EPE Association: EPE 2009 - Topic 14-11 - DS (A): 'Photovoltaic Power Conversion'

EPE 2009 - Topic 14-11 - DS (A): 'Photovoltaic Power Conversion'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 14: 'Electrical Energy Generating Systems, Renewable Energy Systems' > EPE 2009 - Topic 14-11 - DS (A): 'Photovoltaic Power Conversion'

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   A Novel MPPT Algorithm for Dual-Inverter Grid-Connected PV Applications
By Gabriele GRANDI, Darko OSTOJIC, Claudio ROSSI [View]
[Download]

Abstract: A novel MPPT algorithm for three-phase grid-connected photovoltaic generation systems is presented in this paper. Reference is made to a conversion scheme consisting in two balanced arrays of PV modules, each one feeding a standard 2-level three-phase voltage source inverter (VSI). The dc-link voltages of each VSI are regulated according with the requirement of the proposed MPPT algorithm, based on the comparison of the operating points of the two PV arrays. Inverters are connected to grid by a three-phase transformer with open-end windings configuration on inverters side. The resulting conversion structure performs as a power active filter, doubling the power capability of a single VSI, with the additional benefit of multilevel voltage waveforms. The proposed MPPT algorithm has been successfully verified by experimental tests.

   An Innovative Perturb, Observe and Check Algorithm for Partially Shaded PV Systems
By Ricardo ALONSO, Eduardo ROMAN, Asier SANZ, Ekaitz OLAGUENAGA, Pedro IBAÃ‘EZ [View]
[Download]

Abstract: The performance of every photovoltaic (PV) module constituting a PV system can be slightly or strongly different from each other. This factual functioning of PV systems results in some new effects to bear in mind, including the appearance of new peak power points on the output P-V characteristic. However, traditional Maximum Power Point Tracking (MPPT) control methods do not manage these phenomena and can get lost easily. Even though many papers have been reported recently in relation to new MPPT control techniques, none of these solves satisfactorily the problem of local Maximum Power Points (MPPs). In fact, despite their complexity, the operating point is likely to converge on a local MPP under certain conditions reducing significantly the global efficiency of the PV system. In order to overcome this drawback, a new MPPT is proposed consisting of a traditional Perturb & Observe (PO) algorithm but improved with a second stage able to detect these anomalies on the PV generator curve. With this aim, the casuistry of the problem of local MPPs has been analyzed in depth. From the obtained conclusions a new checking stage has been developed and tested. The experimental results carried out have shown not only the capability to find the real MPP under any circumstance but also the facility to get it in a fast and reliable way.

   Application of normally-off SiC-JFETs in Photovoltaic Inverters
By Dirk KRANZER, Bruno BURGER [View]
[Download]

Abstract: In this paper the implementation and the performance of 1200 V / 30 A / 65 m normally-off SiC - JFETs in photovoltaic inverters (PV-inverters) is shown and compared with Si - IGBTs. The JFETsâ€™ low switching energy and on-resistance lead to an improvement of efficiency and a reduction of costs and weight of PV-inverters.

   Combined Mechanical and Electrical Control of Solar Trackers in (C)PV Power Plants
By Olivier STALTER, Bruno BURGER, Seddik BACHA, Daniel ROYE [View]
[Download]

Abstract: The major idea pointed out in this paper concerns the combination of a photovoltaic (PV) grid-feeding inverter with a motor control unit for two-axis solar trackers. The integration of a PV or concentrating PV (CPV) two-axis tracker position control unit, i.e. power electronics to supply the drives as well as sun tracking algorithms, into a specially designed grid-feeding inverter turns it into a â€œTracking Inverterâ€. This Tracking Inverter allows plenty of technical and financial advantages and represents a key component for large scale CPV or tracked PV power plants. Indeed, (C)PV power plants based on Tracking Inverters are not only easier to design and built up but also more flexible, more reliable and foremost much more cost effective than others.

   Control of a Three-Phase Grid-Connected Inverter for Photovoltaic Applications with a Fuzzy MPPT Under Unbalanced Conditions
By Jaime ALONSO-MARTINEZ, JoaquÃn ELOY-GARCÃA, Santiago ARNALTES [View]
[Download]

Abstract: Grid codes are being revised to include additional requirements for renewable energy, as the installed power increases. Therefore it is needed to develop control systems that are able to fulfil those new requirements, which usually include the ability to operate under unbalanced grid voltages without polluting the grid, among others. This paper presents a three-phase inverter for connection of photovoltaic generators to the grid, with a fuzzy maximum power point tracking and the ability to control reactive power. The main feature of the inverter is that the control system has been designed to deal with unbalanced voltage conditions.

   Design and Optimization of a Printed Circuit Board for a Photovoltaic and Thermal Linear Solar Concentrator
By Leonardo SERRI, Alberto REATTI, Mattia BELTRAMINI [View]
[Download]

Abstract: In this paper a Printed Circuit Board (PCB) utilized to enhance the overall performances of a photovoltaic (PV) and thermal concentrators is presented. A Printed Circuit Board has been studied for linear solar concentrators. The concentrator analyzed is based on a single axis tracking system. Because of this, the latter is affected by end losses and, therefore, main attention has been devoted to the design of linear concentrator collector in order to minimize these effects. Design and optimization details for the latter collector are given in the paper. The solutions derived to increase the electrical and thermal power production are also presented. The proposed PCB increases the electrical and thermal power production under critical operation of a linear concentrator such as shadowings and thermal exchanges. The design and optimization has been fulfilled through an electrical model and simulation of the concentration PV cell. The board presents a proper bypass diodes configuration and a "low-thermal resistance" that achieves the electrical and thermal production improvement respectively.

   European efficiency improvement in photovoltaic applications by means of parallel connection of power converters
By AloÃ±a BERASATEGI, cedric CABAL, Bruno ESTIBALS, Corinne ALONSO [View]
[Download]

Abstract: European efficiency definition demonstrates that photovoltaic generators operate in average between 30\% and 100\% of its rated power 80\% of its working time. Nowadays, converters are designed with a maximal efficiency working point, but often, this point does not fit with the correct power range. This paper presents a structure with a parallel connection of n converters to obtain higher conversion efficiency for the power range between 30\% and 100\% of the rated power. The European efficiency has been improved and higher energy production has been achieved with this new structure.

   Evaluation of DC-to-DC Converters Topologies with Quadratic Conversion Ratios for Photovoltaic Power Systems
By JEAN-PAUL GAUBERT [View]
[Download]

Abstract: This paper presents a new class of pulsewidth modulation (PWM) DC-to-DC converters with quadratic conversion ratios for photovoltaic applications without a transformer. The aim of these structures is to obtain at the same time high conversion ratio and excellent efficiency for a wide source voltage range. The DC voltage conversion ratios of these converters have a quadratic dependence on duty cycle providing thus a large step-up and offering the possibility of higher switching frequency. This research focuses on the development of these new structures with only one single active switch and their theoretical analysis with relevant equations and operating principle. Moreover, a complete simulation and experimental results are presented to confirm their interest in photovoltaic applications. These results are used to compare on the one hand the conversion ratios versus duty cycle and on the other hand the efficiency versus the conversion ratios of each topology.

   Field analysis of commercial PV inverters in the 5 kW power range with respect to MPPT effectively
By Vicente SALAS, Pedro. J. DEBORA, E. OLIAS [View]
[Download]

Abstract: The aim of this article is to describe how closely PV grid-connected inverters operate at the actual maximum power point. To carry this study out six 50 Hz single-phase inverters were selected from European market. Each one of them was put into an outdoor grid-connected system installed in LeganÃ©s (Madrid) Spain (by using flat and concentrating PV modules). Different electrical signals with respect to irradiance, PV module temperature and local time were measured. DC voltage and maximum power point tracking were analysed.

   NEW PARALLEL POWER PROCESSING STRATEGY FOR THE SEQUENTIAL SHUNT SWITCHING REGULATOR
By Jose M. BLANES, Ausias GARRIGOS, Jose A. CARRASCO, Esteban SANCHIS, Enrique MASET [View]
[Download]

Abstract: This paper presents the application of the parallel power processing strategy to the Sequential Switching Shunt Regulator for its use with high parasitic capacitance solar arrays. The main idea consists in dividing the complete solar array into two types of sections, low power sections and high power sections. The controller has been devised in such a way that always one low power section switches to regulate the bus, keeping the same first order closed-loop response that the traditional regulator. On the other hand, the turn-on delay has been mathematically modeled and the impact on the loop gain and the closed loop output impedance have been represented and analyzed. To reduce the impact of the delay, a lead-lag network is added in the control loop, achieving better performances in the AC characteristics.

   Passive and Active Methods of Islanding for PV systems
By Tomas SKOCIL, Oriol GOMIS-BELLMUNT, Daniel MONTESINOS-MIRACLE, Samuel GALCERAN-ARELLANO, Joan RULL-DURAN [View]
[Download]

Abstract: This paper presents a review of some techniques for islanding detection, especially by using inverter based DG applications and it also focuses on several islanding detection methods for a single-phase current-control voltage inverter working with a PV system connected into the grid. It is deliberated a single-phase inverter with maximum power of 5 kW. Islanding detection methods are investigated, simulated and evaluated in MATLAB / SIMULINK.

   PV-INVERTER WITH IMPROVED EFFICIENCY AND LIFETIME
By Kurt GÃ–PFRICH [View]
[Download]

Abstract: F3E (Fundamental Frequency Front End) is the denomination for a converter with active rectifier and negligibly small DC-link-capacitance. These converters are normally used to operate 3-phase-motors, especially in applications where power regeneration is required. The simplicity and high efficiency of F3E-converters makes them suitable also for renewable energy applications (wind, water etc.), or as F3E-inverters for renewable DC-sources (solar cells, fuel cells etc.).

   Stand-alone dc power plant supplied by an alternative energy integrated modular system
By Simone CASTELLAN, Alberto TESSAROLO, Marco DELLA VALENTINA, Giorgio VICIGUERRA [View]
[Download]

Abstract: In this paper a DC power plant for base transceiver station power supply is investigated. The supply system employs clean alternative energy sources, namely photovoltaic (PV) modules, wind turbines, a fuel cell as backup generator and a storage battery bank. A detailed description is made and experimental data are shown of a prototype system where the PV modules are directly connected to the DC bus and an on/off strategy is used to control the power flow to the battery bank and to the load. The system is modeled and the model is validated comparing simulation results with experimental data. It is then investigated the possibility to add a DC-DC converter for optimized control of the energy generated by the PV strings. Simulation results show that the addition of a DC-DC converter between the PV modules and the DC bus brings a remarkable increase in the produced energy.

   The Effect of Grid Operating Conditions on the Current Control Performance of Grid Connected Photovoltaic Inverters
By Hong Soo GOH, Matthew ARMSTRONG, Bashar ZAHAWI [View]
[Download]

Abstract: This paper investigates the interactions which arise between grid connected photovoltaic inverter systems and the electrical grid. In particular, it considers the effect of grid voltage harmonics and grid impedance on the current control performance of grid connected inverter systems. In these photovoltaic inverter systems it is usual to control unity power factor, sinusoidal, current into the grid with low levels of distortion. However, due to the time varying nature of the grid it can be difficult to design a system which will always meet power quality standards. To overcome this problem, a better understanding of the impact of the grid operating conditions on the performance of the inverter is required.

   The High Efficiency Transformer-less PV Inverter Topologies Derived From NPC Topology
By Lin MA, Tamas KEREKES, Remus TEODORESCU, Xinmin JIN, Dan FLORICAU, Marco LISERRE [View]
[Download]

Abstract: The grid-connected photovoltaic (PV) systems are an important part of renewable energy sources and their integration is getting more and more widespread. In order to improve the efficiency, practicality and reliability of the PV systems, many kinds of new inverter topologies have been proposed to avoid using a grid isolation transformer. The NPC topology and two other derived topologies are presented and analyzed in this paper. Validated by experiments, it has been proven that they are very suitable for using in transformer-less PV applications due to high efficiency, low leakage current and EMI. Simulations using Simulink and the PLECS toolbox have been done for evaluating efficiency of different NPC topologies and some experimental results are presented in this paper to validate the operation of the different topologies.

EPE 2009 - Topic 14-11 - DS (A): 'Photovoltaic Power Conversion'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 14: 'Electrical Energy Generating Systems, Renewable Energy Systems' > EPE 2009 - Topic 14-11 - DS (A): 'Photovoltaic Power Conversion'
	[return to parent folder]

	A Novel MPPT Algorithm for Dual-Inverter Grid-Connected PV Applications By Gabriele GRANDI, Darko OSTOJIC, Claudio ROSSI	[View] [Download]
Abstract: A novel MPPT algorithm for three-phase grid-connected photovoltaic generation systems is presented in this paper. Reference is made to a conversion scheme consisting in two balanced arrays of PV modules, each one feeding a standard 2-level three-phase voltage source inverter (VSI). The dc-link voltages of each VSI are regulated according with the requirement of the proposed MPPT algorithm, based on the comparison of the operating points of the two PV arrays. Inverters are connected to grid by a three-phase transformer with open-end windings configuration on inverters side. The resulting conversion structure performs as a power active filter, doubling the power capability of a single VSI, with the additional benefit of multilevel voltage waveforms. The proposed MPPT algorithm has been successfully verified by experimental tests.

	An Innovative Perturb, Observe and Check Algorithm for Partially Shaded PV Systems By Ricardo ALONSO, Eduardo ROMAN, Asier SANZ, Ekaitz OLAGUENAGA, Pedro IBAÃ‘EZ	[View] [Download]
Abstract: The performance of every photovoltaic (PV) module constituting a PV system can be slightly or strongly different from each other. This factual functioning of PV systems results in some new effects to bear in mind, including the appearance of new peak power points on the output P-V characteristic. However, traditional Maximum Power Point Tracking (MPPT) control methods do not manage these phenomena and can get lost easily. Even though many papers have been reported recently in relation to new MPPT control techniques, none of these solves satisfactorily the problem of local Maximum Power Points (MPPs). In fact, despite their complexity, the operating point is likely to converge on a local MPP under certain conditions reducing significantly the global efficiency of the PV system. In order to overcome this drawback, a new MPPT is proposed consisting of a traditional Perturb & Observe (PO) algorithm but improved with a second stage able to detect these anomalies on the PV generator curve. With this aim, the casuistry of the problem of local MPPs has been analyzed in depth. From the obtained conclusions a new checking stage has been developed and tested. The experimental results carried out have shown not only the capability to find the real MPP under any circumstance but also the facility to get it in a fast and reliable way.

	Application of normally-off SiC-JFETs in Photovoltaic Inverters By Dirk KRANZER, Bruno BURGER	[View] [Download]
Abstract: In this paper the implementation and the performance of 1200 V / 30 A / 65 m normally-off SiC - JFETs in photovoltaic inverters (PV-inverters) is shown and compared with Si - IGBTs. The JFETsâ€™ low switching energy and on-resistance lead to an improvement of efficiency and a reduction of costs and weight of PV-inverters.

	Combined Mechanical and Electrical Control of Solar Trackers in (C)PV Power Plants By Olivier STALTER, Bruno BURGER, Seddik BACHA, Daniel ROYE	[View] [Download]
Abstract: The major idea pointed out in this paper concerns the combination of a photovoltaic (PV) grid-feeding inverter with a motor control unit for two-axis solar trackers. The integration of a PV or concentrating PV (CPV) two-axis tracker position control unit, i.e. power electronics to supply the drives as well as sun tracking algorithms, into a specially designed grid-feeding inverter turns it into a â€œTracking Inverterâ€. This Tracking Inverter allows plenty of technical and financial advantages and represents a key component for large scale CPV or tracked PV power plants. Indeed, (C)PV power plants based on Tracking Inverters are not only easier to design and built up but also more flexible, more reliable and foremost much more cost effective than others.

	Control of a Three-Phase Grid-Connected Inverter for Photovoltaic Applications with a Fuzzy MPPT Under Unbalanced Conditions By Jaime ALONSO-MARTINEZ, JoaquÃn ELOY-GARCÃA, Santiago ARNALTES	[View] [Download]
Abstract: Grid codes are being revised to include additional requirements for renewable energy, as the installed power increases. Therefore it is needed to develop control systems that are able to fulfil those new requirements, which usually include the ability to operate under unbalanced grid voltages without polluting the grid, among others. This paper presents a three-phase inverter for connection of photovoltaic generators to the grid, with a fuzzy maximum power point tracking and the ability to control reactive power. The main feature of the inverter is that the control system has been designed to deal with unbalanced voltage conditions.

	Design and Optimization of a Printed Circuit Board for a Photovoltaic and Thermal Linear Solar Concentrator By Leonardo SERRI, Alberto REATTI, Mattia BELTRAMINI	[View] [Download]
Abstract: In this paper a Printed Circuit Board (PCB) utilized to enhance the overall performances of a photovoltaic (PV) and thermal concentrators is presented. A Printed Circuit Board has been studied for linear solar concentrators. The concentrator analyzed is based on a single axis tracking system. Because of this, the latter is affected by end losses and, therefore, main attention has been devoted to the design of linear concentrator collector in order to minimize these effects. Design and optimization details for the latter collector are given in the paper. The solutions derived to increase the electrical and thermal power production are also presented. The proposed PCB increases the electrical and thermal power production under critical operation of a linear concentrator such as shadowings and thermal exchanges. The design and optimization has been fulfilled through an electrical model and simulation of the concentration PV cell. The board presents a proper bypass diodes configuration and a "low-thermal resistance" that achieves the electrical and thermal production improvement respectively.

	European efficiency improvement in photovoltaic applications by means of parallel connection of power converters By AloÃ±a BERASATEGI, cedric CABAL, Bruno ESTIBALS, Corinne ALONSO	[View] [Download]
Abstract: European efficiency definition demonstrates that photovoltaic generators operate in average between 30\% and 100\% of its rated power 80\% of its working time. Nowadays, converters are designed with a maximal efficiency working point, but often, this point does not fit with the correct power range. This paper presents a structure with a parallel connection of n converters to obtain higher conversion efficiency for the power range between 30\% and 100\% of the rated power. The European efficiency has been improved and higher energy production has been achieved with this new structure.

	Evaluation of DC-to-DC Converters Topologies with Quadratic Conversion Ratios for Photovoltaic Power Systems By JEAN-PAUL GAUBERT	[View] [Download]
Abstract: This paper presents a new class of pulsewidth modulation (PWM) DC-to-DC converters with quadratic conversion ratios for photovoltaic applications without a transformer. The aim of these structures is to obtain at the same time high conversion ratio and excellent efficiency for a wide source voltage range. The DC voltage conversion ratios of these converters have a quadratic dependence on duty cycle providing thus a large step-up and offering the possibility of higher switching frequency. This research focuses on the development of these new structures with only one single active switch and their theoretical analysis with relevant equations and operating principle. Moreover, a complete simulation and experimental results are presented to confirm their interest in photovoltaic applications. These results are used to compare on the one hand the conversion ratios versus duty cycle and on the other hand the efficiency versus the conversion ratios of each topology.

	Field analysis of commercial PV inverters in the 5 kW power range with respect to MPPT effectively By Vicente SALAS, Pedro. J. DEBORA, E. OLIAS	[View] [Download]
Abstract: The aim of this article is to describe how closely PV grid-connected inverters operate at the actual maximum power point. To carry this study out six 50 Hz single-phase inverters were selected from European market. Each one of them was put into an outdoor grid-connected system installed in LeganÃ©s (Madrid) Spain (by using flat and concentrating PV modules). Different electrical signals with respect to irradiance, PV module temperature and local time were measured. DC voltage and maximum power point tracking were analysed.

	NEW PARALLEL POWER PROCESSING STRATEGY FOR THE SEQUENTIAL SHUNT SWITCHING REGULATOR By Jose M. BLANES, Ausias GARRIGOS, Jose A. CARRASCO, Esteban SANCHIS, Enrique MASET	[View] [Download]
Abstract: This paper presents the application of the parallel power processing strategy to the Sequential Switching Shunt Regulator for its use with high parasitic capacitance solar arrays. The main idea consists in dividing the complete solar array into two types of sections, low power sections and high power sections. The controller has been devised in such a way that always one low power section switches to regulate the bus, keeping the same first order closed-loop response that the traditional regulator. On the other hand, the turn-on delay has been mathematically modeled and the impact on the loop gain and the closed loop output impedance have been represented and analyzed. To reduce the impact of the delay, a lead-lag network is added in the control loop, achieving better performances in the AC characteristics.

	Passive and Active Methods of Islanding for PV systems By Tomas SKOCIL, Oriol GOMIS-BELLMUNT, Daniel MONTESINOS-MIRACLE, Samuel GALCERAN-ARELLANO, Joan RULL-DURAN	[View] [Download]
Abstract: This paper presents a review of some techniques for islanding detection, especially by using inverter based DG applications and it also focuses on several islanding detection methods for a single-phase current-control voltage inverter working with a PV system connected into the grid. It is deliberated a single-phase inverter with maximum power of 5 kW. Islanding detection methods are investigated, simulated and evaluated in MATLAB / SIMULINK.

	PV-INVERTER WITH IMPROVED EFFICIENCY AND LIFETIME By Kurt GÃ–PFRICH	[View] [Download]
Abstract: F3E (Fundamental Frequency Front End) is the denomination for a converter with active rectifier and negligibly small DC-link-capacitance. These converters are normally used to operate 3-phase-motors, especially in applications where power regeneration is required. The simplicity and high efficiency of F3E-converters makes them suitable also for renewable energy applications (wind, water etc.), or as F3E-inverters for renewable DC-sources (solar cells, fuel cells etc.).

	Stand-alone dc power plant supplied by an alternative energy integrated modular system By Simone CASTELLAN, Alberto TESSAROLO, Marco DELLA VALENTINA, Giorgio VICIGUERRA	[View] [Download]
Abstract: In this paper a DC power plant for base transceiver station power supply is investigated. The supply system employs clean alternative energy sources, namely photovoltaic (PV) modules, wind turbines, a fuel cell as backup generator and a storage battery bank. A detailed description is made and experimental data are shown of a prototype system where the PV modules are directly connected to the DC bus and an on/off strategy is used to control the power flow to the battery bank and to the load. The system is modeled and the model is validated comparing simulation results with experimental data. It is then investigated the possibility to add a DC-DC converter for optimized control of the energy generated by the PV strings. Simulation results show that the addition of a DC-DC converter between the PV modules and the DC bus brings a remarkable increase in the produced energy.

	The Effect of Grid Operating Conditions on the Current Control Performance of Grid Connected Photovoltaic Inverters By Hong Soo GOH, Matthew ARMSTRONG, Bashar ZAHAWI	[View] [Download]
Abstract: This paper investigates the interactions which arise between grid connected photovoltaic inverter systems and the electrical grid. In particular, it considers the effect of grid voltage harmonics and grid impedance on the current control performance of grid connected inverter systems. In these photovoltaic inverter systems it is usual to control unity power factor, sinusoidal, current into the grid with low levels of distortion. However, due to the time varying nature of the grid it can be difficult to design a system which will always meet power quality standards. To overcome this problem, a better understanding of the impact of the grid operating conditions on the performance of the inverter is required.

	The High Efficiency Transformer-less PV Inverter Topologies Derived From NPC Topology By Lin MA, Tamas KEREKES, Remus TEODORESCU, Xinmin JIN, Dan FLORICAU, Marco LISERRE	[View] [Download]
Abstract: The grid-connected photovoltaic (PV) systems are an important part of renewable energy sources and their integration is getting more and more widespread. In order to improve the efficiency, practicality and reliability of the PV systems, many kinds of new inverter topologies have been proposed to avoid using a grid isolation transformer. The NPC topology and two other derived topologies are presented and analyzed in this paper. Validated by experiments, it has been proven that they are very suitable for using in transformer-less PV applications due to high efficiency, low leakage current and EMI. Simulations using Simulink and the PLECS toolbox have been done for evaluating efficiency of different NPC topologies and some experimental results are presented in this paper to validate the operation of the different topologies.