基于滑动平均滤波和滞环控制的有源电力滤波器仿真研究

文章提出了一种基于瞬时无功理论的谐波电流检测新方法,该方法采用滑动窗式平均滤波来替代传统的低通滤波器,减小了谐波电流检测中的延时问题。同时采用滞环控制来提高电流的响应速度。利用Matlab/Simulink软件中对所提策略进行了仿真研究,仿真结果证明了所提策略的有效性,电流补偿效果较好,在负载突变情况下,仍具有较快的响应速度。     

单相半桥可逆整流电路的滞环电流控制

为了保证电压型PWM整流器有较好运行性能,时单相半桥可逆整流器的电流控制进行了研究.提出了一种电流跟踪性能好的滞环电流控制方法.滞环电流控制有较快的动态响应,不需要载波信号,误差可由滞环宽度调节,该方法可使电流控制精度很高,所以对单相半桥可逆整流器的滞环控制原理进行了详细的分析,并建立了基于MATLAB环境下的仿真模型,仿真结果验证了该设计方案的正确性.     

瞬时值反馈中点箝位三电平逆变器的研究

本文研究中点箝位三电平半桥逆变器单极性SPWM调制方式,分析了其六种工作模式,给出其控制信号的逻辑生成方式。为保证输出电压稳定和系统动态性能,该逆变器采用了电压电流瞬时值反馈技术。最后研制了一台1kVA/400Hz的三电平逆变器样机,实验表明采用电压电流瞬时值控制三电平逆变器具有优良的稳态和动态性能。     

有源滤波器的新型空间矢量滞环电流控制

本文提出了一种基于矢量原理的有源滤波器的滞环电流控制新方法.该方法以复平面为实施控制的矢量空间,根据电流误差矢量和参考电压矢量的空间分布对电压矢量进行最优化切换,使得电流误差控制在设定的滞环范围以内,改善滤波器性能.而且由于电压空间矢量的引入,使得其实现简单,能有效降低开关频率,改善电流跟踪性能.试验结果证明该方法的可行性.     

基于逆变器的配电网接地故障电流补偿算法研究

本文设计了一种用于不接地配电网中容性电流补偿的三相变流器控制策略.利用希尔伯特变换将接地故障时三相电流分解为正负零序分量,建立逆变器的平均状态空间模型,并给出电流控制算法.最后通过在Matlab中建立模型仿真对所设计控制算法进行了验证.     

单相电流跟踪型逆变器的仿真

本文对逆变器的分类,发展趋势及其在可再生能源并网发电中的作用做了简单介绍,然后用MATLAB对电流跟踪型逆变器做了仿真,得出在合适的RL值下,输出电流很好地跟踪了给定电流的变化。     

二极管箝位式多电平逆变器拓扑结构分析与控制策略研究

本文在分析五电平逆变器的基础上,归纳和分析了多电平逆变器的拓扑结构,对多电平逆变器的通用结构进行了总结.并对多电平逆变器的电压空间矢量进行了分析和研究,最詹对二极管箝位式多电平功率变换器的PWM控制技术进行了归纳和总结.     

三相电流型Z源逆变器数字逻辑脉宽调制

传统电流源(CS)逆变器用于中大型的工业应用中,与传统的电压型(VS)逆变器相比只适合电压下降的场合并且需要一个相当复杂的调制器.为了解决这种问题,本文提出了三相升降压型电流型逆变器的Z源概念,也就是Z源电流型逆变器.文章用不同的调制方法对电压型逆变器进行调制,进而推设计出合适的逻辑开关方程,控制电流源型Z源逆变器.可以用DSP和一个可编程逻辑器件实现.     

直流电源SPWM级联式多电平高压变频器的建模与仿真

阐述了直流电源SPWM级联式多电平逆变器工作原理,并应用于高压变频器的逆变部分,介绍了其建模和仿真过程,并与传统2H桥级联式变频器进行比较。仿真结果表明直流电源SPWM级联式多电平高压变频器具有输入功率因数高,输出波形稳定、谐波污染和损耗小、所用电力电子器件数量少的优点。     

HXD3型电力机车基于两电平逆变器的工作原理及控制方法

本文以HXD3型电力机车的逆变器为研究对象,对其工作原理和控制方法进行了分析,分析了SPWM控制的优越性为以后的机车检修工作提供了理论参考。     

A novel direct torque control method for brushless DC motors based on duty ratio control

Conventional direct torque control (DTC) suffers from large torque ripple and nonconstant switching frequency, which are caused by the hysteresis band amplitude and the motor speed. Many methods have been proposed to tackle these problems. However, these methods are usually complicated and parameter dependent. A novel DTC method for brushless DC motors based on duty ratio control is proposed to reduce torque ripple and maintain a constant switching frequency. During each switching period, an active voltage vector and a zero voltage vector are applied. A simple and effective method implemented to calculate the duty ratio relies only on the torque error, reducing the parameter dependence. The proposed method has the advantages of conventional DTC and effectively reduces torque ripple, which improves the performance of conventional DTC. Simulation and experimental results are given to confirm the method’s validity.     

A novel trust-based false data detection method for power systems under false data injection attacks

This paper proposes a novel trust-based false data detection method for power systems under false data injection attacks (FDIAs). In order to eliminate the interference posed by false data to the power system in the state estimation process, a trust model is first established to estimate the reliability of the system bus. Then an algorithm is proposed to update the bus trust value, when all the trust value of neighbor buses at one bus node are quite low, then this bus is diagnosed as a malicious node and the false data are detected. This method guarantees that the power systems can estimate the state accurately against FDIAs based on the trust of bus. The simulations on the benchmark IEEE 14-bus, IEEE 30-bus and IEEE 57-bus test systems are used to demonstrate the feasibility and effectiveness of proposed algorithm.     

A novel controller design and evaluation for networked control systems with time-variant delays

A new delayed state-variable model for networked control systems is presented, upon which a linear quadratic regulator (LQR) is designed. A method of delays-estimation online is also given. A fuzzy logic with LQR controller is addressed for the difficulty on implementation of LQR in networked control systems (NCSs) with time-variant delays. Simulation results prove that the novel controller can make the system stable and robustly preserve the performance in terms of time-variant delays.     

A decentralized control method for frequency restoration and accurate reactive power sharing in islanded microgrids

To achieve the frequency restoration (FR) and accurate reactive power sharing (RPS) in islanded microgrids (MGs), an improved P-f droop control is proposed. Firstly, the inverter impedance, whose value is set by the virtual impedance method, is used to minimize the impact of line resistance on powers coupling and RPS. Then, in order to restore the frequency of distributed generations (DGs) to the rated value, the reference is changed for compensating the frequency deviation (FD) caused by loads change. And the fast FR rate is achieved under a large constant k. Besides, in order to eliminate the inaccuracy of RPS caused by voltages difference (VD), the line voltage drop (LVD) is used to compensate the voltage droop characteristics. The use of voltage feedback ensures that the obtained voltage is desired after the LVD compensation. Finally, the simulation in RT-LAB indicates the effectiveness of proposed method in an islanded MG model.     

隐性成本含义、估测方法和控制方法研究述评

隐性成本作为成本内容的重要组成部分,在很大程度上影响着企业的决策和财务绩效,更关乎企业的长远发展,目前隐性成本已成为近些年来企业成本管理的重要内容。为了对目前隐性成本的研究有系统地认识和了解,文章在对国内外相关文献进行回顾的基础上,对隐性成本含义、隐性成本的估测方法和控制方法进行分析述评,总结了目前研究存在的不足,并对未来隐性成本进一步需要深入研究的问题进行展望。     

我国复杂产品系统企业市场控制力构建研究

旨在探析我国复杂产品系统企业市场控制力的主要构成要素,以通过构建、强化市场控制力化解其在全球价值链中“低端锁定”的问题,提升企业自主创新的动力和能力。采用多案例嵌入式调查统计分析法,基于探索性多案例研究和文献分析归纳提炼出15个影响复杂产品系统企业市场控制力的观测变量,形成本文实证研究的测度量表,并通过问卷调查法收集118个样本数据,运用探索性因子分析的方法对因素进行提取,得出3个主成分因子,即政治政策能力、差异竞争能力和客户价值链管理能力,构成复杂产品系统企业市场控制力的主因素。     

A flow and routing control policy for communication networks with multiple competitive users

This paper is concerned with deriving an optimal flow and routing control policy for two-node parallel link communication networks with multiple competing users. The model assumes that each user has a flow demand which needs to be optimally selected and routed on the network links. The flow and routing control policy for each user seeks to maximize the user's total throughput and minimize its expected delay. To derive such a policy, we consider a utility function for each user that combines these two objectives in an additive fashion with preference constants that can be adjusted to reflect the user's own preferences between maximizing throughput and minimizing delay. Additionally, we provide each user with the ability to make these preferences link-dependent to reflect the user's preferences for certain links over others in the network. A condition that depends on the link capacities and preference constants is derived to guarantee the existence and uniqueness of a non-symmetric flow and routing control policy solution which satisfies the Nash equilibrium of non-cooperative game theory. The Nash equilibrium is a desirable solution for such networks because it insures that no user can improve its utility by unilaterally deviating from its Nash control policy. We discuss in detail several interesting properties of this equilibrium and in particular, its relationship to the users’ preference constants. Two illustrative examples are also presented.     

基于磁致伸缩位移传感器的船闸闸门控制系统

连申线海安船闸位于南通海安县境内,海安船闸为双线船闸是江苏省干线航道网规划“两纵四横”中的第二纵,是沿海空间开发格局, “三极一带多节点”中的“一带”,纵贯长江三角洲东部,是连申线水上交通咽喉.该船闸控制为PLC控制系统,闸门运行采用磁致伸缩位移传感器开度控制.本文根据传感器的测量位移,推导了闸门开度方程.在控制程序的设计中,闸门的运行开度在监控屏幕上实时显示,并利用闸门开度反馈值作为闸门的无级变速与同步控制.这不仅有利于操作人员观察到船门运行状态,而且确保了闸门运行的平稳同步,还提高了闸门运行的安全性.     

A novel technique for optimal placement of piezoelectric actuators on smart structures

The problem of positioning of actuators and sensors on smart materials has been a point of interest in recent years. This is due to the fact that in many practical applications there are limitations in space, weight, etc. of the smart structures, which make the problem of positioning more complex. In addition, it is required that the actuators/sensors have the best possible performance. The development of smart structures technology in recent years has provided numerous opportunities for vibration control applications. The use of piezoelectric ceramics or polymers has shown great promise in the development of this technology. The employment of piezoelectric material as actuators in vibration control is beneficial because these actuators only excite the elastic modes of the structures without exciting the rigid-body modes. This is important since very often only elastic motions of the structures are needed to be controlled. The purpose of this paper is to introduce a novel approach developed for optimizing the location of piezoelectric actuators for vibration suppression of flexible structures. A flexible fin with bonded piezoelectric actuators is considered in this study. The frequency response function (FRF) of the system is then recorded and maximization of the FRF peaks is considered as the objective function of the optimization algorithm to find the optimal placement of the piezoelectric actuators on the smart fin. Three multi-layer perceptron neural networks are employed to perform surface fitting to the discrete data generated by the finite element method (FEM). Invasive weed optimization (IWO), a novel numerical stochastic optimization algorithm, is then employed to maximize the weighted summation of FRF peaks. Results indicate an accurate surface fitting for the FRF peak data and an optimal placement of the piezoelectric actuators for vibration suppression is achieved.     

一种稳定阈值的湖泊水体信息提取方法

针对提取水体信息时阈值设定模糊问题,提出一种具有稳定阈值的在反射率为0时水体与其他地物分离度最好的自动水体信息提取方法。利用不同时间段的艾比湖、博斯腾湖、鄱阳湖、阿拉湖的Landsat 8卫星影像为数据源,通过分析水体与不同地物的反射率及主分量特征,构建一种新型水体指数——温度植被水体指数（Temperature Vegetation Water Index, TVWI）,利用监督分类得到的水体面积为参考值,分别与传统水体提取方法进行对比验证。结果表明：①利用TVWI分别对2013年与2016年的艾比湖进行水体信息提取,总体精度分别为98.51%、97.33%,博斯腾湖为99.66%,鄱阳湖为98.06%,阿拉湖为99.72%,总体精度较高;②在TVWI指数中,水体与非水体区域区分度较高,在水体边界处的非水体区域出现极高的噪音值,而水体区域值大于0;③通过普适性分析得知,TVWI对湖泊适应性较好,对不同类型的湖泊水体提取精度均较高。因此,利用TVWI进行高精度无模糊阈值设定的水体信息提取是可行的。