نشریه تحقیقات نوین در سیستم های قدرت هوشمند
سال دهم شماره 3 (پیاپی 27، پاییز 1400)

Currently, renewable power plants based on photovoltaic farms are considered as main sources of energy production which have been rapidly growing. However, changes in weather conditions are one of the issues facing this energy conversion system to provide the required power for the consumer. An efficient controller can appropriately control and improve the dynamic performance of the island microgrid based on the photovoltaic system. In this paper, a perturbation and observation method based on optimal fuzzy control is proposed to provide the required energy for the microgrid. In this regard, partial changes in the proportional and integral constants during the climate changes are calculated to ensure the convergence at the desired point. In order to find the desired parameters of the fuzzy system membership functions, a non-dominated sorting genetic algorithm is used. Then, the optimal duty cycle signal is injected into the boost converter. To verify and validate the performance of the proposed controller, a comparison is also made with the conventional observation and perturbation strategy. Also, different radiation conditions are considered for the under study photovoltaic system. Modeling of photovoltaic system and proposed control system has been performed by MATLAB / Simulink software. Finally, the simulation results show that the speed and accuracy of the maximum power point tracking by the proposed control system has been significantly improved.

The issue of unit commitment (UC) is one of the most important issues in the electricity market, and with the smartening and restructuring of networks which its goals and variables have undergone changes. In this paper, solving and modeling the problem of unit commitment by considering smart networks is proposed. As we know, in smart grids, there are new issues such as demand side management and energy storage systems (batteries) as well as new goals such as reducing the environmental pollution of the units that must be considered. In this paper, the issue of unit commitment with demand side management modeling along with optimal charging and discharging of battery storage system with the aim of minimizing the economic costs of units and batteries and environmental pollution is presented. The proposed model is a Mixed Integer Linear Programming (MILP) model that is solved using powerful commercial software such as Gurobi and guarantees optimal global solutions. The proposed model is implemented on two standard IEEE 6 and 118 bus networks, the results of which show the efficiency of the proposed model.

Security Constrained Unit Commitment is a practical way for the system operator to plan and operate in real time. Considering the transmission system and security constraints can lead to different responses to load distribution. One of the solutions to solve problems in the circuit of units with large-scale security constraints is to use the Benders analysis method. But strengthening the way the problem is written puts a big difference on the speed of solution and the computational volume the purpose of this research is existing N-K constraint might lead possibility to ignore some other constraints and minimize the calculation. In the proposed model, studied faults are identified in a loop, and power flow control are proceeded by adding necessary constraints. In each step, transmission system constrains are defined, and in case any overloading occurs, relating constrain is going to be activated in the following step. This strategy defines necessary constraints in each hour and line. Also, sensitive network lines which are overloaded due to lines subjected to fault exit could be defined. Considering the mentioned issues, the importance of Unit Commitment and optimal solution proposition in large scale, in the thesis we are going to analyze the unit commitment by using line outage distribution factor and its combination with N-K security constraint.  The calculation volume in large scale could be decreased by applying this strategy, thus, the computation is fast-speed. On the other hand, all the computations and comparisons are applied on IEEE 118-bus network using GAMS software and MATPOWER tool to analyze power distribution factors. A repeating constraint identification loop is employed to implement N-K constraint, and results show the loop reduces the computation time. In the proposed method, the sensitive lines and their operation conditions are identified that the appropriate response can be achieved in the fault conditions.

High pressure insulators are exposed to different environmental and climatic conditions. The interaction of environmental conditions and insulation pollution makes the insulation of the insulators themselves a suitable substrate for conducting current and leaving its effects on power systems. Knowledge of potential distribution and electric field of high voltage equipment is an important aspect of the design, operation and performance of high pressure insulators. This can be useful for detecting defects in insulation. The purpose of this study is to show the behavior of contaminated insulators under voltage. Therefore, electric field simulation and potential distribution in the vicinity of different insulation levels were discussed. Insulators are modeled in two ways: 2D, 3D and Multiphysics Comsol software analysis, which is one of the best software used in modeling for finite elements. Finally, the results of potential distribution and electric field along the insulation in different contaminated and clean conditions, which are simulated using different conductivity values, are shown.

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.

One of the most applicable relays in protecting the power system is distance and overcurrent relays. In transmission and distribution networks, protection is usually performed by distance protection, and overcurrent protection is used as a backup for distance protection. In the present study, a new approach was provided to coordinate distance and overcurrent relays using pickup current, time adjustment coefficient, and overcurrent relay characteristics to delay these relays as backup for distance relays. It is possible to adjust the second zone of the distance relays' operating time with a fixed and normal value using instantaneous operation relays with changes in coordination constraints. In the proposed method, the coordination problem was solved using GA algorithm. A protection coordination index is then provided to evaluate distributed generation sources' impact on the protection coordination of distance and overcurrent relays. A new method was proposed to obtain the maximum injection capacity under coordination constraints using MATLAB and DIGSILENT software's parallel performance. The proposed method was implemented in IEEE 9 and 39 bus sample networks. Finally, the obtained results were compared and evaluated.