EPE Association: EPE-PEMC 2006 - Topic 12: RENEWABLE ENERGY SOURCES

EPE-PEMC 2006 - Topic 12: RENEWABLE ENERGY SOURCES
You are here: EPE Documents > 04 - EPE-PEMC Conference Proceedings > EPE-PEMC 2006 - Conference > EPE-PEMC 2006 - Topic 12: RENEWABLE ENERGY SOURCES

   [return to parent folder]

   A New Current Control Strategy of Maximizing the Generated Power from a Doubly Fed Induction Generator System
By Hui Li, Zhe Chen [View]
[Download]

Abstract: This paper focuses on the development of maximum wind power extraction strategies for variable speed constant frequency (VSCF) grid-connected wind power generation systems with a doubly fed induction generator (DFIG). A new control method is proposed by directly controlling the DFIG rotor current to follow an optimal condition for not only the extracted maximum power of the wind turbine below the base wind speed but also the copper loss minimization. Based on the wind turbine power characteristic and DFIG mathematical models, the relationships between the generator speed and d-q axis rotor current are derived respectively, for maximal mechanical power extraction and copper loss-minimization. Directly control rotor current scheme is simpler than the conventional vector control strategy. Simulation results have shown the proposed control strategy is correct and valid.

   Advanced Incremental Conductance MPPT Algorithm with a Variable Step Size
By Jae Ho Lee, Hyun Su Bae, Bo Hyung Cho [View]
[Download]

Abstract: This paper proposes an advanced Incremental Conductance MPPT algorithm with a variable step size for a solar array regulator (SAR) system. This approach adjusts automatically a step size to the solar array operating point, thus improving the MPPT (Maximum Peak Power Tracking) speed and accuracy compared with the conventional method with a fixed step size. For the analysis of stability of the proposed algorithm near the maximum power point, the small signal modeling is carried out. Also, it is verified by experiment using a 180W parallel connected prototype hardware.

   Control and Stability Analysis of a Doubly Fed Induction Generator
By Toufik Bouaouiche, Mohamed Machmoum [View]
[Download]

Abstract: Today the penetration level of wind power on the network is high. The power system stability defined as the ability of the system, for given initial operation condition, to regain a normal state of equilibrium after being subjected to a disturbance is the major problem. In this paper we study the control and we analyse the voltage recovery of a doubly fed induction generator after short circuit faults. First, we propose a method which allows controlling the output voltage and frequency for the synchronisation with the network. Once the generator is connected, we introduce appropriate method for control of both active and reactive power flow and output voltage at the same time. The ability of the system to achieve soft and fast synchronisation to the grid and voltage recovery after a short circuit faults is analysed and discussed.

   Control of Multilevel Converter Driving Variable Speed Wind Turbine in Case of Grid Disturbances
By Zoran Ivanovic, Marko Vekic, Stevan Grabic, Vladimir Katic [View]
[Download]

Abstract: This paper proposes modified dual vector current control (DVCC) for the wind turbine application. As in case of conventional DVCC, it fulfills requirements for average unity power factor with suppressed oscillations in active power flow. However, uncontrolled increase in converter output current under unbalanced grid voltage conditions is prevented through imposing limit in its magnitude. Multilevel back-to-back converter is used in order to achieve full control of the turbine, as well as better power quality and lower torque and grid current oscillation.

   Control of Offshore DFIG-based Windfarm Grid with Line-Commutated HVDC Connection
By Serhiy Bozhko, Ramon Blasco-Gimenez, Risheng Li, Jon C. Clare, Greg M. Asher [View]
[Download]

Abstract: The paper considers a control solution for integration of large offshore DFIG-based wind farms with a common collection bus controlled by a STATCOM into the main onshore grid using line-commutated HVDC connection. The main focus of the paper is a mathematically grounded study of the power system interactions that resulted in a plant model appropriate for a formal control design. A design procedure is described and the controlled system is validated using PSCAD/EMTDC simulations confirming high performance of the proposed control strategy in both normal operation conditions and faults.

   DC Connection of Wind Power Generation System with Capacitor Energy Storage
By Toshimitsu Morizane, Takuma Hayashi, Noriyuki Kimura, Katsunori Taniguchi [View]
[Download]

Abstract: This paper presents the performance of connecting two wind generation systems with the energy storage at the dc side. Energy storage is desirable to be installed to keep constant output from the wind power generation system. The DC connection of two wind power generation system helps to exchange power between the two systems and can suppress the disturbance of the output power to the utility systems more longer than the stand alone system. This effect is easily achieved without any additional control. The controller measures only the common dc side capacitor voltage of the local system. MATLAB/simulink simulation verifies the better performance in a certain situation.

   Design of a Low-cost Proton Exchange Membrane Fuel Cell Stack
By Michael James Case, Johan Petrus du Toit, Hendrik Christoffelvan Zyl Pienaar [View]
[Download]

Abstract: This paper presents the design of a small proton exchange membrane fuel cell stack to be used in uninterruptible power supply systems for remote telecommunication sites. A proof of concept design is presented using a two-cell stack made from low-cost and readily available materials. Flow plates used in the stack were manufactured from copper-clad printed circuit board (PCB) using standard PCB manufacturing techniques and machines. This resulted in a significant cost saving and reduction in production time.

   Electrical Supply for the Small Islands on the Basis of Estonian Example
By Margus Leoste, Juhan Karin [View]
[Download]

Abstract: Electrical supply for the separate small islands can be difficult. It is long way to the mainland. Need of power is small and cable lines are expensive. Electricity through the diesel generators is expensive too. One possible solution is using a combination of wind and solar powers, as reserve diesel generator too. Several islands in Estonia are supplied on such manner. Possible solution for the others is showed too.

   Energy Storage and management in Wind turbine Generator Systems
By Chad Abbey, Geza Joos [View]
[Download]

Abstract: This paper considers the role that energy storage may play in the evolution of wind generator technologies, and how it is managed in order to mitigate impacts related to power system operations. The management of the energy storage device is discussed along with other potential options for limiting the output power fluctuations. The concepts are demonstrated using one of the most prominent wind turbine generator technologies, together with a two level energy storage system.

   Experimental Evaluation of the Direct Methanol Fuel Cell Lifespan Problems
By Michael James Case, Hardus Joubert, Hendrik Christoffelvan Zyl Pienaar [View]
[Download]

Abstract: The direct methanol fuel cell stack appears to have great advantages since the fuel is in a liquid form. However this liquid fuel causes the corrosion in the stack and therefore has a performance drop as a result. This paper addresses some of the causes of the associated problems. It is reported that the corrosion can be limited by eliminating all metal components in the anodic liquid flow circuit; this solution is not however complete and the performance of the DMFC remains limited.

   Identification of Wind Turbine Model for Controller Design
By Mate Jelavic, Nedjeljko Peric, Ivan Petrovic [View]
[Download]

Abstract: Wind power increases rapidly with increase of wind speed. In order to keep wind turbine running even at strong winds wind power capture has to be constrained. Efficient way for constraining wind power capture is the use of pitchable blades. For pitch controller design a suitable wind turbine model is needed. Finding mathematical model that would be a good representation of wind turbine system and at the same time suitable for controller design is very difficult task since wind turbine system is strongly nonlinear. Description of wind turbine system using many linear models identified at particular operating points is explored in this paper. Effects occurring when switching between models are examined and their repercussions on controller design are discussed. Use of fuzzy logic is proposed as possible solution for avoiding negative effects caused by switching between models.

   Improved MPPT Algorithms for Rapidly Changing Environmental Conditions
By Dezso Sera, Tamas Kerekes, Remus Teodorescu, Frede Blaabjerg [View]
[Download]

Abstract: The first part of this paper intends to give an overview of the Maximum Power Point Tracking methods for Photovoltaic (PV) inverters presently reported in the literature. The most well-known and popular methods, like the Perturb and Observe (P&O), the Incremental Conductance (INC) and the Constant Voltage (CV), are presented. These methods, especially the P&O, have been treated by many works, which aim to overcome their shortcomings, either by optimizing the methods, or by combining them. In the second part of the paper an improvement for the P&O and INC method is proposed, which prevents these algorithms to get confused during rapidly changing irradiation conditions, and it considerably increases the efficiency of the MPPT.

   Innovation on Traditional Waterwheels for Renewable Energy
By Franz Aschenbrenner [View]
[Download]

Abstract: Renewable energy is one of the most important topics for all engineers. The production of CO2 is a very finical problem for the climate of our earth. Everybody is committed to improve all opportunities to avoid the burning of exhausted raw materials. Beneath the using of renewable primacy products the consumption of alternating energy is a way to solve a little part of this problem.

   Modeling and Test of a PM Synchronous Generator based Small Stand Alone Wind Energy Converter
By Eric Jean Roy Sambatra, Jacques Raharijaona, Georges Barakat, Brayima Dakyo [View]
[Download]

Abstract: This paper deals with the study of the behavior of stand alone wind energy converters (WEC) based on permanent magnet synchronous generator (PMSG). First, the WEC chain is described and the model of each component of the conversion set is studied. At this stage, a special attention is given to incorporate the saturation effect in the PMSG model. Then, the obtained model is used to analyze the dynamic behavior of this WEC face to typical wind site profile and a variable electrical load. The obtained results help the authors to analyze the WEC performances as well as the impact of the generator saturation on the power conversion.

   Overview of Anti-Islanding Algorithms for PV Systems. Part I: Passive Methods
By Francesco De Mango, Marco Liserre, Antonio Dell Aquila, Alberto Pigazo [View]
[Download]

Abstract: This paper offers an overview of the passive methods used for islanding detection. A monitoring PLL has been adopted for the estimation of the voltage amplitude and frequency. Passive inverter resident methods discussed are the over/under voltage (OUV), over/under frequency (OUF), the voltage harmonic monitoring (with a study on the effects of the grid impedance value and of the inverter dc voltage ripple) and the phase monitoring (different from the classical phase jump method). A harmonic synchronization PLL is used to monitor the 3rd, 5th and 7th harmonics. All the proposed algorithms are validated by simulations and experimental results obtained in accordance with the IEEE Std. 929-2000 procedure.

   Overview of Anti-Islanding Algorithms for PV Systems. Part: II Active Methods
By Francesco De Mango, Marco Liserre, Antonio Dell Aquila [View]
[Download]

Abstract: This paper offers an overview of the active methods used for islanding detection. The inverter control algorithm is based on the use of harmonic compensators in order to create ideal working conditions (i.e. the PV-system produces a sinusoidal current and reject grid harmonics). This condition is the indispensable starting point to implement active islanding detection methods. In fact these methods are based on the perturbation of the ideal conditions (e.g. the injection of active/reactive power, the injection of current harmonics, or the insertion of an external capacitor). All the reported algorithms are carefully analysed in their advantage and drawbacks and the considerations are validated by tests results obtained in accordance with the IEEE Std. 929-2000 procedure.

   Permanent Power Generating Wind Turbine with Doubly Fed Asynchronous Generator and Storage Unit, Modelling and Simulation
By Armand Boyette, Shahrokh Saadate [View]
[Download]

Abstract: This paper deals with the design, analysis and simulation of wind turbine associated with a storage unit to generate a constant active power through the grid for all wind conditions. Variable speed wind turbine with a doubly fed induction generator which allows a large speed variation and so a large range of wind is employed. Associated with an inverter controlled with power reference, it is possible to adjust the injected power in the grid. The long duration storage unit connected to the DC bus allows producing a constant active power for all wind conditions. During strong wind the generator provides energy to the network and refills the storage unit and during insufficient wind the storage unit will compensate the lack of energy. The study deals with mainly the modelling of the mechanic and aerodynamic part of the wind turbine and the control of the rectifier - inverter in order to control the active and reactive powers for all wind and turbine speed conditions.

   Research for Electric Brake using NTC Thermistors on Micro Wind Turbine
By Akira Sugawara, Kenichi Yamamoto, Takeshi Yoshimi, Shingo Sato, Akira Tsurumaki, Tsuguru Ito [View]
[Download]

Abstract: As a brake system for small wind turbine, mechanical brake and electric brake by the short circuit of 3-phase permanent magnet generator are used. However, an electric braking method may damage the rotor and/or blades by rapid stop of the generator revolution. Moreover, generator winding may also be damaged by large shortcircuit current. In this paper, the electric braking method using NTC thermistors (negative temperature coefficient resistors) is proposed as a braking system for a cheaper and safe micro wind turbine.

   Short Term Energy Storage based on Reluctance Machine Control for Wind Diesel System
By Mostafa El Mokadem, Cristian Nichita, Pascal Reghem, Brayima Dakyo [View]
[Download]

Abstract: The paper presents a simulation for energy short term storage unit integrated into a stand alone hybrid wind diesel system. The energy short term storage unit is a flywheel device which is driven by a 6/4 switched reluctance machine (SRM) operating in motor and generator modes. The control strategy is developed to smooth the wind power turbulence fluctuations in order to decrease the fuel consumption by the diesel generator and to allow it a suitable operation because of its slow dynamic. The system model is implemented on Matlab-Simulink environment.

   Simulation of a Doubly Fed Induction Generator Used in an Autonomous Variable Speed Hydro Turbine with Maximum Power Point Tracking Control
By Denis Ramuz, Mamadou Camara, Henri Clergeot, Jean Marie Kaufmann [View]
[Download]

Abstract: In this paper, the authors propose an approach with problems of electricity production in isolated sites for tropical countries. Indeed, the geographical context implies often that many populations live in rural areas and are in the majority located at the edge of the rivers. The originality of this work is hybridization with a photovoltaic system via a common Direct Current bus and a maximum power point tracking control (MPPT).

   Small-Power Wind Turbine’s Characterization. Application in a Production’s Forecast
By Adan Simon Muela, Vincent Boitier, Corinne Alonso [View]
[Download]

Abstract: This paper develops a technique to estimate the production of small-power wind turbines by means of Weibull distribution. Moreover, a characterization of the employed turbine has been achieved obtaining experimental results of the production. Finally, a comparison of practical measurements and those estimated has been made presented.

   Wind Power Generation System with Induction Machine and Diode Rectifier
By Noriyuki Kimura, Mitsuhiro Hirao, Toshimitsu Morizane, Katsunori Taniguchi [View]
[Download]

Abstract: This paper investigates advantages of new combination of the induction generator for wind power and the power electronic equipments. Induction generator is popularly used for the wind power generation. The disadvantage of it is impossible to generate power at the lower rotor speed than the synchronous speed. To compensate this disadvantage, expensive synchronous generator with the permanent magnets sometimes used. If HVDC transmission is used to connect the offshore wind farm to the mainland, using AC/DC converter system is no more disadvantageous. However, to omit the expensive permanent magnet is desirable. In proposed scheme, the diode rectifier is used to convert the real power from the induction generator to the intermediate dc voltage, while the reactive power necessary to excite the induction generator only is supplied from the voltage source converter (VSC). This means that the rating of the expensive VSC is minimized and total cost of the wind power generation system is decreased compared to the system with synchronous generator.

   Wind Power Rotor Blade Stress Minimisation by Active Damping through Generator Torque Control
By Thomas Karall, Helmut Weiss, Rudolf Woerndle [View]
[Download]

Abstract: Renewable energy generation strongly relies on wind power aside from water power plants. Technical and economical growth rules (“The larger, the better”) yield systems of increasing power now far in the Megawatt range. Wind power rotor blades have to withstand high mechanical stress by standard and disturbed operation through centrifugal and power transmission forces. Especially, heavy wind gusts create critical situations for the mechanical survival of the rotor blades. A converter between machine and grid enables a high rate of control opportunities. A design is developed for active minimisation of stress peaks and damping of oscillations by specific control interception in generator torque control.

EPE-PEMC 2006 - Topic 12: RENEWABLE ENERGY SOURCES
You are here: EPE Documents > 04 - EPE-PEMC Conference Proceedings > EPE-PEMC 2006 - Conference > EPE-PEMC 2006 - Topic 12: RENEWABLE ENERGY SOURCES
	[return to parent folder]

	A New Current Control Strategy of Maximizing the Generated Power from a Doubly Fed Induction Generator System By Hui Li, Zhe Chen	[View] [Download]
Abstract: This paper focuses on the development of maximum wind power extraction strategies for variable speed constant frequency (VSCF) grid-connected wind power generation systems with a doubly fed induction generator (DFIG). A new control method is proposed by directly controlling the DFIG rotor current to follow an optimal condition for not only the extracted maximum power of the wind turbine below the base wind speed but also the copper loss minimization. Based on the wind turbine power characteristic and DFIG mathematical models, the relationships between the generator speed and d-q axis rotor current are derived respectively, for maximal mechanical power extraction and copper loss-minimization. Directly control rotor current scheme is simpler than the conventional vector control strategy. Simulation results have shown the proposed control strategy is correct and valid.

	Advanced Incremental Conductance MPPT Algorithm with a Variable Step Size By Jae Ho Lee, Hyun Su Bae, Bo Hyung Cho	[View] [Download]
Abstract: This paper proposes an advanced Incremental Conductance MPPT algorithm with a variable step size for a solar array regulator (SAR) system. This approach adjusts automatically a step size to the solar array operating point, thus improving the MPPT (Maximum Peak Power Tracking) speed and accuracy compared with the conventional method with a fixed step size. For the analysis of stability of the proposed algorithm near the maximum power point, the small signal modeling is carried out. Also, it is verified by experiment using a 180W parallel connected prototype hardware.

	Control and Stability Analysis of a Doubly Fed Induction Generator By Toufik Bouaouiche, Mohamed Machmoum	[View] [Download]
Abstract: Today the penetration level of wind power on the network is high. The power system stability defined as the ability of the system, for given initial operation condition, to regain a normal state of equilibrium after being subjected to a disturbance is the major problem. In this paper we study the control and we analyse the voltage recovery of a doubly fed induction generator after short circuit faults. First, we propose a method which allows controlling the output voltage and frequency for the synchronisation with the network. Once the generator is connected, we introduce appropriate method for control of both active and reactive power flow and output voltage at the same time. The ability of the system to achieve soft and fast synchronisation to the grid and voltage recovery after a short circuit faults is analysed and discussed.

	Control of Multilevel Converter Driving Variable Speed Wind Turbine in Case of Grid Disturbances By Zoran Ivanovic, Marko Vekic, Stevan Grabic, Vladimir Katic	[View] [Download]
Abstract: This paper proposes modified dual vector current control (DVCC) for the wind turbine application. As in case of conventional DVCC, it fulfills requirements for average unity power factor with suppressed oscillations in active power flow. However, uncontrolled increase in converter output current under unbalanced grid voltage conditions is prevented through imposing limit in its magnitude. Multilevel back-to-back converter is used in order to achieve full control of the turbine, as well as better power quality and lower torque and grid current oscillation.

	Control of Offshore DFIG-based Windfarm Grid with Line-Commutated HVDC Connection By Serhiy Bozhko, Ramon Blasco-Gimenez, Risheng Li, Jon C. Clare, Greg M. Asher	[View] [Download]
Abstract: The paper considers a control solution for integration of large offshore DFIG-based wind farms with a common collection bus controlled by a STATCOM into the main onshore grid using line-commutated HVDC connection. The main focus of the paper is a mathematically grounded study of the power system interactions that resulted in a plant model appropriate for a formal control design. A design procedure is described and the controlled system is validated using PSCAD/EMTDC simulations confirming high performance of the proposed control strategy in both normal operation conditions and faults.

	DC Connection of Wind Power Generation System with Capacitor Energy Storage By Toshimitsu Morizane, Takuma Hayashi, Noriyuki Kimura, Katsunori Taniguchi	[View] [Download]
Abstract: This paper presents the performance of connecting two wind generation systems with the energy storage at the dc side. Energy storage is desirable to be installed to keep constant output from the wind power generation system. The DC connection of two wind power generation system helps to exchange power between the two systems and can suppress the disturbance of the output power to the utility systems more longer than the stand alone system. This effect is easily achieved without any additional control. The controller measures only the common dc side capacitor voltage of the local system. MATLAB/simulink simulation verifies the better performance in a certain situation.

	Design of a Low-cost Proton Exchange Membrane Fuel Cell Stack By Michael James Case, Johan Petrus du Toit, Hendrik Christoffelvan Zyl Pienaar	[View] [Download]
Abstract: This paper presents the design of a small proton exchange membrane fuel cell stack to be used in uninterruptible power supply systems for remote telecommunication sites. A proof of concept design is presented using a two-cell stack made from low-cost and readily available materials. Flow plates used in the stack were manufactured from copper-clad printed circuit board (PCB) using standard PCB manufacturing techniques and machines. This resulted in a significant cost saving and reduction in production time.

	Electrical Supply for the Small Islands on the Basis of Estonian Example By Margus Leoste, Juhan Karin	[View] [Download]
Abstract: Electrical supply for the separate small islands can be difficult. It is long way to the mainland. Need of power is small and cable lines are expensive. Electricity through the diesel generators is expensive too. One possible solution is using a combination of wind and solar powers, as reserve diesel generator too. Several islands in Estonia are supplied on such manner. Possible solution for the others is showed too.

	Energy Storage and management in Wind turbine Generator Systems By Chad Abbey, Geza Joos	[View] [Download]
Abstract: This paper considers the role that energy storage may play in the evolution of wind generator technologies, and how it is managed in order to mitigate impacts related to power system operations. The management of the energy storage device is discussed along with other potential options for limiting the output power fluctuations. The concepts are demonstrated using one of the most prominent wind turbine generator technologies, together with a two level energy storage system.

	Experimental Evaluation of the Direct Methanol Fuel Cell Lifespan Problems By Michael James Case, Hardus Joubert, Hendrik Christoffelvan Zyl Pienaar	[View] [Download]
Abstract: The direct methanol fuel cell stack appears to have great advantages since the fuel is in a liquid form. However this liquid fuel causes the corrosion in the stack and therefore has a performance drop as a result. This paper addresses some of the causes of the associated problems. It is reported that the corrosion can be limited by eliminating all metal components in the anodic liquid flow circuit; this solution is not however complete and the performance of the DMFC remains limited.

	Identification of Wind Turbine Model for Controller Design By Mate Jelavic, Nedjeljko Peric, Ivan Petrovic	[View] [Download]
Abstract: Wind power increases rapidly with increase of wind speed. In order to keep wind turbine running even at strong winds wind power capture has to be constrained. Efficient way for constraining wind power capture is the use of pitchable blades. For pitch controller design a suitable wind turbine model is needed. Finding mathematical model that would be a good representation of wind turbine system and at the same time suitable for controller design is very difficult task since wind turbine system is strongly nonlinear. Description of wind turbine system using many linear models identified at particular operating points is explored in this paper. Effects occurring when switching between models are examined and their repercussions on controller design are discussed. Use of fuzzy logic is proposed as possible solution for avoiding negative effects caused by switching between models.

	Improved MPPT Algorithms for Rapidly Changing Environmental Conditions By Dezso Sera, Tamas Kerekes, Remus Teodorescu, Frede Blaabjerg	[View] [Download]
Abstract: The first part of this paper intends to give an overview of the Maximum Power Point Tracking methods for Photovoltaic (PV) inverters presently reported in the literature. The most well-known and popular methods, like the Perturb and Observe (P&O), the Incremental Conductance (INC) and the Constant Voltage (CV), are presented. These methods, especially the P&O, have been treated by many works, which aim to overcome their shortcomings, either by optimizing the methods, or by combining them. In the second part of the paper an improvement for the P&O and INC method is proposed, which prevents these algorithms to get confused during rapidly changing irradiation conditions, and it considerably increases the efficiency of the MPPT.

	Innovation on Traditional Waterwheels for Renewable Energy By Franz Aschenbrenner	[View] [Download]
Abstract: Renewable energy is one of the most important topics for all engineers. The production of CO2 is a very finical problem for the climate of our earth. Everybody is committed to improve all opportunities to avoid the burning of exhausted raw materials. Beneath the using of renewable primacy products the consumption of alternating energy is a way to solve a little part of this problem.

	Modeling and Test of a PM Synchronous Generator based Small Stand Alone Wind Energy Converter By Eric Jean Roy Sambatra, Jacques Raharijaona, Georges Barakat, Brayima Dakyo	[View] [Download]
Abstract: This paper deals with the study of the behavior of stand alone wind energy converters (WEC) based on permanent magnet synchronous generator (PMSG). First, the WEC chain is described and the model of each component of the conversion set is studied. At this stage, a special attention is given to incorporate the saturation effect in the PMSG model. Then, the obtained model is used to analyze the dynamic behavior of this WEC face to typical wind site profile and a variable electrical load. The obtained results help the authors to analyze the WEC performances as well as the impact of the generator saturation on the power conversion.

	Overview of Anti-Islanding Algorithms for PV Systems. Part I: Passive Methods By Francesco De Mango, Marco Liserre, Antonio Dell Aquila, Alberto Pigazo	[View] [Download]
Abstract: This paper offers an overview of the passive methods used for islanding detection. A monitoring PLL has been adopted for the estimation of the voltage amplitude and frequency. Passive inverter resident methods discussed are the over/under voltage (OUV), over/under frequency (OUF), the voltage harmonic monitoring (with a study on the effects of the grid impedance value and of the inverter dc voltage ripple) and the phase monitoring (different from the classical phase jump method). A harmonic synchronization PLL is used to monitor the 3rd, 5th and 7th harmonics. All the proposed algorithms are validated by simulations and experimental results obtained in accordance with the IEEE Std. 929-2000 procedure.

	Overview of Anti-Islanding Algorithms for PV Systems. Part: II Active Methods By Francesco De Mango, Marco Liserre, Antonio Dell Aquila	[View] [Download]
Abstract: This paper offers an overview of the active methods used for islanding detection. The inverter control algorithm is based on the use of harmonic compensators in order to create ideal working conditions (i.e. the PV-system produces a sinusoidal current and reject grid harmonics). This condition is the indispensable starting point to implement active islanding detection methods. In fact these methods are based on the perturbation of the ideal conditions (e.g. the injection of active/reactive power, the injection of current harmonics, or the insertion of an external capacitor). All the reported algorithms are carefully analysed in their advantage and drawbacks and the considerations are validated by tests results obtained in accordance with the IEEE Std. 929-2000 procedure.

	Permanent Power Generating Wind Turbine with Doubly Fed Asynchronous Generator and Storage Unit, Modelling and Simulation By Armand Boyette, Shahrokh Saadate	[View] [Download]
Abstract: This paper deals with the design, analysis and simulation of wind turbine associated with a storage unit to generate a constant active power through the grid for all wind conditions. Variable speed wind turbine with a doubly fed induction generator which allows a large speed variation and so a large range of wind is employed. Associated with an inverter controlled with power reference, it is possible to adjust the injected power in the grid. The long duration storage unit connected to the DC bus allows producing a constant active power for all wind conditions. During strong wind the generator provides energy to the network and refills the storage unit and during insufficient wind the storage unit will compensate the lack of energy. The study deals with mainly the modelling of the mechanic and aerodynamic part of the wind turbine and the control of the rectifier - inverter in order to control the active and reactive powers for all wind and turbine speed conditions.

	Research for Electric Brake using NTC Thermistors on Micro Wind Turbine By Akira Sugawara, Kenichi Yamamoto, Takeshi Yoshimi, Shingo Sato, Akira Tsurumaki, Tsuguru Ito	[View] [Download]
Abstract: As a brake system for small wind turbine, mechanical brake and electric brake by the short circuit of 3-phase permanent magnet generator are used. However, an electric braking method may damage the rotor and/or blades by rapid stop of the generator revolution. Moreover, generator winding may also be damaged by large shortcircuit current. In this paper, the electric braking method using NTC thermistors (negative temperature coefficient resistors) is proposed as a braking system for a cheaper and safe micro wind turbine.

	Short Term Energy Storage based on Reluctance Machine Control for Wind Diesel System By Mostafa El Mokadem, Cristian Nichita, Pascal Reghem, Brayima Dakyo	[View] [Download]
Abstract: The paper presents a simulation for energy short term storage unit integrated into a stand alone hybrid wind diesel system. The energy short term storage unit is a flywheel device which is driven by a 6/4 switched reluctance machine (SRM) operating in motor and generator modes. The control strategy is developed to smooth the wind power turbulence fluctuations in order to decrease the fuel consumption by the diesel generator and to allow it a suitable operation because of its slow dynamic. The system model is implemented on Matlab-Simulink environment.

	Simulation of a Doubly Fed Induction Generator Used in an Autonomous Variable Speed Hydro Turbine with Maximum Power Point Tracking Control By Denis Ramuz, Mamadou Camara, Henri Clergeot, Jean Marie Kaufmann	[View] [Download]
Abstract: In this paper, the authors propose an approach with problems of electricity production in isolated sites for tropical countries. Indeed, the geographical context implies often that many populations live in rural areas and are in the majority located at the edge of the rivers. The originality of this work is hybridization with a photovoltaic system via a common Direct Current bus and a maximum power point tracking control (MPPT).

	Small-Power Wind Turbine’s Characterization. Application in a Production’s Forecast By Adan Simon Muela, Vincent Boitier, Corinne Alonso	[View] [Download]
Abstract: This paper develops a technique to estimate the production of small-power wind turbines by means of Weibull distribution. Moreover, a characterization of the employed turbine has been achieved obtaining experimental results of the production. Finally, a comparison of practical measurements and those estimated has been made presented.

	Wind Power Generation System with Induction Machine and Diode Rectifier By Noriyuki Kimura, Mitsuhiro Hirao, Toshimitsu Morizane, Katsunori Taniguchi	[View] [Download]
Abstract: This paper investigates advantages of new combination of the induction generator for wind power and the power electronic equipments. Induction generator is popularly used for the wind power generation. The disadvantage of it is impossible to generate power at the lower rotor speed than the synchronous speed. To compensate this disadvantage, expensive synchronous generator with the permanent magnets sometimes used. If HVDC transmission is used to connect the offshore wind farm to the mainland, using AC/DC converter system is no more disadvantageous. However, to omit the expensive permanent magnet is desirable. In proposed scheme, the diode rectifier is used to convert the real power from the induction generator to the intermediate dc voltage, while the reactive power necessary to excite the induction generator only is supplied from the voltage source converter (VSC). This means that the rating of the expensive VSC is minimized and total cost of the wind power generation system is decreased compared to the system with synchronous generator.

	Wind Power Rotor Blade Stress Minimisation by Active Damping through Generator Torque Control By Thomas Karall, Helmut Weiss, Rudolf Woerndle	[View] [Download]
Abstract: Renewable energy generation strongly relies on wind power aside from water power plants. Technical and economical growth rules (“The larger, the better”) yield systems of increasing power now far in the Megawatt range. Wind power rotor blades have to withstand high mechanical stress by standard and disturbed operation through centrifugal and power transmission forces. Especially, heavy wind gusts create critical situations for the mechanical survival of the rotor blades. A converter between machine and grid enables a high rate of control opportunities. A design is developed for active minimisation of stress peaks and damping of oscillations by specific control interception in generator torque control.