality of basic power grid data. In order to solve the low state estimation accuracy of the short-distance non-transposition double-circuit transmission line on the same tower with the power plant directly connected to the grid, simulate line and grid operation through PSCAD, phase split modeling of the line, calculate line parameters, analyze the influence of the self-inductance and mutual inductance of lines under different phase sequence arrangements and the reasons for the lower accuracy of the line reactive power.KeywordsDouble-circuit transmission lines on the same towerState estimationPSCAD simulation

We propose a new, efficient, adaptive algebraic multigrid (AMG) solver strategy for the discrete systems of partial differential equations arising from structured or unstructured grid models in reservoir simulation. The proposed strategy has been particularly tailored to linear systems of equations arising in adaptive implicit methods. The coarsening process of the AMG method designed automatically employs information on the physical structure of the models; as a smoother, an adaptive ILUT method is employed, taking care of an efficient solution of the hyperbolic parts whilst providing adequately smooth errors for the elliptic parts. To achieve a good compromise of high efficiency and robustness for a variety of problem classes – ranging from simple, small black-oil to challenging, large compositional models – an automatic, adaptive ILUT parameter and AMG solver switching strategy, α-SAMG, has been developed. Its efficiency is demonstrated for eight industrial benchmark cases by comparison against standard one-level and AMG solvers as well as the pure one- level variant of the proposed new strategy. In addition, very promising results of first parallel runs are shown.

Public Street Lighting is one of the main components of total energy consumption in urban areas. Nearly 304 million street lights are installed worldwide and estimated that will increase by 352 million by 2025. However, street lighting is one of the largest consumptions of electrical energy and around 40% of the total energy consumption in cities around the world. This study aims to monitor and control energy management between public street lighting hybrid solar power systems and grid sources to save energy, save costs, and reduce CO2 emissions by using engineering economic analysis methods. The results showed that the payback period of the systems is three years from electricity cost savings of around $2,062.19 or 88.25% within 25 years of investment and CO2 emissions that can reduced up to 85.7%. Economically, this hybrid system has succeeded in saving electricity costs per month and increasing the use of renewable energy.

A new high-order compact (HOC) cascadic multigrid (MG) strategy is developed for modeling large-scale complex gravity problems on nonuniform rectilinear grids. First, the governing 3D Poisson’s gravitational potential equation is discretized by a novel HOC difference scheme, which allows for Robin boundary conditions to further reduce the computational domain. Then, the resulting asymmetric linear system of equations is solved by a generalized extrapolation cascadic MG (gEXCMG) method augmented with a novel MG prolongation operator. The quartic interpolation and completed Richardson extrapolation assist this MG prolongation operator to produce a good initial guess for the biconjugate gradient stabilized smoother. Two synthetic and SEG/EAGE salt models are examined to verify the presented approach. Results indicate that our algorithm can efficiently and accurately produce the gravity signals for complex geologic models. Moreover, the comparisons with the state-of-the-art algebraic MG solvers demonstrate that our gEXCMG solver offers substantially better efficiency with significantly less memory consumption. Therefore, our newly developed method has the potential for serving as a forward engine in large-scale gravity inversions.