Short-circuit Conditions Research Articles

Quantified Assessment of Internal Short-Circuit State for 18 650 Batteries Using an Extreme Learning Machine-Based Pseudo-Distributed Model

To facilitate the diagnosis of battery internal short circuit (ISC) using thermal behaviors, this work integrates several thermal effects, including the commonly ignored heat conduction hysteresis and radiation, to elaborate a lumped thermal model. Then, a pseudo-distributed model structure is built up to approximate the characteristics of real batteries by synthesizing multiple isomorphic electrical/thermal submodels with the extreme learning machine network. Besides, three kinds of configurable destructions are conducted to incur ISC consequences. From thermal and electrical model residuals, four ISC features are extracted and the multiclass relevance vector machine is utilized to assess ISC intensity, in which not only qualitative judgments are given but also quantitative confidences can be derived according to the posterior probabilities. Finally, experiments on 18650 Li-ion cells verify the reliability of the synthesized models and suggest that the diagnosis scheme can recognize ISC faults effectively with low grade and state misjudgment rates (14.59% and 3.13%, respectively).

The Effect of Micro-Inertia and Flexoelectricity on Love Wave Propagation in Layered Piezoelectric Structures.

The non-classical linear governing equations of strain gradient piezoelectricity with micro-inertia effect are used to investigate Love wave propagation in a layered piezoelectric structure. The influence of flexoelectricity and micro-inertia effect on the phase wave velocity in a thin homogeneous flexoelectric layer deposited on a piezoelectric substrate is investigated. The dispersion relation for Love waves is obtained. The phase velocity is numerically calculated and graphically illustrated for the electric open-circuit and short-circuit conditions and for distinct material properties of the layer and substrate. The influence of direct flexoelectricity, micro-inertia effect, as well as the layer thickness on Love wave propagation is studied individually. It is found that flexoelectricity increases the Love-wave phase velocity, while the micro-inertia effect reduces its value. These effects become more significant for Love waves with shorter wavelengths and small guiding layer thicknesses.

A di/dt Detection Circuit for DC Unidirectional Breaker Based on Inductor Transient Behaviour

In this paper, a di/dt detection circuit for DC breaker applications is proposed to provide faster short-circuit and overcurrent fault detection, where DC breakers are required to be designed for unidirectional fault current conditions, which is a challenge regarding DC microgrid applications due to some associated problems such as long periods of fault interruption, complex circuit structure, and low reliability. The proposal, which is based on measurement of di/dt, can detect fault current conditions for different distances from the point of failure, and is suitable to operation in both islanding and grid-connected conditions. The proposed circuit was studied theoretically and experimentally in steady state, as well as under load changes and short circuit conditions to ensure proper operation, making this solution a fast current fault detection solution, which is a significant advantage and requirement in DC microgrid applications.

Estimation of Short Circuit Capability of GaN HEMTs Using Transient Measurement

Wafer level transient voltage measurement (WLTVM) to estimate the short circuit capability of AlGaN/GaN HEMT devices is suggested. Two groups of samples with similar DC and switching properties but different short circuit capabilities of 4-7 and > 10μs were evaluated. The extracted junction temperature and the measured saturation/linear current under repeated short circuit stresses suggest that the short circuit failure is attributed to the degradation in the drift region. The WLTVM could measure the transient potential change along the drift region during short circuit condition. The sample with lower short-circuit survivability showed a faster propagation of the high field traveling from the gate to the drain. The time the high electric field reaches the drain coincides with the time of the short circuit failure. In addition to providing the insight into the short circuit failure mechanism, wafer-level method can provide a quick and non-destructive evaluation of the short circuit capability before packaging devices.

Analysis and Investigation of Thermal Runaway Propagation for a Mechanically Constrained Lithium-Ion Pouch Cell Module

In this paper, tests and analysis of thermal runaway propagation for commercial modules consisting of four 41 Ah Li-ion pouch cells are presented. Module samples were tested at 100% state-of-charge and mechanically constrained between two steel plates to provide thermal and mechanical contact between the parts. Voltage and temperature of each cell were monitored during the whole experiment. The triggering of the exothermal reactions was obtained by overheating one cell of the stack with a flat steel heater. In preliminary studies, the melting temperature of the separator was measured (from an extracted sample) with differential scanning calorimetry and thermogravimetric analysis techniques, revealing a tri-layers separator with two melting points (≈135 °C and ≈170 °C). The tests on module level revealed 8 distinct phases observed and analyzed in the respective temperature ranges, including smoking, venting, sparkling, and massive, short circuit condition. The triggering temperature of the cells resulted to be close to the melting temperature of the separator obtained in preliminary tests, confirming that the violent exothermal reactions of thermal runaway are caused by the internal separator failure. Postmortem inspections of the modules revealed the internal electrical failure path in one cell and the propagation of the internal short circuit in its active material volume, suggesting that the expansion of the electrolyte plays a role in the short circuit propagation at the single cell level. The complete thermal runaway propagation process was repeated on 5 modules and ended on average 60 s after the first thermal runaway triggered cell reached a top temperature of 1100 °C.

Bias-Dependent Dynamics of Degradation and Recovery in Perovskite Solar Cells

Degradation of perovskite solar cells (PSCs) is often found to be partially or fully reversible when the cells are allowed to recover in the dark. Unlike the dynamics of degradation, knowledge about the dynamics of PSC cell recovery is very limited. Here, we demonstrate that the PSC recovery strongly depends on the electrical bias conditions during the light-induced degradation and that it can be manipulated by applying an external electrical bias during the recovery phase. Investigation of the recovery dynamics allows us to analyze the degradation mechanisms in detail. More specifically, we aged a mixed-cation mixed-halide PSC with a n-i-p structure under illumination in open-circuit (OC) or short-circuit (SC) conditions, and periodically measured their characteristics during the recovery. PSCs aged in SC degrade faster and fully recover after the light is switched off, while the performance of the cells aged in OC does not recover but instead further decreases after the light is switched off (“drop-in-dark” effect). With the use of transient photoluminescence, secondary ion mass spectrometry, and drift-diffusion-based simulations, we hypothesize that extrinsic ion migration causes the drop-in-dark effect, by forming an electron extraction barrier at the metal oxide electron transport layer. The applied bias alleviates this effect. Our results are relevant for gaining a deeper understanding of the multiple degradation mechanisms present in perovskite solar cells, and for finding a practical way to assist their recovery.

Physical and mathematical modeling of transients in a synchronous generator utilizing synchronized phasor measurements

There have been quite a few attempts to compute synchronous generator parameters based on voltage and current synchrophasors taken under power system transients. However, we have not seen any publications with thorough analysis as to how soon the phasor measurement unit reacts to disturbance conditions, which components of the transient are filtered out and which are passed through, as well as what the total vector error is. The goal of this research is to determine all of these characteristics of a phasor measurement unit when playing back transient oscillograms for a stator short circuit obtained through mathematical modeling. The transient oscillograms have been derived via both a full Park-Gorev system of flux linkage equations as well as the MATLAB/Simulink Synchronous Machine block. Physical modeling was then conducted via a real-time digital simulator (RTDS) along with a dedicated phasor measurement unit ENIP-2 (PMU), and the stator current phasors were recorded. Our analysis has shown that both RTDS and ENIP-2 (PMU) almost entirely filter out the exponentially decaying DC component of the fault current while closely following the periodical signal envelope. The total vector error has been estimated to become below 1–2 % after around 0,02–0,03 s into the fault when selecting the “P” class filters according to IEEE C37.118. We have come to a conclusion that synchrophasor measurements under power system disturbances could be utilized for estimating the synchronous, transient, and subtransient generator parameters. The selected synchronous machine model in the form of flux linkage equations is correct, as the obtained transient oscillograms are exactly the same as those produced by Simulink. “P” class phasor measurements can be recommended for representing transients in the stator circuit of a synchronous generator. The results of this investigation are meant to be employed for synchronous machine parameter estimation based on phasors sourced from RTDS and, hopefully, from phasor measurement units installed at power plants.

Packaging of semiconductor thermoelectric energy generators with in-plane thermocouples and isolation cavities

With the advent of semiconductor foundry services, thermoelectric energy generator (TEG) by CMOS/BiCMOS process has been preferable for production yield, cost effectiveness, and device scalability. The thermocouples in semiconductor TEG often have thermal isolation cavity to reduce heat loss. Both die- and wafer-packaging are proposed in this work to seal the cavity, prevent moisture/dirt from contamination, and avoid short circuit condition in the thermocouples for TEG applications in wearable devices. For a TEG design by 3P6M (3 polysilicon layers and 6 metal layers) BiCMOS process, the die-level packaging by aluminum film of thickness 50 μm over the TEG is shown to be effective, though there is about 23 % temperature gradient loss by the packaging. The voltage factor is 18.22 V/cm2K, about 77 % of that before packaging. For a TEG design by 1P6M CMOS process, the wafer-level packaging by bonding two identical TEG device wafers is shown to have about 22 % loss in temperature gradient. Yet the TEG performance is increased significantly on the same footprint because of doubling area density, and hence doubling both the power factor and voltage factor. The power factor and voltage factor is 0.164 μW/cm2 K2 and 24.32 V/cm2K, respectively, on the TEG in series circuit after packaging.

Surfactant-Encapsulated Polyoxometalate Complex as a Cathode Interlayer for Nonfullerene Polymer Solar Cells

Surfactant-Encapsulated Polyoxometalate Complex as a Cathode Interlayer for Nonfullerene Polymer Solar Cells

Comparative Investigation of Fullerene PC71BM and Non-fullerene ITIC-Th Acceptors Blended With P3HT or PBDB-T Donor Polymers for PV Applications

Fundamentally, organic solar cells (OSCs) with a bulk-heterojunction active layer are made of at least two electronically dissimilar molecules, in which photoabsorption in one (donor) generates Frenkel excitons. The formation of free charge carriers emerge after exciton dissociation at the donor:acceptor interface. In the past decade, most of the progress in enhanced device performance has been steered by the rapid development of novel donor and acceptor materials and on device engineering. Among these donor materials, regioregular poly(3-hexylthiophene) (P3HT) produced better performance despite the mismatch of its absorption coefficient with the solar emission spectrum. Comparatively the donor PBDB-T exhibits an outstanding absorption coefficient with a deeper-lying highest occupied molecular orbital (HOMO) level. Previously most of the efficient acceptors were based on fullerene molecules characterized by limited photoabsorption and stability. In contrast, the recently developed non-fullerene OSCs have a tunable absorption spectrum and exhibit improved stability. In this work, we explore the fundamental sources of the differences in the device performance for different blend compositions made of fullerene derivative (PC71BM) and non-fullerene (ITIC-Th) when paired with the polymer donors P3HT and PBDB-T. The characteristic changes of the optical properties of these blends and their roles in device performance are also investigated. We also studied charge generation where PBDB-T:PC71BM showed the highest maximum exciton generation rate (Gmax) of 3.22 × 1028 s–1 while P3HT: ITIC-Th gave the lowest (0.96 × 1028 s–1). Also noted, PC71BM based counterparts gave better charge transfer capabilities as seen from the lower PL quenching and higher charge carrier dissociation plus collection probability P(E,T) derived from a plot of Jph/Jsat ratio under short-circuit conditions against the effective voltages.

Design of All-Fused-Ring Electron Acceptors with High Thermal, Chemical, and Photochemical Stability for Organic Photovoltaics

High-performance donor–acceptor electron acceptors containing 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN)-type terminals are labile toward photooxidation and basic conditions, and ...

An Intelligent Dual-Mode Control Strategy for Extending MPPT Operation Interval of DFIG

An intelligent dual-mode control strategy is proposed to extend the MPPT operation range of doubly-fed induction generator (DFIG) and improve the power generation efficiency under low wind speed in this article. By adjusting the strategy of the machine-side converter (MSC) and the necessary switchover, DFIG can automatically operate in two modes depending on the wind speed: the traditional DFIG mode and the DFIG stator short circuit (SSC) mode. In addition, aiming at the characteristics of short time, large impact, and long impact of mode switching process, this article focuses on the flexible mode switching control methods rarely mentioned in other studies, especially the specific process of bidirectional mode switching, MSC control strategy, and the selection of generator load. Finally, the hardware-in-the-loop (HIL) simulation results based on RT-lab show that the control strategy proposed in this article takes the advantages of the low cost of DFIG and the wide speed range of full-power generator (FPG), and achieves fast and flexible switching between the two modes.

Mechanical DC breaker for DC distribution network test method

DC circuit breaker has been a research hotspot in recent years. However, currently, DC circuit breakers are frequently used in the lab to perform breaking tests in the laboratory using a power frequency synthesis loop. The equivalence of the DC circuit breaker is to be discussed. This article aims to provide a test system design scheme that satisfies the technical requirements, that is, at a voltage level of 10kV, the system can provide a 2 kA rated current and a 20 kA short circuit current with a 6kA/ms rise rate to simulate an actual short circuit condition, and Based on this, a successful breaking of the mechanical DC breaker can be achieved. The key work of this paper is to simulate the establishment of the simulation model of the test circuit, as well as the selection of circuit parameters and the selection of components. This enables the shunt to meet the 20kA short-circuit current and the 2kA rated current. The model of DC circuit breaker was established by PSCAD. It has certain guiding significance and reference significance for the actual establishment of DC circuit breakers and test platforms in the laboratory.

Design of Vibration Frequency Method with Fine-Tuned Factor for Fault Detection of Three Phase Induction Motor

This research article focuses on industrial applications to demonstrate the characterization of current and vibration analysis to diagnose the induction motor drive problems. Generally, the induction motor faults are detected by monitoring the current and proposed fine-tuned vibration frequency method. The stator short circuit fault, broken rotor bar fault, air gap eccentricity, and bearing fault are the common faults that occur in an induction motor. The detection process of the proposed method is based on sidebands around the supply frequency in the stator current signal and vibration. Moreover, it is very challenging to diagnose the problem that occur due to the complex electromagnetic and mechanical characteristics of an induction motor with vibration measures. The design of an accurate model to measure vibration and stator current is analyzed in this research article. The proposed method is showing how efficiently the root cause of the problem can be diagnosed by using the combination of current and vibration monitoring method. The proposed model is developed for induction motor and its circuit environment in MATLAB is verified to perform an accurate detection and diagnosis of motor fault parameters. All stator faults are turned to turn fault; further, the rotor-broken bar and eccentricity are structured in each test. The output response (torque and stator current) is simulated by using a modified winding procedure (MWP) approach by tuning the winding geometrical parameter. The proposed model in MATLAB Simulink environment is highly symmetrical, which can easily detect the signal component in fault frequencies that occur due to a slight variation and improper motor installation. Finally, this research article compares the other existing methods with proposed method.

Performing Analysis of Current Transformer in Short Circuit and Open Circuit Conditions By ANSYS@Maxwell

Calculation of the design parameters of current transformers (CTs) is very complex due to their magnetic and thermal properties, complexity of their structure, different ferromagnetic properties of the materials and the nonlinearity of the B-H curve of the core material. The secondary output of these transformers is used for both measurement and protection circuits. Therefore, AT's accuracy must be very good and precise. In this study, the transformer is modeled as 2D using the Finite Element Method (FEM). ANSYS@Maxwell program, which realizes a solution based on finite element method, has been used in magnetic and thermal analysis of the current transformer. Analyzes of the transformer were carried out in 2D under open and short circuit conditions. From the results obtained from the analysis, the scattered electromagnetic flux distribution occurred in the core of the current transformer, which caused the secondary current of the CT to be erroneous. Therefore, it has been observed that unwanted operating conditions occur in the protection circuits..

Single Input Single Output Two Level Isolated Dc-Dc Converter With Secondary Side Phase Shifting For Solar Applications

The isolated dc–dc converters with primary-side phase shifting (PPS) provides severely narrow soft-switching range for main devices in the primary side leg of full bridge converter. The leakage inductance of the high frequency transformer should be large enough for providing the energy needed for soft switching operations and also the idling power loss due to circulating current in the converter legs under large phase-shift angle, which makes reduction of conversion efficiency and complicated in designing the parameters of transformer. Furthermore, the turn-off diode commutations in the output-side rectifier are performed by hard-switching mode. To overcome all these drawbacks, a secondary side phase shifting (SPS) technique has been developed for two-level isolated DC-DC converter. This scheme provides wider soft switching range and reduced power loss due to elimination of circulating current in the primary side of high frequency transformer. In addition, SPS control also provide no reverse recovery current in diodes and hence no power losses in the secondary rectifier circuit. The control switches operate under soft switching even under rated load and short circuit conditions.

A Novel Fault Diagnosis Technique of Interturn Short-Circuit Fault for SRM in Current Chopper Mode

The interturn short-circuit fault of stator winding is a common failure mode in switched reluctance motors (SRMs), which can severely harm the operation of the motor. In this article, a novel method for diagnosing the interturn short-circuit fault in the current chopping mode is proposed, which is suitable for online monitoring and protection of SRMs. The proposed method achieves a fast response and high sensitivity and can mitigate the interference of load conditions on detection reliability. Moreover, this method is based on phase currents, which does not require additional sensor or detection circuits. Meanwhile, the effects of interturn fault location in the stator winding on the motor flux and motor parameters are analyzed in detail through finite-element analysis, which is helpful to establish a reliable diagnostics technique for various fault conditions. Experimentations based on an 8/6 four-phase SRM with special windings designed to simulate interturn short circuit conditions are conducted, and the results have verified the effectiveness of the proposed method.

Lead-free tin perovskite solar cells

Summary The development of efficient and stable lead-free perovskite solar cells (PSCs) is crucial for addressing the concern of environmental pollution from the toxic element lead. In recent years, tin PSCs have emerged as a promising candidate for high-performance, eco-friendly photovoltaic technology with a high certified power conversion efficiency (PCE) of more than 11%, indicating a great potential for future applications. Here, we review the recent efficiency progress of tin PSCs based on the equivalent circuit model of solar cells. We then discuss approaches toward efficiency improvement from the device viewpoint, such as optimizing the band gap, increasing the light-harvesting efficiency and carrier diffusion length, surface passivation, and regulating the interface energy-level alignment. Finally, we point out the possibility of reaching 20% PCE for tin PSCs and issues regarding enlarging the cell size and realizing scalable production in the future. We expect that these perspectives will be helpful for accelerating the commercialization of tin PSCs.

Short circuit detection and driving control with no blanking time for high voltage high power insulated gate bipolar transistors

Insulated gate bipolar transistors (IGBT) short-circuit (SC) protection is one of the most important protection methods for IGBT converter equipment. The fast detection and protection response time could reduce the permanent damage of devices, and extend their use life cycle. At present, the collector emitter voltage vce desaturation method is widely used in the commercial IGBT drive circuit, which has blanking time of fault detection and protection. In this paper, an improved adaptive vce SC detection and protection is proposed to realize the blanking time adjustment under different SC conditions. By the determination of the di/dt characteristics of the current variation on the parasitic inductance between the power emitter and the Kelvin emitter of IGBT modules, the execution time of the two detection methods can be set. According to the switch process and the SC type, the corresponding logic processing will be carried out to realize the fast detection of different SC conditions. The circuit scheme without blanking time detection and protection is designed, and the circuit is modelled and simulated by Pspice. The IGBT driving circuit SC test without blanking time detection and soft turn-off protection has been carried out. Simulation and test results can verify the feasibility of the proposed circuit.

Discriminative common vector in sufficient data Case: A fault detection and classification application on photovoltaic arrays

In this study, the derivation of the Discriminative Common Vector (DCV) approach which is first introduced for a face recognition task in the insufficient data case, for the sufficient data case is obtained and it is applied for a photovoltaic (PV) panel fault detection and classification. Two experimental studies are performed including two different fault configurations. In the first experimental study, as the faulty conditions open-circuit, short-circuit, and partial shading conditions are taken and healthy condition is taken as reference. Thus, a four-class fault detection and classification scheme is constructed. In the second experimental study, the serial resistance degradation fault is considered. This fault detection and classification scheme includes four classes that are healthy and three different serial resistance degradation. The data used in the experimental studies are formed to be 1x3 dimensional vectors which include the current, voltage, and power values obtained from the simulations in the PSIM program. In all two experimental studies for each class, a discriminative common vector (DCV) which represents the common properties of that class, thus, having a high discriminative ability is obtained. As a contribution to the literature, the derivation of DCVA which has high discrimination ability for sufficient data case, and usage of it for PV panels fault detection and classification is proposed for the first time in this study. The proposed method's performance is evaluated with the performance of PCA method that is recently used for the fault detection and classification problem in PV panel systems in the literature. In the first experimental study, the proposed method's performance (99%) is obtained significantly higher than the performance of the PCA method (95%). And in the second experimental study, while PCA can only detect the faulty condition but cannot classify the serial resistance degradation, the proposed method can both detect and classify with 99% accuracy the PV panel serial resistance degradation.