The Experts below are selected from a list of 145947 Experts worldwide ranked by ideXlab platform
Alex Q. Huang - One of the best experts on this subject based on the ideXlab platform.
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Current sensorless Power Balance strategy for DC/DC converters in a cascaded multilevel converter based solid state transformer
IEEE Transactions on Power Electronics, 2014Co-Authors: Xu She, Alex Q. Huang, Xijun NiAbstract:This letter proposes a current sensorless controller for balancing the Power in the dc/dc stage of a cascaded multilevel converter based solid state transformer. It is revealed that the equalization of the active Power component of duty cycles in the cascaded multilevel rectifier stage can be a good indicator of Power Balance in the dc/dc stage. Additionally, the Power Balance of the dc/dc stage can guarantee the voltage Balance in the rectifier stage if the differences among the Power devices are negligible. Based on this principle, a novel Power Balance controller without sensing any current in the dc/dc stage is proposed. In the end, experimental results in a seven-level three-stage solid state transformer are provided for verifying the proposed method.
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Voltage and Power Balance control for a cascaded h-bridge converter-based solid-state Transformer
IEEE Transactions on Power Electronics, 2013Co-Authors: Tiefu Zhao, Subharshish Bhattacharya, Gangyao Wang, Alex Q. HuangAbstract:The solid-state transformer (SST) is an interface device between ac distribution grids and dc distribution systems. The SST consists of a cascaded multilevel ac/dc rectifier stage, a dual active bridge (DAB) converter stage with high-frequency transformers to provide a regulated 400-V dc distribution, and an optional dc/ac stage that can be connected to the 400-V dc bus to provide residential 120/240 V _{rm ac}. However, due to dc-link voltage and Power unBalance in the cascaded modules, the unBalanced dc-link voltages and Power increase the stress of the semiconductor devices and cause overvoltage or overcurrent issues. This paper proposes a new voltage and Power Balance control for the cascaded H-Bridge converter-based SST. Based on the single-phase dq model, a novel voltage and the Power control strategy is proposed to Balance the rectifier capacitor voltages and the real Power through parallel DAB modules. Furthermore, the intrinsic Power constraints of the cascaded H-Bridge voltage Balance control are derived and analyzed. With the proposed control methods, the dc-link voltage and the real Power through each module can be Balanced. The SST switching model simulation and the prototype experiments are presented to verify the performance of the proposed voltage and Power Balance controller.
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Research on voltage and Power Balance control for cascaded modular solid-state transformer
IEEE Transactions on Power Electronics, 2011Co-Authors: Jianjiang Shi, Wei Gou, Tiefu Zhao, Hao Yuan, Alex Q. HuangAbstract:The solid-state transformer (SST) is one of the key elements in Power electronic-based microgrid systems. The single-phase SST consists of a modular multilevel ac–dc rectifier, a modular dual active bridge (DAB) dc–dc converter with high-frequency transformers, and a dc–ac inverter stage. However, due to dc bus voltage and Power unbalancing in each module, the modular SST often presents instability problems making its design difficult and causing unpredictable behavior. Moreover, the unBalanced dc-link voltages increase the stress of the semiconductor devices, and also cause high harmonic distortions of grid current, therefore, necessitating the use of a bigger ac filter. This paper presents a novel single-phase d–q vector-based common-duty-ratio control method for the multilevel rectifier, and a voltage feedforward and feedback based controller for the modular DAB converter. With the proposed control methods, the dc-link voltage and Power in each module can be Balanced. In addition, the low-distortion grid current, unity Power factor, and bidirectional Power flow can be achieved. Simulation and experimental results are presented to validate the proposed control methods.
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voltage and Power Balance control for a cascaded multilevel solid state transformer
Applied Power Electronics Conference, 2010Co-Authors: Tiefu Zhao, Gangyao Wang, Jie Zeng, Sumit Dutta, Subhashish Bhattacharya, Alex Q. HuangAbstract:In this paper, a 20kVA Solid State Transformer (SST) based on 6.5kV IGBT is proposed for interface with 7.2kV distribution system voltage. The proposed SST consists of a cascaded multilevel AC/DC rectifier stage, a Dual Active Bridge (DAB) converter stage with high frequency transformers and a DC/AC inverter stage. Based on the single phase d-q vector control, a novel control strategy is proposed to Balance the rectifier capacitor voltages and the real Power through the DAB parallel modules. Furthermore, the Power constraints of the voltage Balance control are analyzed. The SST switching model simulation demonstrates the effectiveness of the proposed voltage and Power Balance controller. A 3kW SST scale-down prototype is implemented. The experiment results verify the single phase d-q vector controller for the SST cascaded multilevel rectifier.
Vassilios G Agelidis - One of the best experts on this subject based on the ideXlab platform.
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Power Balance optimization of cascaded h bridge multilevel converters for large scale photovoltaic integration
IEEE Transactions on Power Electronics, 2016Co-Authors: Yifan Yu, Georgios Konstantinou, Branislav Hredzak, Vassilios G AgelidisAbstract:Multilevel-cascaded H-bridge converters are promising candidates for next generation photovoltaic Power converters. They feature reduced switching losses and higher conversion efficiency with modular structure; characteristics vital for large-scale photovoltaic Power plants. However, the stochastically-variable nature of irradiance levels and ambient temperatures affects the normal operation of this topology, because Power levels in the three phases can be unequal. The existing zero sequence injection method can deal with the Power imBalance problem, but it is limited in its application. The paper proposes a zero sequence injection method to optimize the converter Power Balance, extending the converter operation with severe Power imBalance. Based on the proposed optimal method, a simplified optimal zero sequence injection method requiring less calculation effort is derived and compared with the optimal method. Simulation and experimental results validate the effectiveness and feasibility of the proposed methods.
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Power Balance of cascaded h bridge multilevel converters for large scale photovoltaic integration
IEEE Transactions on Power Electronics, 2016Co-Authors: Yifan Yu, Georgios Konstantinou, Branislav Hredzak, Vassilios G AgelidisAbstract:Multilevel cascaded H-bridge converters are promising candidates for large-scale photovoltaic Power plants. They allow direct connection to medium-voltage distribution networks without the presence of bulky line frequency Power transformers. Owing to the stochastically variable nature of irradiance level, ambient temperature, and other factors, Power levels in the three phases are expected to be unequal. The Power imBalance condition creates unexpected problems with this topology, which was initially designed to operate under Balanced Power conditions. To deal with this issue, the paper proposes three novel zero-sequence injection methods as an expansion to the conventional zero-sequence injection method. Results obtained from simulations and a 430-V 8-kW three-phase seven-level cascaded H-bridge prototype are presented to verify the effectiveness and feasibility of the proposed methods.
Tiefu Zhao - One of the best experts on this subject based on the ideXlab platform.
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Voltage and Power Balance control for a cascaded h-bridge converter-based solid-state Transformer
IEEE Transactions on Power Electronics, 2013Co-Authors: Tiefu Zhao, Subharshish Bhattacharya, Gangyao Wang, Alex Q. HuangAbstract:The solid-state transformer (SST) is an interface device between ac distribution grids and dc distribution systems. The SST consists of a cascaded multilevel ac/dc rectifier stage, a dual active bridge (DAB) converter stage with high-frequency transformers to provide a regulated 400-V dc distribution, and an optional dc/ac stage that can be connected to the 400-V dc bus to provide residential 120/240 V _{rm ac}. However, due to dc-link voltage and Power unBalance in the cascaded modules, the unBalanced dc-link voltages and Power increase the stress of the semiconductor devices and cause overvoltage or overcurrent issues. This paper proposes a new voltage and Power Balance control for the cascaded H-Bridge converter-based SST. Based on the single-phase dq model, a novel voltage and the Power control strategy is proposed to Balance the rectifier capacitor voltages and the real Power through parallel DAB modules. Furthermore, the intrinsic Power constraints of the cascaded H-Bridge voltage Balance control are derived and analyzed. With the proposed control methods, the dc-link voltage and the real Power through each module can be Balanced. The SST switching model simulation and the prototype experiments are presented to verify the performance of the proposed voltage and Power Balance controller.
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Research on voltage and Power Balance control for cascaded modular solid-state transformer
IEEE Transactions on Power Electronics, 2011Co-Authors: Jianjiang Shi, Wei Gou, Tiefu Zhao, Hao Yuan, Alex Q. HuangAbstract:The solid-state transformer (SST) is one of the key elements in Power electronic-based microgrid systems. The single-phase SST consists of a modular multilevel ac–dc rectifier, a modular dual active bridge (DAB) dc–dc converter with high-frequency transformers, and a dc–ac inverter stage. However, due to dc bus voltage and Power unbalancing in each module, the modular SST often presents instability problems making its design difficult and causing unpredictable behavior. Moreover, the unBalanced dc-link voltages increase the stress of the semiconductor devices, and also cause high harmonic distortions of grid current, therefore, necessitating the use of a bigger ac filter. This paper presents a novel single-phase d–q vector-based common-duty-ratio control method for the multilevel rectifier, and a voltage feedforward and feedback based controller for the modular DAB converter. With the proposed control methods, the dc-link voltage and Power in each module can be Balanced. In addition, the low-distortion grid current, unity Power factor, and bidirectional Power flow can be achieved. Simulation and experimental results are presented to validate the proposed control methods.
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voltage and Power Balance control for a cascaded multilevel solid state transformer
Applied Power Electronics Conference, 2010Co-Authors: Tiefu Zhao, Gangyao Wang, Jie Zeng, Sumit Dutta, Subhashish Bhattacharya, Alex Q. HuangAbstract:In this paper, a 20kVA Solid State Transformer (SST) based on 6.5kV IGBT is proposed for interface with 7.2kV distribution system voltage. The proposed SST consists of a cascaded multilevel AC/DC rectifier stage, a Dual Active Bridge (DAB) converter stage with high frequency transformers and a DC/AC inverter stage. Based on the single phase d-q vector control, a novel control strategy is proposed to Balance the rectifier capacitor voltages and the real Power through the DAB parallel modules. Furthermore, the Power constraints of the voltage Balance control are analyzed. The SST switching model simulation demonstrates the effectiveness of the proposed voltage and Power Balance controller. A 3kW SST scale-down prototype is implemented. The experiment results verify the single phase d-q vector controller for the SST cascaded multilevel rectifier.
Xijun Ni - One of the best experts on this subject based on the ideXlab platform.
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Current sensorless Power Balance strategy for DC/DC converters in a cascaded multilevel converter based solid state transformer
IEEE Transactions on Power Electronics, 2014Co-Authors: Xu She, Alex Q. Huang, Xijun NiAbstract:This letter proposes a current sensorless controller for balancing the Power in the dc/dc stage of a cascaded multilevel converter based solid state transformer. It is revealed that the equalization of the active Power component of duty cycles in the cascaded multilevel rectifier stage can be a good indicator of Power Balance in the dc/dc stage. Additionally, the Power Balance of the dc/dc stage can guarantee the voltage Balance in the rectifier stage if the differences among the Power devices are negligible. Based on this principle, a novel Power Balance controller without sensing any current in the dc/dc stage is proposed. In the end, experimental results in a seven-level three-stage solid state transformer are provided for verifying the proposed method.
Yifan Yu - One of the best experts on this subject based on the ideXlab platform.
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Power Balance optimization of cascaded h bridge multilevel converters for large scale photovoltaic integration
IEEE Transactions on Power Electronics, 2016Co-Authors: Yifan Yu, Georgios Konstantinou, Branislav Hredzak, Vassilios G AgelidisAbstract:Multilevel-cascaded H-bridge converters are promising candidates for next generation photovoltaic Power converters. They feature reduced switching losses and higher conversion efficiency with modular structure; characteristics vital for large-scale photovoltaic Power plants. However, the stochastically-variable nature of irradiance levels and ambient temperatures affects the normal operation of this topology, because Power levels in the three phases can be unequal. The existing zero sequence injection method can deal with the Power imBalance problem, but it is limited in its application. The paper proposes a zero sequence injection method to optimize the converter Power Balance, extending the converter operation with severe Power imBalance. Based on the proposed optimal method, a simplified optimal zero sequence injection method requiring less calculation effort is derived and compared with the optimal method. Simulation and experimental results validate the effectiveness and feasibility of the proposed methods.
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Power Balance of cascaded h bridge multilevel converters for large scale photovoltaic integration
IEEE Transactions on Power Electronics, 2016Co-Authors: Yifan Yu, Georgios Konstantinou, Branislav Hredzak, Vassilios G AgelidisAbstract:Multilevel cascaded H-bridge converters are promising candidates for large-scale photovoltaic Power plants. They allow direct connection to medium-voltage distribution networks without the presence of bulky line frequency Power transformers. Owing to the stochastically variable nature of irradiance level, ambient temperature, and other factors, Power levels in the three phases are expected to be unequal. The Power imBalance condition creates unexpected problems with this topology, which was initially designed to operate under Balanced Power conditions. To deal with this issue, the paper proposes three novel zero-sequence injection methods as an expansion to the conventional zero-sequence injection method. Results obtained from simulations and a 430-V 8-kW three-phase seven-level cascaded H-bridge prototype are presented to verify the effectiveness and feasibility of the proposed methods.
