PV Converter Voltage Limiting for Mixed-Module String Efficiency
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Solution Overview
Problem
In photovoltaic power generation systems, the conversion efficiency of converters is reduced due to fixed voltage limiting values, which do not account for variations in open circuit voltages of individual photovoltaic modules, leading to suboptimal performance when modules with different models or quantities are connected in series and parallel.
Innovation Solution
A photovoltaic system with a controller that sets voltage limiting values for each converter proportionally to the open circuit voltage of the connected module and inversely proportional to the sum of open circuit voltages of the photovoltaic string, ensuring high conversion efficiency while preventing overvoltage at the inverter input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed voltage limiting value is configured for converters, then the inverter input voltage can be controlled within allowable range, but conversion efficiency of the converter reduces
Solution Approach 1:
The patent implements dynamic voltage limiting by making the voltage limiting value proportional to the open circuit voltage of the photovoltaic module. This allows the converter's voltage limiting threshold to adapt automatically to different module characteristics rather than using a fixed value, thereby maintaining high conversion efficiency while preventing inverter overvoltage
Solution Approach 2:
The patent changes the voltage limiting parameter from a fixed value to a proportional relationship with the photovoltaic module's open circuit voltage. By adjusting the voltage limiting value based on module parameters (Voc), the system optimizes converter operating conditions and maximizes conversion efficiency while ensuring inverter protection
2Loss of energy
If voltage limiting value is increased to maximize converter efficiency, then conversion efficiency improves, but inverter overvoltage protection is compromised
Solution Approach 1:
The system uses feedback from the photovoltaic module's open circuit voltage measurement to dynamically adjust the converter's voltage limiting value. This feedback mechanism ensures that the voltage limiting threshold is always appropriately set relative to the actual module characteristics, maximizing efficiency while maintaining inverter protection
Solution Approach 2:
The patent implements parameter-based adaptive control where the voltage limiting value changes proportionally with the photovoltaic module's open circuit voltage. This dynamic parameter adjustment allows the system to optimize converter efficiency for each specific module while inherently preventing inverter overvoltage through the proportional relationship
3Adaptability or versatility
If photovoltaic modules with different models are connected in series, then system flexibility and adaptability improve, but parameter discreteness causes mismatch and reduces performance
Solution Approach 1:
The patent segments the photovoltaic system into independent converter-module units, where each converter independently manages its connected photovoltaic module. This segmentation allows different models of photovoltaic modules to be connected in series without causing mismatch issues, as each converter adapts to its specific module's characteristics through the proportional voltage limiting control
Solution Approach 2:
The patent applies local quality control by making each converter's voltage limiting value specific to its connected photovoltaic module's open circuit voltage. This localized adaptation allows modules with different models and characteristics to be combined in the same system, with each converter optimizing its operation for its specific module, thereby maintaining high system productivity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for flexible configuration of photovoltaic modules, maximizing conversion efficiency by adjusting voltage limiting values based on individual module parameters and string sums, thereby improving overall system performance and preventing inverter derating due to overtemperature.
Implementation Method 1
a direct current generated by a photovoltaic module is converted into an alternating current by using an inverter
Data Source
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AI summary
This application discloses a photovoltaic system and a control method. The photovoltaic system includes an inverter, a controller, and at least two converters. An input terminal of each of the at least two converters are connected to a corresponding photovoltaic module, and output terminals of the at least two converters are connected in series and connected to an input terminal of the inverter. The controller is configured to set a voltage limiting value of at least one of the at least two converters, so that an output voltage of the at least one converter is less than or equal to the voltage limiting value when the converter works in a voltage limiting mode. The voltage limiting value of the at least one converter is proportional to an open circuit voltage of the photovoltaic module connected to an input terminal of the converter. Open circuit voltages of different photovoltaic modules vary with different parameters or models of the photovoltaic modules. Consequently, voltage limiting values of converters connected to the photovoltaic modules are different. In this way, for the voltage limiting value configured for each converter, the open circuit voltage of the photovoltaic module connected to the converter is fully considered, so that the converter works at high conversion efficiency.