Improving the Specifications for Power-Line Filters

The most important requirement of a power-line filter is its insertion loss under load. This paper discusses methods of extending and improving the technique of measuring insertion loss as specified in MIL-STD-220A. It discusses present equipment limitations in MIL-STD-220A that restricts full-load tests to frequencies above 100 kHz and limits maximum current to 100 amperes. However, it is realized that MIL-STD-220A is the only available specification at present. Therefore, the paper discusses methods of extending the MIL-STD-220A technique for measuring the insertion loss of filters for frequencies as low as 14 kHz and under loads as high as 200 amperes. A new buffer network that allows such measurements is described. In addition, a method is discussed for improving voltage regulation and reducing distortion of the power-line waveshape caused by power filters. These are two parameters which have been totally ignored when specifying power filters and which have been found to cause considerable electrical problems after installation.     

Technique for measurement of powerline impedances in the frequencyrange from 500 kHz to 500 MHz

A method for measuring power line impedances using two current probes is examined. This method is characterized by good isolation of the measurement equipment from the power line voltage and by the capability of measuring power line impedances between any pair of power-plug terminals. The use of this two-current probe method with the model described is effective in measuring power line impedances from 0.5 MHz to 100 MHz. Using purely resistive loads for calibration, the error is less than 5% for frequencies below 100 MHz, and less than 20% for frequencies between 100 MHz and 500 MHz. The error in an impedance measurement increases with the magnitude of the load impedance     

EMI电源滤波器的插入损耗分析

在一般EMI滤波器的共模和差模等效电路的基础上,分析了源阻抗和负载阻抗对滤波器插入损耗的影响.提出了共模插入损耗和差模插入损耗的计算方法,推导了滤波器插入损耗与阻抗关系的表达式,并且对这一关系作了仿真分析,仿真结果验证了理论计算和分析的正确性.     

Small-Signal Impedance Measurement of Power-Electronics-Based AC Power Systems Using Line-to-Line Current Injection

Naval ships as well as aerospace power systems are incorporating a greater degree of power electronic switching sources and loads. Although these components provide exceptional performance, they are prone to instability due to their high efficiency and constant power characteristics that can exhibit negative impedance nature at certain frequencies. When designing these systems, integrators must consider the impedance versus frequency at an interface (which designates source and load). Stability criteria have been developed in terms of source and load impedances for both dc and ac systems, and it is often helpful to have techniques for impedance measurement. For dc systems, the measurement techniques have been well established. This paper introduces a new method of impedance measurement for three-phase ac systems. By injecting an unbalanced line-to-line current between two lines of the ac system, all impedance information in the traditional synchronous reference frame $d{-}q$ model can be determined. For medium-voltage systems, the proposed technique is simpler and less costly than having an injection circuit for each phase. Since the current injection is between only two phase lines, the proposed measurement device can be used for both ac and dc interfaces. Simulation and laboratory measurements demonstrate the effectiveness of this new technique.      

Control and performance of a self-commutated GTO converter operating in parallel with line-commutated thyristor converters

Recently, static var generators (SVGs) or static synchronous compensators based on self-commutated converters have been put into practical use for the purpose of compensation for reactive power, power swings damping, and/or voltage control in power systems. The SVGs have also been applied to reduce voltage fluctuations appearing at high-speed train substations. When parallel resonance occurs between passive filters installed at a point of common coupling (PCC) and the power-system impedance existing upstream of the PCC, voltage/current harmonics are significantly amplified in the power system. This paper describes the control and performance for a self-commutated gate-turn-off (GTO) converter operating in parallel with conventional line-commutated thyristor converters. This hybrid power conversion system rated at more than dozens of MVA has an inductive load at the dc side. A bank of passive filters is connected not only for harmonic compensation of the line-commutated converters, but also as a constant leading reactive-power source. The GTO converter can control either leading or lagging reactive power so as to achieve unity power factor operation. In addition, it has the capability of damping out parallel resonance between the passive filters and the power-system impedance. This paper confirms the viability and effectiveness of the hybrid system by means of theory and computer simulation.     

Predicting Insertion Loss of Common-Core Powerline Filters

Knowledge of the propagation mode and the source impedance is necessary in order to predict the insertion loss of common-core powerline filters. If these quantities are standardized, the transition-band insertion loss corresponding to two test modes can be accurately calculated by use of only a programmable hand calculator, such as the Hewlett-Packard HP65 or Texas Instruments SR56. Such predictions of differential and common-mode insertion loss are of value in designing electronic equipment for conformance to world-wide specifications applying to powerline interference emission and filter leakage current.     

A Technique for Determination of Filter Insertion Loss as a Function of Arbitrary Generator and Load Impedances

Insertion loss is derived in terms of generator impedance, load impedance, and filter open-circuit and short-circuit impedances. This expression contains a difference term which places great weight on the accuracy with which filter impedances are measured. It is shown that the use of this difference term can be avoided by introducing the filter insertion loss in a circuit with known generator and load impedances. The resulting exact expression contains terms which are easily measurable with sufficient accuracy to provide reliable insertionloss values for the filter for any combination of generator and load impedances. Also shown is a simplified approximate expression for insertion loss which is applicable in a filter attenuation band. A discussion of experimental verification of the expressions is followed by curves showing application of the approximate insertion-loss expression to a particular filter.     

A low voltage CMOS RF front-end for IEEE 802.11b WLAN transceiver

A low voltage CMOS RF front-end for IEEE 802.11b WLAN transceiver is presented. The problems to implement the low voltage design and the on-chip input/output impedance matching are considered, and some improved circuits are presented to overcome the problems. Especially, a single-end input, differential output double balanced mixer with an on-chip bias loop is analyzed in detail to show its advantages over other mixers. The transceiver RF front-end has been implemented in 0.18 um CMOS process, the measured results show that the Rx front-end achieves 5.23 dB noise figure, 12.7 dB power gain (50 ohm load), −18 dBm input 1 dB compression point (ICP) and −7 dBm IIP3, and the Tx front-end could output +2.1 dBm power into 50 ohm load with 23.8 dB power gain. The transceiver RF front-end draws 13.6 mA current from a supply voltage of 1.8 V in receive mode and 27.6 mA current in transmit mode. The transceiver RF front-end could satisfy the performance requirements of IEEE802.11b WLAN standard. Supported by the National Natural Science Foundation of China, No. 90407006 and No. 60475018.     

Stability margin monitoring for DC distributed power systems via perturbation approaches

In multi-module power electronics systems, especially DC distributed power systems, the small-signal stability issues are often dealt with by employing Middlebrook's impedance criterion. However, for on-line system stability margin monitoring, directly measuring impedance of the source and load subsystems then making quantitative comparisons is too complicated and difficult. This paper proposes practical and simple methods, which involve applying current or voltage perturbation to the dc side of distributed power systems then only measuring the amplitude of two currents or voltages in order to monitor the stability margin. For both methods (current perturbation and voltage perturbation), an implementation approach that does not employ external voltage or current perturbation source is also presented. All these methods and approaches are equivalent to the impedance measuring and comparing method based on the impedance criterion with different forbidden regions. A comparative evaluation of each method and its corresponding implementation approach is provided.     

Control of series active power filters compensating for source voltage unbalance and current harmonics

In this paper, a novel control scheme compensating for source voltage unbalance and current harmonics in series-type active power filter systems combined with shunt passive filters is proposed, which focuses on reducing the delay time effect required to generate the reference voltage. Using digital all-pass filters, the positive voltage sequence component out of the unbalanced source voltage is derived. The all-pass filter can give a desired phase shift and no magnitude reduction, unlike conventional low-or high-pass filters. Based on this positive-sequence component, the source phase angle and the reference voltage for compensation are derived. This method is easier to implement and to tune controller gains. In order to reduce the delay time effect in the voltage control loop, the reference voltage is predicted a sampling period ahead. The validity of the proposed control scheme has been verified by experimental results.     

基于负载的有源EMI滤波器插损分析

相同的有源EMI滤波器在不同的源阻抗和负载阻抗条件下,滤波特性有很大差异。文中以电流检测电流补偿型有源EMI滤波器为例,分析了在负载分别为纯阻性、感性和容性条件下的滤波特性,并给出了有源EMI滤波器的适应条件。     

高精度电流源电路的设计

提出了一种高精度的电流源电路,通过V/I变换,将由带隙基准电压电路产生的与温度和电源电压无关的带隙基准电压转换成与温度和电压无关的高精度基准电流,并通过高精度电流镜结构产生所需的镜像电流,有效地抑制了由于温度、电源电压、负载阻抗的变化及干扰对电流源的影响.用HSPICE对改进前后的电路进行对比测试,结果表明,改进后电流镜的镜像误差约减小90%,电流源的精度显著提高.     

电流模集成电抗元件与频率变换电路的设计

为了拓宽电流模单元电路结构在低压低功耗射频集成电路中的应用,研究把第二代电流传输器用作电抗器件和频率变换电路。以第二代电流传输器为核心,辅助予外围电路,构造从输入到输出端口不同性质传输阻抗的有源电容倍增器和有源电感,并且基于第二代电流传输器组合结构差异的分析,设计了集成频率变换电路。从理论上,推出有源电容倍增器和有源电感结构的合理性。仿真集成频率变换电路,结果袁明对40MHz以下正弦波倍频功能正确,且以100kHz正弦波为调制信号和以10MHz的正弦波为载波获得了双边带调幅信号。这为射频集成电路设计提供了新的思路。     

A series active power filter based on a sinusoidalcurrent-controlled voltage-source inverter

A series active power filter working as a sinusoidal current source, in-phase with the mains voltage, has been developed and tested. The amplitude of the fundamental current in the series filter is controlled through the error signal generated between the load voltage and a pre-established reference. The control allows an effective correction of power factor, harmonic distortion and load voltage regulation. Compared with previous methods of control developed for series active filters, this method is simpler to implement because it is only required to generate a sinusoidal current, in-phase with the mains voltage, the amplitude of which is controlled through the error in the load voltage. The proposed system has been studied analytically and tested using computer simulations and experiments. In the experiments, it has been verified that the filter keeps the line current almost sinusoidal and in-phase with the line voltage supply. It also responds very quickly under sudden changes in load conditions, reaching its steady-state in about two cycles of the fundamental     

A Low-Frequency Current Probe System for Making Conducted Noise Power Measurements

The two current probe technique of measuring conducted radio-frequency interference is a radical departure from conventional measurement techniques. The technique evolved from a dissatisfaction with present techniques, due to the lack of sufficient information obtained from measurements concerning the source of the interference. Normally, the wires concerned when testing for conducted interference are 60-Hz power lines of the two conductor type. If a pair of conductors comprising a power cord is considered as a transmission line, the factors which determine its performance at radio frequencies are primarily the wire length and loading. In practice, power lines do not have readily described configurations, which makes a transmission-line analysis extremely difficult. As a result, no attempt to analyze the situation is made at all. Usually, a line impedance stabilization network (LISN) is inserted into the line and the noise voltage developed is measured across a 50-ohm internal resistor which is effectively placed across the line. Thus, the only information obtained is a noise voltage which existed across a resistor at the time of measurement, but is nonexistent after the test. The noise voltage existing across the line after the LISN has been removed remains unknown. As a matter of fact, it cannot even be calculated, since the line characteristics are unknown. Thus insufficient information is the reason for pursuing the current probe techniques. The two current probe technique of measuring conducted interference overcomes the limitations of the LISN technique by supplying more information about the line.     

Novel three-controller average current mode control of DC-DC PWMconverters with improved robustness and dynamic response

This paper presents a novel average current mode control (ACC) strategy for the control of pulse width modulated (PWM) DC-DC converters, which represents a drastic improvement over conventional ACC. This new method consists of the addition of an auxiliary controller into the control loop, besides the current and voltage regulators. The model-based auxiliary controller can increase the closed loop small-signal bandwidth of Buck derived converters, preserving loop gain crossover frequency and stability margins over significant changes of the power stage passive elements values, the load and the line voltage. Moreover, this control scheme shows much better disturbance rejection properties, i.e., closed loop impedance and audiosusceptibility, than conventional ACC. From a control theory point of view, robust performance is achieved preserving stability. A Buck prototype has been experimentally tested with different LC output filters, line and load conditions, including discontinuous conduction mode. Measurements of the small signal frequency response of the converter have been carried out, showing the improvement achieved by the proposed control scheme. The empirical large signal response of the converter under load steps is also shown in order to validate the concept     

基于本地功率基准的异常用电监测方法

目前电力系统中有不平衡负荷存在,不平衡负荷会引起电能计量的误差。对于计量误差的处理目前普遍在主站结算并归于线损。文中为判断用户是否使用不平衡负荷及其所引起的误差值,利用电力系统中电压电流关系推算出不能直接测量的电压电流值,并应用三相四线制功率计算方法建立本地功率基准,与实际功率加以比较,判断用户是否存在不平衡负荷,并将计量误差量化。这对于防窃电、安全用电有重要作用,同时对于电力系统的节能降损也起着关键作用。通过Matlab仿真分别对正常用电和存在不平衡负荷用电进行了仿真,验证结果表明,不平衡负荷用电时,存在计量误差,且电力部门少计量了使用不平衡负荷用户所消耗的电能。     

高压逆变电源负载阻抗特性分析

高压逆变电源系统在工作时,随着应用环境的变化,负载阻抗会发生变化,负载阻抗变化进而影响电源正常稳定工作。为理解负载阻抗的变化特性及规律,设计合适的逆变电源负载,本文根据实际应用的高频高压逆变电源电路,对负载阻抗的变化进行了理论分析和仿真,最后给出输出电压电流对负载阻抗的变化仿真曲线。根据曲线我们可以为系统电路参数的设计和选择提供依据。     

Nonlinear characterization of GaN HEMT

DC I-V output, small signal and an extensive large signal characterization (load-pull measurements) of a GaN HEMT on a SiC substrate with different gate widths of 100μm and 1 mm have been carried out. From the small signal data, it has been found that the cutoff frequencies increase with gate width varying from 100μm to 1 mm, owing to the reduced contribution of the parasitic effect. The devices investigated with different gate widths are enough to work in the C band and X band. The large signal measurements include the load-pull measurements and power sweep measurements at the C band (5.5 GHz) and X band (8 GHz). When biasing the gate voltage in class AB and selecting the source impedance, the optimum load impedances seen from the device for output power and PAE were localized in the load-pull map. The results of a power sweep at an 8 GHz biased various drain voltage demonstrate that a GaN HEMT on a SiC substrate has good thermal conductivity and a high breakdown voltage, and the CW power density of 10.16 W/mm was obtained. From the results of the power sweep measurement at 5.5 GHz with different gate widths, the actual scaling rules and heat effect on the large periphery device were analyzed, although the effects are not serious.The measurement results and analyses prove that a GaN HEMT on a SiC substrate is an ideal candidate for high-power amplifier design.     

High-Efficiency Broadband Parallel-Circuit Class E RF Power Amplifier With Reactance-Compensation Technique

Class E amplifier offers high efficiency approaching 100% for an ideal case. This paper introduces a first practical implementation of a novel broadband class E power amplifier design combining a parallel-circuit load network with a reactance compensation technique. The novel broadband parallel-circuit class E load network using reactance compensation technique has been discussed based on theory and its experimental verification. A proper guidelines method of designing a high-efficiency broadband class E power amplifier with an LDMOS transistor until the final prototype measurement and optimization will be discussed. In the measurement level, the drain efficiency of 74% at an operating power of 8 W and power flatness of 0.7 dB are achieved across a bandwidth of 136-174 MHz. The efficiency result is the highest result for VHF broadband frequency to date with a low supply voltage of 7.2 V. Simulations of the efficiency, output power, drain voltage waveform, and load angle (impedance) were verified by measurements and good agreements were obtained.