In this paper, a bi‐level power management strategy is presented for an active distribution network (ADN) in the presence of virtual power plant (VPP). In the proposed strategy, VPP contains renewable energy source (RES), energy storage system (ESS) and electric vehicles (EVs) parking lot coordinated with VPP operator (VPPO), and there is a coordinated framework between VPPO and distribution system operator. The proposed power management strategy (PMS) is considered in the context of the bi‐level optimization problem. In the first level, the optimal harmonic power flow formulation of the ADN is considered by minimizing the summation of energy cost, voltage deviation function and voltage THD% as a normalized objective function. In the second level, the VPP is modeled according to the framework of day‐ahead energy and ancillary services markets. In the next step, the linear format of the proposed non‐linear original problem is obtained with an optimal solution and low calculation burden. Also, the Karush‐Kuhn‐Tucker condition is used to convert the proposed bi‐level PMS approach to a single‐level model, and the scenariobased stochastic programming models the uncertainty of load, energy price, RES power, and EVs demand. Finally, the proposed strategy is applied on the 33‐bus distribution network using GAMS software.
Ever-increasing consumption of electrical energy has forced extension of power networks to large areas. This would raise reliability and stability problems of power networks. Hence, there is a serious need to work on protection arrangements and relays behavior for solving these problems. By suitable configuration of protection systems and using correct protection functions, negative effects of undesirable faults in power system will be decreased. In this paper, an algorithm is proposed to enhance the performance of differential relays based on the fuzzy logic systems. The algorithm is employed for the protection of short transmission lines against internal faults with/without resistance. By selecting the best stability characteristics based on fuzzy logic systems, the possibility of protection relays' malfunction will be negligible. In this algorithm, sensitivity, reliability and speed of the relay performance are preserved at suitable levels. Considerable external faults which can saturate current transformers (CTs) have been taken to account in this algorithm. This study purpose is to present an algorithm based on the fuzzy logic, which can select the best slopes for stability characteristics of a differential relay during various conditions. The presented algorithm performance has been analyzed by PSCAD/EMTDC software and compared to conventional methods. The results of fuzzy adaptive protection performance testing prove that the proposed algorithm remains fully immune to current transformer saturation during external faults. The other advantage of this algorithm bases on the fact that the scheme does not need to detect CT saturation, it processes the proposed criteria signals independently of the situation.
In this paper, a CVD method is used for the synthesis of multi-wall carbon nanotubes (MWCNT) which have been purified and functionalized. The approach consists of thermal oxidation and subsequent chemical oxidation. According to TEM images, the CNTs have a diameter about 20-30 nm. We synthesized the FePt nanoparticles on the surface of the functionalized carbon nanotubes through a polyol process. The synthesized FePt nanoparticles have the chemicallydisordered face-centered cubic (fcc) structure with superparamagnetic behavior and with a size of about 2.5 nm. To achieve phase transition from fcc to ordered structure (fct-L1 0 phase), high-temperature annealing under a reducing atmosphere (90% Ar + 10% H 2) is required. The CNTs as a substrate prevent the aggregation of particles during thermal treatment. The FePt nanoparticles after phase transition have ferromagnetic behavior. Furthermore, they have finite size with an average about 5.6 nm and their coercivity reaches to 5.1 KOe at 700°C. We characterized the structure, composition and magnetic properties of FePt/CNT by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM).
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