نشریه فناوری های نوین مهندسی برق در سیستم انرژی سبز
پیاپی 1 (بهار 1401)

Considering environmental issues and the use of green energy resources has led to the increase of Distributed Generations (DGs) connection to electric power grid. Beside many benefits, these generations impose challenges to the electric system. Two main challenges investigated in this article are related to the impact of DGs on the Protective Devices (PDs) coordination and the transient stability of these resources at the fault time incidence. As for Synchronous-based Distributed Generations (SBDGs), the challenge of protection coordination arises from the injection current rate of these generations under fault circumstances and the transient stability challenge is due to the low inertia constant. In proposed method, by shifting the relay characteristic curve downwards and repositioning the curve below the Critical Clearing Time (CCT), not only the coordination of the PDs will be improved, but also the instability of SBDGs will be eliminated. This paper presents a modified time-current-voltage characteristic curve for the overcurrent relays. The simulation results done by ETAP software confirm the effective performance of the proposed method.

Most Micro-Sources (MSs) are interfaced to a Micro-Grid (MG) using power electronics converters. Therefore, a MG can be envisioned as a group of parallel converters. A well-known method to control a group of parallel converters in the decentralized control structure in a MG is to use frequency and voltage droop characteristics. A problem associated with conventional droop characteristics is that reactive power is not always properly shared among MSs which may lead to converter overloading. The nature of conventional droop characteristics is linear. Therefore, these characteristics do not have a sufficient degree of freedom to function properly in nonlinear conditions, such as the occurrence of short circuit faults. Most of proposed methods in the literature are limited to specific MG structures or need extensive information of grid. For this purpose, in this paper, a new power control strategy based on a decentralized method for autonomous micro-grid consisting of voltage source inverters is presented. The control strategy based on voltage and frequency droop control methods. In the proposed method, conventional droop characteristics are corrected by using virtual impedance loop to adjusting the y-intercept of conventional curves. The proposed approach also improves voltage regulation both under normal micro-grid conditions and when faults occur.

Nowadays, the presence of distributed generations has made traditional networks into dynamic state. Current flow fluctuation, increment of fault current and as a result loss of coordination and also error in relays operation in safe sections in the network have been among the problems due to using these generations. Finding solution for these problems has always been challenging over the years. The purpose of this paper is to suggest a new solution in the study of protection system operation in electrical energy networks by using intelligent electronic equipment with communication protocols at the level of distribution networks. In recent years, telecommunications platform and intelligent equipment usage has provided a platform that has been able to show its effectiveness against network sudden changes. Multi-Agent system is the name of this communication platform that has been able to pioneer the beginning of a fundamental change in the design of protection systems in electrical energy networks by using a new scheme. These systems have shown that they have not been without problems and in some cases have caused problems for the network. In the proposed approach, the multilayer structure of the multi-agent system will be broken and the surfaces will be independent of each other. Unlike the typical multi-agent system protection method, protection settings at the moment of fault are not calculated for the entire network. This problem, which has not been seen in previous methods, also removes a large load density from the central unit and increases the operating speed and reliability of the protection system.

In today's power systems, grid parameters are usually monitored by controlling agents to ensure the quality of produced electrical energy. Uninterrupted service to the network customers and continuous power supply may be disrupted through various disturbances. On this basis, the network requires a completely reliable, fast, and precise protection system. The protection of distribution networks is controlled by overcurrent equipment, which is complicated with increasing penetration of distributed generation resources due to change in the direction of current. This paper investigates how these resources affect the coordinated performance of the network protection system and proposes a new solution with the aim of restoration and fixing the miscoordination problem. The proposed method could be implemented on traditional overcurrent protection equipment while being able to meet the challenge of protection coordination with the lowest cost. The simulation results verify the effectiveness of the proposed algorithm.

MDS matrices have a crucial role in the cryptography and coding theory. MDS matrices are used as the diffusion layer in cryptosystems as well as in the construction of linear codes with the maximum error correction capability. On the one hand, the entries of MDS matrices are elements of finite fields. On the other hand, it is a major issue to implement finite fields in the lightweight cryptography. Therefore, to use MDS matrices in the lightweight cryptography, these matrices are first converted to binary matrices and then implemented using heuristics algorithms. In this paper, a method to implement binary matrices with low-cost XOR is proposed and then using the proposed method, a heuristics algorithm for implementing MDS matrices is introduced. The structure of the proposed heuristics algorithm is based on the assumption that let A be a binary matrix (or the binary form of an MDS matrix). First, using a random-iterative method, we obtain a list S from a binary matrix A. Then, based on the list S, we construct a binary matrix B. Next, we find a relation between the implementations of A and B. In other words, using the implementation of the matrix B, we get a low-cost implementation for the matrix A. In the structure of the proposed heuristics algorithm, one of the familiar SLP algorithms called Paar is applied.

Existing double-ended fault location methods in transmission systems can be applied only to single or ‎double-circuit transmission lines. They conventionally use different abc-domain or sequence network ‎equivalent circuits for different fault types. Furthermore, some methods do not consider shunt ‎capacitances of the line, inductive or capacitive coupling between different phases, and (or) the cases of ‎untransposed lines, simultaneously. In this paper, a comprehensive and fast phasor-based double-ended ‎fault location method is proposed which can be used for N-circuit transmission lines. For this purpose, first, ‎a matrix-vector equivalent circuit (MVEC) is proposed that leads to a unique formulation for fault location ‎problem regardless of fault type, number of line circuits, being transposed or untransposed while it ‎considers inductive and capacitive coupling between the phases. Then, based on the MVEC formulation, a ‎bi-level algorithm is suggested that quickly finds the fault location, despite its iterative nature. The ‎proposed method does not need to know impedances of local and remote end sources. Furthermore, its ‎accuracy is not sensitive to fault impedance. Various case studies in terms of fault types, fault impedances, ‎and distances from the measurement side in the presence of noise reveal the accuracy and applicability of ‎the proposed fault location method.‎

One of the most important concerns for power system operators is how to execute the restoration process after having a blackout. In doing so, the parallel restoration is the most common method in which the desired islands are first formed and then the load of each section is restored separately at the same time. In the next step, the islands must be synchronized with having a minimum standing phase angle (SPA) between them. To do this, an optimal multi-objective scheme is defined in this paper in order to coordinate both load restoration and SPA reduction problems. The objective functions of the proposed model are the minimization of the static phase angle and the energy not supplied in which the desired constraints are also considered. For optimization process the teaching and learning optimization algorithm (TLBO) is used as a proposed technique and compared with some other intelligent algorithms. The simulations are performed by creating a connection between MATLAB software and DIGSILENT. The results obtained on the IEEE 39-bus power system show the efficiency of the proposed model.