Showing 6 results for Smart Grid
M. Khalilzadeh, A. Fereidunian,
Volume 12, Issue 4 (12-2016)
Abstract
In this paper, a stochastic approach is proposed for reliability assessment of bidirectional DC-DC converters, including the fault-tolerant ones. This type of converters can be used in a smart DC grid, feeding DC loads such as home appliances and plug-in hybrid electric vehicles (PHEVs). The reliability of bidirectional DC-DC converters is of such an importance, due to the key role of the expected increasingly utilization of DC grids in modern Smart Grid. Markov processes are suggested for reliability modeling and consequently calculating the expected effective lifetime of bidirectional converters. A three-leg bidirectional interleaved converter using data of Toyota Prius 2012 hybrid electric vehicle is used as a case study. Besides, the influence of environment and ambient temperature on converter lifetime is studied. The impact of modeling the reliability of the converter and adding reliability constraints on the technical design procedure of the converter is also investigated. In order to investigate the effect of leg increase on the lifetime of the converter, single leg to five-leg interleave DC-DC converters are studied considering economical aspect and the results are extrapolated for six and seven-leg converters. The proposed method could be generalized so that the number of legs and input and output capacitors could be an arbitrary number.
A. S. Hoshyarzadeh, B. Zaker, A. A. Khodadoost Arani, G. B. Gharehpetian,
Volume 14, Issue 3 (9-2018)
Abstract
Recently, smart grids have been considered as one of the vital elements in upgrading current power systems to a system with more reliability and efficiency. Distributed generation is necessary for most of these new networks. Indeed, in all cases that DGs are used in distribution systems, protection coordination failures may occur in multiple configurations of smart grids using DGs. In different configurations, there are various fault currents that can lead to protection failure. In this study, an optimal DG locating and Thyristor-Controlled Impedance (TCI) sizing of resistive, inductive, and capacitive type is proposed for distribution systems to prevent considerable changes in fault currents due to different modes of the smart grid. This problem is nonlinear constrained programming (NLP) and the genetic algorithm is utilized for the optimization. This optimization is applied to the IEEE 33-bus and IEEE 69-bus standard distribution systems. Optimum DG location and TCI sizing has carried out in steady fault currents in the grid-connected mode of these practical networks. Simulation results verify that the proposed method is effective for minimizing the protection coordination failure in such distribution networks.
R. Mohammadi, H. Rajabi Mashhadi,
Volume 15, Issue 1 (3-2019)
Abstract
Distribution system reliability programs are usually based on improvement of average reliability indices. They have weakness in terms of distinguishing between reliability of different customers that may prefer different level of reliability. This paper proposes a new framework based on game theory to accommodate customers’ reliability requests in distribution system reliability provision. To do this, distribution reliability equations are developed so that it is recognized how game theory is suitable for this purpose and why conventional methods could not provide customer reliability requirements appropriately. It would be shown that customer participation in distribution system reliability provision can make conflict of interest and leads to a competition between customers. So, in this paper a game theoretic approach is designed to model possible strategic behavior of customers in distribution system reliability provision. The results show that by implementing the proposed model, distribution utilities would have the capability to respond to customers’ reliability requirements, such that it is beneficial for both utility and customers.
O. Honarfar, A. Karimi,
Volume 16, Issue 3 (9-2020)
Abstract
Distribution load flow (DLF) calculation is one of the most important tools in distribution networks. DLF tools must be able to perform fast calculations in real-time studies at the presence of distributed generators (DGs) in a smart grid environment even in conditions of change in the network topology. In this paper, a new method for DLF in radial active distribution networks is proposed. The method performs a very fast DLF using zooming algorithm associated with a fast-decoupled reactive power compensation (ZAFDRC) technique, not in all of the buses of the grid, causes to reduce the solution time, which is the most important issue in the real-time studies. The proposed method is based on the zooming algorithm and does not require to calculate the bus-injection to branch-current (BIBC) matrix which reduces the computational burden and helps to decrease the solution time. The method is tested on the IEEE 69-bus systems as a balanced network and the IEEE 123-bus as a very unbalanced system. The results confirm the high accuracy and high speed of the proposed method.
Z. Kazemi, A. A. Safavi,
Volume 16, Issue 3 (9-2020)
Abstract
Kalman filtering has been widely considered for dynamic state estimation in smart grids. Despite its unique merits, the Kalman Filter (KF)-based dynamic state estimation can be undesirably influenced by cyber adversarial attacks that can potentially be launched against the communication links in the Cyber-Physical System (CPS). To enhance the security of KF-based state estimation, in this paper, the basic KF-based method is enhanced by incorporating the dynamics of the attack vector into the system state-space model using an observer-based preprocessing stage. The proposed technique not only immunizes the state estimation against cyber-attacks but also effectively handles the issues relevant to the modeling uncertainties and measurement noises/errors. The effectiveness of the proposed approach is demonstrated by detailed mathematical analysis and testing it on two well-known IEEE cyber-physical test systems.
A. Bahmanyar, H. Borhani-Bahabadi, S. Jamali,
Volume 16, Issue 3 (9-2020)
Abstract
To realize the self-healing concept of smart grids, an accurate and reliable fault locator is a prerequisite. This paper presents a new fault location method for active power distribution networks which is based on measured voltage sag and use of whale optimization algorithm (WOA). The fault induced voltage sag depends on the fault location and resistance. Therefore, the fault location can be found by investigation of voltage sags recorded throughout the distribution network. However, this approach requires a considerable effort to check all possible fault location and resistance values to find the correct solution. In this paper, an improved version of the WOA is proposed to find the fault location as an optimization problem. This optimization technique employs a number of agents (whales) to search for a bunch of fish in the optimal position, i.e. the fault location and its resistance. The method is applicable to different distribution network configurations. The accuracy of the method is verified by simulation tests on a distribution feeder and comparative analysis with two other deterministic methods reported in the literature. The simulation results indicate that the proposed optimized method gives more accurate and reliable results.
