Power Transmission Mode Research Articles

Key Technical Research on Power Electronics and Information Transmission System

Power electronics is a new technology of power transmission and control. Compared with the traditional power transmission, non-contact power transmission has the advantages of low wear rate, safety, reliability, convenience and flexibility. In this way, it avoids the problems of friction, wear, aging and so on in the traditional power supply mode, saves a lot of wires, makes up for the shortcomings of the traditional power transmission mode, and has a wider application range. Therefore, it is of great practical significance to study the key technology of power electronic information transmission for promoting the intelligent development of power transmission in China.

Uncertain Hybrid Multiple Attribute Group Decision of Offshore Wind Power Transmission Mode Based on theVIKOR Method

With the increasing scale of offshore wind power, large-capacity and long-distance offshore wind power will be a trend in the future development of wind power. However, compared with onshore wind power transmission, offshore wind power transmission is more difficult and costly. Therefore, it is of great practical significance and urgency to select the appropriate power transmission mode to realize the long-distance transmission of large-capacity offshore wind power. Since the selection of offshore wind power transmission mode is a multiple attribute decision making problem, in this paper, the technical characteristics of high voltage alternating current (HVAC) and voltage source converter based on high voltage direct current (VSC-HVDC) that are already in use and hybrid HVDC that is possible to be used in offshore wind power transmission in the future are discussed. Based on this analysis, the reliability, economy and construction difficulty of offshore wind power transmission mode are systematically analyzed, and VIKOR method is applied to group decision-making for the selection of offshore wind power transmission mode. The main contributions of this paper are as follows: (1) the characteristics of large-capacity and long-distance offshore wind power transmission are studied, and the evaluation system with multiple indexes including a large number of qualitative indexes is constructed from the technical, economic and social aspects. In order to deal with difficult problems of fuzzy information, interval numbers, language variables, intuitionistic fuzzy numbers and other data types are used to deal with them effectively. (2) In the VIKOR method, because the expert weights are unknown in group decision-making, the expert trust function is used to objectively determine the weight of each expert. (3) The group decision-making analysis of actual case of offshore wind power plant is carried out by using expert knowledge and VIKOR method. The case shows that this method is simple, reasonable and practical.

Wireless Power and Data Transmission System of Submarine Cable-Inspecting Robot Fish and Its Time-Sharing Multiplexing Method

In this paper, a hybrid system topology with one-way wireless charging function and the function of the bi-directional data communication is proposed for the problem of electric energy replenishment and data transmission faced by robot fish in the implementation of autonomous submarine cable inspection. Three working modes of the system and the time-sharing multiplexing method are studied. In the power transmission mode, high-efficiency wireless charging is realized by utilizing the transmission characteristics of a series–series (SS)-type resonant network which involves series resonant networks in both the primary side and the secondary side. In the alignment detection and handshake communication mode, the charging platform distance recognition and the handshake signal transmission are implemented through a series–parallel (SP)-type resonant network based on the ASK (amplitude shift keying) modulation method. In the high-speed data transmission mode, the reverse (secondary to primary) high-speed transmission of the inspection data is achieved through a SP-type resonant network based on the OFDM (orthogonal frequency division multiplexing) modulation method. The three modes share the same coupled coils via a reconfigurable resonant network. The working principle of the system is expounded, the system characteristics under each working mode are analyzed, and the time-division multiplexing control strategy is given. The rationality and effectiveness of the scheme are verified by experiments.

Placement of shunt reactors in high-voltage network using fuzzy constraints

In recent years, controlled shunt reactors (CSR) relevant to the class of FACTS facilities have been widely used to control voltage modes and reactive power flows in the high-voltage electrical network. The selection of location, as well as the definition of the law of CSR control in the conditions of stochastic variability of the operation mode of high-voltage power transmission, are associated with numerous technical and economic factors. At the same time, such constraint conditions as ease of use, performance efficiency, purpose and location in the system, as well as the period of commissioning should be taken into account. In the proposed procedure these factors are considered as fuzzy constraints. The procedure of CSR placement in the 330 kV electrical network of Azerenergy system for control of reactive power flows taking into account the mentioned fuzzy constraints is proposed. The obtained simulation results confirm the advantage of the proposed procedure.

Optimization Model for the Short-Term Operation of Hydropower Plants Transmitting Power to Multiple Power Grids via HVDC Transmission Lines

Long-distance and large-capacity hydropower transmission from large hydropower plants in southwestern China to load centers is an important and effective measure for the accommodation of large-scale hydropower in China. However, the load demands of the receiving-end power grids are not fully considered in the conventional power transmission mode, which has greatly affected their enthusiasm for the absorption of trans-regional hydro energy. In order to make full use of the peak shaving capability of the hydropower plants, this paper develops an optimization model for determining the hourly generation scheduling of the hydropower plants transmitting electric power to several power grids via high voltage direct current (HVDC) transmission lines. A large-capacity and highly complex multi-unit hydropower system, the Xiluodu plant in China, is taken as the case study. In the proposed model, minimizing the peak-valley differences of multiple receiving-end power grids is adopted as the objective to alleviate the peak shaving pressure of the receiving-end power grids. In addition to the traditional hydraulic constraints, the operation constraints of individual units and HVDC power transmission limits are well considered. The study focuses mainly on modeling the stair-like power transmission curve constraint which is discrete and nonlinear and has been rarely considered in previous studies. This constraint is then linearized through limiting the logical relations between multiple binary integer variables. Case studies demonstrate that the proposed model has high computational efficiency, and the peak-valley differences of the two receiving-end power grids, i.e., Zhejiang Power Grid and Guangdong Power Grid, are decreased by 15.2% and 7.33%, respectively. Moreover, frequent conversion of HVDC converter equipment can also be avoided, which makes the obtained generation schedule more executable.

Study on Manufacturing Process and Current Carrying Characteristics of Layering Enamelled Stranded Conductor

Ultra high voltage(UHV) power cable system is an economical, safe and reliable power transmission mode. In recent years, the concern about the traditional fossil energy pollution in the world and the determination to using clean energy have promote the medium distance UHV submarine power cable system. This paper designs and tests one kind of energy saving and loss reducing conductor applied to large cross-section submarine cable. Through reasonable process control, the paint film on the enamelled wire surface can be avoided being scraped during the process of twisting. According to the measured AC / DC resistance ratio, the optimized design for the subsequent conductor is put forward. Compared with the traditional conductor, the current carrying capacity of the conductor is improved, and it has a positive and practical significance for reducing the Joule loss of the cable system.

Near Field Radio Frequency Radiation Hazard on Military Armoured Vehicle - Approach to a Dose Assessment

The level of radio frequency (RF) electromagnetic field emitted from a military armoured vehicle antenna was investigated to identify possible adverse health effect on personnel, especially in the near field region. Both E-Field and H-Field radiations levels emitted from antenna were recorded by emphasising on the main areas of crew working station. To date, open literature on military vehicle and equipment RF radiation hazard safety assessment has limited numbers of discussion especially on RF source distance, location and mode of power transmission. In this investigation, RF levels from two radio antennas were measured, high frequency (HF) and very high frequency (VHF) with the low and high-power transmission. Measurements were taken in two distinct locations namely; commander and gunner respectively with three different conditions; open hatch, close hatch and open hatch with standing crews which representing the normal and combat situations. The measured E-Field and H-Field levels were then assessed for compliance with occupational reference levels of Military Standard 464C, The Institute of Electrical and Electronics Engineers (IEEE) for Military Workplace standards and International Commission on Non-Ionising Radiation Protection (ICNIRP) guidelines. The occupational standard was exceeded on commander and gunner area at certain condition; nevertheless, the rest of the conditions complied within the occupational standard.

Selection of desirable transmission power mode for the bundled wind-thermal generation systems

Although the integration of large–scale clean wind power will have a positive impact on the environment deterioration and reduce the fossil fuel depletion, it also creates challenges for power system operations. Considering that some countries, such as China, hold a geographical advantage of adjacent distributions of wind and coal resources, i.e., the windy areas are located/close to the areas with vast coal reserves, one feasible plan of both utilizing the large–scale wind power and alleviating the operation burden of power systems is to build bundled wind–thermal generation systems (BWTGSs). This paper first gives the optimal BWTGSs (investment) planning method, in which the cost changing rules, the candidate scheme formation, and long–term wind–thermal coordinated generation scheduling simulation are introduced. Then based on different compensation purposes or requirements, four transmission power modes, i.e., constant transmission power mode, thermal–generation–smoothed transmission power mode, transmission power mode considering load pattern of receiving system, and sectioned transmission power mode, are proposed. Finally, numerical studies are conducted. Planning results show that the generator schemes, total costs, and clean energy proportions differ when adopting different transmission modes, and the sectioned transmission power mode is the most desirable mode with the lowest total planning cost and the highest clean energy proportion.

Fog Computing: Data Streaming Services for Mobile End-Users

Cloud computing with its services models (SaaS, PaaS, and IaaS) and its characteristics such as (on demand services, rapid elastics, and scalability) still has a number of problems that prevent some applications from the advantages of this computing paradigm. The long distance between the end-users and the cloud server might be the biggest issue for some real time applications, such as online gaming and content delivery, in term of latency. Fog computing is an emerging paradigm used to solve some issues in cloud computing. It empowers deploying the resources and the services at the edge of the network that is close to end users. The use of streaming services for sensor networking applications is a very important model in machine-to- machine paradigm of communication. In this paper we propose a system for content delivery services for mobile users using fog computing. The fog nodes are distributed at the edge of the network, in the middle between the cloud and mobile users. These nodes receive requests from the users and respond to each request either immediately, in case the service is already downloaded in the fog server, or by bringing the servers either from the cloud server or other fog nodes. The fog nodes are represented as server using COAP protocol. As expected, the results show fog computing provides low response time against the cloud computing. The results also, investigate the power consumption of mobile users for the four dierent modes, Low power mode, Transmission mode (Tx), Receiving mode (Rx), and CPU when they connect directly to fog servers.

Novel Modeling of a Fast DC Breaker for a VSC-HVDC Transmission System Protection

The inability to quickly isolate the faulty sections of the direct current (DC) network damages the converters and the transmission system. Further delay in fault interruption can be escalated to the generation system thus shutting down the whole power system. Currently, Voltage Source Converter-High Voltage Direct Current (VSC-HVDC) systems provide the best mode of bulky power transmission over long distance. Though VSC-HVDC have their own internal protection, they still suffer from short-circuit faults especially on the DC side hence requiring a novel fast DC breaker. The novel design of the DC breaker in this paper utilizes a systematically calculated mutual inductance to divert the energy generated during fault to resistive elementson both sides of the DC breaker thus, preventing the transient voltage and backward current generated at the time of clearing the fault. The major challenge for DC breaker is that current is not alternating inferring that it has no natural zero current occurring point. Thus, the current has to be artificially forced to cross a current zero point so that the fault can be easily interrupted.This study aims at reviewing the currently available DC breakers with a fault clearing time of 5msby modelinga novel fast DC breaker therefore, providing the best possible protection against short-circuit faults on VSC systems. The results indicate that the proposed DC breaker model has a fault clearing time of 1ms. This is a major contribution towards the development a fast DC breaker.

Increasing throughput in energy-based opportunistic spectrum access energy harvesting cognitive radio networks

The performance of large-scale cognitive radio (CR) networks with secondary users sustained by opportunistically harvesting radio-frequency (RF) energy from nearby primary transmissions is investigated. Using an advanced RF energy harvester, a secondary user is assumed to be able to collect ambient primary RF energy as long as it lies inside the harvesting zone of an active primary transmitter (PT). A variable power (VP) transmission mode is proposed, and an energy-based opportunistic spectrum access (OSA) strategy is considered, under which a secondary transmitter (ST) is allowed to transmit only if its harvested energy is larger than a predefined transmission threshold and it is outside the guard zones of all active PTs. The transmission probability of the STs is derived. The outage probabilities and the throughputs of the primary and the secondary networks, respectively, are characterized. Compared with prior work, the throughput can be increased by as much as 29%. The energy-based OSA strategy can be generally applied to a non-CR setup, where distributed power beacons (PBs) are deployed to power coexisting wireless signal transmitters (WSTs) in a wireless powered sensor network.

Коммутационные управляемые устройства на p—i—n-диодах миллиметрового диапазона длин волн

The paper presents the results of research and development of concentrated type p—i—n-diodes switches providing the switching time at the level of a few nanoseconds. To increase lock losses of (~40 dB) the authors use a cascade connection of diodes into waveguide and microstrip transmission line of q = p/2 electric length. Investigation results of creation of switching devices using longitudinally and transversely-distributed p—i—n-structures in the shortwave part of the millimeter wavelength range (f = 300 GHz) are presented. When developing switching devices intended to control the level of microwave power in the millimeter wavelength range, a number of special features arise limiting the achievement of optimal parameters. The dimensions of the metal ceramic packaged p—i—n-diodes and the mounting elements of semiconductor structures become comparable with the wavelength. As a result, package cannot be considered in the calculations and in the design as the capacity of the concentrated type. In our case the diode package is considered in the form of radial line which is able to transform the input impedance of the transmission line to the terminals of the diode structures, and realize high-impedance state (parallel resonance) in the device circuit in the mode of microwave power transmission. Engineering calculations for the given parameters of the silicon mesostructures showed the possibility of creating high-speed devices for switching microwave power with good characteristics. For diode assembling industrial clockwork ruby jewels with high quality of surface finish, strength and appropriate dimensions are applied as dielectric bushings. Suffice it to say that in the frequency range of 150 GHz, we used the bushings with dimensions of external diameter D = 0.4 mm and a height of h = 0.15 mm. The switches created provide transient units of nanoseconds, isolation more than 40 dB at relative frequency bandwidth of 30-40%. Evaluating progress in the development of millimeter wavelength devices, it should be noted that at frequencies greater than 200 GHz, the application of the concentrated type diodes is problematic. In this range it would seem to be promising to use bulk semiconductors. In this case surface-oriented p—i—n-structures can be applied as unified elements of the control devices in the shortwave part of the millimeter range, as well as in quasi-optical transmission lines.

Research on Multi-Stage Generation and Transmission Coordinated Planning Model Considering Wind Power Integration

Decentralized planning mode of power generation and power transmission is facing enormous challenges at present, and all kinds of uncertainties that impact on the planning have become increasingly evident. To solve the two coordinated planning and development issues is imminent, proposing a coordinated planning model of generation and transmission to improve system stability and flexibility and reduce the uncertainties whose threat is significant. Combined with the Stackelberg game theory, this proposes a two-stage coordinated planning model of generation and transmission, which can effectively provide decision makers with optimal program of investment decision, and control the investment risk of power system construction. And the this paper uses the Heuristic Artificial Fish Swarm Algorithm (HAFSA) to solve this model and illustrates our results using a 24-bus network example.

Proactive and reactive transmission power control for energy-efficient on-body communications.

In wireless body sensor network (WBSNs), the human body has an important effect on the performance of the communication due to the temporal variations caused and the attenuation and fluctuation of the path loss. This fact suggests that the transmission power must adapt to the current state of the link in a way that it ensures a balance between energy consumption and packet loss. In this paper, we validate our two transmission power level policies (reactive and predictive approaches) using the Castalia simulator. The integration of our experimental measurements in the simulator allows us to easily evaluate complex scenarios, avoiding the difficulties associated with a practical realization. Our results show that both schemes perform satisfactorily, providing overall energy savings of 24% and 22% for a case of study, as compared to the maximum transmission power mode.

Tracking/Erosion Resistance Analysis of Nano-Al(OH)3Filled Silicone Rubber Insulating Materials for High Voltage DC Applications

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano Al(OH)3 filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano- filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

Power System Planning and Analysis Data Model Research

Power system planning is according to the demand of the social and economic development, energy resources and load distribution, determine the reasonable power structure and strategy. Power grid voltage grade, transmission mode and reasonable space truss structure, etc. Although a large number of literature have studied various aspects of the power planning, but there are few literatures on power system planning comprehensive study, and just theoretical analysis, useless for practical application. This paper analyzes the load forecasting of power system planning, evaluation of power grid and economic evaluation, gives the basic data needed for the analysis and calculation,and provides theoretical guidance for the actual planning work. DOI : http://dx.doi.org/10.11591/telkomnika.v12i5.5112

Energy efficiency enhancement of two-way amplifier forward relaying with channel estimation error

In order to save energy consumption of two-way amplifier forward (AF) relaying with channel estimation error, an energy efficiency enhancement scheme is proposed in this work. Firstly, through the analysis of two-way AF relaying mode with channel estimation error, the resultant instantaneous SNRs at end nodes is obtained. Then, by using a high SNR approximation, outage possibility is acquired and its simple closed-form expression is represented. Specially, for using the energy resource more efficiently, a low-complexity power allocation and transmission mode selection policy is proposed to enhance the energy efficiency of two-way AF relay system. Finally, relay priority region is identified in which cooperative diversity energy gain can be achieved. The computer simulations are presented to verify our analytical results, indicating that the proposed policy outperforms direct transmission by an energy gain of 3 dB at the relative channel estimation error less than 0.001. The results also show that the two-way AF relaying transmission loses the two-way AF relaying transmission loses its superiority to direct transmission in terms of energy efficiency when channel estimation error reaches 0.03.

Voltage Stability Analysis of Wind Power Integrated System Based on Flexible HVDC

With the scale of integration of wind power increases gradually, the voltage stability and the fluctuation problem of the system caused by integration have become more and more prominent. Traditional AC power transmission mode cannot alleviate the adverse effects of integration of wind power, Flexible DC power transmission has many advantages due to the use of voltage source converters self-commutated characteristics, Flexible DC power provides a new technical method and also provides a solution for the integration. This paper introduces the basic structure and the basic control principle of Flexible DC power transmission technology. Then, through comparing the transient stability level and voltage supporting ability of AC power transmission with that of Flexible DC power transmission, an isolated system is used as an example to elaborate the beneficial contribution that the new integration of wind power make to the voltage stability, which indicates that Flexible DC power transmission technology has broad application prospect in the transmission area of wind power, and gives very good reference value for the Flexible DC power used in integration in the future.

Reconfigurable 1:3 power divider using coupled lines

A reconfigurable 1:3 power divider is presented using quarter-wave long coupled lines and switches. The proposed power divider allows dual operating mode, or a 1:3 power divider and 1:0 power transmission mode, by turning the switches on and off. To make a high power-division ratio of three realisable and improve the bandwidth, a microstrip-slot structure is adopted on a thick substrate with high dielectric constant. The measurement of the proposed power divider shows good return and insertion loss performance in both modes.

Reconfigurable un‐equal division power divider with the compact size for high efficiency power amplifiers

AbstractIn this letter, a reconfigurable un‐equal division two‐way power divider with the compact size is presented for high efficiency power amplifiers. It is based on the Wilkinson power divider of which the quarter‐wave long lines are replaced by coupled lines. Two ends of each coupled line are terminated with switches which provide the two modes of operation, or two‐way power divider and one‐way transmission line. These switches are used to adjust the characteristics of the coupled line in order to allow the good insertion and return loss performance in both modes. At the design frequency of 2.14 GHz, the fabricated 1:2 power divider showed the input return loss (S11) of −23.0 dB, isolation (S32) of −27.2 dB, and insertion loss of −5.05 dB (S21) and −2.25 dB (S31) in the power divider mode. The insertion loss (S21) was measured to be −0.90 dB with the return loss (S11) of −21.1 dB in the power transmission mode. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1662–1665, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23471