Power Transmission Scheme Research Articles

Model for building traction information of suburban rolling stock on hydrogen fuel

The materials consider the possibility of using hydrogen as a fuel for suburban rolling stock in Ukraine. The analysis of the use of hydrogen fuel in transport in various countries of the world is carried out. One of the main stages of calculating the rolling stock is the construction of its traction characteristic, which largely depends on the type of power plant. Therefore, a model has been developed for constructing traction characteristics of a suburban rolling stock when it is converted to hydrogen fuel. For this purpose, an analysis of power equipment with an energy source from a polymer of an exchange membrane fuel cell and methods of connecting their batteries to blocks is done. The scheme of power transmission for the rolling stock is proposed and its efficiency coefficient is preliminarily calculated. The main technical indicators of suburban rolling stock in Ukraine at the moment and using proton-exchange membrane fuel cells on it are considered. Preliminary consideration is given to the operation parameters of the electric circuit of the rolling stock under various modes of its motion. The traction characteristic of a suburban mobile suction on hydrogen fuel is constructed. The proposed model is implemented in the software product MathLab.

Joint Offloading and Transmission Power Control for Mobile Edge Computing

With the exploding growth of smart devices and application of 5G communications, there are more and more computation-intensive tasks which are delay-sensitive. Mobile edge computing (MEC) is a new paradigm that provides rich computing resources in close proximity to mobile users. However, how to make the decision of whether offloading or not as well as control the transmission power jointly remains a challenge. In this paper, we first study the joint multiuser offloading and transmission power control optimization problem in a multi-channel wireless interference scenario. We formulate the joint optimization problem into a system-wide computation overhead minimization problem as a mixed integer non-linear program. We then propose an efficient semi-distributed algorithm consisting of two subalgorithms of offloading scheme and transmission power control. The numerical simulation results demonstrate that the proposed algorithm can effectively reduce system-wide computation overhead and increase the number of beneficial edge computing users, compared with all local or edge computing and fixed transmission power schemes.

On Full-Bridge Bipolar MMC-HVDC Control and Protection for Transient Fault and Interaction Studies

Bipolar high voltage direct current (HVdc) links present one reasonable solution to realize bulk power transmission schemes. Especially if full-bridge modular multilevel converter topologies (FB MMC) are utilized, a broad variety of operational advantages exists. To completely unveil intrinsic technological potentials, comprehensive control and protection concepts to discriminate and handle ac, dc, as well as internal converter faults are essential. The proposed scheme consists of a fast and selective multizonal fault detection paired with decoupled ac and dc current controls. As a result, actively controlled dc fault current interruption as well as ac fault reactive current injection are incorporated. It is demonstrated that internal converter quantities remain within feasible technical boundaries, interactions are limited or even fully mitigated, and protection thresholds can be chosen to enable selective tripping. To validate and evaluate the proposed concept, simulations for characteristic faults are performed in electromagnetic transients software.

Wireless Power and Bidirectional Data Transfer Scheme for Battery Charger

Wireless battery charging has been becoming a recent trend in mobile devices. However, there are relatively less research efforts focusing on the large power applications. It is a major drawback of the battery charging in traditional electric vehicles which relies on the use of a plug-in charging device. This paper proposes a wireless power and bidirectional data transmission scheme, data related to battery status, vehicle identification number, or emergency messages that can be mutually transmitted between two isolated units via the same LC tank. The primary unit employs an inverter to yield alternating current and power flow to the load via mutual inductance. The secondary unit transfers data by adjusting current of load, and the primary unit receives data based on the zero-voltage switching method. The primary unit transfers command by trimming the current's curve and the secondary unit receives command and make decoding using the period of carrier wave. It is worth to mention that the design scheme enables it to handle the situation of emergency by sending back the message to the primary unit to make an emergency halt.

Resilient strategy design for cyber-physical system under DoS attack over a multi-channel framework

This paper is concerned with the design of resilient strategy for a class of cyber-physical system (CPS) under denial-of-service (DoS) attack. The DoS attack occurring in wireless network between sensor and remote estimation is considered. For the addressed CPS, a minimax control strategy is designed in the presence of DoS attack in delta domain under imperfect state measurements (IPSM). Then, a novel multi-channel transmission framework is constructed to reduce the probability of being attacked, where transmitter chooses a single channel to send data packet and meanwhile the DoS attacker decides a target channel to attack. Taking account of the control system performance, a two-player Markov stochastic game is built to model the interactive decision-making of both sides under energy budget constraints. Dynamic programming and value iteration methods are applied for the control strategy and power transmission strategy design, respectively. Numerical simulations are presented to illustrate the validity of the scheme.

Analysis of Relay-Assisted OFDMA Cellular Systems with Different Frequency Reuse Techniques

Co-channel interference (CCI) degrades performance of cellular networks. Therefore, this paper addresses CCI problem in relay-assisted (R-A) orthogonal frequency division multiple access cellular systems. Analytical treatments are conducted. The network performance improvements through reducing CCI effects are evaluated using different four interference mitigation models. These models represent R-A strict fractional frequency reuse (FFR) technique with frequency reuse factor (FRF) \(=\) 3, R-A strict FFR technique with FRF \(=\) 4, R-A sectored FFR technique and R-A soft frequency reuse (SFR) technique. Each model contains two different configurations for further network performance improvement. The first configuration assumes three relay stations (RSs) per cell (RPC) while the other one proposes 6 RPC. The best RSs locations in terms of SIR are proposed. Moreover, closed-form expressions for worst cases CEU’s SIR, cell centre user’s SIR and inner radius are implemented. These expressions are used to compare different models using various performance evaluation metrics. The results demonstrate that the two configurations in R-A sectored FFR and R-A strict FFR models provide equal CEU’s SIR. The reason of this result can be attributed to applying equal power transmission strategy. Moreover, the two configurations of R-A SFR network attain different CEU’s SIR values. This result can be accredited to the SFR power control factor. The work outcomes attain much higher CEU’s SIR improvement. Therefore, the outage probability is decreased. Thus, more users can be covered by the network. Accordingly, the total network cost is reduced. So, this treatment improves the network performance while keeping lower network cost.

Voltage Distribution–Based Fault Location for Half-Wavelength Transmission Line with Large-Scale Wind Power Integration in China

Large-scale wind farms are generally far away from load centers, hence there is an urgent need for a large-capacity power transmission scheme for extremely long distances, such as half-wavelength transmission lines (HWTLs), which can usually span thousands of kilometers from large-scale wind farms to load centers. An accurate fault location method for HWTLs is needed to ensure safe and reliable operation. This paper presents the design of a modal voltage distribution–based asynchronous double-end fault location (MVD-ADFL) scheme, in which the phase voltages and currents are transformed to modal components through a Karenbauer transformation matrix. Then, the modal voltage distributions along transmission lines are calculated by voltage and current from double ends. Moreover, the minimums and intersection points of calculated modal voltages from double ends are defined as the fault location estimation. In order to identify incorrect fault location results and reduce calculation errors for the correct ones, air modal and earth modal voltage distributions are applied in the fault location estimations. Simulation results verify the effectiveness of the proposed approach under different fault resistances, distances, and types. Lastly, a real-time digital simulator (RTDS)–based hardware-in-the-loop (HIL) test is undertaken to validate the feasibility of implementing the proposed approach.

Smarttag: An Indoor Positioning System Based on Smart Transmit Power Scheme Using Active Tags

There are no large-scale deployments to navigate the people indoor environments as the GPS for outdoor environments. For this reason, the development of high-performance systems of indoor localization has been considered the potential research areas by both academia and industry in last decade. These indoor localization research studies are divided into two groups in the literature which are reader-based and tag-based systems. Most of these studies are reader-based. These readers and tags can determine the received signal strength levels of the signal using the radio frequency technology. We present a tag-based and cost-effective indoor localization system using NRF24L series radio modules. Different from the available tag-based systems, we propose a smart transmit power scheme run in the tags called SmartTag. The SmartTag provides communication with the nearest reader using different power levels. However, the existing tag-based methods require the received signal strength indicator (RSSI) information to achieve high localization accuracy. Our proposed system eliminates RSSI information with the SmartTag. We have developed a simulation of the prototype system, and we used Monte Carlo simulations in many different scenarios. We have also implemented the system prototype and conducted in an actual indoor environment to demonstrate the performance of the SmartTag by comparing with the Monte Carlo simulations. From the indoor experimental results, we confirm that the detections of room and objects are accurate and positioning accuracy is improved thanks to the SmartTag localization. If we briefly summarize our work, we have determined the position in indoor environments by communicating with the nearest reader in the medium thanks to the scheme on the SmartTag.

Joint optimization of cascades in Yalong River and the middle and downstream of Jinsha River

The main tributaries of the upper reaches of the Yangtze River are not only the strategic base for China’s water resources, but also an important hydropower base for the “West-East Power Transmission Strategy”. With the completion of these reservoir groups, a large-scale mixed reservoir system across the different basins has been formed, which makes the requirements for joint optimization and scheduling of large-scale hydropower system getting higher and higher. This paper focuses on the key problems faced by the joint optimization of large-scale hydropower system in the basin. Taking the Yalong River and the middle and downstream of the Jinsha River as the research area, the hybrid optimization method is introduced herein to solve the joint optimal scheduling model. The results reveal that the power generation by joint optimal scheduling is much more than separately scheduling, and the total power generation increased by 2.84% on average. As Mid-Jinsha cascade and Yalong River cascade has a 690 million kW·h and 190 million kW·h decrease in power generation respectively, the downstream Jinsha River cascade has a power generation increase of 4.31 billion kW·h.

Rate and Power Optimization Under Received-Power Constraints for Opportunistic Spectrum-Sharing Communication

In this paper, the channel capacity of secondary user is investigated for opportunistic spectrum sharing with primary user in a Rayleigh fading environment. In the proposed communication scenario, on finding transmission opportunities in licensed band, secondary user utilizes the band as long as the interference power inflicted on primary receiver is below the predefined threshold, and adjusts its transmission power and data rate based on the sensing information available from spectrum sensor. In this context, two different adaptation schemes namely adaptive transmission power scheme and adaptive rate and transmission power scheme are investigated under joint peak and average received power constraints at primary receiver for multilevel quadrature amplitude modulation format. The closed form expressions are derived for the ergodic channel capacities of these schemes and numerical results are presented to validate the theoretical results. Moreover, a comparison between channel capacities is given to illustrate the benefit of using soft sensing information under said constraints.

Asymptotic Analysis of Rayleigh Product Channels: A Free Probability Approach

The Rayleigh product channel model is useful in capturing the performance degradation due to rank deficiency of MIMO channels. In this paper, such a performance degradation is investigated via the distribution of mutual information assuming the block fading channels and the uniform power transmission scheme. Using techniques of free probability theory, the asymptotic variance of mutual information is derived when the dimensions of the channel matrices approach infinity. In this asymptotic regime, the mutual information is rigorously proven to be Gaussian distributed. Using the obtained results, a fundamental tradeoff between multiplexing gain and diversity gain of Rayleigh product channels under the uniform power transmission can be characterized by the closed-form expression at any finite signal-to-noise ratio. Numerical results are provided to compare the outage performance between the Rayleigh product channels and the conventional Rayleigh MIMO channels.

Concurrent transmission mechanism to mitigate pan-exposed-node problems in wireless sensor networks

Power control technology is widely used in wireless sensor networks to improve network performance. The asymmetric transmission power strategy used in power control technology causes the re-emergence of hidden-node problems and more serious exposed-node problems. This article analyzes the reasons of these problems and proposes the concept of the pan-hidden node and pan-exposed node. To avoid pan-hidden-node problems and mitigate pan-exposed-node problems, a concurrent transmission mechanism is presented. The concurrent transmission mechanism contains a strict time schedule for different categories of frames and an interference degree criterion to ensure concurrent transmission. The rigorous time schedule can guarantee that different classes of frames do not interfere with one another. The interference among the frames of the same type is constrained by the interference degree criterion. Finally, the performance of the concurrent transmission mechanism is evaluated using simulation experiments.

Improve QoS of IEEE 802.11p Using Average Connected Coverage and Adaptive Transmission Power Scheme for VANET Applications

It is very challenging task to achieve good Quality of Services (QoS) in highly dynamic topology of Vehicular Ad hoc NETwork (VANET). The Average Connected Coverage (ACC) is very important QoS of V...

High-Frequency, Half-Wavelength Power Transmission Scheme

The half-wavelength power transmission scheme has some unique advantages and disadvantages for power transmission. This paper presents a new concept to take advantage of the scheme while overcoming its main limitation. The concept involves a power generation transmission unit. This unit generates and transmits power at a specific high frequency so that the distance between the generator and the receiving end is equal to a half-wavelength of the voltage/current of the system. As a result, a far-away generator becomes electrically located at the receiving end as if there is no transmission line separating the sending and receiving ends. The proposed concept represents an innovative and promising scheme to transmit a large amount of power over long distances.

Throughput assurance of wireless body area networks coexistence based on stochastic geometry.

Wireless body area networks (WBANs) are expected to influence the traditional medical model by assisting caretakers with health telemonitoring. Within WBANs, the transmit power of the nodes should be as small as possible owing to their limited energy capacity but should be sufficiently large to guarantee the quality of the signal at the receiving nodes. When multiple WBANs coexist in a small area, the communication reliability and overall throughput can be seriously affected due to resource competition and interference. We show that the total network throughput largely depends on the WBANs distribution density (λp), transmit power of their nodes (Pt), and their carrier-sensing threshold (γ). Using stochastic geometry, a joint carrier-sensing threshold and power control strategy is proposed to meet the demand of coexisting WBANs based on the IEEE 802.15.4 standard. Given different network distributions and carrier-sensing thresholds, the proposed strategy derives a minimum transmit power according to varying surrounding environment. We obtain expressions for transmission success probability and throughput adopting this strategy. Using numerical examples, we show that joint carrier-sensing thresholds and transmit power strategy can effectively improve the overall system throughput and reduce interference. Additionally, this paper studies the effects of a guard zone on the throughput using a Matern hard-core point process (HCPP) type II model. Theoretical analysis and simulation results show that the HCPP model can increase the success probability and throughput of networks.

Modular multilevel converter losses model for HVdc applications

Multi-terminal high voltage dc (HVdc) grids can eventually became a feasible solution to transport energy to remote and/ or distant areas and its exploitation depend, among other things, on the performance of the converter terminals. Therefore, to optimize the power transmission strategy along such a grid, it is necessary to recognize the efficiency of all the converters in all points of operation, namely with the different load conditions. In this vision, the aim of this work is to provide the methodology to model the modular multilevel converter (MMC) efficiency by means of a mathematical expression that can describe, over a broad range of active and reactive power flow combinations, the power losses generated by the semiconductors. According to the presented methodology, a polynomial-based model with a reduced number of coefficients is deducted, in such a way that can be directly used for optimal power flow (OPF) studies. The accuracy of the proposed model is characterized by an absolute relative error, at the worst scenario, approximately equal to 3%.

Performance Analysis of Combined Space Time Block Coding with Generalized Selection Combining in Underlay Cognitive Radio

In this paper, we demonstrate the performance analysis of an underlay MIMO cognitive radios employing space time block coding at secondary’s user transmitter (SU-Tx) and generalized selection combining at secondary’s user receiver. The transmit power strategy enforces the SU-Tx to adapt its power to be transmitted so as to protect primary user’s receiver from harmful interference in order to satisfy primary user outage constraint. We derive closed form expressions for average post processing signal to noise ratio and ergodic capacity. Moreover, approximate expression for average bit error rate is also obtained. Based on the achieved results, we show that the average post processing SNR, Ergodic Capacity and average BER improve as number of best branches to be combined increases. Finally analytical results are affirmed through Monte Carlo simulations.

A Reconfigurable Scheme of Wireless Power Transmission in Fully Enclosed Environments

This letter proposes a reconfigurable scheme of wireless power transmission in fully enclosed environments. The proposed scheme includes one transmitting element and multiple parasitic elements. Field distribution in the fully enclosed environment is reconfigured by switching the parasitic elements’ termination between open and short, with the aim of delivering wireless power efficiently to a receiver whose location is not fixed or not known. Experimental results demonstrate that, via tuning nine parasitic elements at frequency 425 MHz, it is possible to achieve power transmission efficiency greater than 70% when a wireless power receiver changes its location within a 0.4 m by 0.6 m region inside a 1-cubic-meter cubic box.

Increasing the Lifetime of Mobile WSNs via Dynamic Optimization of Sensor Node Communication Activity.

In this paper, a simple and flexible method for increasing the lifetime of fixed or mobile wireless sensor networks is proposed. Based on past residual energy information reported by the sensor nodes, the sink node or another central node dynamically optimizes the communication activity levels of the sensor nodes to save energy without sacrificing the data throughput. The activity levels are defined to represent portions of time or time-frequency slots in a frame, during which the sensor nodes are scheduled to communicate with the sink node to report sensory measurements. Besides node mobility, it is considered that sensors’ batteries may be recharged via a wireless power transmission or equivalent energy harvesting scheme, bringing to the optimization problem an even more dynamic character. We report large increased lifetimes over the non-optimized network and comparable or even larger lifetime improvements with respect to an idealized greedy algorithm that uses both the real-time channel state and the residual energy information.

Power allocation for sensing-based spectrum sharing cognitive radio system with primary quantized side information

Spectrum access approach and power allocation scheme are important techniques in cognitive radio (CR) system, which not only affect communication performance of CR user (secondary user, SU) but also play decisive role for protection of primary user (PU). In this study, we propose a power allocation scheme for SU based on the status sensing of PU in a single-input single-output (SISO) CR network. Instead of the conventional binary primary transmit power strategy, namely the sensed PU has only present or absent status, we consider a more practical scenario when PU transmits with multiple levels of power and quantized side information known by SU in advance as a primary quantized codebook. The secondary power allocation scheme to maximize the average throughput under the rate loss constraint (RLC) of PU is parameterized by the sensing results for PU, the primary quantized codebook and the channel state information (CSI) of SU. Furthermore, Differential Evolution (DE) algorithm is used to solve this non-convex power allocation problem. Simulation results show the performance and effectiveness of our proposed scheme under more practical communication conditions.