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IEEE 802.11ax is the standard for the new generation WiFi networks. In this paper, we formulate the problem of joint access point (AP) placement and power-channel-resource unit assignment for 802.11ax-based dense WiFi. The objective is to minimize the number of APs. Two quality-of-service (QoS) requirements are to be fulfilled: (1) a two-tier throughput requirement which ensures that the throughput of each station is good enough, and (2) a fault tolerance requirement which ensures that the stations could still use WiFi even when some APs fail. We prove that this problem is NP-hard. To tackle this problem, we first develop an analytic model to derive the throughput of each station under the OFDMA mechanism and a widely used interference model. We then design a heuristic algorithm to find high-quality solutions with polynomial time complexity. Simulation results under both fixed-user and mobile-user cases show that: (1) when the area is small (50 x 50 m2), our algorithm gives the optimal solutions; when the area is larger (80 x 60 m2), our algorithm can reduce the number of APs by 34.9-87.7% as compared to the Random and Greedy algorithms. (2) Our algorithm can always get feasible solutions that fulfill the QoS requirements.

Terahertz (THz) band spans the frequencies lying between 0.1 and 10 THz and represents the gap between millimeter waves and Infrared bands. THz will play an influential role in mitigating the spectrum resources shortage to meet the exponential growth of services and wireless devices. Standardization activities are being carried out to regulate the THz bands exploitation under the IEEE 802.15 standardization project. Despite the generous bandwidth, THz communications suffer from high pathloss and attenuation due to Molecular Absorption. As such, THz systems need to use extra power, suitable antennas, and enhanced signal processing and communication techniques to compensate for different signal attenuation sources. In this paper, we propose a new operation mode for the IEEE standard 802.15 to save the power transmission requirement while achieving the required data rate. Hence, less battery or antenna size are needed to support the same communication link quality. To this end, we optimize the power, modulation scheme, and channel allocation to minimize the total transmitted power keeping a minimum quality-of-service. Moreover, the design captures the effect of different weather conditions that are we detail their impact on the channel attenuation.

Unfortunately, due to omissions in the proof of the paper, Figs. 10(c), 16, 22, 27(a) and (b), and 30 have some mistakes that confuse the normal reading. Due to omissions in proofreading, Fig. 8 appears in the layout of Fig. 10(c), which makes Fig. 10(c) ambiguous and interferes with the normal reading. In addition, the statement of “ZVS-DCM” in Figs. 16, 22, 27(a) and (b), and 30 all need to be replaced with “ZVS-TPCM,” otherwise it will be inconsistent with the statement in the main text. Finally, the spelling of the TPCM lacks a “T” in the caption of Fig. 30 in [1]. The corrected figures are shown here. (Figure Presented).

Purposes The purpose of this paper is to identify on the instantaneous electrical power basis of a nonsinusoidal periodic current three-phase asymmetric system, active and reactive positive, negative and zero sequence powers, taking into account higher harmonics. The main power theories, including those embodied in the IEEE 1459 standard, do not allow to evaluate some of power components. Design/methodology/approach A well-known fact is that the three-phase AC system total power with the symmetry of currents and voltages is constant. It corresponds to the electrical energy transfer process in a DC system. In this case, the electrical energy transmission can be taken as high quality. It has been established that the components of active and reactive powers are because of the product of current and voltage of unidirectional sequences. The orthogonal components of the oscillating power are because of the product of the voltage and current components of different sequences, with the exception of the zero sequence. Findings For an unbalanced nonsinusoidal mode of a three-phase system, the components of instantaneous power were defined, corresponding to the active and reactive positive and negative and zero sequences powers with the selection of the fundamental and higher harmonics. The active and reactive powers of sequences were divided into two categories – consumed and generated. Originality/value It is proposed to use the ratio of “interfere” power RMS value to the total power RMS value to assess the instantaneous power distortion.

It is a major concern for utility companies, power engineers, and consumers everywhere that power outages, voltage fluctuations, and power system breakdowns may occur. The voltage profile and power quality of the system as a whole will benefit from a more refined reactive power adjustment. This study investigates the use of a series capacitor controlled by a thyristor to achieve reactive power balance in an IEEE-9 bus system. For these purposes, we use the simulation and analytical tool Mipower (version 6.1). The load flow problem has been solved using the Newton Raphson technique. At first, we checked out the IEEE-9 bus architecture with a series capacitor managed by a thyristor. The system study evaluates TCSC and traditional systems, contrasting their reactive power compensation, voltage profiles, and line losses. Results from the two scenarios show that TCSC boosts system performance.

Accepted version

Wi-Fi researchers are trying hard to extend battery life by optimizing 802.11 power save. The rising number of Wi-Fi devices and IoT devices and daily demands have reduced Station (STA) device power consumption. Better memory management at the Access Point (AP) side is also needed, so that AP can store maximum data to deliver sleepy STA devices. There are three main contributions of this study. The first one focuses on a power-saving mechanism scheme with an adaptive change to Listen Interval (LI) based on the battery status of station devices. The second contribution aims to examine better memory management for the AP buffer to store packets that will in the future deliver power-saving STA when awake. The third contribution, under the implementation of the proposed method, includes Wi-Fi corner cases covered as Beacon frames missed via STA, the keep-alive factor, and the upper-layer time taken to care for and ensure the delivery of unicast/multicast/broadcast data. The proposed approach introduced 802.11 protocols to share battery status, a protocol to announce proposed features via AP, and a protocol to change LI at runtime. Simulation results show that the proposed scheme performs better than 802.11 power saving in terms of power usage at the STA and access point memory management.

An Unified Power Quality Conditioner (UPQC), owning the composition of shunt and series Active Power Filter (APF), has become a standard accepted solution in the area of current and voltage harmonics mitigation of a power system network. This paper furnishes a novel approach of nonal switched UPQC topology, supported with Distributed Generation (DG), aiming at the power quality enhancement and position optimization, placed at different locations in a standard IEEE 14 bus system. In addition to this, behaviour of the proposed topology is analysed using novel Cascade Proportional Integral (PI) - Fuzzy and Space Vector Pulse Width Modulation (SVPWM) as control algorithms and the outcomes are compared with the historical twelve switch UPQC topology. Simulation results of the proposal modelled in MATLAB/SIMULINK reveals the superiority of nonal switched UPQC and the optimal position of the proposed conditioner, for mitigating the harmonic issues in the standard IEEE 14 bus system.

This article reports on the development and evaluation of a proposed optimal network reconfiguration approach for total real power losses reduction in radial distribution systems. The proposed approach was developed in MATLAB and the IEEE 33-bus radial distribution system was used in evaluating its performance. Application of the developed approach on the IEEE 33-bus radial distribution system helped to reduce the total real power losses of the system by 76.31%, from 202.68 kW to 48.02 kW, whereas the best approaches reported in literature reduced the losses by 31.15%, from 202.68 kW to 139.55 kW. These results suggest that the approaches reported in literature fail to find the global optimum combination of tie and sectionalizing branches whose corresponding switches have to be closed and opened, respectively, in order to minimize the total real power losses in the system. Consequently, due to its significant reduction of the system's total real power losses, the developed approach proves to be a potentially reliable tool for power system operators to adopt and use when solving the radial tribution systems' optimal network reconfiguration problem for real power losses reduction.

An orthogonal frequency division multiplexing (OFDM) transmitter for 802.11ah uplink may consume unnecessarily high power due to the malicious effect of a large peak-to-average power ratio (PAPR). This is particularly a problem for client devices (CDs) under the low-power wide-area (LPWA) technology in an Internet of thing (IoT) system, where high PAPR signals may drive the power amplifier (PA) to operate with large input back-off (IBO). This article focuses on receiver-side signal compensation (SC) techniques and introduces a novel scheme called iterative subcarrier regularization (ISR), which is based on the generalization of Papoulis-Gerchberg algorithm (GPGA). We claim that the proposed scheme is completely compatible with 802.11ah as it only exploits the prior information available in the standard operations and popular system-build-in functions in the iterative signal reconstruction process. Extensive numerical evaluations demonstrate that the proposed scheme can improve PA efficiency by 4-9 dB for uplink signaling.

Power-line communication (PLC) is a promising communication technology of constructing IoT (internet of things) systems, and it employs IEEE 1901 as its medium access control (MAC) protocol. Current studies about IEEE 1901 MAC performance analysis do not consider the influence of physical layer’s retransmission protocols, i.e., ARQ (automatic repeat request) and HARQ-CC (hybrid ARQ with chase combining). Moreover, how 1901 protocol affect the energy consumption in PLC networks, and whether 1901 protocol has bound performance are also unsolved in these existing works. Focusing on the above problems, we put forward a cross-layered theoretical model to insightfully analyze 1901 protocol, where the impacts of physical layer’s retransmission protocols (ARQ and HARQ-CC), channel fading modes and practical configurations (buffer size, finite traffic load, etc.) are comprehensively taken into consideration in the modeling process. On this basis, we derive the closed-form expressions of 1901 MAC metrics considering retransmission protocols. Furthermore, we construct an energy consumption model, and provide the bound performance analysis for 1901 protocol. Finally, we evaluate the performance of 1901 protocol under different retransmission protocols and system parameters, and verify the proposed cross-layered theoretical model.

For voltage stability assessment at a given operating point, various types of voltage stability indices (VSIs) have been proposed in the literature. In this paper, the voltage stability assessment of an IEEE-14 bus system is done for performance comparison of different types of VSIs available, under certain critical and practical stressed operating conditions (SOCs). The performance comparison of various VSIs under the considered SOCs is not reported in the literature. Such SOCs include the combinational occurrence of – variation in inductive loading, single line to ground (SLG) fault and effect of one generation unit tripped. These SOCs are the prime cause of voltage collapse of any node/line. The results show the performance of various VSIs with respect to line number, contingency ranking of the line, power margin, effects of loading and SLG fault. These VSIs are also instrumental in critical line and node analysis (CLNA) which is useful in the choice of proper location for reactive power compensation required. The simulated results provide the best performing VSI for accurate prediction of voltage instability under any considered SOC. This information is essential for voltage stability assessment of a particular line under multiple causes of voltage collapse.

The power consumption is rapid increased due to ASD (Adjustable Speed Drives) and automation in industries and large consumption of electricity in domestic regions increased the concern of the power quality. The quality of the power received in the Distribution system is altered because of the losses in the transmission system. The losses in the transmission system is mitigated using the FACTS (Flexible AC Transmission System)controller among these controllers UPFC (Unified Power Flow Controller) plays a vital role in controlling the shunt and series reactive powers in the bus of the power system. The conventional topology of the UPFC consists of AC-DC converter and energy stored in the DC link and DC-AC converter injected a voltage in series to the bus which as to be controlled. Whereas a new topology based on matrix converter can replace the dual converters and perform the required task. The construction of 2-bus, 7-bus and IEEE-14-bus power system is designed and modeled. MC-UPFC (Matrix Converter Based Unified Power Flow Controller) is designed and constructed. The MC-UPFC is the rich topology in the FACTS which is capable of controlling both the transmission parameters simultaneously with the switching technique of Direct power control by the smooth sliding control which gives less ripple in the injecting control parameters such as control voltage [Vc] and voltage angle [α]. By implementing MC-UPFC the real and reactive power can be controlled simultaneously and independently. The control techniques were designed based on the Proportional Integral derivative(PID) with sliding surface power control, FLC (Fuzzy Logic Controller) and ANN (Artificial Neural Network) and the performance of Vc and α of the controllers are investigated. Hence the sliding surface and relevant control switching state of the MC can be controlled by the FLC which gives the robust and autonomous decision making in the selection of the appropriate switching state for the effective real power control in the power system. The work has been carried out in the MATLAB Simulink simulator which gives the finest controlling features and simple design procedures and monitoring of the output.

An M/M/1 queueing system subjected to multiple differentiated vacations, customer impatience and a waiting server is analyzed. The explicit transient probabilities of system size are derived using probability generating function technique, Laplace transform, continued fractions and some properties of confluent hypergeometric function. Further, the time-dependent mean and variance are obtained as the performance measures. A numerical example is presented in order to study the behavior of the system.

Active power flow through a transmission line is one of the main index for reliable operation of power system. During abnormal condition this power can be observed using stability analysis. In this paper, IEEE 14 bus system has been selected for this time domain simulation. A three phase fault has been considered as an abnormal condition for the power system. In addition, this work also observed the rotor angle of the synchronous generators of the system. Results of these observations would be helpful for an operator to take necessary steps for normal operation of a power system as well as planning to improve the system.

In the era of expansion of smart sensing interconnected devices and their growing application in complex systems, the application of wireless communication technology becomes evident. Many wireless technologies are developed to facilitate the growth of systems such as the Internet of Things and Smart Cities. The application of a particular wireless technology in a particular system depends on many factors, such as purpose, requirements, complexity, range, and node deployment. IEEE 802.15.4 is a technical standard that defines the operation of low-rate wireless personal area networks. It is used as the basis for a group of network standards and protocols designed for wireless sensor networks. In this article, the basic features of the emerging IEEE 802.15.4g SUN low-powered wireless network standard, its application scenarios, and performance analyses are presented.

The introduction of the cyber-physical system (CPS) into power systems has created a variety of communication requirements and functions that existing legacy systems do not support. To this end, the IEEE 1815.1 standard defines the mapping between existing distributed network protocol networks and IEC 61850 networks that reflect new requirements. However, advanced CPS cyberattacks have been reported, and in order to address cyberattacks, security research on new power systems that use network devices and heterogeneous communication is necessary. In this study, we propose an intrusion detection system for an IEEE 1815.1-based power system using CPS. We 1) analyze an IEEE 1815.1-based power system network and propose a suitable application method for an intrusion detection system, 2) suggest a bidirectional recurrent neural network-based anomaly detection system for an IEEE 1815.1-based network, and 3) demonstrate the verification of the proposed technique using various power system-specific attack data, including real power system using CPS network traffic, CPS malware behavior (CMB), false data injection (FDI), and disabling reassembly (DR) attacks. Proposed technique successfully detected five types of CMB attacks, three types of FDI and DR attacks.

The increasing usage of LLC-type dc-dc converters in utility, automotive, and power distribution applications has led to a push for a further increase in the converter's operating load range and efficiency. The secondary-side rectifier remains one of the lossiest areas in the converter, alluring designers to synchronous rectification (SR). One method is drain-source SR for cyclically adaptive, closed loop SR. However, when utilized, a severe current oscillation can be observed. An increase in SR duty cycle results in an increase in conduction time of the SR channel over the body diode. This issue becomes increasingly prevalent due to the usage of wide band-gap MOSFETs with high reverse drops and low sensed signal strength. This results in a current oscillation effect, leading to inconsistent SR operation, output ripple, and high EMI. In this paper, the issue is root caused analyzed. A method of improving drain-source SR for light-load SR operation is proposed. The method is prototyped on an FPGA to alleviate the issue on a $600\text{-}V_{in}/ 340\text{-}V_{out}$ 2.5-kW LLC-DCX (DC transformer) power converter.

In real-life power system, optimization methods are used on a daily basis to obtain optimal dispatch for various types of power plants. In this paper, the existing optimization method is used to maximize profit of three cascaded Hydro Power Plants (HPP) and to co-ordinate HPPs dispatch according to Wind Power Plants (WPP) production forecast. A two-stage optimization method was used with first stage design to obtain optimal HPPs dispatch plan and to maximize profit by selling electricity on a day-ahead market. First optimization stage is defined as mixed- integer liner programming (MILP) problem. Obtained dispatch plan together with the WPPs production forecast is used to check power flows in the transmission network and if line congestion occurs, second optimization stage is needed, and it is defined as quadratic programming (QP) problem. The objective of second optimization stage is to find re-dispatch plan that would be minimal deviation from an initial dispatch but it would eliminate line congestions. Proposed optimization strategy is tested using IEEE 14 Bus Test System and the results are presented in this paper.

Nowadays, electrical energy needs are increasing rapidly as a result of technological developments. In order to meet this growing demand, power plants have been built. In this study, voltage stability in IEEE 14-bus power system was investigated by means of Extreme Learning Machine (ELM). For this purpose, the IEEE 14-bus power system model was built in Matlab environment and load flow analysis for this model was performed by using the Newton-Raphson Method (NRM). In this power system, the voltage stability was evaluated by calculating the Line Stability Index (LSI). In the load flow analysis, the active and reactive powers of all bus were increased by 0.05 step (pu) and a total of 1000 active power, reactive power, voltage, and phase angle of the respective bus were obtained for each busbar. These values were used to calculate the values of LSI. The inputs of ELM are selected as active power, reactive power, voltage and phase angle of the respective bus. The output of the NRM was determined as LSI values. The test performance of the NRM is given by 5-fold cross-validation. In addition, the ELM’s performance was investigated for the different number of hidden layer cell numbers and different types of activation functions. The proposed method provides the best test performance in case of ELM with a hidden layer cell number of 100 and the tangent sigmoid activation function. From the obtained results, it is seen that ELM predicted LSI with a very high performance in determination of voltage stability in IEEE 14-bus power systems.