We presently enjoy a predominantly AC electrical distribution system, the engineering basis for which was designed over 100 years ago. While AC distribution systems have served us well, we should periodically pause to assess what opportunities we have accepted or been denied by the overwhelming predominance of AC electrical power distribution systems. What opportunities could be obtained by engineering DC distribution into at least portions of our present system? What advantages of the present AC distribution system should be recognized and protected? This paper will focus on distribution within premise and low-voltage distribution systems. Specifically, we will address the conversion efficiency costs of adopting various premise AC and DC distribution system topologies. According to a simple predictive model formulated in this paper, premise residential DC distribution will incur unfavorable total conversion efficiency compared with existing AC premise distribution. However, if a residence is supplied by a fuel cell or another DC generator, the total conversion efficiency within a residential DC distribution system could be similar to, or even better than, that for AC distribution.

AC Versus DC Distribution SystemsDid We Get it Right

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Real-Time Systems: Scheduling, Analysis, and Verification

We presently enjoy a predominantly ac electrical distribution system, the engineering basis for which was designed over 100 years ago. While ac distribution systems have served us well, we should periodically pause to assess what opportunities we have accepted or been denied by the overwhelming predominance of ac electrical power distribution systems. What opportunities could be obtained by engineering dc distribution into at least portions of our present system? What advantages of the present ac distribution system should be recognized and protected? This paper will focus on distribution within premise and low-voltage distribution systems. Specifically, we will address the conversion efficiency costs of adopting various premise ac and dc distribution system topologies. According to a simple predictive model formulated in this paper, premise residential dc distribution will incur unfavorable total conversion efficiency compared with existing ac premise distribution. However, if a residence is supplied by a fuel cell or another dc generator, the total conversion efficiency within a residential dc distribution system could be similar to, or even better than, that for ac distribution.

AC versus DC distribution systems-did we get it right?

Congestion management in open access based on relative electrical distances using voltage stability criteria

Faster evolutionary algorithm based optimal power flow using incremental variables

The operation and planning of large interconnected power systems are becoming increasingly complex. To maintain security of such systems, it is desirable to estimate the effect of contingencies and plan suitable measures to improve system security/stability. The paper presents an approach for selection of unified-power-flow-controller (UPFC-) suitable locations considering normal and network contingencies after evaluating the degree of severity of the contingencies. The ranking is evaluated using composite-criteria-based fuzzy logic for eliminating masking effects. The fuzzy approach, in addition to real-power loadings and bus-voltage violations, also used voltage-stability indexes at the load buses as the post-contingent quantities to evaluate the network-contingency ranking. The selection of UPFC-suitable locations uses the criteria on the basis of improved system security/stability. The proposed approach for selection of UPFC-suitable locations has been tested under simulated conditions on a few power systems and the results for a 205-node real-life equivalent regional-power-grid system of three interconnected utility systems are presented for illustration purposes.

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Improvement of system security with unified-power- flow controller at suitable locations under network contingencies of interconnected systems

Transmission charges of power contracts based on relative electrical distances in open access

The dependence of the system voltage stability on reactive power distribution forms the basis for reactive power optimisation. The technique attempts to utilise fully the reactive power sources in the system to improve the voltage stability and profile as well as meeting the reactive power requirements at the AC-DC terminals to facilitate the smooth operation of DC links. The method involves successive solution of steady-state power flows and optimisation of reactive power control variables using linear programming techniques. The proposed method has been applied to a few systems and the results obtained on a real-life equivalent 96-bus AC and a two-terminal DC system are presented for illustration.

Lawrence Jenkins

Papers

Improvement of system security with unified-power- flow controller at suitable locations under network contingencies of interconnected systems

Transmission charges of power contracts based on relative electrical distances in open access

Optimum allocation of reactive power for voltage stability improvement in AC-DC power systems

Application of UPFC for system security improvement under normal and network contingencies

An approach for evaluation of transmission costs of real power contracts in deregulated systems