PV String Converter Voltage Limits for Module Mismatch Control
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Solution Overview
Problem
Photovoltaic systems face inefficiencies due to fixed voltage limiting values in converters, which do not account for variations in open circuit voltages of individual modules, leading to suboptimal conversion efficiency and potential overvoltage issues.
Innovation Solution
A photovoltaic system with a controller that sets variable voltage limiting values for each converter based on the open circuit voltage of the connected module and the sum of open circuit voltages in the string, ensuring the converter operates at high efficiency while preventing overvoltage by using a proportional and inversely proportional approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed voltage limiting value is used for all converters, then the system configuration is simple, but the conversion efficiency is reduced and overvoltage protection cannot be ensured
Solution Approach 1:
The patent applies local quality by setting individual voltage limiting values for each converter based on its specific photovoltaic module's open circuit voltage characteristics. Instead of using a uniform voltage limit across all converters, each converter receives a customized limiting value that matches its connected module's properties, thereby optimizing conversion efficiency while maintaining simple system configuration.
2Loss of energy
If the voltage limiting value is increased to maximize conversion efficiency, then conversion efficiency is improved, but overvoltage protection is compromised
Solution Approach 1:
The patent changes the voltage limiting parameter dynamically by calculating individual limiting values based on the open circuit voltage of each photovoltaic module. The controller computes a voltage limiting value for each converter that is proportional to its connected module's open circuit voltage, ensuring that the limiting value adapts to the specific module characteristics while maintaining system safety through overvoltage protection.
3Loss of energy
If different voltage limiting values are set for each converter based on module characteristics, then conversion efficiency is maximized, but the control system complexity increases
Solution Approach 1:
The patent implements self-service by enabling each converter to autonomously determine its own voltage limiting value based on the open circuit voltage of its connected photovoltaic module. The controller provides the module's open circuit voltage parameter, and each converter independently calculates and applies its appropriate limiting value, reducing the need for complex centralized control while maximizing conversion efficiency.
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 solution enhances conversion efficiency by tailoring voltage limiting values to each module's characteristics, improving overall system performance and preventing overvoltage, thus maximizing energy output while ensuring safe operation.
Implementation Method 1
a direct current generated by a photovoltaic module e.g., based on exposure to solar radiation
Data Source
AI summary
A 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.