双U/f下垂控制下双极MMC-HVDC系统交流阻抗建模及稳定性分析

基于模块化多电平换流器的高压柔性直流输电系统(modular multilevel converter-based high voltage direct current,MMC-HVDC)常采用双极接线方式以提高系统功率输送能力和可靠性。然而目前对于风电场经柔直外送系统的稳定性研究集中于单极接线方式,孤岛直驱风电场与采用不同双极协调控制的双极MMC-HVDC互联系统小信号稳定性问题还有待进一步探究。该文首先考虑频率耦合特性、参考系初相位和直流侧耦合特性的影响,分别建立了采用双U/f下垂控制和定U/f-P/Q控制的双极MMC-HVDC系统交流侧等效SISO阻抗模型,并详细分析了金属回线阻抗和双极间功率均分度对交流阻抗特性的影响。接着对比研究了两种协调控制中共有控制环路和特有控制环路对交流侧负电阻特性及互联系统稳定性的影响规律。最后,孤岛直驱风电场经两种双极协调控制下双极MMC-HVDC外送系统Matlab/Simulink时域仿真结果和硬件在环半实物实时仿真实验结果验证了所提出的小信号阻抗模型的精确性和稳定性分析结论的有效性。

UHF波段功率放大器设计

为某UHF波段的发射机设计一款己类功率放大器,工作于频段430~455 MHz,介绍了谐波控制和匹配网络的设计。在放大器输出匹配网络前添加谐波控制电路,通过对晶体管漏极的谐波控制生成己类放大器的工作波形。同时,在输入、输出阻抗是复阻抗的情况下,使用简化实频技术对电路进行匹配,提高了匹配网络的效率。测试结果显示,该放大器输出功率达60 dBm,对应的增益为20 dB,PAE为79%,达到设计要求。

船舶永磁同步推进电机的优化I/f起动控制方法

为解决高转矩与高转动惯量的船舶推进电机在开环I/f控制中转速和转矩波动大、电机易失步、效率低的问题,提出一种I/f控制改进方法。通过建立转矩角观测器,调节给定电流矢量的幅值,使其跟随负载转矩变化,提高系统鲁棒性。同时,将电机运行状态推进至接近最大转矩电流比状态,提高电机的运行效率;通过瞬时有功功率调节电流矢量的角速度,降低电磁转矩波动,加快电机的转速收敛过程。最后,在Matlab/Simulink中进行仿真实验,实验结果表明该方法可以显著提高推进电机运行效率和稳定性。

Transient Air-Fuel Ratio Control in a CNG Engine Using Fuzzy Neural Networks

The fuzzy neural networks has been used as means of precisely controlling the air-fuel ratio of a lean-burn compressed natural gas (CNG) engine. A control algorithm, without based on engine model, has been (utilized) to construct a feedforward/feedback control scheme to regulate the air-fuel ratio. Using fuzzy neural networks, a fuzzy neural hybrid controller is obtained based on PI controller. The new controller, which can adjust parameters online, has been tested in transient air-fuel ratio control of a CNG engine.

Preliminary Design of Control Network for HT-7U Tokamak Cryogenic System

In the course of the cryoplant modernization, a control network will be set up in order to facilitate the control, the supervision, the centralized data acquisition and the alarm handling of the cryogenic system for HT-7U tokamak. The paper introduces the preliminary design of control network based on the Controller Link Network for HT-7U tokamak cryogenic system. The multi-layer structure mentioned in the paper is the mainstream of automatic control. The control philosophy, the structure of the network and the components for control are also presented.

The Paralleling of High Power High Frequency Amplifier Based on Synchronous and Asynchronous Control

The vertical position of plasma in the HT-7U Tokamak is inherently unstable. In order to realize active stabilization, the response rate of the high-power high-frequency amplifier feeding the active control coils must be fast enough. This paper analyzes the paralleling scheme of the power amplifier through two kinds of control mode. One is the synchronous control; the other is the asynchronous control. Via the comparison of the two kinds of control mode, both of their characteristics are given in the text. At last, the analyzed result is verified by a small power experiment.

Relationship between Tomato (Solanum lycopersicum) Nutrition and the Severity of the Vascular Fusariosis

The vascular fusariosis is one of the main obstacles in the tomato crop production. Currently, the management of the nutrient solution is presented as a control option for fusariosis, for such reason different nutrient solutions with nitrogen (N), phosphorus (P), potassium (K) and calcium (Ca) modifications;in four saladette tomato varieties Bony Best (BB), Manapal (M), Walter (W) and FLA were evaluated in this research, in order to analyze the damage caused by Fusarium oxysporum f.sp. lycopersici (FOL) severity. Tomato plants were inoculated with 3 FOL breeds, establishing a completely random design with a factorial arrangement with six repetitions. Disease’s severity was evaluated 30 days after the inoculation using levels of (0 - 4) of the methodology established by Marlatt and Correll (1988). Afterwards, a statistical analysis was done through the Kruskal Wallis test, in which it was observed that treatments 93 (Ca 207 mg∙L-1, R3, variety BB), 95 (207 mg∙L-1 Ca, R3, variety W), 81 (0Ca, R3, BB) showed less disease severity. In the foliar analysis, the best treatments were 22 (193 mg∙L-1 N, R3, M) for N, the greatest P content was treatment 94 (207 mg∙L-1 Ca, R3, M) for K treatment three and 93 (207 mg∙L-1 Ca, R3, variety BB) greatest Ca content.

The Main Diseases and Control Measures of Panax notoginseng(Burk) F. H. Chen in Wuzhou City

The main symptoms of root rot,anthracnose,blight and damping-off of Panax notoginseng( Burk) F. H. Chen are introduced in the paper,and the corresponding control measures are elaborated from the aspects of agricultural management measures,seed disinfection,seedbed treatment and chemical control.

基于色散调控氟碲酸盐玻璃光纤的O-U波段平坦光频梳产生

光学频率梳(简称光频梳)作为一种优秀的多波长光源在通信领域具有巨大的应用潜力。通过将光频梳光源与波分复用技术(WDM)、空分复用技术结合(SDM),通信系统可以具有百Tbit/s量级的传输速率,在5G/6G通信、物联网、自动驾驶等方面具有重要的应用价值。目前实现光频梳的方法主要有以下四种,分别为基于锁模激光器产生飞秒光频梳、基于光学微腔产生光频梳、基于电光调制器产生光频梳以及基于行波四波混频产生光频梳。它们各具特点,但均很难同时实现宽光谱、高信噪比、高平坦度、高的单梳齿功率以及梳齿频率间隔大范围可调,这在一定程度上影响了光频梳在光通信领域的应用。本文提出基于受激布里渊激光腔产生种子梳,采用腔外负色散光纤进行脉冲压缩,进一步利用色散调控的高非线性氟碲酸盐光纤进行扩谱,从而实现光频梳产生。数值计算结果表明,通过该系统,我们可以得到重复频率大范围可调、光谱覆盖整个O-U波段且在O-U波段梳齿强度标准差小于5 dB的平坦光频梳,证明了通过基于布里渊激光腔与色散调控高非线性氟碲酸盐光纤的光学系统产生可用于光通信的平坦光频梳的可行性。

Interval Type-2 Fuzzy Hierarchical Adaptive Cruise Following-Control for Intelligent Vehicles

Intelligent vehicles can effectively improve traffic congestion and road traffic safety.Adaptive cruise followingcontrol(ACFC)is a vital part of intelligent vehicles.In this paper,a new hierarchical vehicle-following control strategy is presented by synthesizing the variable time headway model,type-2 fuzzy control,feedforward+fuzzy proportion integration(PI)feedback(F+FPIF)control,and inverse longitudinal dynamics model of vehicles.Firstly,a traditional variable time headway model is improved considering the acceleration of the lead car.Secondly,an interval type-2 fuzzy logic controller(IT2 FLC)is designed for the upper structure of the ACFC system to simulate the driver's operating habits.To reduce the nonlinear influence and improve the tracking accuracy for the desired acceleration,the control strategy of F+FPIF is given for the lower control structure.Thirdly,the lower control method proposed in this paper is compared with the fuzzy PI control and the traditional method(no lower controller for tracking desired acceleration)separately.Meanwhile,the proportion integration differentiation(PID),linear quadratic regulator(LQR),subsection function control(SFC)and type-1 fuzzy logic control(T1 FLC)are respectively compared with the IT2 FLC in control performance under different scenes.Finally,the simulation results show the effectiveness of IT2 FLC for the upper structure and F+FPIF control for the lower structure.

基于模糊解耦策略的小型注塑机料筒温度F-PI复合控制器

在塑料产品的生产过程中,注塑机料筒温度的响应速度和稳定性对最终塑料产品的质量具有重要影响。为了提高小型注塑机料筒温度的控制精度,针对料筒具有的惯性大、非线性、大滞后、强耦合等温度特性,在模糊控制不能满足控制要求的背景下,提出了基于相邻加热段之间温差的模糊解耦策略,通过利用相邻加热段之间的温差信息,建立模糊解耦控制器,对各段料筒之间的温度耦合进行解耦控制。实验结果表明,该控制方法效果良好,达到目标温度所用时间为1092 s,最大超调量只有3%,但稳态性能较差。为解决稳态性能较差的问题,在模糊解耦的基础上建立F-PI复合控制器,通过引入积分环节消除系统在稳态下的偏差。在Matlab/Simulink环境下进行仿真并在注塑机上进行验证,结果表明,F-PI复合控制方法不仅具有良好的动态响应,还具有更高的稳态精度,稳态偏差仅为±1℃。因此基于模糊解耦策略的F-PI复合控制方法不仅能对料筒的温度耦合进行解耦控制,还有效提高了系统的稳定性和控制精度,具有良好的鲁棒性。

孤岛微电网电流同步U-I下垂控制方法

采用电压-电流(U-I)下垂控制的孤岛微电网系统始终运行于工频频率,避免了传统下垂控制存在的频率偏差及频率越限问题,但电源间易产生环流,功率分配精度差。为此,提出电流同步U-I下垂控制方法,该方法由电流同步控制及U-I幅值下垂控制两部分构成。前者通过调节输出电压相角使各电源输出电流相角一致,以抑制电源间环流;后者依据输出电流的幅值调节输出电压的幅值,使各电源出力依据自身容量分配。在此基础上,建立双端系统的小信号模型,分析电流同步控制环路中控制参数对系统稳定性的影响,为参数设计提供依据。仿真及实验结果表明,相比U-I下垂控制,所提方法的系统环流减小50%以上,电压畸变率改善近10%,电源间功率分配精度及系统电能质量均得到明显提升。

Identification of Biocontrol Strain HJX1 and Determination of Its Antifungal Spectrum

A biocontrol strain HJX1,which had good inhibitory effect against Fusarium oxysporum f. sp. cubense,was identified as Bacillus subtilis based on traditional morphology,16 S rRNA gene sequence and fatty acid profiles. The sequence of 16 S rRNA gene had 99% homology to B. subtilis according to the DNA fragment of 1 521 bp amplified with a pair of universal primers,P0 and P6,of bacteria. Confront culture with pathogenic fungi showed that this strain had good inhibitory effect against 10 pathogenic fungi.

Transferring in control plane for 5G heterogeneous networks

The heterogeneous network with the separation of the control plane and user plane(C/U) is an evolutionary approach to the fifth generation(5 G) to achieve high system coverage and capacity. To minimize signaling load of the core network when there is a macro base station(BS) failure in the control plane, a scheme of transferring the control of small cells under the coverage of the failure macro BS to the neighbor macro BSs is proposed. The average handover rates between small cells related to user mobilities, the extended coverage of the neighboring macro BSs under the constraint of transmitting power and the load balance index of the system are analyzed, based on which the formula of maximizing the handovers processed by macro BSs is constructed and further solved by the convex optimization methods. Simulation results indicate that the proposed scheme can effectively increase the total handovers processed by the macro BSs and thus reduce the signaling load of the core network.

Screening of Bacillus subtilis HAAS01 and Its Biocontrol Effect on Fusarium wilt in Sweet Potato

Fusarium wilt,a disease caused by Fusarium oxysporum f.sp batatas(Fob)is an important disease in sweet potato production.Using endophytic bacteria for biological control of sweet potato diseases is one of the important ways.A Bacillus subtilis with antagonistic effect on Fusarium wilt of sweet potato was isolated from soil by confrontation culture.According to the biological characteristics,16S rDNA sequence analysis,and physiological and biochemical analysis,the Bacillus subtilis HAAS01 was named.A pot experiment was conducted for the biological control experiment of strain HAAS01,and the endogenous hormone content,antioxidant enzyme activity,soluble protein content,and related gene expressions of sweet potato plants were detected.The results showed that the HAAS01 strain could promote the production of endogenous hormones and resist the infection of plant diseases together with defensive enzymes and upregulation of related gene expressions.In summary,Bacillus subtilis HAAS01 was effective in controlling Fusarium wilt of sweet potato and has potential for application and development.

Caputo型多时滞F-OFQVNNs的全局Mittag-Leffler投影同步

本文研究了具有离散和无限分布时滞Caputo型分数阶模糊四元数值神经网络(F-OFQVNNs)的全局Mittag-Leffler投影同步(G-MLPS)问题。首先,引入新的F-OFQVNNs模型;其次,设计新的自适应混合控制器,并采用Lyapunov直接法和不等式放缩技巧,得到了在新控制器下F-OFQVNNs达到G-MLPS的充分判据;最后,通过对实例进行数值模拟验证了所得结果的有效性。

U-model Enhanced Dynamic Control of a Heavy Oil Pyrolysis/Cracking Furnace

This paper proposes a case study in the control of a heavy oil pyrolysis/cracking furnace with a newly extended U-model based pole placement controller(U-PPC). The major work of the paper includes: 1) establishing a control oriented nonlinear dynamic model with Naphtha cracking and thermal dynamics; 2) analysing a U-model(i.e., control oriented prototype) representation of various popular process model sets; 3)designing the new U-PPC to enhance the control performance in pole placement and stabilisation; 4) taking computational bench tests to demonstrate the control system design and performance with a user-friendly step by step procedure.

Analysis and implementation of FURLS algorithm for active vibration control system with positive feedback

While positive feedback exists in an active vibration control system,it may cause instability of the whole system.To solve this problem,a feedforward adaptive controller is proposed based on the Filtered-U recursive least square(FURLS) algorithm.Algorithm development process is presented in this paper.Real time active vibration control experimental tests were done.The experiment results show that the active control algorithm proposed in this paper has good control performance for both narrow band disturbances and broad band disturbances.

Adaptive Neuro-fuzzy Controller Design for Non-affine Nonlinear Systems

An adaptive neuro-fuzzy control is investigated for a class of non-affine nonlinear systems.To do so,rigorous description and quantification of the approximation error of the neuro-fuzzy controller are firstly discussed.Applying this result and Lyapunov stability theory,a novel updating algorithm to adapt the weights,centers,and widths of the neuro-fuzzy controller is presented.Consequently,the proposed design method is able to guarantee the stability of the closed-loop system and the convergence of the tracking error.Simulation results illustrate the effectiveness of the proposed adaptive neuro-fuzzy control scheme.