Adaptive VSG control of flywheel energy storage array for frequency support in microgrids

The application of virtual synchronous generator(VSG)control in flywheel energy storage systems(FESS)is an effective solution for addressing the challenges related to reduced inertia and inadequate power supply in microgrids.Considering the significant variations among individual units within a flywheel array and the poor frequency regulation performance under conventional control approaches,this paper proposes an adaptive VSG control strategy for a flywheel energy storage array(FESA).First,by leveraging the FESA model,a variable acceleration factor is integrated into the speed-balance control strategy to effectively achieve better state of charge(SOC)equalization across units.Furthermore,energy control with a dead zone is introduced to prevent SOC of the FESA from exceeding the limit.The dead zone parameter is designed based on the SOC warning intervals of the flywheel array to mitigate its impact on regular operation.In addition,VSG technology is applied for the grid-connected control of the FESA,and the damping characteristic of the VSG is decoupled from the primary frequency regulation through power differential feedback.This ensures optimal dynamic performance while reducing the need for frequent involvement in frequency regulation.Subsequently,a parameter design method is developed through a small-signal stability analysis.Consequently,considering the SOC of the FESA,an adaptive control strategy for the inertia damping and the P/ωdroop coefficient of the VSG control is proposed to optimize the grid support services of the FESA.Finally,the effectiveness of the proposed control methods is demonstrated through electromagnetic transient simulations using MATLAB/Simulink.

Microstructure and properties of 35 kg large aluminum alloy flywheel housing components formed by squeeze casting with local pressure compensation

The squeeze casting method with local pressure compensation was proposed to form a flywheel housing component with a weight of 35 kg.The numerical simulation,microstructure observation and phase characterization were performed,and the influence of local pressure compensation on feeding of thick-wall position,microstructure and mechanical properties of the formed components were discussed.Results show that the molten metal keeps a good fluidity and the filling is complete during the filling process.Although the solidification at thick-wall positions of the mounting ports is slow,the local pressure compensation effectively realizes the local forced feeding,significantly eliminating the shrinkage cavity defects.In the microstructure of AlSi9Mg alloy,α-Al primarily consists of fragmented dendrites and rosette grains,while eutectic Si predominantly comprises needles and short rods.The impact of local pressure compensation on strength is relatively minimal,yet its influence on elongation is considerable.Following local pressure compensation,the average elongation at the compensated areas is 9.18%,which represents a 44.90%higher than that before compensation.The average tensile strength is 209.1 MPa,and the average yield strength is 100.6 MPa.The local pressure compensation can significantly reduce or even eliminate the internal defects in the 35 kg large-weight components formed by squeeze casting.

小样本下基于改进麻雀算法优化卷积神经网络的飞轮储能系统损耗

飞轮储能系统具有待机损耗,不适合长期储能。针对飞轮损耗这一经济指标,基于飞轮储能系统运行的小样本数据,提出了一种结合Logistic混沌麻雀优化算法和卷积神经网络的飞轮损耗计算模型。首先,分析了飞轮损耗产生的原因;接下来对宁夏灵武电厂的飞轮运行数据进行预处理,并使用对抗生成网络进行小样本扩充;然后基于卷积神经网络建立损耗模型,使用改进的麻雀算法对模型超参数进行优化,并通过对比验证了该模型的优越性;最后通过仿真实验证明了该模型能够优化飞轮储能系统的出力,降低飞轮损耗。

基于rLADRC的磁悬浮高速飞轮储能转子系统振动抑制

针对电磁轴承支承的高速飞轮储能转子系统振动抑制问题,提出一种降阶线性自抗扰控制(rLADRC)方法。首先,建立考虑陀螺效应及不平衡力的刚性飞轮转子系统径向四自由度二阶数学模型;其次,将各自由度数学模型中本自由度项作为内部扰动,其他自由度项带来的耦合和不平衡力项作为外界扰动,进而设计降阶线性扩张状态观测器(LESO)对总扰动进行实时估计;最后,设计线性状态误差反馈控制律(LSEF)并对总扰动进行补偿。结果表明:rLADRC能够实现转子径向四自由度之间的有效解耦,与传统分散比例积分微分(PID)控制和线性自抗扰控制相比,具有良好的动态性能和较强的扰动抑制能力,可在全转速范围内实现飞轮转子系统的稳定悬浮和对振动的有效抑制。

飞轮壳体黏弹性阻尼环的仿真分析与试验研究

随着航天器平台性能指标要求的提高,飞轮微振动对航天器平台的影响越加突出,需要对其进行振动抑制。根据飞轮上壳体的模态特性,提出一种圆环形黏弹性阻尼环结构的设计方法,并针对黏弹性阻尼环的敷设位置、厚度、宽度对其减振效果影响规律进行数值仿真与试验验证,验证圆环形黏弹性阻尼环的有效性。结果表明:圆环形黏弹性阻尼环结构对宽频振动具有良好的减振效果,黏弹性阻尼环的敷设位置对飞轮系统的各阶固有频率变化和减振效果起决定性作用,在飞轮外径的60%处敷设圆环形黏弹性阻尼环减振效果较好,宽度设计为飞轮外径的6%以内、厚度设计为壳体厚度的4倍以内时,随着宽度、厚度的增加,减振效果提高。

相对化One-Way函数的存在性

One- Way函数在计算复杂性和密码技术中均有重要的应用 .将 Grollmann和 Selman的结果推广到相对化和非一致复杂类的情形 ,证明了复杂类 UP/ poly,UP,P/ poly等之间的包含关系与强相对化 one- way函数、弱相对化 one-

A new group key management scheme based on keys tree, XOR operation and one-way function

By introducing XOR operation and one-way function chains to group key management schemes based on the keys tree, a new group key management scheme based on the keys tree, XOR operation and one-way function chains is proposed. Initialization, member adding and member evicting operations are introduced. The new scheme is compared with three other group key management schemes which are based on the keys tree： SKDC, LKH, and OFF. As far as transmission, computation and storage costs are concerned, the performance of the new group key management scheme is the best. The security problem of the new scheme is analyzed. This new scheme provides backward and forward security, i.e.. newly admitted group members cannot read previous multicast messages and evicted members cannot read future multicast messages, even with collusion by many arbitrarily evicted members.

RESEARCH ON CONTROL OF FLYWHEEL SUSPENDED BY ACTIVE MAGNETIC BEARING SYSTEM WITH SIGNIFICANT GYROSCOPIC EFFECTS

Traditional PID controllers are no longer suitable formagnetic-bearing-supported high-speed flywheels with significant gyroscopic effects. Becausegyroscopic effects greatly influence the stability of the flywheel rotor, especially at highrotational speeds. Velocity cross feedback and displacement cross feedback are used to overcomeharmful effects of nutation and precession modes, and stabilize the rotor at high rotational speeds.Theoretical analysis is given to show their effects. A control platform based on RTLinut and a PCis built to control the active magnetic bearing (AMB) system, and relevant results are reported.Using velocity cross feedback and displacement cross feedback in a closed loop control system, theflywheel successfully runs at over 20000 r/min.

基于深度强化学习的轨交飞轮储能系统能量管理

随着城市化进程的加速和公共交通系统的发展,地铁系统的运营效率和能源利用效率受到越来越多的关注。飞轮储能技术凭借其高功率循环能力,为轨道交通系统的能源利用问题提供新的解决方案。该文采用马尔科夫决策过程来描述单飞轮储能系统的能量管理问题,并使用基于深度Q网络的强化学习算法来学习最优的充放电阈值动态调整策略。通过在Matlab/Simulink平台搭建仿真环境,对开发的能量管理算法进行测试,并将其结果与固定充放电阈值、随机充放电阈值策略进行对比,表明该策略在提高电能利用效率和系统运行稳定性方面具有显著效果。

Spacecraft Attitude Tracking and Energy Storage Using Flywheels

The control law of the flywheel in an integrated power and attitude control system （IPACS） for a spacecraft is investigated. The flywheels are used as attitude control actuators as well as energy storage device. A feedback control law for attitude tracking is firstly developed by using Lyapunov approach, and then a torque based control law of the flywheel is studied. The control torque vector of the flywheel is decomposed into three parts which are orthogonal to one another by using the method of singularity value decomposition （SVD）. One part is used to provide the attitude control torque, another part is used to store energy with given power, and the last part is used to accomplish wheel speed equalization to avoid wheel saturation caused by large difference among the wheel spin rates. A management scheme for energy storage power using kinetic energy feedback is proposed to keep energy balance, which can avoid wheel saturation caused by superfluous energy. Numerical simulation results demonstrate the effectiveness of the control scheme.

Accuracy analysis of the optimal separable approximation method of one-way wave migration

An approximation for the one-way wave operator takes the form of separated space and wave-number variables and makes it possible to use the FFT, which results in a great improvement in the computational efficiency. From the function approximation perspective, the OSA method shares the same separable approximation format to the one-way wave operator as other separable approximation methods but it is the only global function approximation among these methods. This leads to a difference in the phase error curve, impulse response, and migration result from other separable approximation methods. The difference is that the OSA method has higher accuracy, and the sensitivity to the velocity variation declines with increasing order.

One-way wave equation seismic prestack forward modeling with irregular surfaces

Mathematical geophone （MG） and equal-time stacking （ETS） principles are used to implement seismic prestack forward modeling with irregular surfaces using the oneway acoustic wave-equation. This method receives seismic primary reflections from the subsurface using a set of virtual MGs. The receivers can be located anywhere on an irregular observing surface. Moreover, the ETS method utilizes the one-way acoustic wave equation to easily and quickly image and extrapolate seismic reflection data. The method is illustrated using high single-noise ratio common shot gathers computed by numerical forward modeling of two simple models, one with a flat surface and one with an irregular surface, and a complex normal fault model. A prestack depth migration method for irregular surface topography was used to reoroduce the normal fault model with high accuracy.

Design and analysis of logarithmic spiral type sprag one-way clutch

A complete mathematical model for logarithmic spiral type sprag one-way clutch design and analysis is given.It assumes that the motion of all clutch components can be expressed by a model of epicyclic gearing.It takes advantage of Hunt-Crossley contact impact theory to calculate the contact forces between sprags and races,and it can be used for optimization of design and comparison with other types of sprag clutches.A good deal of analysis shows that the parameters of the steady windup angle,the steady contact force,the natural frequency and natural cycle of clutch have nothing to do with the initial velocity of outer race,while the parameters of the maximum transient windup angle,the maximum transient impact force and the steady engagement time increase linearly in the mode of engaging operation of clutch.It is also shown that the strut angle has great influence on the dynamic engagement performance of clutch.The parameters of the steady windup angle,the maximum transient windup angle,the steady engaging time,the steady contact force,the maximum transient impact force and the natural cycle of clutch decrease linearly nearly with the inner strut angle,while the natural frequency of the system increases linearly with the inner strut angle.

Pressure-impulse diagram with multiple failure modes of one-way reinforced concrete slab under blast loading using SDOF method

Two loosely coupled single degree of freedom (SDOF) systems were used to model the flexural and direct shear responses of one-way reinforced concrete slabs subjected to explosive loading. Blast test results show that the SDOF systems are accurate in predicting the failure mode of the slab under blast loads by incorporating the effects of the strain rate effect caused by rapid load application. Based on different damage criteria, pressure-impulse (P-I) diagrams of the two failure modes were analyzed with the SDOF systems. The effects of span length, concrete strength, and reinforcement ratio of the slab on the P-I diagram were also investigated. Results indicate that a slab tends to fail in direct shear mode when it is of a smaller span length and tends to fail in flexure mode when it is of a larger span length. With the increase of the concrete strength or reinforced ratio, both the flexure and shear capacity increase. Based on numerical results, a simplified method and a semi analytical equation for deriving the P-I diagram are proposed for different failure modes and damage levels.

Application of direct computing of one-way coupling technique in seismic analysis of concrete gravity dam

A dam-reservoir system subjected to an earthquake is a nonlinear system, because the fluid equations are always nonlinear regardless of the linear or nonlinear model used for the dam body. Therefore, transient analysis is necessary. In this study, dam-reservoir interaction during earthquake excitation was modeled by utilizing coupled finite element equations based on the Eulerian approach. Direct computing of the one-way coupling technique was used to solve the coupled equations. This technique is based on a simple assumption that the fluid hydrodynamic pressure is applied to the dam body while the deformation of the dam has no influence on the water field. Seismic response analysis of the Sonla concrete gravity dam constructed in Sonla Province, Vietnam was carried out as a verification example. The results of the methodology introduced are in close agreement with results of the iterative method and the solution procedure is found to be less time-consuming than that of the iterative method. This method is very convenient and can be easily implemented in finite element programs with fluid-structure interaction modules.

Reducing Fuel Consumption Using Flywheel Battery Technology for Rubber Tyred Gantry Cranes in Container Terminals

Flywheel Energy Storage System (FESS) is used as an energy regeneration system to help with reducing peak power requirements on RTG cranes that are used to load or unload container ships. Nevertheless, with the use of FESS, Port Operator can deploy undersized generator for new RTG as this will further reduce fuel consumption. This paper presents the investigation of the amount of energy and fuel consumption that can be reduced in Rubber Tyred Gantry (RTG) cranes in container terminals by the use of simulation. In addition, Variable Speed Generator is integrated to the simulation-hybridized RTG. Simulation results reveal that the total energy saving exceeded 30% relatively to conventional RTG. A hardware-in-loop system is introduced for the purpose of validating the simulation results. The hardware components procured include a FESS, a Variable Frequency Drive (VFD) and brake resistors.

A parametric bootstrap approach for one-way classification model with skew-normal random effects

In this paper,several properties of one-way classification model with skew-normal random effects are obtained,such as moment generating function,density function and noncentral skew chi-square distribution,etc.Based on the EM algorithm,we discuss the maximum likelihood(ML)estimation of unknown parameters.For testing problem of fixed effect,a parametric bootstrap(PB)approach is developed.Finally,some simulation results on the Type I error rates and powers of the PB approach are obtained,which show that the PB approach provides satisfactory performances on the Type I error rates and powers,even for small samples.For illustration,our main results are applied to a real data problem.

Integrated Power and Single Axis Attitude Control System with Two Flywheels

The existing research of the integrated power and attitude control system（IPACS） in satellites mainly focuses on the IPACS concept,which aims at solving the coupled problem between the attitude control and power tracking.In the IPACS,the configuration design of IPACS is usually not considered,and the coupled problem between two flywheels during the attitude control and energy storage has not been resolved.In this paper,an integrated power and single axis attitude control system using two counter rotating magnetically suspended flywheels mounted to an air table is designed.The control method of power and attitude control using flywheel is investigated and the coupling problem between energy storage and attitude control is resolved.A computer simulation of an integrated power and single axis attitude control system with two flywheels is performed,which consists of two counter rotating magnetically suspended flywheels mounted to an air rotary table.Both DC bus and a single axis attitude are the regulation goals.An attitude ＆ DC bus coordinator is put forward to separate DC bus regulation and attitude control problems.The simulation results of DC bus regulation and attitude control are presented respectively with a DC bus regulator and a simple PD attitude controller.The simulation results demonstrate that it is possible to integrate power and attitude control simultaneously for satellite using flywheels.The proposed research provides theory basis for design of the IPACS.

Application of simple array method in one-way traffic synthetic asessment

One-Way Traffic synthetic assessing can not only determine the assessment method, but can also provide an opportunity for further study of road systems. Comparing three Road Traffic Planning methods, which are Value Analysis method, Simple Array method and Step Analysis method, this paper concludes that Simple Array method has one prominent merit, avoiding the complicated relationship of various factors and simplifying the complex problem. Therefore Simple Array method is firstly presented in this paper to be the assessing measure to assess the One-Way Traffic Planning project. Although this assessing method cannot wholly give way to man’s will, through consistently testing on qualitative factors and with the decision-making results of a multi-program, this method is still an effective method. Using an example of Harbin One-Way Traffic planning, with seven assessing indexes including economic benefit index, Simple Array method is applied to synthetically assessing the program. This fully reflects the general function of One-Way Traffic planning program and objectively evaluates the program. It also proves that, as the method of One-Way Traffic synthetic assessing, Simple Array method is rational and practical.

Urban One-way Traffic Organization and Its Evaluation

One-way traffic organization is a direct, efficient and economic method to solve traffic congestion and expand traffie capacity. With its evolution, advantages and disadvantages introduced its setting conditions demonstrated. The general method and processes are summarized in planning for urban one-way streets project, viz. investigation, drawing out and evaluation of project, selecting of project and beneficial analysis. Fuzzy synthetical evaluation other fields is employed to evaluate the project. Its evaluation system and method is introduced and Delphi method is adopted to obtain evaluation index. Finally, taking Harbin city as an example, the application process of above-mentioned method is illuminated. Accordingly, it is proved that the method is exercisable.