Heresh Seyedi

This paper presents a new scenario based method to prevent voltage instability under wind and load uncertainties considering correlation among wind turbines and loads. The correlated load and wind scenarios are generated based on the correlation matrix as well as Normal and Rayleigh probability density functions. Electrical distances are used to generate the correlation matrix among loads. Then, the preventive voltage instability problem is formulated two-stage stochastic programming problem. Control facilities include rescheduled active and reactive power of generation units, load shedding and demand response. The considered control facilities are classified into two different categories based on the stage of decision making. These categories are named here-and-now and wait-and-see. Demand response, load shedding and reactive power output of power plants are wait-and-see facilities, whereas active power of power plants is considered as here-and-now facility. The proposed method is tested on the standard IEEE 118-bus test system. Comprehensive analyses are carried out demonstrating the impact of uncertainties and correlations, as realistic load and wind modeling, on the problem.

ABSTRACT SUMMARY The most common protection scheme for synchronous generators against stator windings fault is the differential protection scheme. In this paper, a new voltage-controlled overcurrent protection scheme is proposed as a backup protection method for the differential protection method. This scheme is designed to operate in conditions in which differential protection fails to do so and is implemented by fuzzy controllers. The fuzzy controllers set the plug setting of the overcurrent relay. In the proposed method, the fault conditions can be determined regardless of variations of voltage and the current of terminal in different operating states of the synchronous generator. This is realized by measuring not only the terminal voltages and currents of the generator, which are usually used in conventional voltage-controlled overcurrent protection schemes but also other variables that promote the accuracy of the proposed scheme. For presenting this protection method, a synchronous generator with internal fault model is used. The fault model is based on the direct-phase representation that uses the conventional and readily available machine data. Simulations for various types of stator faults of synchronous generator validate the proposed method. Copyright © 2013 John Wiley & Sons, Ltd.

Abstract-- This paper presents an optimal phasor measurement units (PMUs) placement algorithm for the purpose of power system observability and also increasing the performance of secondary voltage control scheme. The optimal placement problem (OPP) is formulated such that to ...

As power demand is increased, power generation and especially distributed generation (DG) are being developed. Therefore, power distribution systems become increasingly complicated and short circuit level in distribution grids is being augmented. Thereby, installation of a superconducting fault current limiter (SFCL) is a logical solution to decrease the fault current level in a distribution network. Preventing distribution system degradation by high fault currents, lower equipment ratings, and economic issues are the advantages of SFCL in distribution grids. However, SFCL installation causes delayed operation of the existing overcurrent protection and requires recoordination of the relays. In addition, disconnecting the SFCL from the distribution circuit due to maintenance leads to miscoordination between the overcurrent relays. In this research work, a genetic algorithm (GA) is used to achieve optimal protection coordination in the presence of both SFCL and DG. Furthermore, the uncertainty associated with the connection status of SFCL and DGs, which are reflected in the protection coordination, is investigated in detail. Moreover, various overcurrent relay characteristics, such as long-time inverse, extremely inverse, very inverse, and normally inverse, are used in a test power system, and remarkable computation results will be shown and discussed in the next parts of the paper.

In this research, an adaptive Continuous Wavelet Transform based overcurrent protection for smart grids is proposed to enhance the overcurrent protection performance encountering High Impedance Fault and Current Transformer saturation, which are extremely complex phenomena and their impacts often cause mis-coordination or mal-operation. The proposed algorithm samples three phase current waveforms and imports them to CWT to extract high frequency coefficients. Afterwards, sum of absolute values of the coefficients, Scoef, is calculated for each sample during the last cycle. Meanwhile, several simulations related to HIFs with different impedances and CT saturations with different severities are executed and the fault currents and sum of absolute values of the coefficients are achieved and saved in the relay memory as (X, Y) coordinates of points (IL-fault, SL-coef), named "learning data". Thereafter, each Scoef is imported to the X-Y plane and, consequently, occurrence of HIF or CT saturation is detected and the real fault current is estimated by both nonlinear interpolation and Extreme Learning Machine approaches. Subsequently, new Time Dial Setting and Ipickup of the relays are computed and reloaded. Security, dependability and sensitivity of proposed adaptive protection method are confirmed by numerous simulation studies.