Short-circuit Point Research Articles

An Improvement Method for Extracting Five Parameters of a Solar Cell Based on Lambert <i>W</i>-Function with the Current-Voltage Data

This article proposes a new method for the extraction of five parameters of a solar cell using Lambert W-function with the current-voltage data. Here we select three points: the short circuit point, the open circuit point, and the maximum power point. On the basis of these we construct five equations to establish a nonlinear formula, in which the series resistance can directly be obtained. The other four parameters are calculated by series resistance. This method is confirmed by two different solar cell data in Matlab software.

310 電磁場逆解析によるリチウムイオン電池内の内部短絡の位置同定に関する研究

Lithium ion battery is generally used in mobile devices for its advantages such as easy downsizing and weight saving due to high energy density. If there were short circuit points in the battery, the abnormal heating occurred for higher energy density than conventional batteries. It is necessary to identify the short circuit parts in Lithium ion battery. However, it is difficult to clarify the micro abnormal part in the battery by diagnosis imaging such as X-ray inspection. Therefore, a new technique of localization of short circuit part has been developed by using inverse analysis of the electromagnetic filed around the battery. This method can inspect the short circuit part in the battery by estimating the electric current value at the arbitrary point from data of the magnetic field around the battery. Because the technique is nondestructive inspection of short circuit part in the battery and able to quantitatively evaluate by electric current value, it will be expected to reduce the inspection cost and to improve the detection accuracy of shirt circuit in the battery. In this report, the effectiveness of this method was discussed through the electric current distribution calculated from the distribution of magnetic flux density around the specimen modeled the battery with one or two internal short circuit parts.

OS0601 磁気センサを用いたリチウムイオン電池内の内部短絡の位置同定に関する研究

Lithium ion battery is generally used in mobile devices for its advantages such as easy downsizing and weight saving due to high energy density. If there were short circuit points in the battery, the abnormal heating occurred for higher energy density than conventional batteries. It is necessary to identify the short circuit parts in Lithium ion battery. However, it is difficult to clarify the micro abnormal part in the battery by diagnosis imaging such as X-ray inspection. Therefore, a new technique of localization of short circuit part has been developed by using inverse analysis of the electromagnetic field around the battery. This method can inspect the short circuit part in the battery by estimating the electric current value at the arbitrary point from data of the magnetic field around the battery. Because the technique is nondestructive inspection and able to quantitatively evaluate, it can be expected to reduce the inspection cost and to improve the detection accuracy of short circuit in the battery. In this report, the effectiveness of this method was demonstrated through the analytical results in which the short circuit parts was identified from the magnetic flux density measured around the specimen that simulated the battery with short circuit by using the magnetic sensor.

Protection of Nonpermanent Faults on DC Overhead Lines in MMC-Based HVDC Systems

A high-voltage direct current system using modular multilevel converter (MMC-HVDC) is a potential candidate for grid integration of renewable energy over long distances. The dc-link fault is an issue MMC-HVDC must deal with, especially for the nonpermanent faults when using overhead lines. This paper proposed a protection scheme to implement fast fault clearance and automatic recovery for nonpermanent faults on dc lines. By employing double thyristor switches, the freewheeling effect of diodes is eliminated and the dc-link fault current is allowed to freely decay to zero. Then, the dc arc can be naturally extinguished and the insulation on the short-circuit point can be restored. The thyristor switches convert the dc-link fault into an ac short circuit of the ac grid through MMC arms. The ac short-circuit current can be cleared simply by turning off all thyristor switches. Since circuit breakers are not tripped during fault clearance, MMC can immediately and automatically rebuild the dc-link voltage and restart power transmission. Simulation results using PSCAD/EMTDC have verified the validity of the proposed protection scheme.

A Systematic Method of Interconnection Optimization for Dense-Array Concentrator Photovoltaic System

This paper presents a new systematic approach to analyze all possible array configurations in order to determine the most optimal dense-array configuration for concentrator photovoltaic (CPV) systems. The proposed method is fast, simple, reasonably accurate, and very useful as a preliminary study before constructing a dense-array CPV panel. Using measured flux distribution data, each CPV cells' voltage and current values at three critical points which are at short-circuit, open-circuit, and maximum power point are determined. From there, an algorithm groups the cells into basic modules. The next step is I-V curve prediction, to find the maximum output power of each array configuration. As a case study, twenty different I-V predictions are made for a prototype of nonimaging planar concentrator, and the array configuration that yields the highest output power is determined. The result is then verified by assembling and testing of an actual dense-array on the prototype. It was found that the I-V curve closely resembles simulated I-V prediction, and measured maximum output power varies by only 1.34%.

Study on Dynamic Response of Torsional Vibration of Turbo-Generator Unit Caused by Short Circuit Fault

When short circuit faults happen near power plant or generator terminal, severe transient torque shock will act on the shaft system, which seriously affects the safe and stable operation of the unit. Using the increment transfer matrix method, the dynamic responses of torsional vibrations are calculated in this work. Combined with the complex Morlet wavelet and time-frequency contour map, the time-frequency domain characters of dynamic torque are analyzed. The analyzed results show that the torque value caused by three phase short circuit fault is largest. The order of torque value from high to low is two phase short circuit to ground, two phase interphase short circuit and single phase short circuit. The electric distance between short circuit point and generator is more short, and the torsional vibration is more serious.

A Novel Compact Dual-band Slot Antenna

This paper introduces a compact dual-band slot antenna using spiral inductive loaded resonators. The radiating elements of the proposed antenna are composed of two balanced short circuited slot lines. To design a dual-band antenna, the microstrip feed line is somehow implemented to provide three short circuit points between the antenna and the feed lines. The antenna size is very compact, and can be integrated easily with other RF front-end circuits for dual-band applications. It is demonstrated that the proposed antenna can provide dual-band behavior with satisfactory radiation characteristics.

Modelling and analysis of switching overvoltages caused by short circuits in MV cables connected with overhead lines

In this paper, overvoltage transients are investigated and mitigated when a three-phase short-circuit occurs in cable lateral connected with medium voltage (MV) overhead line and fuse is operated. The transients are studied using EMTP-ATP simulation environment and the need of metal oxide varistors (MOVs) is investigated. The cable laterals consist of sub-laterals and their effect on reducing transients is also investigated. The surge arresters are installed at the junction of overhead line and cable and at far end of the cable near short-circuit point. The different mitigation methods are tested and optimal protection scheme to reduce overvoltages is proposed on the basis of surge arresters locations and sub-lateral connections.

Modified Medium-Voltage Arc-Flash Incident Energy Calculation Method

The IEEE Standard 1584-2002 provides a guide for conducting arc-flash hazard analyses for low- and medium-voltage systems. Users, however, need to be aware that the models in the guide were based on the measurements of arc incident energy under a specific set of test conditions combined with theoretical work. In the medium-voltage arc-flash analysis, the incident energy calculation, according to the guide, is a function of system voltage, gap between conductors, the distance from the possible arcing point to the worker, the bolted three-phase fault, and the arc clearing time from the source-side protecting device. However, the effect of fault current decaying is not considered in the current guide. According to an IEEE-recommended short-circuit calculation method, the fault contributions from generators and induction and synchronous motors would usually decay over the short-circuit period based on their short-circuit time constants and the excitation system. Therefore, the standard calculated incident energy from short-circuit point of view would be higher than the value if the effect of decaying current were considered. On the other hand, the arc clearing time according to the current guide is derived from the initial bolted three-fault current, which would result in a shorter arc clearing time. As a result, the standard calculated incident energy value from arc clearing point of view would be lower than the value if the effect of decaying current were considered. Therefore, there are two conflicting elements contained in the current guide, which may result in an inconclusive personal protective equipment requirement. This paper will present a modified incident energy calculation method based on the decaying three-phase fault current and also based on the arc clearing time derived from decaying three-phase fault current at the time of fault interruption. A sample calculation and a comparison of the results of the current method and the modified method are presented in this paper.

Z-Source-Converter-Based Energy-Recycling Zero-Voltage Electronic Loads

This paper proposes two high-efficiency energy-recycling zero-voltage electronic loads (ELs) based on a Z-source converter. ELs are a family of power converters which are used as variable impedance loads in several applications. Such applications include testing of photovoltaic (PV) cells, power converters, and power supplies or frequency control of stand-alone microgeneration. In PV-cell performance tests, the zero-voltage operation, near the short-circuit point of the PV cell's I- V curve, creates a challenge for EL design. The converter that is suitable for this application must have the ideal current source behavior because the challenge is to draw a specific constant current from the source under test even during the zero-voltage condition. The energy recycling principle increases the efficiency and allows the construction of high-power ELs. The proposed topologies are based on the Z-source converter and achieve the ideal current source behavior of draining an adjustable current even when the source voltage is zero. These topologies also provide power recycling for energy saving and for developing high-power ELs. The first configuration is based on the traditional Z-source converter, and the second one is based on the recently proposed quasi Z-source converter. Two prototypes were analyzed and built. Experimental results are provided to verify the principle of operation.

Electrochemical Kinetics and Safety of 2-Volt Class Li-Ion Battery System Using Lithium Titanium Oxide Anode

Microvoltammograms of a single particle of lithium titanium oxide (LTO, ) spinel were interpreted using a core-shell model in the spinel∕rock-salt two-phase transition process. Lithium insertion into the particle was controlled by the diffusion in LTO rock-salt structure outlayer. The quick charging was effectively enhanced by reducing the LTO particle size. Lithium extraction from the particle was significantly affected by the charge transfer on the LTO spinel outlayer rather than by the diffusion of lithium ions. The discharge speed during the internal short-circuit abuse test connecting with the LTO anode was 3 orders of magnitude slower than that with graphite anode. At the internal short-circuit point, transformation to the low electron-conductive LTO spinel phase will work to suppress the rapid extension of internal short circuit reaction. A class lithium-ion battery system using the LTO anode had a high output and input power density of for a pulse condition. Quick-charging performance showed 80% of the full capacity in . It was demonstrated that the class lithium-ion battery system exhibited excellent high power and quick charging with outstanding safety characteristics by using the LTO anode.

Electrochemical Kinetics and Perforamcne of 2-Volt Class Li-Ion Battery System with Safety, Quick-Charging, and High-Power

Microvoltammograms of a single particle of Li4/3Ti5/3O4 (LTO) spinel were interpreted using a core shell model in the spinel/rock-salt two-phase transition process. Lithium insertion into the particle was controlled by the diffusion in Li7/3Ti5/3O4 rock-salt structure out-layer. Lithium extraction from the particle was significantly affected by the charge transfer on the LTO spinel out-layer rather than by the diffusion of lithium ions. The discharge speed during the internal short circuit abuse test connecting with the LTO anode was three orders of magnitude slower than that with graphite anode. At the internal short circuit point, transformation to the low electron-conductive LTO spinel phase will work to suppress the rapid extension of internal short circuit reaction. It was demonstrated that the 2-volt class lithium-ion battery system using the LTO anode exhibited excellent high-power and quick-charging with outstanding safety characteristics by using the LTO anode.

Development and Test of 10.5 kV/1.5 kA HTS Fault Current Limiter

Superconducting Fault Current Limiter (SFCL) is an attractive appliance for modern electrical power system. A 10.5kV/1.5 kA three-phase HTS fault current limiter was developed by IEE, CAS. This improved rectifier-type SFCL with HTS coil of 6.25 mH is going on a demonstrated long-term reliable operation in a real 10.5 kV substation located in Hunan, China. In a three-phase-to-ground short circuit test of grid, the prospective fault current of 3.5 kA was limited to 635 A at the pre-setup short-circuit point successfully

Experimental Measurements of Fault Level For Sceco West, Kingdom of Saudi Arabia

The fault level represents the maximum short circuit current that a power system causes to flow to the point of short circuit. Due to change of network configuration, the fault level at any point of the power system network changes accordingly. It is not practical to apply full short circuit on the system in order to determine the fault level. This paper describes scheme for continuous measuring of the fault level at any point of the power system network. This scheme is composed of an antiparallel thyristor pair. The thyristor current, which is controlled by the firing angle, can be used to perform the on-line fault level measurement. Saudi Consolidated Electric Company (SCECO) West network has been simulated in the lab and the invented scheme has been applied to the network to measure the short circuit currents. The comparison between the measured and calculated short circuit currents shows results with high accuracy.

Analysis of the role of mobility-lifetime products in the performance of amorphous silicon p-i-n solar cells

An analytical model of an amorphous silicon p-i-n solar cell is presented to describe its photovoltaic behavior under short-circuit conditions. It has been developed from the analysis of numerical simulation results. These results reproduce the experimental illumination dependence of short-circuit resistance, which is the reciprocal slope of the I(V) curve at the short-circuit point. The recombination rate profiles show that recombination in the regions of charged defects near the p-i and i-n interfaces should not be overlooked. Based on the interpretation of the numerical solutions, we deduce analytical expressions for the recombination current and short-circuit resistance. These expressions are given as a function of an effective μτ product, which depends on the intensity of illumination. We also study the effect of surface recombination with simple expressions that describe its influence on current loss and short-circuit resistance.

ON-LINE FAULT LEVEL MEASUREMENT

ABSTRACT The fault level represents the maximum short circuit current that a power system causes to flow to the point of short circuit. Due to change of network configuration, the fault level at any point of the power system network changes accordingly It is not practical to apply full short circuit on the system in order to determine the fault level. This paper describes scheme for continuous measuring of the fault level at any point of the power system network. This scheme is composed of an antiparallel thyristor pair. The thyristor current, which is controlled by the firing angle, can be used to perform the on-line fault level measurement However, problems are associated with such measurement. These are mainly the complexity of the current waveform and its dependence on the system impedance. The effect of the system X/R ratio on the measurement is also analyzed.

Two-dimensional minority carrier flow in high-efficiency silicon solar cells at short-circuit, open-circuit and maximum power point operating conditions

Abstract Two-dimensional effects in bifacially-contacted n + pp + high-efficiency silicon solar cells arising from the spacing of the front metal fingers, the emitter sheet resistivity, and the shading of the front fingers are investigated with a state-of-the-art numerical semiconductor device simulator. The current flow pattern in the solar cells is examined for the three operating conditions short-circuit, open-circuit, and maximum power point, and the implications of the observed two-dimensional effects on the electrical output parameters are discussed.

Diagnosis of a large distributed series resistance in solar cells

It is well known that a moderate sheet resistance of the emitter layer of a solar cell can be modelled as a lumped series resistance. It has no influence on the open-circuit voltage and little influence on the short-circuit current. The lumped series resistance model enables the fill factor loss to be calculated. In the present paper it is shown that a large sheet resistance leads to current-voltage ( I–V) characteristics which are not of the lumped series resistance type but which instead display the presence of a lumped “light-dependent shunt resistance”. This qualitative diagnosis of an important distributed series resistance is completed using two quantitative diagnostic methods: the determination of the fill factor of the cell, and the measurement of the intersection of the V axis with the tangent to the I–V characteristic at the short-circuit point. The latter quantity, which we call the “short-circuit voltage”, turns out to be equal to about twice the open-circuit voltage, whereas the fill factor is in the range 30% – 38%.

Problems in design and operation of very large electrical generating systems

Problems in design and operation of very large electrical generating systems