Pub Date : 2014-11-01DOI: 10.1109/PEAC.2014.7038044
Huiyong Hu, Wei Wei, Yong-gang Peng, J. Lei
This paper describes the design principles of damped proportional-resonant (PR) controllers used for the grid-connected inverters. Previous works focused on the frequency domain analysis to select parameters, which can't reflect the time domain performance directly. This paper presents a mathematical model of grid-connected inverter connected with a LC filter and isolation transformer in the stationary reference frame, whose order is reduced by weighted current feedback. Based on the reduced-order model, the principles for designing damped PR controllers in the frequency domain are presented in details. The optimized design of damped PR controller through genetic algorithm using the cumulative amount of current tracking error as indicator of the time-domain performance is proposed. Compared with traditional system, the system with the optimized damped PR controller achieves not only better stability in the frequency domain, but also more excellent performances of current tracking and lower total harmonic distortion in the time domain. Simulation results are presented to verify the feasibility and effectiveness of the proposed approach.
{"title":"Optimized design of damped proportional-resonant controllers for grid-connected inverters through genetic algorithm","authors":"Huiyong Hu, Wei Wei, Yong-gang Peng, J. Lei","doi":"10.1109/PEAC.2014.7038044","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7038044","url":null,"abstract":"This paper describes the design principles of damped proportional-resonant (PR) controllers used for the grid-connected inverters. Previous works focused on the frequency domain analysis to select parameters, which can't reflect the time domain performance directly. This paper presents a mathematical model of grid-connected inverter connected with a LC filter and isolation transformer in the stationary reference frame, whose order is reduced by weighted current feedback. Based on the reduced-order model, the principles for designing damped PR controllers in the frequency domain are presented in details. The optimized design of damped PR controller through genetic algorithm using the cumulative amount of current tracking error as indicator of the time-domain performance is proposed. Compared with traditional system, the system with the optimized damped PR controller achieves not only better stability in the frequency domain, but also more excellent performances of current tracking and lower total harmonic distortion in the time domain. Simulation results are presented to verify the feasibility and effectiveness of the proposed approach.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"139 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124396854","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7038022
Xiuting Lv, Ping-an Tan
This paper focuses on the modeling and simulation of silicon carbide(SiC) bipolar junction transistor(BJT). SiC BJT is modeled in MATLAB using internal dynamical equation, and the Haar wavelet method is used to solve the ambipolar diffusion equation (ADE). The simulation results of switching waveforms of SiC BJT are given, which verify the validity of this method.
{"title":"A wavelet based method for modeling and simulation of a SiC BJT","authors":"Xiuting Lv, Ping-an Tan","doi":"10.1109/PEAC.2014.7038022","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7038022","url":null,"abstract":"This paper focuses on the modeling and simulation of silicon carbide(SiC) bipolar junction transistor(BJT). SiC BJT is modeled in MATLAB using internal dynamical equation, and the Haar wavelet method is used to solve the ambipolar diffusion equation (ADE). The simulation results of switching waveforms of SiC BJT are given, which verify the validity of this method.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120836854","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7037907
P. Alemi, Cheol-Ju Bae, Dong-Choon Lee
This paper proposes a novel resonance suppression scheme for a single-phase grid inverter with the LLCL filters. In the structure of the LLCL filters, a small inductor is connected in series with the capacitor in the conventional LCL filters to make zero impedance at the switching frequency, by which the grid-side inductor filter can be reduced remarkably. However, since the resonance phenomenon is a critical issue in this case, a new control method using the proportional and resonant (PR) controllers is proposed to damp out the resonance. The simulation results have verified the effectiveness of the proposed control algorithm for a single-phase grid inverter.
{"title":"Resonance suppression scheme in single-phase grid inverters with LLCL filters","authors":"P. Alemi, Cheol-Ju Bae, Dong-Choon Lee","doi":"10.1109/PEAC.2014.7037907","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7037907","url":null,"abstract":"This paper proposes a novel resonance suppression scheme for a single-phase grid inverter with the LLCL filters. In the structure of the LLCL filters, a small inductor is connected in series with the capacitor in the conventional LCL filters to make zero impedance at the switching frequency, by which the grid-side inductor filter can be reduced remarkably. However, since the resonance phenomenon is a critical issue in this case, a new control method using the proportional and resonant (PR) controllers is proposed to damp out the resonance. The simulation results have verified the effectiveness of the proposed control algorithm for a single-phase grid inverter.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128997516","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7038084
Jinlong Wang, Fanghua Zhang, Jianghua Xie, Shuai Zhang, Shuo Liu
When the inductor current of boundary conduction mode (BCM) Buck converter, falls to zero, the output filter inductor will resonate with the capacitor across the switch called Quasi Resonant (QR). If the switch is turned on when the voltage of resonant capacitor is zero, ZVS and ZCS turn-on can be achieved, the switching loss is eliminated. This thesis analyses the resonant between the output inductor and the capacitor in detail, and find out the time when the voltage across the switch is zero. Then by using a simple zero current detective method and a properly delay circuit, to assure ZVS and ZCS turn-on of the switch. When the Buck converter works in BCM mode the output filter inductor is small, the reverse recovery loss of diode is eliminated, dynamic response time can be reduced. And there is a capacitor across the switch, when it is turned off, ZVS turn-off is achieved. At last a 3kw prototype is designed, the highest efficiency is 98.7%.
{"title":"Analysis and design of high efficiency Quasi-Resonant Buck converter","authors":"Jinlong Wang, Fanghua Zhang, Jianghua Xie, Shuai Zhang, Shuo Liu","doi":"10.1109/PEAC.2014.7038084","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7038084","url":null,"abstract":"When the inductor current of boundary conduction mode (BCM) Buck converter, falls to zero, the output filter inductor will resonate with the capacitor across the switch called Quasi Resonant (QR). If the switch is turned on when the voltage of resonant capacitor is zero, ZVS and ZCS turn-on can be achieved, the switching loss is eliminated. This thesis analyses the resonant between the output inductor and the capacitor in detail, and find out the time when the voltage across the switch is zero. Then by using a simple zero current detective method and a properly delay circuit, to assure ZVS and ZCS turn-on of the switch. When the Buck converter works in BCM mode the output filter inductor is small, the reverse recovery loss of diode is eliminated, dynamic response time can be reduced. And there is a capacitor across the switch, when it is turned off, ZVS turn-off is achieved. At last a 3kw prototype is designed, the highest efficiency is 98.7%.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130699770","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7037905
Minglin Zhu, Shengbao Geng, Yungui Li, L. Hang, Guojie Li
In AC/DC hybrid grid, the individual AC and DC grids exist. The power converters are the key interfaces between these two kinds of individual grids. Under unbalance AC grid, the grid voltage is distorted and the harmonics is involved. Therefore, the active power and reactive power also give rise to the uncontrolled oscillations, which will damage the interface converters. In order to ensure the safety of the converters and the facilities in the grids, the proper control strategy is crucial in AC/DC hybrid grids. In this paper an improved Flexible Positive- and Negative- Sequence Control method (FPNSC) used in d-q axis is proposed. From the simulating and experimental results, this new method shows its advantages compared to other classical methods such as Positive- and Negative-Sequence Control, Average Active-Reactive Control, and Balanced Positive-Sequence Control.
{"title":"Protected control strategies for voltage-source-converter (VSC) under grid faults in AC/DC hybrid grid","authors":"Minglin Zhu, Shengbao Geng, Yungui Li, L. Hang, Guojie Li","doi":"10.1109/PEAC.2014.7037905","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7037905","url":null,"abstract":"In AC/DC hybrid grid, the individual AC and DC grids exist. The power converters are the key interfaces between these two kinds of individual grids. Under unbalance AC grid, the grid voltage is distorted and the harmonics is involved. Therefore, the active power and reactive power also give rise to the uncontrolled oscillations, which will damage the interface converters. In order to ensure the safety of the converters and the facilities in the grids, the proper control strategy is crucial in AC/DC hybrid grids. In this paper an improved Flexible Positive- and Negative- Sequence Control method (FPNSC) used in d-q axis is proposed. From the simulating and experimental results, this new method shows its advantages compared to other classical methods such as Positive- and Negative-Sequence Control, Average Active-Reactive Control, and Balanced Positive-Sequence Control.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130320994","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7038097
Fujun Ma, An Luo, Qiaobo Xiong
In order to meet the requirements of electrolytic copper-foil, a 6.5V/50kA power supply system composed of ten power modules is developed. The power module is composed of two-leg PWM rectifier and dc/dc converter, and dc/dc converter adopts two full-wave rectifiers in parallel to enhance the output ability. In order to meet the process requirements of electrolytic copper-foil, a virtual impedance based current-sharing control method with load current full feedforward is proposed for n-parallel dc/dc converters. The virtual impedance is used to adjust the current-sharing impedance without changing the equivalent output impedance of converter. It can effectively improve the output performance and eliminate the current-sharing errors. Finally, simulation and industrial application results have verified the structure and control method.
{"title":"The development of high-current power supply system for electrolytic copper-foil","authors":"Fujun Ma, An Luo, Qiaobo Xiong","doi":"10.1109/PEAC.2014.7038097","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7038097","url":null,"abstract":"In order to meet the requirements of electrolytic copper-foil, a 6.5V/50kA power supply system composed of ten power modules is developed. The power module is composed of two-leg PWM rectifier and dc/dc converter, and dc/dc converter adopts two full-wave rectifiers in parallel to enhance the output ability. In order to meet the process requirements of electrolytic copper-foil, a virtual impedance based current-sharing control method with load current full feedforward is proposed for n-parallel dc/dc converters. The virtual impedance is used to adjust the current-sharing impedance without changing the equivalent output impedance of converter. It can effectively improve the output performance and eliminate the current-sharing errors. Finally, simulation and industrial application results have verified the structure and control method.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129510509","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7037895
Yenan Chen, Jiangbei Xi, Dehong Xu
Leakage current suppression for a transformerless zero voltage switching (ZVS) full-bridge inverter is investigated. The leakage current model and the common mode voltage of the ZVS full-bridge inverter are analyzed. The leakage current flowing through the parasitic capacitor between PV panels and the ground is reduced by a common mode inductor and the bypass capacitors. The theoretical analysis of proposed method is presented. Finally the leakage current suppression is verified by simulation and experiment.
{"title":"Leakage current suppression for transformerless ZVS full-bridge inverter","authors":"Yenan Chen, Jiangbei Xi, Dehong Xu","doi":"10.1109/PEAC.2014.7037895","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7037895","url":null,"abstract":"Leakage current suppression for a transformerless zero voltage switching (ZVS) full-bridge inverter is investigated. The leakage current model and the common mode voltage of the ZVS full-bridge inverter are analyzed. The leakage current flowing through the parasitic capacitor between PV panels and the ground is reduced by a common mode inductor and the bypass capacitors. The theoretical analysis of proposed method is presented. Finally the leakage current suppression is verified by simulation and experiment.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130258099","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7038071
Zhonghua Zhu, Yongai Zheng, Yu Fang, Pan Xu
This paper analyzes the necessity of establishing the dc bus voltage of the Dual Active Bridge (Dual Active Bridge, DAB) converter when starting up. And the startup method that the DC-bus voltage is built up only by high-voltage-side body diode of the DAB converter rectifying is proposed in the paper. The detailed steps and the software realization method are elaborated. The saturation phenomenon of the inductor and the current surge can be effectively avoided in this way and the method presented in this paper implemented only by digital control, so this method does not need to add extra hardware. Finally, the experimental results verify the method.
本文分析了双有源桥式(Dual Active Bridge, DAB)变换器启动时建立直流母线电压的必要性。提出了仅靠DAB变换器的高压侧体二极管整流来建立直流母线电压的启动方法。阐述了具体步骤和软件实现方法。这种方法可以有效地避免电感的饱和现象和电流浪涌，而且本文的方法仅通过数字控制实现，因此不需要增加额外的硬件。最后，通过实验验证了该方法的有效性。
{"title":"Analysis of the startup method for building up DC voltage via body diode rectifying in Dual Active Bridge converter","authors":"Zhonghua Zhu, Yongai Zheng, Yu Fang, Pan Xu","doi":"10.1109/PEAC.2014.7038071","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7038071","url":null,"abstract":"This paper analyzes the necessity of establishing the dc bus voltage of the Dual Active Bridge (Dual Active Bridge, DAB) converter when starting up. And the startup method that the DC-bus voltage is built up only by high-voltage-side body diode of the DAB converter rectifying is proposed in the paper. The detailed steps and the software realization method are elaborated. The saturation phenomenon of the inductor and the current surge can be effectively avoided in this way and the method presented in this paper implemented only by digital control, so this method does not need to add extra hardware. Finally, the experimental results verify the method.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"16 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114125628","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7037995
Qiqi Zhao, Yu Fang, Mingming Ma, Jun Wang, Yong Xie
A fuzzy control strategy is presented to implement the neutral-point (NP) potential balance based on the power stage of three-level Boost dc-dc converter in this paper. The presented fuzzy controller can solve the imbalance problem of NP potential in the process of starting up and can suppress the influence of inverter circuit modulation strategy on NP potential. It is the fuzzy controller that can adaptively change duty cycle ratio to implement the balance between the output capacitor voltages, not only in the process of starting up, but also in steady operation state. The fuzzy controller has been designed in this paper and the control rules have been given to achieve perfect dynamic and steady performance. Finally, the simulation and experimental results verify the feasibility and reliability of this methods way and the method presented in this paper implemented only by digital control, so this method does not need to add extra hardware. Finally, the experimental results verify the method.
{"title":"Study on a fuzzy controller for the balance of capacitor voltages of three-level boost dc-dc converter","authors":"Qiqi Zhao, Yu Fang, Mingming Ma, Jun Wang, Yong Xie","doi":"10.1109/PEAC.2014.7037995","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7037995","url":null,"abstract":"A fuzzy control strategy is presented to implement the neutral-point (NP) potential balance based on the power stage of three-level Boost dc-dc converter in this paper. The presented fuzzy controller can solve the imbalance problem of NP potential in the process of starting up and can suppress the influence of inverter circuit modulation strategy on NP potential. It is the fuzzy controller that can adaptively change duty cycle ratio to implement the balance between the output capacitor voltages, not only in the process of starting up, but also in steady operation state. The fuzzy controller has been designed in this paper and the control rules have been given to achieve perfect dynamic and steady performance. Finally, the simulation and experimental results verify the feasibility and reliability of this methods way and the method presented in this paper implemented only by digital control, so this method does not need to add extra hardware. Finally, the experimental results verify the method.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114468650","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 : 2014-11-01DOI: 10.1109/PEAC.2014.7037846
Shude Yang, Xiangqian Tong, Hao Zhang
The wind power has the characteristics of intermittent, randomness and uncertainty. In order to make better use of wind power, many scholars use historical data to study the power fluctuation characteristics of wind power generation system,but as for the preparation or built-in wind farms, there are abundant wind speed data but without power data. So how to infer the electric power fluctuations from large numbers of wind speed data that is meaningful to the selection of wind farm related facilities. This paper decomposes the electric and wind power fluctuations in different frequency bands by using wavelet packet method with large numbers of wind speed and electric power data as samples. The rules of the electric and wind power changing with frequency are analyzed in detail and the transfer characteristics from wind power to electric power were drawn finally, which transform the electric power estimation into wind power estimation. This conclusion can provide some references for power fluctuations in preparation or built-in wind farms evaluation and the energy storage device selection to smooth the power fluctuations.
{"title":"Study on power dynamic transfer characteristics of wind power generation system","authors":"Shude Yang, Xiangqian Tong, Hao Zhang","doi":"10.1109/PEAC.2014.7037846","DOIUrl":"https://doi.org/10.1109/PEAC.2014.7037846","url":null,"abstract":"The wind power has the characteristics of intermittent, randomness and uncertainty. In order to make better use of wind power, many scholars use historical data to study the power fluctuation characteristics of wind power generation system,but as for the preparation or built-in wind farms, there are abundant wind speed data but without power data. So how to infer the electric power fluctuations from large numbers of wind speed data that is meaningful to the selection of wind farm related facilities. This paper decomposes the electric and wind power fluctuations in different frequency bands by using wavelet packet method with large numbers of wind speed and electric power data as samples. The rules of the electric and wind power changing with frequency are analyzed in detail and the transfer characteristics from wind power to electric power were drawn finally, which transform the electric power estimation into wind power estimation. This conclusion can provide some references for power fluctuations in preparation or built-in wind farms evaluation and the energy storage device selection to smooth the power fluctuations.","PeriodicalId":309780,"journal":{"name":"2014 International Power Electronics and Application Conference and Exposition","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123010257","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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