Ramezan Ali Naghizadeh

Parameter identification of Jiles‐Atherton model using SFLA

Purpose – The purpose of this paper is to implement a simple, fast and accurate heuristic method for parameter determination of Jiles‐Atherton (JA) hysteresis model for representing magnetization in electrical steel sheets. The performance of the method is validated using measured data and comparison with previous methods.Design/methodology/approach – JA model requires five parameters to represent the hysteretic behavior of ferromagnetic materials. In order to determine these parameters, measured hysteresis loop is used here to calculate a fitness function which is defined by comparing the measured and simulated magnetization loops. This fitness function is minimized by optimization algorithms.Findings – In total, four different measured hysteresis loops are studied in this paper. Each optimization algorithm is executed 50 times to investigate the convergence, speed, and accuracy of six methods. All methods begin with the same randomly generated initial parameters. Physical boundaries are used for paramet...

Optimal Surge Arrester Parameter Estimation Using a PSO-Based Multiobjective Approach

In this paper, an improved self-adaptive particle swarm optimization (ISAPSO) algorithm is developed for estimating the best set of surge arrester model parameters. The purpose is to minimize the relative error between the calculated and manufacturers measured residual voltage peak values for lightning, switching, and steep-front impulses. An objective function, which generalizes the model parameters for all impulse current types with different peak levels, is proposed. This objective function is the summation of three subfunctions that in each of them one type of impulse current with different current peak levels is considered. An efficient multiobjective approach is also applied along with the presented ISAPSO method. The proposed algorithm finds different sets of Pareto-optimal nondominated solutions for the objective functions. A fuzzy clustering technique is used to restrain the size of the repository within the desired limit. The proposed method is applied for a 150-kV TRIDELTA metal-oxide surge arrester in order to demonstrate its accuracy and effectiveness.

A Simple and Unified Method to Model HVDC Links and FACTS Devices in DC Load Flow

The DC load flow is a rapid and approximate solution method for the determination of lines active power flows in power systems. In this paper, the HVDC (High Voltage Direct Current) links and FACTS (Flexible AC Transmission Systems) devices have been modeled in the DC load flow analysis. In order to evaluate the performance of the proposed method, the proposed DC load flow results have been compared with the AC or AC-DC load flow results of DIgSILENT software. It is shown that the proposed DC load flow is accurate enough for power system studies.

Islanding Detection in Unbalanced Distribution Systems with Doubly Fed Induction Generator Based Distributed Generation Using Wavelet Transform

Abstract—A passive islanding-detection technique is proposed in this article for a distribution network with a distributed generation system including a doubly fed induction generator. This method is based on the processing of the measured voltage signals of the distributed generation connecting bus using discrete wavelet transform. Different types of disturbances including faults (single-phase, two-phase, and three-phase) and power quality disturbances (capacitor switching, load switching, and motor starting) are used to discriminate from islanding conditions. A wind turbine equipped with a doubly fed induction generator is considered as the distributed generation source in an unbalanced distribution system. The studied system is simulated with high level of detail in PSCAD/EMTDC software for the purpose of this work. The results of implementing the proposed method verify the high accuracy, reliability, and speed of the proposed islanding-detection approach even with small non-detection zone and the presence of high levels of noise in measured voltage signals.

Estimating the Parameters of Dynamic Model of Drum Type Boilers Using Heat Balance Data as an Educational Procedure

The procedure for deriving the parameters of drum type boilers dynamic model for long-term transient stability studies by use of heat balance data is presented in this paper. The main purpose of the work is to exhibit a regular procedure using available heat balance data of the steam plant boiler and thermodynamic properties of saturated steam and water, to be suitable for educational purposes. The parameters are shown to be in reasonable range. The model response to step changes with and without control loop is simulated and discussed as well. Furthermore, a practical scenario of the studied steam power plant is presented and the measured data are compared with simulation results.

A combinatorial approach based on wavelet transform and Hidden Markov Models in differential relaying of power transformers

This paper proposed a new classification method based on hidden Markov models (HMM) to discriminate between magnetizing inrush current and internal faults in transformers. HMM is a pattern recognizer which can classify signals based on waveform and characteristics. Training data-set is achieved by application of k-means clustering approach. First some principle characteristic of the signals is extracted to reduce the computational time of HMM training procedure and enhance discrimination accuracy, and then two HMM blocks is trained for these two kinds of signals. This procedure makes the scheme insensitive to irrelevant disturbances such as CT saturation. Based on the proposed algorithm a high speed differential relaying could be performed in a quarter of a cycle. Small computation requirement is the advantage of this method which can be applied for real time applications. The suitable performance of this method is demonstrated by simulation of different faults and switching conditions on a power transformer. Since the discrimination method is done with probabilistic characteristics of signals without application of any deterministic index, more reliable and accurate classification is achieved. It provides a high operating sensitivity for internal faults and remains stable for inrush currents of the power transformers.

An Adaptive Approach for Simulation of Inrush Current in Three-phase Transformers Considering Hysteresis Effects

Abstract This article proposes a novel adaptive approach for accurate simulation of inrush currents in three-phase power transformers. The proposed technique is based on using artificial neural networks to update inverse Jiles–Atherton hysteresis model parameters during inrush current transients. The required parameters for training artificial neural networks are obtained using particle swarm optimization based on measured inrush current waveforms. The results show that the proposed technique can be used for accurate simulation of this phenomenon in three-phase power transformers. Inrush current measurements on a three-phase three-leg transformer are used for artificial neural network training and verification of the results.

Optimum design of high voltage bushings by rational Bézier curves

Purpose – The purpose of this paper is to propose a new approach for designing different parts of a high voltage bushing. It also aims to consider technical and economical criteria for the optimum solution of the design problem.Design/methodology/approach – A novel method for finding the optimal contours of different elements of high voltage bushings, including ceramic insulator, electrode, and flange angle is presented. The rational Bezier curves are used for defining the surface of the insulators and conductors of the equipment. Then, these curves are optimally adjusted to obtain an appropriate techno‐economical solution. The utilized optimization method is the improved bacterial foraging algorithm (BFA) with variable step sizes. In the design procedure, two‐dimensional finite element method (2D FEM) is used to calculate the performance parameters in each step of the design procedure. In order to evaluate the performance of the proposed algorithm, optimal design of different elements of a 110 kV bushing...