There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Planning of an islanded hybrid system (IHS) with different sources and storages to supply clean, flexible, and highly reliable energy at consumption sites is of high importance. To this end, this paper presents the design of an IHS with a wind turbine, photovoltaic, diesel generator, and stationary (battery) and mobile (electrical vehicles) energy storage systems (ESS). The proposed method includes a multi-objective optimization to minimize the total cost of construction, maintenance, and operation of sources and ESSs within the IHS and the emission level of the system using two separate objective functions. The problem is subject to operational and planning constraints of sources and ESSs and power. Employing the Pareto optimization technique based on the e-constraint method forms a single-objective optimization problem for the proposed design. The problem involves uncertainties of load, renewable energy, and energy demand of mobile ESSs and has a nonlinear form. Adaptive robust optimization based on a hybrid meta-heuristic algorithm that utilizes a combination of the sine-cosine algorithm (SCA) and crow search algorithm (CSA) is proposed to achieve an optimal robust structure for the suggested scheme. In this scheme, operation model of the mobile storage systems in the IHS considering the uncertainties prediction errors and its model using HMA-based ARO besides adopting the HMA to achieve a unique optimal solution are among the novelties of this research. Eventually, considering the climate data and energy consumption of a region in Rafsanjan, Iran, capabilities of the method in extracting a robust IHS for sources and ESSs are validated depending on optimal economic and environmental conditions. The HMA succeeds to reach an optimal solution with an SD of 0.92% in the final response and this underlines its capability in achieving approximate conditions of unique responsiveness. The proposed scheme with proper planning and operation of sources and storages in the form of a HIS finds optimal values for economic and environmental conditions so that the difference between pollution and cost values from its minimum values at the compromise point is roughly 22%. For 17% uncertainty parameters prediction errors, the scheme obtains a robust structure for the IHS.

Robust multi-objective optimal design of islanded hybrid system with renewable and diesel sources/stationary and mobile energy storage systems

Earth faults occur frequently in power distribution systems and they are usually accompanied by an arc. This is a big hazard to the power distribution systems. Effective early detection is difficult to achieve using conventional methods, which brings inconvenience to fault location and maintenance. In order to solve this problem, a sensitive triggering algorithm should be equipped in the detection device. By analyzing the zero-sequence voltage under normal conditions and fault conditions, a discrete wavelet transform-based triggering algorithm is proposed in this paper. A great number of waveforms simulated by the PSCAD/EMTDC software are used to test the algorithm and two other traditional algorithms, and the results are analyzed and compared. In addition, the curves recorded in the physical simulation systems and the field power distribution systems are input into the proposed algorithm to test its adaptability. For testing whether the algorithm could achieve real-time triggering, a device is designed to carry the algorithm program. These experiments show that the proposed algorithm has high reliability and it can meet the needs of real-time monitoring.

Discrete Wavelet Transform-Based Triggering Method for Single-Phase Earth Fault in Power Distribution Systems

Optimal coordination of directional overcurrent relays in complex distribution networks using sine cosine algorithm

This paper presents a new hybrid algorithm of Harris hawks’ optimization with sequential quadratic programming (HHO-SQP) for optimal coordination of directional overcurrent relays to find optimal relays settings. The SQP procedure is employed in the hybrid algorism as a local search mechanism to enhance the performance of the original HHO method. The optimization problem is described based on a developed objective function as a non-linear and highly constrained optimization problem to minimize the total operating time for primary relays at the same time of maximizing the backup relays operating time. The developed objective function is subject to some constraints related to the coordination process including the absence of any miss coordination between primary and backup relays. The performance of the proposed algorithm based on the new objective function is implemented for two different test systems. The results of the proposed algorithm is compared with those obtained from other recent meta-heuristic techniques. The results show that the new hybrid algorithm outperforms the recently published meta-heuristic algorithms.

Hybrid Harris hawks optimization with sequential quadratic programming for optimal coordination of directional overcurrent relays incorporating distributed generation

High-impedance faults (HIFs) in electrical power distribution systems produce a very random, non-linear and low-magnitude fault current. The conventional overcurrent (OC) relaying-based distribution system protection schemes find difficulty in detecting such low-current HIFs. In this study, a simple two criteria-based protection scheme is proposed for detection and isolation of HIFs in multi-feeder radial distribution systems. It utilises one-cycle sum of superimposed components of residual voltage for HIF detection and the maximum value of one-cycle sum of superimposed components of negative-sequence current for faulted feeder identification. The performance of the proposed scheme is evaluated for a wide variety of possible test cases by generating data through power systems computer-aided design/electro-magnetic transient design and control software. Results clearly show that the proposed scheme can assist conventional OC relay for detection and isolation of HIFs in distribution systems with any grounding connections in a more reliable and faster way.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-smt.2017.0231

High-impedance fault detection in electrical power distribution systems using moving sum approach

Distribution generation (DG) based on renewable energy sources at the distribution voltage level is gaining popularity among utilities and consumers due to numerous technical, economical and environmental benefits. The concept of microgrids (MGs) has been proposed as an attractive alternative to integrate large number of DGs with distribution systems. MGs can operate either in islanded or grid connected mode of operation. The bidirectional power flow and the significant variation in the fault current levels during grid connected and islanded mode of operation imposes significant challenges in designing a proper protection scheme for such system. To solve this problem, recently a number of alternative solutions have been proposed in the technical literature. This paper addresses the protection problems of MGs in detail and critically reviews the existing schemes proposed for MG protection. The most up to date relevant options are described and categorized into specific groups. Finally, a comparative assessment is carried out in which relative advantages and disadvantages of each protection strategy are evaluated.

An extensive review on the state-of-art on microgrid protection

Conventional overcurrent relaying based protection scheme has limitation to detect high impedance faults in distribution systems due to random, nonlinear and low magnitude fault currents. The problem becomes further complicated in presence of distributed generators in distribution systems due to bidirectional flow of power and reduction of fault current contribution from the main grid. This paper presents a one-cycle sum of superimposed component of residual voltage based method to detect high impedance faults in distribution systems integrated with distributed generators. The performance of the scheme is evaluated for high impedance faults at different locations of a 7-node radial distribution system integrated with distributed generators. The scheme is also tested for different non-fault events like capacitor switching and load switching, which often produce similar characteristics as that of high impedance faults. PSCAD/EMTDC software is used for generating data for different test cases and the method is implemented using Matlab software. Results clearly show that the proposed scheme can assist conventional overcurrent relay in detecting high impedance faults in distribution systems integrated with distributed generators in a more reliable and faster way.

A novel high impedance fault detection technique in distribution systems with distributed generators

In this paper, modelling of an asymmetrical micro-ring resonator and its performance as an optical filter and optical sensor is analysed. Quadruple asymmetrical optical micro-ring resonator (QAOMRR) is mathematically modelled in Z-domain using delay line signal processing technique. The transmittance of the configuration is calculated using signal flow graph method. Vernier principle method is applied to achieve larger free spectral range (FSR). Also, the proposed QAOMRR in silicon-on-insulator (SOI) platform is used for biochemical sensing. The proposed QAOMRR offers a FSR of 3.155 THZ and Q- factor of 3875 as well as provide significant shift in resonant wavelength whenever any different analyte is present in biomolecules. Field investigation of the proposed QAOMRR is done using Finite Difference Time Domain (FDTD) method. The directional couplers are designed using FDTD simulations. The proposed method will be extremely useful for modelling analysis and design of different micro optical asymmetrical ring resonator configurations.

Kumari Sarwagya

Papers

High-impedance fault detection in electrical power distribution systems using moving sum approach

Optimal coordination of directional overcurrent relays in complex distribution networks using sine cosine algorithm

An extensive review on the state-of-art on microgrid protection

A novel high impedance fault detection technique in distribution systems with distributed generators

Modelling and Analysis of Quadruple Asymmetrical Optical Micro-Ring Resonator for Biosensing Application