A set of power generators and loads is considered a microgrid if, in comparison to larger power systems, they are smaller and have lower ratings and capacities. An islanded microgrid is a microgrid that is not connected to a larger power system. Generally, ac power systems have three main objections. First, they must always balance power generation with demand. Secondly, they must regulate freq...

Crowder et al. (Oper. Res. 31 (1983) 803–834) conjectured that the separation problem for cover inequalities for binary integer programs is polynomially solvable. We show that the general problem is NP-hard but a special case is solvable in linear time. c © 1998 Elsevier Science B.V. All rights reserved.

We show that the maximization version of the multi-level facility location problem can be approximated by a factor of 0:5. The only previously known result is a factor of 0:47 for the two-level case obtained recently by Bumb (Oper. Res. Lett. 29(4) (2001) 155). c © 2002 Elsevier Science B.V. All rights reserved.

The μCHP is expected as the successor of the conventional high-efficiency boiler producing next to heat also electricity with a comparable overall efficiency. A μCHP appliance saves money and reduces greenhouse

A low voltage distribution network with large amounts of small sized dispersed generation can be operated as an isolated system in certain conditions. This paper presents the control strategies to be used in such a system to deal with islanded operation and to exploit the local generation resources as a way to help in power system restoration after a general blackout. A sequence of actions for ...

Consider the ( n 2 ) (or O(n2)) min-cut problems on a graph with n nodes and nonnegative edge weights. Gomory and Hu [J. Soc. Indust. Appl. Math., 9 (1961), pp. 551–570] showed (essentially) that there are at most n−1 different min-cuts. They also described a compact structure (the flow equivalent tree) of size O(n) with the following property: for any pair of nodes, the value of a min-cut can ...

We propose a polynomial-time algorithm to find an equitable home–away assignment for a given timetable of a round-robin tournament. Our results give an answer to a problem raised by Elf et al. (Oper. Res. Lett. 31 (2003) 343), which concerns the computational complexity of the break minimization problem in sports timetabling. © 2004 Elsevier B.V. All rights reserved.