EPE Association: EPE 2018 - LS5d: HVDC and FACTS

EPE 2018 - LS5d: HVDC and FACTS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 06: Grids, Smart Grids, AC & DC > EPE 2018 - LS5d: HVDC and FACTS

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   Analysis of the Hybrid Arm Modular Multilevel Converter in DC Fault Blocking State and Post-Fault Condition
By Hossein IMANEINI [View]
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Abstract: A hybrid arm MMC with half-bridge arms close to the grounding pole and full-bridge arms away fromthe grounding pole is studied. Different operating modes of the converter in dc fault blocking state areexplained. For each operating mode, the differential equation of fault current is derived. Then, thesufficient condition for blocking the fault current is extracted. Also, a mathematical formula isintroduced for the estimation of maximum blocking time. Finally, the STATCOM operation in thefault period and smooth voltage build-up capability of the hybrid arm MMC are explained. Alltheoretical claims and the converter behavior are verified by simulations.

   Analysis of the Lower Limit of Allowable Energy in Modular Multilevel Converters
By Kosei SHINODA [View]
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Abstract: The operation of Modular Multilevel Converter (MMC) relies on the storage of a certain amount of the energy in the stacked sub-modules (SMs). With appropriate control, this internally stored energy provides an additional degree of freedom, which does not exist in conventional Voltage Source Converters (VSCs). However, due to the internal energy pulsations and their strong non-linearity, the minimum required amount of this energy to ensure its proper operation had not been fully understood. In this paper, a thorough analysis of the converter arm behavior is presented, which gives an analytic expression of the lower limit of the energy as a function of the converter operating point and the connected grid conditions. The relation between the lower energy limit and the operating power is analyzed by using the practical MMC specifications of an HVDC application. An experimental test of a small-scale MMC mock-up demonstrates the validity of the theoretical analysis.

   DC-link voltage modulation for individual capacitor voltage balancing in cascaded H-bridge STATCOM at zero current mode
By Ehsan BEHROUZIAN [View]
[Download]

Abstract: Individual capacitor voltage balancing of cascaded H-Bridge converters is one of the challenges in the field of multilevel converters, especially when the converter is operating at zero-current mode. This is due to the fact that the balancing algorithm requires information about the power direction for proper insertion of the different cells of the converter. In case of delta configuration of the phase-legs of the converter, a circulating current inside the delta can be used for balancing purposes. However, this approach can not be used for the star configuration. Focusing on the star, this paper first highlights the issue related to the capacitor voltage balancing at zero-current mode and second proposes a novel method to overcome this problem. The proposed method is based on modulation of the DC-link voltages. The method provides a small amount of current flow during the zero-current mode operation. This current enables the sorting algorithm to provide an appropriate individual balancing. The proposed method is applied to a 7-level star connected cascaded H-Bridge STATCOM modeled in PSCAD and simulation results show the effectiveness of the proposed method in balancing the capacitors voltages when no current is exchanged with the grid. Finally the proposed method is experimentally verified through a down-scaled laboratory set-up.

   The Controlled Transition Bridge: Analysis and Benchmarking for the HVDC VSC Market
By Pablo BRIFF [View]
[Download]

Abstract: This paper introduces the technical and commercial benefits of the Controlled Transition Bridge (CTB), a hybrid HVDC topology combining thyristor and IGBT valves. CTB offers independent operation in the P-Q envelope with AC/DC fault blocking capabilities. A commercial benchmarking of the topology is presented, which shows that CTB outperforms Full-Bridge MMC for the HVDC VSC DC fault-blocking market.

EPE 2018 - LS5d: HVDC and FACTS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 06: Grids, Smart Grids, AC & DC > EPE 2018 - LS5d: HVDC and FACTS
	[return to parent folder]

	Analysis of the Hybrid Arm Modular Multilevel Converter in DC Fault Blocking State and Post-Fault Condition By Hossein IMANEINI	[View] [Download]
Abstract: A hybrid arm MMC with half-bridge arms close to the grounding pole and full-bridge arms away fromthe grounding pole is studied. Different operating modes of the converter in dc fault blocking state areexplained. For each operating mode, the differential equation of fault current is derived. Then, thesufficient condition for blocking the fault current is extracted. Also, a mathematical formula isintroduced for the estimation of maximum blocking time. Finally, the STATCOM operation in thefault period and smooth voltage build-up capability of the hybrid arm MMC are explained. Alltheoretical claims and the converter behavior are verified by simulations.

	Analysis of the Lower Limit of Allowable Energy in Modular Multilevel Converters By Kosei SHINODA	[View] [Download]
Abstract: The operation of Modular Multilevel Converter (MMC) relies on the storage of a certain amount of the energy in the stacked sub-modules (SMs). With appropriate control, this internally stored energy provides an additional degree of freedom, which does not exist in conventional Voltage Source Converters (VSCs). However, due to the internal energy pulsations and their strong non-linearity, the minimum required amount of this energy to ensure its proper operation had not been fully understood. In this paper, a thorough analysis of the converter arm behavior is presented, which gives an analytic expression of the lower limit of the energy as a function of the converter operating point and the connected grid conditions. The relation between the lower energy limit and the operating power is analyzed by using the practical MMC specifications of an HVDC application. An experimental test of a small-scale MMC mock-up demonstrates the validity of the theoretical analysis.

	DC-link voltage modulation for individual capacitor voltage balancing in cascaded H-bridge STATCOM at zero current mode By Ehsan BEHROUZIAN	[View] [Download]
Abstract: Individual capacitor voltage balancing of cascaded H-Bridge converters is one of the challenges in the field of multilevel converters, especially when the converter is operating at zero-current mode. This is due to the fact that the balancing algorithm requires information about the power direction for proper insertion of the different cells of the converter. In case of delta configuration of the phase-legs of the converter, a circulating current inside the delta can be used for balancing purposes. However, this approach can not be used for the star configuration. Focusing on the star, this paper first highlights the issue related to the capacitor voltage balancing at zero-current mode and second proposes a novel method to overcome this problem. The proposed method is based on modulation of the DC-link voltages. The method provides a small amount of current flow during the zero-current mode operation. This current enables the sorting algorithm to provide an appropriate individual balancing. The proposed method is applied to a 7-level star connected cascaded H-Bridge STATCOM modeled in PSCAD and simulation results show the effectiveness of the proposed method in balancing the capacitors voltages when no current is exchanged with the grid. Finally the proposed method is experimentally verified through a down-scaled laboratory set-up.

	The Controlled Transition Bridge: Analysis and Benchmarking for the HVDC VSC Market By Pablo BRIFF	[View] [Download]
Abstract: This paper introduces the technical and commercial benefits of the Controlled Transition Bridge (CTB), a hybrid HVDC topology combining thyristor and IGBT valves. CTB offers independent operation in the P-Q envelope with AC/DC fault blocking capabilities. A commercial benchmarking of the topology is presented, which shows that CTB outperforms Full-Bridge MMC for the HVDC VSC DC fault-blocking market.