Complex Power Networks Research Articles

Power Network in Loop: A Paradigm for Real-Time Simulation and Hardware Testing

This paper discusses a new paradigm of real-time simulation of power systems in which equipment can be interfaced with a real-time digital simulator. In this scheme, one part of a power system can be simulated by using a real-time simulator, while the other part is implemented as a physical system. The only interface of the physical system with the computer-based simulator is through data-acquisition system. The physical system is driven by a voltage-source converter (VSC) that mimics the power system simulated in the real-time simulator. In this paper, the VSC operates in a voltage-control mode to track the point of common coupling voltage signal supplied by the digital simulator. This type of splitting a network in two parts and running a real-time simulation with a physical system in parallel is called a power network in loop here. This opens up the possibility of the study of interconnection of one or several distributed generators to a complex power network. The proposed implementation is verified through simulation studies using PSCAD/EMTDC and through hardware implementation on a TMS320F2812 DSP.

Contemporary Models of Democracy

In the following article I profile three normative models of at the center of current debates in democratic theory-communitarian, deliberative, and agonistic. I then critique their limitations. Calling for greater sociological and political realism, I turn to Danilo Zolo's thesis of complexity and democracy and his view that today is a supplemental feature of techno-oligarchic regimes. Drawing upon the work of Zolo, Michel Foucault, and Sheldon Wolin, I relocate the idea and practice of democracy. I contend that today exists in its most vital and novel form as an ethos and set of strategies operating at the local and micro levels of adaptation and resistance to complex power and policy networks.

Overall site optimisation by Pinch Technology

The importance of integration in process plant design has long been recognised. This is evidenced for example, by the existence of complex heat and power networks in modern production sites. These networks represent site-wide integration. They usually allow process heating duties in several processes to be effected at low cost by using turbine pass-out steam after obtaining a credit for power generated in a central turbine. When looking for energy saving in retrofit projects, an installed heat and power network of this type usually introduces a counter-productive element. A reduction in steam heating duties leads to a reduction in turbine pass-out steam which, in turn, leads to a reduction in power generation. This makes optimisation of the process alone and optimisation of the process in the site context two rather different tasks. More complications are given through other more general reflections across a site. A modern processing plant such as ethylene, for instance, is usually linked into the overall site and interacts with other plants through several utilities, not just back pressure steam. This makes it necessary to not only understand the fundamental process demands but also to analyse these demands in the site context. Process licensors will usually prefer to consider standard designs for individual processes. The best project, on the other hand, will almost invariably be site dependent. This article highlights the distinction between the application of process integration techniques—in particular pinch technology—within an individual process and their wider application in the overall site context. The “counter productive” aspect of heat savings in the context of isntalled heat and power networks is given attention. In addition to energy, the article discusses yields, flexibility and capital cost savings.

Comment: Modelling and numerical solution of multibranched DC rail traction power systems

Based on the method of nodal voltage circuit analysis, a complex DC-fed traction power network with multibranched lines has been modelled. The model also incorporates detailed return circuits so that rail potentials can be calculated, a requirement which arises because of safety and stray current considerations. The introduction of branch joints and divided rail cells greatly increases the quantity of circuit nodes and gives rise to a large sparse conductance matrix. After establishing a set of simultaneous linear equations describing the behaviour of the network, consideration is given to the most suitable method of solution to prevent excessive computation times and storage requirements. Sample calculation results for train, substation busbar and branch joint voltages and currents are given, together with rail potential profiles.

Applications of Optical Fibres for Power Systems Communications

The various limitations of classical communication systems have forced the Power Supply Undertakings to look for alternative media for power systems operation and control. A reliable and most efficient communication is essential for the present day complex power network. The Optical Fibre Communication System has been found to be more promising in this respect because of its larger bandwidth and smaller loss. There is almost complete freedom from signal leakage and cross talk. The system is having many advantages in spite of some limitations. The article describes the various components used, their merits and demerits, their application, experience gained by the users etc.

Universal Machine Modeling for the Representation of Rotating Electric Machinery in an Electromagnetic Transients Program

This paper describes the theory, development and practical application of a new universal machine module, which can be used for the transient analysis of motor/generator phenomena in large and complex power networks. In the general case, doubly-fed electric machines with an arbitrary number of coils and magnetic saturation can be represented. Included are all of the major classes which are of common industrial interest: synchronous and induction machines of 1, 2, or 3 phases, and dc machines. A procedure for maximizing the flexibility of the machine-network interface is explained. Computer implementation has been variably- dimensioned, so that any number of motors or generators can be interconnected with mechanical systems and electric networks of arbitrary size and configuration. Universal machine modeling is now a standard feature of the BPA Electromagnetic Transients Program (EMTP), which is widely used on numerous different computers.

Validation of Turbogenerator Stability Models by Comparisons with Power System Tests

Comparisons are made between results of operating tests on three large turbogenerators of similar rating, but different rotor construction, and digital computer simulations of these machines connected to a complex power network. The simulations were performed using turbogenerator models derived from measurements using frequency response techniques, as well as models calculated on the basis of standard ANSI definitions. For one machine additional data from short circuit and stator decrement tests enabled models to be derived, and these were also used in the simulations.

Stability Performance of 555 MVA Turboalternators - Digital Comparisons with System Operating Tests

Comparisons are made between operating tests on 555 MVA turboalternators, and computer simulations of these machines connected to a complex power network. The simulations were performed using two sets of alternator stability data -one set calculated on the basis of standard ANSI definitions, and the second set derived from appropriate field measurements on the alternators, using frequency response techniques.