Tamás Kerekes

Tamás Kerekes

Aalborg Universitet

H-index: 42

Europe-Denmark

About Tamás Kerekes

Tamás Kerekes, With an exceptional h-index of 42 and a recent h-index of 31 (since 2020), a distinguished researcher at Aalborg Universitet, specializes in the field of power electronics, grid connection, renewable energy.

His recent articles reflect a diverse array of research interests and contributions to the field:

Lithium-Ion Supercapacitors and Batteries for Off-Grid PV Applications: Lifetime and Sizing

Dual-level design for cost-effective sizing and power management of hybrid energy storage in photovoltaic systems

An adaptive power smoothing approach based on artificial potential field for PV plant with hybrid energy storage system

A Control-Oriented Voltage Tracking Design for Grid-Forming Based Modular Multilevel Converter

Robust PLL-Based Grid Synchronization and Frequency Monitoring

Small Signal Model of Modular Multilevel Converter with Power Synchronization Control

Capacitor Voltage Feedforward-based Voltage Loop Control for Grid-forming Modular Multilevel Converters Under Wide-range of Grid Strength

Interleaved Half-Bridge Submodules with Sensorless Leg Current Balancing in Modular Multilevel Converters

Tamás Kerekes Information

University

Aalborg Universitet

Position

___

Citations(all)

9017

Citations(since 2020)

4128

Cited By

6565

hIndex(all)

42

hIndex(since 2020)

31

i10Index(all)

93

i10Index(since 2020)

70

Email

University Profile Page

Aalborg Universitet

Tamás Kerekes Skills & Research Interests

power electronics

grid connection

renewable energy

Top articles of Tamás Kerekes

Lithium-Ion Supercapacitors and Batteries for Off-Grid PV Applications: Lifetime and Sizing

Authors

Tarek Ibrahim,Tamas Kerekes,Dezso Sera,Abderezak Lashab,Daniel-Ioan Stroe

Journal

Batteries

Published Date

2024/1/23

The intermittent nature of power generation from photovoltaics (PV) requires reliable energy storage solutions. Using the storage system outdoors exposes it to variable temperatures, affecting both its storage capacity and lifespan. Utilizing and optimizing energy storage considering climatic variations and new storage technologies is still a research gap. Therefore, this paper presents a modified sizing algorithm based on the Golden Section Search method, aimed at optimizing the number of cells in an energy storage unit, with a specific focus on the unique conditions of Denmark. The considered energy storage solutions are Lithium-ion capacitors (LiCs) and Lithium-ion batteries (LiBs), which are tested under different temperatures and C-rates rates. The algorithm aims to maximize the number of autonomy cycles—defined as periods during which the system operates independently of the grid, marked by intervals between two consecutive 0% State of Charge (SoC) occurrences. Testing scenarios include dynamic temperature and dynamic load, constant temperature at 25 °C, and constant load, considering irradiation and temperature effects and cell capacity fading over a decade. A comparative analysis reveals that, on average, the LiC storage is sized at 70–80% of the LiB storage across various scenarios. Notably, under a constant-temperature scenario, the degradation rate accelerates, particularly for LiBs. By leveraging the modified Golden Section Search algorithm, this study provides an efficient approach to the sizing problem, optimizing the number of cells and thus offering a potential solution for energy storage in off-grid PV systems.

Dual-level design for cost-effective sizing and power management of hybrid energy storage in photovoltaic systems

Authors

Xiangqiang Wu,Zhongting Tang,Daniel-Ioan Stroe,Tamas Kerekes

Journal

Green Energy and Intelligent Transportation

Published Date

2024/3/7

Integration of hybrid energy storage systems (HESS) into photovoltaic (PV) applications has been a hot topic due to their versatility. However, the proper allocation and power management schemes of HESS are challenges under diverse mission profiles. In this paper, a cost-effectiveness-oriented two-level scheme is proposed as a guideline for the PV-HESS system (i.e., PV, Li-ion battery and supercapacitor), to size the system configuration and extend battery lifespan while considering the power ramp-rate constraint. On the first level, a sizing methodology is proposed to balance the self-sufficiency and the energy throughput between the PV system and the grid to achieve the most cost-effectiveness. On the second level, an improved adaptive ramp-rate control strategy is implemented that dynamically distributes the power between the battery and supercapacitor to reduce the battery cycles. The case study presents …

An adaptive power smoothing approach based on artificial potential field for PV plant with hybrid energy storage system

Authors

Xiangqiang Wu,Yue Wu,Zhongting Tang,Tamas Kerekes

Journal

Solar Energy

Published Date

2024/3/1

The increasing quantity of PV installation has brought great challenges to the grid owing to power fluctuations. Hybrid energy storage systems have been an effective solution to smooth out PV output power variations. In order to reduce the required capacity and extend the lifetime of the hybrid energy storage system, a two-stage self-adaptive smoothing approach based on the artificial potential field is proposed to decompose and allocate power among the grid, battery, and supercapacitor dynamically. In the ramp rate control stage, an unsymmetric artificial potential field method is used to regulate the cutoff frequency of a low-pass filter, so as to limit the PV power ramp rate within the prescribed range and allocate the power between the grid and the hybrid energy storage system. In the HESS power distribution stage, a symmetric artificial potential field is adopted to distribute power between the battery and …

A Control-Oriented Voltage Tracking Design for Grid-Forming Based Modular Multilevel Converter

Authors

Wentao Liu,Tamas Kerekes,Remus Teodorescu

Published Date

2023/6/9

Modular multilevel converters (MMCs) based on grid-forming control as a converter-driven interface for renewable energy sources are the development trend of the future electronics-dominated power grids. MMC offers outstanding voltage quality without an AC filter, which is very distinct from the AC topology of conventional two-level converters (TLC). However, most literature that studies the grid-forming MMC directly follows the voltage tracking control (VTC) principle of TLC and does not involve the voltage controller specifically for the MMC topology. In this paper, the design of the voltage controller is step-by-step deduced based on the topological properties of MMC. According to the analysis findings, the proportional link of the voltage loop can result in high-frequency oscillation and the proposed VTC with a sole integral link cooperating with inner current-loop control presents excellent dynamic performance …

Robust PLL-Based Grid Synchronization and Frequency Monitoring

Authors

Florin Iov,Weihao Zhao,Tamas Kerekes

Journal

Energies

Published Date

2023/9/28

Nowadays, the penetration of inverter-based energy resources is continuously increasing in low-voltage distribution grids. Their applications cover traditional renewable energy production and energy storage but also new applications such as charging points for electric vehicles, heat pumps, electrolyzers, etc. The power ratings range from a couple of kW to hundreds of kW. Utilities have, in the last few years, reported more challenges regarding power quality in distribution grids, e.g., high harmonic content, high unbalances, large voltage and frequency excursions, etc. Phase-Lock-Loop (PLL) algorithms are typically used for grid synchronization and decoupled control of power converters connected to the grid. Most of the research within PLLs is mainly focusing on grid voltage angle estimation while the byproducts of the algorithms, e.g., frequency and voltage magnitude, are often overlooked. However, both frequency and voltage magnitude estimations are crucial for grid code compliance. Practical considerations for implementation on microcontroller boards of these algorithms are also missing in most of the cases. The present paper proposes a modified PLL algorithm based on a Synchronous Reference Frame that is suitable for both grid synchronization and frequency monitoring, i.e., the estimation of RMS phase voltages and frequencies in highly distorted distribution grids. It also provides the tuning methodology and practical considerations for implementation on commercial DSP boards. The performance of the proposed approach is assessed through simulation studies and laboratory tests under a wide range of operational conditions …

Small Signal Model of Modular Multilevel Converter with Power Synchronization Control

Authors

Wentao Liu,Rui Wang,Tamas Kerekes,Tomislav Dragicevic,Remus Teodorescu

Published Date

2023/3/19

Power synchronization control (PSC) is one of the popular control schemes in grid-forming control-based converters because it simulates the grid support capability of conventional synchronous generators. However, prior research is based on two-level converters which do not have complex internal circuits, and whether PSC can be directly applied to the modular multilevel converter (MMC) topology since MMC has sub-module capacitor voltage ripples and inherent second harmonic circulating current algorithm, has not been analyzed. This paper establishes the small signal model of MMC with PSC considering the MMC internal dynamic and circulating current suppression control (CCSC). The power oscillation phenomenon when grid short-circuit ratio (SCR) increases is also demonstrated with the closed-loop system eigenvalues calculation and verified with the experimental results.

Capacitor Voltage Feedforward-based Voltage Loop Control for Grid-forming Modular Multilevel Converters Under Wide-range of Grid Strength

Authors

Wentao Liu,Rui Wang,Tamas Kerekes,Tomislav Dragicevic,Remus Teodorescu

Journal

IEEE Transactions on Power Electronics

Published Date

2023/9/22

An efficient closed-loop voltage tracking control (VTC) for a grid-forming-based converter is required for precise voltage regulation. However, few papers designed a VTC exclusively for modular multilevel converter (MMC) with a full understanding of the MMC's internal dynamic coupling and presented a detailed analysis of the controller. In contrast, traditional voltage–current double loop control or its derivatives are employed without considering the impact of the coupled fluctuating capacitor voltage and with insufficient stability analysis under various operating conditions, especially for the wide range of grid short-circuit ratio. To solve these problems on MMC, this article systematically analyzes the effect of each component of capacitor voltages on the output voltage. In this article, an easy-implemental VTC is proposed which takes the dominant factor of capacitor voltage into the feedforward path (CVF). The …

Interleaved Half-Bridge Submodules with Sensorless Leg Current Balancing in Modular Multilevel Converters

Authors

Aleksandr Viatkin,Mattia Ricco,Riccardo Mandrioli,Tamas Kerekes,Remus Teodorescu,Gabriele Grandi

Journal

Authorea Preprints

Published Date

2023/11/8

A new state observer-based current balancing method for Modular Multilevel Converters with Interleaved half-bridge Sub-Modules (ISM-MMC) is presented in this paper. The developed observer allows estimating currents through interleaved half-bridge legs in each submodule of ISM-MMC basing only on arm current and submodule’s capacitor voltage measurements. Then, the interleaved current balancing control uses the estimated currents to reduce the interleaved currents imbalance caused by upstream control actions. This technique minimizes the number of required current sensors in ISM-MMC, thereby reducing the converter’s cost, weight, and volume. Capabilities of the proposed interleaved currents sensorless balancing control has been tested against standard parameter tolerances of the composing passive elements. The feasibility of the proposed method is verified by extensive simulation and experimental tests.

Passivity-Based Stability Design of LCL-Filtered Converters: An Overview

Authors

Jiacheng Sun,Dao Zhou,Tamas Kerekes,Wenli Yao,Xiaobin Zhang

Published Date

2023/3/19

The stability of LCL-type grid-connected converters in distributed power generation systems (DPGS) have been numerously investigated. It is well known that resonance of high-order filters may cause system oscillations and grid current distortion. This phenomenon is more critical when the DPGS contains capacitive loads and cables. Thus, it needs to consider the interaction effect between the equivalent grid impedance and the converter impedance, for which have been addressed by many innovative passivity methods. This paper reviews contributions and classifies of the existing passivity methods with different current controls as single-loop and multi-loop. Based on the concept of passivity, all passivity methods can guarantee the stability of the system by reshaping the output impedance. Several promising methods for different grid impedances are reviewed and evaluated. Finally, suggestions for implementing …

A Real-time Power Management Strategy based on Artificial Potential Field for Residential PV Systems

Authors

Xiangqiang Wu,Zhongting Tang,Tamas Kerekes

Published Date

2023/9/4

In order to avoid invalid optimization of day-ahead energy management strategies due to power fluctuations, a real-time strategy based on the artificial potential field is proposed in this paper. Based on one-year data, it has been validated that the proposed strategy can decrease battery degradation effectively, hence reducing the total operation cost by 4.7%.

Current balancing control for interleaved half-bridge submodules in modular multilevel converters

Authors

Aleksandr Viatkin,Mattia Ricco,Riccardo Mandrioli,Tamas Kerekes,Remus Teodorescu,Gabriele Grandi

Journal

Authorea Preprints

Published Date

2023/10/30

This paper presents a closed-loop current balancing control for Modular Multilevel Converters with Interleaved half-bridge Sub-Modules (ISM-MMC). The new control loop solves the well-known problem of proper current balancing among interleaved half-bridge legs in each ISM-MMC submodule while preserving a simple and reliable structure. In addition to that, a novel capacitor voltage balancing strategy for MMCs is developed. The new algorithm contains main advantages of the classical capacitor voltage balancing methods while provides an opportunity to decouple two balancing tasks of ISM-MMC, namely capacitor voltage and interleaved legs current balancing. The proposed control methods feature good dynamic performance and are compliant with a digital processor’s operational constraints. The effectiveness of the new balancing methods was verified during extensive numerical simulations and experimental tests on a laboratory prototype by the corresponding system response under the input/output characteristics variation and interleaved current control perturbation.

Sizing of Hybrid Supercapacitors and Lithium-Ion Batteries for Green Hydrogen Production from PV in the Australian Climate

Authors

Tarek Ibrahim,Tamas Kerekes,Dezso Sera,Shahrzad S Mohammadshahi,Daniel-Ioan Stroe

Journal

Energies

Published Date

2023/2/22

Instead of storing the energy produced by photovoltaic panels in batteries for later use to power electric loads, green hydrogen can also be produced and used in transportation, heating, and as a natural gas alternative. Green hydrogen is produced in a process called electrolysis. Generally, the electrolyser can generate hydrogen from a fluctuating power supply such as renewables. However, due to the startup time of the electrolyser and electrolyser degradation accelerated by multiple shutdowns, an idle mode is required. When in idle mode, the electrolyser uses 10% of the rated electrolyser load. An energy management system (EMS) shall be applied, where a storage technology such as a lithium-ion capacitor or lithium-ion battery is used. This paper uses a state-machine EMS of PV microgrid for green hydrogen production and energy storage to manage the hydrogen production during the morning from solar power and in the night using the stored energy in the energy storage, which is sized for different scenarios using a lithium-ion capacitor and lithium-ion battery. The mission profile and life expectancy of the lithium-ion capacitor and lithium-ion battery are evaluated considering the system’s local irradiance and temperature conditions in the Australian climate. A tradeoff between storage size and cutoffs of hydrogen production as variables of the cost function is evaluated for different scenarios. The lithium-ion capacitor and lithium-ion battery are compared for each tested scenario for an optimum lifetime. It was found that a lithium-ion battery on average is 140% oversized compared to a lithium-ion capacitor, but a lithium-ion capacitor has a …

Modulation Compensated Power Synchronization Control for Modular Multilevel Converters with Enhanced Performance under Varying SCR

Authors

Wentao Liu,Rui Wang,Tamas Kerekes,Tomislav Dragicevic,Remus Teodorescu

Journal

IEEE Journal of Emerging and Selected Topics in Power Electronics

Published Date

2023/7/7

Power synchronization control (PSC), one of the common grid-forming (GFM) controls, is an emerging grid support technique for converters in the converter-dominated power system. However, its application to modular multilevel converters (MMCs) with dynamic grid conditions and varying grid strength, exposed some instability issues. This article studies the essence of the MMC internal voltage coupling and the degree of influence on the reference voltage under different grid short-circuit ratios (SCRs). It is found that the key reason for instability is that the submodule (SM) capacitor voltage modifies the reference voltage through the nonlinear switching process and eventually generates the voltage error, up to 61.3% with high SCR = 25. Based on the above findings, an easy-to-implement modulation compensation is proposed to enhance the PSC-MMC stability in changing SCR scenarios. A simplified selection …

Resonant Current Impacts on the Lifetime of LCL Filter in PV Systems

Authors

Jiacheng Sun,Xinyue Zhang,Tamas Kerekes,Wenli Yao,Xiaobin Zhang,Dao Zhou

Published Date

2023/10/29

LCL filters are critical in PV inverter systems, and its resonant currents brings more electrothermal stresses on filter capacitors. This paper investigates the influence of resonant currents on damage of capacitors. Different from conventional methods, this paper predicts the lifetime of individual capacitors by comparing the dynamic hot spot temperatures with and without the damping method and using annual mission profiles. Then, based on Monte Carlo simulations and Weibull analysis, reliability curves are connected from the component level of the individual capacitor to the system level of the capacitor bank with help from the reliability block diagrams. The results show that without damping method, the resonant currents have a significant impact on capacitor lifetime. In the case that electrothermal stress concentrates on an individual capacitor, its lifetime is shorter than that of a capacitor bank. Furthermore, the …

A comparison and introduction of novel solar panel’s fault diagnosis technique using deep-features shallow-classifier through infrared thermography

Authors

Waqas Ahmed,Muhammad Umair Ali,MA Parvez Mahmud,Kamran Ali Khan Niazi,Amad Zafar,Tamas Kerekes

Journal

Energies

Published Date

2023/1/17

Solar photovoltaics (PV) are susceptible to environmental and operational stresses due to their operation in an open atmosphere. Early detection and treatment of stress prevents hotspots and the total failure of solar panels. In response, the literature has proposed several approaches, each with its own limitations, such as high processing system requirements, large amounts of memory, long execution times, fewer types of faults diagnosed, failure to extract relevant features, and so on. Therefore, this research proposes a fast framework with the least memory and computing system requirements for the six different faults of a solar panel. Infrared thermographs from solar panels are fed into intense and architecturally complex deep convolutional networks capable of differentiating one million images into 1000 classes. Features without backpropagation are calculated to reduce execution time. Afterward, deep features are fed to shallow classifiers due to their fast training time. The proposed approach trains the shallow classifier in approximately 13 s with 95.5% testing accuracy. The approach is validated by manually extracting thermograph features and through the transfer of learned deep neural network approaches in terms of accuracy and speed. The proposed method is also compared with other existing methods.

Sensitivity Analysis of Day-Ahead Energy Management Strategies under Variant Resolution Mission Profiles

Authors

Xiangqiang Wu,Zhongting Tang,Tamas Kerekes

Published Date

2023/6/14

Energy management strategies directly influence the performance (e.g., cost) of residential PV systems. In state-of-the-art, most forecast-based energy management strategies adopt hour resolution to make decisions, which may have poor robustness and flexibility to fast-changing weather conditions. This paper compares the sensitivity of three typical operation strategies including maximum self-consumption, mixed integer linear programming, and particle swarm optimization under different kinds of resolutions and weather. The results show that the maximum self-consumption strategy has the best robustness and can utilize the battery most at the expense of total cost. In terms of cost, the mixed integer linear programming strategy performs best on the sunny day, and has the best scheduled result on the partly-cloudy day, but the particle swarm optimization strategy performs best in the real case.

An Explicit Subcell-Based Photovoltaic Model and Its Application in Fault Diagnosis Under Partial Shading Conditions

Authors

Xinyi Chen,Yu Shen,Tamas Kerekes,Yiye Wang,Kanjian Zhang,Haikun We

Journal

IEEE Journal of Photovoltaics

Published Date

2023/10/4

Photovoltaic (PV) models under partial shading conditions are typically based on the scenario that one whole module or cell is shaded under uniform low irradiance. Nonuniform partial shading on one cell is seldom discussed. However, partial shading in real life is not usually in homogeneous irradiance. To fully examine the PV behavior under partial shading conditions, a cell has to be divided into several subcells to model nonuniform complex shading patterns. Therefore, this article develops a comprehensive mathematical PV model based on a single-diode model covering shading area, shading transmittance, and avalanche breakdown effect on reverse-biased cells. It simulates the output of subcells, cells, submodules, and modules by the calculation of explicit Lambert W function. The proposed model is validated in experimental tests, and its average relative error is under 5%. Compared with other related studies …

Review of grid stability assessment based on AI and a new concept of converter-dominated power system state of stability assessment

Authors

Wentao Liu,Tamas Kerekes,Tomislav Dragicevic,Remus Teodorescu

Published Date

2023/1/13

Artificial intelligence (AI) has been increasingly used for power system stability assessment due to its fast evaluation speed compared to conventional time-domain methods. This article reviews four types of classic grid stability assessment methods based on AI in the recent literature first, where different AI algorithms from the literature are summarized and compared. Moreover, as the number of power converters using grid forming control intensively increases in the modern system, the influence of the converter parameters on grid stability needs to be investigated. In this context, the concept of the converter-dominated power system state of stability (CDPS-SOS) assessment based on AI is qualitatively discussed. The CDPS-SOS assessment can reveal the system stability margin by considering the converter control parameters and grid bus voltages. Overall, this article aims to give an overview of AI-based stability …

Effect of battery degradation on the probabilistic optimal operation of renewable-based microgrids

Authors

Mahshid Javidsharifi,Hamoun Pourroshanfekr Arabani,Tamas Kerekes,Dezso Sera,Sergiu Spataru,Josep M Guerrero

Journal

Electricity

Published Date

2022/2/4

In order to maximize the use of renewable-based distributed generators (DGs), in addition to dealing with the effects of the inherent power management uncertainties of microgrids (MGs), applying storage devices is essential in the electrical system. The main goal of this paper is to minimize the total operation cost as well as the emissions of MG energy resources, alongside the better utilization of renewable energy sources (RES) and energy storage systems. The uncertainties of wind speed, solar irradiation, market price and electrical load demand are modeled using reduced unscented transformation (RUT) method. Simulation results reveal that, as expected, by increasing the battery efficiency, the achievable minimum daily operational cost of the system is reduced. For example, with 93% battery efficiency, the operational cost equals EUR 9200, while for an efficiency of 97%, the achievable minimum daily operational cost is EUR 8900. Moreover, the proper economic/environmental performance of the suggested approach, which contributes to the possibility of selecting a compromise solution for the MG operator in accordance with technical and economic constraints, is justified.

Performance assessment of mismatch mitigation methodologies using field data in solar photovoltaic systems

Authors

Kamran Ali Khan Niazi,Tamas Kerekes,Alberto Dolara,Yongheng Yang,Sonia Leva

Journal

Electronics

Published Date

2022/6/21

Partial shading and other non-ideal conditions cause electrical mismatches that reduce the output power generated by a photovoltaic (PV) system. It affects the overall performance and efficiency of PV systems. Therefore, a model is developed in MATLAB, which analyses the performance of the PV systems under real irradiance profiles and temperatures for various available mismatch mitigation methodologies, i.e., bypass diode, DC power optimizer, and differential power processing (DPP). More specifically, this study will help to understand the best mismatch reduction methodologies for a solar PV system under different scenarios. The results also are validated by comparing them with a similar PV system installed in SolarTechLAB, which also operates under the same irradiance and temperature conditions under which these models are tested. This study also presents novel results, covering discussions on the reverse voltage distribution under mismatch scenarios among bypass diode, DC power optimizer, and DPP techniques.

See List of Professors in Tamás Kerekes University(Aalborg Universitet)

Tamás Kerekes FAQs

What is Tamás Kerekes's h-index at Aalborg Universitet?

The h-index of Tamás Kerekes has been 31 since 2020 and 42 in total.

What are Tamás Kerekes's top articles?

The articles with the titles of

Lithium-Ion Supercapacitors and Batteries for Off-Grid PV Applications: Lifetime and Sizing

Dual-level design for cost-effective sizing and power management of hybrid energy storage in photovoltaic systems

An adaptive power smoothing approach based on artificial potential field for PV plant with hybrid energy storage system

A Control-Oriented Voltage Tracking Design for Grid-Forming Based Modular Multilevel Converter

Robust PLL-Based Grid Synchronization and Frequency Monitoring

Small Signal Model of Modular Multilevel Converter with Power Synchronization Control

Capacitor Voltage Feedforward-based Voltage Loop Control for Grid-forming Modular Multilevel Converters Under Wide-range of Grid Strength

Interleaved Half-Bridge Submodules with Sensorless Leg Current Balancing in Modular Multilevel Converters

...

are the top articles of Tamás Kerekes at Aalborg Universitet.

What are Tamás Kerekes's research interests?

The research interests of Tamás Kerekes are: power electronics, grid connection, renewable energy

What is Tamás Kerekes's total number of citations?

Tamás Kerekes has 9,017 citations in total.

What are the co-authors of Tamás Kerekes?

The co-authors of Tamás Kerekes are Frede Blaabjerg, Remus Teodorescu, Marco Liserre, Yongheng Yang, Dezso Sera, Ke Ma.

    Co-Authors

    H-index: 197
    Frede Blaabjerg

    Frede Blaabjerg

    Aalborg Universitet

    H-index: 104
    Remus Teodorescu

    Remus Teodorescu

    Aalborg Universitet

    H-index: 89
    Marco Liserre

    Marco Liserre

    Christian-Albrechts-Universität zu Kiel

    H-index: 65
    Yongheng Yang

    Yongheng Yang

    Zhejiang University

    H-index: 44
    Dezso Sera

    Dezso Sera

    Queensland University of Technology

    H-index: 41
    Ke Ma

    Ke Ma

    Shanghai Jiao Tong University

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