Power Electronics and Control Research Group A STAND A STAND - - ALONE PHOTOVOLTAIC SYSTEM ALONE PHOTOVOLTAIC SYSTEM BASED ON DC BASED ON DC - - DC CONVERTERS IN A MULTI DC CONVERTERS IN A MULTI - - STRING CONFIGURATION STRING CONFIGURATION J. Imhoff, G. F. Rodrigues, A. R. Bülow, R. Gules, J. R. Pinheiro and H. L. Hey
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Power Electronics andControl Research Group
A STANDA STAND--ALONE PHOTOVOLTAIC SYSTEM ALONE PHOTOVOLTAIC SYSTEM BASED ON DCBASED ON DC--DC CONVERTERS IN A MULTIDC CONVERTERS IN A MULTI--
STRING CONFIGURATIONSTRING CONFIGURATION
J. Imhoff, G. F. Rodrigues, A. R. Bülow, R. Gules, J. R. Pinheiro and H. L. Hey
Power Electronics andControl Research Group
OutlineOutline
• Introduction;Motivation;
• Photovoltaic Systems (PV systems);Centralized Photovoltaic Systems;Decentralized Photovoltaic Systems;
• MPPT Technique Choice;• Simulation Results;• Summary;• Next Steps.
Power Electronics andControl Research Group
IntroductionIntroduction: : MotivationMotivation
• 12 million Brazilians remain without electricity (~80% in rural areas);
• Brazil is among the countries that present the highest incidence solar energy.
Source: ANEEL - Atlas de Energia Elétrica do Brasil
• 100% natural, free and inexhaustible;• Locally generated energy;• Modular, silent and reliable.
•• Irregular energy supplied;• Low efficiency;• Expensive technology.
BenefitsBenefits:
DrawbacksDrawbacks::
Power Electronics andControl Research Group
IntroductionIntroduction: : MotivationMotivation
• Shortage of fossil fuels;• Crescent reduction in the costs of PV Systems;• Increase in the acceptance of PV Systems.
Source: Development of the PV industry in Europe," Sustainable Energy 2005 (EPIA)Source: Department of Energy/ US
Power Electronics andControl Research Group
Photovoltaic SystemsPhotovoltaic Systems
•• PV systems can be classified as:PV systems can be classified as:Grid-connected systems;Stand-alone systems;
Centralized Based Concept Topology;Decentralized Based Concept Topology.
Power Electronics andControl Research Group
Centralized Photovoltaic SystemCentralized Photovoltaic System
Centralized MPPT;Low utilization of the generated
energy;Battery bank is placed in the power
path;Reduced life cycle of the batteries.
Features:
Single array of PV panels (series and/or parallel connection);Single DC-DC converter to realize the MPPT.
• The most widely spread stand-alone PV system.
Power Electronics andControl Research Group
Proposed SystemProposed System
As an alternative to centralized configuration,As an alternative to centralized configuration,a standa stand--alone photovoltaic systemalone photovoltaic system
with distributed energy processing is proposedwith distributed energy processing is proposed..
Power Electronics andControl Research Group
Decentralized Photovoltaic SystemDecentralized Photovoltaic System
Features:
Division of the PV array in strings;Each string has its own non-isolated DC-DC boost converter to
perform the MPPT;DC-DC boost converters are connected in series;Integrated buck and boost converters, with bi-directional power flow
control, dedicated to the battery bank.
Power Electronics andControl Research Group
Decentralized Photovoltaic SystemDecentralized Photovoltaic System
Features:Individualized MPPT;Modularity;PV strings can be installed at different orientations;Smaller individual converter power ratings;The battery bank is out of main power path;Longer life cycle of the batteries.
Power Electronics andControl Research Group
MPPT Technique ChoiceMPPT Technique Choice
•• Constant Voltage (CV);Constant Voltage (CV);•• Perturbation and Observation (PO);Perturbation and Observation (PO);•• Incremental Conductance (Incremental Conductance (IncCondIncCond).).
• It is presented the simulation results for the input stage of both: the centralized stand-alone PV system and the proposed decentralized stand-alone PV system for the following conditions:
1) For both system the panels are under the same radiation;
2) Some of the PV panels are submitted to a decreased radiation, characterizing shading/failure/aging of such panels.