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

Generator coherency identification algorithm using modal and time-domain information

Coherency group identification is an integral constituent part of the wider field of reduction techniques in power systems. It consists of separating the machines in the system into groups that feature similar behavior. This paper presents a coherency identification algorithm for dynamic studies. The algorithm combines both modal and time domain techniques in an effort to combine the merits of both approaches. Its outcome is a suggested optimal number of clusters alongside the clustering itself. Tests have been conducted on a sample power system of 39 buses and its validity has been demonstrated

A DC power flow extension

In this work an extension of the well-known DC power flow method is presented. A normal DC power flow of the system is executed to determine voltage angles and a novel derivation of voltage amplitudes is devised. The latter is rigorously formulated and eight alternative ways to tackle it are proposed. Comparative studies between the proposed versions of the algorithm verify its effectiveness in producing an accurate estimate of the voltage profile, on average in the order of 10-3 pu close to the exact solution. The proposed algorithm features very favorable computational requirements of approximately a fifth of the time required for an exact solution. Its computational efficiency renders it a solid candidate for hard real-time applications required in the emerging smart grid

Distributed real-time dynamic security assessment using intelligent techniques

In real time scenario, transmission (of power) in power systems may not be always ideal i.e. they may be interrupted. As a result, the synchronization among the power generating modules may be lost. Loss of synchronization has a direct effect on the stability of power generators. Generally time domain simulation (TDS) is used to examine the stability but TDS is a time consuming process, hence we are required to explore other approaches. Accurate real-time security assessment is necessary to facilitate operations close to the stability limits. Hence for this purpose a distributed time efficient approach has been adopted to predict future values of system parameters and use the same to predict future stability of power generating modules by partially using artificial neural network and fuzzy interference system based on European Network of Transmission System Operators for Electricity (ENTSO-E) defined criteria

Pipelined Numerical Integration on Reduced Accuracy Architectures for Power System Transient Simulations

This work concerns a dedicated mixed-signal power system dynamic simulator. The equations that describe the behavior of a power system can be decoupled in a large linear system that is handled by the analog part of the hardware, and a set of differential equations. The latter are solved using numerical integration algorithms implemented in dedicated pipelines on a field programmable gate array (FPGA). This data path is operating in a precision-starved environment since is it synthesized using fixed-point arithmetic, as well as it relies on low-precision solutions that come from the analog linear solver. In this paper, the pipelined integration scheme is presented and an assessment of different numerical integration algorithms is performed based on their effect on the final results. It is concluded that in low-precision environments higher order integration algorithms should be preferred when the time step is large, since simpler algorithms result in unacceptable artifacts (extraneous instabilities)

Synthesis, Structure, and Antiproliferative Activity of Three Gallium(III) Azole Complexes

As part of our interest into the bioinorganic chemistry of gallium, gallium(III) complexes of the azole ligands 2,1,3-benzothiadiazole (btd), 1,2,3-benzotriazole (btaH), and 1-methyl-4,5-diphenylimidazole (L) have been isolated. Reaction of btaH or btd with GaBr3 or GaCl3 resulted in the mononuclear complexes [GaBr3(btaH)2] (1) and [GaCl3(btd)2] (2), respectively, while treatment of GaCl3 with L resulted in the anionic complex (LH)2[GaCl4] (3). All three complexes were characterized by single-crystal X-ray crystallography and IR spectroscopy, while their antiproliferative activities were investigated against a series of human and mouse cancer cell lines

Power network transient stability electronics emulator using mixed-signal calibration

The emerging field of power system emulation for real time smart grid management is very demanding in terms of speed and accuracy. This paper provides detailed information about the electronics calibration process of a high-speed power network emulator dedicated to the transient stability analysis of power systems. This emulator uses mixed-signal hardware to model the dynamic behavior of a power network. Special design allows the self-calibration of the analog electronics through successive measurements and correction steps. The calibration operation guarantees high resolution of the transient stability analysis results, so that they can be reliably used for operational planning and control on real power networks

A 3D architecture platform dedicated to high-speed computation for power system

This paper presents an innovative 3D hardware architecture for power system dynamic and transient stability. Based on an intrinsic parallel architecture by means of mixedsignal circuits (analog and digital) it overcomes the speed of numerical simulators for given models. This approach does not competing the accuracy and model complexity of the high performance numerical simulators. It intends to complement them with the advantage of speed, low-cost, portability and autonomous functions. The presented architecture provides an ultra-high speed platform by means of emulation principle. The proof of concept is an array of 4x24 nodes reconfigurable platform. Hardware details and comparisons with a reference digital simulator are given

An Ultra-High Speed Emulator Dedicated to Power System Dynamics Computation Based on a Mixed-Signal Hardware Platform

This paper presents an ultra-high speed hardware platform dedicated to power system dynamic (small signal) and transient (large signal) stability. It is based on an intrinsic parallel architecture which contains hybrid mixed-signal (analog and digital) circuits. For a given model, this architecture overcomes the speed of the numerical simulators by means of the so-called emulation approach. Indeed, the emulation speed does not depend on the power system size. This approach is nevertheless not competing against high-performance numerical simulators in term of accuracy and model complexity. It targets to complement the numerical simulators with the advantage of speed, portability, low cost and autonomous functioning. The proof of concept is a flexible and modular 96-node hardware platform. It is based on a reconfigurable array of power system buses called Field Programmable Power Network System (FPPNS). Details on this hardware are given. Two benchmark topologies with, respectively, 17 nodes and 57 nodes are provided. Comparisons with a digital simulator are done in terms of speed and accuracy. The calibration of the system is explained and different applications are proposed and discussed. The promising results of this hardware platform show that the design of a fully integrated solution containing hundreds of power system buses can be achieved in order to provide a low cost solution

A Transient Stability Assessment Method using Post-Fault Trajectories

Abstract—Transient Stability Assessment (TSA) is the process in which the stability of a system is characterized qualitatively or quantitatively. The TSA algorithm presented in this paper is derived from the well-established Single Machine Equivalent (SIME) method and can thus be categorized as a hybrid directtemporal method. The novelty of the proposed algorithm is that it derives a Transient Stability Index (TSI) with a single Time-Domain (TD) simulation for both stable and unstable cases. The resulting TSI is uniform in units and linear around the instability point. Results are reported for two sample power systems of 9 and 36 buses. The proposed algorithm has also been successfully employed to speed-up a Critical Clearing Time (CCT) determination algorithm. Index Terms--power system dynamics, SIME method, timedomain simulation, transient stability assessment I