EPE Association: EPE 2014 - DS1f: Wind Energy Systems

EPE 2014 - DS1f: Wind Energy Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 05: Renewable Energy Power Systems > EPE 2014 - DS1f: Wind Energy Systems

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   A High Efficient Medium Voltage Step-up DC/DC Converter with Zero Voltage Switching (ZVS) and Low Voltage Stress for Offshore Wind Energy Systems
By John LAM, Praveen K. JAIN [View]
[Download]

Abstract: Conventional wind farms have a medium voltage AC (MVAC) grid that collects the power from the individual wind turbines and one or two transformer substations that facilitate high voltage AC (HVAC) power transmission. Since the output voltage of a wind turbine is too low for effective power transmission, it is stepped-up to a medium voltage level through individual transformers to facilitate short distance power transmission to the substation for further voltage boost. The AC transformers are bulky and typically located in the immediate vicinity of the turbines and in off-shore wind farms, marginally rated transformers are usually installed in the turbines nacelle. In order to provide efficient long distance power transmission from the wind farms, HVAC links are now being replaced by high voltage DC (HVDC) links where the bulky transformers are replaced by DC/DC step-up converters. In this paper, a new medium voltage step-up resonant DC/DC converter is proposed for high power wind turbines in offshore wind energy systems. The proposed converter features zero voltage switching and low voltage stress across the power transistors. Four strings of switch pairs are connected in series in the proposed converter so that the voltage stress across each power transistor is equal to only a quarter of the input DC voltage. The circuits operating principles will be discussed in this paper. Simulation results and experimental results on a proof-of-concept prototype are provided to highlight the merits of the proposed converter.

   A simple direct power control of a three-phase inverter for a grid-connected wind energy system
By CHAROULA ZOGOGIANNI, EMMANUEL TATAKIS [View]
[Download]

Abstract: In this paper, a simple direct power control (DPC) for a three-phase inverter, used in a wind energy system, is presented. The inverter is connected to the grid through a LC filter and an isolating transformer. The proposed control algorithm involves independent active and reactive power controllers. Simulation and experimental results prove the simplicity and the effectiveness of the proposed control.

   Comparison of the Power Cycling Stress of IGBT in DFIG and Full Size Converter for Windenergy Applications
By David WEISS, Hans-Günter ECKEL [View]
[Download]

Abstract: In this paper the power cycling stress of the power semiconductors in wind energy applications for twocommon generator concepts (DFIG and gearless synchronous machine) will be investigated. The aim isto show how the chosen generator concept influences the power cycling stress of the power semiconductors. For the investigation regarding power cycling stress and estimated lifetime a wind speed profile of one month measured at the FINO 1 station in the German North Sea was used. With this it is possible to consider the power cycling stress caused by the output frequency of the generator as well as the power cycling stress caused by the cycles due to wind speed variations.

   Comparison of Three Phase Rectifier Topologies applied to Small Wind Turbines
By Kristina BUCHERT, Friedrich Wilhelm FUCHS [View]
[Download]

Abstract: Small wind turbines are used for local energy production or in island networks. They are usually installed at places, where the wind speed is relatively low and considerable fluctuation occurs, resulting in a challenge to offer a high energy production especially at low and gusty wind speeds. For these conditions an optimal drive train has to be selected. In this paper the focus is on typical rectifier topologies applied to small wind turbines as a part of the drive train. Therefore, five rectifier topologies are analyzed and compared concerning relevant comparison factors: DC link voltage and current, the losses (efficiency) based on a virtual power semiconductor, the costs, the volume, the performance of the machine side currents and power vs. generator speed characteristics. The aim is to show with a help of a ranking method, which topology is the best due to the decided criteria.

   Design of Series-Connected Dual-Active Bridges for Integration of Wind Park Cluster into MVDC Grids
By Marco STIENEKER, Jan RIEDEL, Nils SOLTAU, Hanno STAGGE, Rik DE DONCKER [View]
[Download]

Abstract: The transmission of electrical energy with direct current (dc) is a promising alternative to alternatingcurrent (ac) systems. The collection of energy with medium-voltage dc (MVDC) grids also increases the efficiency. In this paper, a dual-active bridge (DAB) dc-dc converter system for integrating wind turbines (WT) into MVDC grids is presented. Within this approach, the secondary-side bridges are series connected whereas the primary-side bridges are not connected with each other. This provides galvanic isolation between the WT.

   Modular Multilevel Converter Solutions with few Sub-Modules for Wind Power Application
By Liudmila POPOVA, Ke MA, Frede BLAABJERG, Juha PYRHÖNEN [View]
[Download]

Abstract: Modular Multilevel Converter (MMC) is a topology where series connection of Sub-Modules (SM) is used to achieve almost sinusoidal output voltage. The MMC converter with a large number of SMs is actively used in high voltage DC (HVDC) transmission systems where a bulky converter is not a difficult issue. In this paper the possibility to use a MMC with just a few SMs for wind power application with limited space in the nacelle is analysed. The current loading, electrical losses and thermal performance of the power devices in the converter solutions studied are analysed. It is shown that an MMC converter with full-bridge (FB) SMs has a more uniform loss and temperature distribution among the semiconductor devices than an MMC with half-bridge (HB) SMs. The reliability of the MMC converters is also investigated in terms of thermal loading.

   Power processing limits of offshore wind turbine systems based on thermal stress
By Sumitha MOHAN, RAJENDRA NAIK [View]
[Download]

Abstract: Entitlement of the power handling capability with appropriate semiconductor devices and switching frequencies is necessary to determine the feasibility (from a cost and reliability standpoint) of high power (~ 4MW or higher) medium voltage offshore wind turbine systems. In this paper, the power conversion system of a back-to-back three phase Neutral Point Clamped (NPC) converter fed by a Permanent Magnet Synchronous Generator (PMSG) is investigated for an offshore wind turbine at the 6-8 MW power level. The objective is to ascertain the power processing capability of the back-to-back converter system with specific medium voltage semiconductor devices (press pack Insulated Gate Bipolar Transistors (IGBT), Integrated Gate Commutated Thyristor (IGCT) and Injection Enhanced Gate Transistors (IEGT)) for typical power factor requirements of 0.9 to unity at the grid. Detailed thermal device models are used for an analysis of individual component losses and overall system efficiency to determine allowable switching frequencies for these power semiconductor devices.

   The Pitch Angle Control of Squirrel-cage Induction Generator (SCIG) Wind Power Generation System Using Sliding Mode Control via reaching law
By Mi YANG, Bao XIAOWEI, Jiang ENYU, Deng WEIHUA, Li JIANXIN, Wang LIMIN, Ren LUFEI, Wang PENG, En yu JIANG [View]
[Download]

Abstract: The pitch angle controller is designed for SCIG wind power system by using sliding mode control tolevel the output power of wind turbine generation (WTG) at the rated power. The WTG system modelis established by using small signal method. Then the pitch angle control system is designed based onthe sliding mode control via reaching law. At last, the simulations are given by matlab softwarecomparing with other two PID control method, the simulation results show that the proposedcontroller has more robustness and little deviation.

EPE 2014 - DS1f: Wind Energy Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 05: Renewable Energy Power Systems > EPE 2014 - DS1f: Wind Energy Systems
	[return to parent folder]

	A High Efficient Medium Voltage Step-up DC/DC Converter with Zero Voltage Switching (ZVS) and Low Voltage Stress for Offshore Wind Energy Systems By John LAM, Praveen K. JAIN	[View] [Download]
Abstract: Conventional wind farms have a medium voltage AC (MVAC) grid that collects the power from the individual wind turbines and one or two transformer substations that facilitate high voltage AC (HVAC) power transmission. Since the output voltage of a wind turbine is too low for effective power transmission, it is stepped-up to a medium voltage level through individual transformers to facilitate short distance power transmission to the substation for further voltage boost. The AC transformers are bulky and typically located in the immediate vicinity of the turbines and in off-shore wind farms, marginally rated transformers are usually installed in the turbines nacelle. In order to provide efficient long distance power transmission from the wind farms, HVAC links are now being replaced by high voltage DC (HVDC) links where the bulky transformers are replaced by DC/DC step-up converters. In this paper, a new medium voltage step-up resonant DC/DC converter is proposed for high power wind turbines in offshore wind energy systems. The proposed converter features zero voltage switching and low voltage stress across the power transistors. Four strings of switch pairs are connected in series in the proposed converter so that the voltage stress across each power transistor is equal to only a quarter of the input DC voltage. The circuits operating principles will be discussed in this paper. Simulation results and experimental results on a proof-of-concept prototype are provided to highlight the merits of the proposed converter.

	A simple direct power control of a three-phase inverter for a grid-connected wind energy system By CHAROULA ZOGOGIANNI, EMMANUEL TATAKIS	[View] [Download]
Abstract: In this paper, a simple direct power control (DPC) for a three-phase inverter, used in a wind energy system, is presented. The inverter is connected to the grid through a LC filter and an isolating transformer. The proposed control algorithm involves independent active and reactive power controllers. Simulation and experimental results prove the simplicity and the effectiveness of the proposed control.

	Comparison of the Power Cycling Stress of IGBT in DFIG and Full Size Converter for Windenergy Applications By David WEISS, Hans-Günter ECKEL	[View] [Download]
Abstract: In this paper the power cycling stress of the power semiconductors in wind energy applications for twocommon generator concepts (DFIG and gearless synchronous machine) will be investigated. The aim isto show how the chosen generator concept influences the power cycling stress of the power semiconductors. For the investigation regarding power cycling stress and estimated lifetime a wind speed profile of one month measured at the FINO 1 station in the German North Sea was used. With this it is possible to consider the power cycling stress caused by the output frequency of the generator as well as the power cycling stress caused by the cycles due to wind speed variations.

	Comparison of Three Phase Rectifier Topologies applied to Small Wind Turbines By Kristina BUCHERT, Friedrich Wilhelm FUCHS	[View] [Download]
Abstract: Small wind turbines are used for local energy production or in island networks. They are usually installed at places, where the wind speed is relatively low and considerable fluctuation occurs, resulting in a challenge to offer a high energy production especially at low and gusty wind speeds. For these conditions an optimal drive train has to be selected. In this paper the focus is on typical rectifier topologies applied to small wind turbines as a part of the drive train. Therefore, five rectifier topologies are analyzed and compared concerning relevant comparison factors: DC link voltage and current, the losses (efficiency) based on a virtual power semiconductor, the costs, the volume, the performance of the machine side currents and power vs. generator speed characteristics. The aim is to show with a help of a ranking method, which topology is the best due to the decided criteria.

	Design of Series-Connected Dual-Active Bridges for Integration of Wind Park Cluster into MVDC Grids By Marco STIENEKER, Jan RIEDEL, Nils SOLTAU, Hanno STAGGE, Rik DE DONCKER	[View] [Download]
Abstract: The transmission of electrical energy with direct current (dc) is a promising alternative to alternatingcurrent (ac) systems. The collection of energy with medium-voltage dc (MVDC) grids also increases the efficiency. In this paper, a dual-active bridge (DAB) dc-dc converter system for integrating wind turbines (WT) into MVDC grids is presented. Within this approach, the secondary-side bridges are series connected whereas the primary-side bridges are not connected with each other. This provides galvanic isolation between the WT.

	Modular Multilevel Converter Solutions with few Sub-Modules for Wind Power Application By Liudmila POPOVA, Ke MA, Frede BLAABJERG, Juha PYRHÖNEN	[View] [Download]
Abstract: Modular Multilevel Converter (MMC) is a topology where series connection of Sub-Modules (SM) is used to achieve almost sinusoidal output voltage. The MMC converter with a large number of SMs is actively used in high voltage DC (HVDC) transmission systems where a bulky converter is not a difficult issue. In this paper the possibility to use a MMC with just a few SMs for wind power application with limited space in the nacelle is analysed. The current loading, electrical losses and thermal performance of the power devices in the converter solutions studied are analysed. It is shown that an MMC converter with full-bridge (FB) SMs has a more uniform loss and temperature distribution among the semiconductor devices than an MMC with half-bridge (HB) SMs. The reliability of the MMC converters is also investigated in terms of thermal loading.

	Power processing limits of offshore wind turbine systems based on thermal stress By Sumitha MOHAN, RAJENDRA NAIK	[View] [Download]
Abstract: Entitlement of the power handling capability with appropriate semiconductor devices and switching frequencies is necessary to determine the feasibility (from a cost and reliability standpoint) of high power (~ 4MW or higher) medium voltage offshore wind turbine systems. In this paper, the power conversion system of a back-to-back three phase Neutral Point Clamped (NPC) converter fed by a Permanent Magnet Synchronous Generator (PMSG) is investigated for an offshore wind turbine at the 6-8 MW power level. The objective is to ascertain the power processing capability of the back-to-back converter system with specific medium voltage semiconductor devices (press pack Insulated Gate Bipolar Transistors (IGBT), Integrated Gate Commutated Thyristor (IGCT) and Injection Enhanced Gate Transistors (IEGT)) for typical power factor requirements of 0.9 to unity at the grid. Detailed thermal device models are used for an analysis of individual component losses and overall system efficiency to determine allowable switching frequencies for these power semiconductor devices.

	The Pitch Angle Control of Squirrel-cage Induction Generator (SCIG) Wind Power Generation System Using Sliding Mode Control via reaching law By Mi YANG, Bao XIAOWEI, Jiang ENYU, Deng WEIHUA, Li JIANXIN, Wang LIMIN, Ren LUFEI, Wang PENG, En yu JIANG	[View] [Download]
Abstract: The pitch angle controller is designed for SCIG wind power system by using sliding mode control tolevel the output power of wind turbine generation (WTG) at the rated power. The WTG system modelis established by using small signal method. Then the pitch angle control system is designed based onthe sliding mode control via reaching law. At last, the simulations are given by matlab softwarecomparing with other two PID control method, the simulation results show that the proposedcontroller has more robustness and little deviation.