ExaGridPF: A Parallel Power Flow Solver for Transmission and Unbalanced Distribution Systems

This paper investigates parallelization strategies for solving power flow problems in both transmission and unbalanced, three-phase distribution systems by developing a scalable power flow solver, ExaGridPF, which is compatible with existing high-performance computing platforms. Newton-Raphson (NR) and Newton-Krylov (NK) algorithms have been implemented to verify the performance improvement over both standard IEEE test cases and synthesized grid topologies. For three-phase, unbalanced system, we adapt the current injection method (CIM) to model the power flow and utilize SuperLU to parallelize the computing load across multiple threads. The experimental results indicate that more than 5 times speedup ratio can be achieved for synthesized large-scale transmission topologies, and significant efficiency improvements are observed over existing methods for the distribution networks

Using GPU to Accelerate Linear Computations in Power System Applications

With the development of advanced power system controls, the industrial and research community is becoming more interested in simulating larger interconnected power grids. It is always critical to incorporate advanced computing technologies to accelerate these power system computations. Power flow, one of the most fundamental computations in power system analysis, converts the solution of non-linear systems to that of a set of linear systems via the Newton method or one of its variants. An efficient solution to these linear equations is the key to improving the performance of power flow computation, and hence to accelerating other power system applications based on power flow computation, such as optimal power flow, contingency analysis, etc. This dissertation focuses on the exploration of iterative linear solvers and applicable preconditioners, with graphic processing unit (GPU) implementations to achieve performance improvement on the linear computations in power flow computations. An iterative conjugate gradient solver with Chebyshev preconditioner is studied first, and then the preconditioner is extended to a two-step preconditioner. At last, the conjugate gradient solver and the two-step preconditioner are integrated with MATPOWER to solve the practical fast decoupled load flow (FDPF), and an inexact linear solution method is proposed to further save the runtime of FDPF. Performance improvement is reported by applying these methods and GPU-implementation. The final complete GPU-based FDPF with inexact linear solving can achieve nearly 3x performance improvement over the MATPOWER implementation for a test system with 11,624 buses. A supporting study including a quick estimation of the largest eigenvalue of the linear system which is required by the Chebyshev preconditioner is presented as well. This dissertation demonstrates the potential of using GPU with scalable methods in power flow computation

Power Bounded Computing on Current & Emerging HPC Systems

Power has become a critical constraint for the evolution of large scale High Performance Computing (HPC) systems and commercial data centers. This constraint spans almost every level of computing technologies, from IC chips all the way up to data centers due to physical, technical, and economic reasons. To cope with this reality, it is necessary to understand how available or permissible power impacts the design and performance of emergent computer systems. For this reason, we propose power bounded computing and corresponding technologies to optimize performance on HPC systems with limited power budgets. We have multiple research objectives in this dissertation. They center on the understanding of the interaction between performance, power bounds, and a hierarchical power management strategy. First, we develop heuristics and application aware power allocation methods to improve application performance on a single node. Second, we develop algorithms to coordinate power across nodes and components based on application characteristic and power budget on a cluster. Third, we investigate performance interference induced by hardware and power contentions, and propose a contention aware job scheduling to maximize system throughput under given power budgets for node sharing system. Fourth, we extend to GPU-accelerated systems and workloads and develop an online dynamic performance & power approach to meet both performance requirement and power efficiency. Power bounded computing improves performance scalability and power efficiency and decreases operation costs of HPC systems and data centers. This dissertation opens up several new ways for research in power bounded computing to address the power challenges in HPC systems. The proposed power and resource management techniques provide new directions and guidelines to green exscale computing and other computing systems

Parallel and Multistep Simulation of Power System Transients

RÉSUMÉ La simulation des régimes transitoires électromagnétiques (EMT) est devenue indispensable aux ingénieurs dans de nombreuses études des réseaux électriques. L’approche EMT a une nature de large bande et est applicable aux études des transitoires lents (électromécaniques) et rapides (électromagnétiques). Cependant, la complexité des réseaux électriques modernes qui ne cesse de s’accroître, particulièrement des réseaux avec des interconnexions HVDC et des éoliennes, augmente considérablement le temps de résolution dans les études des transitoires électromagnétiques qui exigent la résolution précise des systèmes d’équations différentielles et algébriques avec un pas de calcul pré-déterminé. En tant que sujet de recherche, la réduction du temps de résolution des grands réseaux électriques complexes a donc attiré beaucoup d’attention et d’intérêt. Cette thèse a pour objectif de proposer de nouvelles méthodes numériques qui sont efficaces, flexibles et précises pour la simulation des régimes transitoires électromagnétiques des réseaux électriques. Dans un premier temps, une approche parallèle et à pas multiples basée sur la norme Functional Mock-up Interface (FMI) pour la simulation transitoire des réseaux électriques avec systèmes de contrôle complexes est développée. La forme de co-simulation de la norme FMI dont l’objectif est de faciliter l’échange de données entre des modèles développés avec différents logiciels est implémentée dans EMTP. Tout en profitant de cette implémentation, les différents systèmes de contrôle complexes peuvent être découplés du réseau principal en mémoire et résolus de façon indépendante sur des processeurs séparés. Ils communiquent avec le réseau principal à travers une interface de co-simulation pendant une simulation. Cette méthodologie non seulement réduit la charge de calcul total sur un seul processeur, mais elle permet aussi de simuler les systèmes de contrôle découplés de façon parallèle et à pas multiples. Deux modes de co-simulation sont proposés dans la première étape du développement, qui sont les modes asynchrone et synchrone. Dans le mode asynchrone, tous les systèmes de contrôle découplés (esclaves) sont simulés en parallèle avec le réseau principal (maître) en utilisant un seul pas de calcul tandis que le mode synchrone permet une simulation séquentielle en utilisant différents pas de calcul dans le maître et les esclaves. La communication entre le maître et les esclaves est réalisée et coordonnée par des fonctions qui implémentent le primitif de synchronisation de bas niveau sémaphore.----------ABSTRACT The simulation of electromagnetic transients (EMT) has become indispensable to utility engineers in a multitude of studies in power systems. The EMT approach is of wideband nature and applicable to both slower electromechanical as well as faster electromagnetic transients. However, the ever-growing complexity of modern-day power systems, especially those with HVDC interconnections and wind generations, considerably increases computational time in EMT studies which require the accurate solution of usually large sets of differential and algebraic equations (DAEs) with a pre-determinded time-step. Therefore, computing time reduction for solving complex, practical and large-scale power system networks has become a hot research topic. This thesis proposes new fast, flexible and accurate numerical methods for the simulation of power system electromagnetic transients. As a first step in this thesis, a parallel and multistep approach based on the Functional Mock-up Interface (FMI) standard for power system EMT simulations with complex control systems is developed. The co-simulation form of the FMI standard, a tool independent interface standard aiming to facilitate data exchange between dynamic models developed in different simulation environments, is implemented in EMTP. Taking advantage of the compatibility established between the FMI standard and EMTP, various computationally demanding control systems can be decoupled from the power network in memory, solved independently on separate processors, and communicate with the power network through a co-simulation interface during a simulation. This not only reduces the total computation burden on a single processor, but also allows parallel and multistep simulation for the decoupled control systems. Following a master-slave co-simulation scheme (with the master representing the power network and the slaves denoting the decoupled control systems), two co-simulation modes, which are respectively the asynchronous and synchronous modes, are proposed in the first stage of the development. In the asynchronous mode, all decoupled subsystems are simulated in parallel with a single numerical integration time-step whereas the synchronous mode allows the use of different numerical time-steps in a sequential co-simulation environment. The communication between master and slaves is coordinated by functions employing the low-level synchronization primitive semaphore

A mixed-signal computer architecture and its application to power system problems

Radical changes are taking place in the landscape of modern power systems. This massive shift in the way the system is designed and operated has been termed the advent of the ``smart grid''. One of its implications is a strong market pull for faster power system analysis computing. This work is concerned in particular with transient simulation, which is one of the most demanding power system analyses. This refers to the imitation of the operation of the real-world system over time, for time scales that cover the majority of slow electromechanical transient phenomena. The general mathematical formulation of the simulation problem includes a set of non-linear differential algebraic equations (DAEs). In the algebraic part of this set, heavy linear algebra computations are included, which are related to the admittance matrix of the topology. These computations are a critical factor to the overall performance of a transient simulator. This work proposes the use of analog electronic computing as a means of exceeding the performance barriers of conventional digital computers for the linear algebra operations. Analog computing is integrated in the frame of a power system transient simulator yielding significant computational performance benefits to the latter. Two hybrid, analog and digital computers are presented. The first prototype has been implemented using reconfigurable hardware. In its core, analog computing is used for linear algebra operations, while pipelined digital resources on a field programmable gate array (FPGA) handle all remaining computations. The properties of the analog hardware are thoroughly examined, with special attention to accuracy and timing. The application of the platform to the transient analysis of power system dynamics showed a speedup of two orders of magnitude against conventional software solutions. The second prototype is proposed as a future conceptual architecture that would overcome the limitations of the already implemented hardware, while retaining its virtues. The design space of this future architecture has been thoroughly explored, with the help of a software emulator. For one possible suggested implementation, speedups of four orders of magnitude against software solvers have been observed for the linear algebra operations