EPE Association: EPE 2014 - DS3e: Solar Energy Systems

EPE 2014 - DS3e: Solar Energy Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 05: Renewable Energy Power Systems > EPE 2014 - DS3e: Solar Energy Systems

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   A Global Maximum Power Point Tracking Method Based on Interval Short-circuit Current
By Xu DI, Ma YUNDONG, Wang JIE [View]
[Download]

Abstract: A photovoltaic (PV) array show multi local maximum power points mode under partially shaded conditions, where the operating point of the PV system tends to converge to a local maximum power point (LMPP) which is not the real maximum power point. A novel MPPT method is proposed in this paper to achieve global maximum power point tracking (GMPPT) under partially shaded conditions. The behavior of I-V characteristics is discussed and interval short-circuit current is applied to locate global maximum power point interval. A state-space based PV array model and simulation results are presented to validate the proposed method.

   A Study on Design and Optimization Procedure of High Frequency Transformer for Module-Integrated Converter
By JIN-HYUNG YOO, JUNE-WOO JO, TAE-UK JUNG [View]
[Download]

Abstract: The module-integrated converter (MIC) research is interested in the small-scale photo-voltaic (PV)generation. It is capable of efficient power generation by operating at maximum power point of eachPV module. In this system, the high frequency transformer should be compacted and has highefficiency characteristics to attach on the backside of PV module. However, the high frequencytransformer is tallest and biggest component in converter circuit. This paper presented the core andwinding structure optimization procedure to improve the efficiency of high frequency transformer incompact size. In order to obtain the accurate finite element analysis (FEA) result, the converter circuitis considered in the FEA model. The results are verified by testing the prototypes.

   Accelerated Photovoltaic Maximum Power Point Tracking for Partial Shading Conditions
By Liran KATZIR, Doron SHMILOVITZ [View]
[Download]

Abstract: A maximum power point control suitable for photovoltaic systems operating under uneven irradiance is proposed. Building on the observation that local maxima may occur only at specific string voltage, the searched range is reduced significantly. Thus the proposed controller is proven to identify and track the global maximum much faster than previously proposed ones. In addition the algorithm is simple, does not imply heavy computation and can be implemented in the simplest available micro-processors. Simulation results fully support the proposed approach.

   Design of Boost-Power-Stage Converter for PV Generator Interfacing
By Jyri KIVIMÄKI, Teuvo SUNTIO, Lauri HIETALAHTI [View]
[Download]

Abstract: This paper investigates the benefits which can be obtained if the maximum output current of a photovoltaic (PV) generator is taken into account in the design of a boost-power-stage converter. The investigations clearly show that the benefits are smaller inductor core size and more uniform temperature distribution among the power electronic components compared to the conventional design method. It will also be shown how to make the design with small input capacitor and how to take the power decoupling into account in the design process.

   Fuzzy controller for PV systems based on the fuzzy model reference
By ABDEL AITOUCHE [View]
[Download]

Abstract: This paper presents the control of a Photovoltaic (PV) using a fuzzy model approach. A fuzzy controller will be designed based on a Takagi-Sugeno (TS) fuzzy plant model of the PV. This proposed controller is capable of driving the system states of the PV to follow those of a stable reference fuzzy model with the stability of the closed-loop system guaranteed. The simulation results through Matlab/Simulink software demonstrate that the proposed fuzzy control system can guarantee the system stability and also maintain a good tracking performance.

   Optimizing the accuracy of electrical models of PV systems operating under non-ideal conditions
By Diego TORRES LOBERA, Seppo VALKEALAHTI [View]
[Download]

Abstract: Photovoltaic (PV) technology permits us to harness and transform solar radiation into electricity. However, PV power generators are still a marginal share in the global power generation capacity. One of the main reasons for it is that PV systems are greatly dependent on the atmospheric conditions affecting their operation. Furthermore, series connection of PV cells is prone to power losses when the electrical characteristics of the cells are dissimilar or the cells operate under non-uniform operating conditions. Accurate electrical models are required to analyze PV systems under non-ideal operating conditions, for example, to optimize the design of grid inverters. This paper proposes a method to optimize the accuracy of the electrical models based on a sensitivity analysis of the parameters of the model and on the evaluation of the normalized root mean square error between the measured and simulated P-V characteristics continuously by the second.

   Research on input current ripple reduction of two-stage single-phase PV grid inverter
By Jianguo LYU, Wenbin HU, Kai YAO, Xiaoyu LU, Fuyun WU, Junji WU [View]
[Download]

Abstract: Due to the instantaneous input and output power unbalance in two-stage of single-phase photovoltaic(PV) grid inverter, its front-end Boost converter tends to draw a current ripple with double grid frequency. In this paper, the low frequency current ripple reduction method is proposed, based on a duty ratio compensation model to control duty ratio of the boost converter without any extra cost. The duty ratio compensation model is built and derived, which is verified in SABER environment. The simulation proves that the duty ratio compensation method can effectively reduce and even eliminate the low frequency input current ripple in two-stage of single-phase PV grid inverter.

   Single-stage three-phase current-source inverter for photovoltaic grid-connected system
By Yuling LI, Pengfei LI, Yuzha CHEN, Dehua ZHANG, Guanjian WANG [View]
[Download]

Abstract: A single-stage three-phase current source inverter (CSI) using in photovoltaic grid-connected (PVGC) system is investigated. A dynamic predictive optimal control (DPOC) strategy for grid current is presented. In this method, based on a predictive model of grid current and real-time dynamic optimization cost function, an optimal control action for the next sampling interval is achieved in advance. In addition, a perturbing resistance maximum power point tracking (PR-MPPT) algorithm is proposed for the CSI PVGC system. The algorithm is implemented by perturbing resistance instead of perturbing current or voltage in conventional perturbation and observation (PO) MPPT method. The PR-MPPT algorithm can solve the issues of current instability and power dropping instantly at the right side of maximum power point (MPP) of P-I curves in CSI PVGC system. With the proposed methods, the CSI PVGC system achieves the features of simple circuit, good stability and fast dynamic response and MPPT function. Experimental results validate the feasibility of the proposed work.

   Time and frequency-domain evidence on power quality issues caused by grid-connected three-phase photovoltaic inverters
By Tuomas MESSO, Juha JOKIPII, Aapo AAPRO, Teuvo SUNTIO [View]
[Download]

Abstract: The amount of grid-connected inverters has been growing steadily over the past decade due to increasein renewable power generation. These inverters have been reported to degrade power quality in thegrid in areas where the amount renewable power generation is large. However, the reasons behind thepower quality issues are not yet extensively reported in the literature. The output impedance of singleand three-phase PV inverters has been reported to resemble a negative resistance over a frequency range which depends on the selected control scheme and control parameters. Negative resistance can cause impedance-based interactions which may lead to instability, especially, when the inverter is connected to a weak grid which has large inductance. The main contribution of this paper is the experimentalresults which clearly show that the inverter has a significant role on the reported power quality issues.The inverter is shown to generate harmonic, interharmonic or even subharmonic currents depending onthe processed power, component sizing, control parameters and the grid impedance. The paper alsodemonstrates that these phenomena can be accurately predicted by applying the well-known Nyquist stabilitycriterion.

EPE 2014 - DS3e: Solar Energy Systems
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2014 ECCE Europe - Conference > EPE 2014 - Topic 05: Renewable Energy Power Systems > EPE 2014 - DS3e: Solar Energy Systems
	[return to parent folder]

	A Global Maximum Power Point Tracking Method Based on Interval Short-circuit Current By Xu DI, Ma YUNDONG, Wang JIE	[View] [Download]
Abstract: A photovoltaic (PV) array show multi local maximum power points mode under partially shaded conditions, where the operating point of the PV system tends to converge to a local maximum power point (LMPP) which is not the real maximum power point. A novel MPPT method is proposed in this paper to achieve global maximum power point tracking (GMPPT) under partially shaded conditions. The behavior of I-V characteristics is discussed and interval short-circuit current is applied to locate global maximum power point interval. A state-space based PV array model and simulation results are presented to validate the proposed method.

	A Study on Design and Optimization Procedure of High Frequency Transformer for Module-Integrated Converter By JIN-HYUNG YOO, JUNE-WOO JO, TAE-UK JUNG	[View] [Download]
Abstract: The module-integrated converter (MIC) research is interested in the small-scale photo-voltaic (PV)generation. It is capable of efficient power generation by operating at maximum power point of eachPV module. In this system, the high frequency transformer should be compacted and has highefficiency characteristics to attach on the backside of PV module. However, the high frequencytransformer is tallest and biggest component in converter circuit. This paper presented the core andwinding structure optimization procedure to improve the efficiency of high frequency transformer incompact size. In order to obtain the accurate finite element analysis (FEA) result, the converter circuitis considered in the FEA model. The results are verified by testing the prototypes.

	Accelerated Photovoltaic Maximum Power Point Tracking for Partial Shading Conditions By Liran KATZIR, Doron SHMILOVITZ	[View] [Download]
Abstract: A maximum power point control suitable for photovoltaic systems operating under uneven irradiance is proposed. Building on the observation that local maxima may occur only at specific string voltage, the searched range is reduced significantly. Thus the proposed controller is proven to identify and track the global maximum much faster than previously proposed ones. In addition the algorithm is simple, does not imply heavy computation and can be implemented in the simplest available micro-processors. Simulation results fully support the proposed approach.

	Design of Boost-Power-Stage Converter for PV Generator Interfacing By Jyri KIVIMÄKI, Teuvo SUNTIO, Lauri HIETALAHTI	[View] [Download]
Abstract: This paper investigates the benefits which can be obtained if the maximum output current of a photovoltaic (PV) generator is taken into account in the design of a boost-power-stage converter. The investigations clearly show that the benefits are smaller inductor core size and more uniform temperature distribution among the power electronic components compared to the conventional design method. It will also be shown how to make the design with small input capacitor and how to take the power decoupling into account in the design process.

	Fuzzy controller for PV systems based on the fuzzy model reference By ABDEL AITOUCHE	[View] [Download]
Abstract: This paper presents the control of a Photovoltaic (PV) using a fuzzy model approach. A fuzzy controller will be designed based on a Takagi-Sugeno (TS) fuzzy plant model of the PV. This proposed controller is capable of driving the system states of the PV to follow those of a stable reference fuzzy model with the stability of the closed-loop system guaranteed. The simulation results through Matlab/Simulink software demonstrate that the proposed fuzzy control system can guarantee the system stability and also maintain a good tracking performance.

	Optimizing the accuracy of electrical models of PV systems operating under non-ideal conditions By Diego TORRES LOBERA, Seppo VALKEALAHTI	[View] [Download]
Abstract: Photovoltaic (PV) technology permits us to harness and transform solar radiation into electricity. However, PV power generators are still a marginal share in the global power generation capacity. One of the main reasons for it is that PV systems are greatly dependent on the atmospheric conditions affecting their operation. Furthermore, series connection of PV cells is prone to power losses when the electrical characteristics of the cells are dissimilar or the cells operate under non-uniform operating conditions. Accurate electrical models are required to analyze PV systems under non-ideal operating conditions, for example, to optimize the design of grid inverters. This paper proposes a method to optimize the accuracy of the electrical models based on a sensitivity analysis of the parameters of the model and on the evaluation of the normalized root mean square error between the measured and simulated P-V characteristics continuously by the second.

	Research on input current ripple reduction of two-stage single-phase PV grid inverter By Jianguo LYU, Wenbin HU, Kai YAO, Xiaoyu LU, Fuyun WU, Junji WU	[View] [Download]
Abstract: Due to the instantaneous input and output power unbalance in two-stage of single-phase photovoltaic(PV) grid inverter, its front-end Boost converter tends to draw a current ripple with double grid frequency. In this paper, the low frequency current ripple reduction method is proposed, based on a duty ratio compensation model to control duty ratio of the boost converter without any extra cost. The duty ratio compensation model is built and derived, which is verified in SABER environment. The simulation proves that the duty ratio compensation method can effectively reduce and even eliminate the low frequency input current ripple in two-stage of single-phase PV grid inverter.

	Single-stage three-phase current-source inverter for photovoltaic grid-connected system By Yuling LI, Pengfei LI, Yuzha CHEN, Dehua ZHANG, Guanjian WANG	[View] [Download]
Abstract: A single-stage three-phase current source inverter (CSI) using in photovoltaic grid-connected (PVGC) system is investigated. A dynamic predictive optimal control (DPOC) strategy for grid current is presented. In this method, based on a predictive model of grid current and real-time dynamic optimization cost function, an optimal control action for the next sampling interval is achieved in advance. In addition, a perturbing resistance maximum power point tracking (PR-MPPT) algorithm is proposed for the CSI PVGC system. The algorithm is implemented by perturbing resistance instead of perturbing current or voltage in conventional perturbation and observation (PO) MPPT method. The PR-MPPT algorithm can solve the issues of current instability and power dropping instantly at the right side of maximum power point (MPP) of P-I curves in CSI PVGC system. With the proposed methods, the CSI PVGC system achieves the features of simple circuit, good stability and fast dynamic response and MPPT function. Experimental results validate the feasibility of the proposed work.

	Time and frequency-domain evidence on power quality issues caused by grid-connected three-phase photovoltaic inverters By Tuomas MESSO, Juha JOKIPII, Aapo AAPRO, Teuvo SUNTIO	[View] [Download]
Abstract: The amount of grid-connected inverters has been growing steadily over the past decade due to increasein renewable power generation. These inverters have been reported to degrade power quality in thegrid in areas where the amount renewable power generation is large. However, the reasons behind thepower quality issues are not yet extensively reported in the literature. The output impedance of singleand three-phase PV inverters has been reported to resemble a negative resistance over a frequency range which depends on the selected control scheme and control parameters. Negative resistance can cause impedance-based interactions which may lead to instability, especially, when the inverter is connected to a weak grid which has large inductance. The main contribution of this paper is the experimentalresults which clearly show that the inverter has a significant role on the reported power quality issues.The inverter is shown to generate harmonic, interharmonic or even subharmonic currents depending onthe processed power, component sizing, control parameters and the grid impedance. The paper alsodemonstrates that these phenomena can be accurately predicted by applying the well-known Nyquist stabilitycriterion.