Compensation Characteristics Research Articles

An Optimization-Based Algorithm for Shunt Active Filter Under Distorted Supply Voltages

In this paper, an optimization-based control algorithm for the compensation of steady-state load under distorted supply voltages is presented. For balanced and sinusoidal supply voltages, load compensation using shunt active filter produces perfect harmonic cancellation (PHC) and unity power factor (UPF) source currents. However, when the supply voltages are distorted, compensation for PHC will not provide UPF, as the harmonics in the supply voltages are not utilized for delivering the average power. In the same way, to achieve UPF source currents, the compensated source currents should have the same harmonics, unbalance, shape, and be in phase with the respective supply voltages, thereby violating the perfect harmonic cancellation objective. Hence, there should be an optimal operation between these two important compensation characteristics. The optimization-based control algorithm presented in this paper gives the best power factor while satisfying the constraints such as total harmonic distortion limits and average power balance of source currents. It is also flexible to adopt different compensation characteristics based upon the supply voltage conditions. Matlab and its optimization toolbox are used for simulation studies and solving the nonlinear optimization problem, respectively. The algorithm is validated by using a prototype of digital signal processor (TMS320F2812PGFA)-based shunt active power filter. Detailed experimental results are presented.

Application of neutron transmutation doping method to initially p-type silicon material

The neutron transmutation doping (NTD) method was applied to the initially p-type silicon in order to extend the NTD applications at HANARO. The relationship between the irradiation neutron fluence and the final resistivity of the initially p-type silicon material was investigated. The proportional constant between the neutron fluence and the resistivity was determined to be 2.3473×10 19 n Ω cm −1. The deviation of the final resistivity from the target for almost all the irradiation results of the initially p-type silicon ingots was at a range from −5% to 2%. In addition, the burn-up effect of the boron impurities, the residual 32P activity and the effect of the compensation characteristics for the initially p-type silicon were studied. Conclusively, the practical methodology to perform the neutron transmutation doping of the initially p-type silicon ingot was established.

Design and Implementation of a Hybrid Output EMI Filter for High-Frequency Common-Mode Voltage Compensation in PWM Inverters

This paper presents a hybrid output electromagnetic interference (EMI) filter for common-mode voltage compensation in pulsewidth-modulation (PWM) inverters. Its structure is composed of a single-leg four-level active filter connected in series with a low-frequency blocking capacitor and a small passive LC filter that which enhances the suppression of the common-mode voltage in the high-frequency range. The series capacitor helps in avoiding the core saturation of the common-mode coupling transformer caused by the low-frequency components of the common-mode voltage. Detection of PWM voltages by high-speed optoisolators is done at the inverter's output to achieve better common-mode voltage detection and compensation characteristics. Analysis and design guidelines for the hybrid filter are also given to facilitate systematic design in the real implementation of the filter. Experimental results with a real drive system clearly illustrate a significant reduction of the common-mode voltage, the leakage current, the shaft voltage, and the bearing current.

Medical Malpractice and the Chest Physician

The US malpractice system is based on tort law, which holds physicians responsible for not harming patients intentionally or through negligence. Malpractice claims are brought against physicians from most medical disciplines in proportion to their numbers in practice and to the frequency with which they perform procedures. Claims against chest physicians most commonly allege injuries caused by the following: (1) errors in diagnosis, (2) improper performance of procedures, (3) failure to supervise or monitor care, (4) medication errors, and (5) failure to recognize the complications of treatment. Most of these injuries occur in hospitals, and many of the injured patients die. The social goals of the medical malpractice system include the following: (1) compensating patients injured through negligence, (2) exacting corrective justice, and (3) deterring unsafe practices by creating an economic incentive to take greater precautions. Some patients injured through negligence are compensated, but most are not. Claims are brought against some negligent physicians but also some who are not negligent, and being negligent does not guarantee that a claim will be brought. The deterrent effect of medical malpractice is unproven, and the malpractice system may prompt defensive medicine and increase health-care costs. And by stressing individual accountability, it conflicts with a systems-oriented approach to reducing medical errors.

Control Strategies for Load Compensation Using Instantaneous Symmetrical Component Theory Under Different Supply Voltages

In this paper, the theory of instantaneous symmetrical components is applied to explore various control strategies of load compensation, under different supply voltages. When the supply voltages are balanced and sinusoidal, all of these strategies converge to the same compensation characteristics. However, when the supply voltages are not balanced sinusoids, these control strategies result in different degrees of compensation in harmonics, power factor, neutral current, and compensator ratings. These control strategies are discussed in detail and a comparative study of their performance in terms of the rms value, total harmonic distortion, power factor of source currents, and compensator ratings is presented. Based on this study, it is possible to select the best strategy to meet the required load compensation characteristics for available supply voltages. A three-phase four-wire distribution system supplying an unbalanced and nonlinear load is considered for simulation study. The detailed simulation results using MATLAB are presented to support the proposed compensation strategies.

Gate-controlled series compensator on gate-controlled power semiconductor devices

Characteristics of a nonreactor series compensator (NRSC) based on a gate-controlled power semiconductor for the production of flexible (controlled) AC power lines are considered. Analytical solutions of the transient equation on the commutation of gate switching in an NRSC circuit for steady-state processes are obtained. The forms of currents and voltages in the NRSC circuit are analyzed. The dependence of the equivalent impedance of NRSC on the commutation delay angle of gate control and its effect on the degree of compensation for an electric power line (EPL) are determined. A comparison of the characteristics of an NRSC and a thyristor-controlled series compensator (TCSC) is performed. Estimation of the maximum switching frequency of an NRSC is given; the effect of an NRSC on the distortion of the curves of currents and voltages in EPLs is shown.

A Practical Series-Shunt Hybrid Active Power Filter Based on Fundamental Magnetic Potential Self-Balance

In this paper, a novel series-shunt hybrid active power filter based on fundamental magnetic potential self-balance is reported. It consists of three parts: a passive power filter, a voltage-source pulsewidth-modulated (PWM) converter and a series zero magnetic flux current transformer. The zero magnetic flux current transformer locating in series between the power supply and nonlinear loads presents low reactance to fundamental and high impedance to the harmonics automatically. And the harmonic voltage dropped on the zero magnetic flux current transformer can be detected in real time. The voltage-source PWM converter is controlled as a harmonic voltage source. Wherein, it is connected to the passive filters in series through an isolated transformer. Therefore the flow-in harmonic current will be less than before. The configuration, working principle and performance analysis of the designed hybrid active power filter are determined. The validity of the theory and excellent compensation characteristics are proved by an experimental prototype. The current distortion factor is decreased from 20.46% to 2.67% by using this hybrid active power filter.

A New Method of Compensating Harmonic Currents for Wind Power Generation Systems with the Soft Starter Using a Hybrid Active Filter

This paper proposes a new method of compensating harmonic currents for wind power generation systems with the soft starter using a hybrid active filter. The hybrid active filter consists of single-tuned LC and small-rated active filters. The single-tuned LC filter absorbs the harmonic current while behaving as a phase-leading capacitor for the fundamental component. The small-rated active filter improves the compensation characteristics of the passive filter under the soft start of the constant-speed wind turbine. The required rating of the active filter can be reduced because the active filter does not supply the fundamental reactive current. The basic principle of the proposed compensation method is discussed, and then confirmed by digital computer simulation using PSCAD/EMTDC. Simulation results demonstrate that the waveform of the source current becomes sinusoidal under the soft start. The required rating of the active filter is about 8.5% of the induction generator rating. A new calculation method of THD with the detrending algorithm is proposed for the transient state. The THD of the source current is about 7.3% using the hybrid active filter.

통신해양기상위성의 영상위치유지 성능평가 프로그램 개발 및 분석

이 연구는 통신해양기상위성의 영상위치유지 (Image Navigation and Registration, INR) 시스템의 시뮬레이션을 위한 프로그램을 개발하고, 영상오차보상(Image Motion Compensation, IMC) 알고리즘의 성능을 비교분석 하였다. 통신해양기상위성 궤도와 자세 요소를 모델링 하고 궤도오차와 자세오차를 계산하여 이러한 궤도 및 자세오차가 영상왜곡에 미치는 영향을 분석하였다. 또한 영상오차보상을 하지 않았을 경우와 GOES 위성의 영상오차보상 알고리즘을 적용하였을 경우, 그리고 선행 연구를 통해 개발되었던 개량된 영상오차보상 알고리즘을 적용하였을 경우의 영상들을 비교하여 각 알고리즘의 성능을 확인하였다. 개량된 영상오차보상 알고리즘은 GOES위성의 알고리즘보다 효율적으로 영상왜곡을 보상하였다. 이러한 연구는 통신해양기상위성의 INR시스템을 효과적으로 운용하고 그 성능을 향상시킬 수 있는 기술적 토대를 마련하는데 기여할 것이다. We developed a software for simulations and analyses of the Image Navigation and Registration (INR) system, and compares the characteristics of Image Motion Compensation (IMC) algorithms for the INR system. According to the orbit errors and attitude errors, the capabilities of the image distortions are analyzed. The distortions of images can be compensated by GOES IMC algorithm and Modified IMC (MIMC) algorithm. The capabilities of each IMC algorithm are confirmed based on compensated images. The MIMC yields better results than GOES IMC although both the algorithms well compensate distorted images. The results of this research can be used as valuable asset to design of INR system for the Communication, Ocean, Meteorological Satellite (COMS).

Recovery of Vestibular Imbalances After Vestibular Neuritis

To determine chronological characteristics of vestibular recovery after vestibular neuritis (VN) by using various clinical parameters. Prospective clinical study. Twenty of 22 consecutive patients with acute VN underwent serial follow-ups of static (spontaneous nystagmus, subjective visual vertical, and ocular torsion) and dynamic (head-shaking nystagmus [HSN], vibration-induced nystagmus [VIN], head thrust test, and caloric test) vestibular imbalances for 1 year after symptom onset. Static vestibular imbalances improved more rapidly than dynamic imbalances. Among the dynamic imbalances, a trend of higher recovery rate was found in head thrust sign, HSN, and VIN than in caloric asymmetry. HSN tended to be more sensitive in detecting vestibular asymmetry than VIN and head thrust sign. Some patients showed direction reversal of HSN (n = 5, 25.0%) or VIN (n = 5, 25.0%) during follow-up. Direction of VIN changed according to the stimulation sites in four (20.0%) patients. In view of more rapid resolution of static vestibular imbalance after VN, evaluation of the dynamic vestibular imbalances may provide more useful information for underlying vestibulopathy, especially in the compensated phase. The different temporal profiles ofdynamic vestibular recovery may reflect different chronological characteristics of vestibular compensation according to stimulus frequency. Direction reversal of HSN and VIN during follow-up suggests that lateralization of VNbased on the direction of these nystagmus should be considered in the context of disease phase.

Parallel voltage sag compensator with reduced capacitance using a boost‐type power factor correction rectifier

AbstractA new circuit of parallel‐type voltage sag compensator is proposed in this paper. The proposed voltage sag compensator can reduce the necessary capacity of the energy storage capacitor for compensation by boost‐type power factor correction rectifier charging the capacitor during a voltage sag. As a result the proposed system can reduce the size and maintenance of the apparatus. Copyright © 2004 Wiley Periodicals, Inc.This paper shows the principle and control system of the proposed circuit. Compensation characteristics were demonstrated by simulation and experiment. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(2): 19–33, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20261

Control Methods and Compensation Characteristics of a Series Active Filter for a Neutral Conductor

Due to the advance of information technologies, a large number of electronic products such as personal computers have been connected to power distribution systems in commercial buildings. Hence, voltage distortion on utility outlets and excessive neutral current on distribution lines have arisen and lead to a number of serious problems in the distribution system. Two control methods and the related compensation characteristics of a series active filter connected to the neutral conductor are presented in this paper. The distinct functions of the proposed active filter are the mitigation of the third-harmonic voltage and the neutral current in a three-phase four-wire distribution system in a building. The required power of the proposed active filter is less than 10% of that of the harmonic-producing loads. A control method of the dc capacitor voltage on the active filter circuit is also described. It is clarified through experiments that one of the two functions of the active filter can be realized selectively and the dc capacitor voltage of the active filter can be regulated to a desired value

Strategies and Operating Point Optimization of STATCOM Control for Voltage Unbalance Mitigation in Three-Phase Three-Wire Systems

Reactive power control through the static compensator (STATCOM) has gained wide attentions due to its outstanding performance. But for a STATCOM with traditional control strategies, unbalanced utility voltages will greatly affect the performance of the STATCOM and, in severe cases, may even cause the shutdown of the STATCOM for overcurrent protection. This paper proposes novel control strategies to ensure normal operation of STATCOM in three-phase three-wire systems when severe system voltage unbalance occurs and, furthermore, to mitigate voltage unbalance at the point of common coupling (PCC) whether it is caused by the utility or load. The control laws, operation principles, compensation characteristics, and operating point optimization of the proposed control strategies are analyzed and compared in detail. The power flow in the STATCOM and corresponding dc-side voltage-control schemes for these control strategies are also introduced. It is shown that the proposed voltage-controlled current source (VCCS) strategy and modified voltage-controlled voltage source strategy are valid for voltage unbalance compensation, especially the VCCS strategy for low rating under the same performance. Finally, the simulation and experimental investigations were carried out with these three parameter-optimized control strategies, respectively, for light and heavy load conditions. The results verified that the current passing through the STATCOM is under control and the voltage at the PCC is more balanced than before compensation. The compensation performance of the STATCOM is thus proven satisfactory

Corporate governance, excess compensation, and CEO turnover in family and non-family businesses

The replacement of a CEO is one of the control mechanisms that companies employ to reduce the agency problems. This paper divides companies into non-family businesses and family businesses and investigates the influence of outside directors, outside blockholders, and excess compensation in CEOs termination process. The samples used in the paper come from manufacturing companies in Taiwan listed between 1996-1997; the analytical method is logistic regression model. The conclusion is as follows: 1. the characteristics of family businesses, corporate governance, and excess compensation have no correlation on CEO turnover. 2. External board members play an important role in CEO termination in non-family businesses

Should employment authorities worry about mergers and acquisitions?

This paper considers the role of mergers and acquisitions on employment. First, it considers the importance of different aspects of compensation policy and human resource management practices for distinguishing acquired and acquiring firms. Second, it examines which individuals from which firms remain with the newly created entity after the takeover. Using a unique employer–employee linked data set for France, we find that very few observable workforce or compensation characteristics distinguish acquired from acquiring firms ex-ante. Nevertheless, the human resources department seems to be quite active in the post-takeover period, with employees of the acquired firm having a lower probability of continued employment with the new entity in the short term after takeover than those of the acquiring firm and with the differences between the two types of firms disappearing after 3 years. The workers with characteristics that tend to be associated with the fastest subsequent job finding in the displaced worker literature are also those who tend to be overrepresented among the individuals who separate from their employer post-takeover. Finally, as both acquired and acquiring firms differ from firms not involved in takeover activity in a similar manner, employment authorities may be able to anticipate the regions in which takeovers are more likely to occur by looking at the financial accounts of firms with particular characteristics that have local establishments.

A Novel Concept of Gamma-Ray Compensation for Neutron Ionization Chamber

A novel method of γ-ray compensation in a neutron ionization chamber (CIC) is developed as an ex-core nuclear instrumentation in a pressurized water reactor. To minimize the dependence of the compensation efficiency on γ-ray dose and dose rate, the improved CIC has the signal electrode with small holes to induce leakage or fringing electric fields. Change in compensation characteristics could be controlled by adjusting the field strength. It has been shown that the compensation margin for adjustment can be extended to 5-8%.

울트라커패시터를 이용한 UPS의 순시전압보상에 관한 연구

본 논문은 순간전압강하 보상을 위해 축전지와 울트라커패시터가 병렬로 연결된 무정전 전원장치 시스템을 제안하였다. 축전지와 병렬로 연결된 울트라커패시터는 정전시 순간전압강하를 보상하고, 출력전압의 전압 변동률을 감소시키는 역할을 한다. 무정전 전원장치에서 울트라커패시터의 빠른 순간전압보상 구현을 위해 3[㎸A]의 시스템을 제작하여 실험을 수행하였다. 실험결과를 통하여 울트라커패시터의 빠른 보상특성과 울트라커패시터를 사용함으로써 출력전압의 변동률이 5[%]이내를 만족함을 확인하였다.

Lorenz Dominance and Non-welfaristic Redistribution

Our concern is for income inequalities that may result from non-welfaristic redistribution schemes. We show that for large classes of income functions Lorenz dominance results can be found in the comparison of two egalitarian equivalent mechanisms. Comparisons of different conditionally egalitarian mechanisms only yield poverty dominance results. In general, no egalitarian equivalent mechanism can be Lorenz dominated by a conditionally egalitarian mechanism. Our analysis stresses the need for accurate empirical estimates of the pre-tax income function and of the distributions of responsibility and compensation characteristics.

Control methods and compensation characteristics of a series active filter for neutral conductor

AbstractWith an increase in the number of electronic devices, such as personal computers, connected to power distribution lines in commercial buildings, problems associated with their use, such as voltage distortion on utility outlets and excessive neutral current on the distribution lines, become more and more serious. This paper shows control methods and compensation characteristics of series active filters connected to the neutral conductor. The distinctive functions of the proposed active filter are the mitigation of third harmonic voltage and the reduction of neutral current in three‐phase four‐wire distribution systems. The required kVA rating of the proposed active filter is less than 10% of that of the harmonic producing leads. A control method of the DC capacitor voltage on the active filter circuit is also described. It was experimentally demonstrated that one of these two functions of the active filter (to mitigate harmonics or to reduce the neutral current) can be realized selectively and that the DC capacitor voltage of the active filter can be regulated to a desired value. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(4): 53–63, 2006; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20227

A digital predistorter for power amplifier with memory effect

When a conventional predistorter compensating the nonlinear distortion in a power amplifier is used, the compensation characteristics deteriorate as the signal bandwidth is increased, to such a degree that the memory effect is no longer negligible. In this paper, it is shown experimentally that the memory effect is caused by fluctuations of the input voltage at low frequency. Measured data are introduced into the simulation. A predistorter that can deal with the memory effect is presented. It is shown by simulation and experiments that the distortion compensation characteristic can be improved. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(12): 20–30, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20314