一种新颖的锁相环的研究

本文提出了一种新颖的适用于三相电力系统在频率波动条件下的锁相环系统。介绍了锁相环的三个环节鉴相器、环路滤波器和压控振荡器的基本构成以及系统的工作原理,并在离散时域内分析了锁相环系统的动态特性,通过闭环系统的根轨迹给出了系统的稳定条件,仿真实验结果表明该锁相环可以很好地跟踪系统频率的变化从而实现相位的锁定。     

基于GA-SVR模型的肌力康复电刺激系统的设计研究

为了实现康复电刺激系统治疗参数的个性化定制及实时调整,提出了一种基于调制中频电刺激的下肢肌力康复闭环电刺激系统。设计低频调制中频刺激电路,基于遗传算法建立了电刺激参数与膝关节角度之间的支持向量机回归预测模型,并搭建基于模糊内模控制PID的闭环反馈系统,以达到更精确稳定的参数设置效果。通过膝关节运动实验表明,被试者在无痛感的前提下更接近预期的关节运动轨迹,30组膝关节运动角度与预期值最大均方根误差为10.21°,最小均方根误差为5.48°。相比传统低频电刺激,肌电平均振幅具有20μV以上提升。本文提出的电刺激系统参数可实现因人而异,且可根据闭环反馈结果进行实时调整,该系统能有效活化肌肉、提升肌力,在肌力康复步态训练中有较好的应用前景。     

LCL滤波并网逆变器的进网电流相位矫正技术

文中分析了LCL滤波并网逆变器系统的稳定性。该并网逆变器采用逆变器侧电感电流作为反馈量,并采用电网电压前馈控制策略,由劳斯判据得到该系统恒稳定的结论。由闭环系统的传递函数确定了电压前馈系数的大小,并根据闭环系统的根轨迹设计了电流环的控制参数。分析了该闭环系统并网功率因数小于1的原因,为克服这一缺点,提出了进网电流相位矫正技术。该技术根据进网电流与电网电压之间的相位差调节电流环基准值的频率,最终使进网电流与电网电压同相位,并网功率因数等于1。进网电流相位矫正技术不会影响原有系统的稳定性。仿真结果验证了该策略的有效性。     

Geometric links among classical controls tools

This paper develops a geometric perspective that ties together a number of graphically based techniques from classical control theory. In particular, in the frequency domain, a connection between the Nyquist diagram and the Bode plots is unfolded via a sequence of three-dimensional representations. A parallel development in the “gain-domain” begins with the Evans root locus plot and leads to a set of gain plots that portray eigenvalue behavior as an explicit function of forward gain. The gain plots extend the standard root locus plot by depicting explicitly the influence of gain (or any system parameter) on the closed-loop system eigenvalues. This is similar to the way the Bode plots embellish the information of the Nyquist diagram by exposing frequency explicitly. The gain plots enable direct determination of gain values for which the closed-loop system is stable or unstable. By exposing the correspondence of gain values to specific eigenvalues, the plots serve as a pole-placement tool for identifying closed-loop designs meeting performance specifications. Furthermore, the gain plots reveal by inspection information about the closed-loop root sensitivity. The authors have found the gain plots as well as the underlying geometric development in both the frequency and gain domains invaluable in undergraduate and graduate controls education     

带恒功率负载的Boost变换器模糊自适应反步滑模控制

恒功率负载的负阻抗特性易导致DC/DC变换器系统输出电压不稳定。该文针对带恒功率负载的Boost变换器,提出一种模糊自适应反步滑模控制策略。首先应用精确反馈线性化将模型转化为布鲁诺夫斯基标准形式。然后在保证大信号稳定的前提下,将模糊自适应控制方法加入到反步滑模控制器的设计中,根据模糊自适应控制系统实时更新系统增益,利用李雅普诺夫理论证明整个闭环系统的稳定性。最后,仿真和实验结果表明,与传统的双闭环PI控制方法相比,该控制策略具有更好的动态调节性能和更强的鲁棒性。     

Transfer Functions of the Slip-Controlled Induction Machine

The use of a feedback loop to regulate the slip frequency of an inverter-driven induction machine is viewed as replacing the normal independent control of stator frequency with independent control of slip frequency. For steady-state conditions the two modes of operation are shown to produce characteristics analogous to shunt and series dc machines. A method employing closed-form transfer functions, a reduced set of nondimensional parameters, and a general root locus diagram is used to present the dynamic characteristics of controlled slip frequency operation and to compare performance with conventional operation. The parameter range in the general diagram is sufficient to incorporate nearly all standard induction machines over a wide size and frequency range. The results demonstrate that the ratio K? of the rotor transient time constant to the static electromechanical time constant is a critical parameter in the comparison of the two modes. Since this parameter tends to increase with machine size, the relative advantages of slip frequency control are shown to be machine-size dependent. Inclusion of a speed-control loop regulating machine voltage is also Considered and shown to be described by the same general root loci. The performance of this closed-loop system is also shown to be very dependent on K? and hence on machine size.     

A unified approach to teaching feedback in electronic circuitscourses

A generalized negative feedback model is proposed as a vehicle for teaching feedback amplifiers in engineering schools. The model applies to both discrete and operational amplifier configurations and does not dictate the use of specific gain definitions (such as transconductance) for analyzing a given negative feedback amplifier. The main features of the suggested methodology and examples for quick evaluation of closed-loop gain, frequency response, and input and output impedances of negative feedback amplifiers are presented. The proposed method has been successfully tested in the class room over the past two years     

基于暂态阻尼增强的改进VSG控制策略

针对虚拟同步发电机(virtual synchronous generator, VSG)并网运行时在有功指令和电网频率扰动下存在输出有功暂态振荡问题,提出了一种基于暂态阻尼增强的改进VSG控制策略。首先,基于状态反馈理论,分析了所提控制方法的物理意义,即该策略是通过在常规VSG有功控制环中加入角频率和电磁功率的高频分量来增强系统暂态阻尼。然后,基于所提的控制方法,建立了系统的有功控制环闭环小信号模型,并通过对系统特征根的根轨迹进行分析揭示了所提控制方法对VSG有功功率振荡抑制的影响。并给出了各状态反馈参数的设计准则,指导了反馈系数的设计。所提控制策略能有效抑制有功指令突变和电网频率突变时VSG输出有功功率振荡,并且不会影响系统的稳态特性。最后,通过仿真和实验对比分析,表明所提控制方法具有更好的有功功率振荡抑制效果,并且能消除稳态偏差,且适用于不同电网强度。     

针对并网型飞轮储能系统的双电流闭环比例谐振控制

文章提出一种适用于飞轮储能系统并网的双电流闭环控制方法。在电网侧及飞轮侧控制系统中同时引入比例谐振控制器,避免了比例积分（proportional integral,PI）控制器跟踪正弦电流存在稳态误差的缺点,提高了系统的稳定性及电网电能质量。同时,采用电容电流内环反馈控制抑制LCL滤波器的谐振尖峰,提高进网功率因数。在充电阶段,电网侧变换器采用电压外环控制方式,飞轮侧变换器采用转速外环控制方式;在待机及并网运行阶段,电网侧变换器采用电网侧电流外环电容电流内环的控制策略,飞轮侧变换器采用直流母线电压外环电流内环的控制策略,以稳定直流母线电压。采用广义根轨迹法对电网侧控制器参数进行设计。搭建了飞轮储能系统并网控制模型,仿真结果验证了文章控制策略的有效性。     

Decentralized PI/PD position control for active magnetic bearings

This paper discusses a closed-loop decentralized control for active magnetic bearings. A cascade connection of PI and PD position controllers is proposed. The control design is based on a simplified linearized model for one axis using a root locus. An excellent agreement is noticeable between simulation and experimental results. It has been shown, that the presented PI/PD control guarantees satisfactory high damping and stiffness of the overall system.     

Comparison between closed-loop and partial open-loop feedbackcontrol policies in long term hydrothermal scheduling

Stochastic dynamic programming has been. extensively used in the optimization of long term hydrothermal scheduling problems due to its ability to cope with the nonlinear and stochastic characteristics of such problems, and the fact that it provides a closed-loop feedback control policy. Its computational requirements, however, tend to be heavy even for systems with a small number of hydroplants, requiring some sort of modeling manipulation in order to be able to handle real systems. An alternative to closed-loop optimization is an approach that combines a deterministic optimization model with an inflow forecasting model in a partial open-loop feedback control framework. At each stage in this control policy, a forecast of the inflows during the period of planning is made, and an operational decision for the following stage is obtained by a deterministic optimization model. The present paper compares such closed-loop and partial open-loop feedback control policies in long term hydrothermal scheduling, using a single hydroplant system as a case study to focus the comparison on the feedback control performance. The comparison is made by simulation using data from historical and synthetical inflow sequences in the consideration of three different Brazilian hydroplants located in different river basins. Results have demonstrated that the performance of the partial open-loop feedback control policy is similar to that of the closed-loop control policy, and is even superior in dry streamflow periods     

A method for plotting the complementary root locus using the root-locus (positive gain) rules

The root-locus method is a well-known and commonly used tool in control system analysis and design. It is an important topic in introductory undergraduate engineering control disciplines. Although complementary root locus (plant with negative gain) is not as common as root locus (plant with positive gain) and in many introductory textbooks for control systems is not presented, it has been shown a valuable tool in control system design. This paper shows that complementary root locus can be plotted using only the well-known construction rules to plot root locus. It can offer for the students a better comprehension on this subject. These results present a procedure to avoid problems that appear in root-locus plots for plants with the same number of poles and zeros.     

含恒功率负荷直流微电网的状态反馈电压振荡控制技术

扰动发生后新能源发电和恒功率负荷侧换流器在现有功率控制模式下所表现出的负阻抗特性,会大幅增加直流电压振荡失稳的风险.为此,首先针对直流电压振荡失稳的问题,推导含恒功率负荷两端直流微电网的小扰动线性化状态方程.其次,结合各状态变量的参与因子,选取振荡电流、电压作为可调节控制参数,将其分别引入储能换流器与恒功率负荷换流器的占空比反馈环节中,提出基于状态反馈的多端直流电压振荡控制方法.然后,利用根轨迹、Bode图分析附加状态反馈电压振荡控制技术后的直流微电网稳定裕度的变化规律,为控制参数设计提供依据.最后,搭建时域仿真系统,验证了所提出的控制方法可有效抑制直流微电网的电压振荡,显著提高系统的动态稳定性.     

Complementary root locus revisited

In this paper, a new finding related to the well-known root locus method that is covered in the introductory control systems books is presented, It is shown that some of the complementary root locus rules and properties are not valid for systems with loop transfer functions that are not strictly proper. New definitions for root locus branches have been presented which divide them into branches passing through infinity and branches ending at or starting from infinity. New formulations for calculating the number of branches passing through the infinity point of intersection of the asymptotes on the real axis, and angles of these asymptotes with the real axis have been introduced. It has been shown this type of system with the order of n will have at least one and at most n branches which will pass through infinity. The realization and stability of these systems have been investigated, and their gain plots have been presented. The new finding can be used by educators to complement their lecture materials of the root locus method. By using problems similar to examples presented in the paper, analytical understanding of the students in a classical control systems course can be tested     

MIMO连续系统中可交换矩阵的充要条件

首先对MIMO或SISO连续闭合线性系统在状态矩阵可交换下,给出了反馈阵存在的充要条件,即SISO闭合系统归结到矩阵A的特征值与特征根的情形,MIMO闭环系统归结到矩阵A的特征子间的不变性,而以SISO及MIMO开环系统的情形时,以Kronecker积作为工具,将状态矩阵集可交换时反馈阵的存在性等价于Lyapunov方程解的存在性问题,同时给出了Lyapunov方程的具体形式,最后,通过几个具体数字例子来说明所得的结论。     

蔡氏电路混沌系统的自适应反馈控制

针对一类简单的三维自治系统一蔡氏电路(Chau’s circuit)混沌系统，提出了一种反馈控制方法和一种自适应反馈控制方法。对于两种控制方法都利用Lyapunov原理证明了闭环系统的渐进稳定性，将提出的控制方法用于蔡氏电路混沌系统稳定于其不动点的控制。仿真结果表明，控制方法是有效的，自适应技术提高了系统的控制性能。     

Analysis of a Tuned Coupled Circuit by Root-Locus Techniques

Application of root-locus techniques to the familiar transformer-coupled tuned circuit accurately locates the poles of the transfer function as a function of the coefficient of coupling, thus enabling the frequency response to be found easily by graphical zero-pole techniques. The locus is seen to be a circle centered on the negative real axis, and this explains the fact that the lower frequency peak in the undercoupled case is greater than the higher frequency peak, a phenomenon which is not explained by the usual algebraic approximations. This ties theory and experimental results together nicely and gives an engineering student motivation and practice in the use of root-locus techniques in circuit analysis.     

微分反馈控制在永磁伺服系统中的应用研究

PI调节器用于伺服系统闭环控制时,为保证伺服系统有快速响应,超调是不可避免的.本文研究微分控制(微分调节,微分反馈)对抑制系统响应超调的作用.通过求解微分方程的实时解,分析微分控制对闭环系统阻尼比及闭环零、极点的影响.分析表明,对实际的永磁同步伺服系统引入微分反馈控制,可使系统既有较快的响应速度,又明显地抑制伺服系统响应超调,从而使系统具有优异的响应性能.仿真和实验均证实了微分反馈对伺服系统控制的有效性.     

基于频域的β-GPC稳定性分析与设计及在中频电源控制中的应用

推导了β-GPC(Generalized Predictive Control,即广义预测控制)的闭环反馈结构和闭环传递函数的递推公式.采用频域响应法分析β-GPC控制下闭环系统的频率特性.通过计算系统开环和闭环极点,分析闭环系统频率特性,设计β-GPC的参数,应用于中频电源控制系统中取得了满意的稳定性和暂态特性.     

A simple and fast algorithm for determining asymptotic stability of linear autonomous systems

The method introduced here determines explicitly whether a given system has only eigenvalues with negative real parts, without determining these eigenvalues, but rather by determining the eigenvalues of a related symmetric matrix which are always real and hence easy to calculate. The new method is similarly applied to linear autonomous discrete systems where all the eigenvalues of the system matrix are required to be positioned within the unit circle in the z-plane.