Optimal Design of Wireless Power Transmission Systems Using Antenna Arrays

Three design methods for wireless power transmission(WPT)systems using antenna arrays have been investigated.The three methods,corresponding to three common application scenarios of WPT systems,are based on the method of maximum power transmission efficiency(MMPTE)between two antenna arrays.They are unconstrained MMPTE,weighted MMPTE,and constrained MMPTE.To demonstrate the optimal design process with the three methods,a WPT system operating at 2.45 GHz is designed,simulated,and fabricated,in which the transmitting(Tx)array,consisting of 36 microstrip patch elements,is configured as a square and the receiving(Rx)array,consisting of 5 patch elements,is configured as an L shape.The power transmission efficiency(PTE)is then maximized for the three application scenarios,which yields the maximum possible PTEs and the optimized distributions of excitations for both Tx and Rx arrays.The feeding networks are then built based on the optimized distributions of excitations.Simulations and experiments reveal that the unconstrained MMPTE,which corresponds to the application scenario where no radiation pattern shaping is involved,yields the highest PTE.The next highest PTE belongs to the weighted MMPTE,where the power levels at all the receiving elements are imposed to be equal.The constrained MMPTE has the lowest PTE,corresponding to the scenario in which the radiated power pattern is assumed to be flat along with the Rx array.

Catastrophe of Power Transmission System

Power systems are critical infrastructures in the same way as gas and oil networks, water networks, transportation networks, telecommunications systems and computer systems. These complex networked systems are increasingly interdependent on each other, as the digital society matures on a global scale. A typical example of a critical infrastructure vulnerability that undergoes rising vulnerability to catastrophic failure is the power transmission network. There are several reasons for such a situation to prevail. Firstly, as witnessed in developed countries, there has been a very slow expansion of the high voltage transmission grid during recent decades due to stringent regulations put forward in response to environmental concerns. Secondly, there are the profound structural reforms that the power industry has embarked on, which are geared toward the emergence and consolidation of competitive energy markets. In the evaluation of catastrophe of the power transmission system, the most important parameter to be taken into a consideration is resilience index of electro-magnet floury. In particular, it has been taken into consideration its effect on the different fields of human interest.

Cyber-physical Collaborative Restoration Strategy for Power Transmission System Considering Maintenance Scheduling

In order to improve the ability of power transmission system to cope with compound faults on the communication side and power side,a cyber-physical collaborative restoration strategy is proposed.First,according to the information system’s role in fault diagnosis,remote control of equipment maintenance and automatic output adjustment of generator restoration,a cyber-physical coupling model is proposed.On this basis,a collaborative restoration model of power transmission system is established by studying interactions among maintenance schedule paths,information system operation,and power system operation.Based on power flow linearization and the large M-ε method,the above model is transformed into a mixed integer linear programming model,whose computational burden is reduced further by the clustering algorithm.According to the parameters of IEEE39 New England system,the geographic wiring diagram of the cyber-physical system is established.Simulation results show the proposed restoration strategy can consider the support function of the information system and space-time coordination of equipment maintenance at both sides comprehensively to speed up load recovery progress.

Probabilistic steady-state and dynamic security assessment of power transmission system

Two-level system model based probabilistic steady-state and dynamic security assessment model is introduced in this paper.Uncertainties of nodal power injection caused by wind power and load demand,steady-state and dynamic security constraints and transitions between system configurations in terms of failure rate and repair rate are considered in the model.Time to insecurity is used as security index.The probability distribution of time to insecurity can be obtained by solving a linear vector differential equation.The coefficients of the differential equation are expressed in terms of configuration transition rates and security transition probabilities.The model is implemented in complex system successfully for the first time by using the following effective measures:firstly,calculating configuration transition rates effectively based on component state transition rate matrix and system configuration array;secondly,calculating the probability of random nodal power injection belonging to security region effectively according to practical parts of critical boundaries of security region represented by hyper-planes;thirdly,locating non-zero elements of coefficient matrix and then implementing sparse storage of coefficient matrix effectively;finally,calculating security region off-line for on-line use.Results of probabilistic security assessment can be used to conduct operators to analyze system security effectively and take preventive control.Test results on New England 10-generators and 39-buses power system verify the reasonableness and effectiveness of the method.

Human reliability analysis in maintenance team of power transmission system protection

The requirement for reliable electrical energy supply increases continuously because of its vital role in our lives.However,events due to various factors in the power grid can cause energy supply to be interrupted.One of these factors is human error and thus human reliability analysis is a serious element in the industry.The first step is to identify the roots of human error,on which there has been limited research in this area.In this paper,the potential and actual causes of human error in maintenance teams of power transmission system protection are identified and predicted within a framework of human factors analysis and classification system method.Then,human error factors are ranked to help improve human reliability.The proposed method is implemented in the Fars Electricity Maintenance Company.

Design considerations for electromagnetic couplers in contactless power transmission systems for deep-sea applications

In underwater applications of contactless power transmission(CLPT) systems,high pressure and noncoaxial operations will change the parameters of electromagnetic(EM) couplers.As a result,the system will divert from its optimum performance.Using a reluctance modeling method,we investigated the gap effects on the EM coupler in deep-sea environment.Calculations and measurements were performed to analyze the influence of high pressure and noncoaxial alignments on the coupler.It was shown that it is useful to set a relatively large gap between cores to reduce the influence of pressure.Experiments were carried out to verify the transferring capacity of the designed coupler and system for a fixed frequency.The results showed that an EM coupler with a large gap can serve a stable and efficient power transmission for the CLPT system.The designed system can transfer more than 400 W electrical power with a 2-mm gap in the EM coupler,and the efficiency was up to 90% coaxially and 87% non-coaxially in 40 MPa salt water.Finally,a mechanical layout of a 400 W EM coupler for the underwater application in 4000-m deep sea was proposed.

Optimal Design of Aperture Illuminations for Microwave Power Transmission with Annular Collection Areas

This work presents an optimal design method of antenna aperture illumination for microwave power transmission with an annular collection area.The objective is to maximize the ratio of the power radiated on the annular collection area to the total transmitted power.By formulating the aperture amplitude distribution through a summation of a special set of series,the optimal design problem can be reduced to finding the maximum ratio of two real quadratic forms.Based on the theory of matrices,the solution to the formulated optimization problem is to determine the largest characteristic value and its associated characteristic vector.To meet security requirements,the peak radiation levels outside the receiving area are considered to be extra constraints.A hybrid grey wolf optimizer and Nelder–Mead simplex method is developed to deal with this constrained optimization problem.In order to demonstrate the effectiveness of the proposed method,numerical experiments on continuous apertures are conducted;then,discrete arrays of isotropic elements are employed to validate the correctness of the optimized results.Finally,patch arrays are adopted to further verify the validity of the proposed method.

On Differentiation Among Pilot Signals of Multiple Mobile Targets in Retro-Reflective Beamforming for Wireless Power Transmission

An experimental study is conducted on several retro-reflective beamforming schemes for wireless power transmission to multiple wireless power receivers(referred to herein as“targets”).The experimental results demonstrate that,when multiple targets broadcast continuous-wave pilot signals at respective frequencies,a retro-reflective wireless power transmitter is capable of generating multiple wireless power beams aiming at the respective targets as long as the multiple pilot signals are explicitly separated from one another by the wireless power transmitter.However,various practical complications are identified when the pilot signals of multiple targets are not appropriately differentiated from each other by the wireless power transmitter.Specifically,when multiple pilot signals are considered to be carried by the same frequency,the wireless power transmission performance becomes heavily dependent on the interaction among the pilot signals,which is highly undesirable in practice.In conclusion,it is essential for a retro-reflective wireless power transmitter to explicitly discriminate multiple targets’pilot signals among each other.

Study on Wireless Power Transmission for Gastrointestinal Microsystems Based on Inductive Coupling

Wireless power transmission based on inductive coupling for remotely implanted micro devices has been considered in this paper. The receiving coil, integrated in microsystems and the external transmitting coil compose a loosely coupled transformer. The coupling coefficient was calculated and measured on spacing misalignments. The geometric size of transmitting coil was analyzed for the target of remotely delivering power. The received power was maximized by choosing appropriate value of frequency, tuning capacitance and the load resistance. A conventional full bridge rectifier circuit was employed to convert ac to dc voltage. The received dc power was up to 160 mW with a transmitting vohage of 5 Vrms when the receiving coil was placed at the center of the transmitting coil. This may meet the requirement of some microsystems for high power over a long time.

Wireless Laser Power Transmission System for Dynamic Target Using Rotation of Single Component

We design a novel wireless laser power transmission system in which the process of wireless power transmission to a dynamic target was completed based on the rotation of just one component.The design of this system not only reduces the loadbearing of the gimbal,but also avoids the degradation of beam quality caused by lens vibration when tracking dynamic targets.As a result,this WLPT system has been verified by tracking an unmanned aerial vehicle at 122 m away with an offset distance of±26.7 mm.We believe this system offers great potential in highpower,longdistance dynamic laser power transmission.

Real-Time Wind Speed Analysis at Wind-Damaged Tower of a Transmission Line

Affected by the Super Typhoon“Mangkhut,”a total of five base towers of a transmission line in the mountainous area of China collapsed.In this paper,a mathematical model is established based on the Shuttle Radar Topography Mission(SRTM)data near the accident tower.The measured wind speed in the plain area under the mountain is used as the calculation boundary condition.The wind speed at the top of the mountain is calculated by using a numerical simulation method.The design wind speed and calculated wind speed at the tower site are compared,and the influence of wind speed on tower position in this wind disaster accident is analyzed.

Manufacturing Development Emphases on Power Generation and Transmission Apparatus in 11th Five-Year Plan Period and Prospect to the Year 2020

Based on predictions on Chinese power development in the coming 20 years, this paper introduces the emphases and key technologies in power sources and power network construction, and puts for ward the major tasks and technological orientation for machinery manufacturers to supply qualified equipment to China power industry.

Statistics and Analysis on Reliability of HVDC Transmission Systems of SGCC

Reliability level of HVDC power transmission systems becomes an important factor impacting the entire power grid.The author analyzes the reliability of HVDC power transmission systems owned by SGCC since 2003 in respect of forced outage times,forced energy unavailability,scheduled energy unavailability and energy utilization eff iciency.The results show that the reliability level of HVDC power transmission systems owned by SGCC is improving.By analyzing different reliability indices of HVDC power transmission system,the maximum asset benef its of power grid can be achieved through building a scientif ic and reasonable reliability evaluation system.

CHAOTIC OSCILLATION OF ANONLINEAR POWER SYSTEM

For a nonlinear power transmission system, the residue calculus method is introduced and applied to study its heteroclinic bifurcation. There a cone region and a strip region of parameters are obtained, in which the power transmission system displays chaotic oscillation. This gives a theoretic analysis and a computational method for the purpose to control the nonlinear system with deviation stably running.

Damping Characteristic Analysis and Optimization of Wind-thermal-bundled Power Transmission by LCC-HVDC Systems

With the rapid development of renewable energy,wind-thermal-bundled power transmission by line-commutated converter based high-voltage direct current(LCC-HVDC)systems has been widely developed.The dynamic interaction mechanisms among permanent magnet synchronous generators(PMSGs),synchronous generators(SGs),and LCC-HVDC system become complex.To deal with this issue,a path analysis method(PAM)is proposed to study the dynamic interaction mechanism,and the damping reconstruction is used to analyze the damping characteristic of the system.First,based on the modular modeling,linearized models for the PMSG subsystem,the LCC-HVDC subsystem,and the SG subsystem are established.Second,based on the closed-loop transfer function diagram of the system,the disturbance transfer path and coupling relationship among subsystems are analyzed by the PAM,and the damping characteristic analysis of the SG-dominated oscillation mode is studied based on the damping reconstruction.Compared with the PAM,the small-signal model of the system is obtained and eigenvalue analysis results are presented.Then,the effect of the control parameters on the damping characteristic is analyzed and the conclusions are verified by time-domain simulations.Finally,the penalty functions of the oscillation modes and decay modes are taken as the objective function,and an optimization strategy based on the Monte Carlo method is proposed to solve the parameter optimization problem.Numerical simulation results are presented to validate the effectiveness of the proposed strategy.

High Precision Ultrasonic Guided Wave Technique for Inspection of Power Transmission Line

Due to the merits of high inspection speed and long detecting distance, Ultrasonic Guided Wave（UGW） method has been commonly applied to the on-line maintenance of power transmission line. However, the guided wave propagation in this structure is very complicated, leading to the unfavorable defect localization accuracy. Aiming at this situation, a high precision UGW technique for inspection of local surface defect in power transmission line is proposed. The technique is realized by adopting a novel segmental piezoelectric ring transducer and transducer mounting scheme, combining with the comprehensive characterization of wave propagation and circumferential defect positioning with multiple piezoelectric elements. Firstly, the propagation path of guided waves in the multi-wires of transmission line under the proposed technique condition is investigated experimentally. Next, the wave velocities are calculated by dispersion curves and experiment test respectively, and from comparing of the two results, the guided wave mode propagated in transmission line is confirmed to be F（1,1） mode. Finally, the axial and circumferential positioning of local defective wires in transmission line are both achieved, by using multiple piezoelectric elements to surround the stands and send elastic waves into every single wire. The proposed research can play a role of guiding the development of highly effective UGW method and detecting system for multi-wire transmission line.

X-BAND CIRCULARLY POLARIZED RECTENNAS FOR MICROWAVE POWER TRANSMISSION APPLICATIONS

Circularly polarized rectennas operating at X-band are studied in this paper. The quasi-square patches fed by aperture coupling are used as the circularly polarized receiving antennas, which are easily matched and integrated with the circuits of rectennas. The double-layer structure not only minimizes the size of the rectennas but also decreases the effects of the circuits on the an- tenna. The receiving elements have broader bandwidth and higher gain than the single-layer patches. Two rectennas operating at 10GHz are designed, fabricated and measured. The voltage of 3.86V on a load of 200? is measured and a high RF-DC conversion efficiency of 75% is obtained at 9.98GHz. It is convenient for this kind of rectennas to form large arrays for high power applications.

Vibration Characteristics and Power Transmission of Coupled Rectangular Plates with Elastic Coupling Edge and Boundary Restraints

Coupled-plate structures are widely used in the practical engineering such as aeronautical,civil and naval engineering etc.Limited works can be found on the vibration of the coupled-plate structure due to the increased mathematical complexity compared with the single plate structure.In order to study analytically the vibration characteristics and power transmission of the coupled-plate structure,an analytical model consisting of three coupled plates elastically restrained along boundary edges and elastically coupled with arbitrary angle is considered,in which four groups of springs are distributed consistently along each edge of the model to simulate the transverse shearing forces,bending moments,in-plane longitudinal forces and in-plane shearing forces separately.With elastic coupling condition and general boundary condition of both flexural and in-plane vibrations taken into account by setting the stiffness of corresponding springs,the double Fourier series solution to the dynamic response of the structure was obtained by employing the Rayleigh-Ritz method.In order to validate the model,the natural frequency and velocity response of the model are firstly checked against results published in literatures and the ANSYS data,and good agreement was observed.Then,numerical simulation of the effects of several relevant parameters on the vibration characteristics and power transmission of the coupled structure were performed,including boundary conditions,coupling conditions,coupling angle,and location of the external forces.Vibration and energy transmission behaviors were analyzed numerically.The results show that the power transmission can be significantly influenced by the boundary restraints and the location of excitation.When the excitation is located at the central symmetry point of the model,the energy flow shows a symmetrical distribution.Once the location deviates from the central symmetry point,the power circumfluence occurs and the vortex energy field is formed at high frequency.

Reduction of electric field strength by two species of trees under power transmission lines

Electrical pollution is a worldwide concern,because it is potentially harmful to human health.Trees not only play a significant role in moderating the climate,but also can be used as shields against electrical pollution.Shielding effects on the electric field strength under transmission lines by two tree species,Populus alba and Larix gmelinii,were examined in this study.The electrical resistivity at different heights of trees was measured using a PiCUS sonic tomograph,which can image the electrical impedance for trees.The electric field strength around the trees was measured with an elf field strength measurement system,HI-3604,and combined with tree resistivity to develop a model for calculating the electric field intensity around trees using the finite element method.In addition,the feasibility of the finite element method was confirmed by comparing the calculated results and experimental data.The results showed that the trees did reduce the electric field strength.The electric field intensity was reduced by 95.6%,and P.alba was better than L.gmelinii at shielding.

Analysis of the compound split transmission based on the four-port power split device

In order to identify all the appropriate system schemes for the compound split systems formed primarily with a four-port mechanical power split device, power transmission characteristics of the compound split systems was analyzed. Considering the structural symmetry and according to the different connection arrangement of the four ports, compound split system was classified into four types. Using black-box modeling method, the generalized models of the speed ratio, the torque ratio and the power split ratio were established. Moreover, a semi-invert diagram was used to distin- guish the different schemes in each type. The characteristics of the speed ratio, the torque ratio and the power split ratio in each domain were also analyzed and compared. Through the semi-invert dia- gram, a selection method based on the rated-power speed ranges in different schemes was presented and all suitable compound split systems were identified, which can be used as references for the scheme selection of this kind of continuously variable power split transmission.