Characteristics Of Module Research Articles

An I–V characteristic reconstruction-based partial shading diagnosis and quantitative evaluation for photovoltaic strings

The partial shading condition (PSC) is the most common abnormality occurred in photovoltaic (PV) systems. Accurate quantitative evaluation of the shaded area and the severity of the shading is of potential importance in optimizing the maintenance strategy for PV systems. In this paper, we propose a PSC diagnosis and quantitative evaluation method by analyzing the measured string current–voltage (I–V) characteristic obtained from the PV inverter with the I–V scanning function, which includes pre-diagnosis of the system abnormality based on the operational power deviation, the diagnosis of PSCs based on the derivatives characteristics of the PV string, and the quantitative evaluation based on the I–V characteristic reconstruction. The quantitative evaluation of PSCs is the main focus in this paper, where the I–V characteristics of the unshaded PV modules in the partially shaded PV string are reconstructed according to different mismatch levels, respectively. The number of shaded PV modules and the corresponding severity of the partial shadings are estimated according to the reconstructed I–V characteristics. The simulation and experimental results verify that both the proposed diagnosis and quantitative evaluation method is effective with decent accuracy, especially for severe mismatch conditions. Experimental results show that the maximal mean absolute error of the quantified shaded area and quantified shaded rate are approximately 1.4446 units of 1/3 PV modules and 0.026, respectively.

A simplified mathematical modeling approach for thermal runaway of Li(Ni0.8Co0.1Mn0.1)O2 pouch cells based on thermal runaway experimental data

Currently, the numerical modeling methods used to characterize the thermal runaway and propagation mechanisms in NCM811 pouch batteries still face numerous challenges. This is primarily due to the uncertainties in thermal runaway reactions and the immense computational demands encountered when modeling begins at the granular level of the cell. To address this issue, this study designed a series of experiments for an NCM811 pouch battery. By employing experimental data, reasonable assumptions were made regarding the combined effects of solid-state thermal conduction, electrochemical heating, and fluid-solid heat transfer through gas jet streams. A simplified thermal runaway mathematical modeling method based on experimental data was proposed, effectively tackling the problem. This framework was then applied to thermal runaway experiments on a single NCM811 battery used in this study, providing essential input parameters for three-dimensional numerical modeling of modules composed of multiple batteries in multiphysics simulation software. The simulation results derived from the proposed method were in good agreement with experimental data. This study can characterize the thermal runaway and thermal propagation characteristics of battery modules using single-cell thermal runaway experiments. Moreover, the proposed modeling approach not only predicted the experimental outcomes of the NCM811 pouch battery with reasonable accuracy but also provided smoother data, elucidating the highly fluctuating trends observed in experimental data. This method also offers guidance for designing fire prevention and smoke exhaust systems for battery packs. This study presents a novel approach for the mathematical modeling of thermal runaway and thermal propagation in battery modules using NCM811 pouch batteries, contributing to the ongoing development of lithium-ion battery module design.

Characterization of Event Related Desynchronization in Chronic Stroke Using Motor Imagery Based Brain Computer Interface for Upper Limb Rehabilitation.

Motor imagery-based brain-computer interface (MI-BCI) is a promising novel mode of stroke rehabilitation. The current study aims to investigate the feasibility of MI-BCI in upper limb rehabilitation of chronic stroke survivors and also to study the early event-related desynchronization after MI-BCI intervention. Changes in the characteristics of sensorimotor rhythm modulations in response to a short brain-computer interface (BCI) intervention for upper limb rehabilitation of stroke-disabled hand and normal hand were examined. The participants were trained to modulate their brain rhythms through motor imagery or execution during calibration, and they played a virtual marble game during the feedback session, where the movement of the marble was controlled by their sensorimotor rhythm. Ipsilesional and contralesional activities were observed in the brain during the upper limb rehabilitation using BCI intervention. All the participants were able to successfully control the position of the virtual marble using their sensorimotor rhythm. The preliminary results support the feasibility of BCI in upper limb rehabilitation and unveil the capability of MI-BCI as a promising medical intervention. This study provides a strong platform for clinicians to build upon new strategies for stroke rehabilitation by integrating MI-BCI with various therapeutic options to induce neural plasticity and recovery.

The Mechanism of Short-Circuit Oscillations in Automotive-Grade Multi-Chip Parallel Power Modules and an Effective Mitigation Approach.

This paper presents an in-depth analysis of the oscillation phenomenon occurring in multi-chip parallel automotive-grade power modules under short-circuit conditions and investigates three suppression methods. We tested and analyzed two commercial automotive-grade power modules, one containing two chips and the other containing a single chip, and found that short-circuit gate oscillations were more likely to occur in multi-chip parallel packaged modules than in single-chip packaged modules. Through experimental and simulation analyses, we observed that gate oscillations were mainly caused by the interaction between internal parasitic parameters of the module and the external drive circuit, and we found that high drive resistance and low common emitter inductance between parallel chips could effectively suppress gate voltage oscillations. We also analyzed the two mainstream suppression schemes, increasing the drive gate resistance and placing the drive capacitors in parallel. Unfortunately, we found that these suppression schemes were not ideal solutions because both schemes changed the switching characteristics of the power module. As an alternative, we propose a simple and effective solution that involves adding parallel connections between the parallel chips. Simulation calculations showed that this optimized method reduced the emitter inductance between parallel chips in the upper bridge arm by about 30% and in the lower bridge arm by 35%. Through short-circuit experiments conducted at different DC bus voltages, it has been verified that the new optimized solution effectively resolves gate oscillation issues without affecting the switching characteristics of the power module.

An experimental study on thermal runaway propagation over cyclic aging lithium-ion battery modules with different electrical connections

This paper investigates the thermal runaway propagation characteristics of cyclic aging battery modules connected in series, parallel, and series-parallel configurations. Additionally, a comparative analysis of the thermal runaway characteristics among the three battery module configurations is performed. In this experiment, voltage, mass, and other parameters of cells are measured. The temperature response reveals that: when comparing the three battery module configurations, the parallel module has the highest maximum temperature of thermal runaway at 720 °C, followed by the series and series-parallel combined configurations at 683 °C and 669 °C, respectively. The parallel module also exhibits the fastest propagation rate of thermal runaway, which is further intensified by cyclic aging. Regarding the voltage response: the series configuration has five stages of voltage variation during thermal runaway, while the parallel configuration has two stages, and the series-parallel combined configuration has three stages. Cyclic aging accelerates the voltage decline during thermal runaway for all three battery module types. In terms of mass response: the 2P2S configuration experiences the highest mass loss of 55.7 g, followed by the parallel (40.8 g) and series (34.7 g) configurations. Preliminary heat transfer analysis shows that: the average heat transfer during thermal runaway is highest for the 2P2S configuration (20,161 J), followed by the 4S (18,913 J) and 4P (18,773 J) configurations. Cyclic aging reduces the overall heat transfer. Electrical connections have minimal impact on heat transfer within the battery modules. Specifically, in the 4S, 4P, and 2P2S configurations, the heat transfer attributed to electrical connections accounts for only 1.2 %, 0.4 %, and 7.3 % respectively, of the overall heat conduction through the battery shell.

Modified Rime-Ice Growth Optimizer with Polynomial Differential Learning Operator for Single- and Double-Diode PV Parameter Estimation Problem

A recent optimization algorithm, the Rime Optimization Algorithm (RIME), was developed to efficiently utilize the physical phenomenon of rime-ice growth. It simulates the hard-rime and soft-rime processes, constructing the mechanisms of hard-rime puncture and soft-rime search. In this study, an enhanced version, termed Modified RIME (MRIME), is introduced, integrating a Polynomial Differential Learning Operator (PDLO). The incorporation of PDLO introduces non-linearities to the RIME algorithm, enhancing its adaptability, convergence speed, and global search capability compared to the conventional RIME approach. The proposed MRIME algorithm is designed to identify photovoltaic (PV) module characteristics by considering diverse equivalent circuits, including the One-Diode Model (ONE-DM) and Two-Diode Model TWO-DM, to determine the unspecified parameters of the PV. The MRIME approach is compared to the conventional RIME method using two commercial PV modules, namely the STM6-40/36 module and R.T.C. France cell. The simulation results are juxtaposed with those from contemporary algorithms based on published research. The outcomes related to recent algorithms are also compared with those of the MRIME algorithm in relation to various existing studies. The simulation results indicate that the MRIME algorithm demonstrates substantial improvement rates for the STM6-40/36 module and R.T.C. France cell, achieving 1.16% and 18.45% improvement for the ONE-DM, respectively. For the TWO-DM, it shows significant improvement rates for the two modules, reaching 1.14% and 50.42%, respectively. The MRIME algorithm, in comparison to previously published results, establishes substantial superiority and robustness.

The mechanism of EP/SiC coating modulated DC flashover characteristics of epoxy composites in SF6/N2 mixtures

Surface flashover is an inevitable insulation issue for basin-type insulators in gas-insulated switchgears/lines, which significantly challenges the reliability of the electrical power systems. Previous studies have indicated that polymer/semiconductor-filler composite coatings effectively improve the insulation properties; however, the influence mechanism of the coating materials on flashover has not been demonstrated from a molecular perspective. In this work, epoxy/silicon-carbide (EP/SiC) composites were coated onto an EP substrate. The energy-level structure, surface trap, surface charging, and DC flashover voltage in SF6/N2 were calculated and characterized, and the process by which the tailored molecular energy level influences surface charge transport and flashover characteristics was elucidated. The incorporating of SiC particles reduced the width of the bandgap and introduced shallow traps, which improved carrier mobility and surface conductivity. Quantitative analysis of charge transport indicated that the improved carrier mobility and reduced surface trap level accelerated the surface charge dissipation. This reduced the tangential electrical field distortion and surface charge density and further impeded gas ionization. When the SiC concentration was 15 wt%, the flashover performance improved by 20.88%. This study describes the mechanism by which the EP/SiC coating regulates the surface charge distribution to improve the surface flashover performance by establishing a relationship among the microscopic molecular energy-level structures, mesoscopic charge transport, and macroscopic discharge phenomena.

Enhanced Heat Transfer in Thermoelectric Generator Heat Exchanger for Sustainable Cold Chain Logistics: Entropy and Exergy Analysis

This study investigates the application of thermoelectric power generation devices in conjunction with cold chain logistics transport vehicles, focusing on their efficiency and performance. Our experimental results highlight the impact of thermoelectric module characteristics, such as thermal conductivity and the filling thickness of copper foam, on the energy utilization efficiency of the system. The specific experimental setup involved a simulated logistics cold chain transport vehicle exhaust waste heat recovery thermoelectric power generation system, consisting of a high-temperature exhaust heat exchanger channel and two side cooling water tanks. Thermoelectric modules (TEMs) were installed between the heat exchanger and the water tanks to use the temperature difference and convert heat energy into electrical energy. The analysis demonstrates that using high-performance thermoelectric modules with a lower thermal conductivity results in better utilization of the temperature difference for power generation. Additionally, the insertion of porous metal copper foam within the heat exchanger channel enhances convective heat transfer, leading to an improved performance. Furthermore, the study examines the concepts of exergy and entropy generation, providing insights into the system energy conversion processes and efficiency. Overall, this research offers valuable insights for optimizing the design and operation of thermoelectric generators in cold chain logistics transport vehicles to enhance energy utilization and sustainability.

Prospective secondary teachers’ noticing of students’ thinking about the limit concept: pathways of development

Research has shown that there is a need to examine prospective teachers’ development trajectories related to noticing expertise. An important content in the Spanish high school curriculum (16–18 years old) is the limit concept. Given the importance of this concept in the curriculum and the difficulties some prospective teachers have, developing their noticing of students’ mathematical thinking of this concept in teacher education programs is crucial to achieve high school student mathematics achievement. This study examines how prospective secondary school mathematics teachers (PTs) notice students’ mathematical thinking about the limit concept as they participated in a teaching module. PTs had to anticipate and interpret students’ mathematical understanding and make instructional decisions to support students’ conceptual progression using information about high school students’ understanding of the limit concept. We examined PTs changes related to how they anticipated, interpreted and made instructional decisions during the teaching module. We identified a change in how PTs conceived the understanding of the dynamic limit concept: from all-or-nothing dichotomy to progression; and a change in the instructional decisions they made: from decisions focused on changing the type of discontinuity to conceptual decisions. These changes allow us to characterise development noticing pathways. Our findings also help to identify the teaching module characteristics that support the development of PTs noticing.

Motor learning- and consolidation-related resting state fast and slow brain dynamics across wake and sleep

Motor skills dynamically evolve during practice and after training. Using magnetoencephalography, we investigated the neural dynamics underpinning motor learning and its consolidation in relation to sleep during resting-state periods after the end of learning (boost window, within 30 min) and at delayed time scales (silent 4 h and next day 24 h windows) with intermediate daytime sleep or wakefulness. Resting-state neural dynamics were investigated at fast (sub-second) and slower (supra-second) timescales using Hidden Markov modelling (HMM) and functional connectivity (FC), respectively, and their relationship to motor performance. HMM results show that fast dynamic activities in a Temporal/Sensorimotor state network predict individual motor performance, suggesting a trait-like association between rapidly recurrent neural patterns and motor behaviour. Short, post-training task re-exposure modulated neural network characteristics during the boost but not the silent window. Re-exposure-related induction effects were observed on the next day, to a lesser extent than during the boost window. Daytime naps did not modulate memory consolidation at the behavioural and neural levels. These results emphasise the critical role of the transient boost window in motor learning and memory consolidation and provide further insights into the relationship between the multiscale neural dynamics of brain networks, motor learning, and consolidation.

The Mechanism of the Semi-Transparent Coverings Affecting the Power Generation Capacity of the Photovoltaic Module and Array

Shading on photovoltaic (PV) modules due to shadows, covering, dust, etc., usually characterized as semi-transparent, will significantly affect the power generation capacity. No systematic study has considered the impact of semi-transparent coverings on the power generation capacity of PV modules. This paper covers a single cell in the PV module using a covering with a transmittance of 18.55% and systematically investigates its impact on the power generation capacity. The open-circuit voltage (Voc) of the PV module is nearly unaffected by semi-transparent coverings because the covered cell can be considered as working at a lower irradiance and thus can output a voltage close to that of the uncovered cell. The short-circuit current (Isc) is significantly affected by coverings because it is co-contributed by the photocurrent (evaluated based on the covering ratio R and transmittance) and the reverse bias current ΔIsc (the covered cell is in a reverse bias state). The ΔIsc increases with R because more charge accumulates at the bi-ends of the covered cell; but, it decreases at full covering, which implies that in a partially covered case the uncovered part contributes more to ΔIsc than the covered part. The fill factor (FF) of the PV module first increases and then decreases with R, as the equivalent resistance of the covered cell increases rapidly with R, which replaces the wire resistance in dominating the series resistance of the PV module when R > 0.6. This work is of great theoretical significance in analyzing the output characteristics of PV modules under real conditions.

Enhancement in thermal and electrical characteristics of solar photovoltaic module through a direct contact water jacketed cooling system

Renewable energy resources are vital for addressing the universal concerns of air quality, energy security, and sustainable development. Solar energy has several benefits over other popular renewable energy sources, such as its accessibility and increased predictability. The device used for conversion of solar energy to electrical energy is known as photovoltaic panel, which is highly sensitive to the temperature. A significant reduction in efficiency is observed with an increment in temperature hence cooling of photovoltaic panel is highly desirable. Among the different cooling techniques, water cooling is attractive and widely used due to its good thermal properties and availability. Generally, panel cooling through water circulation in tubing is explored in past, however, these tubing structures are having some limitations such as heat transfer barrier, limited surface area, leakage issues, clogging and cost of material. These issues can be partially resolved by using direct contact water jacket cooling system. Therefore, the present study focuses on in enhancing the thermal and electrical characteristics of the solar photovoltaic module through a direct contact water jacketed cooling system. Initially, a 3D numerical model is developed and the outcome of the numerical model is compared with the experimental work. The results obtained are found in good agreement for solar cell temperature and water outlet temperature. The solar panel performance is investigated with different flow rates such as 0.01, 0.05, 0.1 and 1 cm/s. The direct contact water jacketed cooling system offers simplicity, light weight and cost effectiveness and is found promising over the indirect system. Temperature reduction up to 20 °C is observed over uncooled PV panel whereas enhancement in electrical efficiency up to 9.6 % is observed. The cooled PV solar cell maintain 40.2% low temperature compare to uncooled solar cell temperature.

Adaptive Particle Swarm Optimization of a Photovoltaic System under Partial Shading

The solar photovoltaic (PV) energy is the most prevalent and popular source of energy. But the PV output characteristics are mainly depending on temperature and irradiance and are nonlinear in nature. Therefore, PV array characteristics greatly vary with change in the atmospheric condition. Under partial shading condition (PSC), PV modules will not receive the same level of incident solar irradiance throughout the system due to some obstructions such as: dust, cloudy weather, shadows of nearby objects: buildings, trees, mountains, birds etc… which causes mismatch in PV module characteristics of the PV array and losses arise in the entire PV configuration. Consequently, power extraction from the PV system is reduced and the PSC on the PV array can be minimized by the proper selection of PV configurations, physical relocation of the PV modules and maximum power point tracking techniques (MPPT) to overcome this problem. The present article studies and compares the MPPT based on the Adaptive particle swarm optimization (APSO) algorithm under partial and completely shaded. The perturbation and observation (P&O) method is widely due to its simplicity and easy implementation but the Intelligent and hybrid control such as: fuzzy logic control (FLC) and adaptive neural fuzzy inference system (ANFIS) can track the MPP with better efficiency but in a long time compared to conventional approaches. In addition, these methods need big data for good results and the data problem is regulated with the evolutionary algorithms and searching the duty cycle (d) in a shorter time than FLC and ANFIS. The principle of PSO, grey wolf optimization (GWO), and APSO techniques is the search for a global solution, and it have good behaviour under PSC but APSO can be classified as best solution between the studied approaches. The simulation results, which are presented in MATLAB/Simulink software, show the effectiveness of the proposed APSO technique.

Thermal runaway propagation behavior and gas production characteristics of NCM622 battery modules at different state of charge

Due to the complex thermal runaway propagation behavior of lithium-ion battery modules and the generation of a substantial amount of combustible mixed gases during the process, their safety performance is compromised, hindering their large-scale application in the fields of energy storage and automotive industries. Therefore, in this paper, the thermal runaway propagation behavior and gas production characteristics of Li (Ni0.6Co0.2Mn0.2) O2 battery modules with different state of charge were investigated in closed space. The results show that no thermal runaway occurred in the battery module when the state of charge was below 25% in closed space. With the decrease of the state of charge, both the internal thermal propagation speed and the surface temperature of the lithium-ion battery were reduced. The total gas production volume from 17.48 mol to 6.17 mol when the state of charge was reduced from 100% to 50%. The main gases produced during thermal runaway were CO2, CO, H2, CH4, and C2H4. With the decrease of the state of charge, the content of CO2 increased, the content of C2H4 and CO decreased, and the content of H2 and CH4 remained unchanged with the state of charge. The results contribute to safety measures for preventing thermal runaway accidents in lithium-ion batteries, offering guidance for the secure design of lithium-ion battery packs, and thus enhancing the overall safety of lithium-ion batteries.

Diverse Plantarflexor Module Characteristics Influence Immediate Effects of Plastic Ankle-Foot Orthosis on Gait Performance in Patients With Stroke: A Cross-sectional Study

ObjectiveTo investigate the immediate effects of plastic ankle-foot orthosis (AFO) on locomotor performance in patients with stroke and determine how such effects might undergo alteration when distinct plantarflexor (PF) module subtypes are considered. DesignCross-sectional study. SettingTwo university hospitals. ParticipantsFifty-two patients with stroke and 21 of those without stroke (N=73). InterventionsNot applicable. Main Outcome MeasuresMotor modules were identified through non-negative matrix factorization, and participants were classified into 3 groups: independent-normal-timing, independent-altered-timing, and merged PF modules. To assess the effects of the AFO, gait measurements reflecting locomotor performance were obtained with and without the presence of the plastic AFO for each group. ResultsThe independent-altered-timing group had increased paretic propulsion, greater non-paretic step length, and faster walking speed after the administration of the plastic AFO; however, these significant changes were not observed in the independent-normal-timing and merged PF module groups. Notably, patients in the independent-normal-timing and merged PF module groups exhibited longer paretic stance times. ConclusionThis study suggests that the immediate effects of plastic AFO depend on the PF module subtype. These findings can potentially guide clinical decision-making regarding AFO selection for stroke rehabilitation in patients with diverse gait control characteristics.

Thermal Performance Analysis of a Prismatic Lithium-Ion Battery Module under Overheating Conditions

Thermal runaway (TR) of lithium-ion batteries has always been a topic of concern, and the safety of batteries is closely related to the operating temperature. An overheated battery can significantly impact the surrounding batteries, increasing the risk of fire and explosion. To improve the safety of battery modules and prevent TR, we focus on the characteristics of temperature distribution and thermal spread of battery modules under overheating conditions. The heat transfer characteristics of battery modules under different battery thermal management systems (BTMSs) are assessed. In addition, the effects of abnormal heat generation rate, abnormal heat generation location, and ambient temperature on the temperature distribution and thermal spread of battery modules are also studied. The results indicate that the BTMS consisting of flat heat pipes (FHPs) and bottom and side liquid cooling plates can effectively suppress thermal spread and improve the safety of the battery module.

Thermal runaway propagation characteristics of lithium-ion battery modules in a restricted channel with different longitudinal wind velocities

Thermal runaway (TR) and its propagation (TRP) in lithium-ion batteries (LIBs) present safety challenges, especially in confined spaces where wind speed's impact on TRP remains poorly understood. This study investigates the influence of longitudinal wind speed on TRP in LIBs within restricted channels. Results reveal a decreased incidence of TR with higher wind speeds. At 0 m/s, all cells in the two types of modules sequentially trigger TR, while speeds above 4 m/s prevent TR in any cells. TR onset temperature decreases, and onset time increases with wind speed. In the four-cell module, as wind speed rises from 0 m/s to 3 m/s, the TR onset for cell #1 increases from approximately 355 s to about 786 s. Dimensionless maximum remaining heat and dimensionless TR rate display a negative linear relationship with dimensionless wind speed. Dimensionless maximum remaining heat and TR rate exhibit a negative linear relationship with dimensionless wind speed. Additionally, the dimensionless TRP rate follows a power function with dimensionless wind speed. Energy flow distribution at different wind speeds is calculated, showing effective heat dissipation by longitudinal wind, delaying or preventing TRP. This research advances TRP theory and proposes a novel approach to mitigate TRP in LIBs.

A Simple Approach for Module Temperature and Power Prediction

In this work a mathematical approach to calculate solar panel temperature based on measured irradiance, temperature and wind speed is applied. With the calculated module temperature, the electrical solar module characteristics is determined. A program developed in MatLab App Designer allows to import measurement data from a weather station and calculates the module temperature based on the mathematical NOCT and stationary approach with a time step between the measurements of 5 minutes. Three commercially available solar panels with different cell and interconnection technologies are used for the verification of the established models. The results show a strong correlation between the measured and by the stationary model predicted module temperature with a coefficient of determination R2 close to 1 and a root mean square deviation (RMSE) of ≤ 2.5 K for a time period of three months. Based on the predicted temperature, measured irradiance in module plane and specific module information the program models the electrical data as time series in 5-minute steps. Predicted to measured power for a time period of three months shows a linear correlation with an R2 of 0.99 and a mean absolute error (MAE) of 3.5, 2.7 and 4.8 for module ID 1, 2 and 3. The calculated energy (exemplarily for module ID 2) based on the measured, calculated by the NOCT and stationary model for this time period is 118.4 kWh, resp. 116.7 kWh and 117.8 kWh. This is equivalent to an uncertainty of 1.4% for the NOCT and 0.5% for the stationary model.

Power Cycling Reliability with Temperature Deviation of Pressureless Silver Sintered Joint for Silicon Carbide Power Module

SiC devices can enhance power conversion in electric vehicles. However, traditional soldering techniques are limited by their low melting temperatures. Therefore, we used pressureless Ag sintering to assemble a 1200 V/200 A SiC metal-oxide-semiconductor field-effect transistor power module and compared the long-term reliability, electrical properties, and driving performance of the module with those of a similar module assembled using the solder Sn-3.0Ag-0.5Cu (SAC305). To assess sinter joint reliability, we performed power cycling tests over two temperature ranges, 50–150°C and 50–175°C, for 15,000 cycles. Subsequently, we compared the breakdown voltage (BVDSS) and drain-source on-resistance (RDS(ON)) of the SiC power modules and performed cross-sectional analyses of the device bonding interfaces. No difference in BVDSS was found between the Ag-sintered and SAC305-soldered joints. However, the RDS(ON) exhibited minimal variation for the Ag-sintered module but significantly varied for the SAC305-soldered module, suggesting that the former better maintained its characteristics. Furthermore, the electrical characteristics of the SAC305-soldered module underwent more significant alterations with increasing temperature change during power cycling, indicating that cracks propagated throughout the SAC305 soldered joint over time. Therefore, Ag sintering was quantitatively validated as the superior die attachment technology compared to soldering for long-term reliability.

Research on performance ratio composition and standard energy efficiency ratio correction method of photovoltaic power station

The performance ratio (PR) of the system is used to quantify the power generation efficiency of the photovoltaic power generation system. The size of the index is affected by many factors. After the environmental impact is compensated, the standard energy efficiency ratio (PRstc) of the system is obtained. PRstc is an important index for evaluating the power generation efficiency of photovoltaic power stations. Improving the accuracy of PRstc is conducive to improving the state evaluation and analysis capabilities of power stations, providing a theoretical basis for comparative analysis of photovoltaic power stations in different regions, and improving the scientific operation and maintenance of power stations. The PRstc calculation method of the industry standard NB / T 10394-2020 does not consider the influence of the change of the power temperature coefficient of the component and the weak light response of the photovoltaic cell, which ultimately leads to the calculation result less than the actual value. In order to reduce the error in the calculation of PRstc, the mathematical relationship between PR and power loss of photovoltaic power station is discussed. The calculation method of power loss caused by the change of environmental factors is proposed, and the PRstc is calculated by using the variation. Finally, the PRstc is calculated according to the actual operation data of photovoltaic power station, and compared with the calculation method of industry standard NB / T 10394-2020. The results show that when the total irradiation dose is high, the difference between the two PRstc values is less than 2 %. When the total irradiation is low, the calculation result is larger than that of the standard method, and the difference between the two increases with the decrease of the total irradiation. Due to the consideration of the change of power generation caused by the characteristics of photovoltaic modules, the error caused by the change of power temperature coefficient and weak light response of modules is reduced, which is more advantageous than the calculation method of industry standard.