Parameter Design of Current Double Closed Loop for T-Type Three-Level Grid-Connected Inverter

To reduce current harmonics caused by switching frequency,T-type grid-connected inverter topology with LCL filter is adopted.In view of the disadvantages of the slow response speed of the traditional current control and the failure to eliminate the influence of the LCL filter on the grid-connected current by using current PI control alone,a current double closed loop PI current tracking control is proposed.Through the theoretical analysis of the grid-connected inverter control principle,the grid-connected inverter control model is designed,and the transfer functionmodel of each control link is deduced,and the current loop PI regulator is designed at last.The simulation results show that the control strategy is feasible.

EFFECTIVE DOUBLE LOOP CONTROL FOR A SQUARE WAVE BRUSHLESS DC MOTOR

A new type of brushless DC motor has been developed by using a square wave rare earth permanent magnet synchronous motor with its double loop control circuit. The double loop control scheme of the drive system yields a combination of desired characteristics including simplified control structure, small ripple torque, high speed accuracy, wide operating speed range, and fast dynamic response. Experimental results confirm excellent characteristics of the motor.

Endoscopic treatment of efferent loop syndrome with insertion of double pigtail stent

Efferent loop syndrome is a very rare postgastrectomy syndrome that can occur following Billroth-Ⅱor Rouxen-Y reconstruction.The most common loop syndrome after gastric surgery is afferent loop syndrome;however,efferent loop syndrome has been reported in rare cases.Here,we report a case of efferent loop obstruction that occurred after postoperative adhesiolysis of a small-bowel obstruction.The patient had undergone a partial gastrectomy with BillrothⅡanastomosis and gastric ulcer perforation 30 years prior.The efferent loop obstruction was successfully resolved by the insertion of a double pigtail stent.To the best of our knowledge,this is the first case in the literature describing the treatment of efferent loop obstruction.

The Singularities of Gravitational Fields of Static Thin Loop and Double Spheres Reveal the Impossibility of Singularity Black Holes

In the classical Newtonian mechanics, the gravity fields of static thin loop and double spheres are two simple but foundational problems. However, in the Einstein’s theory of gravity, they are not simple. In fact, we do not know their solutions up to now. Based on the coordinate transformations of the Kerr and the Kerr-Newman solutions of the Einstein’s equation of gravity field with axial symmetry, the gravity fields of static thin loop and double spheres are obtained. The results indicate that, no matter how much the mass and density are, there are singularities at the central point of thin loop and the contact point of double spheres. What is more, the singularities are completely exposed in vacuum. Space near the surfaces of thin loop and spheres are highly curved, although the gravity fields are very weak. These results are inconsistent with practical experience and completely impossible. By reasonable analogy, black holes with singularity in cosmology and astrophysics are something illusive. Caused by the mathematical description of curved space-time, they do not exist in real world actually. If there are black holes in the universe, they can only be the types of the Newtonian black holes without singularities, rather than the Einstein’s singularity black holes. In order to escape the puzzle of singularity thoroughly, the description of gravity should return to the traditional form of dynamics in flat space. The renormalization of gravity and the unified description of four basic interactions may be possible only based on the frame of flat space-time. Otherwise, theses problems can not be solved forever. Physicists should have a clear understanding about this problem.

Different oxidation routes for lattice oxygen recovery of double-perovskite type oxides LaSrFeCoO6 as oxygen carriers for chemical looping steam methane reforming

Double-perovskite type oxide LaSrFeCoO（LSFCO） was used as oxygen carrier for chemical looping steam methane reforming（CL-SMR） due to its unique structure and reactivity. Two different oxidation routes,steam-oxidation and steam-air-stepwise-oxidation, were applied to investigate the recovery behaviors of the lattice oxygen in the oxygen carrier. The characterizations of the oxide were determined by X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, hydrogen temperature-programmed reduction（H-TPR） and scanning electron microscopy（SEM）. The fresh sample LSFCO exhibits a monocrystalline perovskite structure with cubic symmetry and high crystallinity, except for a little impurity phase due to the antisite defect of Fe/Co disorder. The deconvolution distribution of XPS patterns indicated that Co,and Fe are predominantly in an oxidized state(Feand Fe) and(Coand Co), while O 1s exists at three species of lattice oxygen, chemisorbed oxygen and physical adsorbed oxygen. The double perovskite structure and chemical composition recover to the original state after the steam and air oxidation, while the Co ion cannot incorporate into the double perovskite structure and thus form the CoO just via individual steam oxidation. In comparison to the two different oxidation routes, the sample obtained by steam-oxidation exhibits even higher CHconversion, CO and Hselectivity and stronger hydrogen generation capacity.

A new algorithm for diameter of double loop network

Presents a new algorithm for diameter of double loop network(DLN) by which two new classes of infinite families of tight DLN of the known twelve infinie families of tight DLNs, under 3.3 in [1] including eleven are constructed.

A Routing Algorithm for Distributed Optimal Double Loop Computer Networks

A routing algorithm for distributed optimal double loop computer networks is proposed and analyzed. In this paper, the routing algorithm rule is described, and the procedures realizing the algorithm are given. The proposed algorithm is shown to be optimal and robust for optimal double loop. In the absence of failures,the algorithm can send a packet along the shortest path to destination; when there are failures,the packet can bypasss failed nodes and links.

DISTRIBUTED OPTIMAL LOCAL DOUBLE LOOP NETWORK

A distibuted optimal local double loop(DOLDL) network is presented. Emphasis is laid on the topology and distributed routing algorithms for the DOLDL. On the basis of building an abstract model, a set of definitions and theorems are described and proved. An algorithm which can optimize the double loop networks is presented. The optimal values of the topologic parameters for the DOLDL have been obtained by the algorithm, and these numerical results are analyzed. The study shows that the bounds of the optimal diameter (d) and average hop distance (a) for this class of networks are [square-root 3N -2] less-than-or-equal-to d less-than-or-equal-to [square-root 3N+1] and (5N/9(N-1)) (square-root 3N-1.8) < a < (5N/9 (N-1)). (square-root 3N - 0.23), respectively (N is the number of nodes in the network. (3 less-than-or-equal-to N less-than-or-equal-to 10(4)). A class of the distributed routing algorithms for the DOLDL and the implementation procedure of an adaptive fault-tolerant algorithm are proposed. The correctness of the algorithm has been also verified by simulating.

A double closed loop APFC control with feed-forward

In order to improve the steady state performance,dynamic response and power factor of traditional power factor correction(PFC)digital control method and reduce the harmonic distortion of input current,a double closed loop active power factorcorrection(APFC)control method with feed-forward is proposed.Firstly,the small signal model of Boost PFC control systemis built and the system transfer function is deduced,and then the parameters of the main device with Boost topology is estimated.By means of the feed-forward,the system can quickly respond to the change in input voltage.Furthermore,the use ofvoltage loop and current loop can achieve input current and output voltage regulation Simulink modeling shows that this methodcan effectively control the output voltage in case of input voltage largely fluctuating,improve the system dynamic response abilityand input power factor,and reduce the input current harmonic distortion

Modeling and Analysis of Submerged Arc Weld Power Supply Based on Double Closed-Loop Control

According to the soft-switching pulsed SAW (Submerged arc weld) weld power supply based on the double closed-loop constant current control mode, a small signal mathematic model of main circuit of soft-switching SAW inverter was established by applying the method of three-terminal switching device modeling method, and the math-ematic model of double closed-loop phase-shift control system circuit was established by applying the method of state-space averaging method. Dynamic performance of the inverter was analyzed on base of the established math-ematic model, and the tested wave of dynamic performance was shown by experimentation. Research and experimentation show that relation between structure of the power source circuit and dynamic performance of the controlling system can be announced by the established mathematic model, which provides development of power supply and optimized design of controlling parameter with theoretical guidance.

DOUBLE LOOP ACTIVE VIBRATION CONTROL OF PNEUMATIC ISOLATOR WITH TWO SEPARATE CHAMBERS

A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.

AN ASYMPTOTIC PROPERTY OF THE NUMBER OF SPANNING TREES OF DOUBLE FIXED STEP LOOP NETWORKS

Let T(C(p,1,q)) be the number of spanning trees of circulant graph C(p,1,q). In this note we show that T(C(p+1,1,q))T(C(p,1,q))→2, p→+∞.

Double Integrable Couplings and Their Constructing Method

To extend the study scopes of integrable couplings, the notion of double integrable couplings is proposed in the paper. The zero curvature equation appearing in the constructing method built in the paper consists of the elements of a new loop algebra which is obtained by using perturbation method. Therefore, the approach given in the paper has extensive applicable values, that is, it applies to investigate a lot of double integrable couplings of the known integrable hierarchies of evolution equations. As for explicit applications of the method proposed in the paper, the double integrable couplings of the AKNS hierarchy and the KN hierarchy are worked out, respectively.

External Bifurcations of Double Heterodimensional Cycles with One Orbit Flip

In this paper, external bifurcations of heterodimensional cycles connecting three saddle points with one orbit flip, in the shape of “∞”, are studied in three-dimensional vector field. We construct a poincaré return map between returning points in a transverse section by establishing a locally active coordinate system in the tubular neighborhood of unperturbed double heterodimensional cycles, through which the bifurcation equations are obtained under different conditions. Near the double heterodimensional cycles, the authors prove the preservation of “∞”-shape double heterodimensional cycles and the existence of the second and third shape heterodimensional cycle and a large 1-heteroclinic cycle connecting with P1 and P3. The coexistence of a 1-fold large 1-heteroclinic cycle and the “∞”-shape double heterodimensional cycles and the coexistence conditions are also given in the parameter space.

Magnetic properties of La2CuMnO6 double perovskite ceramic investigated by Monte Carlo simulations

We present a theoretical study of the magnetic properties of the lanthanum copper manganate double perovskite La2CuMnO6 ceramic,using Monte Carlo simulations.We analyze and discuss the ground state phase diagrams in different planes to show the effect of every physical parameter.Based on the Monte Carlo simulations,which combine Metropolis algorithm and Ising model,we explore the thermal behavior of the total magnetization and susceptibility.We also present and discuss the influence of physical parameters such as the external magnetic field,the exchange coupling interactions between magnetic atoms,and the exchange magnetic field on the magnetization of the system.Moreover,the critical temperature of the system is about Tc=70 K,in agreement with the experimental value.Finally,the hysteresis loops of La2CuMnO6 are discussed.

Explore the Mystery of the Origin of the Double Helix and the Biomembrane

In nature, the most possible reason that helix is chosen as the basic structure of life molecule is based on its simplest chiral three-dimensional structure. The process of the conversion from chemical molecules to double helical molecules is completed by the topology effect which belongs to the simplest way to form helix, and no external power is needed;moreover, the energy of double helix has fixed drive direction [1]. The dual-branch loop helix (II)—the transition state of double helix has many uses, for example, it can be turned to double helix, and it may be broken into two fragments of a and b which can construct more complicated structures. So the dual- branch loop helix (II) can provide special "building block" of assembling biomembrane and other life molecules.

基于全光混沌注入双环电光相位反馈环的混沌保密通信系统研究

针对现有混沌保密光通信系统时延特征隐藏所需反馈增益系数较大这一问题,设计了一种基于全光混沌注入双环电光相位反馈环的混沌保密通信系统。首先,由全光反馈产生光混沌并将其耦合至2个电光相位混沌反馈环中。然后,通过相位调制的方式实现信息与混沌载波的非线性耦合并参与混沌载波的生成。最后,在检测端通过光混沌同步实现信号的解密。借助MATLAB软件仿真分析了系统中混沌信号的复杂度、时延特征隐藏、同步性、鲁棒性和通信性能。仿真结果表明,所设计的混沌保密通信系统在较小的反馈系数时具有较高的复杂度且时延特征得到较好的隐藏。

基于功率转速双闭环的增程器发电功率动态控制策略

针对电动汽车内燃发电增程器发电功率动态控制存在的控制精度不高、响应滞后和反向超调等问题,提出并设计了一种结合功率/转速双闭环的增程器发电功率动态控制策略。该策略基于高效运行曲线进行发电功率的转矩/转速解耦,同时考虑了基于实际发电功率反馈的内燃机目标发电转矩修正、发电转矩转速动态协调修正。变工况发电试验结果表明,增程器发电过程中的发电功率最大正向超调为1.37 kW,最大反向超调为1.89 kW,稳态误差均小于0.01 kW,功率上升响应时间约为2.5 s,功率下降响应时间约为2.8 s,且工作点均在高效运行曲线附近。该增程器发电功率动态控制策略能够减少瞬态发电功率的响应滞后和反向超调的问题,在工程实践中具备可行性。

一种适用于复杂电网下的高精度锁相环

针对现有并网逆变器在电网电压谐波复杂的情况下难以精确锁定电压频率和相位的问题,结合传统锁相环结构与自适应算法的理论提出一种高精度的锁相方法。依据对传统锁相环在复杂电网下的弊端分析,确定了锁相环采用传统低通滤波器、带通滤波器时的滤波效果与延时的矛盾关系。根据最小均方算法的高自适应特性与快速跟踪特点,结合锁相环中坐标变换公式,确定算法的输入输出以及权重矩阵,构建基于派克变换的最小均方算法矩阵模型。通过将所需的电压正序分量设置为不断更新的权重矩阵来进行高精度的滤波,同时通过引入均方瞬时误差和自相关估计均值来进行变步长控制,提高滤波更新速度,以适用于复杂程度不确定的电网电压进行自适应滤波锁相。对仿真和样机实验的结果表明:采用基于派克变换的最小均方算法的改进型双二阶广义积分锁相方法,可以在不降低动态响应速度的前提下,提高锁相环的滤波效果,进而提高并网逆变器在电网畸变严重场景下锁定电压频率和相位的跟踪精度。

基于占空比波表的三相四线整流器控制

三相脉宽调制(PWM)整流器应用广泛。针对三相四线(TPFW)PWM整流器,提出了一种基于占空比波表的电压电流双闭环控制策略。该控制策略电压外环采用波表系数步进调节控制,电流内环采用离散比例积分微分(PID)控制叠加电容电压步进调节均衡控制。该方法能够提高系统功率因数,同时也能抑制整流器输出直流侧电压波动以及实现电容电压均衡。最后在硬件平台上进行实验验证,实验结果表明该控制策略具有抑制输出电压纹波、功率因数高、系统稳定性好等优点。与传统方法相比,该控制方法控制简单,易于工程实践.