Linear/Quadratic Programming-Based Optimal Power Flow using Linear Power Flow and Absolute Loss Approximations

This paper presents novel methods to approximate the nonlinear AC optimal power flow (OPF) into tractable linear/quadratic programming (LP/QP) based OPF problems that can be used for power system planning and operation. We derive a linear power flow approximation and consider a convex reformulation of the power losses in the form of absolute value functions. We show four ways how to incorporate this approximation into LP/QP based OPF problems. In a comprehensive case study the usefulness of our OPF methods is analyzed and compared with an existing OPF relaxation and approximation method. As a result, the errors on voltage magnitudes and angles are reasonable, while obtaining near-optimal results for typical scenarios. We find that our methods reduce significantly the computational complexity compared to the nonlinear AC-OPF making them a good choice for planning purposes

Dynamic Reserves in Matching Markets

We study a school choice problem under affirmative action policies where authorities reserve a certain fraction of the slots at each school for specific student groups, and where students have preferences not only over the schools they are matched to but also the type of slots they receive. Such reservation policies might cause waste in instances of low demand from some student groups. To propose a solution to this issue, we construct a family of choice functions, dynamic reserves choice functions, for schools that respect within-group fairness and allow the transfer of otherwise vacant slots from low-demand groups to high-demand groups. We propose the cumulative offer mechanism (COM) as an allocation rule where each school uses a dynamic reserves choice function and show that it is stable with respect to schools' choice functions, is strategy-proof, and respects improvements. Furthermore, we show that transferring more of the otherwise vacant slots leads to strategy-proof Pareto improvement under the COM

Beyond the global financial crisis: central banking in a new global financial system

Since the outbreak of the global crisis in mid 2007, there has been an extensive discussion on root causes. Some blame the greed and corruption of financial actors. Others put the blame on central bankers for easy money or regulators who remained idle as too much risks accumulated in financial markets. According to advanced economies, global imbalances have been caused by emerging surplus countries that keep their currency undervalued and their domestic consumption restricted. It is unfortunate that all these arguments and counter arguments, which may be valid in their own way, prevents a more general discussion on the deep-seated conflicts and contradictions in the global economic, social and political paradigm upon which the world order is built. To put it another way, the problems we face today do not arise from some operational failures, but from the system itself and the underlying philosophical framework. In fact this is a crisis of three main pillars of our existing system: the crisis of the economic theory, the crisis of the globalization, and the crisis of market based financial system.global financial crisis, economic theory, financial system

Transmission Network Reduction Method using Nonlinear Optimization

This paper presents a new method to determine the susceptances of a reduced transmission network representation by using nonlinear optimization. We use Power Transfer Distribution Factors (PTDFs) to convert the original grid into a reduced version, from which we determine the susceptances. From our case studies we find that considering a reduced injection-independent evaluated PTDF matrix is the best approximation and is by far better than an injection-dependent evaluated PTDF matrix over a given set of arbitrarily-chosen power injection scenarios. We also compare our nonlinear approach with existing methods from literature in terms of the approximation error and computation time. On average, we find that our approach reduces the mean error of the power flow deviations between the original power system and its reduced version, while achieving higher but reasonable computation times

Non-autonomous Svinolupov Jordan KdV Systems

Non-autonomous Svinolupov-Jordan systems are considered. The integrability criteria of such systems are associated with the existence of recursion operators. A new non-autonomous KdV system is obtained and its recursion operator is given for all $N$. The examples for N=2 and N=3 are studied in detail. Some possible transformations are also discussed which map some systems to autonomous cases.Comment: Latex file (amssymb), 10 page

Turkey's response to the global economic crisis

Turkey was not affected by the financial crisis as much as the advanced economies and managed to rapidly exit the turmoil. The reasons behind the strong response and quick recovery of the Turkish economy were its low country risk and low currency risk premiums. This study shows the foundations of these low risk premiums and compares some measures of these risks of the Turkish economy with peer countries. Second, this paper demonstrates that all of Turkey’s economic sectors were very strong before the crisis and sustained this strength during the course of the crisis. Finally, it discusses the policies that have already been taken and planned to be taken by Turkey’s economic authorities. The government seems to be very determined in keeping fiscal discipline as tight as necessary while not being excessivefinancial crises, global economic crisis, Turkey, economic policies, financial markets