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1.
为了改进AC/DC变换器的性能,本文提出一种基于汉密尔顿消散模型的AC/DC控制算法。介绍了一种基于汉密尔顿消散模型的AC/DC控制器设计方法,并对这种控制算法进行了分析。 相似文献
2.
This paper presents a robust high bandwidth discrete-time predictive current control scheme for voltage-source pulsewidth-modulated (VS-PWM) converters. First, to achieve high bandwidth current control characteristics, a digital predictive current controller with delay compensation is adopted. The compensation method utilizes a current observer with an adaptive internal model for system uncertainties. The predictive nature of both the current observer and the internal model forces the delays elements to be equivalently placed outside the closed loop system. Second, to ensure perfect tracking of the output current in the presence of uncertainties and providing means for attenuating low- and high- frequency system disturbances, the frequency modes of the disturbances to be eliminated should be included in the stable closed loop system. Toward this, an adaptive internal model for the estimated uncertainty dynamics is proposed. To cope with the high bandwidth property of the lump of uncertainties in VS-PWM converter applications, the disturbance slowly varying assumption is relaxed in the proposed controller. The relaxation is achieved by adopting a curbing sliding-mode-based feedback gain vector within the internal model observation system. Comparative evaluation tests were carried out on a grid-connected VS-PWM converter and a direct drive permanent magnet synchronous motor (DD-PMSM) drive system to demonstrate the validity and effectiveness of the proposed control scheme at different operating conditions. 相似文献
3.
Zhong Q.-C. Liang J. Weiss G. Feng C.M. Green T.C. 《Industrial Electronics, IEEE Transactions on》2006,53(5):1594-1602
Inverters used as the interface for a distributed generator in a three-phase four-wire system sometimes operate with a large neutral current because of unbalanced loads and single-phase (possibly nonlinear) loads. Voltage balance within the dc-link of the inverter is important for proper operation of the inverter, and the neutral current is a significant disturbance to this. It is preferable to use fast acting control rather than dissipative balancing or large-valued capacitors. This paper develops a linear model of an actively balanced split dc-link and applies Hinfin control design to provide high-bandwidth robust control. The approach is developed for a conventional two-level inverter, but it remains valid (without change) for a three-level neutral-point clamped inverter. The controller achieves very small deviations of the neutral point (better than 0.5 in 800 V) from the midpoint of the dc source despite the large neutral current (32 ARMS). The controller design is described and verified first in a PSCAD simulation and second in experimental testing of a 30-kW 415-V (line) inverter 相似文献
4.
《Microwave Theory and Techniques》1967,15(11):604-612
Approximate analyses published previously on tunnel-diode converters are basically phenomenological in nature by restricting the currents flowing through the tunnel diode or (and) the voltage across it to the signal, local oscillator, and intermediate frequencies only. Because of the nonlinear nature of the tunnel diode, many higher-order frequency components corresponding to harmonics and products, sums, and differences of the above mentioned frequencies are present. By including the effects of series resistance and series inductance and restricting the operating region within the parabolic portion of the tunnel-diode characteristics, the present analysis attempts to formulate the problem in a "rigorous" manner through the derivation of a second-order nonautonomous nonlinear differential equation with time-varying coefficients. The solution to a "first-order" approximation is obtained by incorporating a variational type treatment with an expansion type perturbation method. In an effort to verify the validity of the theoretical results obtained by the nonlinear analysis, an analog simulation is carried out since the control of required parameters in actual experiments is extremely difficult, especially in the microwave frequency region. The general agreement between the theoretical results and the analog simulation is promising and, therefore, should yield enough information to facilitate the control and adjustment of the various parameters in actual experiments especially in the microwave region. Specifically, we have verified by the analog simulation the theoretical prediction that the optimized conversion gain is obtained when the source resistance is about one third of the load resistance. In addition to minimizing the converter noise, the noise due to the first IF amplifier can also be minimized by selection of the correct converter load resistance by using Figs. 4 throngh 8. 相似文献
5.
Neacsu D.O. Wagner E. Borowy B.S. 《Industrial Electronics, IEEE Transactions on》2008,55(4):1628-1636
A solution for high current applications consists of paralleling power stages of lower power. Given the complexity of these systems, a comprehensive computer-based analysis is required before physical implementation. This paper presents a simulation benchmark for selection of the pulsewidth modulation (PWM) algorithms used to control interleaved three-and four-wire three-phase power inverters. The analysis considers the resulting phase current harmonics, dc link current harmonics, neutral point voltage, and inter converter circulation currents. Analytical aspects of different current control structures used within interleaved power electronics systems and effects of selecting various PWM algorithms are revealed for both the three-wire and the four-wire structure. Finally, analysis of the DSP implementation for different practical solutions is shown. 相似文献
6.
Christoph SANITER Rolf HANITSCH Alan WOOD 《电力电子》2005,3(2):63-67,72
在频域内使用频率耦合矩阵(FCMs),用建模方法描述了控制信号变化对PWM变换器谐波的影响。该方法是建立在对变换器开关函数严格的数学分析基础上的,并在频域内产生了一个完整的分析式。本文提供了这种建模方法得到的结果并用时域内的仿真数据进行了校验。 相似文献
7.
全并行(闪烁型)A/D转换器和逐次逼近型A/D转换器不能同时达到很高的转换速度和分辨率。本文介绍了几种能同时实现高速高分辨率A/D转换的电路,并对二步式A/D转换器、分区式A/D转换器以及流水线型A/D转换器的基本原理、结构和误差作了一些分析。 相似文献
8.
Bershad N.J. Bermudez J.C.M. Tourneret J.-Y. 《Signal Processing, IEEE Transactions on》2008,56(5):1853-1864
This paper studies the statistical behavior of an affine combination of the outputs of two least mean-square (LMS) adaptive filters that simultaneously adapt using the same white Gaussian inputs. The purpose of the combination is to obtain an LMS adaptive filter with fast convergence and small steady-state mean-square deviation (MSD). The linear combination studied is a generalization of the convex combination, in which the combination factor lambda(n) is restricted to the interval (0,1). The viewpoint is taken that each of the two filters produces dependent estimates of the unknown channel. Thus, there exists a sequence of optimal affine combining coefficients which minimizes the mean-square error (MSE). First, the optimal unrealizable affine combiner is studied and provides the best possible performance for this class. Then two new schemes are proposed for practical applications. The mean-square performances are analyzed and validated by Monte Carlo simulations. With proper design, the two practical schemes yield an overall MSD that is usually less than the MSDs of either filter. 相似文献
9.
《Microwave Theory and Techniques》1978,26(4):305-313
Frequency converters produce intermodulation noise in the desired signal band which may be a serious problem for communications systems using amplitude modulation. In this paper, we introduce the Volterra series with time-varying kernels to treat intermodulation in frequency converters with one two-terminal nonlinearity. The method gives exact results up to the order calculated (third order here) for any nonlinearity expressable as a power series, will treat frequency dependence in the nonlinearity as well as the terminations, and leads to a convenient algorithm for computer calculation. The mathematics provides a physical picture of intermodulation of a specific order as being produced by the modulation of lower order products through the nonlinearity. In fact, the solution for a given order of intermodulation currents or charges is the solution of a set of linear equations where the driving functions are intermodulation currents of lower order. A program has been written for the specific but important case of an abrupt junction varactor upconverter. Results for an upconverter that may be used for single-sideband operation in the common carrier microwave band show that the largest contribution to intermodulation comes from currents which are at the sum and difference frequencies of the input (IF) signal corresponding to currents above the input port in frequency and currents in the bias circuitry. This paper documents previously unpublished work (1972) done as part of the exploratory study of single-sideband modulation on long-haul microwave radio transmission. 相似文献
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An Improved Control Strategy of Limiting the DC-Link Voltage Fluctuation for a Doubly Fed Induction Wind Generator 总被引:2,自引:0,他引:2
Jun Yao Hui Li Yong Liao Zhe Chen 《Power Electronics, IEEE Transactions on》2008,23(3):1205-1213
The paper presents to develop a new control strategy of limiting the dc-link voltage fluctuation for a back-to-back pulsewidth modulation converter in a doubly fed induction generator (DFIG) for wind turbine systems. The reasons of dc-link voltage fluctuation are analyzed. An improved control strategy with the instantaneous rotor power feedback is proposed to limit the fluctuation range of the dc-link voltage. An experimental rig is set up to valid the proposed strategy, and the dynamic performances of the DFIG are compared with the traditional control method under a constant grid voltage. Furthermore, the capabilities of keeping the dc-link voltage stable are also compared in the ride-through control of DFIG during a three-phase grid fault, by using a developed 2 MW DFIG wind power system model. Both the experimental and simulation results have shown that the proposed control strategy is more effective, and the fluctuation of the dc-link voltage may be successfully limited in a small range under a constant grid voltage and a non-serious grid voltage dip. 相似文献
12.
Stephen B. Goldberg 《Alternatives to the High Cost of Litigation》2007,25(9):145-150
There's more that parties can do to help themselves in mediation. Veteran Evanston, Ill., neutral Stephen B. Goldberg describes how parties can work more effectively with the neutrals they hire to help them close cases and deals 相似文献
13.
Lung-Sheng Yang Tsorng-Juu Liang Jiann-Fuh Chen 《Power Electronics, IEEE Transactions on》2008,23(2):707-714
This paper proposes a novel three-phase ac-dc buck-boost converter. The proposed converter uses four active switches, which are driven by only one control signal. This converter is operated in discontinuous conduction mode (DCM) by using the pulsewidth modulation (PWM) technique, and the control scheme very easily and simply achieves purely sinusoidal input current, high power factor, low total harmonic distortion of the input current and step-up/down output voltage. Also, the proposed converter provides a constant average current to the output capacitor and load in each switching period. Thus, the ripple component of sixth times line frequency will not appear in the output voltage. Therefore, a smaller output capacitor can be used in the proposed converter. Moreover, the steady-state analysis of voltage gain and boundary operating condition are presented. Also, the selections of inductor, output capacitor and input filter are depicted. Finally, a prototype circuit with simple control logic is implemented to illustrate the theoretical analysis. 相似文献
14.
在当前的工业部门和用电设备中,电力电子技术得到了广泛的应用,导致电力系统中的非线性负载的比重增大,电网的谐波污染程度增加,电流和电压发生严重畸变,较大的影响了电能质量,同时也对电能计量带来了较大的负面影响。本文针对谐波对电能计量的影响进行研究,从谐波在电网中流动的理论和电能计量标准出发,分别探讨了谐波对感应式电能表和电子式电能表的影响,最后给出了提高测量精度的相关策略。 相似文献
15.
The signal flow graph (SFG) nonlinear modeling approach is well known for modeling DC-DC converters and it is a powerful analysis tool for higher order converter systems. Modeling of several specific fourth-order DC-DC converter circuits have been reported using conventional state-space averaging. Particular emphasis has been given, so far, only to arrive at any of the large, small-signal (SS) and steady-state models but not a generalized one. This paper gives the generalized SFG model of the fourth-order DC-DC converter topology that is useful for generating different types of fourth-order DC-DC converter circuits unified models. Further, it is shown that the deduction of large, SS and steady-state models from these unified SFGs is easy and straightforward. All possible fourth-order DC-DC converter circuits from its generalized topology have been identified and an analysis of a few converter circuits is given here for illustration of the proposed modeling method. Large-signal (LS) models are developed for different topology configurations and are programmed in SIMULINK simulator. LS responses against supply and load disturbances are obtained. Experimental observations are provided to validate the proposed modeling method. 相似文献
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为保证电能计量的精准,同时节约能源。电能计量的主要工具是电能表,电能表的计量关乎电能计量的准确度。因此,研究谐波对电能计量的影响是必要的。文中将通过对谐波的产生、危害以及其对感应电能表和电子电能表计量的影响进行分析,目的是寻求新的电能计量方法减少谐波的影响。 相似文献
18.
《Power Electronics, IEEE Transactions on》1987,2(4):343-353
The dynamics of multiple-output dc-dc converters are discussed. A multi-input-multi-output (MIMO) feedback system model incorporating effects of the output fluctuation is derived for the converter. Based on system theoretic tools, a set of stability conditions is obtained for the MIMO model; the result is used to formulate a stable margin. A practical five-output converter was selected for illustration of the proposed analytic tool. The effects of the input filter and coupled inductor on system stability margin are investigated. 相似文献
19.
大气波导对雷达异常探测影响的评估与试验分析 总被引:3,自引:0,他引:3
针对海洋大气波导环境对雷达性能影响的定量评估问题,本文建立的方法将对流层大气中电波传播的抛物型数值方程模式与雷达接收机理论结合起来,通过对雷达电磁波在实际波导环境下的传播损失分布规律进行阈化处理来分析雷达的最大探测距离特征.雷达探测评估的仿真数据显示,该方法能够较方便地评估雷达在大气波导环境下所具有的超视距探测等异常特征,该方法应用于某海域的试验分析中,评估的结果与实际雷达探测效果较为一致,验证了方法的实用性及大气波导环境下雷达的异常探测能力. 相似文献
20.
Chang Liu Panchenko Alexander Nikolaevich Bondarenko Igor Ilver Ibraimov 《Mobile Networks and Applications》2020,25(4):1582-1586
Mobile Networks and Applications - The open coaxial sensor (OCS) enables online non-destructive testing of a wide range of objects. To solve the electrodynamics problem in the OCS design, this... 相似文献