Influence of voltage and load current on dc bipolar corona pulses

Digitizing oscilloscopes were used to observe anode and cathode corona pulses on a laboratory scale HVDC bipolar transmission line. Data was collected with the transmission line energized at a nominal voltage of ±60 kV with no load current. The effects of increased voltage and added load current were then separately investigated. Histograms show distributions of corona pulse amplitude and time between consecutive corona pulses (corona pulse time separation). Increasing the transmission line voltage had the effect of increasing corona pulse amplitude and decreasing corona pulse time separation for both anode and cathode. Addition of load current decreased the corona pulse amplitude and increased the corona pulse time separation for the anode. The cathode corona pulse amplitude and pulse time separation decreased with the addition of load current     

Analysis of corona losses on monopolar dc transmission lines

This paper presents a charge-simulation-based method to solve the equations describing the ionized field around monopolar transmission lines. The method is applied for calculating the corona power-loss and ground-level current-density profile of the conductor bundles of two and three subconductors. Different orientations of the conductor bundle is sought to investigate how the ground-level current-density profile is influenced by the orientation of the bundle with respect to the ground plane. The change of the corona onset voltage from point-to-point on each subconductor is taken into account. The calculated corona power-loss and ground-level current-density of bundle conductors agreed fairly with those measured experimentally for a laboratory model.     

Factors affecting corona on twin-point gaps under dc and ac HV

The factors affecting corona formation on twin-point/plane gaps are investigated both theoretically and experimentally. In the theoretical analysis, an electrostatic field computation program based on the charge simulation method was used to get the electric field profile on the plate for different gap lengths and interspacings between the two points. Also, the effect of voltage level, air pressure and gap length on the number of axial streamers occurring across the critical field line was introduced for a constant time duration. The variation of the integral of the ionization coefficient with the axial length from the point was studied. Finally, a study of the effect of air pressure and gap length on both the corona inception voltage and critical length was presented. Corona formation in single and twin-point/plane gaps also was investigated experimentally under both high direct and alternating voltages. There are many factors affecting such corona formation. The investigated factors were the interspacing between the two points, gap length between the point and the plane, ambient temperature, relative humidity, polarity or frequency of the applied voltage, and electrode material. In order to study and explain such phenomena, a photographic investigation together with a simultaneous measurement of both the applied voltage and the corona current were introduced. Curve fitting of the dc corona current vs. gap length and voltage for both single and twin-point/plane gaps gave the conventional relationship, but in case of twin point the power of the gap length varies between 1.2 and 1.3     

Inception voltage of corona in bipolar ionized fields-effect oncorona power loss

In this paper, an iterative finite-element-based algorithm is presented as a numerical tool for the solution of the bipolar ionized field around high-voltage DC (HVDC) transmission lines. The effect of including unequal values of the positive and negative corona inception voltages and ion mobilities on the corona power loss is investigated. In addition, the effect of negative ion field enhancement on reducing the positive conductor corona inception voltage is also studied. The present algorithm is applied to different laboratory and full-scale transmission line configurations. Comparison with previously computed V-I characteristics showed that the present computed values were in better agreement with the experiment. Also, it has been found that the effect of unequal corona inception voltages on the corona power loss (or corona current) is noticeable at applied voltages very near to the inception values     

Modeling and simulation of ac–dc buck-boost converter fed dc motor with uniform PWM technique

PWM controlled rectifiers can efficiently and economically be employed in low and medium power applications of dc drives and in front-end converters of rectifier–inverter systems while maintaining the advantages of design simplicity and operation reliability of naturally commutated schemes. Due to the high dc voltage that is produced which is greater than the peak voltage of the utility supply, the ac–dc buck-boost converter is especially suited as a front-end power source in variable-speed drive systems to convert the utility supply voltage into a variable dc link voltage where a single-phase or a three-phase utilities power supply is available. In this paper, the dynamic model and steady state equivalent circuit of a single-phase ac–dc buck-boost converter fed dc motor with uniform PWM control is presented. The waveforms of voltage and current, the input and output characteristics of the converter are discussed and verified. Measured, computed and simulated results are shown to be very close and the model is proved to be efficient and accurate.     

Monte Carlo simulation of electrical corona discharge in air

Electrical discharges play a key role in technologies; there are many industrial applications where the corona discharge is used. Air as insulator is probably the best compromise solution for many applications. All of this reflects on the great importance of the evaluation of the corona performance characteristics. Numerical simulation of the corona discharge helps to better understand the involved phenomena and optimize the corona devices. This paper is aimed at calculating the corona discharge in negative point-plane air gaps. To describe the non-equilibrium behavior of the electronic avalanches and to simulate the development of corona discharge the method of Monte Carlo has been used. This model provides the spatial-temporal local field and particles charged densities variations as well as the ionization front velocity.     

A new interleaved bidirectional dc/dc converter with zero voltage switching and high voltage gain: analyses,design and simulation

In this paper, a new interleaved non‐isolated bidirectional dc–dc converter with capability of zero voltage switching and high voltage gain is proposed. In the proposed converter by using two coupled inductors and one capacitor, the voltage gain is extended. Moreover, by using only an auxiliary circuit that includes an inductor and two capacitors, the zero voltage switching (ZVS) of two used switches in the first phase of converter can be achieved. The ZVS operation of two used switches in the second phase is always obtained without using any extra auxiliary circuit. This converter similar to other interleaved converters has low input current ripple and low current stress on switches. In this paper, the proposed converter is analyzed in all operating modes, and also the voltage gain, required conditions for ZVS operation of switches, voltage and current stresses of all switches, and the value of input current ripple in both boost and buck operations are obtained. Finally, the accuracy performance of the proposed converter is verified through simulation results in EMTDC/PSCAD software. Copyright © 2017 John Wiley & Sons, Ltd.     

Robust decentralized control of parallel dc/dc converters

Robust decentralized linear feedback controllers for parallel operating dc/dc converters, using the structured singular value approach, are investigated. Different structures of decentralized controllers were applied and tested. The controllers were designed for structured and unstructured modeluncertainty. The gain directionality compensation, due to a high condition number was considered.Eine robuste und dezentralisierte Regelung für parallele Gleichstromwandler wurde untersucht. Verschiedene Strukturen des Regelungsverfahren wurden angewandt und getestet. Die Regelung wurde für den Fall der strukturierten und unstrukturierten Perturbation entworfen.     

Design of generalized class E2 dc/dc converter

This paper presents a novel design procedure for class E² dc/dc converter. The design procedure requires only circuit equations and design specifications. When the circuit equations are got, the other procedures for the computation of the design values are carried out with aid of computer. Therefore, we can design class E² dc/dc converters with any conditions by using the proposed design procedure. Moreover, we give the design and the performance curves of class E² dc/dc converter and discuss about them. By carrying out the circuit experiments, we show the validity of the proposed design procedure. Copyright © 2003 John Wiley & Sons, Ltd.     

紫外电晕检测仪在电晕放电检测中的应用

首先阐述一种新型紫外电晕检测仪的原理,介绍该仪器目前在国外的应用情况,然后分析该类仪器在系统应用中技术特点和存在的一些问题,最后结合电力系统快速发展的展望了应用的前景。     

Design of advanced robust decentralized control of parallel dc/dc converters

Contents This paper presents the useful analysis and synthesis technique for the design of multivariable feedback systems. Optimal robust decentralized controllers of nominal and diagonal dominant nominal model of parallel operating dc/dc converters using structured singular value approach are designed. The proposed controllers have different number of tuning parameters and they are robust for both reference signals and disturbances. The robustness of feedback systems with designed controllers is investigated and compared. Simulation results, both in frequency and time domain, demonstrate the preferable performance of the designed decentralized controllers in setpoint tracking and disturbance rejection.

---

Verbesserte robuste dezentralisierte Regelung für parallele Gleichstromwandler

Übersicht Der Artikel stellt eine für den Entwurf dezentraler Regelungen für parallele Gleichstromwandler geeignete Methode dar, die auf neueren Entwicklungen auf dem Gebiet der multivariablen Regelungssysteme aufbaut. Es werden optimale robuste dezentralisierte Regler für das nominale und das diagonal-dominante nominale Modell für einen parallelen Gleichstromwandler anhand der strukturierten singulären Werte entworfen. Diese Regler haben eine unterschiedliche Zahl von Einstellparametern und sind robust bezüglich des Führungs- und Störverhaltens. Die Robustheit des Rückkopplungssystems für die entworfenen unterschiedlichen Regler wird vergleichend untersucht. Die Simulationsergebnisse im Zeit- und Frequenzbereich lassen erkennen, daß mit den entworfenen dezentralen Reglern eine verbesserte Regelgüte bezüglich der Sollwertfolge und der Störgrößenbekämpfung erzielt wird.

     

Studies on robust control of parallel operating dc/dc converters

Contents In this paper, an optimal robust control approach for parallel operating dc/dc converters is presented. Various types of controllers using frequency domain optimization method based on -optimality framework are designed. Different structures of low-order controllers, decentralized controller and a new controller based on Internal Model Control (IMC) theory are developed to improve the robust performance of parallel operating dc/dc converters against uncertainties and disturbances. The proposed controllers are robust for setpoints and/or for disturbances. Finally, a comparison between the performance of the closed-loop system with designed robust decentralized and IMC controllers is obtained.

---

Untersuchung verschiedener robuster Regelungsstrukturen für parallele Gleichstromwandler

Übersicht Im Mittelpunkt des Beitrages steht die vergleichende Untersuchung verchiedener robuster Mehrgrößen-regelungsstrukturen für parallele Gleichstromwandler. Der Entwurf der Regler erfolgt im Frequenzbereich und nutzt das -Analyse- und Synthesekonzept. Es werden verschiedene Reglertypen niedriger Ordnung, dezentrale Regler und ein neuer IMC (Internal Model Control) Regler betrachtet. Ziel ist es, die Robustheit der Regelgüte bezüglich Modellungenauigkeiten und Störeinflüssen bei parallelen Gleichstromwandlern zu verbessern. Die vorgeschlagenen Regler zeigen robustes Führungs- und/oder Störverhalten. Abschließend erfolgt ein Vergleich der Regelgüte, die entworfenen robusten dezentralen und IMC-Regler im geschlossenen Kreis erreichen.

     

SPICE‐aided modelling of dc characteristics of power bipolar transistors with self‐heating taken into account

This paper deals with the problem of calculations of the dc characteristics of power bipolar transistors (BJTs) with self‐heating taken into account. The electrothermal model of the considered devices dedicated for PSPICE is presented. The correctness of the model was verified experimentally in all ranges of the BJT operation. Two transistors—BD285 and 2N3055—were arbitrarily selected for investigation. A good agreement between the measured and calculated characteristics of these transistors was observed. Copyright © 2009 John Wiley & Sons, Ltd.     

Particle-in-cell simulations on a single gap gas discharge

In order to help understand the mechanisms of gas discharges at a low pressure and high voltage, simulations on the initial phase of a single gap gas discharge in the case of atomic hydrogen has been carried out, based on the models of the explosive electron emission and neutral gas ionization, by using the self-consistent, 2-1/2 dimensional particle-in-cell W MAGIC 2DT code. The motion patterns of the charged particles during the initial process of the gas discharge are obtained at a hydrogen pressure of 1.33/spl times/10/sup -2/ Pa and an applied voltage of 10 kV. The profiles of phase space, the statistic histograms of velocities for the charged particles in the gap, the net charge density along the symmetrical axis direction, as well as the effects of applied voltage in the range of 10-40 kV and gas species (e.g. H/sub 2/, N/sub 2/ and Ar) on the characteristics of gas discharges are presented. Results also show that some simulations are in good accordance with existing experimental data.     

一种考虑冲击电晕及线路参数频变的电磁暂态仿真方法

在对冲击电晕的伏库特性分析的基础上,通过将线路分为多个不长的小段,在每段线路两边插入考虑冲击电晕的附加电容,从而既计及了冲击电晕对电磁暂态的影响,又与现有的线路模型相兼容.通过雷击输电线路的电磁暂态仿真表明,考虑冲击电晕与不考虑冲击电晕的电磁暂态过程相差很大,因此在研究行波保护的雷电波抗干扰方法时应该考虑冲击电晕对电磁暂态过程的影响.     

一种考虑冲击电晕及线路参数频变的电磁暂态仿真方法

在对冲击电晕的伏库特性分析的基础上,通过将线路分为多个不长的小段,在每段线路两边插入考虑冲击电晕的附加电容,从而既计及了冲击电晕对电磁暂态的影响,又与现有的线路模型相兼容。通过雷击输电线路的电磁暂态仿真表明,考虑冲击电晕与不考虑冲击电晕的电磁暂态过程相差很大,因此在研究行波保护的雷电波抗干扰方法时应该考虑冲击电晕对电磁暂态过程的影响。     

基于Ansoft新型交直流混合供电系统接口变压器仿真研究及解决因直流引起的磁饱和问题的措施

针对直流注入交流系统会引起变压器的直流偏磁,使变压器铁芯饱和趋于严重、漏磁增加、谐波含量增加、励磁电流畸变的问题,提出一种在Zigzag变压器的中性点注入直流,有效应对因直流引起的磁饱和问题。构建Ansoft Maxwell环境下的仿真模型,对变压器的磁力线、磁场强度、磁链曲线交链、电压电流波形进行有限元分析,实验结果表明注入直流电流后主磁力线变化并不大,漏磁力线减少。