EPE Association: EPE 1999 - Topic 09e: Adjustable Speed Generation Systems

EPE 1999 - Topic 09e: Adjustable Speed Generation Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1999 - Conference > EPE 1999 - Topic 09: POWER ELECTRONICS IN GENERATION, TRANSMISSION AND DISTRIBUTION > EPE 1999 - Topic 09e: Adjustable Speed Generation Systems

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   A PM Synchronous Machine Drive for a Miniature Hydro Power Station
By J. Luukko; I. Tunkkari; J. Pyrhönen [View]
[Download]

Abstract: A permanent magnet synchronous machine drive for a miniature hydro power station is presented. The machine inverter control principle is direct-torque-control-based without a shaft-mounted speed measurement. The line coverter is also based on DTC. Possible faults associated with using a permanent magnet synchronous generator are also analysed. A laboratory drive is tested and measurement results are presented. It is shown that this kind of a drive is a better alternative to a grid connected asynchronous generator in a low speed hydro power station application.

   Control of Self-Excited Induction Generators Driven by Wind Turbines
By J. Sallan; E. Muljadi; M. Sanz; C. P. Butterfield [View]
[Download]

Abstract: The use of squirrel-cage induction machines in variable-speed wind generation systems presents serveal advantages. The cage induction machine is simple, reliable, requires very little maintenance and has a low cost and weight per kilowatt. Besides, the variable speed operation allows an increase in the energy captured and reduces both the torque peaks in the drive train and the fluctuations in the power sent to the utility. Its main drawback is the need for an electronic interface to connect the generator to the utility. This interface can be greatly simplified by using a self-excited generator because in that case a simple diode bridge is required to perform the AC/DC conversion. The subsequent AC/DC conversion can be performed by means of different techniques. One that is readily available for large power conversion, has a low cost and is highly reliable is the use of a thyristor bridge. The delay angle of the bridge can be used to make the wind turbine track the optimum power curve. This paper analyzes the operation of such a system applied to a 1/3 hp self-excited generator. It presents the main results from the simulation and the test performed for the different excitation configurations.

   Load-adaptive Variable Speed Generating System - Behaviour Analyse of Dynamic
By L. M. Grzesiak; W. Koczara [View]
[Download]

Abstract: The HYGEN load-adaptive variable-speed generating system produces standard AC 50Hz, 230 Vrms voltage for common applications – and for very sensitive loads. The system comprises two energy sources. The primary energy source is an engine-driven alternator and the secondary source is a battery bank. The permanent magnet generator generates an output of variable voltage and variable frequency, which is converted by an AC/DC/AC power electronic converter system, resulting in a high quality output voltage, even under the most adverse load conditions. Energy flow between the engine, battery and load is controlled by means of the converters. The control feature of the DC/DC converter, which is connected to the output of the generator through a rectifier and LC filter, permits manipulation of th torque acting on the engine by controlling the current in the alternator. In addition, the voltage of th alternator is allowed to vary freely. Mathematical models of all subsystems are described, and ar finally integrated into a complex model of the whole system. Models of subsystems and also the overall model are implemented in Simulink. In order to simplify the calculations, all electrical AC units ar converted to the equivalent DC–link model using the DC/DC converter model with average quantities. The dynamic behaviour of the system under several step-loads at different operating points is analysed and discussed. Resistive step-loads are applied to the output of the inverter because they represent th most difficult load conditions, i.e. inrush current di/dt approaching infinity. Computer simulation results are presented.

   Numerical Model of Adjustable-Speed Power Unit Using Doubly Fed Machine with Cycloconverter in Rotor Circuit
By M. Chomat; L. Schreier; J. Bendl [View]
[Download]

Abstract: A numerical model of an adjustable-speed power unit utilising a doubly fed machine with a 12-pulse cycloconverter in the rotor circuit was developed. Both steady-state and transient operation of the system were numerically simulated and analysed. The results will be used in design and development of a real unit for a storage power plant.

   Rotor Flux Oriented Induction Machines as a DC Power Generator
By E. Levi; Y. W. Liao [View]
[Download]

Abstract: The paper deals with a variable-speed induction generator, aimed at supplying an autonomous dc power system with constant dc voltage. Reactive power requirements of the induction generator are met by voltage source converter, operated in current controlled mode. Control of the compensator is achieved using rotor flux oriented control principles. As operation in both base speed region and field-weakening region is anticipated, the generator is represented with a suitable saturated machine model. Estimation of instantaneous rotor flux space vector is performed using a recently introduced estimator that fully accounts for main flux saturation. Description of the system is provided and an extensive simulation study is performed. Self-excitation under no-load conditions, step application and variation of a dc load, and variable speed operation in both base speed and field weakening regions are examined by simulation. It is shown that the proposed control system is capable of maintaining constant dc voltage under all operating conditions. Excellent tracking of rotor flux reference is achieved, indicating that proper rotor flux orientation is maintained at all times.

   Variable Speed Grid Connected Induction Generator for Wind Energy Systems
By R. Pena; R. Cárdenas; D. Sbarbaro; R. Blasco-Giménez [View]
[Download]

Abstract: The control of an induction machine driven by a wind turbine suupplying energy to the grid is presented. Two back-to-back voltage source PWM inverters are used to interface the machine and the grid voltage. The machine currents are controlled using vector control techniques ensuring flux and torque control. Machine torque control is used in order to track an optimum rotational speed for maximum wind energy capture. The control of the DC-link voltage is accomplished by transformation of ac quantities to the rotating voltage reference frame, feedforward compensation and control of the E² norm in order to obtain a linear plant. This strategy can effectively be used for reducing the value of the DC link capacitor. The use of other techniques, such as duzzy logic controllers, is also discussed.

EPE 1999 - Topic 09e: Adjustable Speed Generation Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1999 - Conference > EPE 1999 - Topic 09: POWER ELECTRONICS IN GENERATION, TRANSMISSION AND DISTRIBUTION > EPE 1999 - Topic 09e: Adjustable Speed Generation Systems
	[return to parent folder]

	A PM Synchronous Machine Drive for a Miniature Hydro Power Station By J. Luukko; I. Tunkkari; J. Pyrhönen	[View] [Download]
Abstract: A permanent magnet synchronous machine drive for a miniature hydro power station is presented. The machine inverter control principle is direct-torque-control-based without a shaft-mounted speed measurement. The line coverter is also based on DTC. Possible faults associated with using a permanent magnet synchronous generator are also analysed. A laboratory drive is tested and measurement results are presented. It is shown that this kind of a drive is a better alternative to a grid connected asynchronous generator in a low speed hydro power station application.

	Control of Self-Excited Induction Generators Driven by Wind Turbines By J. Sallan; E. Muljadi; M. Sanz; C. P. Butterfield	[View] [Download]
Abstract: The use of squirrel-cage induction machines in variable-speed wind generation systems presents serveal advantages. The cage induction machine is simple, reliable, requires very little maintenance and has a low cost and weight per kilowatt. Besides, the variable speed operation allows an increase in the energy captured and reduces both the torque peaks in the drive train and the fluctuations in the power sent to the utility. Its main drawback is the need for an electronic interface to connect the generator to the utility. This interface can be greatly simplified by using a self-excited generator because in that case a simple diode bridge is required to perform the AC/DC conversion. The subsequent AC/DC conversion can be performed by means of different techniques. One that is readily available for large power conversion, has a low cost and is highly reliable is the use of a thyristor bridge. The delay angle of the bridge can be used to make the wind turbine track the optimum power curve. This paper analyzes the operation of such a system applied to a 1/3 hp self-excited generator. It presents the main results from the simulation and the test performed for the different excitation configurations.

	Load-adaptive Variable Speed Generating System - Behaviour Analyse of Dynamic By L. M. Grzesiak; W. Koczara	[View] [Download]
Abstract: The HYGEN load-adaptive variable-speed generating system produces standard AC 50Hz, 230 Vrms voltage for common applications – and for very sensitive loads. The system comprises two energy sources. The primary energy source is an engine-driven alternator and the secondary source is a battery bank. The permanent magnet generator generates an output of variable voltage and variable frequency, which is converted by an AC/DC/AC power electronic converter system, resulting in a high quality output voltage, even under the most adverse load conditions. Energy flow between the engine, battery and load is controlled by means of the converters. The control feature of the DC/DC converter, which is connected to the output of the generator through a rectifier and LC filter, permits manipulation of th torque acting on the engine by controlling the current in the alternator. In addition, the voltage of th alternator is allowed to vary freely. Mathematical models of all subsystems are described, and ar finally integrated into a complex model of the whole system. Models of subsystems and also the overall model are implemented in Simulink. In order to simplify the calculations, all electrical AC units ar converted to the equivalent DC–link model using the DC/DC converter model with average quantities. The dynamic behaviour of the system under several step-loads at different operating points is analysed and discussed. Resistive step-loads are applied to the output of the inverter because they represent th most difficult load conditions, i.e. inrush current di/dt approaching infinity. Computer simulation results are presented.

	Numerical Model of Adjustable-Speed Power Unit Using Doubly Fed Machine with Cycloconverter in Rotor Circuit By M. Chomat; L. Schreier; J. Bendl	[View] [Download]
Abstract: A numerical model of an adjustable-speed power unit utilising a doubly fed machine with a 12-pulse cycloconverter in the rotor circuit was developed. Both steady-state and transient operation of the system were numerically simulated and analysed. The results will be used in design and development of a real unit for a storage power plant.

	Rotor Flux Oriented Induction Machines as a DC Power Generator By E. Levi; Y. W. Liao	[View] [Download]
Abstract: The paper deals with a variable-speed induction generator, aimed at supplying an autonomous dc power system with constant dc voltage. Reactive power requirements of the induction generator are met by voltage source converter, operated in current controlled mode. Control of the compensator is achieved using rotor flux oriented control principles. As operation in both base speed region and field-weakening region is anticipated, the generator is represented with a suitable saturated machine model. Estimation of instantaneous rotor flux space vector is performed using a recently introduced estimator that fully accounts for main flux saturation. Description of the system is provided and an extensive simulation study is performed. Self-excitation under no-load conditions, step application and variation of a dc load, and variable speed operation in both base speed and field weakening regions are examined by simulation. It is shown that the proposed control system is capable of maintaining constant dc voltage under all operating conditions. Excellent tracking of rotor flux reference is achieved, indicating that proper rotor flux orientation is maintained at all times.

	Variable Speed Grid Connected Induction Generator for Wind Energy Systems By R. Pena; R. Cárdenas; D. Sbarbaro; R. Blasco-Giménez	[View] [Download]
Abstract: The control of an induction machine driven by a wind turbine suupplying energy to the grid is presented. Two back-to-back voltage source PWM inverters are used to interface the machine and the grid voltage. The machine currents are controlled using vector control techniques ensuring flux and torque control. Machine torque control is used in order to track an optimum rotational speed for maximum wind energy capture. The control of the DC-link voltage is accomplished by transformation of ac quantities to the rotating voltage reference frame, feedforward compensation and control of the E² norm in order to obtain a linear plant. This strategy can effectively be used for reducing the value of the DC link capacitor. The use of other techniques, such as duzzy logic controllers, is also discussed.