EPE Association: EPE 1999 - Topic 09a: Renewable Energy Systems

EPE 1999 - Topic 09a: Renewable Energy 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 09a: Renewable Energy Systems

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   A Modular DC-DC Converter and Maximum Power Tracking Controller for medium to large scale Photovoltaic Generating Plant
By J.A. Gow; J. A. M. Bleijs [View]
[Download]

Abstract: A suitable configuration for medium to large scale photovoltaic plant consists of a number of d.c.-d.c. converter modules feeding a common bus with a single high power inverter providing the utility interface. This paper proposes an efficient d.c.-d.c. converter system employing a new fast maximum power point tracker with an appropriately optimized converter topology.

   Analysis and Design of Inverters for Low Voltage Generators
By J. Myrzik; A. Waldschmidt [View]
[Download]

Abstract: During the past few years the development of small inverters for photovoltaic technology has been supported by creating small, expandable energy supply systems. In order to reduce the high costs for solar technology nowadays, mainly the costs of the power conditioning have to be reduced. Therefore, the derivation of several transformerless inverter topologies will be presented here, which allow to connect a low generator voltage to the utility grid. Their conduction mode, DC- and AC-signal behaviour and modelling will be discussed. The theoretical results will be verified in a test circuit for stand alone systems.

   Current Source Inverter for a 400 kW Ocean Waves Induction Generator
By C. Joao Ramos; P. Moreira da Silva; A. Carvalho [View]
[Download]

Abstract: Electrical energy generated from the ocean waves is a renewable energy being developed. One form of retrieving this energy is using the Oscillating Water Column (OWC) principle. In order to optimise this energetic resource, the electric generator must work at variable speed depending on the input power. For the energy to be delivered to mains, the voltage magnitude and frequency must be constant. This paper describes a system that uses a generator based on a wound induction machine with slip energy recovery, which allows operation with variable speed and direct connection to the mains. The Slip Energy Recovery System (SERS) is based on a wound induction machine being controlled through the amount of rotor energy delivered to the mains by means of a static converter. The AC variable rotor voltage is converted to DC voltage with a rectifier groupment and then converted again to AC in order to be injected into mains. The use of an IGBT Current Source Inverter (CSI) as DC-AC converter minimises current harmonics and allows smooth interaction between the random and variable input power and the mains. The main advantage of this system is the ability to generate 400 kW using a 200 kW machine and a 200 kW CSI. The prototype appears as an important development due to work with a large renewable energy source at a significant power level. The good performance carried out by the equipment based on an induction generator is reached through a well-controlled IGBT based current inverter that is presented within this paper.

   Flywheel Energy Storage System Using a Vector Controlled Induction Motor
By R. Càrdenas; R. Peña; R. Blasco [View]
[Download]

Abstract: Even when variable speed wind turbines are used, electrical generation using wind energy conversion system generates electrical power which is not suitable for some application because of the ripple in the output of the generator. Also in wind diesel system, the wind velocity variations produce an unacceptable number of start/stop cycles of the diesel engine if an erergy buffer is not considered. In this paper the applications of the flywheel storage systems using vector controlled induction machines for wind energy applications are discussed. A non linear control system is proposed and two control schemes, a gain scheduling and a fuzzy logic based control system are presented.

   Maximum Power Transfer in Small Wind Energy Converter with Permanent Magnet Generator for Heating Purposes
By L. Latkovskis; K. Rashevits; L. Rutmanis; J. Stabulnieks [View]
[Download]

Abstract: A simple wind energy converter for power heating elements supply is proposed. The maximum power transfer is realized by dividing the load resistance into two parts and by proper matching the wind turbine and load circuit characteristics. An analytical approach to the system parameter calculation based on a linear system model analysis is described. Results of the PSPICE simulation are given as well.

   Power Electronic Interface for Wind Energy Conversion System Supplying Remote Installations in Antarctica
By F. Caricchi; V. Callea; F. Grescimbini; M. Falchetta; G. Lo Bianco; L. Solero [View]
[Download]

Abstract: Interest for exploitation of wind energy in Antarctica came up from the need of providing electricity supply, preserving the Antarctic environment and avoiding negative effects on pollution sensitive experiments, to a number of remote and unattended equipmùent which are required to operate on annual basis for data-acquisition purposes. Concerning to that this paper deals with design and testing of a 5 kW current regulated ac-dc power electronic interface prototype being developed for stand-alone wind-energy conversion system installed in extremely cold climates. Variable speed generator operatopn in the range from 125 rev/min to 260 rev/min is accomplished via the power electronic interface with diode bridge rectifier and IGBT-based dc-dc step-down converter, thus providing energy supply to a 110 V rated voltage lead-acid battery storage. The development of the original wind-energy conversion system is related to projects on scientific activities being carried out in several Antarctic sites. the wind turbine is acutally under test at the ENEA test field of Casaccia and will follow the next 1999-2000 Antarctic expedition.

   Rural South Africa and Photovoltaic Weak-Grid Interface Systems
By M.N. Mather; M. Malengret; J. Enslin [View]
[Download]

Abstract: Electrification of rural South Africa has traditionally been implemented using stand-alone renewable energy systems. These are often of a hybrid nature (with diesel generator) and can be integrated to form an isolated weak grid. Also, contemporary scenarios envision extension of the National utility using cheap distribution topologies. The role of PV interfacing within these contexts is identified, and a technical exploration of various topologies and control strategies is presented. Based on this, a design proposal is formulated.

   Static and Rotating Grid Formation for Modularly Expandable Island Grids
By J. Sachau; A. Engler [View]
[Download]

Abstract: Design and control of the grid forming battery pulse inverter in isolated modularly expandable threephase grids in the range of about 5 - 50 kW with renewable energy sources are presented with respect to a future expansion of the system with further generators. The integration of a flywheel coupled to a synchronous generator increases the range and stability of the system.

   Topology for Decentralised Solar Energy Inverters with a Low Voltage AC-Bus
By B. Lindgren [View]
[Download]

Abstract: The development of photovoltaic inverters has recently moved towards smaller units in order to increase modularity and energy yield in shaded areas. The drawbacks are higher cost, as well as lower efficiency in comparison with larger units. This paper compares eight decentralised configurations and one conventional, with respect to efficiency and cost. Reliability and personal safety are also considered. The pre-requisite is that standard PV-modules of 25-50 V, 110 W, are to be used and the energy is to be transformed to the national grid of 230 V, 50 Hz. The recommended configuration is a low voltage AC-bus, which can reduce costs while maintaining or improving efficiency and safety.

EPE 1999 - Topic 09a: Renewable Energy 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 09a: Renewable Energy Systems
	[return to parent folder]

	A Modular DC-DC Converter and Maximum Power Tracking Controller for medium to large scale Photovoltaic Generating Plant By J.A. Gow; J. A. M. Bleijs	[View] [Download]
Abstract: A suitable configuration for medium to large scale photovoltaic plant consists of a number of d.c.-d.c. converter modules feeding a common bus with a single high power inverter providing the utility interface. This paper proposes an efficient d.c.-d.c. converter system employing a new fast maximum power point tracker with an appropriately optimized converter topology.

	Analysis and Design of Inverters for Low Voltage Generators By J. Myrzik; A. Waldschmidt	[View] [Download]
Abstract: During the past few years the development of small inverters for photovoltaic technology has been supported by creating small, expandable energy supply systems. In order to reduce the high costs for solar technology nowadays, mainly the costs of the power conditioning have to be reduced. Therefore, the derivation of several transformerless inverter topologies will be presented here, which allow to connect a low generator voltage to the utility grid. Their conduction mode, DC- and AC-signal behaviour and modelling will be discussed. The theoretical results will be verified in a test circuit for stand alone systems.

	Current Source Inverter for a 400 kW Ocean Waves Induction Generator By C. Joao Ramos; P. Moreira da Silva; A. Carvalho	[View] [Download]
Abstract: Electrical energy generated from the ocean waves is a renewable energy being developed. One form of retrieving this energy is using the Oscillating Water Column (OWC) principle. In order to optimise this energetic resource, the electric generator must work at variable speed depending on the input power. For the energy to be delivered to mains, the voltage magnitude and frequency must be constant. This paper describes a system that uses a generator based on a wound induction machine with slip energy recovery, which allows operation with variable speed and direct connection to the mains. The Slip Energy Recovery System (SERS) is based on a wound induction machine being controlled through the amount of rotor energy delivered to the mains by means of a static converter. The AC variable rotor voltage is converted to DC voltage with a rectifier groupment and then converted again to AC in order to be injected into mains. The use of an IGBT Current Source Inverter (CSI) as DC-AC converter minimises current harmonics and allows smooth interaction between the random and variable input power and the mains. The main advantage of this system is the ability to generate 400 kW using a 200 kW machine and a 200 kW CSI. The prototype appears as an important development due to work with a large renewable energy source at a significant power level. The good performance carried out by the equipment based on an induction generator is reached through a well-controlled IGBT based current inverter that is presented within this paper.

	Flywheel Energy Storage System Using a Vector Controlled Induction Motor By R. Càrdenas; R. Peña; R. Blasco	[View] [Download]
Abstract: Even when variable speed wind turbines are used, electrical generation using wind energy conversion system generates electrical power which is not suitable for some application because of the ripple in the output of the generator. Also in wind diesel system, the wind velocity variations produce an unacceptable number of start/stop cycles of the diesel engine if an erergy buffer is not considered. In this paper the applications of the flywheel storage systems using vector controlled induction machines for wind energy applications are discussed. A non linear control system is proposed and two control schemes, a gain scheduling and a fuzzy logic based control system are presented.

	Maximum Power Transfer in Small Wind Energy Converter with Permanent Magnet Generator for Heating Purposes By L. Latkovskis; K. Rashevits; L. Rutmanis; J. Stabulnieks	[View] [Download]
Abstract: A simple wind energy converter for power heating elements supply is proposed. The maximum power transfer is realized by dividing the load resistance into two parts and by proper matching the wind turbine and load circuit characteristics. An analytical approach to the system parameter calculation based on a linear system model analysis is described. Results of the PSPICE simulation are given as well.

	Power Electronic Interface for Wind Energy Conversion System Supplying Remote Installations in Antarctica By F. Caricchi; V. Callea; F. Grescimbini; M. Falchetta; G. Lo Bianco; L. Solero	[View] [Download]
Abstract: Interest for exploitation of wind energy in Antarctica came up from the need of providing electricity supply, preserving the Antarctic environment and avoiding negative effects on pollution sensitive experiments, to a number of remote and unattended equipmùent which are required to operate on annual basis for data-acquisition purposes. Concerning to that this paper deals with design and testing of a 5 kW current regulated ac-dc power electronic interface prototype being developed for stand-alone wind-energy conversion system installed in extremely cold climates. Variable speed generator operatopn in the range from 125 rev/min to 260 rev/min is accomplished via the power electronic interface with diode bridge rectifier and IGBT-based dc-dc step-down converter, thus providing energy supply to a 110 V rated voltage lead-acid battery storage. The development of the original wind-energy conversion system is related to projects on scientific activities being carried out in several Antarctic sites. the wind turbine is acutally under test at the ENEA test field of Casaccia and will follow the next 1999-2000 Antarctic expedition.

	Rural South Africa and Photovoltaic Weak-Grid Interface Systems By M.N. Mather; M. Malengret; J. Enslin	[View] [Download]
Abstract: Electrification of rural South Africa has traditionally been implemented using stand-alone renewable energy systems. These are often of a hybrid nature (with diesel generator) and can be integrated to form an isolated weak grid. Also, contemporary scenarios envision extension of the National utility using cheap distribution topologies. The role of PV interfacing within these contexts is identified, and a technical exploration of various topologies and control strategies is presented. Based on this, a design proposal is formulated.

	Static and Rotating Grid Formation for Modularly Expandable Island Grids By J. Sachau; A. Engler	[View] [Download]
Abstract: Design and control of the grid forming battery pulse inverter in isolated modularly expandable threephase grids in the range of about 5 - 50 kW with renewable energy sources are presented with respect to a future expansion of the system with further generators. The integration of a flywheel coupled to a synchronous generator increases the range and stability of the system.

	Topology for Decentralised Solar Energy Inverters with a Low Voltage AC-Bus By B. Lindgren	[View] [Download]
Abstract: The development of photovoltaic inverters has recently moved towards smaller units in order to increase modularity and energy yield in shaded areas. The drawbacks are higher cost, as well as lower efficiency in comparison with larger units. This paper compares eight decentralised configurations and one conventional, with respect to efficiency and cost. Reliability and personal safety are also considered. The pre-requisite is that standard PV-modules of 25-50 V, 110 W, are to be used and the energy is to be transformed to the national grid of 230 V, 50 Hz. The recommended configuration is a low voltage AC-bus, which can reduce costs while maintaining or improving efficiency and safety.