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Under-voltage load shedding is an important measurement to maintain the voltage stability in power systems. In this paper, a new combined index is proposed for under-voltage load shedding. The proposed index is weighted combination of importance, sensitivity and value of loads. This is of paramount importance, since three vital factors such as importance of load, sensitivity of minimum eigenvalue of load flow Jacobian respect to load and the amount of loads are considered for optimal under-voltage load shedding. The algorithm accounts constraints not only in present operating condition but also for predicted next interval load. The proposed method is applied on IEEE 14-bus test system. This paper formulates the optimal under-voltage load shedding problem for power system as a Nonlinear Programming (NLP), and it solves the proposed problem using Generalized Algebraic Modeling Systems (GAMS) software package with CONOPT solver. Results have been compared with those researches based on sensitivity analysis. The results showed effectiveness of proposed index. This proposed index can be used in selecting candidate buses in different power system problems. [ABSTRACT FROM AUTHOR]

This paper includes a novice technique for locating single line to ground fault in electrical transmission network. Validation of the proposed algorithm is demonstrated using MATLAB Simulink. Simpower system tool box is used for the modeling of smart meter, transmission lines and single line to ground fault (1L-G). A novel method is proposed to countercheck whether the fault has occurred really or not. Data related to 1l-G fault has been collected at 220kV Lonikand substation and analyzed exclusively during the visit at Kalkitech (top manufacturing company of Intelligent Electronic Devices (IEDs) in Bangalore, Karnataka, India). Effect of harmonics on fault current measurement using smart meter is elaborated. Advancements in communication technology are illustrated from asset management perspective. [ABSTRACT FROM AUTHOR]

Interline power flow controller (IPFC) is a concept of AC flexible control of the transmission system (FACTS), with the ability to series compensation and power flow management in multi lines of a post power. Out of all FACTS devices, interline power flow converter (IPFC) is considered to be most flexible, powerful and versatile. IPFC has the capability of compensating multi-transmission line. The proper placement of interline power flow controller (IPFC) can improve the transmission line congestion problem to a great extent. This paper proposes the optimal location of the IPFC in electrical power systems, using the particle swarm optimization algorithm. Expression of sample figure and analysis of the sample system show that IPFC is effective to minimize the power losses in the power system. [ABSTRACT FROM AUTHOR]

This article presents a network feeder reconfiguration in balanced distribution networks using Multi Verse Optimization (MVO) to optimize the total network power losses and reduce emissions by means of step by step switching. Reconfiguration is a considerable manner of altering the power flows through the lines from the main substation to load ends, while maintaining radial structure. The main objective of this paper is to solve feeder reconfiguration problem to reduce the total line losses and emission reduction for an open loop distribution system. MVO is a population based method to resolve the network reconfiguration problem. A precise power flow solution is applied and the objective is formulated. A nature inspired Multi Verse Optimization is utilized to restructure the power distribution system and identify the optimal tie switches for lower line losses in the distribution network. The reduction of resistive losses leads to reduction of emissions. The suggested MVO method has carried out on two standard 16-node and 69-node distribution systems for normal load and overload conditions and results show the performance of the anticipated MVO method. The final outcomes prove a significant reduction in real power losses and emissions. [ABSTRACT FROM AUTHOR]

In this paper, the results of a finite element analysis are carried out on a new stator geometry of a three phase longitudinal flux Linear Switched Reluctance Motor (LSRM). In the new geometry, pole shoes are affixed to the stator poles. Static and dynamic characteristics for the proposed structure have been highlighted. Motor performance for variable load conditions is discussed. The 2-Dimensional (2-D) finite element analysis (FEA) and the experimental results of this paper prove that LSRMs are one of the strong candidates for linear propulsion drives. [ABSTRACT FROM AUTHOR]

This paper presents a study about of a fuzzy Controlled STATCOM, which can be applied for mitigation of the voltage flicker in a distribution system. The voltage flicker is produced by a large variable load absorbing continuously changing currents such as an arc furnace. The DSTATCOM includes a voltage-sourced PWM inverter and its control system. The control strategy of the DSTATCOM plays an important role in maintaining the voltage flicker. Here, the DSTATCOM controller is designed with two types of controllers, linear proportional-integral (PI) and nonlinear fuzzy logic. The simulation of the DSTATCOM with 3MVar reactive power on a 25 KV distribution network is carried out in MATLAB/SIMULINK software. At the end of the paper, fuzzy controllers were evaluated by comparing its performance with the PI controllers. It is observed that the fuzzy controllers are very superior in mitigating the voltage flicker. [ABSTRACT FROM AUTHOR]

Because of the great benefits of distributed generation (DG) resources, such as inexhaustible and nonpolluting, they have more influence in the power industry, especially in distributed networks. DGs such as photovoltaic panels, wind turbines, fuel cells and micro gas turbines, etc. are going to be used in demand side of power systems. Such DGs can decrease power losses if they are placed properly in the distribution networks. In this paper presents ant colony algorithm for optimal placement and sizing of DGs in radial distribution networks for the purpose of cost minimization. The objective function embraces the cost of power losses and installed DGs cost. By applying the proposed method, the economic cost and power losses are decreased to a considerable degree while enhancing the voltage profile. Algorithm to optimize the objective function written in Matlab and simulation results are investigated on a real case study from a section of Tehran distribution network consisting of 13 buses. [ABSTRACT FROM AUTHOR]

Nowadays, due to increased consumption and operation of electric power systems close to their stability boundaries, power systems may become unstable during severe disturbances. So, it is very important to determine the stability margin under different conditions. In this paper, the static voltage stability of an interconnected power system considering load and generation uncertainties is evaluated using probabilistic power flow. The Monte Carlo Simulation method is used to generate the probabilistic power flow scenarios. Then, the expected static voltage stability index and probability of stability for all of the PQ buses are obtained. Also, the standard deviations of the stability indexes are calculated. Finally, the critical PQ nodes are determined under given disturbance. The study has been carried out on 39-Bus New England and 118-bus IEEE test systems and results are presented. [ABSTRACT FROM AUTHOR]

Reactive power dispatch plays a key role in secure and economic operation of power systems. Optimal reactive power dispatch (ORPD) is a non-linear optimization problem which includes both continues and discrete variables. Due to complex characteristics, heuristic and evolutionary based optimization approaches have become effective tools to solve the ORPD problem. In this paper, a new optimization approach based on improved differential evolution (IDE) has been proposed to solve the ORPD problem. IDE is an improved version of differential evolution optimization algorithm in which new solutions are produced in respect to global best solution. In the proposed approach, IDE determines the optimal combination of control variables including generator voltages, transformer taps and setting of VAR compensation devices to obtain minimum real power losses. In order to demonstrate the applicability and efficiency of the proposed IDE based approach, it has been tested on the IEEE 14 and 57-bus test systems and obtained results are compared with those obtained using other existing methods. Simulation results show that the proposed approach is superior to the other existing methods. [ABSTRACT FROM AUTHOR]

In this paper, an auto tuned load frequency controller based on Fuzzy Wavelet Neural Network (FWNN) and Shuffled Frog Leaping Algorithm (SFLA) is employed to damp the deviations of frequency and tie line power due to the load disturbances in a multi-area power system. Optimal tuning of the FWNN parameters is very important to improve the design performance and achieve a satisfactory level of robustness, for a particular operation. In this work, a new systematic tuning method is developed for designing the FWNN load frequency controller. For this, the error between the desired system output and output of control object is employed to tune the FWNN parameters. Tuning rule is accomplished based on SFLA approach by minimizing a combination of control error. To show the effectiveness of the proposed method, some numerical results are presented for a two area power system considering governor saturation and the results are compared to the obtained results by a classic PI controller and a fuzzy load frequency controller. Moreover, the robustness of the proposed method is tested against change of parameters. The simulation studies show that the designed controller by proposed method has a very desirable dynamic performance, better operation and improved system parameters such as settling time and step response rise time even when the system parameters change. [ABSTRACT FROM AUTHOR]

There are relatively few literatures about Flexible AC Transmission Systems (FACTS) in reliability aspects, particularly in composite system reliability evaluation. Reliability of the power system could be studied by some indices that help to compare power system under different conditions from reliability point of view. The actual benefits of the FACTS can be quantitatively estimated using suitable models and techniques. Corrective control as an alternative for the system reinforcement is proposed in this paper as a suitable way to ease the challenges related to building new transmission lines or reconstruction of power grid. Static Var Compensator (SVC) as a member of FACTS family has been used as corrective control. A test case with three scenarios is considered for comparing the effect of SVC on the reliability of the power system. It will be seen that the correct SVC replacement has a great influence on the reliability indices of power grid and losses could be diminished. [ABSTRACT FROM AUTHOR]

This paper incorporates the SSSC FACTS device in optimal power flow solutions to enhance the performance of the power systems. The particle swarm optimization is used for solving the optimal power flow problem for steady-state studies. The effectiveness of the proposed approach was tested on IEEE 14-bus and IEEE 30-bus systems with SSSC FACTS device. Results show that the proposed PSO algorithm gives better solution to enhance the system performance with SSSC device compared to without SSSC device. [ABSTRACT FROM AUTHOR]

The growing requirement to the clean and renewable energy has led to the rapid development of wind power systems all over the world. With increasing use of wind power in power systems, impact of the wind generators on subsynchronous resonance (SSR) is going more important. The SSR is a well-known phenomenon in a series compensated power systems which can be mitigated with series or parallel flexible ac transmission systems (FACTS) devices. In this paper, wind turbines and steam turbines have been used as a hybrid energy production system. For damping the SSR, thyristor controlled series capacitor (TCSC) as a series FACT devise and unified power flow controller (UPFC) as a series-parallel FACT device have been used. In order to have an optimal control on pitch angle in high speed of wind, a novel method using imperialist competitive algorithm (ICA) has been used. Furthermore, supplementary controllers for UPFC and TCSC have been design and adaptive neuro fuzzy inference system (ANFIS) and fuzzy logic damping controllers (FLDC) are added to these FACTS devises to mitigate the SSR. Finally, the results of two FACTS devises have been compared. Furthermore, the results obtained from imperialist competitive algorithm (ICA) are compared with PID controller optimized by Particle Swarm Optimization (PSO) algorithm. [ABSTRACT FROM AUTHOR]

In this paper, voltage sag is compensated by the DVR (Dynamic Voltage Restorer) in distribution systems. This device is applied between the sensitive load and the supply in order to inject voltage in series to correct the voltage sag. Subsequently, all the other various DVR compensation techniques in the distribution system are explained. Due to the restriction of the energy storage in DVR's capacitors, it is essential to minimize the active power injected by the DVR. Thus, a minimum active power injection method is proposed to compensate the voltage sag. Performance of this method is evaluated under balanced and unbalance voltage sag in a distribution system. [ABSTRACT FROM AUTHOR]

The increased use of nonlinear devices in the industry has resulted in the direct increase of harmonic distortion in power systems during these last years. Active filter systems are proposed to mitigate current harmonics generated by nonlinear loads. The conventional scheme based on a two-level voltage source inverter controlled by a hysteresis controller has several disadvantages and cannot be used for medium or high-power applications. To overcome these drawbacks and improve the APF performance, there's a great tendency to use multilevel inverters controlled by intelligent controllers. Three level (NPC) inverter is one of the most widely used topologies in various industrial applications such as machine drives and power factor compensators. On the other hand, artificial neural networks are under study and investigation in other power electronics applications. In order to gain the advantages of the three-level inverter and artificial neural networks and to reduce the complexity of classical control schemes, a new active power filter configuration controlled by two MLPNN (Multi-Layer Perceptron Neural Network) is proposed in this paper. The first ANN is used to replace the PWM current controller, and the second one to maintain a constant dc link voltage across the capacitors and compensate the inverter power losses. The performance of the global system, including power and control circuits is evaluated by Matlab-Simulink and SimPowerSystem Toolbox simulation. The obtained results confirm the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Uncontrolled energization of large power transformers may result in magnetizing inrush current of high amplitude and switching over-voltages. The most effective method for the limitation of the switching over-voltages is controlled switching since the magnitudes of the produced transients are strongly dependent on the closing instants of the switch. We introduce a harmonic index that its minimum value is corresponding to the best-case switching time. Also, this paper presents an Artificial Neural Network (ANN)-based approach to estimate the optimum switching instants for real time applications. In the proposed ANN, second order Levenberg-Marquardt method is used to train the multilayer perceptron. ANN training is performed based on equivalent circuit parameters of the network. Thus, trained ANN is applicable to every studied system. To verify the effectiveness of the proposed index and accuracy of the ANN-based approach, two case studies are presented and demonstrated. [ABSTRACT FROM AUTHOR]

The problem of Economic Dispatch (ED) in electric power systems is to schedule the power output for each committed generator unit such that the operating cost is minimized and simultaneously, the customer load demand is matched and the generator operating limits are met. Nowadays with increasing awareness of environmental pollution caused by burning of fossil fuels, emission of pollutants is also a criterion for economic dispatch of the plants. The environmental objective of generation dispatch is to minimize the total environmental cost or the total pollutant emission. This paper presents an efficient and simple approach for solving the emission constrained economic dispatch problem using the proposed Hybrid Particle Swarm Optimization Technique (HPSO). The convergence and usefulness of the proposed HPSO is demonstrated through its application to a test system. The computational results reveal that the proposed algorithm has an excellent convergence characteristic and has the potential to apply to other power system problems. [ABSTRACT FROM AUTHOR]

In this paper the power flow control at power systems in the presence of distributed generation is analyzed. The work proposes use of Unified power flow controller (UPFC) to control the power flow at the load bus by Main supply in coordination with DG source. This work shows that using UPFC leads to the reduction of the oscillation power and voltage at the time of three phase fault in the system. The studies are performed based on the well known software, MATLAB/SIMULINK Simulation results show that the stability and effectiveness of the applied operation of DG source in coordination with the main utility can be achieved by using UPFC. [ABSTRACT FROM AUTHOR]

In this paper a neuro-fuzzy controller is proposed to enhance transient stability and increase critical clearing time (CCT) in the static synchronous compensator (STATCOM). For achieving this idea, first the controller is designed based on the Lyapunov energy function. In order to avoid complexity of computation and overcome system uncertainty a neuro-fuzzy controller is proposed. In this controller, Neural network determines the system rules and membership functions. In order to design a neural network and its training patterns, the energy function controller is used under various system conditions. This controller has learning abilities due to its robust fuzzy controller and neural network. Simulation results on the single-machine infinite-bus (SMIB) show that the neuro-fuzzy controller damps electromechanical oscillations and increases the critical clearing time. [ABSTRACT FROM AUTHOR]