فصلنامه مهندسی و مدیریت انرژی
سال دوازدهم شماره 3 (پیاپی 45، پاییز 1401)

Congestion Risk Management is one of the most important subjects of Transmission management in deregulated power system and world electricity market, especially markets of zonal or local pricing in which Firm Transmission Rights (in other words Financial Transmission Rights) are the main elements. In this study, considering subjects of Financial Rights of Transmission Congestion, methods of optimum proposal of different Rights by participants of transmission rights second auction of electricity Market in short period (weekly) for Congestion Risk Management will analyzed. At the end, a proposed method in a typical network is tested and the numerical right values shown.

In the light of the emergence of smart grids, the functions associated with this type of grids in the blocks of the energy management system require the adoption of robust strategies in order to provide a higher level of control and protection. Under-frequency load shedding (UFLS) sheds load blocks when the frequency drop is below the threshold limit. In adaptive UFLS, in an advanced telecommunications platform, the main quantities of the system are measured at each hour and in real-time; besides, the optimal amount of load is shed according to frequency deviation. In this paper, an hourly framework using Mixed-Integer Linear Programming (MILP) is proposed for an optimal design of an adaptive UFLS in smart networks. The goal is to provide a more systematic adaptive UFLS that is less dependent on trial and error. Here, the under-frequency relay is set for each hour in regard to operating conditions and uncertainties resulting from contingencies, to renewable energy sourses (RES), and to load fluctuations at that hour. The simulations are performed on the IEEE 39-bus test system over a 24-hour time horizon.

Factorizing a system is one of the best ways to make a system intelligent. Factorizing the protection system, providing the right connecting agents, and transmitting the information faster and more reliably can improve the performance of a protection system and maintain system reliability against distributed generation resources. This study presents a new method for coordinating network protection system at the presence of distributed generation resources using smart electrical devices, control algorithms, and telecommu nications infrastructure. The proposed method is evaluated and validated on an experimental network simulated by ETAP software. also It provides a an opportunity to detect current fluctuations and network structure, which contribute to identify new protection modes using the information table as well as to determine the protection area. By using the information obtained from current fluctuations, the performance of the backup relay is improved.

In this paper, an optimal design for a surface-mounted permanent magnet synchronous generator (PMSG) with outer-rotor is presented to minimize manufacturing cost. The main contribution of this study is to determine new dimensions for surface-mounted permanent magnet (SMPM) that yields  more sinusoidal air gap flux density distribution;  that improves the induced voltage quality, and that reduces both cogging torque and torque ripple. For further investigation, four different plans have been considered for PMSG by combining distributed and concentrated windings with the conventional and proposed SMPM. For this purpose, an accurate model for PMSG is considered. Then, based on this model and intended objective function, design variables were optimized by using genetic algorithm. Afterward, simulation studies based on the finite element analysis (FEA) were carried out in order to validate the optimal plans. By comparing the results of four optimal plans, obtained from optimization process and FEA, we observed that the PMSG with the concentrated winding and proposed SMPM had higher efficiency, lower total volume, lower manufacturing cost, lower cogging torque, and lower torque ripple as compared with other plans. Thus, it can be considered a proper choice for direct-drive wind turbines.

In Inverters as one of the most important equipment of power systems have profoundly been developed in recent decades, and their performance has attracted researchers regarding the control and structures they enjoy. In this paper, an innovative symmetric and asymmetric topology is proposed for a multilevel inverter (MLI) in order to reduce the switch and the driver counts. Also, the number of conducting switches at each voltage level is low in this structure. These features result in lower conduction losses of switches. Besides, an accurate comparison with recently introduced multilevel inverters has been carried out to confirm the superiority of the proposed structure. For proving the suitable performance of the proposed MLI, a 21-level symmetric and 37-level asymmetric inverter containing 14 switches were designed and simulated in the MATLAB/Simulink environment. A laboratory prototype for each of these inverters was implemented as well. The experimental results finely verified the simulated results.

In Recent advances in renewable energy technologies as well as the restructuring of the electricity market have increased the use of renewable energy resources. The use of these energy sources has many benefits such as increasing reliability, improving power quality, and peak shaving. However, one of the main disadvantages of these energy sources is the islanding detection. The island mode occurs when the main grid is interrupted for any reason, and the part of the grid that contains distributed generation supplies local loads independently from the main grid. Unintentional islanding causes problems such as protective interference and damage to consumer equipment. As a result, the fast detection and disruption of the distributed generation is essential to prevent equipment damaging. This paper presents a new hybrid islanding detection method for distributed generation resources to activate the real power shift method in case the rate of frequency change, in the first stage, exceeds the threshold. Then, if by changing the real part of the DG output current, the voltage amplitude changed, the islanding event would be detected.  The proposed method is implemented and simulated in the Matlab/Simulink environment.  It was also investigated under various conditions such as load switching, motor starting, and multi-DG mode. The simulation results showed the performance of the proposed method in islanding detection in these conditions.

Transmission lines and transformers are the most important equipment of a power network, the outage of which can lead to cascading failure. This paper tries to identify those lines or transformers that cannot be prevented from being overloaded by operations such as load shedding or production decrease through considering a model of cascade outage simulation. Also, one of the risk assessment methods, called Failure Modes and Effects Analysis (FMEA) method, is used to identify the critical network lines and transformers known as initial events of cascading failures. This method through the evaluation of three criteria ofseverity, occurrence, and detection assesses and categorizes the risk priority number (RPN) of the combination of possible N-K (1). The proposed method was implemented in the IEEE 39-bus test system, and its results showed its accuracy compared to the other methods.

In the last decade, piezoelectric materials have received much attention for harvesting waste mechanical energy from surroundings. Piezoelectricity was first discovered in ceramic crystals. However, piezo-ceramics were toxic and fragile; therefore, polymeric-based piezo-materials were developed due to their excellent flexibility and biocompatibility. In this paper, polyvinylidene fluoride (PVDF) nanowires have been synthesized while employing aluminum oxide nanopores (AAO) template. The scanning of electron microscopy (SEM) images have been used to study the morphology of the nanowires. Nanogenerators, based on PVDF nanowires, have been fabricated to convert mechanical energy to electrical energy. A built- setup working with the frequency of 5Hz and impact force of 20N/m2 has been used to characterize the performance and efficiency of the nanogenerators.  The nanogenerators, developed in this study, have demonstrated a power output efficiency of 14%.

In this work, the role and utilization of gold metal nanoparticles on enhancing the performance of dye sensitized solar cells are studied. Dye sensitized solar cells were fabricated with the use of red tea as natural dye sensitizer. The gold nanoparticles were synthesized and functionalized with carboxyl group and then were used in the photoanode of the fabricated DSSCs. Operation of these cells in the presence of the nanoparticles was studied. The way of applying gold nanoparticles in photoanode is very important and optimized configuration of photoanode as the plasmonic paste was designed and their concentration (weight ratio of Au /TiO2), in photoanode was optimized. Due to the role of gold nanoparticles to improve the absorption of sunlight by the dye, the mass ratio of gold nanoparticles is an important factor in cell optimization. So that the concentration of gold nanoparticles doesn't prevent the adsorption of dye molecules on the surface of TiO2 and for 2 nm gold nanoparticles used in this study, this mass percentage was optimized as 0.143 wt% Au-TiO2.

The buffer layer is one of the main elements in the thin film solar cells, especially in the copper indium gallium selenide (CIGS) thin-film solar cells. The buffer layer increases the optical absorption and decreases the surface recombination, which in turn results in further absorption of carriers and the enhancement of the solar cell efficiency. In this paper, the cadmium sulfide (CdS) and cadmium selenide (CdSe) thin films were selected as buffer layers. Then, the effect of different combinations of these two buffer layers on the solar cell parameters such as JSC, VOC, FF, and η were investigated using Silvaco Atlas commercial software. The optimal condition and higher efficiency were achieved when the CdS and CdSe layers were close to the ZnO and CIGS layers respectively. It was found out that the selection of 40-nm thickness for cadmium sulfide and 10-nm thickness for cadmium selenide increased the efficiency of solar cell up to 25.19%. Also, the plotting of the energy band diagram illustrated that electrons and holes, in an optimal condition, moved easily without any potential barriers. This condition led to a significant increase in the solar cell efficiency.