Integrated power factor compensator without load current measurement

A simple strategy and low cost control for the switching mode rectifier to work simultaneously as a power factor corrector and an active power filter (APF) to reduce current harmonics drawn from the nonlinear load are analysed and presented in this paper. The principal component of the control circuit is an Intel 80196MC microcontroller that performs the dc bus voltage and line current control. The sliding mode control is used in the current loop to achieve fast line current dynamics. The source currents only are measured in the proposed control scheme instead of both the source and load currents needed in the conventional control approach. A simple proportional-integral control is adopted in the voltage loop to achieve slow dc bus dynamics. The proposed control strategy can achieve a high power factor and low current harmonics. No dedicated APF is needed in the proposed control strategy. To demonstrate the effectiveness of the integrated power factor compensator for elimination of reactive power and current harmonics, software simulation and hardware tests are performed.     

Entire-domain MoM analysis of an array of arbitrarily oriented circular loop antennas: a general formulation

This paper presents a general formulation for the entire-domain method of moments analysis of an N-element array of arbitrarily oriented coupled circular loop antennas. The orientations of the loops with respect to each other are defined through the use of Eulerian angles. The positions of the loops in space are defined by translation vectors from the center of a loop to another. By making use of coordinate transformations and vector algebra, a concise set of linear equations for solving the currents on the loops is obtained. The formulation is sufficiently general to be used for all the previously reported coupled loop orientations. It is also ideal for the study of skewed circular loops which may be oriented in innumerable ways and in turn demand a general formulation for their analysis. The use of the general formulation is illustrated by analyzing the coupling currents between collocated skewed loops. The formulation is also applied to study the effects on the transfer impedance between a pair of noncollocated skewed loops as one of the loops is rotated about various axes.     

Study of Mutual Coupling Between Circular Stacked-Patch Antennas on a Sphere

A rigorous mathematical analysis is given of spherical stacked-patch arrays with emphasis on the physical interpretation of mutual coupling mechanisms present in doubly- curved convex structures. The analysis method is based on electromagnetic field representation in terms of spherical harmonics where each harmonic has the same angular variation as the spectral source component. To obtain the spectral representation the vector-Legendre transformation is applied to currents and fields. A novel approach to the mutual coupling calculation within the method of moments analysis of spherical arrays is applied. By expressing the patch current in terms of two suitable potential-like auxiliary functions, it is possible to avoid the use of Euler's formulas for coordinate system rotation and the related lengthy integrations. Instead, the rotation of antenna elements and corresponding current distributions can be done in closed form with the help of Vilenkin's addition theorem for associated Legendre functions. It is shown that the new approach results in significant acceleration and improved accuracy of the analysis of spherical patch antenna arrays. The algorithm is successfully tested against a commercially available electromagnetic software and measurements performed on the developed laboratory model, confirming its accuracy for both input impedance and mutual coupling calculation and with only a small difference between the predicted and measured resonant frequencies, due to limitations in the experimental model. The influence of the structure parameters on mutual coupling level is extensively investigated, including all coupling mechanisms and leakage of energy due to curvature of the structure. It is shown that stacked-patch antennas can have reduced coupling level comparing to single patch antennas with possible deep nulls above the antenna resonant frequency.      

Optimal current programming in three-phase high-power-factorrectifier based on two boost converters

Current programming in a three-phase high-power-factor rectifier based on two boost converters is discussed in this paper. It is shown that the converter currents can be expressed in terms of two mutually related auxiliary functions. The auxiliary functions are related to the input current spectrum. Optimal auxiliary functions that eliminate harmonics of the input currents are derived. A method to generate reference signals for the optimal current programming is proposed. Experimental results confirming the proposed concepts are presented     

A single-phase controlled-current PWM rectifier

The analysis and test results are given for an experimental single-phase controlled-current PWM (pulse-width-modulated) rectifier that operates at unity power factor with near sinusoidal current waveform and that has power reversal capability. The twice-line-frequency AC power is identified as a source of voltage harmonics in the DC link. The harmonics enter into the voltage regulation feedback loop to distort the AC current waveform. These undesirable harmonics can be removed by a low-pass filter. It is noted that the overall design must address the possibility of instability due to the low-pass filter in the feedback path     

Electric lines of force of an electrically small dipole-loopantenna array

The electric lines of force of an electrically small dipole-loop antenna array have been determined analytically for both the near- and far-fields of the array. It has been found that the behavior of the families of electric contours are dependent upon a coupling parameter, which is the ratio of the loop and dipole sizes and currents. This parameter also controls the appearance (or not) and position of the points of equilibrium for the radiated field when analyzed in a real phase plane. The electric lines of force of the dipole-loop array exhibit increased directivity in the plane of the array when the coupling parameter is purely real, indicating that the respective dipole and loop currents must be in phase quadrature for this effect to occur     

Numerical and charge sheet models for thin-film SOI MOSFETs

Numerical charge sheet models applicable for all bias conditions are presented for the channel currents of long-channel SOI MOSFETs. From a comparison of the two models it is shown that the charge sheet analytic model accurately predicts the channel currents from weak to strong inversion regions. The results include analytic expressions for the drift and diffusion current components of individual channel currents, the front-gate and back-gate interaction parameter, and an analytic correlation between the surface potentials of the front and back channels when there is coupling between the two gates under nonthermal equilibrium conditions. The effect of SOI (silicon on insulator) film thickness on the drain current was investigated under different bias conditions for the back gate, and it was found that thin films are beneficial from the point of increased drain currents if the back channel is in depletion or inversion. It is also shown that, in addition to the charge coupling effects, dynamic interaction between the channels exists if the static current in one of the channels saturates     

Essential-coupling-path models for non-contact EMI in switching power converters using lumped circuit elements

This paper proposes a simple lumped circuit modeling approach for describing noncontact EMI coupling mechanisms in switching power converters. The resulting model assumes a minimum number of noise sources and contains essential coupling paths that allow easy physical interpretations. Essentially, all capacitive couplings are represented by an equivalent noise voltage source and six coupling impedances, whereas all inductive couplings are represented by an equivalent noise current source and three coupling impedances. The resulting coupled noise appears as currents flowing into the terminals of the line-impedance-stabilization-network (LISN). The equivalent voltage source can be conveniently approximated as the switching-node-to-zero voltage, which is typically a rectangular pulse of a few hundred volts. The equivalent current source can be modeled as the current flowing around a loop containing the equivalent voltage source and parasitics such as winding capacitance of the power transformer, the snubber capacitance and connection inductances. Also, the coupling impedances can be estimated by making simplifying assumptions about the geometry of the components and tracks, or by direct measurements. Simulations and experiments verify how inductive and capacitive couplings through each path may produce substantial EMI measured by the LISN. Being based on a lumped circuit approach, the proposed model is easy to apply in practice for understanding, diagnosing and approximating EMI behaviors.     

PWM整流器的PI^λ D^μ控制策略

针对常规控制适用场所的局限性,提出了一种基于分数阶控制的PWM整流方法,该方法有别于以往的双闭环控制策略,电流内环控制使用分数阶控制器取代传统控制器。通过MATLAB/Simulink仿真与实验验证了该控制策略的控制效果明显好于传统控制方法。此外,其不仅可以应用在控制精度要求高、控制参数多的非线性系统中,而且具有较好的跟随性、鲁棒性和稳定性,能够准确的跟踪指令电流,并且得到的网测电流谐波很少,近似于正弦波。     

A new robust capacitively coupled second harmonic quadrature LC oscillator

A study of some reported superharmonic LC quadrature voltage-controlled oscillator (LC-QVCO) is performed in which it is shown that robustness of the quadrature oscillation varies depending on the coupling configuration. Next, a new superharmonic LC-QVCO is proposed in which the common source node in either of two identical cross-connected LC-VCOs is coupled via a capacitor to the node common between the two varactors in the LC-tank of the other LC-VCO. As a result of connecting common mode nodes, the currents flowing through the two coupling capacitors are comprised of only the even harmonics. In the proposed coupling configuration there exists a closed loop through which the second harmonic signals circulate. A qualitative argument is presented to justify the robustness of the quadrature nature of the proposed QVCO by applying the Barkhausen phase criterion to the second harmonic signals in the loop. Since the coupling devices are only two capacitors, no extra noise sources and power consumption are added to the core VCOs. A Monte-Carlo simulation showed that the phase error of the proposed QVCO caused by device mismatches is no more than 1°. Also, generalizing this method to several numbers of VCOs in a loop, multiphase signals can be generated. The proposed circuits were designed using a 0.18-μm RF CMOS technology and simulation results are presented.     

Diakoptic theory for multielement antennas

A theory is presented for the analysis of multielement antennas which consist of interconnected, conductive structure elements of electrically small dimensions. The theory is based on the retarded electromagnetic potentials which permit a diakoptic approach to the problem. The antenna is broken up into its individual structure elements. Each element is assumed to be excited by currents which are impressed at its terminals, i.e., junctions with adjacent elements (current coupling) and by the electric fields of the currents and charges on all the other elements (fieid coupling). Both excitations are treated independently. Each impressed current produces a "dominant" current distribution, a characteristic of the element, which can be readily computed. Current coupling is formulated by "intrinsic" impedance matrices which relate the scaler potentials at the terminals of an element, caused by its dominant current distributions, to the impressed currents of the element. Field coupling produces "scatter" currents on all the elements and is formulated by a "fieid-coupling" matrix which relates the scalar potentials at the terminals, caused by field coupling, to the impressed currents at all the terminals. Intrinsic and "field-coupling" matrices are combined to form the "complete" impedance matrix of the diakopted antenna. Enforcing continuity of the currents and equality of the scalar potentials at all the interconnections between the elements yields a system of linear equations for the junction currents and the input impedance of the antenna. Current coupling dominates field coupling. Fieid coupling is primarily affected by the dominant current distributions of the elements, and in general the scatter currents have negligible effect on it. Although detailed numerical investigations will be presented in another paper, a simple example is included here to demonstrate that the diakoptic theory yields very good results even if greatly simplified assumptions are made.     

On two parallel loop antennas

The problem concerning the mutual coupling of two parallel thin-wire loop antennas in air is analyzed by formulating two coupled integral equations for the currents on the loops which are then solved by a typical Fourier series expansion method. Moment functions associated with the mutual coupling of the two loops are computed using a double Gaussian quadrature scheme. It is shown that the results as obtained from the integral equations agree with the conventional magnetic dipole approach provided that the loops are sufficiently small, and when the second loop is a perfect image of the first. For larger loops however the magnetic dipole approach cannot adequately take into account the proximity effect, since the current is assumed to be uniform. Input conductance of each loop is obtained for a wide range of separations as well as the staggering angles between the two loops. As special cases, results of a colinear and a coplanar are recovered.     

Current control strategy for power conditioners using sinusoidal signal integrators in synchronous reference frame

In this paper, a current control scheme, based on proportional-integral regulators using sinusoidal signal integrators (SSIs), is proposed for shunt type power conditioners. The aim is to simplify the implementation of SSI-based current harmonic compensation for industrial implementations where strict limitations on the harmonic distortion of the mains' currents are required. To compensate current harmonics, the SSIs are implemented to operate both on positive and negative sequence signals. One regulator, for the fundamental current component, is implemented in the stationary reference frame. The other regulators, for the current harmonics, are all implemented in a synchronous reference frame rotating at the fundamental frequency. This allows the simultaneous compensation of two current harmonics with just one regulator, yielding a significant reduction of the computational effort compared with other current control methods employing sinusoidal signal integrators implemented in stationary reference frame. A simple and robust voltage filter is also proposed by the authors to obtain a smooth and accurate position estimation of the voltage vector at the point of common coupling (PCC) under distorted mains' voltages. The whole control algorithm has been implemented on a 16-b, fixed-point digital signal processor (DSP) platform controlling a 20-kVA power conditioner prototype. The experimental results presented in this paper for inductive and capacitive loads show the validity of the proposed solutions.     

有互感和电源的电容耦合电路的量子涨落

通过正则变换和幺正变换的方法研究了有互感和电源存在的情况下的介观电容耦合电路的量子涨落。结果表明电荷和电流的量子涨落与电源无关。当电路元件确定时，如果L1／L2的值很大或很小，耦合对涨落的影响很大。互感从有到无的过程中，回路1中电流的涨落和回路中2中电荷的涨落有明显的变化。换句话说，互感的有无对涨落的大小起着举足轻重的作用。     

有源电力滤波器两种检测算法的比较研究

本文研究了有源电力滤波器的两种谐波电流检测算法,ip—iq法对负载电流中的谐波进行全部检测,基于用户侧谐波和无功补偿的检测法仅对用户自身造成的谐波进行检测。仿真结果表明,通过APF补偿后,前者电源电流为正弦波,后者电源电流和电源电压保持相同的畸变率,波形相似。     

有源电力滤波器两种检测算法的比较研究

文章研究了有源电力滤波器的两种谐波电流检测算法,ip-iq法对负载电流中的谐波进行全部检测,基于用户侧谐波和无功补偿的检测法仅对用户自身造成的谐波进行检测。仿真结果表明,通过APF补偿后,前者电源电流为正弦波,后者电源电流和电源电压保持相同的畸变率,波形相似。     

The backscattered field of a thin wire loop for H-polarization

For a thin wire loop illuminated by a plane electromagnetic wave, the backscattered field is determined when the incident magnetic vector is parallel to the plane of the loop. The complete second-order geometrical theory of diffraction (GTD) solution is obtained and found to be in excellent agreement with numerical data at angles close to normal incidence on the loop. At wide angles, however, the data exhibit a significant lobe that is not predicted by GTD. Analysis of the data shows that the lobe is due to currents circulating around the loop and the properties of these currents are deduced. Using a simple model for the current, the corresponding contribution to the backscattered field is determined. When this is added to the GTD solution, the resulting expression for the backscattered field is in good agreement with the numerical data for all angles of incidence and all loop diameters greater than a wavelength.     

Voltage Injection Method for Three-Phase Current Reconstruction in PWM Inverters Using a Single Sensor

This paper presents a voltage injection method for reconstructing phase currents from current signals measured on single current-shunt circuits with cost-effective and high-performance configurations in the pulsewidth modulation (PWM) inverters that are used for digital appliances. This method involves the injection of voltage signals at the carrier frequency for reconstructing the phase currents in PWM inverters using a single current sensor in the DC-link. It uses minimum signals to reduce the voltage and current harmonics caused by the injected signals. The vector of the injected voltage is at a minimum distance from the original reference to ensure the measurement time in the reconstruction of the phase currents. An injection sequence control method is also proposed to avoid an abrupt change in the injection signals. A PWM scheme for splitting phase voltages is proposed to reduce any audible noise, especially in low-speed operation. The proposed method reconstructs the phase currents with signals from a single current sensor and minimizes the amplitude of the injected signals to reduce the harmonics at audible noise frequencies in the injection signals. Experimental results showed the effectiveness of the proposed method.     

TRAPATT oscillations in a p-i-n avalanche diode

The characteristics of TRAPATT oscillations in a p-in diode are discussed and an approximate semi-analytical solution for the diode voltage waveform is derived when the diode current is a square wave. It is shown that a traveling avalanche zone is not necessary to generate a dense "trapped" plasma and that the boundary conditions prevent the trapped plasma from completely filling the depletion layer. Typical voltage waveforms and corresponding diode power, efficiency, and impedance at the fundamental and higher harmonics are presented. When the diode current is a square wave the diode does not necessarily exhibit a negative resistance at all higher harmonics. A computer program for TRAPATT oscillations in a p-i-n diode is described. Its running time is two or three orders of magnitude less than more exact time domain computer analyses. Typical results of diode power, dc to RF conversion efficiency, and required circuit impedances are presented for several different current waveforms which are composed of up to the seventh harmonic of a square wave and the first two harmonics of a half-wave sine wave. It is shown that high-efficiency oscillations are possible with diode currents composed of only the fundamental and one harmonic.     

基于dSPACE的三相PWM整流器最优控制

PWM整流器系统通常采用双闭环控制。其电流环为一多输入多输出强耦合的系统,普遍应用PI调节器结合前馈解耦的方法。本文针对电流环的特点,设计了LQR调节器,进一步提高了控制系统的性能。本文选取id,iq作为系统状态变量,建立PWM整流器电流环的系统状态方程,通过求解Riccati方程得到所求控制器。搭建了基于dSPACE...