Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378945
Liao Kunyu, Tao Shun, Zhao Lei, Yao Liting, Xiao Xiangning
when designing a passive network to compensate unbalanced load, an ideal and balanced voltage source is usually taken to generate the voltage at the point of common coupling (PCC), but the compensation results is not so good due to the unbalance of PCC voltage in real systems. With regard to three- phase three-wire circuit, the system side is equivalent to Thevenin model, and the negative sequence current of the load is decomposed into three parts, after being weighted and allotted into three phases, each part then rotates to the positive sequence. Based on the above procedure, the negative sequence weighted equivalent model of three-phase unbalanced load is established in this paper. With equivalent load parameters, the negative- sequence-weighted formula of passive compensation network parameters is presented utilizing the Steinmetz theory. Since the network parameters are functions of negative-sequence-weights, the proposed compensation method can provide a theoretical basis for optimal balance compensation. Simulation results verify the validity of the equivalent model and compensation method proposed.
{"title":"A balance compensation method based on negative sequence weighted equivalent model of unbalanced load","authors":"Liao Kunyu, Tao Shun, Zhao Lei, Yao Liting, Xiao Xiangning","doi":"10.1109/ICHQP.2018.8378945","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378945","url":null,"abstract":"when designing a passive network to compensate unbalanced load, an ideal and balanced voltage source is usually taken to generate the voltage at the point of common coupling (PCC), but the compensation results is not so good due to the unbalance of PCC voltage in real systems. With regard to three- phase three-wire circuit, the system side is equivalent to Thevenin model, and the negative sequence current of the load is decomposed into three parts, after being weighted and allotted into three phases, each part then rotates to the positive sequence. Based on the above procedure, the negative sequence weighted equivalent model of three-phase unbalanced load is established in this paper. With equivalent load parameters, the negative- sequence-weighted formula of passive compensation network parameters is presented utilizing the Steinmetz theory. Since the network parameters are functions of negative-sequence-weights, the proposed compensation method can provide a theoretical basis for optimal balance compensation. Simulation results verify the validity of the equivalent model and compensation method proposed.","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"89 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80336106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378845
Jingzong Zhang, Hongkun Chen, Linghua Zeng, T. Ding
A method of harmonic responsibility division is proposed by the combination of background harmonic voltage segmentation and multiple linear regression based on the improved Hampel function in the complex field. The background harmonic voltage is clustered and divided into different data segments, and the multiple linear regression model based on the improved Hampel weight function in the complex field is introduced to further improve the accuracy of harmonic responsibility division. The method proposed is tested on IEEE 13-bus system and a simple experimental circuit respectively. The results show that the proposed method is able to improve the accuracy of harmonic responsibility division, especially under high harmonic voltage fluctuation at the PCC node.
{"title":"Responsibility division optimization for multiple harmonic sources based on the improved hampel weight function","authors":"Jingzong Zhang, Hongkun Chen, Linghua Zeng, T. Ding","doi":"10.1109/ICHQP.2018.8378845","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378845","url":null,"abstract":"A method of harmonic responsibility division is proposed by the combination of background harmonic voltage segmentation and multiple linear regression based on the improved Hampel function in the complex field. The background harmonic voltage is clustered and divided into different data segments, and the multiple linear regression model based on the improved Hampel weight function in the complex field is introduced to further improve the accuracy of harmonic responsibility division. The method proposed is tested on IEEE 13-bus system and a simple experimental circuit respectively. The results show that the proposed method is able to improve the accuracy of harmonic responsibility division, especially under high harmonic voltage fluctuation at the PCC node.","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"103 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85854007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378920
M. de Ápraiz, R. Diego, J. Barros
This paper presents a method based on the use of the residual of an Extended Kalman filter for step transient detection in phasor measurement units. The residual in a Kalman filter, defined as the difference between the measurement and the estimation, is close to zero when the signal is in stationary state but presents a significant increase at the beginning of a sudden change, when a large mismatch appears between the measurement and the estimation. Comparing the instantaneous magnitude of the residual with an adequate detection threshold, a step transient can be detected in the input signal. The paper studies the performance of the method in the detection of step transients in magnitude and phase angle, power swings, high-frequency transients and transient harmonic distortion in power system networks.
{"title":"Transient detection in phasor measurement units with kalman filtering","authors":"M. de Ápraiz, R. Diego, J. Barros","doi":"10.1109/ICHQP.2018.8378920","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378920","url":null,"abstract":"This paper presents a method based on the use of the residual of an Extended Kalman filter for step transient detection in phasor measurement units. The residual in a Kalman filter, defined as the difference between the measurement and the estimation, is close to zero when the signal is in stationary state but presents a significant increase at the beginning of a sudden change, when a large mismatch appears between the measurement and the estimation. Comparing the instantaneous magnitude of the residual with an adequate detection threshold, a step transient can be detected in the input signal. The paper studies the performance of the method in the detection of step transients in magnitude and phase angle, power swings, high-frequency transients and transient harmonic distortion in power system networks.","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"120 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86174154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378926
Dilini Darmawardana, S. Perera, D. Robinson, P. Ciufo, Jan Meyer, M. Klatt, U. Jayatunga
Due to the increasing number and capacity of grid connected power electronic interfaces associated with distributed generating systems, there is increasing concern on the associated power quality problems. Amongst these, high frequency (HF) emissions (referred to as Supraharmonics) in the range 2–150 kHz has become a topic of growing interest within power quality research communities. An increasingly prominent grid connected devices which can contribute to these HF emissions are the photovoltaic (PV) systems. In this paper, HF emissions from seven small (output power ≤ 10kW), grid-tied, photovoltaic inverters (both single phase inverters and three phase inverter composed of three single phase inverters) are analysed using measurements carried out under controlled conditions in laboratory environments. It is shown that under fixed network conditions, these HF emissions are affected by the MPPT (Maximum Power Point Tracking) voltage and the output power level of the PV inverter. Moreover, a strong correlation between the behaviour of HF emissions and the topologies of inverters was observed; an important factor in developing high frequency models of PV inverters.
{"title":"Investigation of high frequency emissions (supraharmonics) from small, grid-tied, photovoltaic inverters of different topologies","authors":"Dilini Darmawardana, S. Perera, D. Robinson, P. Ciufo, Jan Meyer, M. Klatt, U. Jayatunga","doi":"10.1109/ICHQP.2018.8378926","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378926","url":null,"abstract":"Due to the increasing number and capacity of grid connected power electronic interfaces associated with distributed generating systems, there is increasing concern on the associated power quality problems. Amongst these, high frequency (HF) emissions (referred to as Supraharmonics) in the range 2–150 kHz has become a topic of growing interest within power quality research communities. An increasingly prominent grid connected devices which can contribute to these HF emissions are the photovoltaic (PV) systems. In this paper, HF emissions from seven small (output power ≤ 10kW), grid-tied, photovoltaic inverters (both single phase inverters and three phase inverter composed of three single phase inverters) are analysed using measurements carried out under controlled conditions in laboratory environments. It is shown that under fixed network conditions, these HF emissions are affected by the MPPT (Maximum Power Point Tracking) voltage and the output power level of the PV inverter. Moreover, a strong correlation between the behaviour of HF emissions and the topologies of inverters was observed; an important factor in developing high frequency models of PV inverters.","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"87 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73916524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378889
D. Schwanz, T. Busatto, M. Bollen, A. Larsson
In this paper, the hosting capacity considering harmonic distortion is estimated for single-phase-connected photovoltaic inverters (PVIs) in low-voltage distribution networks. A stochastic approach is used to calculate the harmonic voltage distortion with each customer in the network. The method has been applied to a 6-customer network for the connection of 2.5-kW single-phase PVIs with and without harmonic voltage background. From the results, it was observed that the contribution from 2.5 kW single-phase photovoltaic inverters to the individual harmonic distortion will not cause the established limits to be exceeded. Also, that the harmonic voltage background is often dominating and should be continuously observed.
{"title":"A stochastic study of harmonic voltage distortion considering single-phase photovoltaic inverters","authors":"D. Schwanz, T. Busatto, M. Bollen, A. Larsson","doi":"10.1109/ICHQP.2018.8378889","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378889","url":null,"abstract":"In this paper, the hosting capacity considering harmonic distortion is estimated for single-phase-connected photovoltaic inverters (PVIs) in low-voltage distribution networks. A stochastic approach is used to calculate the harmonic voltage distortion with each customer in the network. The method has been applied to a 6-customer network for the connection of 2.5-kW single-phase PVIs with and without harmonic voltage background. From the results, it was observed that the contribution from 2.5 kW single-phase photovoltaic inverters to the individual harmonic distortion will not cause the established limits to be exceeded. Also, that the harmonic voltage background is often dominating and should be continuously observed.","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"117 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73941410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378910
M. Michalski
The paper presents results of preliminary research on possibility to recreate a variation of voltage in power grid on the basis of recorded values of measures of the variation. This is a complex issue because the voltage changes that occur in real networks are random. Five algorithms have been proposed and their quality has been verified using the obtained values of Pst short-term flicker indicator. Description of the algorithms and results analysis have been preceded by the introduction that aims at short description of selected voltage variation indices.
{"title":"Introductory results of tests of algorithms for recreation of voltage variation with voltage fluctuation indices","authors":"M. Michalski","doi":"10.1109/ICHQP.2018.8378910","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378910","url":null,"abstract":"The paper presents results of preliminary research on possibility to recreate a variation of voltage in power grid on the basis of recorded values of measures of the variation. This is a complex issue because the voltage changes that occur in real networks are random. Five algorithms have been proposed and their quality has been verified using the obtained values of Pst short-term flicker indicator. Description of the algorithms and results analysis have been preceded by the introduction that aims at short description of selected voltage variation indices.","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"87 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75705713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378844
C. Noce, M. De Santis, P. Varilone, P. Verde
In this paper, we analysed two methods, M1 and M2, for determining in which network the voltage sags originated. The problem referred to the High Voltage (HV) and Medium Voltage (MV) systems interconnected by HV/MV stations. The methods were compared using time domain simulations, short circuits were forced on the HV or the MV network, the voltage sags were observed, and M1 and M2 were applied. Comparisons of M1 and M2 behaviours were done for the same network architecture with and without Distributed Generation (DG).
{"title":"Comparison of methods using only voltage measurements for detecting the origin of voltage sags in the modern distribution networks","authors":"C. Noce, M. De Santis, P. Varilone, P. Verde","doi":"10.1109/ICHQP.2018.8378844","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378844","url":null,"abstract":"In this paper, we analysed two methods, M1 and M2, for determining in which network the voltage sags originated. The problem referred to the High Voltage (HV) and Medium Voltage (MV) systems interconnected by HV/MV stations. The methods were compared using time domain simulations, short circuits were forced on the HV or the MV network, the voltage sags were observed, and M1 and M2 were applied. Comparisons of M1 and M2 behaviours were done for the same network architecture with and without Distributed Generation (DG).","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"35 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72844982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378839
W. Boonkird, S. Premrudeepreechacharn, Y. Baghzouz
This paper studies the voltage sag on a distribution system that delivers power to an array of water pumps in Mae Moh mine. Mae Moh mine is an open pit mine, therefore, electric pump is a crucial equipment for pumping water out of mine. DIgSILENT's PowerFactory software is used for modeling the electrical system and assessing the severity of voltage sag that is caused by sequential starting of large motors as this might affect some sensitive loads at various buses. Possible solutions are described for the worse cases where the voltage dip is considered unacceptable.
{"title":"Impact of voltage sag on electrical system for water pumping of Mae Moh mine","authors":"W. Boonkird, S. Premrudeepreechacharn, Y. Baghzouz","doi":"10.1109/ICHQP.2018.8378839","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378839","url":null,"abstract":"This paper studies the voltage sag on a distribution system that delivers power to an array of water pumps in Mae Moh mine. Mae Moh mine is an open pit mine, therefore, electric pump is a crucial equipment for pumping water out of mine. DIgSILENT's PowerFactory software is used for modeling the electrical system and assessing the severity of voltage sag that is caused by sequential starting of large motors as this might affect some sensitive loads at various buses. Possible solutions are described for the worse cases where the voltage dip is considered unacceptable.","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"30 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73135340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378862
Abdelfatah Ali, D. Raisz, K. Mahmoud
As the penetration level of the photovoltaic (PV) system increases over the coming decades, reverse power flows on the distribution feeder will happen and the associated voltage rise might lead to violations of voltage limits. The severity of the voltage regulation problem depends on the relative size and location of PV system, loads, and the distribution feeder topology. This paper proposes an approach to solve the voltage rise problem associated with PV system and to improve the total voltage deviation by optimally increasing the capacity of the PV inverter over the capacity of the PV modules in the presence of capacitor banks. An optimization model is constructed to calculate the optimal inverter capacity with minimizing the cost of PV inverter as well as the total voltage deviation on the distribution network. The overall system constraints are considered in the optimization model. The proposed approach is tested using the IEEE 119-node distribution network. The effectiveness of the proposed approach is demonstrated by calculating the optimal capacity of the PV inverter for mitigating the voltage rise problem and reducing the total voltage deviation.
{"title":"Optimal planning of PV inverter in the presence of capacitor bank in medium-voltage distribution networks","authors":"Abdelfatah Ali, D. Raisz, K. Mahmoud","doi":"10.1109/ICHQP.2018.8378862","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378862","url":null,"abstract":"As the penetration level of the photovoltaic (PV) system increases over the coming decades, reverse power flows on the distribution feeder will happen and the associated voltage rise might lead to violations of voltage limits. The severity of the voltage regulation problem depends on the relative size and location of PV system, loads, and the distribution feeder topology. This paper proposes an approach to solve the voltage rise problem associated with PV system and to improve the total voltage deviation by optimally increasing the capacity of the PV inverter over the capacity of the PV modules in the presence of capacitor banks. An optimization model is constructed to calculate the optimal inverter capacity with minimizing the cost of PV inverter as well as the total voltage deviation on the distribution network. The overall system constraints are considered in the optimization model. The proposed approach is tested using the IEEE 119-node distribution network. The effectiveness of the proposed approach is demonstrated by calculating the optimal capacity of the PV inverter for mitigating the voltage rise problem and reducing the total voltage deviation.","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"785 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76919236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-05-01DOI: 10.1109/ICHQP.2018.8378853
S. Sakar, S. Rönnberg, M. Bollen
LED lighting technology is the most efficient way of lighting service and its usage has increased rapidly. Although, LED lamps are potential victim and source of electromagnetic interference in the frequency range between 2 kHz and 150 kHz (“supraharmonics”). Therefore, immunity test for this frequency range is necessary to analyze its performance variations. In this study, Test profiles described in IEC 61000-4-19 have been applied to LED lamps and the results have been analyzed according to implemented algorithm that uses the relative light intensity variation index. The results show that both supraharmonics and modulation of the test profiles can reveal light flicker. In addition, some potential drawbacks of the standard have been found that deviation of the mains' frequency is also another factor causes intermodulation/non- synchronization on the applied test signal, so this can be seen as light flicker. This issue better be clarified with more details in the IEC 61000-4-19, particalulary for lighting equipment
{"title":"Immunity test of LED lamps based on IEC 61000-4 19 and unexpected consequence","authors":"S. Sakar, S. Rönnberg, M. Bollen","doi":"10.1109/ICHQP.2018.8378853","DOIUrl":"https://doi.org/10.1109/ICHQP.2018.8378853","url":null,"abstract":"LED lighting technology is the most efficient way of lighting service and its usage has increased rapidly. Although, LED lamps are potential victim and source of electromagnetic interference in the frequency range between 2 kHz and 150 kHz (“supraharmonics”). Therefore, immunity test for this frequency range is necessary to analyze its performance variations. In this study, Test profiles described in IEC 61000-4-19 have been applied to LED lamps and the results have been analyzed according to implemented algorithm that uses the relative light intensity variation index. The results show that both supraharmonics and modulation of the test profiles can reveal light flicker. In addition, some potential drawbacks of the standard have been found that deviation of the mains' frequency is also another factor causes intermodulation/non- synchronization on the applied test signal, so this can be seen as light flicker. This issue better be clarified with more details in the IEC 61000-4-19, particalulary for lighting equipment","PeriodicalId":6506,"journal":{"name":"2018 18th International Conference on Harmonics and Quality of Power (ICHQP)","volume":"265 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75917056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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