EPE Association: EPE 2014 - DS2h: Power Electronics in Transmission and Distribution Systems; HVDC FACT's

EPE 2014 - DS2h: Power Electronics in Transmission and Distribution Systems; HVDC FACT's
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 06: Grids and Smart Grids > EPE 2014 - DS2h: Power Electronics in Transmission and Distribution Systems; HVDC FACT's

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   A General Analytical Loss Calculation Method of Cascaded H-bridge Multilevel STATCOM Converters
By NAN CHEN, Liwei WANG, Mauro MONGE [View]
[Download]

Abstract: A general analytical loss calculation method for cascaded H-bridge multilevel converter is proposed in the paper. Different from traditional averaged switching frequency approach, the loss difference between converter operating in capacitive mode and inductive mode will be reflected by the proposed method. The proposed method is generic and valid for different modulation methods covering phase-shifted and level-shifted multicarrier modulation. Analytical result by the proposed method is verified by detailed equivalent model based on Matlab circuit simulation.

   Average loss calculation and efficiency of a new HVDC auto transformer
By Andre SCHOEN, Mark BAKRAN [View]
[Download]

Abstract: For the upcoming need to transfer bulk power over long onshore distances, HVDC power transmission is the preferred choice. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, that still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation losses, and high investment costs. In this paper the conversion efficiency of the new HVDC auto transformer is compared to the conventional two stage topology with a full AC link.

   DC Current Suppression Circuit in HVDC Power Transmission System
By Sungmin KIM, Jaejung JUNG, Shenghui CUI, Seung-Ki SUL [View]
[Download]

Abstract: To increase the popularity of HVDC power transmission system, the Multi-Terminal Direct Current (MTDC) power transmission system is expected to be installed. Since the Voltage Source Converter HVDC (VSC-HVDC) is available, the MTDC systems are much more likely to be installed soon. However, an efficient Direct Current blocking measure such as DC circuit breaker remains as the most critical hurdle to implement MTDC system. In this paper, a new DC current suppression circuit is proposed. This circuit is a kind of the semiconductor DC circuit breaker, and can be used for very quickly interrupting the DC current against the short circuit fault condition at the cost of minimum conduction loss at the normal operation. Because of the modular configuration, the proposed circuit has inherent redundancy and no need of the series-connection of the semiconductor switches and bulky surge voltage arrestor bank.

   Earth currents in HVDC grids: an example based on 5 terminal bipolar configurations
By Erik BERNE, Gilbert BERGNA, Philippe EGROT, Quentin WOLFF [View]
[Download]

Abstract: With the rapid development of Voltage Source Converters and the recent progresses for DC fault management through DC breakers or inherent fault limiting converters, HVDC has become more and more attractive to grid operators and the possibility of a DC grid layer superimposed to the AC grid is gaining ground. Still, a lot of questions remain concerning the appropriate operation of such a grid. One question that has only attracted limited interest is the possibility of ground currents circulating between stations of the grid. The current levels and the criticity of this question are highly dependent on the topology of these hypothetical DC grids and theirs modes of operation. Still, the environmental and legal issues associated with ground currents as well justify the need to study this aspect as well as the mission profile information required for the proper HVDC station electrode design. The aim of this document is to provide illustration of ground current circulation in the case of bipolar HVDC grids with 5-terminal meshed and radial examples. The influence of the mode of operation of the grid is studied, in the transient case with a DC-fault and in the permanent case of operation with a faulted pole. The influence of the impedance connection to ground is illustrated with both high and low resistance cases. Finally, the possibility of using a pole voltage balancing control unit is investigated and its limits are demonstrated, showing the need for a supervision unit or an enhanced local ground current control.

   Implementation of a Modular Customer-end Inverter for a Low Voltage DC Distribution Network
By Aleksi MATTSSON, Pasi NUUTINEN, Tero KAIPIA, Pasi PELTONIEMI, Pertti SILVENTOINEN, Jarmo PARTANEN [View]
[Download]

Abstract: In this paper the implementation of a modular customer-end inverter (CEI) for a low voltage DC (LVDC) distribution network is discussed. Selection of the nominal power of one inverter module, the effect of the switching frequency and input DC voltage on the lifetime cost is studied. The design goal is set for minimum lifetime cost of the inverter and therefore, investment cost and losses are studied. A load profile of a typical customer group that would be connected to the LVDC distribution network is used in the loss calculation to determine a better approximation of the losses of the system in a real world application and how this affects the design.

   Investigation of negative sequence injection capability in H-bridge Multilevel STATCOM
By EHSAN BEHROUZIAN, MASSIMO BONGIORNO, HECTOR ZELAYA DE LA PARRA [View]
[Download]

Abstract: The aim of this paper is to investigate the ability of star- and delta-connected H-bridge multilevelSTATCOMs to exchange negative-sequence current with the grid. Zero-sequence injection is utilizedfor capacitor voltage balancing. It is shown that a singularity for these configurations exists, leading tolimitations in the utilization of the compensator for asymmetry compensation purposes.

   MAIN REACTOR CONCEPT A COST AND PERFORMANCE EFFICIENT SVC
By Jarmo AHO, Antero KÄHKÖNEN, Neil THOMSON, Kare KAASALAINEN [View]
[Download]

Abstract: Main Reactor Concept for utility SVC represents a patented innovation where a mature system building block (SVC) is modified to be more cost- and performance efficient compared to traditional design. The idea is based on the use of blocking reactor between SVC busbar and substation medium voltage busbar.

   Modular Multilevel DC/DC Converter Architectures for HVDC Taps
By Thomas LUTH, Michael MERLIN, Timothy GREEN [View]
[Download]

Abstract: DC/DC connections between DC voltage levels in High Voltage Direct Current (HVDC) schemes are useful for interconnection between links and as taps to inject/extract relatively small amounts of power. Taps with high voltage transformation ratios (such as 500 kV to 50 kV) are particularly challenging to achieve with reasonable use of semiconductor ratings. Four architectures of DC/DC converter covering both direct connection and transformer-interfaced are analysed and compared in terms of the ratio of their apparent power rating (rated current times rated current summed across all stacks of the cells) to the throughput power. It is found that the direct conversion architectures have reasonable power capacity factor only for low transformation ratios (of 2:1 or less) but the inclusion of a transformer and intermediate square-wave operation allows much wider transformation ratios with a reasonable power capacity factor. For each design the nature of the cell-balancing currents has been determined since this is a major factor in determining the total current flow in each cell stack.

   Parameter Design of Modular Multilevel Converter for DC Fault Ride-Through Capability in Multi-Terminal HVDC System
By Sungmin KIM, Shenghui CUI, Seung-Ki SUL [View]
[Download]

Abstract: The purpose of this paper is to provide the design guide line of the module capacitor, the arm inductor and the DC inductor in Modular Multilevel Converter (MMC). Especially, this design method is proposed for the MMC to have the DC fault ride-through capability in Multi-terminal HVDC system. An MMC system connected to two DC grids and an AC grid is formulated according to the design guide line and the performance of the MMC system has been analyzed through computer simulating. The rationality of the proposed guide line has been confirmed by the simulation results.

EPE 2014 - DS2h: Power Electronics in Transmission and Distribution Systems; HVDC FACT's
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 06: Grids and Smart Grids > EPE 2014 - DS2h: Power Electronics in Transmission and Distribution Systems; HVDC FACT's
	[return to parent folder]

	A General Analytical Loss Calculation Method of Cascaded H-bridge Multilevel STATCOM Converters By NAN CHEN, Liwei WANG, Mauro MONGE	[View] [Download]
Abstract: A general analytical loss calculation method for cascaded H-bridge multilevel converter is proposed in the paper. Different from traditional averaged switching frequency approach, the loss difference between converter operating in capacitive mode and inductive mode will be reflected by the proposed method. The proposed method is generic and valid for different modulation methods covering phase-shifted and level-shifted multicarrier modulation. Analytical result by the proposed method is verified by detailed equivalent model based on Matlab circuit simulation.

	Average loss calculation and efficiency of a new HVDC auto transformer By Andre SCHOEN, Mark BAKRAN	[View] [Download]
Abstract: For the upcoming need to transfer bulk power over long onshore distances, HVDC power transmission is the preferred choice. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, that still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation losses, and high investment costs. In this paper the conversion efficiency of the new HVDC auto transformer is compared to the conventional two stage topology with a full AC link.

	DC Current Suppression Circuit in HVDC Power Transmission System By Sungmin KIM, Jaejung JUNG, Shenghui CUI, Seung-Ki SUL	[View] [Download]
Abstract: To increase the popularity of HVDC power transmission system, the Multi-Terminal Direct Current (MTDC) power transmission system is expected to be installed. Since the Voltage Source Converter HVDC (VSC-HVDC) is available, the MTDC systems are much more likely to be installed soon. However, an efficient Direct Current blocking measure such as DC circuit breaker remains as the most critical hurdle to implement MTDC system. In this paper, a new DC current suppression circuit is proposed. This circuit is a kind of the semiconductor DC circuit breaker, and can be used for very quickly interrupting the DC current against the short circuit fault condition at the cost of minimum conduction loss at the normal operation. Because of the modular configuration, the proposed circuit has inherent redundancy and no need of the series-connection of the semiconductor switches and bulky surge voltage arrestor bank.

	Earth currents in HVDC grids: an example based on 5 terminal bipolar configurations By Erik BERNE, Gilbert BERGNA, Philippe EGROT, Quentin WOLFF	[View] [Download]
Abstract: With the rapid development of Voltage Source Converters and the recent progresses for DC fault management through DC breakers or inherent fault limiting converters, HVDC has become more and more attractive to grid operators and the possibility of a DC grid layer superimposed to the AC grid is gaining ground. Still, a lot of questions remain concerning the appropriate operation of such a grid. One question that has only attracted limited interest is the possibility of ground currents circulating between stations of the grid. The current levels and the criticity of this question are highly dependent on the topology of these hypothetical DC grids and theirs modes of operation. Still, the environmental and legal issues associated with ground currents as well justify the need to study this aspect as well as the mission profile information required for the proper HVDC station electrode design. The aim of this document is to provide illustration of ground current circulation in the case of bipolar HVDC grids with 5-terminal meshed and radial examples. The influence of the mode of operation of the grid is studied, in the transient case with a DC-fault and in the permanent case of operation with a faulted pole. The influence of the impedance connection to ground is illustrated with both high and low resistance cases. Finally, the possibility of using a pole voltage balancing control unit is investigated and its limits are demonstrated, showing the need for a supervision unit or an enhanced local ground current control.

	Implementation of a Modular Customer-end Inverter for a Low Voltage DC Distribution Network By Aleksi MATTSSON, Pasi NUUTINEN, Tero KAIPIA, Pasi PELTONIEMI, Pertti SILVENTOINEN, Jarmo PARTANEN	[View] [Download]
Abstract: In this paper the implementation of a modular customer-end inverter (CEI) for a low voltage DC (LVDC) distribution network is discussed. Selection of the nominal power of one inverter module, the effect of the switching frequency and input DC voltage on the lifetime cost is studied. The design goal is set for minimum lifetime cost of the inverter and therefore, investment cost and losses are studied. A load profile of a typical customer group that would be connected to the LVDC distribution network is used in the loss calculation to determine a better approximation of the losses of the system in a real world application and how this affects the design.

	Investigation of negative sequence injection capability in H-bridge Multilevel STATCOM By EHSAN BEHROUZIAN, MASSIMO BONGIORNO, HECTOR ZELAYA DE LA PARRA	[View] [Download]
Abstract: The aim of this paper is to investigate the ability of star- and delta-connected H-bridge multilevelSTATCOMs to exchange negative-sequence current with the grid. Zero-sequence injection is utilizedfor capacitor voltage balancing. It is shown that a singularity for these configurations exists, leading tolimitations in the utilization of the compensator for asymmetry compensation purposes.

	MAIN REACTOR CONCEPT A COST AND PERFORMANCE EFFICIENT SVC By Jarmo AHO, Antero KÄHKÖNEN, Neil THOMSON, Kare KAASALAINEN	[View] [Download]
Abstract: Main Reactor Concept for utility SVC represents a patented innovation where a mature system building block (SVC) is modified to be more cost- and performance efficient compared to traditional design. The idea is based on the use of blocking reactor between SVC busbar and substation medium voltage busbar.

	Modular Multilevel DC/DC Converter Architectures for HVDC Taps By Thomas LUTH, Michael MERLIN, Timothy GREEN	[View] [Download]
Abstract: DC/DC connections between DC voltage levels in High Voltage Direct Current (HVDC) schemes are useful for interconnection between links and as taps to inject/extract relatively small amounts of power. Taps with high voltage transformation ratios (such as 500 kV to 50 kV) are particularly challenging to achieve with reasonable use of semiconductor ratings. Four architectures of DC/DC converter covering both direct connection and transformer-interfaced are analysed and compared in terms of the ratio of their apparent power rating (rated current times rated current summed across all stacks of the cells) to the throughput power. It is found that the direct conversion architectures have reasonable power capacity factor only for low transformation ratios (of 2:1 or less) but the inclusion of a transformer and intermediate square-wave operation allows much wider transformation ratios with a reasonable power capacity factor. For each design the nature of the cell-balancing currents has been determined since this is a major factor in determining the total current flow in each cell stack.

	Parameter Design of Modular Multilevel Converter for DC Fault Ride-Through Capability in Multi-Terminal HVDC System By Sungmin KIM, Shenghui CUI, Seung-Ki SUL	[View] [Download]
Abstract: The purpose of this paper is to provide the design guide line of the module capacitor, the arm inductor and the DC inductor in Modular Multilevel Converter (MMC). Especially, this design method is proposed for the MMC to have the DC fault ride-through capability in Multi-terminal HVDC system. An MMC system connected to two DC grids and an AC grid is formulated according to the design guide line and the performance of the MMC system has been analyzed through computer simulating. The rationality of the proposed guide line has been confirmed by the simulation results.