A bilevel optimization approach to decide the feasibility of bookings in the European gas market

The European gas market is organized as a so-called entry-exit system with the main goal to decouple transport and trading. To this end, gas traders and the transmission system operator (TSO) sign so-called booking contracts that grant capacity rights to traders to inject or withdraw gas at certain nodes up to this capacity. On a day-ahead basis, traders then nominate the actual amount of gas within the previously booked capacities. By signing a booking contract, the TSO guarantees that all nominations within the booking bounds can be transported through the network. This results in a highly challenging mathematical problem. Using potential-based flows to model stationary gas physics, feasible bookings on passive networks, i.e., networks without controllable elements, have been characterized in the recent literature. In this paper, we consider networks with linearly modeled active elements such as compressors or control valves. Since these active elements allow the TSO to control the gas flow, the single-level approaches for passive networks from the literature are no longer applicable. We thus present a bilevel model to decide the feasibility of bookings in networks with active elements. While this model is well-defined for general active networks, we focus on the class of networks for which active elements do not lie on cycles. This assumption allows us to reformulate the original bilevel model such that the lower-level problem is linear for every given upper-level decision. Consequently, we derive several single-level reformulations for this case. Besides the classic Karush–Kuhn–Tucker reformulation, we obtain three problem-specific optimal-value-function reformulations. The latter also lead to novel characterizations of feasible bookings in networks with active elements that do not lie on cycles. We compare the performance of our methods by a case study based on data from the .

Designing on Optical Wireless Communication for 5G Mobile Applications

The emphasis of this paper is on designing 5G networks infrastructure, offering a better wireless and optical network segment transport scheme with domains for applications for mobile phones. Identify the appropriate set of power grid wireless (optical/optical) technologies) and processing modules needed to facilitate 5G mobile services in an energy-efficient a two-stage optimization framework and the premium way is suspected. A multi-objective method in the first iteration is for optimization, where reflects on the element of the transport network strives to jointly reduce the expenditures on investment of the 5G mobile network. This is done to determine the minimum mobile technologies for wireless and optical power grids. The second stage focuses on the branch of the web server and aims to define effective modules of processing to which 5G operational systems need to be distributed. The performances of the proposal are investigated using separate clustering algorithms, reasonable traffic statistics choices such as mm-wave and optical passive networks (PONs) for optical grid transport, fixed, and elastic networks in Bristol, UK, via a city-wide topology. To give more advantages to 5G applications, our paper proposed a 5G communication using optical wireless technology.

Zaštita tronamotajnog energetskog transformatora zasnovana na faznoj komparaciji struja

This paper presents a new algorithm for three-winding transformer protection against internal short circuits. The algorithm is based on the application of the digital phase comparison of currents measured at the primary, secondary and tertiary terminals of the power transformer. The applied digital phase comparison does not calculate the angle between the two currents compared in phase, but uses the method of integration of the product of two signals within one basic semi-period of the signals. In order to provide selective protection in the case where the power transformer has only one of its three windings connected to the active network and the other two windings feeding passive networks, an overcurrent function has been added to the digital phase comparator. The paper shows that the application of the new algorithm can successfully detect the internal faults of the three-winding transformer and ensure timely tripping of protection. The signals obtained by computer simulations were used to verify the operation of the proposed algorithm. The algorithm and test results are given in the paper. Index Terms- power system protection, power transformer, digital phase comparison, fault discrimination.

Synthesis of Fractional-Order Biquadratic Immittance Functions

Passive network synthesis, as an important part of circuit and system theory, has been well developed in integer-order circuits. With the development of fractional-order calculus and fractional-order elements, the problem of using fractional-order passive networks to realize fractional-order immittance functions has drawn much attention. In this paper, the realization of a fractional-order biquadratic immittance function is considered. First, the form of a fractional-order biquadratic function and some theorems that could promote later research are introduced. Second, a detailed study for the realization of a fractional-order biquadratic immittance function is shown. Finally, through summarizing the realizability conditions of each network, we have obtained the scope of fractional biquadratic impedance functions that can be realized by this paper.