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This article investigates the operation of a microgrid system through a novel control scheme. The proposed microgrid system employs various autonomous generation systems, including photovoltaic, wind, a diesel engine, a fuel cell, an aqua electrolyzer, and a battery. A simulation model for this microgrid system was developed using MATLAB/SIMULINK (The MathWorks, Natick, Massachusetts, USA). A proportion-integral-derivative control scheme is employed, and the parameters of proportion-integral-derivative controllers for various controllable sources are tuned with a firefly algorithm. This is done using a new proposed weighted goal attainment method for achieving improved and fault-tolerant operation. The proposed control scheme shows better performance over the classical proportion-integral-derivative and bacterial foraging–proportion-integral-derivative controller in both transient and steady-state conditions. The firefly algorithm–proportion-integral-derivative controller also shows stronger robustness properties against system perturbations, disturbances, and faults than that with other controller structures. The robustness is a highly desirable property in such a scenario since many components of the microgrid may be switched on/off or may run at lower/higher power output at different time instants. [ABSTRACT FROM AUTHOR]

Abstract—A new fault phase selection method for transmission lines is proposed in this article. First, fault phase selection factors are constructed based on the relationship between the fault current of each phase and the fault current difference of the other two phases at a relay point. By analyzing different characteristics of fault phase selection factors in the case of different fault types, fault phase selection criteria are proposed. Simulation results show that fast and accurate selection of the fault phase can be achieved within a period cycle after fault occurs. Also, it is verified that the method bears a high sensitivity to all types of faults and is immune to the impact of fault resistance, fault inception angle, fault location, load current, and high-voltage DC lines, which makes it relatively reliable. Even when a developing fault occurs, good selectivity is secure with this method. Furthermore, the method provides sufficient sensitivity for phase selection on the weak-infeed side and parallel lines. [ABSTRACT FROM PUBLISHER]

Abstract—Integration of distributed generation with utility network demands satisfactory operation of an islanding detection scheme, as it can otherwise lead to such problems such enhancement in non-detection zone, out-of-phase reclosing, personnel safety, and degradation of power quality. This article presents a new islanding detection scheme based on the rate of change of impedance (dz/dt) of each phase. To calculatedz/dt, phasor computation is carried out using a half-cycle modified discrete Fourier transform algorithm. Test data are generated using the PSCAD/EMTDC software package (HVDC Research Center, Inc., Manitoba). Various islanding conditions have been simulated by disconnecting the main circuit breaker with different values of active and reactive power mismatch. At the same time, different non-islanding conditions have also been simulated through switching (ON/OFF) of load, energization/de-energization of medium transmission lines, short-circuit on an adjacent feeder, and switching (ON/OFF) of the transformer and capacitor bank in the network. The simulation results indicate that the proposed scheme is capable of providing effective discrimination between islanding and non-islanding conditions. The proposed scheme is able to detect islanding conditions within a half-cycle from event inception. [ABSTRACT FROM PUBLISHER]

This article presents an adaptive distance relay setting for a power transmission network connecting more than one wind farm. The ideal trip characteristics of the distance relay is greatly affected in the presence of complex mutual coupling of transmission lines, as the apparent impedance is significantly affected. Similarly, the reach setting of the relay for the lines connecting wind farms is significantly affected, as the relaying voltage fluctuates continuously. Thus, the proposed study focuses on developing an adaptive relay setting for a transmission network including more than one wind farm and considering variations in operating conditions of wind farms and mutual coupling of transmission lines together. The proposed relay algorithm is extensively tested on two-terminal as well as multi-terminal power networks with wide variations in operating parameters. The performance testing of the proposed adaptive relay characteristics for faults and faults during power swing indicates the potential ability of the approach in handling distance relaying in a transmission system. [ABSTRACT FROM AUTHOR]

Optimal capacitor placement as a precious and significant strategy to improve the performance of the power systems has attracted much attention in recent years. However, the non-linear and discrete nature of the optimal capacitor placement problem is a big barrier in front of the traditional optimization methods for global search. Therefore, this article proposes a powerful optimization technique based adaptive modified honey bee mating optimization algorithm to solve the optimal capacitor placement problem effectively. The proposed method consists of two sub-modification methods to let each solution choose the modification methods which best fit its situation. Also, in order to preserve the random search ability of the algorithm, the idea of the roulette wheel mechanism is employed in the selection process. The proposed algorithm can overcome the main shortcomings in the traditional honey bee mating optimization algorithm by using both local and global search schemes. Therefore, the problem investigated is formulated in a multi-objective framework optimizing the total power losses, voltage deviation, and cost of both power losses and capacitor investment simultaneously. As the result of the conflicting behavior of the objective functions, the idea of a non-dominated solution, called the Pareto solution, is employed to find the set of optimal solutions. During the optimization process, the set of Pareto solutions found is stored in an external memory called a repository. In order to avoid excessive growth of the repository, a fuzzy-based clustering technique is applied to the problem. The feasibility and superiority of the proposed method is tested through three standard test systems. [ABSTRACT FROM AUTHOR]