EPE Association: EPE 2013 - DS3g: Converters for Rotating and Linear Generators

EPE 2013 - DS3g: Converters for Rotating and Linear Generators
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2013 ECCE Europe - Conference > EPE 2013 - Topic 14: Converters for rotating and linear generators > EPE 2013 - DS3g: Converters for Rotating and Linear Generators

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   A Paradigm Change in Wind Power Station Control through Emulation of Conventional Power Plant Behaviour
By Florian FEIN, Markus SCHMIDT, Holger GROKE, Bernd ORLIK [View]
[Download]

Abstract: With a new control concept presented in this paper, wind power stations with inverter-coupledsynchronous generators (SG-WPS) behave to a great extent like the turbine-generator sets ofconventional thermal power plants including the ability of the release of active- and reactive reservepower. This allows every single SG-WPS to improve its contribution to power grid stability. The newcontrol concept consists of three main subsystems: The control of the grid-side inverter, the control ofthe generator-side inverter and the control of the rotor speed with the pitch angle. This paper points toall named subsystems, but the main focus is on the control of the dc-link voltage of the frequencyinverter. In contrast to conventional control concepts of SG-WPS, where the dc-link voltage isregulated with the grid-side inverter, here it is controlled with the generator-side inverter. This is aparadigm change in wind power station control. Without the task of dc-link voltage control, the grid-sideinverter of the SG-WPS is operated with droop based virtual synchronous machine emulation. Itallows the SG-WPS to immediately react to grid disturbances by the release of active- and reactivereserve power. This is an important step in the conversion of a WPS from a “negative consumer” to avoltage source. Simulation results show the dynamic behaviour of the SG-WPS with the new controlconcept as a whole. A test bench and experimental results for the dc-link voltage control with thegenerator-side inverter will be presented.

   Advanced Modeling of a Doubly Fed Induction Generator with open Statorfor soft Grid Synchronization
By Christian MEHLER, Guido TISBORN, Holger GROKE, Bernd ORLIK [View]
[Download]

Abstract: This paper presents a new, extended flux model of the doubly fed induction generator (DFIG). Thisextended flux model describes the operation at no-load with open stator connections, as well as theoperation when connected to the grid. With this model, it is possible to simulate the softsynchronization of the DFIG to the grid. Also the synchronization process itself is modified using thenew flux model. This paper presents simulations of the new flux model and the synchronizationprocedure. Measurements at a test bench complete the paper.

   Comparative investigation and improvement of wind farms based on wind energy conversion and grid connection methodsS121201F
By Georgios ADAMIDIS, Thomas NATHENAS, Athanasios KARLIS [View]
[Download]

Abstract: In this paper two different conversion systems of wind energy into electricity are investigated. In the first system studied the wind turbine is connected to a three phase diode rectifier. At the output of the non-controlled rectifier a DC/DC boost converter is connected. Controlling the switching pattern for the DC/DC converter the maximum power point (MPPT) is achieved. In the second system the wind turbine is connected to a three-level rectifier consisting IGBTs switches. The three-level rectifier triggered with the space vector modulation method (SVPWM). The maximum power is achieved through and algorithm which modifies the switching pattern. On the grid side a three level inverter is connected. The controllers applied to both systems are fuzzy controllers. For the study of these two systems Matlab/ Simulink was used in steady state and transient response.

   Comparison of different control techniques for grid side VSC in terms of losses and current harmonics
By Magdalena SCHRÖDER, Sidney GIERSCHNER, Hans-Guenter ECKEL [View]
[Download]

Abstract: More and more wind power plants are built which use voltage source converters (VSC) to feed energy into grid. This paper compares two different control techniques and shows how virtual flux direct power control (VFDPC) reduces filtering requirements at the output of the converter and helps to save up to one quarter of converter losses. Furthermore the influence of a reduced, variable dc link voltage of the wind power plant itself and its converter control is discussed.

   Considerations for Active Condition Monitoring in Power Electronic Converters
By Tommi KARKKAINEN, Pertti SILVENTOINEN [View]
[Download]

Abstract: No generally accepted and widely adopted condition monitoring method currently exists for power elec-tronic converters. Several failure precursors have been proposed for power electronic components. Inthis paper the authors investigate the requirements for a condition monitoring system for different appli-cations and consider the applicability of previously proposed failure precursors.

   Current Sensor Fault Detection and Isolation combining Model-Based and Signal-Based Algorithms in PMSG Drives
By Yves MOLLET, Johan GYSELINCK, Fabien MEINGUET [View]
[Download]

Abstract: This paper presents a new on-line open-phase and current-sensor fault detection and isolation methodfor permanent-magnet synchronous generator (PMSG) drives with neutral point voltage control. Simplesignal processing implementations for sensor outage and open-phase faults detection are combined witha cumulative-sum (CUSUM) algorithm capable of detecting smaller sensor output errors (offset or gainvariation). The algorithm uses output signals from eight current sensors (two on each phase and two onthe neutral wire). Experimental tests have been done on a 2kW-PMSG at different speeds and brakingtorques where different sensor-fault combinations have been tested with and without open-phase fault.Finally a test has been done while the shaft speed and the torque were varying in order to test the abilityof the algorithm to work in transient conditions. Results show that the algorithm allows 3-out-of-6redundancy in case of sensor outage and 5-out-of-6 redundancy in case of sensor offset or gain changewith globally limited computational cost. Combinations of two outages and one offset or gain error canbe isolated. In case of open-phase fault the algorithm can continue to detect sensor faults if at least onesensor is working on each remaining phase and on the neutral. A short fault detection time is obtainedin case of sensor outage with a transitional detection by the CUSUM algorithm followed by the finaldetection by the signal processing algorithm.

   Design of Grid-connected Directly Driven Wave Power Generation System With Optimal Control of Output Power
By Kai SUN, Qing KANG, Xi XIAO, Zanxiang NIE, Lipei HUANG [View]
[Download]

Abstract: This paper presents a directly driven wave power generation system which is connected to power gridcomposed of permanent magnetic linear generator(PMLG)， generator side converter, grid sideconverter, controller and grid. Control strategies based on back to back converter structure wasproposed: vector decoupling control was used to generator side converter aiming at optimize powerextraction from wave energy; Grid voltage oriented control was used to grid side converter in order tomake the current sinusoidal and realize unit power factor control. Since the DC link voltage hasfluctuation using traditional method, a method with power feed forward was proposed to keep the DClink voltage stable and improve the dynamic response of the system. A simulation model was built forthe whole system in Matlab/Simulink and simulation results verified that the proposed control strategyis feasible and effective.

   Efficiency Comparison of 690V-Converter Topologies for Wind Power Plants with DFIG
By Thomas RUMP, David WEISS, Hans-Guenter ECKEL [View]
[Download]

Abstract: 2-level-converters with 1700V-IGBTs and 1100V dc-link voltage are common in wind powergeneration. However, this dc-link voltage is not sufficient to fulfill reactive power requirements of gridoperators in any circumstances. In case of high active and reactive power generation of the windpower plant and an overvoltage in the grid the dc-link voltage has to be increased.In this paper the power losses of a 2-level-converter with a fictitious 2kV-IGBT and a 3-levelconverterwith 1200V-IGBTs are calculated for 1250V dc-link voltage and compared to each other.The loss calculation is done over a wind speed range from 0 to 12m/s. Additionally the converterenergy losses in 20 years are determined assuming a IEC III wind speed distribution.It was found that the 2-level-converter with 2kV-IGBTs produces the highest power losses in anyoperation points. The losses with the 1200V-IGBT 3-level-converter and 1250V dc-link voltage areeven smaller than for the 2-level-converter with 1700V-IGBT and 1100V dc-link voltage. The valuesfor the 20 years energy losses are corresponding.Therefore it can be said that the 3-level-converter is a good alternative to the 2-level-converter with1700V-IGBT due to reduced power losses and the capability to fulfill grid code requirements.

   Fault Ride Through of DFIG-based Wind Turbine with Saturable Transformer Model
By Hilmi GURLEYEN, Erkan MESE, Yusuf YASA [View]
[Download]

Abstract: This paper presents performance of doubly-fed induction generator (DFIG) based wind turbine undergrid fault. All system is designed in Matlab/SIMULINK. DFIG and drive train model created inmathematical domain, whereas semiconductor switches, filters, transmission line and transformers arecreated with available models in Matlab/Simulink/SimPowerSystems toolbox. Saturable transformermodel is used and compared with linear transformer model under fault.

   Fundamental Frequency and Mission Profile Wearout of IGBT in DFIG Converters for Windpower
By David WEISS, Hans-Guenter ECKEL [View]
[Download]

Abstract: In this paper the influence of fundamental frequency and mission profile power cycles on estimated lifetime of the power semiconductors in the rotor side converter of a DFIG will be investigated. The aim of this paper is to get a feeling which impact the large cycles due to the variation of wind speed (missionprofile cycles) and the short cycles caused by the output frequency of the converter (fundamental frequency cycles) have on the estimated life time of the power semiconductors. The total number of cycles, including mission profile and fundamental frequency cycles, were counted using the Rainflow algorithm. To count the fundamental frequency only the maximum and minimum temperature within one period of the fundamental frequency were extracted. The investigation was done for a real wind speed over time profile over 6 months.

   Influence of IGBT Current Rating on the Thermal Cycling Lifetime of a Power Electronic Active Rectifier in a Direct Wave Energy Converter
By Thibaut KOVALTCHOUK, Judicael AUBRY, Bernard MULTON, Hamid BEN AHMED [View]
[Download]

Abstract: Direct Wave Energy Converters offer high reliability potential, which is a key factor in offshore environments, yet their electrical power produced is strongly pulsating. The t hermal cycling of their power electronic switches (considered here to be I nsulated Gate Bipolar Transistors, IGBT) may reduce the lifetime of the power electronic converter. This study proposes a generic design method for choosing both the IGBT current rating and the heatsink thermal resistance in order to satisfy a reliability constraint. A parametric electro-thermal model has thus been developed to determine the junction temperature time series. Moreover, a rainflow cycle counting method is introduced for the reliability analysis and lifetime prediction using two aging models, one for wire bonds, the other for the solder joint of the chip.

   Modeling and Simulation of Permanent Magnet Synchronous Generator Wind Power Generation System Using Boost Converter Circuit
By Sirichai TAMMARUCKWATTANA [View]
[Download]

Abstract: This paper proposes variable-speed wind generator system using the Boost chopper system. The boost chopper system has three speed control modes for the wind velocity. The control mode of low wind velocity regulates armature current of the generator with the boost chopper circuit to control the speed of wind turbine. The control mode of middle wind velocity regulates the DC link voltage with vector controlled inverter to control the speed of wind turbine. The control mode of high wind velocity regulates the pitch angle of the wind turbine with the pitch angle control system to control the speed of wind turbine. The hybrid of three control modes extends the variable-speed range. The boost chopper system simplifies the maintenance and improves the reliability and reduces the cost in compare with PWM converter system. extensive

   Reconfiguration of Control Strategies for High Power DFIG Wind Turbine System with Grid Fault Ride-Through Capability
By Ling PENG, Hongwei MA, Yongdong LI, Bruno FRANCOIS, Xu LIE [View]
[Download]

Abstract: This paper proposes a reconfiguration scheme of control strategies for a doubly fed induction generator (DFIG) based wind turbine system. With the proposed scheme, the wind turbine system can remain connected to the grid and produce a maximum reactive power to assist the grid voltage recovery.

   Thermal Profile Analysis of Doubly-Fed Induction Generator Based Wind Power Converter with Air and Liquid Cooling Methods
By Dao ZHOU, Frede BLAABJERG, Michael TONNES, Mogens LAU [View]
[Download]

Abstract: Today, wind power generation system keeps on moving from onshore to offshore and also upscaling in size. As the lifetime of the wind power converter is prolonged to 20-25 years, this paper will investigate and compare different cooling methods for power modules – the air cooling and the liquid cooling seen from a thermal profile assessment point of view. Firstly, an analytical approach from loss profile to thermal profile for the power semiconductor is proposed and verified in a 2 MW Doubly-Fed Induction Generator (DFIG) based wind turbine system. Then, the typical air cooling and liquid cooling in wind power converter are analyzed and compared in terms of the mean junction temperature and the junction temperature fluctuation. It is concluded that the liquid cooling approach has a similar junction temperature fluctuation but gives a lower mean junction temperature than the air cooling approach.

   V-theta Control of Inverters Used in SPM Wind Turbine Generators
By Mehanathan PATHMANATHAN, Wen SOONG, Nesimi ERTUGRUL [View]
[Download]

Abstract: This paper examines a modulation strategy called V-theta control, designed for six-switch controlled rectifiers in small-scale wind turbines. In this strategy, surface permanent magnet (SPM) generator torque is commanded by controlling the magnitude of the phase voltage and its phase shift with respect to the current. Simulated results obtained using simplified and PWM inclusive models were used to validate the analytical findings presented. Lastly, experiments comparing V-theta, phase advance and conventional switched-mode rectifier (SMR) modulated AC/DC converters across a range of generator speeds. V-theta; control was found to produce up to 22\% more power when compared to phase advance modulation, the control technique with the closest performance.

   Wind Energy Conversion System Equipped With Doubly-Fed Induction Generator Controlled by back-to-back Power Electronic Converter under Various Grid Faults
By Dimitrios GIAOURAKIS, Athanasios SAFACAS, Savvas TSOTOULIDIS [View]
[Download]

Abstract: The main objective of this paper is to investigate the behaviour of Doubly-Fed Induction Generator (DFIG) under various grid disturbances. In order to study the dynamic response of DFIG, to emerge the faults’ consequences, a model has been simulated in Matlab/Simulink. In addition, FFT analysis has been done to achieve fault diagnosis and identification. The disturbances that have been investigated are 1φ to ground, phase to phase and three phase short-circuit. Also, the model of DFIG has been simulated under asymmetrical voltage sag. In these cases DFIG has been operated under subsynchronous mode.

EPE 2013 - DS3g: Converters for Rotating and Linear Generators
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2013 ECCE Europe - Conference > EPE 2013 - Topic 14: Converters for rotating and linear generators > EPE 2013 - DS3g: Converters for Rotating and Linear Generators
	[return to parent folder]

	A Paradigm Change in Wind Power Station Control through Emulation of Conventional Power Plant Behaviour By Florian FEIN, Markus SCHMIDT, Holger GROKE, Bernd ORLIK	[View] [Download]
Abstract: With a new control concept presented in this paper, wind power stations with inverter-coupledsynchronous generators (SG-WPS) behave to a great extent like the turbine-generator sets ofconventional thermal power plants including the ability of the release of active- and reactive reservepower. This allows every single SG-WPS to improve its contribution to power grid stability. The newcontrol concept consists of three main subsystems: The control of the grid-side inverter, the control ofthe generator-side inverter and the control of the rotor speed with the pitch angle. This paper points toall named subsystems, but the main focus is on the control of the dc-link voltage of the frequencyinverter. In contrast to conventional control concepts of SG-WPS, where the dc-link voltage isregulated with the grid-side inverter, here it is controlled with the generator-side inverter. This is aparadigm change in wind power station control. Without the task of dc-link voltage control, the grid-sideinverter of the SG-WPS is operated with droop based virtual synchronous machine emulation. Itallows the SG-WPS to immediately react to grid disturbances by the release of active- and reactivereserve power. This is an important step in the conversion of a WPS from a “negative consumer” to avoltage source. Simulation results show the dynamic behaviour of the SG-WPS with the new controlconcept as a whole. A test bench and experimental results for the dc-link voltage control with thegenerator-side inverter will be presented.

	Advanced Modeling of a Doubly Fed Induction Generator with open Statorfor soft Grid Synchronization By Christian MEHLER, Guido TISBORN, Holger GROKE, Bernd ORLIK	[View] [Download]
Abstract: This paper presents a new, extended flux model of the doubly fed induction generator (DFIG). Thisextended flux model describes the operation at no-load with open stator connections, as well as theoperation when connected to the grid. With this model, it is possible to simulate the softsynchronization of the DFIG to the grid. Also the synchronization process itself is modified using thenew flux model. This paper presents simulations of the new flux model and the synchronizationprocedure. Measurements at a test bench complete the paper.

	Comparative investigation and improvement of wind farms based on wind energy conversion and grid connection methodsS121201F By Georgios ADAMIDIS, Thomas NATHENAS, Athanasios KARLIS	[View] [Download]
Abstract: In this paper two different conversion systems of wind energy into electricity are investigated. In the first system studied the wind turbine is connected to a three phase diode rectifier. At the output of the non-controlled rectifier a DC/DC boost converter is connected. Controlling the switching pattern for the DC/DC converter the maximum power point (MPPT) is achieved. In the second system the wind turbine is connected to a three-level rectifier consisting IGBTs switches. The three-level rectifier triggered with the space vector modulation method (SVPWM). The maximum power is achieved through and algorithm which modifies the switching pattern. On the grid side a three level inverter is connected. The controllers applied to both systems are fuzzy controllers. For the study of these two systems Matlab/ Simulink was used in steady state and transient response.

	Comparison of different control techniques for grid side VSC in terms of losses and current harmonics By Magdalena SCHRÖDER, Sidney GIERSCHNER, Hans-Guenter ECKEL	[View] [Download]
Abstract: More and more wind power plants are built which use voltage source converters (VSC) to feed energy into grid. This paper compares two different control techniques and shows how virtual flux direct power control (VFDPC) reduces filtering requirements at the output of the converter and helps to save up to one quarter of converter losses. Furthermore the influence of a reduced, variable dc link voltage of the wind power plant itself and its converter control is discussed.

	Considerations for Active Condition Monitoring in Power Electronic Converters By Tommi KARKKAINEN, Pertti SILVENTOINEN	[View] [Download]
Abstract: No generally accepted and widely adopted condition monitoring method currently exists for power elec-tronic converters. Several failure precursors have been proposed for power electronic components. Inthis paper the authors investigate the requirements for a condition monitoring system for different appli-cations and consider the applicability of previously proposed failure precursors.

	Current Sensor Fault Detection and Isolation combining Model-Based and Signal-Based Algorithms in PMSG Drives By Yves MOLLET, Johan GYSELINCK, Fabien MEINGUET	[View] [Download]
Abstract: This paper presents a new on-line open-phase and current-sensor fault detection and isolation methodfor permanent-magnet synchronous generator (PMSG) drives with neutral point voltage control. Simplesignal processing implementations for sensor outage and open-phase faults detection are combined witha cumulative-sum (CUSUM) algorithm capable of detecting smaller sensor output errors (offset or gainvariation). The algorithm uses output signals from eight current sensors (two on each phase and two onthe neutral wire). Experimental tests have been done on a 2kW-PMSG at different speeds and brakingtorques where different sensor-fault combinations have been tested with and without open-phase fault.Finally a test has been done while the shaft speed and the torque were varying in order to test the abilityof the algorithm to work in transient conditions. Results show that the algorithm allows 3-out-of-6redundancy in case of sensor outage and 5-out-of-6 redundancy in case of sensor offset or gain changewith globally limited computational cost. Combinations of two outages and one offset or gain error canbe isolated. In case of open-phase fault the algorithm can continue to detect sensor faults if at least onesensor is working on each remaining phase and on the neutral. A short fault detection time is obtainedin case of sensor outage with a transitional detection by the CUSUM algorithm followed by the finaldetection by the signal processing algorithm.

	Design of Grid-connected Directly Driven Wave Power Generation System With Optimal Control of Output Power By Kai SUN, Qing KANG, Xi XIAO, Zanxiang NIE, Lipei HUANG	[View] [Download]
Abstract: This paper presents a directly driven wave power generation system which is connected to power gridcomposed of permanent magnetic linear generator(PMLG)， generator side converter, grid sideconverter, controller and grid. Control strategies based on back to back converter structure wasproposed: vector decoupling control was used to generator side converter aiming at optimize powerextraction from wave energy; Grid voltage oriented control was used to grid side converter in order tomake the current sinusoidal and realize unit power factor control. Since the DC link voltage hasfluctuation using traditional method, a method with power feed forward was proposed to keep the DClink voltage stable and improve the dynamic response of the system. A simulation model was built forthe whole system in Matlab/Simulink and simulation results verified that the proposed control strategyis feasible and effective.

	Efficiency Comparison of 690V-Converter Topologies for Wind Power Plants with DFIG By Thomas RUMP, David WEISS, Hans-Guenter ECKEL	[View] [Download]
Abstract: 2-level-converters with 1700V-IGBTs and 1100V dc-link voltage are common in wind powergeneration. However, this dc-link voltage is not sufficient to fulfill reactive power requirements of gridoperators in any circumstances. In case of high active and reactive power generation of the windpower plant and an overvoltage in the grid the dc-link voltage has to be increased.In this paper the power losses of a 2-level-converter with a fictitious 2kV-IGBT and a 3-levelconverterwith 1200V-IGBTs are calculated for 1250V dc-link voltage and compared to each other.The loss calculation is done over a wind speed range from 0 to 12m/s. Additionally the converterenergy losses in 20 years are determined assuming a IEC III wind speed distribution.It was found that the 2-level-converter with 2kV-IGBTs produces the highest power losses in anyoperation points. The losses with the 1200V-IGBT 3-level-converter and 1250V dc-link voltage areeven smaller than for the 2-level-converter with 1700V-IGBT and 1100V dc-link voltage. The valuesfor the 20 years energy losses are corresponding.Therefore it can be said that the 3-level-converter is a good alternative to the 2-level-converter with1700V-IGBT due to reduced power losses and the capability to fulfill grid code requirements.

	Fault Ride Through of DFIG-based Wind Turbine with Saturable Transformer Model By Hilmi GURLEYEN, Erkan MESE, Yusuf YASA	[View] [Download]
Abstract: This paper presents performance of doubly-fed induction generator (DFIG) based wind turbine undergrid fault. All system is designed in Matlab/SIMULINK. DFIG and drive train model created inmathematical domain, whereas semiconductor switches, filters, transmission line and transformers arecreated with available models in Matlab/Simulink/SimPowerSystems toolbox. Saturable transformermodel is used and compared with linear transformer model under fault.

	Fundamental Frequency and Mission Profile Wearout of IGBT in DFIG Converters for Windpower By David WEISS, Hans-Guenter ECKEL	[View] [Download]
Abstract: In this paper the influence of fundamental frequency and mission profile power cycles on estimated lifetime of the power semiconductors in the rotor side converter of a DFIG will be investigated. The aim of this paper is to get a feeling which impact the large cycles due to the variation of wind speed (missionprofile cycles) and the short cycles caused by the output frequency of the converter (fundamental frequency cycles) have on the estimated life time of the power semiconductors. The total number of cycles, including mission profile and fundamental frequency cycles, were counted using the Rainflow algorithm. To count the fundamental frequency only the maximum and minimum temperature within one period of the fundamental frequency were extracted. The investigation was done for a real wind speed over time profile over 6 months.

	Influence of IGBT Current Rating on the Thermal Cycling Lifetime of a Power Electronic Active Rectifier in a Direct Wave Energy Converter By Thibaut KOVALTCHOUK, Judicael AUBRY, Bernard MULTON, Hamid BEN AHMED	[View] [Download]
Abstract: Direct Wave Energy Converters offer high reliability potential, which is a key factor in offshore environments, yet their electrical power produced is strongly pulsating. The t hermal cycling of their power electronic switches (considered here to be I nsulated Gate Bipolar Transistors, IGBT) may reduce the lifetime of the power electronic converter. This study proposes a generic design method for choosing both the IGBT current rating and the heatsink thermal resistance in order to satisfy a reliability constraint. A parametric electro-thermal model has thus been developed to determine the junction temperature time series. Moreover, a rainflow cycle counting method is introduced for the reliability analysis and lifetime prediction using two aging models, one for wire bonds, the other for the solder joint of the chip.

	Modeling and Simulation of Permanent Magnet Synchronous Generator Wind Power Generation System Using Boost Converter Circuit By Sirichai TAMMARUCKWATTANA	[View] [Download]
Abstract: This paper proposes variable-speed wind generator system using the Boost chopper system. The boost chopper system has three speed control modes for the wind velocity. The control mode of low wind velocity regulates armature current of the generator with the boost chopper circuit to control the speed of wind turbine. The control mode of middle wind velocity regulates the DC link voltage with vector controlled inverter to control the speed of wind turbine. The control mode of high wind velocity regulates the pitch angle of the wind turbine with the pitch angle control system to control the speed of wind turbine. The hybrid of three control modes extends the variable-speed range. The boost chopper system simplifies the maintenance and improves the reliability and reduces the cost in compare with PWM converter system. extensive

	Reconfiguration of Control Strategies for High Power DFIG Wind Turbine System with Grid Fault Ride-Through Capability By Ling PENG, Hongwei MA, Yongdong LI, Bruno FRANCOIS, Xu LIE	[View] [Download]
Abstract: This paper proposes a reconfiguration scheme of control strategies for a doubly fed induction generator (DFIG) based wind turbine system. With the proposed scheme, the wind turbine system can remain connected to the grid and produce a maximum reactive power to assist the grid voltage recovery.

	Thermal Profile Analysis of Doubly-Fed Induction Generator Based Wind Power Converter with Air and Liquid Cooling Methods By Dao ZHOU, Frede BLAABJERG, Michael TONNES, Mogens LAU	[View] [Download]
Abstract: Today, wind power generation system keeps on moving from onshore to offshore and also upscaling in size. As the lifetime of the wind power converter is prolonged to 20-25 years, this paper will investigate and compare different cooling methods for power modules – the air cooling and the liquid cooling seen from a thermal profile assessment point of view. Firstly, an analytical approach from loss profile to thermal profile for the power semiconductor is proposed and verified in a 2 MW Doubly-Fed Induction Generator (DFIG) based wind turbine system. Then, the typical air cooling and liquid cooling in wind power converter are analyzed and compared in terms of the mean junction temperature and the junction temperature fluctuation. It is concluded that the liquid cooling approach has a similar junction temperature fluctuation but gives a lower mean junction temperature than the air cooling approach.

	V-theta Control of Inverters Used in SPM Wind Turbine Generators By Mehanathan PATHMANATHAN, Wen SOONG, Nesimi ERTUGRUL	[View] [Download]
Abstract: This paper examines a modulation strategy called V-theta control, designed for six-switch controlled rectifiers in small-scale wind turbines. In this strategy, surface permanent magnet (SPM) generator torque is commanded by controlling the magnitude of the phase voltage and its phase shift with respect to the current. Simulated results obtained using simplified and PWM inclusive models were used to validate the analytical findings presented. Lastly, experiments comparing V-theta, phase advance and conventional switched-mode rectifier (SMR) modulated AC/DC converters across a range of generator speeds. V-theta; control was found to produce up to 22\% more power when compared to phase advance modulation, the control technique with the closest performance.

	Wind Energy Conversion System Equipped With Doubly-Fed Induction Generator Controlled by back-to-back Power Electronic Converter under Various Grid Faults By Dimitrios GIAOURAKIS, Athanasios SAFACAS, Savvas TSOTOULIDIS	[View] [Download]
Abstract: The main objective of this paper is to investigate the behaviour of Doubly-Fed Induction Generator (DFIG) under various grid disturbances. In order to study the dynamic response of DFIG, to emerge the faults’ consequences, a model has been simulated in Matlab/Simulink. In addition, FFT analysis has been done to achieve fault diagnosis and identification. The disturbances that have been investigated are 1φ to ground, phase to phase and three phase short-circuit. Also, the model of DFIG has been simulated under asymmetrical voltage sag. In these cases DFIG has been operated under subsynchronous mode.