EPE Association: EPE 2011 - DS2k: Topic 15: Non-Rotating Power Generation and Storage Systems I

EPE 2011 - DS2k: Topic 15: Non-Rotating Power Generation and Storage Systems I
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2011 ECCE Europe - Conference > EPE 2011 - Topic 15: Non-rotating power generation and storage systems > EPE 2011 - DS2k: Topic 15: Non-Rotating Power Generation and Storage Systems I

   [return to parent folder]

   A High efficiency resonant solar micro-inverter
By Johan ENSLIN, Bruce MODICK, Madhu JOSHI, Titi TRANDAFIR, Ron DECKER, Ehab SHOUBAKI, Kathryn VOHDEN [View]
[Download]

Abstract: No abstract provided.

   A Novel Design Methodology Maximizing the Weighted-Efficiency of Flyback Inverter for AC Photovoltaic Modules
By Anastasios NANAKOS, Emmanuel TATAKIS, Georgios DIMITRAKAKIS, Nikolaos PAPANIKOLAOU, Anastasios KYRITSIS [View]
[Download]

Abstract: A new design methodology that optimizes the weighted efficiency of a single-phase, single-stage flyback inverter for AC-PV module applications is proposed. This novel approach combines the essential advantages of the flyback topology with high efficiency in the direction of a reliable, cost-effective and high performance photovoltaic system. The proposed methodology focuses exclusively on choosing the inverter’s design parameters, taking into consideration the PV module’s characteristics. In order to meet this goal an analytical losses calculation should be performed. Since the problem is complicated special effort is given to manipulate the equations and variables in such a way to minimize the number of parameter taking into consideration the operation constraints. The proposed methodology is also verified experimentally.

   An all-in-one power electronic solution for the introduction of PV and storage for smart grids
By Jan CAPPELLE, Stijn VISPOEL , Thomas VAN MAERHEM [View]
[Download]

Abstract: Due to a growing green consciousness and the royal Belgian subsidy policy towards photovoltaic solarpower, PV-installations are showing up all over the country. The distribution grid, once designed to deliver electric power, has to deal with a problem of overvoltage during high irradiation levels. This paper presents the first results of a research project that was funded by the Flemish government to investigate the influence of renewables on the power quality and vice versa. The first aim of the project was to come up with practical solutions for the overvoltage in distribution grids. The presented solution is the introduction of a limited battery pack at residentual PV production sites to buffer energy at overvoltage. Today’s household PV-inverters switch off at overvoltage resulting in the loss of green energy. The discussed all-in-one inverter avoids these losses. Firstly, a model of the distribution grid is given to quantify this green energy loss on a typical Belgian distribution feeder. Simulations on this model show that the local installation of a buffer size of only one third of the average daily PV yield of the PV-installation can already eliminate the overvoltage along the feeder. Secondly, a possible power electronic solution for limiting the active power injection by buffering is presented. This all-in-one power electronic solution offers battery charging, grid coupling possibilities as well as single phase solar energy inverting with MPP tracking from a single inverter platform. The platform is real-time controlled from Matlab/Simulink via a target PC. The paper concludes with a control algorithm for this all-in-one inverter.

   Ascertainment of Static Characteristic Fluctuation of Photovoltaic Cells and Evaluation of High-Speed Maximum Power Point Tracking Control
By Shioto TANAKA, Toshiya YOSHIDA, Katsumi OHNIWA, Osamu MIYASHITA [View]
[Download]

Abstract: In this paper, tracking speed of maximum power point tracking (MPPT) control of photovoltaic (PV) generation systems is investigated. To observe quick changes of the static characteristics of PV, a high-speed measurement system is developed. Ability of MPPT control is evaluated with voltage-current chart recorded by the proposed system at speed of about 100 charts per second. By the discussions, speedup of MPPT control is effective when especially the PV system is mounted on automobiles running on streets.

   Bidirectional Converter Interface for a Battery Energy Storage Test Bench
By Ionut TRINTIS, Stephan THOMAS, Tobias BLANK, Christoph ROGGENDORF, Stig MUNK-NIELSEN, Remus TEODORESCU [View]
[Download]

Abstract: This paper presents the bidirectional converter interface for a 6 kV battery energy storage test bench. The power electronic interface consists a two stage converter topology having a low voltage dc-ac grid connected converter and a new dual active bridge dc-dc converter with high transformation ratio. The dc-dc converter controls the battery charge/discharge current while the grid converter controls the common dc-link voltage and the grid current. The applied control structures and the hardware implementation of both converters are presented, together with their interaction. Experimental results of the test bench show good performance for the bidirectional power flow with a maximum operating power of 100 kW.

   DC-AC inverter based on a Cycloconverter Output Stage with Active Filter for peak power reduction in transformer and switches
By Nicholas SHATTOCK, Christian KLUMPNER, Greg ASHER [View]
[Download]

Abstract: Converters used for interfacing a DC to AC medium voltage grid, constructed from a Voltage Source Inverter (VSI) connected to a Cycloconverter output stage, via a high frequency transformer (DC/AC), have several advantages when compared to a DC-DC converter combined with an Voltage Source inverter (DC/DC/AC) as the output stage, but also some major shortcomings. This paper focuses on some of these shortcomings, the installed power in the high frequency transformer and associated switches, as the transformer in the DC/AC converter processes twice the peak power of the transformer in the DC/DC/AC converter. It is proposed that by adding an additional 3 phase Voltage Source Inverter (VSI) active filter, connected to a flying capacitor, to each of the single phase DC/AC inverters the peak power required from the transformer and switches can be reduced.

   Design and Implementation of 50kW Multi-String Photovoltaic PCS Using three-phase interleaved DC-DC converters
By Hanju CHA, Woojong LEE, Tae-Pung AN [View]
[Download]

Abstract: In this paper, a 50kW multi-string photovoltaic power conditioning system (PV PCS) and control schemes are proposed and analyzed. The PV PCS consists of five 10kW three-phase interleaved dc-dc converters and a 50kW centralized inverter with LCL-filter, whose controllers are connected through CAN communication for synchronization and ripple current reduction. Prototype of multi-string PV PCS is implemented and tested for the proposed several control schemes.

   Design Considerations for Core Material Selection and Operating Modes for a High Frequency Transformer Used in an Isolated DC/DC Converter
By Omar ABU HASSAN, Christian KLUMPNER, Greg ASHER [View]
[Download]

Abstract: Magnetic core materials are considered critical components that influence an isolated DC/DC converter’s dynamic response, efficiency and size. This paper illustrates the impact of core material choice in the design of a high frequency transformer for an isolated DC/DC converter for energy storage applications. The variation of the performance for different types of core material as well as the inter relationship between parameters (flux density, frequency, efficiency and size) is investigated. It is shown that, by summing up the loss surfaces of systems that (use different core materials) will result in a recommended core material map which can guide the designer towards the smallest losses that can be achieved in a given frequency and flux density range, which the designer can assign to their application. In addition, it will be investigated the variation of power loss with the loading factor, which is an important aspect in energy storage system since most systems will operate at reduced loading compared to the peak power capability, where the systems is designed from thermal point of view. In order to maximize transformer efficiency, adjustable voltage and current is considered and an analytical model to derive optimum operating point at a given frequency is derived. Exploration of finding the best operating point when frequency is also allowed to vary is also considered.

   Dielectric Elastomers as Generators
By Balazs CZECH, Rick VAN KESSEL, Pavol BAUER, Jon Abraham FERREIRA [View]
[Download]

Abstract: Dielectric elastomers used as generators have received considerable attention lately andseveral prototypes were built to demonstrate the process. The aim of the paper is to show how aninnovative energy harvesting cycle can be realized to use the DEs as an efficient generator. Itinvestigates the effects of (dis)charging instants, the current amplitude and how the parasitics of thematerial influences the energy gain and show what kind of trade-offs can be reached by selectingparameters carefully. Also an EAP emulator is introduced: it is able to implement a variable capacitorby a controllable power supply. It can be used for evaluating PTOs, tests, measurements; without thecomplexity, vulnerability and high price of the elastomer.

   Dual-mode current-fed semi-quadratic buck-boost converter for transformerless modular photovoltaic applications
By Lari NOUSIAINEN, Teuvo SUNTIO [View]
[Download]

Abstract: The urge to utilize green energy supplies increases the number of grid-connected photovoltaic (PV) energy systems. Transformerless inverter technology is a key for efficient and low cost solutions. In order to achieve the high DC link voltage required by the transformerless single-stage inverter, numerous photovoltaic modules has to be connected in series. In a long string, the mismatch losses of the modules and propability of partial shading increases especially in the built environment. In case of the partial shading, the maximum power point (MPP) may exist at the voltage levels unreachable for the inverter causing high losses in the energy yield. To reduce the aforementioned problems, modular solutions have been proposed. In modular applications, each module is interfaced to a voltage bus by a power electronics based converter to increase the MPP tracking efficiency. Implementing PV energy systems, where solar cells are connected to a voltage bus, which has lower or higher voltage than the voltage of the PV generator, such as the power grid in modular applications, requires the use of a buck-boost-type converter. The semi-quadratic conversion ratio of the proposed converter enables its usage in transformerless modular applications. The converter may be equipped with a low-frequency unfolding full-bridge inverter to implement a modular single-phase inverter. Input voltage control and the quadratic step-down conversion ratio of the converter provide efficient power decoupling for the fluctuating power of the single-phase grid. The converter can be controlled with a single or dual PWM signals as desired. The paper concentrates on the steady-state properties of the converter. Feasibility of the converter is proven by experimental measurements.

   Generator Emulation Controls for Photovoltaic Inverters
By Hussam ALATRASH, Johan ENSLIN [View]
[Download]

Abstract: State-of-the-art inverter controls for grid-tied photovoltaic (PV) systems pose a number of challenges to grid stability if deployed on a large scale. This paper addresses large-scale integration of PV and other distributed generation (DG) into the grid. A new control scheme for grid-tied DG inverters is proposed to embed various load-following functions. This control scheme, dubbed Generator Emulation Controls (GEC), allows DG inverters to perform voltage regulation support, reactive power compensation, and fault ride-through. GEC also allows DG inverters to form scalable inverter-dominated micro-grids. These micro-grids are capable of operating in grid-tied mode or of separating and supporting an islanded load. Dynamic modeling of synchronous generators is presented, and used to guide GEC implementation. Experimental results are presented to demonstrate some of the main features of GEC.

   Genetic algorithms for maximum power point tracking in photovoltaic systems
By Jean-Paul GAUBERT [View]
[Download]

Abstract: This paper presents a novel genetic algorithm to carry out the maximum power point tracking based on the photovoltaic cell model. For that it is necessary to measure the open circuit voltage (Voc) and short circuit current (Isc), then the proposed algorithm gives directly and rapidly the optimal voltage (Vop) so the converter duty cycle can be adjusted. The simulation results are obtained by changing Isc and Voc values. The proposed technique permits to verify the linearity between Vop and Voc and between optimal current (Iop) and Isc. We also give a comparison with the conventional Perturb and Observe (P&O) and Incremental Conductance (IncCond) algorithms.

   Multilevel High Voltage Converter driving Dielectric Elastomer Generators
By Christian GRAF, Juergen MAAS [View]
[Download]

Abstract: Electro Active Polymers are highly suitable as generators to convert mechanical strain energy into electrical energy, because of the high energy density. To harvest energy, the polymer is stretched by an external force to increase the capacitance of the variable capacitor. After applying charges at the maximum stretch until a predetermined allowable field strength is reached, the external force is reduced and the polymer relaxes. During relaxation a considerable amount of the strain energy is converted into electric field energy and at the end of relaxation the charges can be harvested at a higher voltage compared to the initial voltage level. For the electrical control, a special high voltage power-electronics is necessary driving the generators at high voltages and typically low currents. This is realized with a multilevel converter topology, which provides the required bidirectional energy flow and a high efficiency. A model of the converter is derived and a high dynamic voltage controller with underlying current controller is designed. Finally measurement results are presented, demonstrating the converters' ability to drive dielectric elastomer generators for energy harvesting.

   Optimal Structure Selection for Small-Size Hybrid Renewable Energy Plants
By Antonio TESTA, Salvatore DE CARO, Tommaso SCIMONE [View]
[Download]

Abstract: Hybrid Wind/Photovoltaic plants are often complemented with suitable energy storage devices to improve flexibility in grid connected applications and the continuity of supply in island mode service. The design of generation plants including energy storage devices is a quite complex task, moreover, no tools are today available to systematically compare the features of different possible architectures on the basis of given wind speed, solar irradiation and load diagrams. A probabilistic design approach is then proposed in this paper to select the most suitable internal structure of permanently grid connected, or island mode operating plants. The paper is mainly focused on low power Hybrid Wind/Photovoltaic plants for distributed generation, however, the proposed procedure may also be adapted to high power systems.

   Soft Switching Interleaved Active Clamp Flyback Inverter for a Photovoltaic AC Module System
By Young-Ho KIM, Jun-Gu KIM, Chung Yuen WON, Yongchae JUNG, Tae-Won LEE [View]
[Download]

Abstract: A soft switching interleaved active clamp flyback inverter for a photovoltaic AC module system isproposed. The proposed system includes an interleaved active clamp flyback converter and anunfolding bridge inverter. The interleaved active clamp flyback converter has the advantages of zerovoltage switching (ZVS) performance for the primary switches, reverse-recovery problem alleviationfor the secondary output diodes and small input current ripple. Furthermore, each switch in the flybackconverter operates with a high efficiency point along with an output power using a new optimalcontrol method. Therefore, high efficiency and high power density conversion can be achieved in awith input voltage range by employing the proposed system. In order to verify these, theoreticalanalysis and simulation are performed.

   TECHNIQUES FOR THE OPTIMAL DESIGN OF PHOTOVOLTAIC INVERTERS INTERCONNECTED WITH THE ELECTRIC GRID
By Eftichios KOUTROULIS, Frede BLAABJERG [View]
[Download]

Abstract: The DC/AC inverters are the key elements of grid-connected PV energy production systems. In this paper, a new technique for the optimal design of the power section and output filter of a full-bridge, grid-connected PV inverter, is proposed. The objective function which is minimized during the Genetic Algorithm-based optimization procedure is the PV inverter Levelized Cost Of the Electricity generated (LCOE). The proposed method has been applied for the optimal design of PV inverters installed at various sites in Europe. The simulation results indicate that the optimal values of the PV inverter design variables depend on the PV inverter specifications, the technical and economic characteristics of the components used to build the PV inverter and the meteorological conditions prevailing at the installation area.

   The Design And Application Of Flow Cell Systems.
By Eric LEWIS [View]
[Download]

Abstract: A Vanadium Redox Battery® energy storage system has been developed with a standard energy storage module rated at 200 kW rms with a peak power of 300 kW and a normal storage time of two hours. However the storage time can be increased to significantly longer times, at a viable cost, by adding extra storage fluid in a larger tank. The associated power converter system is presented together with data on the need for electrical energy storage.

   Voltage-Hold Perturbation & Observation Maximum Power Point Tracking Algorithm for Improved Tracking over the Transient Atmospheric Changes
By Imadeddin ABDALLA [View]
[Download]

Abstract: The paper proposes an algorithm for tracking the maximum power point of a PV source which isbased on the voltage-hold perturbation and observation tracking of the maximum power point duringatmospheric changes. The algorithm overcomes the major tracking limitations and produces improvedresults compared with the standard MPPT algorithms which were reviewed briefly as a background.The proposed algorithm has been implemented practically by using eZdsp™ F28335 to control theDC/DC buck-converter under different irradiances.

   Wind/PV/Diesel Energy System: Modeling and Sizing Optimization
By Lu ZHANG, Rachid BELFKIRA, Georges BARAKAT [View]
[Download]

Abstract: This paper focuses on the development of a methodology for calculation of the sizing and optimizationof a stand-alone hybrid system. This approach makes use of a deterministic algorithm to suggest,among a list of commercially available system devices, the optimal number and type of units ensuringthat the total costs of the autonomous hybrid systems are minimized while guaranteeing theavailability of the energy demand of the customers and safety of the system. The hybrid systems arestudied with the collection of hourly data of solar radiation, wind speed and ambient temperature tothe site of Le Havre, France, for a period of one year. Finally, the obtained sizing optimization of thestudied hybrid systems is exposed and discussed by showing the simulation of the hybrid systemsoperation for a short period of time.

EPE 2011 - DS2k: Topic 15: Non-Rotating Power Generation and Storage Systems I
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2011 ECCE Europe - Conference > EPE 2011 - Topic 15: Non-rotating power generation and storage systems > EPE 2011 - DS2k: Topic 15: Non-Rotating Power Generation and Storage Systems I
	[return to parent folder]

	A High efficiency resonant solar micro-inverter By Johan ENSLIN, Bruce MODICK, Madhu JOSHI, Titi TRANDAFIR, Ron DECKER, Ehab SHOUBAKI, Kathryn VOHDEN	[View] [Download]
Abstract: No abstract provided.

	A Novel Design Methodology Maximizing the Weighted-Efficiency of Flyback Inverter for AC Photovoltaic Modules By Anastasios NANAKOS, Emmanuel TATAKIS, Georgios DIMITRAKAKIS, Nikolaos PAPANIKOLAOU, Anastasios KYRITSIS	[View] [Download]
Abstract: A new design methodology that optimizes the weighted efficiency of a single-phase, single-stage flyback inverter for AC-PV module applications is proposed. This novel approach combines the essential advantages of the flyback topology with high efficiency in the direction of a reliable, cost-effective and high performance photovoltaic system. The proposed methodology focuses exclusively on choosing the inverter’s design parameters, taking into consideration the PV module’s characteristics. In order to meet this goal an analytical losses calculation should be performed. Since the problem is complicated special effort is given to manipulate the equations and variables in such a way to minimize the number of parameter taking into consideration the operation constraints. The proposed methodology is also verified experimentally.

	An all-in-one power electronic solution for the introduction of PV and storage for smart grids By Jan CAPPELLE, Stijn VISPOEL , Thomas VAN MAERHEM	[View] [Download]
Abstract: Due to a growing green consciousness and the royal Belgian subsidy policy towards photovoltaic solarpower, PV-installations are showing up all over the country. The distribution grid, once designed to deliver electric power, has to deal with a problem of overvoltage during high irradiation levels. This paper presents the first results of a research project that was funded by the Flemish government to investigate the influence of renewables on the power quality and vice versa. The first aim of the project was to come up with practical solutions for the overvoltage in distribution grids. The presented solution is the introduction of a limited battery pack at residentual PV production sites to buffer energy at overvoltage. Today’s household PV-inverters switch off at overvoltage resulting in the loss of green energy. The discussed all-in-one inverter avoids these losses. Firstly, a model of the distribution grid is given to quantify this green energy loss on a typical Belgian distribution feeder. Simulations on this model show that the local installation of a buffer size of only one third of the average daily PV yield of the PV-installation can already eliminate the overvoltage along the feeder. Secondly, a possible power electronic solution for limiting the active power injection by buffering is presented. This all-in-one power electronic solution offers battery charging, grid coupling possibilities as well as single phase solar energy inverting with MPP tracking from a single inverter platform. The platform is real-time controlled from Matlab/Simulink via a target PC. The paper concludes with a control algorithm for this all-in-one inverter.

	Ascertainment of Static Characteristic Fluctuation of Photovoltaic Cells and Evaluation of High-Speed Maximum Power Point Tracking Control By Shioto TANAKA, Toshiya YOSHIDA, Katsumi OHNIWA, Osamu MIYASHITA	[View] [Download]
Abstract: In this paper, tracking speed of maximum power point tracking (MPPT) control of photovoltaic (PV) generation systems is investigated. To observe quick changes of the static characteristics of PV, a high-speed measurement system is developed. Ability of MPPT control is evaluated with voltage-current chart recorded by the proposed system at speed of about 100 charts per second. By the discussions, speedup of MPPT control is effective when especially the PV system is mounted on automobiles running on streets.

	Bidirectional Converter Interface for a Battery Energy Storage Test Bench By Ionut TRINTIS, Stephan THOMAS, Tobias BLANK, Christoph ROGGENDORF, Stig MUNK-NIELSEN, Remus TEODORESCU	[View] [Download]
Abstract: This paper presents the bidirectional converter interface for a 6 kV battery energy storage test bench. The power electronic interface consists a two stage converter topology having a low voltage dc-ac grid connected converter and a new dual active bridge dc-dc converter with high transformation ratio. The dc-dc converter controls the battery charge/discharge current while the grid converter controls the common dc-link voltage and the grid current. The applied control structures and the hardware implementation of both converters are presented, together with their interaction. Experimental results of the test bench show good performance for the bidirectional power flow with a maximum operating power of 100 kW.

	DC-AC inverter based on a Cycloconverter Output Stage with Active Filter for peak power reduction in transformer and switches By Nicholas SHATTOCK, Christian KLUMPNER, Greg ASHER	[View] [Download]
Abstract: Converters used for interfacing a DC to AC medium voltage grid, constructed from a Voltage Source Inverter (VSI) connected to a Cycloconverter output stage, via a high frequency transformer (DC/AC), have several advantages when compared to a DC-DC converter combined with an Voltage Source inverter (DC/DC/AC) as the output stage, but also some major shortcomings. This paper focuses on some of these shortcomings, the installed power in the high frequency transformer and associated switches, as the transformer in the DC/AC converter processes twice the peak power of the transformer in the DC/DC/AC converter. It is proposed that by adding an additional 3 phase Voltage Source Inverter (VSI) active filter, connected to a flying capacitor, to each of the single phase DC/AC inverters the peak power required from the transformer and switches can be reduced.

	Design and Implementation of 50kW Multi-String Photovoltaic PCS Using three-phase interleaved DC-DC converters By Hanju CHA, Woojong LEE, Tae-Pung AN	[View] [Download]
Abstract: In this paper, a 50kW multi-string photovoltaic power conditioning system (PV PCS) and control schemes are proposed and analyzed. The PV PCS consists of five 10kW three-phase interleaved dc-dc converters and a 50kW centralized inverter with LCL-filter, whose controllers are connected through CAN communication for synchronization and ripple current reduction. Prototype of multi-string PV PCS is implemented and tested for the proposed several control schemes.

	Design Considerations for Core Material Selection and Operating Modes for a High Frequency Transformer Used in an Isolated DC/DC Converter By Omar ABU HASSAN, Christian KLUMPNER, Greg ASHER	[View] [Download]
Abstract: Magnetic core materials are considered critical components that influence an isolated DC/DC converter’s dynamic response, efficiency and size. This paper illustrates the impact of core material choice in the design of a high frequency transformer for an isolated DC/DC converter for energy storage applications. The variation of the performance for different types of core material as well as the inter relationship between parameters (flux density, frequency, efficiency and size) is investigated. It is shown that, by summing up the loss surfaces of systems that (use different core materials) will result in a recommended core material map which can guide the designer towards the smallest losses that can be achieved in a given frequency and flux density range, which the designer can assign to their application. In addition, it will be investigated the variation of power loss with the loading factor, which is an important aspect in energy storage system since most systems will operate at reduced loading compared to the peak power capability, where the systems is designed from thermal point of view. In order to maximize transformer efficiency, adjustable voltage and current is considered and an analytical model to derive optimum operating point at a given frequency is derived. Exploration of finding the best operating point when frequency is also allowed to vary is also considered.

	Dielectric Elastomers as Generators By Balazs CZECH, Rick VAN KESSEL, Pavol BAUER, Jon Abraham FERREIRA	[View] [Download]
Abstract: Dielectric elastomers used as generators have received considerable attention lately andseveral prototypes were built to demonstrate the process. The aim of the paper is to show how aninnovative energy harvesting cycle can be realized to use the DEs as an efficient generator. Itinvestigates the effects of (dis)charging instants, the current amplitude and how the parasitics of thematerial influences the energy gain and show what kind of trade-offs can be reached by selectingparameters carefully. Also an EAP emulator is introduced: it is able to implement a variable capacitorby a controllable power supply. It can be used for evaluating PTOs, tests, measurements; without thecomplexity, vulnerability and high price of the elastomer.

	Dual-mode current-fed semi-quadratic buck-boost converter for transformerless modular photovoltaic applications By Lari NOUSIAINEN, Teuvo SUNTIO	[View] [Download]
Abstract: The urge to utilize green energy supplies increases the number of grid-connected photovoltaic (PV) energy systems. Transformerless inverter technology is a key for efficient and low cost solutions. In order to achieve the high DC link voltage required by the transformerless single-stage inverter, numerous photovoltaic modules has to be connected in series. In a long string, the mismatch losses of the modules and propability of partial shading increases especially in the built environment. In case of the partial shading, the maximum power point (MPP) may exist at the voltage levels unreachable for the inverter causing high losses in the energy yield. To reduce the aforementioned problems, modular solutions have been proposed. In modular applications, each module is interfaced to a voltage bus by a power electronics based converter to increase the MPP tracking efficiency. Implementing PV energy systems, where solar cells are connected to a voltage bus, which has lower or higher voltage than the voltage of the PV generator, such as the power grid in modular applications, requires the use of a buck-boost-type converter. The semi-quadratic conversion ratio of the proposed converter enables its usage in transformerless modular applications. The converter may be equipped with a low-frequency unfolding full-bridge inverter to implement a modular single-phase inverter. Input voltage control and the quadratic step-down conversion ratio of the converter provide efficient power decoupling for the fluctuating power of the single-phase grid. The converter can be controlled with a single or dual PWM signals as desired. The paper concentrates on the steady-state properties of the converter. Feasibility of the converter is proven by experimental measurements.

	Generator Emulation Controls for Photovoltaic Inverters By Hussam ALATRASH, Johan ENSLIN	[View] [Download]
Abstract: State-of-the-art inverter controls for grid-tied photovoltaic (PV) systems pose a number of challenges to grid stability if deployed on a large scale. This paper addresses large-scale integration of PV and other distributed generation (DG) into the grid. A new control scheme for grid-tied DG inverters is proposed to embed various load-following functions. This control scheme, dubbed Generator Emulation Controls (GEC), allows DG inverters to perform voltage regulation support, reactive power compensation, and fault ride-through. GEC also allows DG inverters to form scalable inverter-dominated micro-grids. These micro-grids are capable of operating in grid-tied mode or of separating and supporting an islanded load. Dynamic modeling of synchronous generators is presented, and used to guide GEC implementation. Experimental results are presented to demonstrate some of the main features of GEC.

	Genetic algorithms for maximum power point tracking in photovoltaic systems By Jean-Paul GAUBERT	[View] [Download]
Abstract: This paper presents a novel genetic algorithm to carry out the maximum power point tracking based on the photovoltaic cell model. For that it is necessary to measure the open circuit voltage (Voc) and short circuit current (Isc), then the proposed algorithm gives directly and rapidly the optimal voltage (Vop) so the converter duty cycle can be adjusted. The simulation results are obtained by changing Isc and Voc values. The proposed technique permits to verify the linearity between Vop and Voc and between optimal current (Iop) and Isc. We also give a comparison with the conventional Perturb and Observe (P&O) and Incremental Conductance (IncCond) algorithms.

	Multilevel High Voltage Converter driving Dielectric Elastomer Generators By Christian GRAF, Juergen MAAS	[View] [Download]
Abstract: Electro Active Polymers are highly suitable as generators to convert mechanical strain energy into electrical energy, because of the high energy density. To harvest energy, the polymer is stretched by an external force to increase the capacitance of the variable capacitor. After applying charges at the maximum stretch until a predetermined allowable field strength is reached, the external force is reduced and the polymer relaxes. During relaxation a considerable amount of the strain energy is converted into electric field energy and at the end of relaxation the charges can be harvested at a higher voltage compared to the initial voltage level. For the electrical control, a special high voltage power-electronics is necessary driving the generators at high voltages and typically low currents. This is realized with a multilevel converter topology, which provides the required bidirectional energy flow and a high efficiency. A model of the converter is derived and a high dynamic voltage controller with underlying current controller is designed. Finally measurement results are presented, demonstrating the converters' ability to drive dielectric elastomer generators for energy harvesting.

	Optimal Structure Selection for Small-Size Hybrid Renewable Energy Plants By Antonio TESTA, Salvatore DE CARO, Tommaso SCIMONE	[View] [Download]
Abstract: Hybrid Wind/Photovoltaic plants are often complemented with suitable energy storage devices to improve flexibility in grid connected applications and the continuity of supply in island mode service. The design of generation plants including energy storage devices is a quite complex task, moreover, no tools are today available to systematically compare the features of different possible architectures on the basis of given wind speed, solar irradiation and load diagrams. A probabilistic design approach is then proposed in this paper to select the most suitable internal structure of permanently grid connected, or island mode operating plants. The paper is mainly focused on low power Hybrid Wind/Photovoltaic plants for distributed generation, however, the proposed procedure may also be adapted to high power systems.

	Soft Switching Interleaved Active Clamp Flyback Inverter for a Photovoltaic AC Module System By Young-Ho KIM, Jun-Gu KIM, Chung Yuen WON, Yongchae JUNG, Tae-Won LEE	[View] [Download]
Abstract: A soft switching interleaved active clamp flyback inverter for a photovoltaic AC module system isproposed. The proposed system includes an interleaved active clamp flyback converter and anunfolding bridge inverter. The interleaved active clamp flyback converter has the advantages of zerovoltage switching (ZVS) performance for the primary switches, reverse-recovery problem alleviationfor the secondary output diodes and small input current ripple. Furthermore, each switch in the flybackconverter operates with a high efficiency point along with an output power using a new optimalcontrol method. Therefore, high efficiency and high power density conversion can be achieved in awith input voltage range by employing the proposed system. In order to verify these, theoreticalanalysis and simulation are performed.

	TECHNIQUES FOR THE OPTIMAL DESIGN OF PHOTOVOLTAIC INVERTERS INTERCONNECTED WITH THE ELECTRIC GRID By Eftichios KOUTROULIS, Frede BLAABJERG	[View] [Download]
Abstract: The DC/AC inverters are the key elements of grid-connected PV energy production systems. In this paper, a new technique for the optimal design of the power section and output filter of a full-bridge, grid-connected PV inverter, is proposed. The objective function which is minimized during the Genetic Algorithm-based optimization procedure is the PV inverter Levelized Cost Of the Electricity generated (LCOE). The proposed method has been applied for the optimal design of PV inverters installed at various sites in Europe. The simulation results indicate that the optimal values of the PV inverter design variables depend on the PV inverter specifications, the technical and economic characteristics of the components used to build the PV inverter and the meteorological conditions prevailing at the installation area.

	The Design And Application Of Flow Cell Systems. By Eric LEWIS	[View] [Download]
Abstract: A Vanadium Redox Battery® energy storage system has been developed with a standard energy storage module rated at 200 kW rms with a peak power of 300 kW and a normal storage time of two hours. However the storage time can be increased to significantly longer times, at a viable cost, by adding extra storage fluid in a larger tank. The associated power converter system is presented together with data on the need for electrical energy storage.

	Voltage-Hold Perturbation & Observation Maximum Power Point Tracking Algorithm for Improved Tracking over the Transient Atmospheric Changes By Imadeddin ABDALLA	[View] [Download]
Abstract: The paper proposes an algorithm for tracking the maximum power point of a PV source which isbased on the voltage-hold perturbation and observation tracking of the maximum power point duringatmospheric changes. The algorithm overcomes the major tracking limitations and produces improvedresults compared with the standard MPPT algorithms which were reviewed briefly as a background.The proposed algorithm has been implemented practically by using eZdsp™ F28335 to control theDC/DC buck-converter under different irradiances.

	Wind/PV/Diesel Energy System: Modeling and Sizing Optimization By Lu ZHANG, Rachid BELFKIRA, Georges BARAKAT	[View] [Download]
Abstract: This paper focuses on the development of a methodology for calculation of the sizing and optimizationof a stand-alone hybrid system. This approach makes use of a deterministic algorithm to suggest,among a list of commercially available system devices, the optimal number and type of units ensuringthat the total costs of the autonomous hybrid systems are minimized while guaranteeing theavailability of the energy demand of the customers and safety of the system. The hybrid systems arestudied with the collection of hourly data of solar radiation, wind speed and ambient temperature tothe site of Le Havre, France, for a period of one year. Finally, the obtained sizing optimization of thestudied hybrid systems is exposed and discussed by showing the simulation of the hybrid systemsoperation for a short period of time.