فهرست مطالب b. mozafari

Current and voltage signals' distortion caused by the fault in the power system has negative effects upon the operation of the protective devices. One of the influencing factors is the existence of the exponential DC which can significantly distort the signals and lead to a possible malfunction of the protective devices, especially distance and over-current relays. The main problem is the lack of clarity about this component due to the dependence of its time constant and initial amplitude to the configuration of the electrical grid, location and resistance of faulty point. This makes it hard to extract the main frequency phasors of the voltage and current. Considering the importance of a fast clearance of the fault, this paper offers a method for an effective and fast removal of the decaying-DC that employs a data window with a length that is equal to the half cycle of the main frequency, while the conventional methods mostly use data from one cycle or even more. The proposed method is based upon the extraction of the decaying-DC component's parameters. The efficiency of this method is compared to the conventional Fourier algorithm of Half-Cycle (HCFA) and the mimic filter plus the HCFA. The outcomes display that the proposed method presents a better efficiency from the point of view of the speed and the accuracy of convergence to the final results.

This paper proposes an advanced distribution automation planning problem in which emergency-based demand response plans are incorporated during service restoration process. The fitness function of this planning problem consists of various costs associated with fault occurrence in electric distribution systems consisting of the total yearly cost of customers’ interruptions, the total annualized investment cost of control and protection devices deployment, including sectionalizing switches, circuit breakers, and fuses and the total annual cost of performing emergency-based demand response programs in the service restoration process. Moreover, the customers’ behavior in participating in the service restoration process is also modeled through using an S-function. The proposed advanced distribution automation planning method is implemented on the fourth bus of the Roy Bilinton test system in order to evaluate its efficacy. The obtained results show that the reliability indices and the total cost of distribution automation are reduced by about 9% and 12% more than the published methods for distribution automation, respectively.

In a three-phase distribution system, due to unequal distribution of single-phase loads, load diversities, the different consumption patterns, and growing penetration of renewable energy resources in smart grids, the problem of unbalanced power flow becomes more challenging. In this paper, we propose a new innovative phase imbalance mitigation (PIM) scheme performed by smart meters. With aid of the proposed optimal phase assignment for 3-phase power distribution input feeders known as phase rearrangement (PR), Electrical storages (ES), and the Renewable energy sources (RES), smart meter owners are inspired to assist the distribution system operator (DSO) in diminishing the phase imbalance. This is achieved by employing a proposed connection point assignment system which has the flexibility of selecting the power input among the three phases and management of ESs and RESs.  We model this problem into a mixed integer linear program, where smart meter owners minimize their electricity bill. Simulation results confirm the proposed approach and show smart meter owners will save on their electricity bill and the DSO will get benefit by improving the power quality of the grid and significant decrements of the power flow imbalance.

Using a conservative stability analysis to design a time delay system controller usually cause a devaluation on the actuator performance. In addition, the results obtained considering deterministic stability criteria may not be reliable due to the existence of random delays. Whenever the feedback loop of a power system oscillation damping control system receives remote signals through communication networks, we face a POD system with random delays namely POD-RD system.  In this paper, a new design approach to promote the performance of a POD-RD control system is proposed based on the delay scheduling control signal method. This is a two-step method for implementation. In the first step assuming the average value of the communication random delays, the controller''''s parameters and also delay parameter of the control signal are determined as initial values by minimizing sperctral abscissa of the closed loop system. In the next step, to include impact of the communication random delays, a repetitive procedure is proposed to determine the optimal value of the delay parameter of the control signal and also the controller''''s parameters. The objective of the optimization model is to minimize the spectral abscissa and the defined second order moment. The feasibility of the proposed method is evaluated by doing a number of simulations on the standard four-machine test system.The results reveal that the method can make a robust performance in the studied system.