Smart grids are considered a promising alternative to the existing power grid, combining intelligent energy management with green power generation. Decomposed further into microgrids, these small-scaled power systems increase control and management efficiency. With scattered renewable energy resources and loads, multi-agent systems are a viable tool for controlling and improving the operation of microgrids. They are autonomous systems, where agents interact together to optimize decisions and reach system objectives. This paper presents an overview of multi-agent systems for microgrid control and management. It discusses design elements and performance issues, whereby various performance indicators and optimization algorithms are summarized and compared in terms of convergence time and performance in achieving system objectives. It is found that Particle Swarm Optimization has a good convergence time, so it is combined with other algorithms to address optimization issues in microgrids. Further, information diffusion and consensus algorithms are explored, and according to the literature, many variants of average-consensus algorithm are used to asynchronously reach an equilibrium. Finally, multi-agent system for multi-microgrid service restoration is discussed. Throughout the paper, challenges and research gaps are highlighted in each section as an opportunity for future work.

Multi-agent system for microgrids: design, optimization and performance

Robust economic dispatch considering automatic generation control with affine recourse process

The objective of the paper is to present a -t stability index that can be used for the security assessment of electric power systems. This index provides an evaluation of the system securitylevel by considering t he values of the accelerations and kinetic energies of the generators, after the occurrence of a large disturbance. The derivation of the index is based on the pattern recognition principles and the fuzzy sets theory. The results that are o btained f rom the application of the i ndex are illustrated by the stability analysis of two power systems. The first is the CIGRE test system, while the second is the Hellenic Interconnected System.

An Application of Fuzzy Concepts to Transient Stability Evaluation

As technological advances give rise to increasingly more powerful computers, applied mathematicians are able to simulate phenomena of considerable complexity using nurmerical models. One of the problems is how to transform the volminuous output data from a numerical form to a visual one, which is easier for humans to comprehend. This article analyzes a case study from the field of meteorology. A weather simulation, program produces numerical output which defines the values of several variables as functions of the three spatial parameters and time. The output of this model is then used as the input to our grphic rendering system, which displays these complex data sets using stereo animation, employing novel techniques to add realism in the animation sequences. We take advantages of the special geometrical configuration to reduce the computation time by about two orders of magnitude. The value our approach is that our techniques for representing four-dimensional data sets can easily be extended to display phenomena in other disciplines.

Stereo Animation for Very Large Data Bases: Case Study- Meteorology

The stability of integrated power systems has a major role, particularly in online system security and planning. Catastrophe theory as a qualitative mathematical tool has been used previously for studying both steady state stability and transient state stability of power systems. By applying catastrophe theory to the transient stability of a power system, the equivalent machine system has been derived. The author presents a technique for applying catastrophe theory with the aim of defining the stability regions for multimachine cylindrical rotor systems. This technique is performed in such a way that the individual machine energies are balanced. It is valid for any fault type or location and is effective for online transient stability assessment.

Power systems transient stability assessment using catastrophe theory

The output of a conventional transient stability program is analyzed using transient energy functions for individual machines. The analyst is provided with a quantitative index of the degree of stability or instability for each generator. This index is useful for guiding the selection of subsequent case studies. The transient energy consists of two components: kinetic and potential energy. In the post-disturbance period, profiles of the kinetic energy (VKE), the potential energy (VPE), and the time derivative of the potential energy (V?PE) are obtained. These are used to develop a criterion for the degree of stress on a disturbed but stable machine, and to assess the extent of instability for an unstable machine. The method of analysis has been tested on two power networks representing the system of the state of Iowa, and validated by studies on a Philadelphia Electric Co. network.

K. C. Kruempel

Papers

Transient Stability Program Output Analysis