An improved control algorithm of shunt active filter for voltageregulation, harmonic elimination, power-factor correction, and balancingof nonlinear loads

This paper deals with an implementation of a new control algorithm for a three-phase shunt active filter to regulate load terminal voltage, eliminate harmonics, correct supply power-factor, and balance the nonlinear unbalanced loads. A three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC-VSI) with a DC bus capacitor is used as an active filter (AF). The control algorithm of the AF uses two closed loop PI controllers. The DC bus voltage of the AF and three-phase supply voltages are used as feedback signals in the PI controllers. The control algorithm of the AF provides three-phase reference supply currents. A carrier wave pulse width modulation (PWM) current controller is employed over the reference and sensed supply currents to generate gating pulses of IGBTs of the AF. Test results are presented and discussed to demonstrate the voltage regulation, harmonic elimination, power-factor correction and load balancing capabilities of the AF system     

Digital control of induction motor current with deadbeat responseusing predictive state observer

For a high-power induction motor drive, the switching frequency of the inverter cannot become higher than one kilohertz, and such a switching frequency produces a large current ripple, which then produces torque ripple. To minimize the current ripple, a method based on deadbeat control theory for current regulation is proposed. The pulsewidth modulation (PWM) pattern is determined at every sampling instant based on stator current measurements, motor speed, current references, and rotor flux vector, which is predicted by a state observer with variable poles selection, so that the stator currents are controlled to be exactly equal to the reference currents at every sampling instant. The proposed method consists of two parts: (1) derivation of a deadbeat control and (2) construction of a state observer that predicts the rotor flux and the stator currents in the next sampling instant. This paper describes a theoretical analysis, computer simulations and experimental results     

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.     

A Unified Artificial Neural Network Architecture for Active Power Filters

In this paper, an efficient and reliable neural active power filter (APF) to estimate and compensate for harmonic distortions from an AC line is proposed. The proposed filter is completely based on Adaline neural networks which are organized in different independent blocks. We introduce a neural method based on Adalines for the online extraction of the voltage components to recover a balanced and equilibrated voltage system, and three different methods for harmonic filtering. These three methods efficiently separate the fundamental harmonic from the distortion harmonics of the measured currents. According to either the Instantaneous Power Theory or to the Fourier series analysis of the currents, each of these methods are based on a specific decomposition. The original decomposition of the currents or of the powers then allows defining the architecture and the inputs of Adaline neural networks. Different learning schemes are then used to control the inverter to inject elaborated reference currents in the power system. Results obtained by simulation and their real-time validation in experiments are presented to compare the compensation methods. By their learning capabilities, artificial neural networks are able to take into account time-varying parameters, and thus appreciably improve the performance of traditional compensating methods. The effectiveness of the algorithms is demonstrated in their application to harmonics compensation in power systems     

The Design of Triode Harmonic Generators

EXISTING analytical methods for predetermining the anode and grid currents of a triode harmonic generator are examined. These methods are found to give large unpredictable errors which may be of the order of 25 per cent. A new analytical method is devised, based on a power series representation of the tube characteristics, whereby the anode current components can be forecast with a maximum error of less than 6 per cent for harmonic generation up to fifth order. This method is also applied to the prediction of grid currents and is found to be more accurate than previous analytical methods.     

Natural Current Balancing of Multicell Current Source Converters

This paper explores the issue of balancing the intermediate inductor currents of a multilevel current source inverter (CSI). The paper begins by identifying that single-phase multicell CSIs and flying capacitor voltage source inverters (FCVSIs) form a topological dual pair. This allows the established understanding of the natural balance process of the FCVSI intermediate capacitor voltages to suggest that the intermediate inductor currents of the CSI should also settle to their target balance values when phase-shifted carrier (PSC) pulse width modulation (PWM) is used. This concept is confirmed by full switched simulations. Next, an analytic model is developed to explore the dynamic response and robustness of the balancing process, using a double Fourier series representation of the converter switching signals to linearise a nonlinear transient circuit model. The model is verified against simulations, and predicts that the resistance of the intermediate inductors can perturb the steady state balancing point. The model further predicts that the resistance of the inductance must be small compared to the load resistance to minimize this effect. Results obtained on a five-level experimental CSI precisely match the theoretical model and hence support these conclusions.     

A new approach for minimum-torque-ripple maximum-efficiency controlof BLDC motor

Torque-ripple control of the brushless DC motor has been the main issue of the servo drive systems in which the speed fluctuation, vibration, and acoustic noise should be minimized. Most methods for suppressing the torque ripples require Fourier series analysis and either iterative or least-mean-square minimization. In this paper, a novel approach to achieve ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms which include the case of three-phase unbalanced conditions. As a result, the proposed approach provides a simple way to obtain optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results     

An improved deadbeat rectifier regulator using a neural netpredictor

This paper proposes a new input current reference prediction scheme for the deadbeat control of a three-phase rectifier used in AC/DC/AC converters. The inherent lag in deadbeat control is compensated by predicting the reference resulting in better performance. The proposed predictor consists of a neural net which is trained on-line and predicts the slow varying and periodic trends of the current reference plus a linear first order predictor which predicts the fast variations of the current reference time signal. A CRITIC decides if the neural net training is sufficient and therefore whether or not to use the prediction in the control loop. The learning rule used allows neural net weights to be trained whenever a parameter change causes an increased prediction error. This predictive-regulator is shown to result in improved performance in steady state, in the presence of input voltage imbalance or load variations     

基于LSTM算法的电子部件故障预测

故障诊断与预测使用大量信息数据,需要采用推断统计、神经网络等研究方法,对测试数据进行分析和预测,从而评估设备健康状况,在故障发生前对指标进行预测和采取预防举措,最大限度保证电子设备健康工作。本文提出了基于LSTM(长短时记忆网络)算法的电子设备部件故障预测模型,针对时序型数据对轴承运行状态进行分析和预测。     

Xenon flashlamp triggering for laser applications

Results of an investigation into the triggering of linear xenon flashlamps are presented, with particular reference to xenon flashlamps in laser applications. Measurements are described which give information on the arc formation process, trigger voltage thresholds, peak trigger currents, lamp energy output stability, and electromagnetic interference (EMI) for both series and parallel triggering. Particular attention is given to the performance obtained with both the correct and the incorrect polarities for the two types of triggering. The investigation makes extensive use of a high-speed streak camera and a wideband (100 MHz) continuous sweep spectrum analyzer, as well as more conventional instrumentation. It was found that: 1) the triggering process is extremely fast (≤50 ns) for both methods, but that parallel triggering produces trigger currents which are 100 times smaller than series; 2) the trigger current rather than the main energy, discharge current is the dominant EMI source; 3) the measured RF spectra show the corresponding EMI superiority of parallel over series; and 4) the two methods are equivalent in regard to the effect on lamp efficiency and stability.     

An exact integration procedure for vector potentials of thincircular loop antennas

A direct integration procedure for far-zone vector potentials of thin circular loop antennas has been known for many years. This method is general in the sense that it leads to simple integrals which have closed form solutions for most commonly assumed loop current distributions. However, a comparable integration technique has not been available for evaluating the more complicated near-zone vector potentials. This paper introduces a systematic approach for the exact integration of general near-zone vector potentials associated with current-carrying circular loop antennas. A particular example is considered where this new integration technique is used to find exact solutions to the vector potential and electromagnetic field integrals for loops with a Fourier cosine-series expansion of the current. The observation is made that degenerate forms of these exact representations lead to simplified expressions for the important special cases of a uniform and cosinusoidal current loop. Two equivalent forms of exact series expansions are derived for the uniform current vector potential and field integrals. It is shown that the familiar small-loop approximations, as well as the classical far-field expressions, may be obtained as limiting cases of the more general exact series representations for the uniform current loop obtained in this paper. Convenient asymptotic far-field expansions are derived for the loop with a cosinusoidal current distribution. Finally, the far-field analysis for the cosinusoidal loop is generalized to loops having an arbitrary current represented by a Fourier cosine series     

Harmonic filtering of high-power 12-pulse rectifier loads with aselective hybrid filter system

Current distortion of 12-pulse rectifier loads is significantly lower compared to six-pulse rectifier loads. However, in passive filtering of the lowest and dominant characteristic 11th and 13th harmonics, the use of 5th and 7th filters is often required in order to prevent possible parallel and series resonance between the passive filter and source impedance which can be excited by source background distortion or by load current residual noncharacteristic harmonics at the 5th and 7th harmonic frequencies. In hybrid filter systems, an active filter (AF) can be added in series with the passive filter in order to isolate the source and load. In most proposed hybrid filter systems, AF control is based on the detection of total current distortion and high-frequency inverters. With a selective AF control system and voltage-controlled inverter, the AF can be controlled to isolate the load at the critical frequencies only while at all other frequencies the passive filter function is preserved so that lower switching frequency and AF rating is required. In this paper, the authors present a selective AF filter control system and simple hybrid filter topology suitable for the compensation of high-power 12-pulse rectifier loads. Harmonic current controllers based on the second-order infinite-impulse response digital resonant filters are used, as they can be considered as simple digital algorithms for more complex double cascaded synchronous-reference-frame-based proportional plus integral controllers. They are centered to the targeted harmonic frequencies by using an adaptive fundamental frequency tracking filter. This approach gives good results, even if the reference waveform (in our case, a load voltage) is highly distorted or unbalanced and no separate phaselocked loop is required. Test results for a laboratory model of this system and stability analysis are presented and the importance of delay-time compensation is discussed     

Variable structure current control for induction motor drives byspace voltage vector PWM

In this paper, a variable structure current controller based on a space voltage vector PWM scheme is presented for induction motor drives. In this current controller design, only the current sensors are employed and we attempt to force the stator currents to be exactly equal to the reference currents rapidly. This proposed current controller, which is based on the space voltage vector PWM drive, exhibits several advantages in terms of reduced switching frequency, robustness to parameter variations, elimination of current/torque ripple, and improved performance in induction motor drive. It shows that the current control laws can be demonstrated in theory. Finally, simulation and experimentation results verify the proposed control scheme     

A four-switch shunt active filter based on one cycle control for compensating non-linear loads

ABSTRACT

This paper introduces a Four-Switch Three-Phase Shunt Active Power Filter (FSTP-APF) based on One Cycle Control (OCC) technique for compensating the currents of three phase non-linear loads. The power stage of FSTP-APF uses only four semiconducting switches which leads to reduce the overall cost of APF. The proposed technique retains the advantages of the conventional OCC, such as no reference current calculation, no need for using Phase-Locked Loop (PLL), very simple control circuit and constant switching frequency. In addition, the modification reduces the number of semiconductor switches, reduces the filter output inductances, reducing the number of sensors to only four sensors, two of them for measuring supply currents and the others for measuring DC-link voltages, and the control algorithm becomes simpler. The feasibility and performance of the proposed technique are demonstrated through the simulation and experimental verifications.     

High‐Performance Integrated ZnO Nanowire UV Sensors on Rigid and Flexible Substrates

Due to the large surface area‐to‐volume ratio and high quality crystal structure, single nanowire (NW)‐based UV sensors exhibit very high on/off ratios between photoresponse current and dark current. Practical applications require a large‐scale and low‐cost integration, compatibility to flexible electronics, as well as reasonably high photoresponse current that can be detected without high‐precision measurement systems. In this paper, NW‐based UV sensors were fabricated in large‐scale by integrating multiple NWs connected in parallel via the contact printing method. Linear scaling of the photoresponse current with the number of NWs is demonstrated. Integrated ZnO NW UV sensors were fabricated on rigid glass and flexible polyester (PET) substrates at the macroscopic scale. The flexible and rigid sensors performed comparably, exhibiting on/off current ratios approximately three orders of magnitude higher than sensors made from polycrystalline ZnO thin films. Under UV irradiance of 4.5 mW cm^?2 and 3 V bias, photoresponse currents and on/off current ratios for the rigid and flexible UV sensors reached 12.22 mA and 82 000, and 14.1 mA and 120 000, respectively. This result suggests that lateral integration of semiconductor NWs is an effective approach to large‐scale fabrication of flexible NW sensors that inherit the merits of single‐NW‐based systems with unaffected performance compared to using rigid substrate.     

Temperature rise measurement for power-loss comparison of an aluminum electrolytic capacitor between sinusoidal and square-wave current injections

DC-link capacitors are a major factor of degrading reliability of power electric converters because they usually have a shorter lifetime and higher failure rate than those of semiconductor devices or magnetic devices. Characteristics of the capacitors are usually evaluated by a single sinusoidal current waveform. However, actual current flowing out of the converter into the capacitor is a modulated square current waveform. This paper provides experimental comparison of the power loss dissipated in an aluminum electrolytic capacitor between sinusoidal and square-wave current injections. Power loss is estimated by temperature rise of the capacitor. Experimental results confirm that power losses of the square-wave current injection were always lower than those of the sinusoidal current injection by 10–20%. Moreover, the power losses of the square-wave current injection can be estimated by a synthesis of fundamental and harmonic currents based on the Fourier series expansion, which brings a high accuracy less than 1% when more than fifth harmonic current is introduced. This comparison will be useful for estimating power loss and life time of electrolytic capacitors.     

A 12 kW three-phase low THD rectifier with high-frequency isolation and regulated DC output

A robust 12 kW rectifier with low THD in the line currents, based on an 18-pulse transformer arrangement with reduced kVA capacities followed by a high-frequency isolation stage is presented in this work. Three full-bridge (buck-based) converters are used to allow galvanic isolation and to balance the dc-link currents, without current sensing or current controller. The topology provides a regulated dc output with a very simple and well-known control strategy and natural three-phase power factor correction. The phase-shift PWM technique, with zero-voltage switching is used for the high-frequency dc-dc stage. Analytical results from Fourier analysis of winding currents and the vector diagram of winding voltages are presented. Experimental results from a 12 kW prototype are shown in the paper to verify the efficiency, robustness and simplicity of the command circuitry to the proposed concept.     

Multiply driven and loaded coaxial circular loop arrays

Characteristics of single- or double-loaded coaxial loop arrays with arbitrary circumferences are studied when the sources or loads are located diagonally on the loops. For finite gaps at the deriving points and finite lengths of the loads, integral equations for the loop currents are obtained. These integral equations are then reduced to a matrix one by expanding the currents and the kernel in Fourier series of the azimuthal coordinate. For the special case of loaded Yagi arrays numerical results for the gain and the input impedance are presented. These results reveal that a capacitive loading of the array generally broadens the gain bandwidth of the array over which the gain remains essentially constant. A resistive loading of the exciter, on the other hand, yields a broadband characteristic for the driving-point admittance.     

Characterization on acceleration-factor equation for packaging-solder joint reliability

The well-known Norris-Landzberg acceleration factor (N-L AF) empirical equation was developed based on the accelerated thermal cycling (ATC) test. It has been widely used for many years to predict product lifetimes. However, some recent test results have shown the insufficiency of this equation when the ramp rates change. The AF equation predicts a longer lifetime when the ramp rate is higher, which contradicts the experimental test data. The reason for this discrepancy is that the N-L AF equation combines both ramp rate and dwell time factors in one frequency term. Thus, modifying the current AF equation to more precisely predict product lifetimes has become an important topic.This study proposes a new AF equation to decouple the effects of the ramp rate and dwell time during an ATC test, replacing the frequency term used in the N-L equation with two new terms. One is related to the ramp rate for the strain rate effect, and the other is related to the dwell time for the creep effect of the packaging solder joint material. The new AF equation produces a good correlation between the simulation and test results for different package types discussed in the literature with various ramp rates and dwell times.