فهرست مطالب مجید گندمکار

In traditional generation systems, about 25% of energy is wasted, and the presence of distributed energy resources (DER) such as photovoltaic, wind turbines, fuel cell, and the combined heat and power can reduce fuel consumption, pollution, and transmission losses. In this paper, a complete energy management framework in a microgrid is proposed by considering the constraints using Improved Shuffled Frog Leaping Algorithm, in which the exact share of energy production for different units is determined. The proposed scheme is used to select the best arrangement of DERs in the microgrid, the output of which is to determine the number and optimal location of DERs in several bus-bars. Then, the independent system operator determines the quantity of energy exchange and consumption by considering load distribution constraints. Boilers and CHPs have also been used to maintain the balance between the production of thermal power by energy sources and thermal demands. In addition, the Demand Response Program has been used with the aim of smoothing the load curve and of reducing the operating costs. Finally, the proposed method has been implemented and simulated using MATLAB software on a two standards 69-and- 118-bus IEEE system. The comparison of the results with other algorithms showed the accuracy and superiority of the proposed method from the point of view of reducing operating costs.

In addition to the many advantages of Distributed Generation (DG) for the distribution networks, they change the direction and increase the level of fault current. These changes may cause the loss of protection coordination of reclosers and fuses in distribution networks. Usually, the operation time of reclosers is determined by two main settings, TDS and IP, but two other parameters (A and B), which are defined by the standards of traditional reclosers, are also influential on the operation time of reclosers. These two parameters can be modified in digital reclosers. In this article, these two characteristics are optimized with TDS and IP to restore protection coordination. For this purpose, first, the location and the size of the DGs are specified, after that to alleviate the effects of the DGs, the location and the impedance of FCLs are optimized by a multi-objective optimization function to reduce the loss, improve voltage profile, and reduce the effects of changes in the feeders’ fault current while DGs are connected to the distribution network. Then, to restore the protection coordination, and to reduce the operating time of the protection equipment, fuse, and recloser, the parameters A, B, TDS, and IP are optimized using a multi-function optimization. To validate the proposed approach, the IEEE 33-bus network in the presence of synchronous DGs and resistive SFCL has been simulated in DIgSILENT software.

Standard PID controllers are one of the most desirable controllers for industrial automation and the most widely used control in feedback systems. However, linear controllers have limitations that represent tation controllers can be used to overcome these limitations. In this paper, a robust reset control based on optimal output feedback to control a robot with two degrees of freedom. In general, the behavior of reset controllers is similar to that of linear controllers, in other words, they are easy to implement. In this regard, in this paper, by introducing a special combination control called robust reset output feedback control, the disadvantages of the linear controller are eliminated and its main purpose is to reduce overexposure and increase the response speed and better stability of the controlled system. Therefore, this paper introduces a systematic method for reset optimal output feedback controller. To do this, an optimal output feedback controller is first designed without the reset action, so that the poles of the closed-loop system are located in a predefined area. This area is selected to ensure the stability of the exponential and the arrival time of the closed loop in a finite time. Then, the reset value at reset times is designed to minimize a cost-effective function for better performance. In this paper, for the first time, the reset value is specified only with the system output information and then the stability of the system will be guaranteed. The robot used in this article is a practical and industrial example that has two arms and two joints with separate control capability. The position and behavior of the arms based on the governing equations and mathematical relations indicate its direct effect on each other. Finally, to prove the proposed design, numerical simulation will be performed using Matlab software and a comparison between the proposed controller and a similar controller will be performed.

In this paper, the protection coordination for Digital dual-setting directional overcurrent relays (DS-DOCR) in the presence of renewable energy sources and energy storage system in the conditions of maximum and minimum fault current in the distribution network is investigated. The proposed scheme minimizes the total operating time of the relays to achieve fast protection coordination in DS-DOCR relays. In addition, to increase the flexibility in the DS-DOCR settings, the permitted range for all relay parameters such as A, B, pickup current (IP), and time dial setting (TDS) is explained in both forward and backward directions. In the proposed scheme, the operating results of DS-DOCR relays on the IEEE 9-bus distribution network in the presence of maximum penetration of photovoltaic sources (PV), wind and energy storage systems (ESSs), in maximum and minimum fault current conditions are investigated. Simulation of the study method is done in DIgSILENT Power Factory software. The numerical results indicate that the proposed solution algorithm has ideally provided the optimal values ​​of the DS-DOCR relays setting parameters, and is capable of achieving reliable and fast protection coordination.

This paper presents the system stability-constrianted optimal protection coordination (SSCOPC) as stochastic problem in the microgrid with grid-connected and islanded operation modes, including renewable energy sources (RESs) and energy storage systems (ESSs). To regulate optimally the dual setting overcurrent relays (DSORs) and to selectin the reactance size of fault current limiter (FCL), the system minimizes the total relays operation time in the primary and backup protection modes. Also, it is subject to the limits of the coordination time interval (CTI), DSORs setting parameters, FCL size, and microgrid stability in the fault condition. Generally, the microgrid includes RESs and ESSs; thus, the proposed SSCOPC needs a daily operation of microgrid as stochastic model to calculate network variables before fault occurrence. Hence, s this situation minimizes the microgrid operation cost and load shedding cost of islanded microgid which are subjected to optimal power flow equations in the presence of RESs and ESSswhile considering the uncertainty of the load and its generation. Therefore, by applying the proposed problem on the 9 and 32 bus microgrid, solving the problem by the Crow Search Algorithm (CSA), and selecting optimal size of RESs and ESSs, based on operation and protection coordination indices, the proposed SSCOPC can obtain a fast protection solution that considers system stability in faulty conditions.

Due to the progress of renewable energy technologies and the intention of energy policymakers to use these clean and cheap resources, many studies have focused on ways to take advantage of these energies. Limitations, such as low capacity, output power uncertainty, and sustainability problems, make the use of distributed energy resources costly and difficult. Among distributed generation resources, renewable energy resources such as wind energy and solar energy are more environmentally friendly and are used more than other technologies. Despite the many advantages of these resources, their output power depends on such factors as wind speed and solar intensity, which cannot be accurately predicted. For this reason, the infiltration[MSH1]  of high levels of these resources into power systems increases system uncertainty and can reduce reliability while system reliability is very important for power system designers and operators, as well as energy consumers. To solve these problems, a new concept, named virtual power plant, is proposed. A virtual power plant is a collection of distributed energy resources that come together to participate in the market. Virtual power plants can efficiently coordinate, aggregate, and manage different distributed energy resources such as distributed generation, energy storage systems, and controllable loads. These plants are flexible agents for a range of distributed energy sources that can be used in wholesale markets to provide services to system operators. The energy management system is the heart of a virtual power plant that coordinates the flow of power from generators, controllable loads, and energy storage devices. This paper proposes a full model for optimal planning of a virtual power plant if uncertainties of distributed generation sources such as wind and solar energy, as well as electrical vehicles, are considered. To prevent the negative effects of the presence of electric vehicles on electricity networks, especially in virtual power plants, it is necessary to charge these vehicles in a controlled manner and with careful planning. In addition, the demand response whose modeling is based on price-based demand response for non-users and encouragement-based for electric vehicles is optimized on two scenarios, and a 32-bus network is studied. The main goal of the research is to maximize the profit of the virtual power plant for the simultaneous use of load response and electric vehicles with the capability of connecting to the grid.

Power system protection at transmission and distribution levels based on overcurrent relays is essential based on their properties such as detection, stability, high speed, backup and error correction accuracy. Since distributed generation sources are connected to the power grid, they not only increase the short circuit level of the grid, but also disrupt the set point of main and backup relays, which will interrupt the healthy areas of the grid. In order to maintain the safety and stability of the network and to avoid increasing the power rating of the existing equipment, Superconducting Fault Current Limiter (SFCL) devices are utilized to significantly reduce the short circuit current at its primary cycles. However using of SFCLs, may lead to inadequate relay performance and lack of short circuit current detection. In order to solve the above problems, this paper presents a SFCL model with resistive structure and coupling inductance, while increasing the fault impedance path and reducing short circuit current, optimally. Then shielding synchronization between main relays and their near and far back-ups are achieved. Finally proposed objective function is minimized using the improved particle swarm optimization algorithm and three case studies will be performed. The simulation results represent the superiority of the proposed method in resolving the error and eliminating disturbance between the relays at the shortest possible time.

Reliability of a system is the ability of a system to do prospected duties in future and the probability of desirable operation for doing predetermined duties. Power system elements failures data are the main data of reliability assessment in the network. Determining antiseptic parameters is the goal of reliability assessment by using system history data. These parameters help to recognize week points of the system. In other words، the goal of reliability assessment is operation improving and decreasing of the failures and power outages. This paper is developed to assess reliability indices of Bakhtar Regional Electricity Company up to 1393 and the improving methods and their effects on the reliability indices in this network. DIgSILENT Power Factory software is employed for simulation. Simulation results show the positive effect of improving methods in reliability indices of Bakhtar Regional Electricity Company.